# MH-C9000 Termination Issues [ A "hot" discussion :P ]



## EngrPaul (Dec 28, 2006)

I just received my MH-C9000 charger from TD yesterday. 

I decided to refresh/analyze all my batteries, lowest capacities first. The first batteries I used are 4 AAA 850 mA*h Energizer cells, which I have been using in pairs with my wireless mouse on my laptop for a couple years.

Following instructions, I programmed each bay to refresh/analyze... charge at 800 mA and discharge at 200 mA. Since these cells were already charged, the charging went quickly, and terminated properly.

Then Each bay discharged and reached their rest position. Here are the final capacities:

"A" 682 mA*h - "B" 718 mA*h - "C" 722 mA*h - "D" 792 mA*h 

I had labeled them after determining their capacities, that's why they are in order of capacity results.

I decided I didn't want to charge at 1.0C, so I pulled each cell an let them rest for an hour. So they were at a state of discharge around 1 Volt at this point.

Before going to bed last night, I inserted each cell and programmed it for 600 charge (0.7C), 200 discharge (0.2C). I put the batteries in order of being labeled. Each bay started charging at 600, so I went to bed. The charger propped up on it's lift bar sat in a room that was at 65F, with no artificial circulation.

This morning I awoke to find two cells near the end of discharging (A and C), two cells still charging (B and D). It's the two bays still charging that worries me! 

These two batteries that are still charging are over 4C now. 

EDIT: _I checked the overcharged cell temperatures with an IR thermometer: 127F. Now being over 4000 mA*h, I pulled them from the charger to reduce the damage to my cells._

I have the feeling the charger is the problem, not me or the batteries. I hope somebody can chime in here and help me understand what's going on.


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## moldyoldy (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi EngrPaul,

I had the exact same problem but with only the "B" bay. The situation was roughly the same using Refresh/Analyze and Powerex 2700mah AA cells. I also pulled the cells several times and reprogrammed the slots trying to make up my mind, but still in the "Refresh" mode . The other 3 slots terminated correctly. Slot B did not and the voltage sat on 1.51volts until I pulled it anyway after about 4AH being loaded into the cell. 

In the course of pulling the cells trying to make up my mind, I noticed that some readings were being retained from my previous aborted cycle. irritating, but plausible since the charger only scans the channels on some periodicity leaving the previous settings in place between scans. If you pull and reinsert a cell using the same mode setting, the new insertion may not reset the internal values for the last recorded voltage, etc. even though you actively change the charge current. To solve my problem, I had to cycle the power and all was well.

My recommendation, if you are going to abort a cycle, especially any sort of a longer refresh cycle, you have to cycle the power - pull the plug and reinsert. That is the only way the old voltage readings are erased assuming that you use the same mode setting (Refresh/Analyze, Cycle, Break-in, etc). If you change the mode settings, the previous cell voltage values may be erased if the cycle does not include an immediate charge. The problem seems to lie with the last recorded cell voltage or voltages - I don't know how many readings are stored to determine a -dV/dT.

BTW, That cell in slot B that had 4AH loaded into it also tested out with a higher capacity than the other cells that terminated correctly. I recall that WillC. indicated that Maha chose a "safe" cutoff level for the 801D/808/800S for longer cell life as compared to the 204W where the charger clearly overcharges the cells to ensure max capacity at the expense of somewhat shorter cell life.

Another BTW, after some intense use, I am beginning to understand some of the better uses of the C9000 charger. Some of the cycles are simply too long to wait for when I have many other tests I want to run. For example, I am quite satisfied with the "Discharge" cycle which gives me the existing capacity in any cell w/o any charging before or after. That was something I was missing from my BC-900. I often want to know what the remaining capacity in a cell is after storage or after an unknown amount of use. Saves inserting those cells in my LED lights and timing the lights runtime until discharge. I use one of my other chargers to actually charge the cells. eg: a comparison of charged capacity of four cells after fast and slow charges - 2A compared to .5A charge rate.

Tim


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## moldyoldy (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

a follow-on recollection. Other CPF members have reported problems when they pulled cells for a voltage check and re-inserted cells, especially at the end of the charge cycle. This sort of out-smarts the smart chargers since they rely on some sequence of voltage readings to determine and end of charge indication. Cycling power is the only way I know of resetting those voltage readings. 

I recall now that I had the same problem on my BC-900, maha 801D and AccuPower 20. The problem? no charge termination. At the time I blamed the newness of the cells. Now I realize that I contributed to the problem by tinkering with the cells somewhere close to end of the charge cycle.

Tim


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Thanks for your suggestions. 

Powering on/off could be a work-around, but it is certainly not the way the product is described to work.

I used the charge current directly in the middle of their 0.33C - 1.0C recommended charge range. 

I had the batteries off the charger for an hour, the charger should have forgot those old values.

This charger is sold to be able to detect dV/dt accurately and also to monitor the cell temperature dT/dt for proper termination.

Evidently these are not working, and the charger needs to back up it's regimen with a timer or some sort of limit to charge (150% max, for instance)

I'm really unhappy with this failure. I don't trust the charger. I can't stay home and babysit the charger all the time. 

What sort of protection do I have against having a melted ball of plastic on my tabletop when I come home?

I bought the charger to take better care of my batteries, not destroy them.


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## moldyoldy (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Thanks for your suggestions.
> 
> I had the batteries off the charger for an hour, the charger should have forgot those old values.




If the power to the charger was not cycled, there is no particular design reason why the charger would have erased the last voltage settings. This is perhaps a design question - should the charger erase the series of voltage settings each time a cell is removed? how long does the cell need to be missing to erase the settings? 

Again FWIW, other CPF members have reported charge termination problems when they started swapping in/out/in cells towards the end of a charge on other chargers.

In any case, Will C. should comment on the circumstances of this issue.

Of greater concern for me is the potential loss of AC power during a cycle and I'm not home. AC power loss does happen more than we like to admit. Smart chargers can be really confused by that. Yes, a design with flash memory can hold settings thru a power outage, but that adds $$$!

Tim


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

_"The capacity information will be stored as long as the battery is inserted in the charger. It will be lost upon removal of the battery."_

I'm not sure why other values would be stored internally. If the capacity information is gone, why not all the other incremental data?

If the power goes off, I would hope the charger comes back on and does NOTHING. We all know how haywire electronics get when powered on and off unexpectedly. I would not want the charger to try to pick up where it left off if there is a possiblitiy of data being corrupted.

Now, I did read in the FAQ:

_"*I am charging some older batteries and see that the charging capacity is much higher than the capacity I programmed. Why doesn’t the charger terminate correctly? *_

_The charger terminates by voltage and by temperature simultaneously. For certain older (and low quality) batteries, they do not produce the proper negative delta V signal (a small voltage drop at the conclusion of the charge) needed for the charger to stop. At the same time, the battery temperature failed to reach the termination limit as the charging rate was probably too low._

_To address this issue, you should attempt to perform a BREAK-IN mode on the batteries first. You should also use a higher charging rate."_

I didn't really think this applies to me. The name-brand batteries are really not that old, have been constantly exercised at a low current, and are a reasonable capacity to current standards.

Even so, I will perform a full discharge, break-in operation, then charge at 800mA, and report back tomorrow with my results.


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## BVH (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Small UPS's are not that costly. For those who will use the charger while at work or otherwise unattended, maybe the purchase and use of a small UPS would add a little margin of safety. I have a rather large UPS for my PC and after having read your posts, I think I will use one of its circuits for this charger. Thanks for the info in these posts!


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## willchueh (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Okay let me address the questions here:

1. MH-C9000 will not retain any memory of the previous cycle as long as the charger detects the battery is removed. The longest time required for this detection is TWO SECONDS (one measurement cycle). You can be assured that the battery removal is successful when the subsquent insertion prompts for the MODE. 

Now, the charger may DISPLAY some data from the previous cycle but only for the first few seconds of the new cycle. moldyoldy, this is probably what you saw. But it if you let it sit for a few seconds, the new data will kick in. 

The old data is not used at all in the new cycle and definitely not for the termination conditions. 

A power reset is not necessary. 


2. EngrPaul, regarding your overcharging experience, I am fairly confident that the cells did not produce the end-of-charge conditions necessary for the cells to stop. The main mechanism is Negative Delta V at about 5mV, followed by maximum temperature at 54 deg C, temperature change, then timer. Of course, the timer protection is very long due to the high capacity the unit supports (except for BREAK-IN mode which prompts for battery capacity - the charger recalculates timer based on this). 

The problem is the cell didn't get hot enough and borderlines the temperature limit.

If you look at the capacity of the battery (slot B), it is at 84% of the rated capacity, indicating that it is towards the end of its useful life. This would explain for the weak negative delta V signal. 

I can assure you, if the temperature of the cell is exceeded, the charger will stop. It poses little safety risk to the user. 

You won't be seeing any melted cell.


3. It is really not necessary to operate the MH-C9000 with an UPS.


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## moldyoldy (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Thanks for the responses Will C.!!

Aha! An important answer: the sensing cycle of the charger is two seconds for one cycle. That is needed to understand some other artifacts with what I see in the display.

regarding the data numbers that I see after insertion of the next cell to be tested - yes, they could be left over from a previous run. However some of the numbers are relatively impossible, such as 2.035 V for a NiMH cell, although this could be the unloaded charging voltage. Nevertheless, all of the data readings returned to something plausible after a sensing cycle or two. You answered that question!

The key to yet another answer is that the charger has to sense the withdrawal of the battery, and that is determined by the charger querying for "Mode" upon reinsertion of a cell. I seem to recall a couple times that I did not see the "Mode" at reinsertion, but I also seem to recollect that I may not have waited two seconds. I was getting somewhat irritated with _my_ indecision at that point .....  In any case, EngPaul's hour wait was enough.

as for my AA cell not providing a sufficient end-of-charge indication at a charge rate of 1500ma. um, well, the AA cell that failed the detection in the C9000 was a Maha Powerex 2700mah AA cell with about 5 cycles on it. The equivalent charge rate of 1500ma was about 1/2C. That cell successfully terminated charges previously on both an 801D and on an 800S. However, a test with a sample of one is a degrees of freedom of zero, so that single event probably did not prove much.  Yes, even Maha could have marginal cells in a lot....  and no, I don't know which one it is anymore since I re-bundled that AA cell with the other 3 from the charger. All came from a recent purchase of 32 Powerex AA cells from T-D. Thoughts? or simply a chance event?

The last piece of info that you provided is the 5mv level for charge determination of -dV/dT. Is this determined between the last two readings, or is there some averaging going on? 

I recall from another post someone made some time ago that the Maha 801D could sense at a 1mv reading resolution. true? If so, this is presumably also true for the 800s and the 808 which use a similar design. So, what is the sensing resolution of the C9000? Of course a 1mv reading resolution is not necessarily the actual negative voltage cutoff determination which should be higher voltage value - of necessity!

Thanks for your responses! very important to know this. Of course, if some of my questions are bordering on company proprietary info, don't answer! I understand.

Tim


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Will,

Thank you for your replies.

(1) I would like to know how I can prevent damage to my cells, from hours of overcharge to my batteries. If I am regularly using batteries, they are working fine for me, how would I know they are not "good enough" for this charger?

(2) My other Maha chargers have no problem sensing the end of cycle with these batteries. I thought the MH-C9000 was a better product?

(3) Why can't this charger have a default refresh & analyze regimen, where all I have to do is enter the battery capacity? This way I don't have to calculate my charge and discharge currents, and the charger will stop at 130% capacity, instead of delivering a significant (possibly destructive) overcharge?


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## willchueh (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tim,

The Negative Delta V "trigger condition" is 5mV but the resolution is 1mV (actually slightly better than that). There is a lot of signal conditioning (averaging, moving windows, etc) to the voltage. So no, it is not determined between the last two readings (forgive me for not going to greater details). 


William


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Okay let me address the questions here:
> ...
> 2. EngrPaul, regarding your overcharging experience, I am fairly confident that the cells did not produce the end-of-charge conditions necessary for the cells to stop. The main mechanism is Negative Delta V at about 5mV, followed by maximum temperature at 54 deg C, temperature change, then timer. Of course, the timer protection is very long due to the high capacity the unit supports (except for BREAK-IN mode which prompts for battery capacity - the charger recalculates timer based on this).
> 
> ...


It may not pose a safety risk to the user but it definitely can ruin the cell.

A cell with 84% of rated capacity should still have plenty of useful life left considering that it's probably at least 90% of its actual initial capacity. I have NEVER had an NiMH cell fail to terminate on my BC-900 (-dV/dt) or Lenmar Mach 1 (-dV/dt, dT/dt) and I've charged plenty of cells that were in FAR worse condition. Something is defintely wrong with his charger.



> 3. It is really not necessary to operate the MH-C9000 with an UPS.


It may not be necessary but it seems advisable. IMHO, the charger should not start charging if it's powered up with cells inserted. The C-9000 is not the only charger with this flaw but it doesn't make it right. If a brief power interruption occurs late in a charge cycle or shortly after its completetion, the end of charge indications can be missed and cells ruined. A simple firmware change would prevent this.

Mike


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> It may not pose a safety risk to the user but it definitely can ruin the cell.
> 
> A cell with 84% of rated capacity should still have plenty of useful life left considering that it's probably at least 90% of its actual initial capacity...
> 
> Something is defintely wrong with his charger.


 
Exactly my thoughts. Thanks Mike.


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## moldyoldy (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

FWIW, although it is frustrating when a charger does not terminate the charge correctly - my problem also - I do not necessarily accuse the charger. 

I read on CPF that on many occasions the super-fast 15min chargers would simply reject a cell that was otherwise functional for the user. For that reason alone I would not purchase any 15min charger. Even the technical description of the AccuPower 20 charger indicates that it does some rather fancy calculations to determine impedance and thereby decide how it is going to charge a cell. ie: higher impedance means slower charging, etc. 

The point is that I have had missed charge terminations with my V33 BC-900, the AccuPower 20, the Maha 801D, the Maha 401FS, etc. all with 2500 or 2700mah cells. I did not really expect the C9000 to catch everything either. 

My belief is that the latest crop of high-capacity cells are much more tempermental than the older cells - of about 2000mah capacity. I consider it significant that the Eneloops started out at 2000mah capacity - much lower than the latest in the capacity race for AA cells! As someone typed recently on CPF, with a limited volume to the cell size, to increase the cell capacity usually means making design compromises, such as thinner separators in the cell. End result - shortened life and increased susceptibility to events or conditions that the older cells tolerated very well.

Tim


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Actually, right before I took the pictures, bay#2 voltage was constantly reading 1.52 volts. The picture shows 1.50 volts. So the voltage was on it's way down between when I wrote down the numbers and when I had the camera in-hand.


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Exactly my thoughts. Thanks Mike.



It's you who deserves the thanks for posting in detail about this.

I've got two being delivered today. One is for a friend who is getting it based solely on my advice and I feel responsible for it behaving decently. He's very smart and technical but doesn't have the time to baby sit the charger. I don't really either but I guess I'll have to ask him if he's ok with me checking both. I almost hope it fails right away as the alternative is at least several days of testing to try and develop confidence in it. Maha blaming it on the cell only gets me more worried.

I should have known better and waited. Just on a string of bad luck... Ordered a P1D CE a month ago that still hasn't gotten to me 9 days after it shipped and 4sevens wants me to wait until next week before he'll ship a replacement. 9 days, 800 miles...getting aggravated every time I open the mail box...

If you decide to run any more checks before returning it, I'd appreciate you giving us updates.

Mike


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Unfortunately this break-in cycle I am doing will take me into Saturday morning (if he power doesn't fail  )

So far, I'm at 460 minutes at the initial 0.1C, and each bay reads 1.39 volts.

The next thing I will try (we're talking Sunday) is to try new Sanyo 1000 mA*h AAA's I just got from TD a little while back. That should eliminate the "old battery" variable.


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## willchueh (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

EngrPaul,

I would suggest a simple test to verify proper operation of the termination logic. Fully charge a battery. Let it rest (for about one hour), then recharge it. Please let us know the amount of charge delivered after termination. 

Do four at a time so we can verify consistency between the slots. 

Thanks!

William




EngrPaul said:


> Unfortunately this break-in cycle I am doing will take me into Saturday morning (if he power doesn't fail  )
> 
> So far, I'm at 460 minutes at the initial 0.1C, and each bay reads 1.39 volts.
> 
> The next thing I will try (we're talking Sunday) is to try new Sanyo 1000 mA*h AAA's I just got from TD a little while back. That should eliminate the "old battery" variable.


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> EngrPaul,
> 
> I would suggest a simple test to verify proper operation of the termination logic. Fully charge a battery. Let it rest (for about one hour), then recharge it. Please let us know the amount of charge delivered after termination.
> 
> ...



Now that's more like the support I hoped we'd get!

Thank you from another customer!

Mike


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi William,

After the break-in, I will do what you ask.

Which batteries do you want me to use? (Older 850 mAh or new 1000 mAh)

What charging rate?

What if it won't terminate? How do I determine when? 

I could use my pocket IR thermometer and watch for a certain temperature...

Thanks for your help...

Paul


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## willchueh (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Paul,

Let's use the 1000mAh at 1000mA rate. So basically charge twice and let us know the charge delivered in the 2nd charge. It should be done within 5-10 minutes. 

William



EngrPaul said:


> Hi William,
> 
> After the break-in, I will do what you ask.
> 
> ...


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## dekelsey61 (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi William,
If you follow the not charging below the 0.33C and a discharge rate of 0.2C you should not have a problem with the charger missing the termination of the charge in the refresh mode? Thank you.
Dan


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Paul,
> 
> Let's use the 1000mAh at 1000mA rate. So basically charge twice and let us know the charge delivered in the 2nd charge. It should be done within 5-10 minutes.
> 
> William



I can understand why William prefers you using newer cells but brand new cells might terminate the first charge early due to false -dV/dt detection. They might then accept significant charge on a restart because they weren't charged fully on the first cycle even if the charger is working correctly.

Not to mention that personally I'd prefer not abusing brand new cells with an overcharge... darn, went and mentioned it...

That said, he's the support guy in the hot seat, not me...been there, done that, not always fun 

Mike


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

The two C-9000 chargers I ordered just arrived.

First impressions
- Duracell 2300 mAH AA are a very snug fit and a bit of a pain to pull out.
- Display is very bright and legible. Nice!
- Easy to set parameters (haven't read the manual) but HATE having to do it for each cell when inserting multiples at the same time.
- I hate the way the display sequences through mA delivered, charging current, charging time and voltage. What makes it even worse is having to wait for the voltage that appears last after switching to each cell. I can judge charge status pretty accurately just by see the current voltage and knowing the cells I'm charging and the rate I set. I guess I'm spoiled by the BC-900 where a quick glance gives me all the volatges at the same time once you select it once.

I put the Duracells on a 1000 mA charge. They are all probably between charged to 60-80% capacity. If/when the charge completes, I'll remove them, wait a bit and then put them on charge again as William suggests. I have to go out in a bit so I might not get results until very late tonight as I am NOT leaving them on charge when I go out.

Pity to abuse these cells by putting them on charge again fully charged as they all have pretty limited cycles on them... Oh well, got new Maha 2700 AA and 1000 AAA I ordered too so the Duracells are getting demoted anyway.

Mike


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## wptski (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> The two C-9000 chargers I ordered just arrived.
> 
> First impressions
> - Duracell 2300 mAH AA are a very snug fit and a bit of a pain to pull out.
> ...


Mike:

All cells are hard to remove!


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> All cells are hard to remove!



Not AAAs but they seem to insert far less securely.

Mike


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## coppertrail (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I found that it's easier if you pull the AA cells backwards towards the negative end, then lift them out of the charger.


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## Mike abcd (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I got some early results and they're a mixed bag, definitely not all good. Cells were all probably about 80% charged thinking about it more as they'd finished fast charge on the Lenmar and then been removed.

Charge rate was 1000 mAH per William on Duracell 2300s.

Slots 3 and 4 terminated around the same time at about 20-30 minutes. The C-9000 stopped charging completely without doing a top off charge or only did it for a few minutes and I missed it. Cells were luke warm when removed a bit after charging. Everything was about like I'd expect.

Slot 1 charged a lot longer, roughly an hour but I didn't log it as I was busy and distracted with other stuff. Cell got pretty warm, roughly like the BC-900 near end of charge at the same 1000 mA rate. No top off charge observed so it probably terminated on -dV/dt and not dT/dt.

Slot 2 eventually completed at 113 minutes with 1667 mAH reported. Reported charge appears to be lower than actual by about 10% as the charge rate shown was about 980 mA. I suspect Maha fudged the numbers to avoid confusing users who don't understand charge efficiency.

Slot 2 severely overcharged the cell IMHO and the cell got very hot. I suspect it may have terminated on a high cell temp cutoff threshold.

Sorry for the sloppy reporting but I really shouldn't have even tried it with everything else I had going on. I'm running out but may try charging the cells again when I get back but it will be very late or tomorrow before I can provide an update.

I'd suggest monitoring the C-9000 carefully and using higher charge currents for now to try to give its -dV/dt more to work with and give its delta temperature cutoff a chance to work. Or just wait for mre info from other users or Maha.

Hopefully William will comment and offer his advice.

Mike


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## EngrPaul (Dec 28, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I should be able to do Willam's request for both the 850 and 1000 AAA's Saturday. Four cells at a time.

I'll do it at a time I can be around for the end of the charge and monitor what happens, including temperature readings. I won't let my cells get fried... esp. the new ones.


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## EvilLithiumMan (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I'm running into a similar situation. After doing my line dropout test, I inserted the four Powerex 2000 cells and just let it go at the default settings and went to sleep. I got up about three hours later, glanced at the charger and went back to sleep. As I dozed off, I thought remembered seeing one of the cells at 3000mah. Sure enough, when I really woke up, slot one was still going.







The cell is quite warm, but I can keep my fingers on it. As I recall, my threshold of pain is around 50C (122F), so no danger of a meldown. I'll try some of the suggestions here and see how it does a second time around.


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## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Friends,

As you are running into the same situation, please try to take notice whether the voltage is dropping or not. I have a suspicion -dV/dt is not being caught.

Also, when you have a problem shuffle the batteries to another location to determine whether the battery is the problem or the slot in the charger.

Thanks


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## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Friends,
> 
> As you are running into the same situation, please try to take notice whether the voltage is dropping or not. I have a suspicion -dV/dt is not being caught.
> 
> ...


If you miss termination, it's going to get hot very fast.


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## EvilLithiumMan (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Since -dv/dt is only on the order of 5mV and occurs over a few seconds, we'll never see it on the MH-C9000 display.

By the way, my slot one finished charging. Final time was 346 minutes and capacity of 5220MAH. Ironically, this was only moments away from when I took my pics. (345 minutes and 5203MAH). Clearly, I simply was too impatient


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## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> If you miss termination, it's going to get hot very fast.



Hey Bill, 

One of the "problem" with the MH-C9000 is that the cooling is "too good" for rates under 1500mA. From our test, even if a cell is continously charged at 1.0A, the temperature hovers around 115F and falls short of the high temperature cutoff. 

William


----------



## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike abcd,

Regarding your earlier question about the "charging efficiency:" 

The current shown on the screen is the "peak" current which is only applied 90% of the time. For example, if you select 2000mA, the current is 2000mA for only 2.0 seconds, and 0mA for 0.2 seconds. The brief rest time is part of the pulse charging and is also used to measure voltage, etc, since we do not want to include the resistance of the metal contact, etc and noises from high frequency used in the switcher. 

So the number shown is not fudged for "charging efficiency." 

William


----------



## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EvilLithiumMan said:


> Since -dv/dt is only on the order of 5mV and occurs over a few seconds, we'll never see it on the MH-C9000 display.


 
This is my point, I am seeing it on the display, which has a resolution to 10 mV.


----------



## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Hey Bill,
> 
> One of the "problem" with the MH-C9000 is that the cooling is "too good" for rates under 1500mA. From our test, even if a cell is continously charged at 1.0A, the temperature hovers around 115F and falls short of the high temperature cutoff.
> 
> William


William:

That's probably true! Where I've seen temperatures climb fast was probably at higher rates.


----------



## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just charged four 2.3Ah Duracells at 2A, allowed to cool and reinserted them into the same slots again.

Slot#1 = [email protected] min
Slot#2 = [email protected] min
Slot#3 = [email protected] min
Slot#4 = [email protected] min


----------



## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Bill,

What if you charge around 0.35C? = 800 mA


----------



## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

_Slightly off topic, but related to terminal temperatures..._

I just charged 4 AA Energizer 2500's in a MH-C204W. 

The terminal temperature when the LED's went from red to green was 145F.

I've always thought this charger makes the batteries just a little too hot. So I blow a fan across it (not this time). 

What effect does cooling the batteries with a fan have on termination? Does it fool the charger? When I use the fan, I still have proper termination on this old charger.

So far, I have not used the fan on the MH-C9000. I haven't seen those kinds of temperatures yet.


----------



## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Bill,

This is the expected result. Go ahead and try 800mA too, the result should be comparable. 

William



wptski said:


> I just charged four 2.3Ah Duracells at 2A, allowed to cool and reinserted them into the same slots again.
> 
> Slot#1 = [email protected] min
> Slot#2 = [email protected] min
> ...


----------



## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Bill,
> 
> This is the expected result. Go ahead and try 800mA too, the result should be comparable.
> 
> William


William:

Recharge the same cells I assume?

EDIT:

Same cells recharged at 800ma but not in the same slots.

Slot#1 = [email protected] min
Slot#2 = [email protected] min
Slot#3 = [email protected] min
Slot#4 = [email protected] min

Even closer than at 2A rate.


----------



## dekelsey61 (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi- Can anyone answer this question I wrote for William?


dekelsey61 said:


> Hi William,
> If you follow the not charging below the 0.33C and a discharge rate of 0.2C you should not have a problem with the charger missing the termination of the charge in the refresh mode? Thank you.
> Dan


----------



## dekelsey61 (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

EvillithiumMan or anyone- Why does the charger show 5203Mah when they are 2000Mah batteries? Is this normal if not how can you avoid this. Thank you.

Dan



EvilLithiumMan said:


> I'm running into a similar situation. After doing my line dropout test, I inserted the four Powerx 2000 cells and just let it go at the default settings and went to sleep. I got up about three hours later, glanced at the charger and went back to sleep. As I dozed off, I thought remembered seeing one of the cells at 3000mah. Sure enough, when I really woke up, slot one was still going.
> 
> 
> 
> ...


----------



## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Sure. 



wptski said:


> William:
> 
> Recharge the same cells I assume?


----------



## dekelsey61 (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi William- Is this safe and will the charger terminate correctly at these figures? Thnak you for your reply.

Dan



dekelsey61 said:


> Hi William,
> If you follow the not charging below the 0.33C and a discharge rate of 0.2C you should not have a problem with the charger missing the termination of the charge in the refresh mode? Thank you.
> Dan


----------



## EvilLithiumMan (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> EvillithiumMan or anyone- Why does the charger show 5203Mah when they are 2000Mah batteries? Is this normal if not how can you avoid this. Thank you.
> 
> Dan



This thread was started by EngrPaul who noted he had two AAA cells whose charge wasn't terminated as expected. I was simply adding my own similar experience with an AA cell. It's not normal and we are still exploring what may have happened. My Powerex 2000 cells are pretty old and have seen a lot of service. That may be a factor.

I tried willchueh's suggestion of letting the cell cool for an hour and reinserting it. No problem at that point - charging terminated normally.

(Some don't care for the fact that each slot has to be programmed, but I find it doesn't take very long and like the feature. And the display is simply wonderful for my tired, old eyes. And if some find it too bright to have it on at night, placing something as common as a playing card over it blocks the light. Although a giant compared to my BC-900, I love it).


----------



## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Sure.


I did, edit above.


----------



## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

EvilLithiumMan,

Thanks for your (and many others) suggestion on "group programming" and "on/off for backlight." I've added them to the "wish list" which the development team reviews. 

dekelsey61,

Based on internal testing, certain cells don't produce sufficient negative delta V to be terminated properly. I would recommend upping the charging current to at least 0.5C (as opposed to 0.33C on the manual). But the temperature protection will always kick in if the temperature rises to high. 

William


----------



## willchueh (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> I did, edit above.



Those figures look good to me.

William


----------



## SciGuy (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Two of my four brand new Sanyo 1000mAh AAAs did not terminate charge and reached over 1600mAh before I noticed the situation. I had given the cells an intitial partial charge of 100mA for 6 hours followed by a discharge at a 200mA rate. This was then followed by a charge at 700mA rate that resulted in appropriate termination for only two of the four cells. These were fresh cells just received from TD along with the MH-C9000. 

Perhaps a longer break in charge would have helped but the gross over charge with the .7C rate is really bothering me. I assume that the two cells have probably lost significant potential life already due to this overcharge.

Hugh


----------



## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

SciGuy,

Are you keeping track of which bay is overcharging? What if you switch the batteries around? Does it follow the batteries or the slot?

I'm sorry to ask so many questions. I'm running a break-in cycle which has me offline from testing the unit two days. :~


----------



## SciGuy (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> SciGuy,
> 
> Are you keeping track of which bay is overcharging? What if you switch the batteries around? Does it follow the batteries or the slot?
> 
> I'm sorry to ask so many questions. I'm running a break-in cycle which has me offline from testing the unit two days. :~



The problem occurred in slots 2 and 4. I will be monitoring the situation much more vigilantly over the next few test charges. I have a set of 800mAh eneloops discharging at this time and would hate to "toast" them before a single use.

Hugh


----------



## EngrPaul (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hugh,

That's the same two slots that overcharged on me, #2 and #4.

Are we seeing a trend here?


----------



## dekelsey61 (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Maybe William from Maha can answer the question about slots 2+4 ovecharging in several chargers. That would help us all out. Thank you.
Dan


----------



## SilverFox (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Hugh,

Welcome to CPF.

How hot did the cells get?

Keep in mind that you will always put more in than you get out. A good rule of thumb is that the cell is charged when its temperature raises around 20 - 30 F above the ambient temperature.

New cells often present a problem. This is why the forming charge is important. It is terminated on time and not an end of charge signal.

With this charger, you will be able to determine if any damage has been done to the cells. Just do a discharge capacity test after the cell is fully charged, and compare the results to the other cells. 

Let us know what you find.

Tom


----------



## SilverFox (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Dan,

Keep in mind that while we have reports of some slots charging longer, there is no evidence that the cells have been damaged. We need to document the capacities from the cells to see if damage has occurred.

Just because a cell absorbs more than its rated capacity does not mean that it has been damaged. If the temperatures get hot and the thermal protection kicks in, that is different, and at that point I would be concerned.

Let's see what capacities people are getting and then we can determine if any damage has been done. It is interesting that there seems to be a trend developing, but I am not sure just what it means.

Tom


----------



## wptski (Dec 29, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I used both of my C9000's to D/C some stored cells. A bunch of which were old 2Ah PowerEx cells that discharged in a minute or two yet some charged to 1200mAh but some only 300-400mAh. They did terminate using 1A charging rate!


----------



## EngrPaul (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Cells A-B-C-D

Readings from above:

682 - 718 -722 -792

Note: Cells B and D were overcharged to about 5C before Break-In below.

After Break-In routine:

689 - 754 - 741 - 794

It appears the overcharge did not damage the batteries, as measured by capacity.

After rest, the batteries went back in for a 1.0C charge (800 mA). They all terminated in 5 minutes. Here are the capacity readings based on the additional top-off:

60 - 55 -55 -61

After another rest period, I put them back in for a 0.33C charge (300 mA). They all terminated in 10 minutes. Here are the capacity readings:

58 - 56 -54 - 53

The highest temperature reached in this final charge was 93F.

Before I move on to another set of batteries, I'm going to do one more exercise. I'm going to swap battery locations to D-C-B-A and do the Refresh & Analyze at 0.7C/0.2C, to try to duplicate the original failure.


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I was trying to duplicate problems users are having so I took four 1.8Ah PowerEx cells that came out of a portable radio. I set the C9000 at 600ma which is a bit over .33C.

Slot#1 = [email protected] min
Slot#2 = [email protected] min
Slot#3 = [email protected] charging
Slot#4 = [email protected] min

I spot checked temperature through the night and Slot#3 which is still going never got warmer than 127F and Slot#2 by the way is at 92F, probably heated by Slot#3 and from the charger itself which I proved in the other C9000 thread. Right now Slot#3 is at 122F and the others are at 88F.

I assume that these cells missed -DeltaV termination but are too cool to terminate for temperature but use max voltage.

I'm pulling the plug on Slot#3 as it's over 6C now. I'm going to allow them to cool and discharge at 400ma nearest to .2C to check capacity.

Discharge results:

Slot#1 = 2020mAh
Slot#2 = 1927mAh
Slot#3 = 2037mAh
Slot#4 = 2035mAh

Note that Slot#2 the only one that terminated properly is the lowest but Slot#3 that never finished is close the other three.

EDIT: Recharge results:

Slot#1 = [email protected] min
Slot#2 = [email protected] min
Slot#3 = [email protected] min
Slot#4 = [email protected] min

As the Slot#4 was DONE, Slot#3 is still the warmest cell at 122F which is the cell that never finished. All cells are in the same slots during these tests. Hmm, maybe I should swap them around, hey?


----------



## Lonely Raven (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I'll throw my hat in here.


I've done a Refresh and Analyze on about 5 sets (of four) of Energizer 2500ma AA cells in the past few days.

I had one drastically overcharge when I was doing a 500ma/500ma R&A and you guys pointed out that was bad. 

So I upped the next set to 1000ma/1000ma and got around 2200ma each on completion of the next set. A bit low, but these were from my fiance's camera flash...so who knows how she's treated them.

Did another set at 1000ma/1000ma and the results were all over the place. two were 2200ma, one was 2375ma and one was 2475ma. One of them was WAY overcharged showing something like 5200ma, I don't recall what slot it was. These were again from my fiance's camera flash, so I figured the mix of discharge totals were due to her mixing batteries and previously dubious charges...so on to my sets.

I opened up one of my three flashes, all the same Energizer 2500ma, I did a set at 1500/1000 and the one is slot 4 way overcharged. all of them finalized at around 2320ma, give or take about 30ma which I figure it well within tolerance.

Next flash, R&A at 1500/1000, again all terminated around 2300 but slot 2 way overcharged.

Last flash, R&A at 1500/1000, one terminated at 2230, two at 2330, and one at 2430. Not sure why my last flash had such wild results. Maybe my fiance borrowed batteries out of my flash a few times. 

So I too have had wild overcharges in slots 2 and 4. But I thought one set I did also had an overcharge in slot 1.

I've discharged some of the overcharged units, and they all came in around 2200-2350 which appears to be about right for these cells.

These are all decently new cells, the oldest ones being about 6 months old, but they do get used a lot. The ones that were the most consistant were the ones that have been used the most.

I'm not sure if this info helps at all. Sorry I didn't keep any proper logs, I've just been busy with other things and really didn't think to log the detals. So take everything with a grain of salt.

I'm doing a Break-In on some fresh out of the package Energizer 850ma AAA, so I'll be off line from testing for another 24 hours.


----------



## EvilLithiumMan (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

wptski -
So out of four slots, only one terminated properly? Not good. I hope what I said in another thread does not turn out to be prophetic:

"My biggest fear is that this is a new and untested charger, and while I want one as soon as possible, I'm going to be pissed if 3 months from now "Version 2" of the C9000 comes out because the initial release had bugs. There are advantages to waiting."


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EvilLithiumMan said:


> wptski -
> So out of four slots, only one terminated properly? Not good. I hope what I said in another thread does not turn out to be prophetic:
> 
> "My biggest fear is that this is a new and untested charger, and while I want one as soon as possible, I'm going to be pissed if 3 months from now "Version 2" of the C9000 comes out because the initial release had bugs. There are advantages to waiting."


William Chueh mentioned somewhere that the .33C rate in the manual should be changed to .5C. I had no problem using 1A rate on 1.8Ah or 2.0Ah cells on either of my C9000's.


----------



## EngrPaul (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EvilLithiumMan said:


> wptski -
> 
> So out of four slots, only one terminated properly? Not good. I hope what I said in another thread does not turn out to be prophetic:
> 
> ...




If the charger has bugs which result in documented failure to work as defined in the specifications, I consider that a defect in workmanship and materials. The charger has a three year warranty for such. It will be up to Maha Energy Corp to correct the defect, however this is best done.


----------



## dekelsey61 (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Has anyone found a safe charge rate to set and none of the slots overcharge the cell? I have been following this post for some time. I have some 2700Mah+2500Mah and 2000Mah batteries and want ot know a safe charge level. I read about the 0.5c rate but have not tried it yet. Thank you.
Dan


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Has anyone found a safe charge rate to set and none of the slots overcharge the cell? I have been following this post for some time. I have some 2700Mah+2500Mah and 2000Mah batteries and want ot know a safe charge level. I read about the 0.5c rate but have not tried it yet. Thank you.
> Dan


William Chueh suggested .5C instead of .33C, it's worked for me.


----------



## EngrPaul (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

To determine an appropriate minimum C, I think a lot of us will have to be doing charges from a fully discharged state, up to a fully charged state. This will take some time until we develop this statistical data. 

It seems termination happens OK at any C when topping off.


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> To determine an appropriate minimum C, I think a lot of us will have to be doing charges from a fully discharged state, up to a fully charged state. This will take some time until we develop this statistical data.
> 
> It seems termination happens OK at any C when topping off.


My 1.8Ah cells weren't discharged fully and one cell hasn't finished yet at 7942mAh.


----------



## SilverFox (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Perhaps we need to be looking at the battery manufacturers recommendations...

They state that you get a strong end of charge signal when you charge at 1.0C.

The end of charge signal is difficult to determine on new cells, cells that have been in storage, and damaged cells.

You should be able to charge at 0.5C without problems, once the cells get formed and 
broken in.

The other "safe" charge rate is the 0.1C for 16 hours.

I know there is a lot of interest in the mAh going into the cells, but keep in mind that we have seen variations in this for a long time. We just never had a way of measuring it. Cells end up finishing the charge at different times all the time. I will note that some of these times seem to be extended beyond normal, but I don't know the condition of the cells. I have had damaged cells take forever to finish the charge, and come out working fine.

As interesting as the charging mAh are, it is the discharging mAh that count when you turn your flashlight on.

A good way to check things out would be to start with new cells, do a break in cycle, then do 5 cycles of refresh and analyze charging at 1C and discharging at 1.0 amp. Now we have cells with known characteristics and can put the charger through its paces.

When you are evaluating something and keep adding in new variables, you have a difficult time figuring out what is what.

I agree that a charger should handle all sorts of situations safely. If a cell is not behaving, it should not melt the charger down. We have seen some extended charging, but no melting down or excessive heat. When a discharge cycle is done on the cells that have been charged for an extended period of time, the discharge capacity is in line with the other cells, indicating that no damage has been done to the cell. 

This charger/analyzer allows us to set a wide range of parameters. When we choose marginally correct parameters, it seems to protect us from ourselves. 

Tom


----------



## SilverFox (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

Any idea of the cells temperature?

Tom


----------



## dekelsey61 (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I am using the break-in mode on all of my batteries that I have new and old before I try and charge them at the recommended rate and see if I have the same problems as you all.
Dan


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> Any idea of the cells temperature?
> 
> Tom


Tom:

The one "still" charging is at 122F and the others still inserted are in the mid 80's.

EDIT: I keep on updating Post#60 for the cells input.


----------



## moldyoldy (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

FWIW, just to continue to share experiences with the C9000:

I originally responded to EngrPaul with my own single failed charge cutoff detection back at the beginning of this thread. However now that a few more days have passed and the C9000 has been in continuous use, I have to admit that after that single charge cutoff detection failure, I have not had any problems with charge cutoff. The cells "finish" or go on "Rest" time reasonably close to each other.

I have not yet tried out the cycle feature - that takes too much time and I have other cells with which to test capacity. ditto for the break-in feature. I will eventually try it just to see how it works, but not for the next couple days. All other features have functioned as advertised, save for the isolated charge cutoff failure during Refresh.

Tim


----------



## EngrPaul (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I wanted you folks to have a progress update, even though the R&A cycle isn't complete yet, because it looks like the lack of termination is following the batteries, not the slots in the charger.

Previously I ran A-B-C-D in slots 1-2-3-4

This time I inserted them D-C-B-A in slots 1-2-3-4

Slots 2 and 4 failed to terminate before, this time slots 1 and 3 are overcharging.

Here is the current progress:

Slot 1 has charged 1.5C and is still charging cell "D".

Slot 2 is still saying "discharge" at 1.02V, however it reads 0mA. A minute ago it was at 1mA, so I suppose it's below .5mA and rounding down now. This cell "C" behaved this way in slot 3 before.

Slot 3 is still charging cell "B", currently 1.9C delivered.

Slot 4 has completed charging cell "A", I believe it terminated properly.

So it would seem this charger isn't tolerant of "older" batteries, both for termination signal (charging) and for high internal resistance (discharging).

EDIT FOR UPDATE:

Finally slot 2 has reached full discharge and now is at REST, waiting an hour for charging. If you don't hear back from me, assume this battery terminated properly.

I lifted the batteries being overcharged (131F) out of slots 1 and 3, and dropped them back in to the same slots, at the default 1000 mA (1.2C for these batteries) instead of what I was using (600mA / 0.7C). They both terminated soon afterward.


----------



## wptski (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I'm editing Post #60 to reflect all my findings.


----------



## Handlobraesing (Dec 30, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> 2. EngrPaul, regarding your overcharging experience, I am fairly confident that the cells did not produce the end-of-charge conditions necessary for the cells to stop. The main mechanism is Negative Delta V at about 5mV, followed by maximum temperature at 54 deg C, temperature change, then timer. Of course, the timer protection is very long due to the high capacity the unit supports (except for BREAK-IN mode which prompts for battery capacity - the charger recalculates timer based on this).
> 
> The problem is the cell didn't get hot enough and borderlines the temperature limit.
> 
> If you look at the capacity of the battery (slot B), it is at 84% of the rated capacity, indicating that it is towards the end of its useful life. This would explain for the weak negative delta V signal.



Lack of -dV signal has been identified in aging batteries in Sanyo engineering documents and it is discussed in the charging method. For quick charging, they suggest:

1. Primary termination -dt/dT and/or -dV
2. Timer shut-off to prevent ride-through if -dV is missed.
3. safety shut off if Tmax is reached before either of the above takes place or something malfunctions. 

Lack of ride-through shut off is a problem all one-size-fits-all chargers that charges or capable of charging a battery at beyond safe continuous charge rate including the MH-C9000 and the LaCrosse BC-900. If the MH-C9000 incorporated a user programmable maximum charge time, this would be partially solved (I say partially, because it's still at the mercy of user error)

Most chargers don't use -dT/dt so temperature isn't really used in normal charging control. Since missing -dV is rather common, on a universal fast charger, #3 is the only thing to lean back on. Earlier version of BC-900 had questionable Tmax shut off, so the result was a meltdown when -dV was missed.


----------



## bob_ninja (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> ...
> I agree that a charger should handle all sorts of situations safely. If a cell is not behaving, it should not melt the charger down. We have seen some extended charging, but no melting down or excessive heat. When a discharge cycle is done on the cells that have been charged for an extended period of time, the discharge capacity is in line with the other cells, indicating that no damage has been done to the cell.
> 
> This charger/analyzer allows us to set a wide range of parameters. When we choose marginally correct parameters, it seems to protect us from ourselves.
> ...




No meltdown is mandatory - so far so good. "excessive heat" is somewhat subjective and can be debated. I am not sure about "no damage" as any damage done may not manifest short term. I am rather puzzled how 1C or even 0.5C charge rate delivered for an extra hour or two can cause no damage while the cell temp is just below the safety level. I don't mean to be a smart azz. If we already established that most 2500+ capacity AAs have a fragile construction (thin separators) then my guess would be that they don't handle extra current very well. For instance, your tests have shown that super high current delivered by 15min chargers does shorten the lifespan.

William,
While I didn't order your charger, I was hoping to purchase a later version that would fix any possible issues. I appreciate the difficulty in handling varying capacities while at the same time trying to avoid overcharging. Others mentioned the forming mode takes cell capacity as input. Perhaps you could enable the same input for ALL MODES so that they all can have a 1.5C max current limit. That way a 2500 mAh AA charge would terminate after 3750 mAh is delivered when all else fails. Moreover, when this limit is reached you could signal an error icon, indicating that the battery may be too old or defective.

If individual slot setting is too much/difficult, you could allow a user to modify the global charger setting for max current delivered. You could have a setting for each format, AA and AAA. As we tend to use similar capacity batteries this would work well also. That way your factory setting can be initialized at some super high, say 10Ah, and users could fine tune to something closer to their specific case.

I think most all users don't expect a huge delta between rated capacity and charger delivered current, even if it doesn't cause significant damage. My BC-900 never does that and I often use the pathetic 200 mAh rate. I suspect that it is more sensitive and it will err on the side of caution, terminating too early. Personally I prefer that choice. I'd rather re-insert a battery to verify a full charge. That being said, the danger of a missing termination signal remains. That is why your charger can fix this issue once and for all by allowing user entered current limit (that is lower than the absolute factory set maximum, of course).

Again, don't want to sound too critical. I do expect this charger to exceed BC-900 while matching its reliability at least. I also charged some fairly old AAs in BC-900 with no termination issues. By now many people have charged all sorts of batteries in their BC-900 and with a few exceptions haven't had any problems. I think that most users would assume the ability of a charger to cope with all sorts of batteries, new and old, low and high capacity, etc.

P.S.: While the standard advice is to use 0.5C to 1C rates, BC-900 proves that lower rates as low as 0.1C can still be managed safely (well 99% of the time  Therefore I consider 0.1C to 0.5C rates still valid (which is my personal preference as I am usually not in a big hurry). I generally try to use about 0.3C - should be good enough for proper termination.


----------



## Turbo DV8 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EvilLithiumMan said:


> wptski -
> So out of four slots, only one terminated properly? Not good. I hope what I said in another thread does not turn out to be prophetic:
> 
> "My biggest fear is that this is a new and untested charger, and while I want one as soon as possible, I'm going to be pissed if 3 months from now "Version 2" of the C9000 comes out because the initial release had bugs. There are advantages to waiting."


 
I hope it isn't so, but I might turn out to be an even better prophet than you, because prior to your "prophecy", and even as my two BC-900's were terminating happily away and everyone was jumping on the Maha pre-order bandwagon, I made this post:




> Devil's Advocate, here. So, just how prudent is it to jump and pre-order from the first of a production run of any entirely new electronic or mechanical product? To just, say, pull an example out of the hat at random... how many revisions does this make for the La Crosse now? Although always in search of the holy grail of battery chargers, the ones I have right now do the job well enough to persuade me to sit back and let the early adopters discover the kinks on their own dime, then let Maha address them. So please, please, please ... go ahead and pre-order the new Maha!


----------



## bfg9000 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Well after charging dozens of high capacity cells without issue, I've run into a no-termination condition on one of four new (but old stock) 1850mAh AA cells. They were charged once with a timed forming charge a month ago, and used lightly since on the original charge. All charged and discharged uneventfully using refresh/analyze, but on the final 900mA recharge, I noticed all were "done" except the cell in slot one. That one read 9485mAh at 699 minutes, 1.39v, and I left it on charge to see what would happen because it was only slightly warm.

When it read "done" the one cell read 732mAh and 122min for the discharge performance. The other cells read 834mAh/167min, 846mAh/177min, and 1386mAh/244min so I guess they may need more cycles or a discharge and reform for best performance. I found it a little strange that the charger would happily pump nearly 13 times the capacity it had just tested back into the cell, though don't really care (aside from the wasted time) if it turns out that does not damage anything. I mean the cell didn't get very warm at all.

Most likely just dud cells (or too new) but I think I'll be trying higher rather than lower rates when using the smart modes, at least until this is sorted out. Like other Maha chargers this one probably indicates a _termination by high voltage_ by flashing the "done," but what I'd really like is some indication when termination was caused by _high temperature_.


----------



## Handlobraesing (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Is this charger capable of having the firmware updated?


----------



## EvilLithiumMan (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Well, I was hoping my mortal existance would prove more interesting than staring at a C9000 screen for hours on end, but I guess not.

At any rate, I've done a couple more cycles with the Powerex 2000 cells that originally resulted in slot one not terminating properly. Not one failure since then. I've also done a couple of tests where the fully charged cells sat for one hour, then went back in the charger even though they had a full charge. Again, no problem. The charging terminated in about 8 to 10 minutes, cells barely warm.


----------



## bwm (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> To determine an appropriate minimum C, I think a lot of us will have to be doing charges from a fully discharged state, up to a fully charged state. This will take some time until we develop this statistical data.
> 
> It seems termination happens OK at any C when topping off.



I have been charging my AAA batteries since I received my Charger using the Refresh Analyze setting. When I chose the minimum charge rate I found that none of my batteries terminated charge. I pulled the battteries when I checked the charger and found they had 4000mah put into my 1000mah Duracell's. 

After letting them cool and puttting them back in the charger I found that all the batteries would then terminate properly using the low charge rate. The tester would rest the batteries then discharge the batteries. Then, once again the batteries would not terminate properly.

I changed the charge rate to .5c and now all my Duracell 1000mah batteries terminate properly.

I do have one old Energizer 950mah battery and put it through a refresh analze and it has gotten quite hot (no ir thermometer to check the temperature). By leaving my thumb on the battery it reminds me of how my HDS EDC U60GT feels for temperature when I was testing it's runtime on it's highest setting. Currently it is reading 1628 mah 497ma 217 min 1.49 volts - it currently is in slot 3.


I have charged three different manufacturers AAA batteries in my charger so far: Duracell AAA 1000mah purchased about 2 months ago, Energizer AAA 950mah purchased about one year ago, and Rayovac AAA 700mah batteries purchased in late 2002 or early 2003.


Brian


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Jumping on a soap box . . . . . . . .

Here are some of my thoughts as an owner of a C9000 regarding our collective experiences provided in this thread regarding the C9000. Without any other data, and sweeping forward to a broad and possibly fallacious conclusion, .... 

it appears that high-capacity Ni-MH cells with a higher impedance tend not to terminate correctly using the C9000. It make no difference whether the cells are "new" or "old". Once the cell has been fully cycled at least once, the impedance drops and the cells terminate correctly. Ergo, the C9000 charger has difficulty sensing the proper charge cutoff signal on cells with higher impedance.

I recall from a German test description of the inner workings of the Accupower 20 charger that it specifically performs impedance tests on the cells to determine the actual charging rate - namely that the charger does not charge at a fixed current rate each time a cell is inserted. Consistent with that comment I have observed that some AA cells require a noticeably longer time to charge to cutoff in the AccuPower 20, yet the cells came from the same purchase, and came out of the same flashlight in use. The documentation further states that corrective treatment for a high impedance cell could take 3 or more cycles to correct. ie, just because the cell is newer or older has no close relationship to the internal impedance. Also, I note that the Sony BCG-34xxx AAA/AA charger performs some sort of cell test before it starts charging, and states that in the manual as well. It is unknown to me which actual tests are peformed by the Sony charger at start of charge.

So what is the point of my comment? With the C9000, we set the exact charging and discharging parameters, the charger does not. the only option left for the charger is to determine the -dV/dT cutoff, and that is preset via some sort of moving average window etc. in the ROM. If a high-impedance cell (new or old) can fake out the moving average + whatever other voltage change determination the designers programmed, then the cutoff signal is missed. The cutoff window can be tighter or looser which may result in a false signal and early charge stop. The design may entail adding some additional time after the actual cutoff detection to ensure the battery is really fully charged (overcharged) aka the C204W. of course that overcharge reduces the battery life. I believe that William C. stated that in the case of the 808/801D/800S Maha the designers intentional chose a safer cutoff to save cell life. In any case, I have had missed charge cutoffs in nearly all of the chargers I have possessed, from various Maha chargers (401FS, 801D, 800S) to the BC-900 to the C9000 to the AccuPower charger even to an old Radio Shack pulse charger. 

I find it interesting that I haven't noticed a charge cutoff failure in the Sony AAA/AA charger or the Maha 204W charger.

IOW, I cannot determine that the C9000 has had any more incidents of charge cutoff failure than any other charger I have had. condition noted that I obviously have not had months of experience with it yet. Furthermore, questions of a failed charge cutoff occurs w/o regard to whether the cells were "new" or "old". It seems to relate more to the recent usage - ie: full discharge or not, not lots of little top-off charges. Unfortunately, I didn't write anything down - only a faulty memory bank is available ....  However, once the first charge cutoff was missed, I cannot recall that it was ever missed the second time after a full discharge/charge. Whatever the problem was, was corrected in a full discharge/charge. 

FWIW, One of older Ph.D EE types at work states that he doesn't like to charge a battery until it drops below 50% charge level. There may be something to that experience since Fujitsu purposely holds off on a Lifebook battery charge until the cell charge level has dropped to less than 90%, then it starts a charge.


In any case, allowing a settable max charge time limit for each slot would be really tedious. Don't forget that this is a $60 charger - seems to be expensive compared to other $30-40 consumer grade chargers, but still not at the level of the Triton or Schulze which are hardly consumer grade chargers. We have 4 keys on the C9000. To truly set all of the parameters, you would need a real keyboard - ergo, a USB hookup, etc. now this charger is getting complicated. What was the target market and price?

End comment and I'll be off my soap box: I believe that all we are discovering with the C9000 is the vagaries of high-capacity cells and their "electrical" age, not their chronological age. Cell impedance is important! More than a few comments have been posted on CPF that the lower capacity Ni-MH cells were more reliable. 

'nuff said. off soap box.

Tim


----------



## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

High impedance on old/new cells may be the problem but will increasing the minimum charging rate to .5C solve it? Saying that, above is a post where .5C was used on 1.8Ah cells and it missed termination! 

Post #60 has been edited.


----------



## BVH (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Here are the results of my first set of brand new 4 Sanyo 2700's using Break-in Mode. All for slots terminated within 7 minutes of each other - around 955 to 961 minutes on the final charge.

First reading after the "Done" indicator came on:

Slot 1 - capacity 2619 mah, 1.46 Volts. 
Slot 2 - capacity 2640 mah, 1.47 Volts
Slot 3 - capacity 2623 mah, 1.45 Volts
Slot 4 - capacity 2614 mah, 1.47 Volts

Final charge mah were all approximately 38xx. All cells were a mild to low-moderate temperature at termination.

I remember the 16 hour initial charge will feed in much more mah than cell capacity but I don't remember anything about over-feeding on final charge? I need to go back and find that info.


----------



## dekelsey61 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

BVH- That is about the exact results I received when I did a Break-in mode on my new Sanyo 2700Mah batteries! I am breaking-in all my batteries to maybe avoid miss terminations in the charge and refresh modes. It is taking along time but If it helps that will be good. I am refreshing some of my Sanyo 2700Mah batteries now that I broke-in about a week ago. They finished the charge cycle in 25mins. Now are discharging. Batteries were just warm to the touch after the first charge. My settings in the refresh mode are 1200Ma charge and 500Ma discharge. Everything seems to be going ok.
Dan




BVH said:


> Here are the results of my first set of brand new 4 Sanyo 2700's using Break-in Mode. All for slots terminated within 7 minutes of each other - around 955 to 961 minutes on the final charge.
> 
> First reading after the "Done" indicator came on:
> 
> ...


----------



## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

just to be contrary, my C9000 _prematurely_ terminated charge for one cell of four brand new Sony 2700mah AA cells. All four cells were discharged in the Sony BCG-34HRMF (?) AAA/AA charger. The termination was in about 1/2 the charge time as the other 3 cells. not even close.

Tim


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## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



moldyoldy said:


> just to be contrary, my C9000 _prematurely_ terminated charge for one cell of four brand new Sony 2700mah AA cells. All four cells were discharged in the Sony BCG-34HRMF (?) AAA/AA charger. The termination was in about 1/2 the charge time as the other 3 cells. not even close.
> 
> Tim


Tim:

I take it that you discharged the cell to prove that it was premature? Isn't premature termination rather odd compared to missed termination??


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Bill, 

The new Sony (corrected from Sanyo) 2700mah AA cell was already discharged and charged once in the Sony BCG-34 AAA/AA charger with no problems. after a rest, I then discharged all four cells again in two L2T flashlights because too many other chargers were busy. It was nearly discharged when I pulled them to start the "Refresh" cycle in the C9000.

I am still waiting for the other 3 cells to switch to discharge. the wait is getting bothersome and the other cells are getting hotter. presently at about 3080mah into the three 2700mah cells, so not quite unacceptable yet.

Tim


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

FWIW, here is another comparison between chargers and dischargers (sic).

Cells are Powerex 2700mah AA cells, only a few cycles on these.

Charger #1 is 800S on 1A, discharge in the C9000 on test (no Refresh): 2490mah, 2547mah, 2504mah, 2521mah.

Charger #2 is the C9000 on Refresh(& test): 2540mah, 2589mah, 2512mah, 2567mah

Charger #3 is the BC-900 on Test cycle: 2.79Ah, 2.74Ah, 2.68Ah, 2.73Ah.

as we know, the BC-900 does not wait an hour between charge and discharge, so the mah values are elevated. however the numbers are reasonably compatible.

Remember that the 800S (and 801D and 808) were designed with an early charge termination to increase cell life. So the difference between the 800S and the C9000 is expected. (at least on my part)

Tim


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## bfg9000 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Just wanted to add my brand new low-capacity cells ended up fairly evenly charged _even though one was charged at 900mA some 10 hours longer than the others_:
1456mA
1350mA
1403mA
1409mA all when discharged at 500mA
So after the third charge on these cells (that have sat <1v for two years) capacity is looking quite a bit better.


----------



## coppertrail (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



moldyoldy said:


> Hi Bill,
> 
> The new Sanyo 2700mah AA cell was already discharged and charged once in the Sony BCG-34 AAA/AA charger with no problems. after a rest, I then discharged all four cells again in two L2T flashlights because too many other chargers were busy.


 Is the L2T significantly brighter using the Sanyo 2700s as opposed to Alkaline primaries? Sorry that this is off topic . . .


----------



## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Coppertrail, 

I am unable to answer your question regarding relative brightness with any 2700mah NiMH cells relative to alkaline cells. I simply don't purchase AA/AAA alkaline cells any more. The NiMH cells are simply too good and the nominal AAA/AA chargers are reasonable. I have had AAA alkaline cells come in, but only via purchases of, say, the Princeton Tec EOS or Quad (good headlights). Sorry!

In any case, given the regulation in the L2T head, I doubt that there would be much difference between alkaline cells and Ni-MH cells until towards the end of their discharge time. The alkaline cells would drop off sooner.

Tim


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Back to the C9000 testing.

Well, I purposely wanted to test for a probable problem with new cells and charge cutoff. The test was successfull! None of the new Sony 2700mah cells terminated correctly. One terminated charge at about 1/2 capacity. The charger indicated some 4000mah hours of charge (~140%) for the other 3 and I gave up. Those 3 are now on a straight discharge to see what the discharge capacity is. 

When all 4 cells have discharged, I will try out the "forming" charge mode. that in spite of the fact that these cells were already discharged and charged successfully w/o problem in the Sony BCG-34 charger.

So, I just provided more evidence that the C9000 has problems with charge cutoff, and from my observations, it is not dependent on cell slot. Slot number two held the Sony cell that terminated charge at about 1000mah of charge. The other 3 were in 1,3,4 and _I_ terminated charge at over 4000mah. I had no intentions of cooking good Sony cells.

I don't know the problem is with charge cutoff in the C9000. My other Powerex AA cells had no problem save the single event which I reported on back at the beginning of this thread. I suspect some difficulty with cell impedance, but that remains to be discovered.

FWIW, I also successfully discharged/charged some new Sony 2500mah cells in the Sony charger w/o incident. the same 2500mah cells were charged in the BC-900 w/o incident. These were the first Sony cells placed into the C9000.

addition: Forgot to mention - I was charging the Sony cells at 500ma. Discharge was also supposed to be 500ma - to be compatible with the BC-900 for capacity comparison reasons. for a 2700mah cell, that is now evidently considered low, but the Sony charger with 4 AA cells charges at a 525ma rate - per the manual - and it had no problem with the same Sony cells that the C9000 failed on all 4 slots to detect the charge cutoff.

Tim


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## SilverFox (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Tim,

A few questions...

What is the charge rate that you are using?

What is the charge rate of the Sony charger?

Is the Sony charger an independent channel charger?

Tom


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## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tim:

What charging rate did you use on those Sony 2.7Ah cells?

Darn, sneaky fox!


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## bcwang (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



moldyoldy said:


> FWIW, here is another comparison between chargers and dischargers (sic).
> 
> Cells are Powerex 2700mah AA cells, only a few cycles on these.
> 
> ...



Another thing we need to know is what voltage the c9000 decides to end the discharge test. I know the bc900 is .9 volts, but the c9000 may be ending it at a higher voltage thus giving it less capacity than would be reported in the bc900 even if inserted from the same state.


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## dekelsey61 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi bcwang,
My charger stops the discharge voltage at about 1.0-1.3v. As the batteries rest they go up to about 1.15v by the time the charge mode kicks in. Hope this helps you.
Dan


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## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Hi bcwang,
> My charger stops the discharge voltage at about 1.0-1.3v. As the batteries rest they go up to about 1.15v by the time the charge mode kicks in. Hope this helps you.
> Dan


Dan:

You mean 1.0-1.03V, right? I think that somewhere it was quoted to be 1.0V.


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## dekelsey61 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Bill,
Yes-It is never lower than 1.0volts at times it has cut off at 1.02volts. Most of the time it is at 1.0volts. Maha's web page if you look at the spec. it says the discharge voltage termination is 1.0volts.
Dan
I am sorry Bill- I ment 1.03Volts Typo error on my part.


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

yup, I knew you two would catch that omission - I added it at the end of my longish post - too late. 

Per the manual, the Sony BCG-34 charger charges at 1050ma for two AA cells, or 525ma for four AA cells. or, 640ma for two AAA cells or 320ma for four AAA cells. I have not actually measured the charge or discharge current. I have had two of these chargers and they worked flawlessly whether in my possesion or the recipients possesion. I routinely observe that the Sony BCG-34 charger does some sort of cell analysis for about 3-4 seconds when the cell is first inserted into the charger. I have no idea what it is testing.

For the BC-900 charger I chose the max discharge rate of was 500ma with a corresponding charge rate of 1000ma.

So my point was to try to match these rates or else I would not have had a comparison. I was trying to test for a discharge capacity difference from a full charge on various chargers. See 3 of my results in a previous post.

I had not in any way performed a "forming" charge on the new Sony 2500mah and new 2700mah AA cells. These were the cells as received from T-D as part of the package in the last week. I discharged and charged them on the Sony charger - nothing else.

My intention was to use the C9000 like the average consumer would use it for new cells - and not wait for some 2 day forming charge to be completed.

Except for a single incident, the C9000 successfully processed all of the Powerex (couple months old) and new LaCrosse AA and AAA cells. The normal modes for the C9000 were "Discharge" and "Refresh". I was saving the hi-capacity Sony cells for the last since they were of the latest 2700mah capacity. The C9000 failed on all four slots with the Sony 2700mah AA cells. Some characteristic of the Sony cells was really confusing the Maha C9000 charger. 

The path forward? discharge the Sony 2700mah AA cells and do a full forming charge on them - "Break-in" per the C9000 manual. After a couple days it should be done. Then I will try the Discharge cycle, then the same Refresh cycle that all four slots failed on.

Sigh, as another poster mentioned - watching the screen of the C9000 was not what I had planned for New Years Eve. 

However, the data is useful for the CPF community - we are all in the same situation - trying to discover the idiosyncracies of a new charger on the market that possesses more features than most of us have had available before.

Tim


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Oooops, forgot to mention - the Sony BCG-34 charger is an independent channel charger - the primary reason why I purchased it. I already had the Maha 204W which did not have independent channels.

The other reason is compact size - similar to the 204W. small size, no external wall wart, and 100-240VAC compatibility. Family members fly the Pond too often to ignore the voltage/frequency compatibility.

Tim


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## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tim:

It's already been proven that the .33C for low limit should be .5C and maybe 1A is too far below the low limit for the highest capacity cells


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## EngrPaul (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

OK, this is my last post of the year, and it's a positive one.

*I just finished R&A on four Sanyo Industrial 1000 mA*h AAA's. They all terminated properly with a 0.7C charge.*

Here are the capacities:

975 - 996 - 989 - 988

The first one was used lightly for about a month, the other three moderately in the same application.

So it looks like Sanyos are consistently good cells.

I'll be moving onto some AA's now, New Sanyo 2700's. Just for some more experience with known-good batteries. Then back to older batteries to see how things shake out.

Happy New Year everyone!


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## moldyoldy (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom,

A fair comment regarding the .33C rate being too low. I already knew that it was too low per prior posts, but was trying to be compatible with the BC-900 unit for a cross check of available cell capacity after a charge. I didn't really have any problems until the Sony 2700mah AA cells were inserted. What was really curious was the too-early termination! however a single data point is a degrees of freedom of zero - and a statistical significance of nothing. Nevertheless, my Sony 2700mah cells will go on a Break-in cycle. At the end of that Break-in, I will test them again intentionally on the 500ma rate using the Refresh/Analyze mode just to see what changed. I will discharge them first, probably in the L2Ts or the Sony charger.

BTW, regarding my single earlier failure to detect a charge cutoff on a somewhat used Powerex 2700mah AA cell - the charge rate was 1500ma. about 1/2C. All of the cells get hotter at that rate than my 801D at a 2A full charge rate. Maha changed something!

Happy New Year!

Tims


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## wptski (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tim:

Even with large spacing and gaps under the cells, this charger is heating the cells like hot dogs on a grill! Remember my IR images? Does some heat at the wrong time cause more heat???? A .5C charge on 1.8A cells, 3.5 hrs. later cells are still over 80F!!


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## dekelsey61 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Bill-
My batteries get very hot in the charger after the discharge cycle also. It is sure alot different than the 801D or the 808M chargers. Will all this heat damage the batteries? Thank you.
Dan




wptski said:


> Tim:
> 
> Even with large spacing and gaps under the cells, this charger is heating the cells like hot dogs on a grill! Remember my IR images? Does some heat at the wrong time cause more heat???? A .5C charge on 1.8A cells, 3.5 hrs. later cells are still over 80F!!


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## bfg9000 (Dec 31, 2006)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Guess it may be a good idea after all to do at least two forming cycles on new cells before smart charging them in the C9000, even though I've never needed to do this before for other chargers. Termination just seems a little touchy on it with newish cells, and perhaps that is the reason the _Break-In_ mode automatically does two forming cycles. The well used cells here seem to always terminate fine even at 0.37C (though WC has pointed out that not all cells are compatible with this) so it'll be only a one-time deal with the right cells.

I think this is reasonable and did not expect a $60 specialty product not intended for the average consumer to be perfect or free from compatibility problems. I mean nothing caught on fire, the overcharge hasn't appeared to damage cells or heat them enough to cause alarm or even notice if it weren't for the running tally on the screen. The average consumer likely doesn't care to have the analyzer part anyway so would probably be better served by the 801D.


----------



## BVH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Results of second set of 4 brand new Sanyo 2700 in my second 9000 charger added to compare with the first Sanyo 2700 batts and charger:

Here are the results of my first set of brand new 4 Sanyo 2700's using Break-in Mode. All four slots terminated within 7 minutes of each other - around 955 to 961 minutes on the final charge.

First reading after the "Done" indicator came on:

Slot 1 - capacity 2619 mah, 1.46 Volts.
Slot 2 - capacity 2640 mah, 1.47 Volts
Slot 3 - capacity 2623 mah, 1.45 Volts
Slot 4 - capacity 2614 mah, 1.47 Volts

Final charge mah were all approximately 385x. All cells were a mild to low-moderate temperature at termination.


Here are the second set of batts in the second charger results. All four slots terminated within 5 minutes of each other - around 960 to 965 minutes on the final charge.

First reading after the "Done" indicator came on:

Slot 1 - capacity 2599 mah, 1.46 Volts.
Slot 2 - capacity 2592 mah, 1.46 Volts
Slot 3 - capacity 2660 mah, 1.47 Volts
Slot 4 - capacity 2605 mah, 1.46 Volts

Final charge mah were all approximately 387x. All cells were a mild to low-moderate temperature at termination.

I think most importantly, both chargers performed almost identically and both terminated ok. No significant heating of the batts and no missing of termination.


----------



## Turbo DV8 (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Even with large spacing and gaps under the cells, this charger is heating the cells like hot dogs on a grill!


 

You could always suspend a little muffin fan over the charger, like every BC-900 owner without homeowners fire insurance does.  But I like your idea better. I could turn the fan off over my two BC-900's and lay a couple weenies across the eight AA cells charging at high rate. The AA grill marks would look so homestyle.


----------



## bfg9000 (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Bill + Dan, which cells are you using that get hot? I've tried everything from cheap Lenmars and Powerizers to Jetcells, PowerExes and Sanyos and none of them ever got hot in the C9000, even when termination was missed.


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## NiOOH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Bill + Dan,
Can you post some more info on the heating issues, i.e. which cells, what charging current, how hot. 
For me this will be the most important thing in making the decision to replace my BC900 with C9000 or not. I mean, it doesn't matter if the charger can do a lot of things if it cannot charge properly.
Please share some more info


----------



## moldyoldy (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Happy New Year NiOOH! 

Regarding _replacing_ the BC-900 with the C9000, I would not do that. they don't "replace" each other although some operational features overlap. The key aspect to either charger is the ability to set the charge/discharge current rate. The C9000 clearly has the better manufacturing product quality. I have both units and will probably keep each unit. The much smaller size of the BC-900 means a lot to me for Euro travel purposes whereas the C9000 is going to sit at home. If anything, ultimately the C9000 may by given to some budding young flashaholic rather than the BC-900. 

For example, if you don't need the more automated features of the C9000 along with higher discharge/charge current rates, and you have v33 of the BC-900, I would not bother spending the money. If I am willing to spend time and pay attention to what is going on with the BC-900, I can duplicate many modes of the C9000.

For example, by setting a charge rate of 200mah on the BC-900 in test mode, I can sort of duplicate the "Break-in" mode of the C9000 for AA cells. No, it is not a _timed_ mode on the BC-900, but I can watch for the termination or stop charging at 16hrs. If I don't require the one hour pause between charge and discharge, the BC-900 "Discharge" mode can adequately perform a capacity check comparable to the "Test" of the C9000. I just have to pay attention as the voltage goes below 1.10v to catch the capacity before the BC-900 starts charging again. I also have to adjust the displayed capacity down a bit due to the fact that the BC-900 discharges down to 0.9 v whereas the C9000 discharges down to 1.0. If the capacity difference is large, then the cell is already aging.

The last comment is to wait for the revisions on the C9000 before you purchase one. ....and there will be revisions of the C9000! Experience with the C9000 by CPF members mirror in some fashion the experience with earlier models of the BC-900. The BC-900 is a very capable unit - the first really adjustable charger that was w/in the consumer $$ of the the average flashaholic. 

As so many have said, the BC-900 has been revised how many times? and in Europe there is a BC-700 as well. I don't know who the original designer/manufacturer was, but the BC-900 is sold by a lot of vendors quite successfully. ...and yes, the BC-900 has generated lots of comment regarding it's ability to overheat cells and melt chargers! So also the C9000 is generating lots of comment regarding missed cell termination. Yes, the BC-900 problem is a safety issue, and the C9000 is not a safety issue, but overcooks cells anyway. Nevertheless, in terms of product cycle, the BC-900 is much farther down the road towards removing the undesirable effects. We have yet to see how Maha will respond to our obvious problems with charge termination.

As always, YMMV!

Tim


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## NiOOH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Thank you Tim and Happy New Year .

In terms of features, from what I gathered about C9000, it is supperior to the BC900. First, the BC900 cannot do a separate discharge cycle. This is annoying. Often , I'd like only to discharge the cells at a given current and get their capacity without running the charge cycle at twice the current. The break-in mode is also quite usefull. At 200 mA the BC900 does not terminate properly in 80% of the cases. Also the c9000 offers a wider selection of discharge currents. C9000 also appears to be better built.
Of course, all this doesn't count if the charger overrheats the cells.
I would pretty much appreciate if someone can measure the cell's temperature during charge at 0.5-1C.


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## wptski (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Bill + Dan,
> Can you post some more info on the heating issues, i.e. which cells, what charging current, how hot.
> For me this will be the most important thing in making the decision to replace my BC900 with C9000 or not. I mean, it doesn't matter if the charger can do a lot of things if it cannot charge properly.
> Please share some more info


Look at Post #29 in this thread: C9000 These two center slots get warmer earlier than the others, stay a bit warmer than the other two slots and the whole charger retains the heat many hours after the it's DONE. I can't think of any charger where cell temperature is retained so long. 

It's just something I'v noticed and seems odd. Does this retain heat damage cells? Not sure. One point is that during cycles where there is a hour rest period, cells sure won't reach room temperature. I charged 1.8Ah cells at 900ma and 3.5 hrs later after termination, cells were still over 80F.

EDIT: A .5C charge on 1.8Ah cells show 124F cell temperature but this "maybe" have been a tad before the last cell was DONE. A 600ma charge rate on 1.8Ah where one cell never finished after some 20 hrs for over 6C, I spot checked and the highest was 127F.


----------



## willchueh (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

A lot of the heat on the cells is from the charger. Remember, the charger has to step down from 12V to 1.6V and there is bound to be efficiency loss. Since power is proportional to the square of the current, the higher the charging rate the more heat loss from the charger.

A simple experiment will demonstrate this. If you charge 1 battery only vs. charging 4 batteries (using the same rate), you will find the former to be much lower in temperature. 

Adding a small fan definitely would reduce charger temperature (and consequently cell temperatures). 

I should also mention that charger temperature is strongly dependent on the ambient temperature. In my personal testing (at my home), I find the cell temperature to be only relatively warm when I use the charger in a non-heated room (I live in Southern California - I would say the temperature is about 65F). However, when I operate the unit in a heated room, I find the cell temperature noticeably higher.

This is because charger heat is generally given in "temperature rise." The higher the amibent, the higher the terminal temperature. 

Hope this helps - and prosperous 07 to all!

William


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## NiOOH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> EDIT: A .5C charge on 1.8Ah cells show 124F cell temperature but this "maybe" have been a tad before the last cell was DONE. A 600ma charge rate on 1.8Ah where one cell never finished after some 20 hrs for over 6C, I spot checked and the highest was 127F.


 
Hmmmm, 124F is not that cool for 0.5 C charge is it? We have seen chargers that operate cooler than that at this charging current. 
How does it compare to, say Maha C801. I still wonder how much of this heat is generated by the cells themselves (possibly due to overcharging) and how much is generated by the charger itself.


----------



## wptski (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Hmmmm, 124F is not that cool for 0.5 C charge is it? We have seen chargers that operate cooler than that at this charging current.
> How does it compare to, say Maha C801. I still wonder how much of this heat is generated by the cells themselves (possibly due to overcharging) and how much is generated by the charger itself.


You can read William Chueh's response above but others have stated that a C808M, I think charges cooler than a C9000 at 1000ma.


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## NiOOH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hmm... wasn't C9000 supposed to trminate with dT/dt of 1 degree Celsius per minute as a primary. I used to use a Lenmar Pro66, which used this termination (backed by -dV at 10 mV per cell) and at 2 A charging current the cells stayed below 115 F. I could think that at 0.5 C the temperature gradient of 1 C/minute is reached at higher temperatures, but there should be a secondary termination mechanism that kicks-in before the cells are so hot. 
How warm they get at 1C?


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## BVH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Bill, my 808M definitely charges significantly cooler in the 1000 mah mode than my 9000's. Even using the default 2000 mah mode, most cells stay mildly warm until the last few minutes, when some get very warm, some don't.


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## EngrPaul (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

William,

Your suggestion for cooling matches my wish for these chargers to have an internal fan to extract internally generated heat.

Thanks,

Paul


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## NiOOH (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> William,
> 
> Your suggestion for cooling matches my wish for these chargers to have an internal fan to extract internally generated heat.
> 
> ...


 
There are such chargers. Lenmar Mach1 Gamma for instance has a small internal fan, which cools only the internals of the chargers, but not the cells themselves.

Another such charger/analyzer is the Conrad Charge Manager 2010. It has two quite powerful (and noisy) fans for cooling off the electronics.


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## EngrPaul (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

... and I installed one in the bottom of a MH-C124S years ago. This charger used resistors to dissipate the voltage drop. I wondered where all that heat was supposed to go. 

I found that extracting heat from the case caused fresh air to enter from the battery terminal openings, thereby cooling the batteries (in theory).


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## SilverFox (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Well... I am not seeing any heat issues with my cells.

I just charged 1800 mAh cells at 2.0 amps. The maximum temperature was 122 F. I recall that the 808 was showing around 120 F under similar charging conditions. 

I have observed similar results when charging some AAA 850 mAh cells at 1.0 amp.

So far, I only have done 8 charge cycles, I consider heat a non issue with this charger. I get hotter temperatures (128 F) off of the BC-900.

Tom


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## wptski (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Well... I am not seeing any heat issues with my cells.
> 
> I just charged 1800 mAh cells at 2.0 amps. The maximum temperature was 122 F. I recall that the 808 was showing around 120 F under similar charging conditions.
> 
> ...


Tom:

How long to cool down though?


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## SilverFox (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

At one hour it was down to 77 F.

Tom


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## wptski (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> At one hour it was down to 77 F.
> 
> Tom


Tom:

Are you charging outside??  I charged 1.8Ah cells at 900ma, 3.5 hrs later still over 80F! I wonder why?

I used the thermal imager for those reading. I've put black electrian's tape on a cell but readings remain the same. I just took two small plastic cups filled with water and even put tape on one of them. Using a lab grade glass thermometer, I allowed the water to reach room temperature. They were within .5F of eachother! I was really not hoping to find a major difference between the two.

I can't understand why your cells cool so fast.


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## SilverFox (Jan 1, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

I don't know what is going on...

I have read the reports of cells heating up, but I just can't duplicate that.

I will have to try charging at a low rate to see if I can get them to heat up when the charger misses the end of charge termination signal.

Tom


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## SilverFox (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

This round was a little hotter.

Once again charging at 2.0 amps with 1800 mAh cells. Maximum charging temperature was 126 F. An hour later the temperature dropped to 79 F.

Not much to write home about...

Tom


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom Bill,
Thanks for the info. While still within safe limits 126F is too hot for me. I've used chargers that worked considerably cooler than that at similar charging current. To me, the main question now is how much heat is generated by the charger itself, and how much is generated inside the cells. Also, what is the end of charge temperature at different charging currents.


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## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Is anyone comparing terminal temperatures to manufacturer's suggested charging regimen? I recall seeing the terminal temperature at 100% charge is around 110F, and the slope is rather steep. If you want temperature to be the secondary termination method, you have to go to a higher temperature. And you consider the possible variations in cell manufacturers, thermosensors, ambient conditions, charger heat... the temperature is going to be higher unless you want to risk early termination. I expect the temperature to get up as high as 130-140F. I am not sure how damaging these temperatures can be to a battery's chemistry. I think it's just our human reaction that things too hot to hold on to are too hot period.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

I just discharged some 2.3Ah Duracells and I'm going to charge them at 1200ma. I'll have to practice a bit but I think that I have enough testing power to log temperature on all four cells at the same time. They won't be all sync'd together because I'll have to manually start three units after the last cell is inserted but they'll be close. They'll be three seperate graphs too, two will be similiar and the other different.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Is anyone comparing terminal temperatures to manufacturer's suggested charging regimen? I recall seeing the terminal temperature at 100% charge is around 110F, and the slope is rather steep. If you want temperature to be the secondary termination method, you have to go to a higher temperature. And you consider the possible variations in cell manufacturers, thermosensors, ambient conditions, charger heat... the temperature is going to be higher unless you want to risk early termination. I expect the temperature to get up as high as 130-140F. I am not sure how damaging these temperatures can be to a battery's chemistry. I think it's just our human reaction that things too hot to hold on to are too hot period.


What's terminal temperature? The BC-900 pauses at around 130F but I've never seen any reference to 110F.


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Is anyone comparing terminal temperatures to manufacturer's suggested charging regimen? I recall seeing the terminal temperature at 100% charge is around 110F, and the slope is rather steep. If you want temperature to be the secondary termination method, you have to go to a higher temperature. And you consider the possible variations in cell manufacturers, thermosensors, ambient conditions, charger heat... the temperature is going to be higher unless you want to risk early termination. I expect the temperature to get up as high as 130-140F. I am not sure how damaging these temperatures can be to a battery's chemistry. I think it's just our human reaction that things too hot to hold on to are too hot period.


 
140F is too hot. The maximum cell temperature suggested by most manufacturers is 131F (55C). This is also the temperature to which most chargers thermal protection is set. My BC900 (v33) pauses at 125-127F. In my experience everything above 120F is going to hurt cycle life. 
The good thing with using dT/dt (temperature gradient) is that you eliminate ambient conditions, unless the ambient temperature does not vary widely during charge. If you use dT/dt as a termination mechanism, at currents of 0.5C and above it will act as a primary termination mechanism, i.e. will be activated first at temperatures below 120F.

Another thing that puzzles me is this missing of termination issue. I've been using my BC900 for a year now mostly at 700 mA charging current. Before that used Vanson BC-1HU (later modification that also used 700 mA). I've done hundreds of cycles on these two chargers with cells ranging from 1600 mAh to 2500 mAh and never ever had any termination issues. It looks like even below 0.33C for 2500 mAh cells the voltage drop is sufficient to triger the -dV termination. What is the -dV value of the c9000? For such a sophisticated charger, I'd expect it to be below 10 mV per cell.

Perhaps it's time to hear from someone from Maha about all of this.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I was talking to SilverFox yesterday and he said that the C9000 used 3mv or was it 5mv voltage termination. Well, it's low anyway.

How about my case where one cell out four terminated when I knowingly used the too low .33C on 1.8mAh cells? Substained temperature above 120F for 20 hrs! The cell is marked so I'll know if it dies at an early age.


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> I was talking to SilverFox yesterday and he said that the C9000 used 3mv or was it 5mv voltage termination. Well, it's low anyway.
> 
> How about my case where one cell out four terminated when I knowingly used the too low .33C on 1.8mAh cells? Substained temperature above 120F for 20 hrs! The cell is marked so I'll know if it dies at an early age.


 
Hmmm, 5 mV per cell of -dV should definately be enough to terminate properly even at 0,33C.


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

... and yet another thought. IMO Maha engineers could have been a bit more conservative in setting the criteria for quick charge termination, since the C9000 does a top-off charge, i.e. there is no danger of significant undercharging. All this said, can someone please post these criteria as far as they are known at that stage.

dT/dt what gradient (how many degrees per minute)?
0 dV yes or no?
-dV how much voltage drop per cell?
max. T what value?

If I remember correctly these specs were posted somewhere, but I don't seem to find them now.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

The standard is 1.8F/min.
No ZeroDelta.
3-5mv/cell
Max temperature cutoff??????


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> The standard is 1.8F/min.
> No ZeroDelta.
> 3-5mv/cell
> Max temperature cutoff??????


 
Thanks!
In my experience, these criteria should not allow heating of the cells to such temperatures. Were the cells you tested healthy? Brand, condition? 
Sorry if I'm asking too many questions, but the replacement of my BC900 depends on that.


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## willchueh (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

The negative delta V cutoff magnitude on the MH-C9000 is 5mV. Industry standard is 7mV. The unit has a resolution better than 1mV, which cannot be said for most chargers out there. 

NiOOH, 

The interesting thing is that certain older/low quality/degraded cells do not produce sufficient negative delta V. We connect a data acqusition system to the cells that is synchronized with the charger to measure offline voltage. In cells that fail to terminate, we see the negative delta V is typically 1mV. 

William


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## willchueh (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> To me, the main question now is how much heat is generated by the charger itself, and how much is generated inside the cells. Also, what is the end of charge temperature at different charging currents.



We did a test where the cells are connected "externally" to the charger (actually using a dummy MH-C808M unit). This effectively eliminates any heat produced by the charger. We find that the cells are cooler significantly. Keep in mind that this test effectively disables temperature monitoring.

You can perform similar testing by comparing temperature of one cell vs. four cells. One cell will run significantly cooler. Even two cells (at slot 1 and 4) run significantly cooler than four cells. 

William


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> We did a test where the cells are connected "externally" to the charger (actually using a dummy MH-C808M unit). This effectively eliminates any heat produced by the charger. We find that the cells are cooler significantly. Keep in mind that this test effectively disables temperature monitoring.
> 
> You can perform similar testing by comparing temperature of one cell vs. four cells. One cell will run significantly cooler. Even two cells (at slot 1 and 4) run significantly cooler than four cells.
> 
> William


 
Thank you William.  
Can you please post some test results for end of charge temperature of the cells you have tested at the usual charging currents between 0.5-1C


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## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Please see the following resource for temperatures during charging:

http://www.duracell.com/oem/Pdf/others/nimh_6.pdf

Third physical page, second chart (6.1.2)


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Thanks!
> In my experience, these criteria should not allow heating of the cells to such temperatures. Were the cells you tested healthy? Brand, condition?
> Sorry if I'm asking too many questions, but the replacement of my BC900 depends on that.


Yes, cells in good shape, not too many cycles on them.


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Please see the following resource for temperatures during charging:
> 
> http://www.duracell.com/oem/Pdf/others/nimh_6.pdf
> 
> Third physical page, second chart (6.1.2)


 
Yes, I have this document. 140F is way too hot, this is all I can say, as I have already done above. dT/dt of 1Celsius/minute should be reached around 120F mark at 1C charging current, providing that the charger does not heat the cells additionally. From my experience if you heat up your cells to even 130F at the end of every charge, do not expect more than 100 cycles before capacity decreases significantly and internal resistance gets high.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Please see the following resource for temperatures during charging:
> 
> http://www.duracell.com/oem/Pdf/others/nimh_6.pdf
> 
> Third physical page, second chart (6.1.2)


It shows [email protected]@100%. I wonder how old this ducument is? I bet this doesn't hold true for higher capacity cells. I've had this same paper for at least a year.

Would I'd like to know is if the C9000 missed termination, how much damage does a cell suffer with +120F temperature for numerous hours?


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## NiOOH (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

You can find similar charts on the sites of several cell manufacturers. Sanyo and GP also have them. These are more or less schematic. 

Apparently this does not hold true for the charger in question.
The chart shows you that with -dV of 10 mV per cell at 1C the end of charge temperature is a bit below 125F.

C9000 uses dT/dt backed by 5 mV per cell. Both shoud terminate sooner than -dv of 10 mV/cell, yet the temperatures reported so far are higher.
Eighter the termination algorhytms of the c9000 do not perform up to specs or the charger itself produces a significant amount of heat, that is not efficiently dissipated. As indicated by William it is rather the latter.
I've used a charger with dT/dt termination at 2 A that kept various cells (1600-2500 mAh Sanyos) around 115-120F at the end of charge. 0dv chargers run a bit hotter than that at the same curent, and -dV ones hotter still


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## SilverFox (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello EngrPaul,

Keep in mind the conditions that graph represents. They are charging at 1 C and terminating with a negative delta V value of 10 mV. I would also guess that those results were not obtained with their high capacity cells.

I can duplicate those results by charging 1800-2200 mAh cells on my Schulze and using a NiCd charging algorithm. If I do the same thing with 2500 mAh cells, they get hotter under the same charging conditions.

Tom


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## AndyTiedye (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I had read somewhere when NiMH batteries first came out that they wanted ZERO dv.
Is that true for some of them?


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## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Andy,

That PDF makes mention of 0 dV/dt.


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## wptski (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Andy,
> 
> That PDF makes mention of 0 dV/dt.


It mentions all forms of termination and charging methods.


----------



## SilverFox (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Just to make sure that we are all reading the same document from Duracell...

At a 1 C charge rate, they are recommending a temperature rise termination of 1.8 F per minute and a back up temperature cut off at EDIT:160 F is not correct, it should be 140 F. ENDEDIT:

They go on to suggest that the temperature criteria may be useful all the way down to 0.5 C charge rate, however it is not recommended for 0.5 C to 0.3 C charge rates. At the lower rates, a negative delta voltage is preferred.

It is not recommended to charge in the 0.3 C to 0.1 C range, and charging at 0.1 C and below is timer controlled as far as termination goes.

Duracell goes on to recommend a 3 step charge method. Charge at 1.0 C to a temperature termination of 1.8 F rise per minute (or until the cell reaches EDIT:160 F is not correct, it should be 140 F ENDEDIT. Follow this by a 0.1 C top off charge for 30 minutes. Then apply a 0.003 C trickle charge until you need to use the cell.

There is also a reference in the 1.0 C charge information that this is for constant current charging. I am not sure what happens when we use pulse chargers...

From all of these recommendations, it seems that cells that don't terminate properly, yet don't exceed EDIT:160 F is not correct, it should be 140 F ENDEDIT: will continue to charge as we have seen. I would imagine that sooner or later the temperature would rise and the EDIT:160 F is not correct, it should be 140 F ENDEDIT: maximum temperature would shut things off.

Did I miss anything?

Tom

Edit notes. I got mixed up with the temperatures. Thanks Mike for catching that. The document states 60 C (140 F) and I transposed the numbers. It should read a temperature maximum of 140 F.


----------



## Mike abcd (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

The cutoff in the doc is 60 deg C / 140 deg F. I suspect you mixed up the "C and F". It's a backup termination only and should not be reached unless the primary method fails. If the cut off is hit while using dT/dt as the primary method (ie it failed), the top off should not be done. Although the document doesn't explicitly state that I think it's a reasonable assumption as no top off is advised for -dV/dt.

I don't think you can automatically assume every cell will hit 140 deg F at 1C although it seems likely. It may be to prevent cell leakage/bursting, etc.. Ambient temps definitely play a big role in cell temperatures.

Mike


----------



## SilverFox (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Thanks for catching the temperature correction. I have edited my post to reflect the change.

The reason I summarized the information is that we are seeing cells that are not terminated during the charge cycle, yet are not reaching the maximum temperature. Since a temperature increase is an indication of over charging, does this mean that the cells are not being overcharged?

Perhaps the charger is OK and there is something different about the cells...

Tom


----------



## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I haven't had any more termination problems, despite continuing to use a 0.7C charge.

If I have termination problems with a battery, I will indicated it with a " * " on the following thread where I am posting my capacity results:

https://www.candlepowerforums.com/threads/146927


----------



## SilverFox (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Woops, double...


----------



## dekelsey61 (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Paul,
What would you say caused your termination problems? I have some 2700Mah+2500Mah batteries. In the Refresh mode what would you set the CHARGE Ma at on those batteries? I am also looking to keep the heat down on the batteries also and I know the higher the charge rate the more heat is produced. Thank you for your reply.
Dan




EngrPaul said:


> I haven't had any more termination problems, despite continuing to use a 0.7C charge.
> 
> If I have termination problems with a battery, I will indicated it with a " * " on the following thread where I am posting my capacity results:
> 
> https://www.candlepowerforums.com/threads/146927


----------



## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Hi Paul,
> What would you say caused your termination problems?
> Dan


 
These were older, used batteries. Probably near the end of their life, just like William said. Until I have problems with newer batteries, this is what I will assume.



dekelsey61 said:


> Hi Paul,
> In the Refresh mode what would you set the CHARGE Ma at on those batteries?
> Dan


 
I have been using 0.7 times the capacity of the battery.


----------



## dekelsey61 (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Thank you for your reply!! How is the heat factor at 0.7c? Thanks for your help.


EngrPaul said:


> These were older, used batteries. Probably near the end of their life, just like William said. Until I have problems with newer batteries, this is what I will assume.
> 
> 
> 
> I have been using 0.7 times the capacity of the battery.


----------



## EngrPaul (Jan 2, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Thank you for your reply!! How is the heat factor at 0.7c? Thanks for your help.


 
The highest temperature I've seen so far has been 125-130. This is when I'm around at the end of the cycle and get the chance to wave the IR thermometer at it.


----------



## NiOOH (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> The highest temperature I've seen so far has been 125-130. This is when I'm around at the end of the cycle and get the chance to wave the IR thermometer at it.


 
What cells and charging current?


----------



## SilverFox (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

OK, I have finally been able to get some cells to heat up...

A while ago I purchased some Powerex 2500 mAh cells. I put 4 of them away for testing and reported their results in the NiMh Shoot Out thread. These reference cells have been set aside and are not in general use. Once a month I put them in the C808M charger and do a normal condition cycle on them. In this mode, they are charged at 2.0 amps.

It was time for a condition cycle, so I put them in the C9000, discharged them, let them rest, then charged them at 2.0 amps. 

Until this charge, I have seen temperatures below 130 F, and I initially thought something was wrong with my temperature probe. I have been in communication with several others that have been seeing higher temperatures, and have been trying to figure out why I was not seeing them.

All 4 cells terminated, but the temperature was at least 158 F. If you look at the cell in slot 1, you can see the heat shrink splitting. I was monitoring the cell in slot 2 for my temperature readings. The other 3 cells also show heat shrink splitting, but the cell in slot 1 is the most pronounced.







I am doing a discharge to see what I get. The voltage at termination was around 1.48 volts.

Not quite a melt down, but I will now join the bandwagon and say that there appears to be some malfunction with the temperature termination and it seems that the temperature cut off is set too high.

Tom


----------



## Mike abcd (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> ...
> 
> Not quite a melt down, but I will now join the bandwagon and say that there appears to be some malfunction with the temperature termination and it seems that the temperature cut off is set too high.
> 
> Tom



It's not just the backoff temperature termination being set too high IMHO. That should not even come into play unless both the dT/dt and -dV/dt terminations fail to operate correctly.

I think you'll find the highest temps in slots 2 and 3 even though your cell 1 showed the most physical damage.

Mike


----------



## EngrPaul (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

H/S, Tom! Do you have a fire extinguisher?

I use an Extech IR thermometer to scan my battery temperatures. 

I'm charging some Sanyo 2700's at 2000 mA today... I hope when I get home the wrappers are intact!


----------



## moldyoldy (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I have not posted on this subject for a couple days - doing testing of my single C9000. 

I am sorry to discover that the C9000 problems with charge cutoff detection did not go away even with a full C9000 "Break-In" cycle on all previously affected cells! 

It could be argued that the Sony cells need more "break-in". I disagree. The 2700mah Sony cells have now gone thru over 6 cycles including a full "break-in" cycle on the C9000 with no detectable change in charge cutoff failures from the C9000. Typically 3 of 4 cells fail the charge cutoff sensing. I have had charge cutoff failures even at a 1500ma rate, although I am primarily using a 500ma charge rate since I don't want to destroy the cells when the charge cutoff is missed.

Before thoughts arise regarding .5C and even 1C being the proper charge rates, consider this: These same Sony 2700mah and 2500mah cells are properly sensed 100% for a charge cutoff on : 
- the Sony BCG-34HRMF @ 525ma charge rate for 4 AA cells; 
- the LaCrosse BC-900 @ 500ma and even _200ma_ charge rates ! ! 
- the Maha 800S on Soft charge @ 500ma for AA cells. 

For that matter, the Sony BCG charger properly sensed the charge cutoff on these same Sony cells even for the very first charge. IOW, the _charge rate_ does NOT seem to be the problem! All of my other chargers did in fact correctly charge these Sony hi-capacity cells even at supposedly "low" charge currents! 

In my biased opinion based on the evidence that I have from my own testing, the algorithm or sensing for the C9000 charge cutoff is faulty. Whatever it is, it is not the same as in the prior successful Maha chargers. There may also be some electrical characteristic of the Sony or other high capacity cells that interacts with some portion of the C9000 algorithm for charge cutoff. All unknown.

... and judging from the "heating" reports with higher-capacity cells, (mine included), it looks like the temp cutoff needs to be adjusted as well! In my testing, when charge cutoff was correctly sensed, the cells were running hotter than in my Maha 800S or 801D.

To be fair, nearly all of the Powerex 2700mah cells and all of the LaCrosse cells (lower capacity) are properly sensed for charge cutoff in the C9000. 

Tim


----------



## wptski (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Okay, here’s more graphs galore for you!

Duracell 2.3Ah, discharged first and charged at 1200ma.. I used a Fluke 54-II dual input temperature meter, Fluke 199C Scopemeter with a 80PK adapter and a Fluke 189 logging DMM. All using the standard bead K-Type probe wound several times around the cells with the measuring bead in conatct as best I could. The only one that has a adjustable offset is the 54-II, so I connected at room temperature and had to bring it down 1.8F to match the other two. The IR imager was about 2.5-3F above them early on but as the temperature got higher, it was more like 5F higher.

EDIT: Added Dt/dt(1.8F/min) time from start, collected from numeric data points for Slots#2,3 and 4. Slot#1 was calculated from scope software well zooming in

Slot#1 = [email protected] min, Dt/dt = 130 min
Slot#2 = [email protected] min, Dt/dt = 126 min
Slot#3 = [email protected] min, Dt/dt = 130 min
Slot#4 = [email protected] min, Dt/dt = 129 min


Slot#1, Fluke 199C







Slot#2, Fluke 189





Slot#3/4, Fluke 54-II





IR image when the last cell was DONE in Slot#4






IR image three hours after the last cell was DONE in Slot#4


----------



## moldyoldy (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Well whaddya know, the Sony 2500mah AA cells finally had one cycle where all of 4 cells terminated a charge correctly in the C9000 charger! ...and that only after between 10 and 15 discharge/charge cycles in my L2Ts and a couple more cycles in the Sony charger on "Refresh". 

and all this time these cells would terminate a charge correctly in _any_ other charger that I have, and at charge currents from 200ma to 500ma! Not in the Maha C9000! 

Maybe after another half-dozen discharge/charge cycles with the Sony 2700mah AA cells, the C9000 will start completing the charge correctly. Ugh! not what I was expecting from this purchase! 

This is certainly a very inauspicious beginning for a charger from a designer/manufacturer with a generally good history in prior chargers. Eventually Maha will correct the bugs, but ...... 

Tim


----------



## ARTofAWD (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Well I've been playing with my charger since I received it on Friday. So far I've only charged 'cheap' cell without much success.


Of 4 iPower 2100 cells, one won't charge at all as the charger won't even see it, yet I have no problem charging it in other chargers. The second cell never terminates !! On three occasions regardless of charging current it keeps cooking, so much so that the wrapper is bubbled, on two occasions I've put in 7C (15Amps). The other two cells do charge and report about 1530mah capacity (pretty poor).

I've also tried 4 Lenmars 2450 cells. All terminate properly but capacties are between 1600 and 1950. This is even after 1 break-in, and 1 refresh/analyze with a charge rate of 1.0A.

My questions are:
1) why would they let a battery even exceed 2C far less my 7C when I pulled the battery.
2) why would they let the battery get so hot it would bubble the wrapper.
3) why wouldn't it allow me to charge a battery without giving an error such as high impediance etc. 

This charger knows how long it's been charging, it knows how much current it's put out and it knows the battery temperature. Even dumb 'timed' chargers at aleast try to charge a cell and also know when to give up. This thing has the potential to do so much more. I hope Maha will help us 'early adopters' and upgrade the unit when new firmware is available.

PS. I too hear the unit 'squeaking' during charging, but this too me isn't a problem.


----------



## SilverFox (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just ran another 2 amp charge on the Powerex 2500 mAh cells...

All 4 terminated, but the termination temperature this time was 159.3 F.

Still too hot, but the problem is repeatable...

Tom


----------



## dekelsey61 (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Tom,
How are you repeating the overheating of the cells. If you charged the cells at 1 amp would this heat happen? In your past posts you mentioned you had no problem with heat. What have you done different? Thank you.
Dan




SilverFox said:


> I just ran another 2 amp charge on the Powerex 2500 mAh cells...
> 
> All 4 terminated, but the termination temperature this time was 159.3 F.
> 
> ...


----------



## wptski (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> I just ran another 2 amp charge on the Powerex 2500 mAh cells...
> 
> All 4 terminated, but the termination temperature this time was 159.3 F.
> 
> ...


Tom:

How was the input capacity and time?


----------



## SilverFox (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Dan,

I am charging different cells than I was before.

I will have to check a 1 amp charge.

Tom


----------



## SilverFox (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

Input was around 2550 mAh in roughly 86 minutes. In an hour the cell cooled down to 89 F.

Tom


----------



## ProofTech (Jan 3, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Perhaps a little thermal grease between each thermistor and the little metal strips that they touch would help with these overheating problems.


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just did a test only charging 2 Duracell 2300 AA in slots 1 and 4. They were previously discharged in the C-9000 at 1000 mA and sat for several hours out of the charger. Room temp was about 70 deg F. Temps measured with an IR thermometer.

It was better but not quite as good as I hoped.

Time Temp V
15 96 1.41
...
60 100 1.44
65 103 1.45
70 108 1.48
72 112 1.48
74 120 1.48
76 128 1.48
Both done at 77 min, temp=132
Charge input 2283/2310, a previous C-9000 discharge test @ 1000 mA was 1987/1959.

Voltages dropped to 1.44 V right after charge completion and 1.42 V after a few minutes. An hour later, they were at 1.44/1.43 and after 75 minutes 1.44/1.44. So it looks like it terminated on dT/dt and was doing a top off charge. I've seen it do a top off with 4 x AAA @ 900 mA but never with 4 x AA @ 1000 or 2000 mA.

Based on the temps I measured, the charge probably should have terminated around 70 minutes when cell temp had climbed 5 deg in 2 minutes. After 70 minutes cell temp seemed to keep climbing at 4 deg / min or about twice the spec for 1C charging.

The charger area under the cells stayed a lot cooler than with running 4 x AA @ 2000 mA. I got 115 deg aiming between slots 1/2 and 3/4 then but with 2 cells in 1/4, saw only 95 deg.

The cells would have stayed a lot cooler with termination at 70 minutes where it looks like it should have happened, roughly 108 deg vs 132! The extra 7 minutes works out to ~200 "extra" mAH put in. Given the late termination, I would have preferred not to see the top off charge.

I suspect the charger will do better with an external fan cooling it as it should get a little more air flow through the vents . Dremmeling out the slots or adding holes would probably help a lot but I'm not going there based on where things stand. The only fan I have handy is an old ~12" desk fan and a bit noisy so I haven't decided whether to try it. Any volunteers?

Ive got a meter (Radio Shack-22-812) that can take a thermocouple (type k?) with a 1 mV per deg C or F output but they don't seem to carry the probe. I'm not sure where I can find one locally and catching and logging the temp rise near the end of the charge is getting old fast after doing it a bunch of times.

Mike


----------



## NiOOH (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hmmm...
This is too bad. 
Thank you guys for all the data.

It looks like the c9000 does have termination problems, and I wonder why? dT/dt could be missed if there is no good thermal contact between the probe and the cell, but what happens with the voltage termination backup? Could it be that electronic hash from charger electronics makes voltage readings too noisy for the small voltage dip to be seen?
I hope that the engineers at Maha will solve that and solve it soon.


----------



## tacoal (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

It seems if the C9000 used same cover material as BC-900, the melting down would happen already, disappointing.


----------



## Curious_character (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I wonder if there's a QC problem or a design problem that causes trouble only on some units. I've had mine in nearly constant use since I got it nearly a week ago. I've been doing mostly refresh/analyze, on AA cells from 1300 to 2500 mAh, and AAA cells of 700 - 900 mAh. They're in various states of having been used and stored. I haven't caught it missing termination, and the cells (usually being charged at 1A for AA, 400 mA for AAA) are much cooler at termination than with several other chargers I have that take a comparable time. It seems to be doing just what it's intended to do.

It sounds from some of the postings that ambient temperature might be a factor -- the room where I've been using it is at a fairly constant 65 degrees F.

I've got a fair selection of cell brands and capacities -- if someone has a repeatable set of conditions that causes a problem I'd be glad to try to duplicate it here.

c_c


----------



## Handlobraesing (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Looks like I'm gonna hold off the purchase for a while.


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Hmmm...
> This is too bad.
> Thank you guys for all the data.
> 
> ...


The C9000 doesn't use dT/dt termination, if it did, it would have to be for primary termination because dT/dt occurs first then ZeroDeltaV and lastly -DeltaV


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> I just did a test only charging 2 Duracell 2300 AA in slots 1 and 4. They were previously discharged in the C-9000 at 1000 mA and sat for several hours out of the charger. Room temp was about 70 deg F. Temps measured with an IR thermometer.
> 
> It was better but not quite as good as I hoped.
> 
> ...


Does it have a banana input or small, thin polarized blade? Fluke makes both, I have both too. Any place that sells Fluke stuff like Grainger might have it. I don't have the time right now to dig up a number for you.


----------



## NiOOH (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Mike.
Thanks for the info. Indeed, it looks like the dT/dt does not work properly. 132F is just outside the specified maximum end-of-charge temperature (131F) by most manufacturers. Although, it wouldn't cause venting or even deformation of the wraps, repeated charging to such high temperatures will cause greatly reduced cycle life. 
That's a shame because otherwize the C9000 looked like a great charger.
Either some of the units just sold are deffective, or it's a design flaw.
Have you guys contacted Maha on that? It'd be interesting to hear what they think.
Meanwhile, I will hold my purchase untill the exact problem is identified and hopefully solved.


----------



## summerwind (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

you guys have nailed something that's beyond me, so my question is this, would i be best off returning this charger and waiting for an updated version?


----------



## RobSpook (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



summerwind said:


> you guys have nailed something that's beyond me, so my question is this, would i be best off returning this charger and waiting for an updated version?



Personally, I am going to continue using it to charge and refresh/analyize all my batteries and will send it to Maha if/when they decide to fix them. Personally, I haven't had any issues, and I don't plan on using any charge rate higher than 1300 ma (and thats ONLY for Energizer 2500's if they ever send me the coupons they're supposed to.)

Rob


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello ProofTech,

I have not opened up my unit to see how contact is made. I did that exact thing with my BC-900. I may have to have a look...

Tom


----------



## EngrPaul (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I'm going to continue being an early production adopter/evaluator, as long as there continues to be no safety issues.

So far I've only had two cells not terminating, the rest have been fine.

Plus, I'm continuing to get fantastic support from MAHA (William).


----------



## moldyoldy (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

FWIW, some of my experiences with the C9000 are mirrored by comments in the two threads on CPF about the C9000 issues. I notice charge cutoff issues primarily with the higher-capacity cells, in particular, the 2700mah cells. The cells also get much hotter even at the 500ma to 1000 ma charge rates than with my other Maha chargers. 

For now, I am debating continuing testing with the C9000 charger. However I will always restrict charge rates to no more than 1000ma, and preferably 500ma. I spent too much money on my hi-cap cells to repeatedly cook them with charge cutoff failures in testing out a new charger. I am thinking about returning it, but am waiting for Maha itself to take a position. I won't wait long.

IOW, I also am looking for at least a Maha statement about the problems observed in using this charger. There are simply too many problems observed by too many very capable CPF members with documented test data to ignore! If Maha offers no statement or even a return/repair offer soon, then the C9000 will be returned.

Tim


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Are you sure your charge ended on change in temperature? Perhaps we can get Bill to expand the scale on his temperature plots to show only the time when the temperature rise was in the 1.8 F / minute range.

Bill, can you rescale your temperature plots in post 166 with an X scale of 1.5 - 2.5 hours and a Y scale of 100 - 140 F ? This would allow us to zoom in on the area where the temperature rise occurred and see if it follows delta temperature termination.

Tom


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Tacoal,

The temperatures involved with the BC-900 melt downs were a lot hotter than what we are seeing with the C9000. The shrink wrap distorts at around 155 F, and the plastic starts to melt at around 185 F. We have another 30 degrees to go before we see any charger melt downs.

Tom


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Curious Character,

I am not sure what is going on. Like you, I have used the charger to charge a wide variety of AA and AAA cells without problems. My AA charging has been done at 2 amps and my AAA charging at 1 amp. The temperatures were all below 130 F.

Then this happens...

I believe my "problem" cells are terminating on negative delta V and not on temperature when charging at 2 amps. I am also confused by the malfunction of the high temperature cut off. I am making sure to insure proper contact with the thermal strip at the negative end of the charger.

For now I can only suggest monitoring the cell temperature during charging. If the temperature gets hot, stop the charge manually and make a note to charge at a lower charge rate next time.

Tom


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello NiOOH,

William and I have been in fairly constant communication. Maha is replacing my cells, and trying to figure out what is going on with the charger. They have been very supportive.

I have a few more tests to run after which I will suggest to William that I send him my charger and problem cells so they can study the problem first hand.

Tom


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

I'm at work right now and have a appointment tonight to keep too, so maybe tomorrow.. Yes, I can zoom in and also the software shows a list of numeric data points. That's for Slots#2,3 and 4 only.

NiOOH:

Are you confusing dT/dt termination and maximum temperature safety cutoff? The safety cutoff isn't a rate per minute, it's just a single value.


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Summerwind,

I have had a lot of success and one failure with this charger. I believe in forming charges and think you will get better performance and longer life if you take the time to do a forming charge.

This charger makes the forming charge automatic. I think it is worth keeping just for that feature. I think it will pay for itself with just this feature, by keeping your cells healthy longer. If you do a forming charge every 20 - 30 cycles, or once a year, you may find yourself replacing your cells out of curiosity, rather than need.

This charger seems to do well at its default setting of 1 amp. I think you are probably fine at this charge rate, but you need to keep an eye on the charging process. Fortunately this charger gives you enough information to keep track of what is going on and it doesn't hurt to touch the cells from time to time to see if they are only warm, or if they are getting hot. If you are charging 2000 mAh cells and notice that the charger has put in 3000 mAh and is still charging, you should pull the cell and stop the charge manually. At least this charger gives you information to determine what is going on. 

The discharge function seems to work fine, although we are not sure why the discharge current seems to taper off near the end of the cycle. The results seem in line with what we expect.

I am planning on keeping mine, but will monitor cell temperature and the amount of time the charge has been running. 

Now, if we could persuade William to include temperature as one of the items listed on the read out...

Tom


----------



## NiOOH (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> Are you sure your charge ended on change in temperature? Perhaps we can get Bill to expand the scale on his temperature plots to show only the time when the temperature rise was in the 1.8 F / minute range.
> 
> ...


 
Tom. I downloaded one of Bill's graphs and lookedf at it zoomed in. At slot number 1 it did terminate at a slope og 1.8 F/min based on the last 3 minutes of charge. I am still puzzled over the fact that the end temperature was 123.3F at 0.5C. It's simply too hot for this charging rate and termination mechanism.


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Summerwind,
> 
> I have had a lot of success and one failure with this charger. I believe in forming charges and think you will get better performance and longer life if you take the time to do a forming charge.
> 
> ...


Tom:

Current tapers off? Where did this come from? I "think" that I have still have a current plot but it's nothing but a straight line till it goes into topoff charge rate.

EDIT: Whoops! I misead or didn't read correctly. That's "discharge" current.


----------



## EngrPaul (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

That question was answered... for a battery with high internal resistance, the offline voltage has not yet dropped to discharge termination at 1.0V, while the online voltage drops below 0.9V, and the charger won't discharge at the desired rate anymore. (I have a wish that they lowered this 0.9V to a lower value).



wptski said:


> Tom:
> 
> Current tapers off? Where did this come from? I "think" that I have still have a current plot but it's nothing but a straight line till it goes into topoff charge rate.


 


EngrPaul said:


> While performing a break-in on 4 batteries simultaneously, several of my cells were already past the discharge, rest, and several hours into charging. Cell "C" took 9.3 hours to discharge. The final capacity was 741


 


willchueh said:


> EngrPaul,
> 
> I think I've a good explanation for you. During both charging and discharging, the voltage is read "offline" which means they are taken with the current off.
> 
> ...


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I tried a charge at 1 amp and got a maximum temperature of 132 F. All 4 cells terminated.

Next is to try a 2 amp charge with two cells in slots 1 and 4.

Tom


----------



## willchueh (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I would like to address the questions regarding dT/dt. 

Some of you have used external temperature probes to monitor the temperature of the batteries. This is NOT the temperature the charger's software sees. Here are the differences:

1) The thermocouples in the charger is in contact with both the batteries and the charger's PCB - both generates heat. External temperature probe does not suffer from this. 

2) Each thermocouple get thermal interference from the nearby cells, since the negative metal contacts act as thermal conduits. 

If we set the dT/dt too sensitive, it will most certainly cause premature termination as seen in other chargers. I wish we are able to measure the temperature as acurately as external probes, but it is simply not possible when the charger has to charge four cells at a time and generate heat that throws the temperature readings off. 

Overall, the charger still uses -dV as the primary detection, temperature is used as secondary given the physical limitation above. 

Regards,

William


----------



## willchueh (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



moldyoldy said:


> There are simply too many problems observed by too many very capable CPF members with documented test data to ignore!



I regret to hear that you feel we are ignoring your concerns. I hope that our active participation in this forum shows that we stand behind our products. 

William


----------



## macdude22 (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I've been hammering this thing with a lot of AA cycles @ 1000 charge/ 700 discharge without any issues yet. Only one I didn'd do that with was a pair of Panasonic 1400s I had that I used a 500 charge/ 500 discharge setting. They cycled out at 1379 and 1382. I've had these things forever, good to see them hold up.


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

willchueh:

What is the temperature cutoff point, however the C9000 is doing it? The BC-900 v33 is able to pause when cell surface temperature is around 130F but the C9000 can't?


----------



## willchueh (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> willchueh:
> 
> What is the temperature cutoff point, however the C9000 is doing it? The BC-900 v33 is able to pause when cell surface temperature is around 130F but the C9000 can't?



Bill, 

The cutoff temperature is dynamic, dependent on the charging rate. When the charger operates at 2.0A, the cutoff temperature is 131F (55 C).

William


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Larry abcd:

The K-type bead probes from Fluke are 80PK-1 with mini-connector and the 80BK with a standard spaced dual banana plug. Grainger has the 80PK-1 has #1T322, a catalog didn't the other but that doesn't mean that they don't carry it!


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Bill,
> 
> The cutoff temperature is dynamic, dependent on the charging rate. When the charger operates at 2.0A, the cutoff temperature is 131F (55 C).
> 
> William


William:

So, from your earlier explanation. The thermistor inside the charger,reading the total temperature would cutoff at 131F, correct? I think that I seen 127F at least hot spot below Slot#1/2 with the thermal imager. My uneducated guess would be that the inside would be warmer. Yes/No?


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*




SilverFox said:


> Hello Mike,
> 
> Are you sure your charge ended on change in temperature? Perhaps we can get Bill to expand the scale on his temperature plots to show only the time when the temperature rise was in the 1.8 F / minute range.
> ...
> Tom



Tom,

I'm reasonably sure that it terminated on dT/dt as the cell voltage rose slowly over the next 1.5+ hours following the large drop when the high charger current stopped. As I stated, I haven't noticed that before when charging 4 x AA, only with 4 x AAA and 2 x AA. The slow voltage rise seems to confirm a top off charge was done. I can't see any other reasonable conclusion.

I assume that the top off charge is only done after it terminates on dT/dt but William hasn't responded to my post where I asked that question. A top off charge shouldn't be applied after -dV/dt termination according to the cell manufacturers.

Mike


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> I tried a charge at 1 amp and got a maximum temperature of 132 F. All 4 cells terminated.
> 
> Next is to try a 2 amp charge with two cells in slots 1 and 4.
> 
> Tom



Tom,

Did it look like it did a top off charge? I see a slow voltage rise of about .02 V over the hour following charge termination on AA and more on AAA (due to their lower capacity) when it does.

Mike


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Tom. I downloaded one of Bill's graphs and lookedf at it zoomed in. At slot number 1 it did terminate at a slope og 1.8 F/min based on the last 3 minutes of charge. I am still puzzled over the fact that the end temperature was 123.3F at 0.5C. It's simply too hot for this charging rate and termination mechanism.



The 1.8 F/min criteria for dT/dt termination is based on a 1C charge rate. At .5C a lower dT/dt value should probably be used.

I suspect that explains the temperature getting higher than you expected.

Mike


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Does anybody have a link to the thread with pictures of the C-9000 internals? I'm having trouble finding it.

I doubt that there's room for an internal fan but I'm curious whether I could dremel slots/holes in the case and use an external fan to cool the internal electronics.

I may be willing to void my warranty to do this but I'm not willing to lose the option of returning it or void the warranty just to see if it looks like it would help.

There's a LOT to like about the C-9000 and I'd hate to give up on it. I suspect a little active cooling of the internals would make a big difference and even opening up the slots or adding additional vents would help.

Mike


----------



## EngrPaul (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike,

A desk fan, or laptop cooler would be less deadly to your warranty...

Here's that link to pictures.

https://www.candlepowerforums.com/threads/146310


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Yes, after the 1 amp charge, it went into a top off charge.

Tom


----------



## NiOOH (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi William,

Great to see that engineers from Maha are taking up our concerns seriously, and even better participating in this forum. Although I'm still to purchase the C9000, I'm glad to hear from you and be here.

About the dT/dt detection, my understanding is that it is used instead of absolute T mainly because of the reason that it ignores external interferences, such as heat generated by the charger. Yes, the charger does contribute to the end of charge temperature, but it should not influence the termination system. I mean, the charger electronics would heat fairly quickly after the begining of the cycle when dT/dt is much less than 1.8F/min and thus not trigger a false termination. 
I've used a dT charger whichg terminated around 120-125F at 2 A charging current.
Also, providing that the c9000 is doing a 2 hours top-off charge, IMO the fast charge could have been terminated more conservatively.


----------



## NiOOH (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Oh, and yet another question. What is the sampling frequency for T and V. 
I mean, we are talking about dT and dV, which strictly speaking call for an infinite sampling rate. Since it is obviously not the case, we should talk about delta T and V respectively, but my keyboard is not easily configured to type Greek charactes.


----------



## moldyoldy (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Quote:
Originally Posted by *moldyoldy*
There are simply too many problems observed by too many very capable CPF members with documented test data to ignore! 



willchueh said:


> I regret to hear that you feel we are ignoring your concerns. I hope that our active participation in this forum shows that we stand behind our products.
> 
> William



Hi William, 

I apologize if my frustration with failed -dv/dT charge cutoff on high capacity cells and with the overheating issues using the C9000 implied that Maha was already ignoring the issues. I meant it as a statement that there were too many reasonably documented issues with the C9000 performance for Maha to ignore. 

My implied reference is to another brand of NiMH charger that from all accounts did not acknowledge that there was at least one significant problem with that charger, although that company did eventually bring out a modified version which appears to correct a major problem.

In any case, your participation on this forum and responding some of the posts is a good indication that Maha is paying attention. I was glad to read that you and SilverFox have been in communication on at least one of the issues surfaced in these forums. I understand if you do not necessarily respond to every issue observed on the C9000 that has been posted here, my own included! I nevertheless am quite interested in how the problems with the C9000 will be corrected.

Thank you for your visible presence in these forums! 

Tim


----------



## Mike abcd (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Mike,
> 
> A desk fan, or laptop cooler would be less deadly to your warranty...
> 
> ...



Thanks for the link Paul. I definitely plan on trying an external fan first. I'm just trying to explore options if that doesn't produce acceptable results.

The cooling slots in the case seem pretty small so I was wondering if it would be easy to get more air into the internals. Looks like it from the pics. Seems like there's a lot of open space on the other side of the existing slots in a few places.

Mike


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> Please see the following resource for temperatures during charging:
> 
> http://www.duracell.com/oem/Pdf/others/nimh_6.pdf
> 
> Third physical page, second chart (6.1.2)


I don't want to appear to be rude but I wish that everybody would read paragraph 6.2.6 in the document above for a explanation of dT/dt termination and temperature backup cutoff.

I'm getting confused by the term of dT/dt being used instead of temperature backup cutoff. If your charging at 1C say, dT/dt occurs first than ZeroDeltaV and then NegDeltaV termination. I guess that the backup cutoff temperature could be a rate per minute but it's usually given as a certain degree like 140F. The BC-900 cuts off at around 130F.

So what are we really talking about here?


----------



## tacoal (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Tacoal,
> 
> The temperatures involved with the BC-900 melt downs were a lot hotter than what we are seeing with the C9000. The shrink wrap distorts at around 155 F, and the plastic starts to melt at around 185 F. We have another 30 degrees to go before we see any charger melt downs.
> 
> Tom


 
Hi Tom,

Thanks for explanation. I supposed they used different plastic.

I just wonder if this is avoidable if an external fan is added, like the way to avoid melting down on BC-900 charging new high capacity batter?


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

I believe some think that the C9000 utilizes delta temperature as a cut off. I don't seem to find a reference to that method of termination on this charger... 

I do know it utilizes a - delta V termination, along with a maximum voltage termination. It is also supposed to have a maximum temperature termination as well.

So, we are talking about how the charger should perform if it utilized change in temperature termination, and if we were all charging at 1C.

Tom


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> I believe some think that the C9000 utilizes delta temperature as a cut off. I don't seem to find a reference to that method of termination on this charger...
> 
> ...


Tom:

I've stated several times that the C9000 doesn't use Dt/dt but the formula was still repeated that was the reason for the post.

T/D has it as Heat Management something.

I still don't know what they are refering to! We'll have to wait for the other users to reply.


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> Are you sure your charge ended on change in temperature? Perhaps we can get Bill to expand the scale on his temperature plots to show only the time when the temperature rise was in the 1.8 F / minute range.
> 
> ...


Tom:

I edited Post #166 without posting more graphs using "time from start". So comparing that, all look good except Slot#4 that went a bit long before terminating but it didn't get overly warm in the process.


----------



## SilverFox (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

OK, now I am confused...

If the C9000 is not using dT/dt, then it would appear that - delta V occurs almost at the same time as dT/dt.

Tom


----------



## EngrPaul (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

If I'm seeing the graphs correctly, there is a significant slope change of temperature around 90% charged, then the slope is rather constant. And this will probably vary from battery to battery, and unintentional changes in ambient conditions (for instance, the activity of a nearby bay, somebody suddenly blowing air across the charger, the sun coming out, etc.). I imagine picking out the right dT/dt for 100% charge would be difficult in practice for a consumer charger.

OTOH, dV/dt seems more reliable (always a swing from + to -), and is easier to detect than a definite magnitude.


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> OK, now I am confused...
> 
> ...


Tom:

Yes, it's pretty close and the temperature is still increasing too, so if it misses -DeltaV, up it goes. Now, past the Dt/dt point, temperature is rising 4-5F/min. Remember this is only at .5C too! I wonder how a graph at 1C compares to .5C?????


----------



## wptski (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



EngrPaul said:


> If I'm seeing the graphs correctly, there is a significant slope change of temperature around 90% charged, then the slope is rather constant. And this will probably vary from battery to battery, and unintentional changes in ambient conditions (for instance, the activity of a nearby bay, somebody suddenly blowing air across the charger, the sun coming out, etc.). I imagine picking out the right dT/dt for 100% charge would be difficult in practice for a consumer charger.
> 
> OTOH, dV/dt seems more reliable (always a swing from + to -), and is easier to detect than a definite magnitude.


Which one are you looking at? The worst one is Slot#1 because it resolution you might call it was 1F or whole numbers but it's ploting many points making it look jumpy. I used the scope input but I could have used it's meter input which might be better which has .1F resolution but this was my first try at logging temperature with a scope.  I was glad to able to get all four slots logging.


----------



## EngrPaul (Jan 4, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I was looking at the Duracell graph... sorry I wasn't specific!


----------



## RobSpook (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Here's just a little addition to this thread... this happened last night:

I put 2 pairs of green "3YD" 650ma AAA batteries that came with and are used in our house phones in the c9000 on R&A, 400/200. All four terminated the initial charge and went into the discharge mode. 1 & 2 took much longer to charge initially because they were totally dead, so their final charges are now up to 2294 and 1390 both at 1.50v for at least two hours and cells are hot. I can put my finger tips on them for about 10 seconds. 3 & 4 started their final charge much earlier and both went up to 3400, one at 1.42v and the other at 1.45v. I pulled them because the voltages were the same at 11:30pm and 4:30am. At 5:00am I reinserted 3 & 4 on the same settings and guess what... they both terminated initial charge and went to discharge. 

I am now going to work and will be back in about six hours to update... To rehash a post I made in another thread, I have R & A'd two sets on AA Eneloops with absolutely no problems whatsoever 

Yes, the 3YD AAA are older batteries, but the strange thing is that they all terminated the initial charge correctly, but not the recharge!

Rob

PS, as I type this cell #2 just went up to 1.51v.


----------



## NiOOH (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> I believe some think that the C9000 utilizes delta temperature as a cut off. I don't seem to find a reference to that method of termination on this charger...
> 
> ...


 
So, the C900 does not use dT/dt (rate of temperature increase) as a termination criterion?! Can someone confirm this?


----------



## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> I believe some think that the C9000 utilizes delta temperature as a cut off. I don't seem to find a reference to that method of termination on this charger...
> 
> ...



Tom,

The TD site stated that it used dT/dt when I purchased it although it seems to have been removed. I am not imagining that. It was the reason I purchased it. The other features were just nice to have in comparison.

William has stated that it uses it but not as a primary method due to limitations in the hardware.

I try to be objective but a number of us are seeing temperatures that are close to or exceed the backup temperature cut off that should only be hit when both dT/dt and -dV/dt cutoff thresholds are not sensed.

I haven't tried monitoring voltages directly but based on the cell manufacturers graphs and obesrved temperature rises it appears that the C-9000 is not even terminating on -dV/dt at the stated threshold reliably with 4 AA cells at higher charge rates.

Then there are the complete failures to terminate. We could blame it on the cells but my BC-900 terminated charge on the same cells...

Mike


----------



## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> So, the C900 does not use dT/dt (rate of temperature increase) as a termination criterion?! Can someone confirm this?



From William C of Maha earlier in this thread (post #198)
https://www.candlepowerforums.com/posts/1770344&postcount=198



willchueh said:


> I would like to address the questions regarding dT/dt.
> 
> Some of you have used external temperature probes to monitor the temperature of the batteries. This is NOT the temperature the charger's software sees. Here are the differences:
> 
> ...



It was also listed as a feature on TD's site when I purchased it.

Mike


----------



## wptski (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> From William C of Maha earlier in this thread (post #198)
> https://www.candlepowerforums.com/posts/1770344&postcount=198
> 
> 
> ...


Mike:

I don't think that Willam Chueh should have used the term Dt/dt in that reply anyway, misuse again as in a later reply said that the cutoff temperature was 131F period, no rate.


----------



## SilverFox (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Update:

I took 2 of my "problem" cells and put them into slots 1 and 4, then charged at 2 amps. Maximum temperature was 127 F and both cells terminated.

Tom


----------



## wptski (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Update:
> 
> I took 2 of my "problem" cells and put them into slots 1 and 4, then charged at 2 amps. Maximum temperature was 127 F and both cells terminated.
> 
> Tom


Tom:

What was their problem before?


----------



## tacoal (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

It seems c9000 has more cases of missing termination of charging than bc900 since this only happsens on bc900 when first charging high capacity battery.

The dT/dt termination should be a complex algorithm since the sensor is not independent with each other. In addition, thermal contact plays a very critical role in applying this. Although the reason(s) of BC900 melting down is not clearly known, I think the thermal contact is one of them.


----------



## SilverFox (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

These were the cells that when charging 4 at a time at 2 amps were heating up to 158 F the first time and 159.3 F the second time. This time I only charged 2 cells and put them into slots 1 and 4. Charged at 2 amps and the temperature maxed out at 127 F.

Tom


----------



## wptski (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> These were the cells that when charging 4 at a time at 2 amps were heating up to 158 F the first time and 159.3 F the second time. This time I only charged 2 cells and put them into slots 1 and 4. Charged at 2 amps and the temperature maxed out at 127 F.
> 
> Tom


Tom:

Well, that's what the manual suggests, if only charging two, use Slots#1/4 and William Chueh stated, more cells, more heat.

What capacity were the cells? I think that I'll redo my Post#166 test on four other 2.3Ah Duracells at 2A this time. Too bad that we can't compare temperature probes! I have some IR images that show four cells, where the two center cells are at 130F but a few degrees warmer towards the positive end near the hot spot under/between them which is 140F. If it's supposed to cutoff at 131F total inside temperature, something is wrong, either my testing procedure is wrong which I have no problem with or the charger has a problem either in design or operation.


----------



## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> I don't think that Willam Chueh should have used the term Dt/dt in that reply anyway, misuse again as in a later reply said that the cutoff temperature was 131F period, no rate.



I respectfully disagree and found William's post completely consistent with a discussion of the issues involved with dT/dt sensing given the C-9000 hardware. Of course both our viewpoints are only that and I hope William chooses to clarify his intent.

In the interim, please take a look at the TD C-9000 "Features" page here.
http://thomas-distributing.com/maha-mh-c9000-battery-charger.php

The sixth bullet item reads
"Negative delta V, peak voltage, dT/dt (temperature rise) and max"

Hopefully this resolves the discussion of whether it was claimed to use dT/dt and we can get back to observations of its actual behavior. As I clearly stated before my purchasing decison was based on its claim of using dT/dt. You can find a comment from me about that in the original pre-ship C-9000 thread.

I trust it's not your intent but you're making me feel like you think I'm bashing the C-9000 and you have to defend it. I assure you I'm trying and hopefully succeeding at being objective. I very much want to like this charger but I find the missed terminations and levels of cell heating disturbing. I'm not willing to simply write off the missed terminations as bad cells as they have useable capacity left and 3 other chargers I have consistently terminate charging on the same cells.

Tom, please don't hestitate to offer constructive criticism now or in the future on my posts and please be direct ie I thing you're wrong about this and here's why.

now back to our regularly scheduled program...and my apologies to all...

Mike


----------



## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Update:
> 
> I took 2 of my "problem" cells and put them into slots 1 and 4, then charged at 2 amps. Maximum temperature was 127 F and both cells terminated.
> 
> Tom



Tom,

Are you using the WM CBA probe? If so, can you post a graph of the temperature rise preferably zoomed in on the last few minutes?

Have you tried your IR probe yet? It would be helpful to see a comparison of their readings. Folks at rcgroups don't seem to trust the CBA probe accuracy and response time but I remember you've calibrated yours.

Your results with 2 vs 4 AA cells are pretty consistent with mine although you seemed to get about 5 degrees higher with 4 cells and 5 degrees lower with 2 cells. I wonder if the CBA probe is being affected by the surrounding air temperature as that would seem to explain this. I saw much lower temperatures (95 vs 115) aiming my IR thermometer at the charger housing between slots 2/3 with 2 vs 4 cells.

Mike


----------



## Curious_character (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Woops. My C-9000, well-behaved until now, just missed the charge termination on a cell. It was a brand-new Eneloop AAA (800 mAh). I had charged the 4 cells in the pack on another charger to save time, since the C-9000 was busy. After some rest, I put them into the C-9000 and discharged at 200 mA -- all showed a bit more than 800 mAh. They rested a couple of hours, then I did a charge at 400 mA. Three of the cells terminated normally at a bit over 800 mAh. The fourth was around 1100 and still charging when I terminated it. It was warm but not as hot as cells normally coming off a fast charger, so I doubt that a temperture limit would have terminated the charge.

c_c


----------



## SilverFox (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Thanks for finding that description specification listed on Thomas Distributing. I thought I had seen something about change in temperature termination, but could not find it anywhere. I was beginning to believe that we had made it up in our discussions.

Yes, I am using the CBA probe. I have noticed that there is a 20-30 second lag and that the probe lacks linearity. Since I am only interested in protecting myself from cell ignition during discharging, I devised a calibration procedure to insure that my CBA would shut down if the cell temperature got too hot.

I tape the probe to the side of a stainless tea kettle with 140 F water inside. I actually start off at 150 F and track the drift down to 130 F. The water temperature is monitored by a lab grade thermometer.

With the tea pot full of 140 F water, I set my probe to read 140 F. The probe is not linear, so it is off at temperatures below and above that, but it is very repeatable. I periodically check the calibration to guard against any drift.

I tape the probe to the cell to get good contact. 

The CBA does not record temperature, so I can not provide a graph.

Tom


----------



## wptski (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Tom,
> 
> Are you using the WM CBA probe? If so, can you post a graph of the temperature rise preferably zoomed in on the last few minutes?
> 
> ...



Okay, it states that it does use dT/dt and max temperature cutoff which William Chueh said was 131F. If it does, then why doesn't work? Why did Silverfox melt the wrapper off a cell at 160F. Why did William Chueh say that the thermistor reads PCB, etc. entire charger temperature and wish that it could read cell surface temperature as we are testing here with thermocouples???? If it can't read cell surface temperature there is no way it can "ever" use dT/dt as a form of termination!!

Look at MAHA's site's specs for the charger:C9000. There no mention of dT/dt at all! Who do you believe, T/D or MAHA??

A MAHA C777PLUS-II has max temperature cutoff and a 13 hour safety timer. It will melt a cell and charge for over 24 hours.


----------



## RobSpook (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Just another note... I am performing an R&A on 4 Energizer AAA 850 mah batteries at 500 Charge and 300 Discharge. As in my previous post with the 3YD batteries, the initial charge is terminating, but the 2nd charge (after discharge) appears to be fluking again. Energiazer #2 and 3 terminated at different times (since they were removed from different devices). #1 and 4 are still charging, up to 1096 at 1.47v and 1311 at 1.48v. The wrapper of the #1 cell has popped off. It was in perfect condition before the cycle... Each battery has only 3 charges on it.

This is strange that with ALL the AAA batteries that fail, the first charge terminates, but the charge after the DISCHARGE does not. Anyone else?


----------



## moldyoldy (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



RobSpook said:


> This is strange that with ALL the AAA batteries that fail, the first charge terminates, but the charge after the DISCHARGE does not. Anyone else?



FWIW, the second charge in the "Refresh" mode is where over half of my many AA charge cutoff failures occur. For some reason the first charge may cutoff correctly and the second charge does not. Furthermore, the cell overtemp indications (fingertips, no instruments) are all signs that the primary -dV/dT cutoff failed, much less questions about whether the overtemp cutoff failed. (no instruments, fingertips not calibrated!) Even when the C9000 terminated the charge, the charge time was all over the map. and, like you, all of my cells that failed in the C9000 functioned properly in Maha 801D, 800S, etc. and w/o excessive heat and w/consistent charge times. 

Tim


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## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> Yes, I am using the CBA probe. I have noticed that there is a 20-30 second lag and that the probe lacks linearity.
> ...
> ...



Tom,

If you haven't tried it, smearing some thermal grease over and around the probe with a thin layer between the probe and the cell might help in getting better readings and reduce the influence of the air around the probe.

Can you compare it to your IR probe? My posted data shows that I observed about 4 deg F per minute dT in the last few minutes before fast charge termination on 2 AA cells @ 2000 mA in slots 2/3.

Mike


----------



## dekelsey61 (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Tom-
I am confussed here also. Most of the heat and missed terminations came when setting the charge rate @2amp. In on of your post you did what I said and set the charge rate at 1amp and said they all terminated with not alot of heat. I used the R/A mode on some 2700Mah batteries and set the charge rate @1200Ma. All terminated and the heat was not alot. Could it be we should use a charge rate at about the 1amp. Would this work or am I wrong with my thinking.
Thank you.
Dan
P.S. If this is a real issue at any charge rate what is maha going to do with all these chargers out there?


----------



## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Okay, it states that it does use dT/dt and max temperature cutoff which William Chueh said was 131F. If it does, then why doesn't work? Why did Silverfox melt the wrapper off a cell at 160F. Why did William Chueh say that the thermistor reads PCB, etc. entire charger temperature and wish that it could read cell surface temperature as we are testing here with thermocouples???? If it can't read cell surface temperature there is no way it can "ever" use dT/dt as a form of termination!!
> 
> Look at MAHA's site's specs for the charger:C9000. There no mention of dT/dt at all! Who do you believe, T/D or MAHA??
> 
> ...



William's post gives specifics on the issues with temperature measurement on the current hardware that makes it "difficult" to do accurate dT/dt termination. The temp sensors "try" to read cell temperature but are also influenced by heating from the electronics and "cross coupling" of heat between the cells.

The Maha Mach 1 "Gamma" charger uses a fan to keep the electronics cool that doesn't move any air across the cells. It terminates very reliably but IMHO is way too agressive in charge termination and significantly under charges cells. (about 20-25% for AA, 30-45% for AAA on two different ones compared to my BC-900) I've put cells fully charged on the BC-900 in it both hot and after allowing them to cool and it terminates fast charge (fan and LED go off) in a few minutes. I'll have to try to do some temperature checks with my IR thermometer but my "finger thermometer" says below 110 F at most from what I remember. BTW, the Lenmar also "knows" whether AA or AAA cells are inserted. I suspect the Maha lacks that capability.

I strongly suspect that dT/dt termination requires a fan to keep the electronics temperature stable and/or isolating the temperature sensors from the heat producing charge circuitry along with steps to reduce "heat coupling" between the cells such as seperate connections between the cell cathodes rather than one cross connect.

Unfortunately all of the above raises costs and/or increases the size of the charger. A fan is also a reliabilty/noise issues. My Lenmar buzzes badly until the fan is running for a while and isn't exactly quiet. The buzzing wasn't there to start with and it doesn't have a ton of hours on it.

I suspect dT/dt termination was part of the C-9000 design goals but cost and design issues crippled it and Maha is backing away from claiming the feature. I wouldn't be surprised if dT/dt disappears from the TD site at some point.

Mike


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## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Is anybody willing to host some jpegs for me? They're really small (~100-300 kB) but I'd prefer somewhere that they'll be around for at least a few months.

I did a test where I monitored cell voltage during a charge to look at dV/dt that I think folks might find interesting. The initial test was with only one AA cell charged at 1000 mA but I plan on repeating it with four cells.

The data requires some explanation and I'd expect questions regarding its validity due to the slow sample rate and how the C-9000 charges so I need to "write it up" first. If some one is willing, I'll send both the pics and write up to them for posting here together. I accept all "liability" though in the event of attacks  I'll try to get to it tomorrow but it may be Sunday before I have time.

Unfortunately I'm pretty sure I can't get valid data at a 2000 mA charge rate although 1000 mA "works" well IMHO. If it proves useful, I can try a bit higher or it might motivate some one else with better equipment to give it a try.

TIA

Mike


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## Mike abcd (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I suspect the missed terminations that have been observed may also be tied to heat issues.

Temperature changes in the electronics can induce drift, particularly in low cost components, that makes accurate measurements tougher. At the same time, the Sanyo data seems to show the dV "hump" used to terminate charge happening later and being much shallower. Seems to be slightly smaller too.

Mike


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## wptski (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Try the Photobucket.com, it's free!


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## summerwind (Jan 5, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

mike,
i have a site that i pay for that allows me to post pictures of any size and amount.......be glad to put them up for you.

-mike




Mike abcd said:


> Is anybody willing to host some jpegs for me? They're really small (~100-300 kB) but I'd prefer somewhere that they'll be around for at least a few months.
> 
> I did a test where I monitored cell voltage during a charge to look at dV/dt that I think folks might find interesting. The initial test was with only one AA cell charged at 1000 mA but I plan on repeating it with four cells.
> 
> ...


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## FsTop (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

www.tinypic.com retains pictures for 6 months after the last time they are accessed - free and easy, with no registration required. It even gives you the code to copy/paste into your post to show the image (the php


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## RobSpook (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



RobSpook said:


> Energiazer #2 and 3 terminated at different times (since they were removed from different devices). #1 and 4 are still charging, up to 1096 at 1.47v and 1311 at 1.48v. The wrapper of the #1 cell has popped off. It was in perfect condition before the cycle... Each battery has only 3 charges on it.
> 
> This is strange that with ALL the AAA batteries that fail, the first charge terminates, but the charge after the DISCHARGE does not. Anyone else?



Pulled #1 and 4 this morning... both had over 4500 mah pumped in, and still at 1.47v and 1.48v respectively. I am starting to regret returning my BC-900 now.


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## NiOOH (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> William's post gives specifics on the issues with temperature measurement on the current hardware that makes it "difficult" to do accurate dT/dt termination. The temp sensors "try" to read cell temperature but are also influenced by heating from the electronics and "cross coupling" of heat between the cells.
> 
> The Maha Mach 1 "Gamma" charger uses a fan to keep the electronics cool that doesn't move any air across the cells. It terminates very reliably but IMHO is way too agressive in charge termination and significantly under charges cells. (about 20-25% for AA, 30-45% for AAA on two different ones compared to my BC-900) I've put cells fully charged on the BC-900 in it both hot and after allowing them to cool and it terminates fast charge (fan and LED go off) in a few minutes. I'll have to try to do some temperature checks with my IR thermometer but my "finger thermometer" says below 110 F at most from what I remember. BTW, the Lenmar also "knows" whether AA or AAA cells are inserted. I suspect the Maha lacks that capability.
> 
> ...


 
Mike.
Lenmar Mach1 Gamma uses different charging algorythm. It is somewhat similar to the constant voltage used for charging LiIon cells. The charging current peaks around the middle of the cycle at 2 Amps. When certain cell voltage (or voltage slope) is reached the charging current is decreased in steps of 400 mA, i.e. 2 A-1.6 A-1.2 A-0.8 A... Thus the charging current is adjusted to the state-of-charge of the cells. If you monitor cells temperature carefully, you will notice that it peaks roughly halfway throughout the cycle at around 100F. At the end of the quick charge the cells are just above room temperature.
Also, I found that Mach1 Gamma does timed top-off charge (forgot the current, but it was above 100 mA). If you leave the cells on the charger for 4-5 hours, the charge completeness is well above 90%.


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## bfg9000 (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> William's post gives specifics on the issues with temperature measurement on the current hardware that makes it "difficult" to do accurate dT/dt termination. The temp sensors "try" to read cell temperature but are also influenced by heating from the electronics and "cross coupling" of heat between the cells...
> 
> I strongly suspect that dT/dt termination requires a fan to keep the electronics temperature stable and/or isolating the temperature sensors from the heat producing charge circuitry along with steps to reduce "heat coupling" between the cells such as seperate connections between the cell cathodes rather than one cross connect.


I didn't have many termination failures until after I placed a fan blowing at the cells, so tried the fan blowing at the *back* of the charger with the same cells (no airflow over them) and they terminated fine at 2A.

Unfortunately some cells do get somewhat warm when using a 2A rate. So this is a pickle: charging at 1A supposedly risks failure to terminate (haven't really had problems) and 2A may cook the cells. Worse, I replaced my previous charger with this because cells came off it at 1.55v, and I've just noticed this one still terminates at 1.53v



. Oh well, at least I am enjoying my new discharge-only capacity tester.


----------



## RobSpook (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I'm glad you're enjoying yours.. I'm not. I'm kinda pissed about it failing to terminate on 10 out of my 12 AAA batteries. Screwey thing is they TERMINATE FINE on the first charge of the R&A cycle... then got to infinity on the recharge. I am going to send it back unless I hear something from MAHA about this... I'm not the only one apparently...


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## wptski (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

For all you people still stuck on this thing about the C9000 using dT/dt termination. Here’s a 2.7Ah Sanyo cell charging at 2A and graph of temperature and voltage. The software won't show both scaled at the same time so I'm showing temperature where the cursors X's are. The cell showed DONE in 61 minutes as the graphs show a voltage drop also. Look at the far right, cursor values, you see a spread of about one minute for 1.8F which occurs about six minutes before it’s DONE.

This is much more accurate than the way I had to do it in my Post#166 above.


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## NiOOH (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Thanks Bill.
Great data that pose few questions.

What was the temperature slope at termination point? Apparently, even if dT/dt is used by the charger it is not working properly. Even worse, your data show that the voltage drop is too big. It has been stated that the c9000 terminates at -dV of 5 mV. From this plot it looks more like 15-20 mV of voltage drop before the termination was activated.
The strange thing is that even with this overcharging the temperature stays quite low. Did you feel the cell after the experiment to confirm that the temperature probe was in good thermal contact with the cell, i.e. did it feel at body temperature? Anyway, the overcharging is confirmed by your voltage data. It is obvious that the c9000 DOES NOT terminate with the -dV value specified by the manufacturer.
Something isn't right with this charger. I hope someone from Maha would explain all this and the chargers will be fixed.

Your data show exactly how the termination methods are ranked in terms of occurance. Look at the point around 55 min where 1.8F/min slope occurs. It happens seconds before peak voltage is reached, which in turn, preceeds the voltage drop by a couple of minutes or so.


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## NiOOH (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

... and a few more questions
Was the cell completely dicharged before the experiment? Did you do a discharge test afterwards to determine the capacity?

BTW, do you have the raw data? If yes, can you PM it to me in a text format. I'll input them into some data analysis software to get some more info.


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## wptski (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> ... and a few more questions
> Was the cell completely dicharged before the experiment? Did you do a discharge test afterwards to determine the capacity?
> 
> BTW, do you have the raw data? If yes, can you PM it to me in a text format. I'll input them into some data analysis software to get some more info.


#1, no
#2, no
#2, no because it's a scope not a logger and there is no raw data.


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## wptski (Jan 6, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> Thanks Bill.
> Great data that pose few questions.
> 
> What was the temperature slope at termination point? Apparently, even if dT/dt is used by the charger it is not working properly. Even worse, your data show that the voltage drop is too big. It has been stated that the c9000 terminates at -dV of 5 mV. From this plot it looks more like 15-20 mV of voltage drop before the termination was activated.
> ...


It was 2.7F/min. The point of this post was to show that it doesn't use dT/dt. True, it doesn't because it's not used. An IR probe agreed with the contact probe. There's no way you could conclude from this graph anything about voltage as it's showing temperature as I explained in the post. The scale has to be changed from temperature to voltage and this is a average reading anyway during graphing. A few millivolts is hard to detect anyway. I have seen it on chargers that charge two cells at a time, so it's twice as much and easier to detect. The C9000 checks the battery voltage during the off time of the pulsed current.

NegDeltaV is overcharging by it's definition, to insure a full charge.


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## NiOOH (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Sorry trying to post some graphs


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## Curious_character (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just ran into two more cells that didn't terminate. They were AAA cells which were fairly old (been in a cordless phone) but had good capacity. They were essentially fully charged at the beginning of the refresh cycle, and terminated ok in a short time when first charged.

I'm going to be hesitant to use a charger that I can't trust not to severely overcharge batteries.

c_c


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## bfg9000 (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Robspook, back here TooManyGizmos wanted an independent channel standalone discharger for less than $60, and this model fits the bill perfectly. While it doesn't have 8 slots, it does actually measure the capacity as it discharges each of its 4 slots to 1.0v.

As a plus, it can also perform a double break-in forming charge sequence flawlessly, and works OK as a charger in a pinch _if_ you have compatible cells and want a complete charge.


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## wptski (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Here's the test form Post#254 shown in the voltage scale and expanded to show the voltage drop. As you can see the voltage is over 1.6V but the shown C9000 cell voltage is much less because it's the actual cell voltage. I'll look into if there is a way for me to show the actual cell voltage accurately! If you look at the cursor values at the right, is shows a drop of 12mv but like I say, it's not accurate because it's not really reading the cell voltage during the off time of the pulse only!


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## NiOOH (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

http://photo-zona.net/index.php?APP_ACTION=IMAGE_EDIT&IMAGE_ID=66016 






Here is a voltage versus time graph of charging an Ansmann 2000 mAh cell at 2 A current with a peak voltage detection charger. The actual discharge capacity of this cell was about 1850 mAh (at 0.2 C discharge rate). The end of charge temperature was 115F.


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## wptski (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Similar to Post#166 these are temperature graphs of four 2.3Ah Duracells again but not the same ones. These were fully discharged cells, charged at 2A this time and in the other post it was at 1.2A. The cells in Slots#2/3 finished first as I expected but the other two were far behind. The other odd thing is that the two that finished first don’t show any point in the temperature rise of 1.8F/min but the other two do did at 4-5 min prior to being DONE! This means that dT/dt is not reliable under all conditions. I assume that differences in the cells are at fault here. I also discharged these cells afterwards at 500ma, close to .2C to check the capacity.

I also used the meter input instead of the scope input on the scope for Slot#1 this time which gives it a better resolution.

Charge/Discharge
Slot#1 = [email protected] min/[email protected] min
Slot#2 = [email protected] min/[email protected] min
Slot#3 = [email protected] min/[email protected] min
Slot#4 = [email protected] min/[email protected] min

Slot#1







Slot#2






Slot#3/4


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## dekelsey61 (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi- I charged up 4 Energizer 2500Mah batteries. When they were finished charging I took them out of my C9000 charger for about 45mins. I then put them back in the charger at a charge rate of 1000Ma to charge. 8 mins. later all 4 batteries were all DONE. What terminated the charge? dT/dt? dv/dt? The batteries were luke warm to the touch. Thank you.
Dan


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## wptski (Jan 7, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Hi- I charged up 4 Energizer 2500Mah batteries. When they were finished charging I took them out of my C9000 charger for about 45mins. I then put them back in the charger at a charge rate of 1000Ma to charge. 8 mins. later all 4 batteries were all DONE. What terminated the charge? dT/dt? dv/dt? The batteries were luke warm to the touch. Thank you.
> Dan


Look at the post before yours. Dt/dt isn't used. What is dv/dt? Never heard of it.


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## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I think the C-9000 is definitely using dT/dt. It just doesn't terminate at the 1 dec C per minute spec for a 1C charge rate.

None of the cell manufacturers advise a top off charge after -dV/dt termination but the C-9000 does one at times. I think that only happens after it terminates on dT/dt. I ceratinly hope they didn't decide to do a top off charge after its specified cut off of 10 mV -dV/dt.

I still haven't had a chance to post the results but I've monitored cell voltage and seen the C-9000 cut off fast charging at 5 and 6 mV and start a top off charge.

Mike


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## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



dekelsey61 said:


> Hi- I charged up 4 Energizer 2500Mah batteries. When they were finished charging I took them out of my C9000 charger for about 45mins. I then put them back in the charger at a charge rate of 1000Ma to charge. 8 mins. later all 4 batteries were all DONE. What terminated the charge? dT/dt? dv/dt? The batteries were luke warm to the touch. Thank you.
> Dan



If the cell voltage dropped rapidly and didn't come back up over the next hour, then it didn't do a top off charge and I'd guess it was -dV/dt.

If it did a top off, I'd guess it was dT/dt.

Unfortunately (IMHO) Maha decided not to show the top off charge in the display or add the additional mAH into the "charge capacity" value.

Mike


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## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike:

In my Post#264 which is at 1C dT/dt never happened on the two center slots "only" but with the same brand/capacity cells it did at .5C. I sure wish that William Chueh would put this use of dT/dt to rest! This issue just goes on and on.

Topoff isn't but 80ma anyway, what's to worry about?

I'd like to know how your able to show 5-6ma drop on something that's measured only on the OFF pulse? I haven't found a accurate way to do that yet.


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## NiOOH (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I might have missed the early part of this discussion, but how long is the off-cycle


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## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> I might have missed the early part of this discussion, but how long is the off-cycle


It wasn't discussed but William Chueh checks the cell voltage on the OFF part of the pulse, so that when it has to be measured/checked. It depends on the charging rate, 2A max rate, at 1A, 50% DC. It was 1980ms for a full cycle, so just figure on that. It isn't but a few milliseconds at 2A. I actually figure at 2A is really 1810ma.


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## SilverFox (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

I am not sure what you think you are seeing, but William has stated that the primary termination method used with the C9000 is negative delta V, with a value of 5 mV.

Next is maximum cell voltage, followed by maximum "charging system" temperature. The "charging system" is defined as cells and charger boards. When the whole system exceeds 131 F, the charger will shut down.

I believe a delta temperature safety cut off is used, but it seems to be applied globally and not at an individual cell level. The temperature sensors monitor both the cell and board temperatures. I would guess that if the average of these two temperatures rises above the cut off temperature, the charger would shut down. There is also the possibility that there is a rate of temperature rise value that, when exceeded, would shut things down as well. 

We do not know what the delta temperature value is, but I don't think it has anything to do with "charge termination." My guess is that it is another safeguard to prevent against any "BC-900 like" melt downs.

The final safety is the timer. The charger will shut down when it reaches 20 Ah.

In order to properly terminate a charge on temperature change, it is recommended to charge at a 1C rate, and you need to monitor the cell temperature separately. The C9000 falls a little short on the 1C charge rate with higher capacity cells, but there is some wiggle room there. It is not set up to monitor individual cell temperature. It measures a combined board and cell temperature. If we use a simple average, I had cells at 158 F and if the board temperature was 102 F, an average of those two would come close to the maximum shut down temperature. If the cells had not terminated on negative delta V, they may have terminated on maximum temperature within a very short time.

I don't believe that this charger terminates the charge based on the cells rate of temperature rise. 

Tom


----------



## NiOOH (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I don't believe that such a sophisticated charger, could have termination problems. I know from experience that cheaper chargers DO terminate on dT/dt without problems. Even cheaper chargers use voltage-based termination reliably (although entering overcharge briefly) with no problems whatsoever at charging rates from 1C to 0.25C.
Why on Earth couldn't C9000 do that.


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> I am not sure what you think you are seeing, but William has stated that the primary termination method used with the C9000 is negative delta V, with a value of 5 mV.
> 
> ...



Tom,

Thanks for the correction that the -dV termination value is 5 mV.

As for the rest, Wow, we're just going in circles.

As I previously posted "dT/dt (temperature rise) is listed as a feature on the TD C-9000 features page.

Then there's William's post
https://www.candlepowerforums.com/posts/1770344&postcount=198

It starts with "I would like to address the questions regarding dT/dt" and goes on to list two issues affecting the ability of the C-9000 hardware to accurately measure temperature.

He then states 

"If we set the dT/dt too sensitive, it will most certainly cause premature termination as seen in other chargers. I wish we are able to measure the temperature as acurately as external probes, but it is simply not possible when the charger has to charge four cells at a time and generate heat that throws the temperature readings off. 

Overall, the charger still uses -dV as the primary detection, temperature is used as secondary given the physical limitation above."

Two explicit references to dT/dt with no statement that it doesn't use it yet you fixate on the word temperature alone in the last sentence and assume it applies only to a max temperature termination. huh?

Then there's the "top off" charge. I can't imagine why it would implement one unless the charger was designed to potentially terminate on dT/dt.

I've measured over 115 deg F on the charger surface directly below slots 2/3 and 3/4 so your "average temp" appears low. I also see no meaning in an average of the cell and electronics temp in light of William's post that directly discusses the issues affecting the C-9000 measurement of individual cell temperatures.

I certainly agree that the observed behavior of the C-9000 doesn't conform to dT/dt termination per the cell manufacturer's specs. However I don't agree that it wasn't designed with the intent of being able to terminate on dT/dt.

If William says I'm wrong, I'll promptly apologize to all here...and return the charger as dT/dt termination support was the primary reason I purchased it. I still hold out some hope that it can do it better with cooling of the charger's electronics or I would have already returned it.

BTW, has anybody considered what is going to happen to C-9000 cell temperatures when summer rolls around and folks start using it in 80 deg F and higher temps vs the 70 deg and lower temps most of us are using it in now? I'm regularly seeing slot 2/3 cell temps of 130 at 1000 mA charge and 140 at 2000 mA when charging 4 AAs.

If you are still in direct contact with William, please ask him for confirmation one way or another. Frankly we're going in circles on this and I'm not going around again without direct info from Maha.

Mike

Mike


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just called Maha support. The tech wasn't sure if it used dT/dt as a termination method but promised to check. He did state that it used individual temperature sensors on each cell.

Mike


----------



## NiOOH (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> I just called Maha support. The tech wasn't sure if it used dT/dt as a termination method but promised to check. He did state that it used individual temperature sensors on each cell.
> 
> Mike


 
I guess they made an attempt to implement dT/dt, quite poorly though.


----------



## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike:

MAHA's posted specs on their site mentions no dT/dt at all. I guess I could post another hundred graphs showing that it doesn't use dT/dt but you'll still believe that it does because T/D had it posted. Hey, give it up!

Post #166 shows a IR image and cell's temperature at both ends. I found using the imager that the area around the metal temperature contact to be 125F that means 6F below the so-called shutoff of 131F. If that cell's temperature was raised another 6F the positive end would be near 160F.


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> In my Post#264 which is at 1C dT/dt never happened on the two center slots "only" but with the same brand/capacity cells it did at .5C. I sure wish that William Chueh would put this use of dT/dt to rest! This issue just goes on and on.
> 
> ...



I think William posted that the top off charge was 100 mA for two hours. 200 mAH of excess charge on an AAA battery with 800 mAH or less of total capacity is a lot in my book.

I'm using a Radio Shack 22-812 meter with a serial interface and PC data logging S/W. It only logs data once per second but appears to have a sample and hold on its front end with a very short aperature time. The data plots look really ugly with samples at the resting voltage, higher voltage during the charging pulse and in between. However at 1000 mA charge, the bulk of the samples appear to be taken during the no current "resting period" due to the low duty cycle.

It's easy to track the upward trend on the lower end of the sawtooth plots @ 1000 mA charge rate. I've done LOTS of spot checks and the lower readings are always within .010 and .015 volts of the Maha voltage display and increase monotonically by the meter's 1 mV resolution (until the voltage flattens and drops at the end of charge) with occasional .001 jitter (1 digit) that is to be expected.

I'm convinced it's showing an accurate picture of the cell voltage during a 1000 mA charge but others may disagree.

I've also tried it at 2000 mA charge rate. Due to the higher duty cycle, it doesn't capture the resting period consistently and shows the voltage under the charge pulse much more often. It appears to still offer useful data in tracking the cell voltage changes IMHO. I'm less certain that it allows accurate tracking of dV in this case but I'm becoming progressively more convinced that it does. As far as I know, the measurement of dV is intended to be done under charge anyway.

I'll try to find time to sign up for a site that will allow me to post the plots and "write up" info on the tests I've done.

The most interesting results so far IMO are 2000 mA charge rate tests done with a single cell and 4 AAs from a discharged state and a single cell from a fully charged state. Both single cell tests showed a clearly defined -dV but the 4 cell test showed the cell voltage rise go to zero but it didn't drop. Both the cell and charger temperature was much higher in the 4 cell test. A wild guess is that the higher temps broadened or reduced the cells -dV "signal" and/or affected the chargers ability to maintain the high charge current.

I'm only willing to have limited discussions on this until folks have seen the data but might try to answer questions in the interim.

Mike


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> MAHA's posted specs on their site mentions no dT/dt at all. I guess I could post another hundred graphs showing that it doesn't use dT/dt but you'll still believe that it does because T/D had it posted. Hey, give it up!
> 
> Post #166 shows a IR image and cell's temperature at both ends. I found using the imager that the area around the metal temperature contact to be 125F that means 6F below the so-called shutoff of 131F. If that cell's temperature was raised another 6F the positive end would be near 160F.



Bill,

Maha's specs don't mention -dV/dt termination either...guess TD just made it up and William chose to discuss dT/dt issues without saying it didn't use it.

Don't worry, I have given up discussing it here. If anybody cares, I have zero doubt it doesn't implement it "correctly". I care because it gives me some hope that the charger could work a LOT better with some cooling of its internals although I'm getting progressively more discouraged from trying.

I wonder if your IR sensor is reading the contact temperature correctly. I'd guess the shiny contacts would have a very low emissivity compared to the cells, etc. Your IR images are stunning. Looks like an amazing and expensive tool/toy. drool... My cheapo IR thermometer seems to agree with your temps pretty closely although I can only get accurate readings at the middle of the cell due to its large spot size.

Mike


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



NiOOH said:


> I guess they made an attempt to implement dT/dt, quite poorly though.



Well put IMHO.

Mike


----------



## 3rdDerivative (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Is any one besides Mike (and me) concerned about the 2 hour 100ma, since the charger seems NOT to use dT/dt?

It seems like poor engineering or sloppy firmware. 

Either way this charger besides the nice readouts, discharge and cycles options is looking nothing special as a charger. In fact, at step backward when used as just a charger. 

The website claims you have over 10K possibilities. I would just have like the more usual 500mah, 1000mah an 2000mah charge cycles to not cook my batteries. 

Forget the other 9,997 options.


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## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



3rdDerivative said:


> Is any one besides Mike (and me) concerned about the 2 hour 100ma, since the charger seems NOT to use dT/dt?
> 
> It seems like poor engineering or sloppy firmware.
> 
> ...



Just when I was beginning to fell very lonely here... Nice to know others share my concerns.

Mike


----------



## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike:

I cover the metal contact with black tape to double check. What you mean that they don't mention -dV/dt?? Look here: C9000 

If your worried about the topoff, just pull it out when it shows DONE.

Here's another point that came up in another thread, somewhere. The C9000 also uses PWM during discharge too. I posted a screen showing some hash during the ON portion of the pulse but I think that it was in the FAQ thread. No hash on the discharge pulses!

Interesting about your metering, it must be tuned just right. I may have come up with a way to look at the voltage drop. My scope saves the last 100 screens for playback. If I catch it just right after DONE shows, I "should" be able to see it. My first attempt failed as I had the timebase set too fast, only catching one pulse per screen, nothing to compare to. I'll try a slower timbase next and hope that it works.


----------



## Mike abcd (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> I cover the metal contact with black tape to double check. What you mean that they don't mention -dV/dt?? Look here: C9000
> 
> ...



Sorry I missed the -dV refernce. Now lets see, how many days before that "timer" terminates the charge assuming it's based on max capacity delivered.

I don't normally watch the charger so pulling them off when it shows done is not a viable option for me.

The black tape you use to get the emissivity into a reasonable range probably serves as an insulator and still causes low readings.

Does your scope have enough resolution to track the volatge peak? Most I've used don't. On a digital scope, it would take at least 11 bits of resolution on a 0-2V range to get 1 mV.

I haven't tried looking at the discharge yet but I'm surprised it doesn't use PWM also. I have noticed the "accumulated" mAH displayed by the C-9000 on both charge and discharge is about 10% less than the mA rate displayed x time.

Mike


----------



## 3rdDerivative (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> If your worried about the topoff, just pull it out when it shows DONE.



Almost as useful as suggesting:

And if you are worried about overheating your batteries, just put your charger in the freezer too.


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## willchueh (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

PWM is used to regulate the discharge current. However, it does not involve an inductor (used for voltage stepdown in charging) therefore the scope will appear different. 

As for observed discharge current vs. the display:

The charger pauses for 10% of the time to measure voltage, etc per duty cycle. The current shown on the screen is the full current. Therefore the actual current is x0.90. If you charge for one hour at 1000mA, it will result in aprox. 900mAh accumulated capacity. 

William


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## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> PWM is used to regulate the discharge current. However, it does not involve an inductor (used for voltage stepdown in charging) therefore the scope will appear different.
> 
> As for observed discharge current vs. the display:
> 
> ...


William:

In an earlier post you stated that the C9000 measured the cell voltage on the OFF pulse. That would be a different amount of time or depending on the charging rate, not 10% all the time.


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## wptski (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Sorry I missed the -dV refernce. Now lets see, how many days before that "timer" terminates the charge assuming it's based on max capacity delivered.
> 
> I don't normally watch the charger so pulling them off when it shows done is not a viable option for me.
> 
> ...


Mike:

Using black tape tape is the suggested way or painting the object black.

I think the scope has the specs but since it's PWM presents a special problem. It must measure or show the battery voltage not the charging voltage.


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## willchueh (Jan 9, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> William:
> 
> In an earlier post you stated that the C9000 measured the cell voltage on the OFF pulse. That would be a different amount of time or depending on the charging rate, not 10% all the time.



Bill,

The OFF time is 10% of one single charge cycle. The off time is constant regardless of charging current. 

William


----------



## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



willchueh said:


> Bill,
> 
> The OFF time is 10% of one single charge cycle. The off time is constant regardless of charging current.
> 
> William


William:

Okay, now you really have me confused! If this charger's max output current is roughly 2A and your charging rate is set to 1A, your duty cycle is 50% ON, 50% OFF. I can capture some waveforms later and post them.


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## bob_ninja (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I have to agree with Mike.
The main features that I am looking for are both dT/dt protection as well as max temperature limit for ANY CELL. Now I understand and accept the challanges of measuring these values for each battery. If accuracy is as poor as +/- 10% or even 15% then I would be fine with that. The charger must have these protections against not just meltdowns but also overheating batteries to the point where internal and external structures might be compromised. Our individual definitions of what is "warm" or "hot" are irrelevant. I care about which temperature limit can an average NiMH AA battery handle.

That being said, I expect -dV/dt signal to be detected at least as reliably as most existing chargers do. Also I'd want a protection against putting in more than 2C into a cell, which again none my current chargers do.

The bottom line is while it can allow for more aggresive use (such as 1C or 2C charge rate) it should still be able to handle them safely without causing too much damage to cells.

All this may be rather demanding requirements. I just don't see much improvement over BC-900 otherwise. Why switch?


----------



## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

The dT/dt form of termination isn't reliable under certain conditions.


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## Handlobraesing (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

My Duracell 15 minute(8.5A?) and 30 minute (3.4A) chargers stops charging every few seconds for some few tens of miliseconds, then measures the cell voltage throughout the charging cycle. 

Also, it measures the cell impedance before beginning and would only allow charging if the impedance is low enough to safely charge at this rate.


----------



## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Handlobraesing said:


> My Duracell 15 minute(8.5A?) and 30 minute (3.4A) chargers stops charging every few seconds for some few tens of miliseconds, then measures the cell voltage throughout the charging cycle.
> 
> Also, it measures the cell impedance before beginning and would only allow charging if the impedance is low enough to safely charge at this rate.


A D-15 is another PWM charger like the C9000 and "probably" works the same, checks cell voltage during the OFF pulse too. Unless you have some inside information that may be true or not, post a graph showing what, where and how. I'm not saying that I know how either works fully but these C9000 threads are riddled with false statements and guesswork about how it's supposed to work, does or doesn't!


----------



## Mike abcd (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> The dT/dt form of termination isn't reliable under certain conditions.



Bill,

Can you please educate us and tell us what those conditions are?

I certainly appreciate that measuring dT/dt accurately is a design challenge in a low cost charger. I also think that even chargers designed to use dT/dt should have -dV, max temp, max voltage, etc backups.

Mike


----------



## SilverFox (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

I'll jump in on that one...

When you charge at rates below 1C, dT/dt becomes difficult.

Tom


----------



## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Bill,
> 
> Can you please educate us and tell us what those conditions are?
> 
> ...


Mike:

I wish I could! I'm standing in the corner with my dunce hat too 

Now, SilverFox just stated that it was unreliable below 1C but above is some graphs for 2.3Ah cells at 2A which isn't 1C but fairly close. The center two cells didn't show enough rise to meet dT/dt but the outer two did! Confusing but even worse I have another test I did on the same cells in the same slots at 1200ma rate and all four showed the classic dT/dt with flying colors! I think that I'll be able to post that tonight. We need CSI CPF here!


----------



## Mike abcd (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> I'll jump in on that one...
> 
> ...



I understand that the dT/dt magnitude is affected by charge rate. So is -dV. Anything less obvious?

Mike


----------



## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Here’s three more graphs of the same 2.3Ah Duracells charged earlier(Post#264) at 2A but this time it’s at 1200ma. All cells were discharged first and allowed to cool. Cells were marked and installed in the same slots every time. Unlike the 2A tests where only Slots#1/4 showed the dT/dt rise of 1.8F/min, all slots showed the dT/dt rise several minutes prior to showing DONE. Cells were then discharged at 400ma for a capacity check.

Charge/Discharge
Slot#1 = [email protected] min/[email protected] min
Slot#2 = [email protected] min/[email protected] min
Slot#3 = [email protected] min/[email protected] min
Slot#4 = [email protected] min/[email protected] min

Slot#1






Slot#2





Slot#3/4





IR image right after Slots#1/3 were DONE.


----------



## dekelsey61 (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Bill
I have been using the refresh mode on some of my 2500Mah+2700Mah batteries and setting the charge rate at 1100Ma or 1200Ma. All terminated fine with temps. at about 120F. Can we conclude the charger works best at these charge levels and not so good at the 2000Ma(2amp) level? I have not had any problems with the charger in that range. I have not tried the 2amp charge yet.
Dan
,


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## wptski (Jan 10, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Dan:

Comparing my tests at 2A and 1.2A, it appears that Slots#2/3 don't have as high capacity at 2A as it they do at 1.2A! Why? I don't know. Heat maybe as the center slots didn't get as warm at 2A but you might expect the opposite to happen!


----------



## Mike abcd (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Dan:
> 
> Comparing my tests at 2A and 1.2A, it appears that Slots#2/3 don't have as high capacity at 2A as it they do at 1.2A! Why? I don't know. Heat maybe as the center slots didn't get as warm at 2A but you might expect the opposite to happen!



Bill,

I wondered the same thing since I always see higher temps in slots 2/3. Then I realized the cells in slots 2/3 were already partially charged based on the data in post #264

Charge/Discharge
Slot#1 = [email protected] min/[email protected] min
Slot#2 = [email protected] min/[email protected] min
Slot#3 = [email protected] min/[email protected] min
Slot#4 = [email protected] min/[email protected] min

Slot 2/3 show more mAH on discharge than charge. They also show about 110 mAh less discharge capacity than your current test but that's not enough to account for the much shorter charge time. The initial partial charge and less heating because of it might account for that.

Mike


----------



## wptski (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Bill,
> 
> I wondered the same thing since I always see higher temps in slots 2/3. Then I realized the cells in slots 2/3 were already partially charged based on the data in post #264
> 
> ...


Mike:

All cells were fully discharged and cool prior to testing. The center slots do get warmer but it appears that it's only at longer charging times but this seems to increase the capacity a bit too. The no dT/dt at 2A is confusing also but I wonder if all these documents that we refer to all the time are outdated and don't hold true once cell's capacity got above a certain level.

I tried some 1.8Ah PowerEx cells at .5C early on, no graphs but the IR images that I took showed the center slots warmer too. I wonder how they'd do at 1C?

I have some IR images that I'm going to add to the last batch of graphs.


----------



## Mike abcd (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike:
> 
> All cells were fully discharged and cool prior to testing....



Bill,

I'm assuming you charged and then discharged the cells and the data you posted is charge mAH and time, discharge mAH and time (for that charge followed by discharge cycle).

If so, the cells is slots 2/3 showed more mAH discharged than went in on the charge. That seems impossible unless the cells were partially charged first.

The difference seems too large to be accounted for by errors in the C-9000 particularly since the charging process is not 100% efficient.

I guess it's possible that the C-9000 might have terminated the previous discharge cycle early and you started with partially charged cells.

Mike


----------



## wptski (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Bill,
> 
> I'm assuming you charged and then discharged the cells and the data you posted is charge mAH and time, discharge mAH and time (for that charge followed by discharge cycle).
> 
> ...


Mike:

Well, input capacity isn't a true indicator compared to discharge capacity. I didn't log the discharge capacities at that time but I don't remember anything odd! I don't think that they were partially charged. There is something odd about the fact that those slots warm up more at .5C than 1C anyway, so there's more than one thing that doesn't make any sense!


----------



## Mike abcd (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I guess I'm interpreting the data you posted wrong. I thought you posted data for the charge cycle followed by a discharge cycle.

My point was that it's impossible to get more energy out than was put in unless there was already some in there before the charge cycle.

I've consistently seen higher temps in slots 2/3 at charge rates of 1000 and 2000 mA. I haven't seen any significant differences between the slots in charge completeness at the same rate. I have seen a bit higher charge/discharge mAH at 2000 vs 1000 mA.

Mike


----------



## wptski (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike:

Yes, I posted the Charge/Time/Discharge/Time but prior to that was another unposted Discharge too. That's the oddity here or the differences between heat, capacity and time when using the same 2.3Ah cells at 1.2A/2.0A.

My tests are consistent at 1.2A rate but not at 2.0A rate.

What capacity cells are you using?
Are you using the same cells?
Are your cells discharged prior to testing?
Are you charging at 2A and approx. .5C?


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## SilverFox (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Let’s stop for a moment and look at how chargers work.

There are several ways to terminate a charge. They include a timer, temperature differential, maximum temperature, voltage peak, a rate of temperature increase, and a drop in voltage from the peak voltage. There may be others, but this is what comes immediately to mind.

Let’s look at dT/dt. The main difficulty with contestant dT/dt termination is measuring the temperature of the cell. You can imbed a temperature sensor in a battery pack, but it gets difficult with single cells. This signal is dependent on charge rate, and the condition of the cell.

The next difficulty is that it is hard to sell people on buying a charger that only charges their cells up to around 90-95% of full charge. You can get to a full charge, but it takes additional charging time. When the charger indicates that the charge is done, it is inconvenient to wait around for the topping charge to finish bringing the cell up to a full charge. 

Cycle life is vague, but run time is easily measured. If I can get a charger that gives me longer run time, and still a decent life cycle from my cells, I am all for it. 500 – 1000 cycles may not be realized by an average user for 10-20 years. 

10 years ago, cell capacities were in the 800 - 1200 mAh range, NiCd cells were still strong in the running, and fast chargers were charging in 5 hours.

Things have progressed from those times. 

I think if we shoot for 200 - 300 cycles, we will be doing well. This gives us good return on our investment, and allows us to enjoy the incremental improvements in technology.

Another frequently used termination method is negative delta voltage. As the cell reaches full charge, the voltage will drop a little. A standard value is 7 – 10 mV. The RC people frequently use 3 – 5 mV for NiMh cells, they then top off the charge to get the cells full. This method is also dependent on charge rate and condition of the cell.

Now let’s look at maximum voltage. If a charger is used to charge NiCd and NiMh cells, it requires a higher maximum voltage value, because NiCd cells charge to a higher voltage. The problem is that if you use maximum voltage as a back up termination, it can take a NiMh cell a long time to get to a maximum NiCd voltage. This could be what we are seeing with the C9000 charger.

Temperature differential is dependent on ambient temperature, so it is not usually used for charge termination. It is used for a safety to prevent charger melt down.

Maximum temperature is also used as a safety.

We all agree that high temperatures result in lower cycle life. The question is how much do you loose when the cells come off the charger at 140 F vs. 130 F, or 120 F. Duracell has done some testing with some low capacity cells and discovered that if you terminate on a maximum temperature of 104 F, you will only get about 525 cycles from NiMh cells. If you overcharge to 150%, the cycle life drops to around 500 cycles. I should point out that the charging in the Duracell study was done at 1C.

Now, keep in mind that we are seeing temperatures of 130 - 150 F with the C9000 charging to roughly 110%. The BC-900 is the only other consumer charger that reports mAh put into the cells and it throttles the temperature at around 130 F (with version 33, or up to 160 F with version 32) while also charging to around 110%. If we charged to 150% at 1C, I believe the temperatures would be higher. 

I am not sure what we can conclude from this, but if charging to 150% only reduces the cycle life by around 25 cycles, brief temperature excursions may not be as bad as we may think.

I would love to see a study on high capacity cells, but with all the elevated self discharge rate problems we are seeing, I doubt we will see that information for quite some time. Perhaps we can do the testing ourselves…

I did some cycle testing. 2500 mAh cells charged at 7.5 amps and fully discharged every cycle fell on their face at around 125 cycles. I did not formally monitor the cell temperatures during the charging, but it was in the 140 F range. The same cells charged at 1 amp fell on their face at around 150 cycles. This is with cell temperatures in the 120 F range. I did another round of testing under the same conditions with 2000 mAh cells. They were still going strong after 150 cycles. Keep in mind that 150 cycles is roughly 3 years of use for the average person.

I agree that when the cell temperatures get up to 160 F and the shrink wrap melts off the cells, that is too hot, however I am not sure that a brief excursion over 130 F is going to be that drastic.

I have been trying to figure out what is going on with this charger. There are reports of roughly 30 cells failing to properly terminate. Why is this?

I was just re-reading this thread and noticed the voltage graph that Wpski posted for the C9000 (see post # 262). Right after that, NiOOH posted a graph for a different charger also showing voltage (see post #263). Do you see the difference?

The NiOOH graph shows the cell terminated at roughly 1.5 volts. Bills graph shows the C9000 terminating at just over 1.6 volts. 

If you have a charger that terminates at 1.5 volts, it will always run cooler than one that terminates at 1.6 volts. There has been a lot of comparison between different chargers. A problem cell for the C9000 is not a problem for XYZ charger. Could it be that XYZ charger is terminating on a maximum voltage lower than the C9000? Have you ever noticed that the BC-900 will immediately indicate Full when you insert a fully charged cell? This is because the maximum voltage termination value has been tripped by the fully charged cell. The C9000 takes several minutes to check things out and realize that a fully charged cell is really fully charged.

To back this up, I have noticed that my NiCd cells frequently terminate with a flashing “Done” on the C808M. They do not do that with the C9000. This indicates that the C9000 is capable of terminating at a higher voltage.

I am sure there may be more to this, but this may be the main cause of the missed termination issue.

The C9000 utilizes a top off mode, so perhaps William would consider modifying the termination values to a lower voltage. Those of us that use NiCd cells may suffer from this, but it may eliminate the termination issues we are seeing.

Tom


----------



## wptski (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

I can't use "quotes" or IE7 will crash!

The graphs by me and NiOOH are charging voltage not actual cell voltages, although there might be a ratio between the two. I noticed that if I watched the C9000 shown cell voltage as the charging rate is increased so does the charging voltage increase. They do kind-of follow each other for all purposes. I've been experimenting in try to plot the actual cell voltage which has to be read/shown on the OFF pulse of the charger and it's tough going so far!


----------



## bmoorhouse (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Silverfox, thank you for the through post and the great review. I am new to all of this battery stuff, but learning very quickly by following this discussion. 

Your logic makes a lot of sense to me and perhaps your idea of lowering the max voltage is the answer. If so, and MAHA does that, will those of us with current model C9000s be out of luck, or will there be a way to update them via firmware?


----------



## Mike abcd (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> ...
> Now let’s look at maximum voltage. If a charger is used to charge NiCd and NiMh cells, it requires a higher maximum voltage value, because NiCd cells charge to a higher voltage. The problem is that if you use maximum voltage as a back up termination, it can take a NiMh cell a long time to get to a maximum NiCd voltage. This could be what we are seeing with the C9000 charger
> ....
> We all agree that high temperatures result in lower cycle life. The question is how much do you loose when the cells come off the charger at 140 F vs. 130 F, or 120 F. Duracell has done some testing with some low capacity cells and discovered that if you terminate on a maximum temperature of 104 F, you will only get about 525 cycles from NiMh cells. If you overcharge to 150%, the cycle life drops to around 500 cycles. I should point out that the charging in the Duracell study was done at 1C.
> ...



Tom,

I've never seen maximum voltage even discussed as a termination method for NiMH cells by any manufacturer. I also don't remember seeing it listed for the C-9000 anywhere. Do you have any references? BTW, max voltage is VERY dependant on the charge rate relative to capacity but also cell temp and health.

The BC-900 will refuse to charge cells inserted with a voltage it considers too high as it assumes they are already charged. However, it will happily charge cells to a much higher threshold. The "insertion" threshold on mine is 1.40 or 1.41 V and seems quite reasonable. I can remember seeing older AAA cells charged at 700 mA hitting at least 1.56 V. I think I've even seen 1.6+ V.

I can find no mention of maximum voltage being used in the BC-900 manual. I would hope the C-9000 is not using maximum voltage for anything except a backup to terminate charge when other methods (that should have worked) have failed.

I have a BC-900 V32 and have never seen it hit anywhere near 160 deg F and believe me, I would have remembered that. I have only seen it pause the charging due to the over temp sense with 4 x AA @ 1000 mA and my IR thermometer measured the cells in the center (hotter) slots at 125 deg F. I assume the internal temp was higher and the BC-900 sensed that.

BTW, that was too hot for my liking and one of the reasons I was looking for something better.

Do you have a reference to the Duracell overcharge test? I can't find it in their current document. I also thought it was popular consensus that the newer high capacity cells don't tolerate abuse nearly as well as lower capacity ones. Haven't you posted about that many times?

BTW, figure 7.1.1 in the current Duracell document shows a reduction in cycle life by 50% for cells charged and discharged at 45 deg C. Cells were charged at C/4 for 3.2 hours and discharged at C/4 for 2.4 hours (to about 40% capacity).

Granted that's for cells both charged and dischaged at that temp but I've seen cells hit over 60 deg C in the C-9000. IMHO, that's a significant concern. The Duracell data certainly seems to show temperature is a very significant factor in cycle life.

I'm really puzzled by your apparent lack of concern about the high cell temperatures we're seeing.

Mike


----------



## dekelsey61 (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom,
I think you may be right with the higher voltage cutoff like bmoorhouse said. I also wounder like bmoorhouse is saying what will maha do for all of us when they update this charger to take care of these issues that have bought the early version of this charger. With Maha's great customer service I would think they would make it right for all of us.
Dan




bmoorhouse said:


> Silverfox, thank you for the through post and the great review. I am new to all of this battery stuff, but learning very quickly by following this discussion.
> 
> Your logic makes a lot of sense to me and perhaps your idea of lowering the max voltage is the answer. If so, and MAHA does that, will those of us with current model C9000s be out of luck, or will there be a way to update them via firmware?


----------



## bob_ninja (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Tom,
> ...
> I'm really puzzled by your apparent lack of concern about the high cell temperatures we're seeing.
> 
> Mike



Tom's expectations of battery lifespan might be lower than yours or mine. He seems to be happy with 100 cycles. I don't see why should a modern NiMH battery last 100 cycles when 10-20 year old NiCds easily last 500+ cycles. That is not progress.

Anyway, he did some tests, such as the one he mentioned, charging at super quick rate (more heat) vs quick rate (less heat) and found minor difference in lifespan. However, this has more to do with high capacity cell construction being so poor that it doesn't last long regardless of heat.

The other problem is that the older studies/experiments were done on older lower capacity cells (more robust) whereas the current standard are higher capacity cells (fragile). Therefore they have different characteristics, including vulnerability to heat damage while charging. I haven't seen much info on this, so can only guess.

In short, you concern or lack thereof for heat during charging process is based on lifespan expectations. Most people seem to be happy with 100ish cycles and couldn't care less about heat.


----------



## SilverFox (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Here is a manufacturer that utilizes peak voltage detection for charge termination. It is interesting to note that PVD is the main method of termination for charge rates under 2C. This just happened to be the first one that came up on a search. I am sure there are lots of others out there as well.

I find it interesting that people think that their low charge rate low cost charger somehow has a "magic" end of charge termination signal enhancer that enables their charger to see and end of charge signal when there is no signal present. I believe these chargers are terminating on a lower maximum cell voltage. 

The BC-900 immediately recognizes that a cell is full. Take a cell that is fully charged on the BC-900 and insert it into the C9000. It will take a few minutes for the C9000 to indicate that it is fully charged because the peak voltage value is higher on the C9000.

One of the main changes from V32 to V33 for the BC-900 was changing the maximum cell temperature from 160 F to 130 F. This was documented in detail on the German camera forum that was analyzing the BC-900.

The Duracell data is listed in Figure 29.20 of the Handbook of Batteries, third edition. It is copyrighted, so I can't publish the graph without permission. Pick up a copy of the book, it is a wealth of information.

I agree that temperature is a significant factor in cycle life. I just don't agree that an occasional excursion to 140 F at the end of the charge cycle is detrimental to a large extent. If we were to soak the cell at 140 F for an extended period of time, I believe we would see problems, however I am not convinced that a brief excursion for a few minutes has that large an effect.

I don't believe I have a lack of concern, I just am looking at different numbers. You seem to come across as believing that when the cell temperature approaches 140 F, or if there is any degree of over charge, the cell is going to immediately die. It seems that NiOOH, and some others, share your beliefs. I have demonstrated that even the high capacity cells can withstand multiple cycles of 3C charging and 100% discharges. The Duracell data shows that there is a loss of cycle life when you charge to 150%, but the loss is only around 5%. I am taking the position that a 5% loss in cycle life is not that significant.

I am concerned when cells melt the shrink wrap off of cells. I think Maha needs to make some adjustments so this does not happen again. I am also concerned by hot cell temperatures, but I just don't know where the line is between warm and hot.

Tom


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## bfg9000 (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



bob_ninja said:


> Tom's expectations of battery lifespan might be lower than yours or mine. He seems to be happy with 100 cycles. I don't see why should a modern NiMH battery last 100 cycles when 10-20 year old NiCds easily last 500+ cycles. That is not progress.


I should point out that 500 cycles of a 600mAh NiCd AA cell delivers exactly the same total mAh as a 2500mAh NiMH AA one does in 120 cycles.

If it weren't for the whole self-discharge failure issue I think most of us would prefer to have the same total capacity using fewer charges, and in that light a 125-150 cycle lifespan for high capacity cells doesn't seem too bad.


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## SilverFox (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bob,

NiCd chemistry is simply more robust than NiMh. It is unfortunate that NiCd chemistry is toxic and that we can't get more capacity from it.

For the record, I am concerned about heat, I just don't know where the line is between warm and hot.

I was very disappointed when my set of test cells finally died. I tallied up their performance and realized that they had over 200 cycles on them, with 65 of those cycles on the Energizer 15 minute charger. They had been "cooked" on the Maha 401 on high, and in spite of all of this "abuse" the still survived 200 cycles over 3 years of hard use. I think this is pretty good service from a $2.30 cell.

Tom


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## bfg9000 (Jan 11, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I just calculated that 120 20 minute charges on a "15 minute" charger is 40 hours, while 500 charges on a 5 hour charger is 2500 hours (nearly 3 1/2 months). That's what probably best describes the progress over the last 20 years; same total capacity with fewer charges and less time spent charging.

Anywhere I still use dumb constant trickle chargers (solar lights, toothbrush, cordless phone, etc) I still use NiCD though.


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## NiOOH (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

In my experience, repeated overcharging at currents of 0.5C and higher can hurt cycle life a lot more than suggested by manufacturers. Charging on something like Maha 401FS on fast mode, especially high capacity cells results in no more than 100 cycles. I have cells that are charged 2-3 times per week. With 100 cycles they will last less than a year, which is not acceptable. 
Also, I just can't sit and watch the charger overcharging my cells. IMO the technology has advanced enough to be possible to design a charger that chargers according to manufacturers recommendations.


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## bob_ninja (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

bfg9000,
Let us do the math properly and see what we get. BTW I do prefer NiMH, but should still like to keep some of the performance of NiCd if possible.

typical 2.5 Ah NiMH AA x 120 cycles = 300 Ah

In truth, after 120 cycles they are down to 80% of original capacity, so during this period on average their capacity is 2.5 Ah x 90% = 2.25 Ah

2.25 Ah NiMH AA x 120 cycles = 270 Ah

Of course, I cannot be bothered to run to the charger and top up my AAs every time I use them, so on average they'll sit idle for say 30 days. Even my AAAs easily last one month in MP3 player, so this is a fair number. Again to keep things simple I'll use the value of 15% self discharge / month (because there are too many factors, like temp, age,...)

270 Ah x 85% = 229.5 Ah

As many pointed out these batteries are fragile. Thus we must qualify that these 229.5 Ah are delivered at a rate of no more than 2C. Thus they don't even work for certain applications like flashes and RC, etc. I found out the hard way and cost me some time and money.

These days NiCd is easily 700 mAh

typical 0.7 Ah NiCd AA x 500 cycles x 90% x 92% = 290 Ah
(lower self discharge rate of say 8%)

And these are tough 290 amps, at cold temps, at 2C and 3C rates, etc.

Like I said, I still prefer NiMH but also had to recognize that I still need NiCd.
Now I don't expect 500 cycles from NiMH but also don't expect 120 cycles. Just to put these values in perspective, it is a 500 - 120 = 380 cycles, 76% drop!!!!!!!! That is too much for me.

I do expect a reasonable 300 cycles from NiMH, which is 200 cycles less, or 40% loss. That is still a lot, but not as bad as the other number.


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## SilverFox (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello NiOOH,

I think, in general, I agree with you.

The question that remains is What constitutes an overcharge?

Duracell suggests that if cells get to 104 F while charging, damage is being done. On the other hand, if you limit the charge to 120%, you can expect 1000 cycles from your cells. This is with 1C charging and a 100% 1C depth of discharge down to 1.0 volts per cell.

A charger to do this would be straight forward. You put your cell into the charger and enter the capacity. The charger would then discharge the cell down to 1 volt at 1C, then charge at 1C to 120% of the capacity you entered.

Just a minute now... The C9000 already does this. If you look at the capacities going into the cells (ignoring for the moment the missed terminations) it seems that it is putting around 110% back in. I wonder how Duracell was able to charge a cell at 1C to 120% and keep the temperature below 104 F?

At any rate, if you are looking for a charger that has that capability, the Schulze comes very close. 

If you have an application where you are going through 2 - 3 charge/discharge cycles a week, I would recommend using some 2000 mAh cells. If you recall from my cycle testing observations, these cells can handle the Energizer 15 minute charger and are still going strong after 150 cycles. They would probably be good for 300 - 500 cycles before they die and look at the time you could save on charging...

What capacity cells are you using, and how are they holding up?

Tom


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## SilverFox (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bob,

In my humble opinion, your numbers are still off...  

A 2500 mAh NiMh cell is probably only good for 2300 mAh, where as the 700 mAh NiCd cell will more than likely test out closer to 800 mAh...

Tom


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## wptski (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

I'm wondering if you took a cell externally connected to the C9000 or any other charger and charged it at 1C, how warm would it get? Keeping it away from the chargers heat helps, we know that already. I can remember posting a graph from a BC-900 with one cell installed and another connected outside the charger. The outside cell stayed cooler, that much I remember but not the temperatures or the charging rate/capacity!


----------



## SilverFox (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

That is a good point. This charger gets hot when charging 4 cells at 2 amps. Perhaps the case could be opened up somewhat. This has been mentioned before, but I don't think anyone has tried it.

Tom


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## wptski (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> That is a good point. This charger gets hot when charging 4 cells at 2 amps. Perhaps the case could be opened up somewhat. This has been mentioned before, but I don't think anyone has tried it.
> 
> Tom


Tom:

Well, it also heated the center slots higher at .5C than it at 2A on 2.3Ah cells! 

This might be similiar to cooking something on a stove. It's better to cook longer at a lower temperature than it is for a shorter time at a higher temperature, things get warmer way inside with the lower/longer method.


----------



## Mike abcd (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> Here is a manufacturer that utilizes peak voltage detection for charge termination. It is interesting to note that PVD is the main method of termination for charge rates under 2C. This just happened to be the first one that came up on a search. I am sure there are lots of others out there as well.
> 
> ...



Tom,

You're interpreting the charger IC data sheet wrong. Yes, it will terminate charge if a cell hits a maximum voltage (Vmcv) in any mode but that's set at 2.0 V and clearly is a safety backup and not intended to be hit under normal conditions.

PVD used at charge rates of C/2 and 1C is defined as a -2.5 mV +/- 2.5 mV CHANGE in the cell voltage and has nothing to do with the absolute cell voltage. It's basically a 0 dV detection and more sensitive than most chargers -dV.

I'll stand by my statement that I have not seen any cell manufacturer even discuss absolute cell voltage as a valid charge termination technique for NiMH.

Maximum cell voltage is higher at higher charge rates than lower charge rates for any given cell. Your speculation that chargers are using absolute voltage to terminate at lower charge rates is nonsense IMHO. -dV is smaller, and according to the cell manufacturers potentially non existent, but in practice can still occur and be detected as low as .1C and lower.

I also stand by my observations on the BC-900 regarding your comments on maximum cell voltage. The BC-900 implements a check when a cell is inserted and will not BEGIN to fast charge a cell whose initial resting voltage is over 1.39 (1.40?) V. However, it will quite happily CONTINUE to fast charge cells past 1.6 volts that met the initial resting voltage test. The BC-900 initial check is a safety feature that tries to prevent users from inserting or re-inserting fully charged cells since that can lead to charge termination failures. It has nothing to due with normal charge termination.

IMHO, the initial resting voltage check that the BC-900 does is a reasonable test that the C-9000 appears to omit and neither charger implements an absolute voltage check for normal charge termination. It's possible that either or both might use maximum voltage as a safety backup like the charger IC you posted but I see no relevance to the discussion of the C-9000 and cell heating.

The C-9000 is NOT terminating charge on cells that were inserted fully charged on absolute voltage and I have voltage vs time graphs to prove it. It's terminating the charge AFTER the cell voltage has begun to drop, IOW, on -dV.

Since my 2 years of high school German have long faded into oblivion, I assume I wouldn't be able to follow the German forum BC-900 discussion but I'd still appreciate a link as Google translation might help. However, I still stand by my observation that I have seen my v32 BC-900 pause charging at a cell temp of 125 deg F and have NEVER seen cell temperatures over 130 deg F. I have a pdf of the BC-900 manual that was downloaded on 11/28/2005 that lists 127 deg F as the threshold for pausing charging.

Again, although the BC-900 does not heat cells nearly as much as other chargers, I have never been happy with how hot it gets 4 AA cells at 1000 mA. I am therefore even less happy with the C-9000 heating cells even more. To be fair, the C-9000 is not a lot worse at 1000 mA, just a little. At 2000 mA it's a LOT worse than the BC-900 at 1000 mA making its higher charge currents unsuitable for normal use with 4 AA cells IMHO.

I would never suggest that you violate copyright law but fair use certainly allows you to post a summary. What was the cell type and capacity used in the Duracell test? What were the charge and discharge rates and ambient temperatures?

The "Handbook of Batteries, third edition" has a copyright date of 2002 and is a compilation of data by 2 writers/editors. I suspect much of the data dates to considerably earlier than 2002. I feel you are seriously misleading folks who rightfully respect your opinions by stating than a 150% over charge results in only a 5% loss in service life with current cells and ignoring the current Duracell data on the effects of temperature on service life that shows a very significant impact.

The basic problem with the C-9000 is that the charger circuitry gets VERY hot when charging multiple cells at higher rates. This causes the cells to get heated to temperatures at and above the cell manufacturer's maximum ambient temperature of 40 deg C for a large portion of the charge cycle long before the cell self heating becomes significant. I even suspect that the higher "locall ambient" temperature the cells see due to charger circuitry heating causes the cell temperature rise to be greater than it would be at lower ambient temps. The result is that cells get heated close to or over the maximum backup safety temperature of 140 deg F (60 deg C) that Duracell/Sanyo/etc specifies for charge termination failure.

I fail to comprehend how that can be viewed as benign or acceptable.

If I've given you the impression that "that when the cell temperature approaches 140 F, or if there is any degree of over charge, the cell is going to immediately die", please accept my apologies. That was not my intent and is not my belief. I just disagree very strongly with you that the temperatures we're seeing with 4 cells at higher rates are benign or relatively inconsequential.

BTW, other than the relatively small number of outright charge terminations, the C-9000 is not grossly overcharging cells (>110%). Just look at the charge input vs cell capacity and that's apparent. You seem to be assuming the elevated cell temperatures are being caused solely by too much charge input and ignoring the obvious cell heating by the charger circuitry that IMHO is by far the major cause.

Just for the record, I view even the small number of C-9000 charge terminations that have been reported with quality cells to be unacceptable and a serious cause for concern.

Mike


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## Mike abcd (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> ...
> 
> Just a minute now... The C9000 already does this. If you look at the capacities going into the cells (ignoring for the moment the missed terminations) it seems that it is putting around 110% back in. I wonder how Duracell was able to charge a cell at 1C to 120% and keep the temperature below 104 F?
> ...
> ...



It's real simple. Keep the heat from the charger circuitry from heating the cells and don't overcharge.

Take a look at look at figure 8 in the Sanyo doc. They do a lot better than that when charging cells at 1C @ 20 deg C ambient.

Mike


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## Mike abcd (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Tom:
> 
> I'm wondering if you took a cell externally connected to the C9000 or any other charger and charged it at 1C, how warm would it get? Keeping it away from the chargers heat helps, we know that already. I can remember posting a graph from a BC-900 with one cell installed and another connected outside the charger. The outside cell stayed cooler, that much I remember but not the temperatures or the charging rate/capacity!



That's a test I've thought about doing. I just don't have any way to connect a single cell other than jumpering up empty slots in an 8 cell holder. I've got to get around to making a battery clamp or getting magnets with charge leads one of these days. I actually have one of the Harbor Freight clamps folks have been modding for this.

I'd run the test with 3 cells in the C-9000 and the 4th connected externally preferably suspended rather than lying flat on a surface. I have some concern about adding too much capacitance in the connections due to the pulse charging that the C-9000 uses.

Mike


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## Mike abcd (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Tom:
> 
> Well, it also heated the center slots higher at .5C than it at 2A on 2.3Ah cells!
> 
> This might be similiar to cooking something on a stove. It's better to cook longer at a lower temperature than it is for a shorter time at a higher temperature, things get warmer way inside with the lower/longer method.



Bill,

As I've mentioned before I've got lots of test cycles done and all had higher temps on slots 2/3 than 3/4 and higher temps at 2000 mA than 1000 mA on all slots.

Your data showed less charge input and a shorter charge time on your test on slots 2/3 than 3/4. All my tests were done with cells that test within 3% capacity across the 4 cells in a test group and show much closer charge input and charge times than your test.

Can you consider re-running your test at the 2000 mA charge rate after discharging all the cells?

Mike


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## Mike abcd (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Bill,
> 
> That is a good point. This charger gets hot when charging 4 cells at 2 amps. Perhaps the case could be opened up somewhat. This has been mentioned before, but I don't think anyone has tried it.
> 
> Tom



I've mentioned it before and seriously considered it. The only thing stopping me is that I haven't been able to convince myself to keep the C-9000 and I want to be able to return it to TD without issues.

I'm sitting on a $175 order from them as I bought two C-9000 chargers and a bunch of cells for a friend. There's no way I'm giving the charger to my friend based on my testing so at least one charger and the cells are definitely going back to TD.

If I decide to keep a C-9000, I'll open it up and run the test but I have some ideas on trying to isolate the cells from at least some of the charger heat that I want to try first. If that looks promising, I'm far more likely to go further.

Mike


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## wptski (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Bill,
> 
> As I've mentioned before I've got lots of test cycles done and all had higher temps on slots 2/3 than 3/4 and higher temps at 2000 mA than 1000 mA on all slots.
> 
> ...


Mike:

The test in Post#264 was at 2A and the cells were discharged prior to the test.


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## wptski (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

I took a fully discharged 2.3Ah Duracell and used a Duratrax ICE at 2.3A charging rate, senitivity set to 5mv.

Input=2257mAh
Termination at 59 min
dT/dt occured at 57 min
Max temperature 106.8F
Discharge at 500ma, C9000= [email protected] min

So, not that far away from Duracell's 104F!


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## 3rdDerivative (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I considered modifying the case also on my C9000 before I returned it. I think the top end need more cooling holes, IMHO. And some cutoff values needed to be adjusted as SilverFox noted on the voltage threshold.

Probably looking like a yo-yo, but I ordered from TD a C800s a few days ago thinking I would use the 8 slots along with its reported cool charging characteristics. Then noticed last night on Amazon, the BC-900 is now $35. So what the heck, I ordered it also. 

When the C9000 issues settles down, I will still get one. I can always either just keep the BC-900 or give it away (and have a daughter at DU with all her electronic stuff). I am sure the C800S will be a nice workhorse of a charger.


----------



## coppertrail (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

IMO, the C800S is an excellent product. It's been my primary charger since I received it a month ago.


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## EngrPaul (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I agree, the C800S is my primary still. The C9000 is only used for break-in and analysis.


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## macdude22 (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

I couldn't use my C9000 for main charging if I wanted too, it's too busy cycling and analyzing batteries.


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## SilverFox (Jan 12, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

I see we still are not communicating… Let me try again…

I never said that peak voltage was a valid termination technique. I simply pointed out that if you miss the – dV signal, it is used to terminate the charge. 

So, let’s walk through this step by step. We have documented cases where the C9000 continued to charge a cell and put several times the capacity of the cell into the cell. The cell temperature remained low, but the charger just kept charging. In all cases that I have been able to review, the cell voltage remained below 1.6 volts.

The C9000 uses 5 mV as the –dV value, so in these cases there was less than this during the charge. Keep in mind that this is more sensitive than what us usually used. The “standard” value is 7 mV and before that it was 10 mV. 

Since we seem to be throwing things back a forth… Show me the voltage drop value when charging at 0.1C, or lower. If it is less than 5, 7, or 10 mV, the current chargers will not see it. I would like to see a graph, but will accept a table of the actual values based on 5 different brands and capacities of cells.

The battery manufacturers say that the –dV is not reliable at low charge rates, yet you insist that because your charger is terminating, it has to be on –dV. Now is your chance to prove the battery manufacturers wrong on this.

I can show you two cases where charging was terminated on peak voltage. The C808M, when charging NiCd cells, will frequently terminate with a flashing “Done.” If you take the time to read back through the C808M thread, you will find that the flashing “Done” means that the charge was terminated on high voltage.

The next case involves the C9000 charging Radio Shack 1000 mAh NiCd cells. The charge terminated, but checking the cell voltage I find that they are at 1.36 volts. How did the charge terminate? It terminated on high voltage, but the cell was not fully charged. These cells are well worn and the termination came just over 4 hours into the charge. The charging rate was 200 mA.

Your observations with the BC-900 further confirm my stand. The BC-900 checks the cell and if it is 1.4 or higher, it signals Full. The C9000, with a higher voltage set point starts charging the cell until it reaches a higher voltage, then signals Done.

This  isn’t the correct thread, but it will get you into the German forum.

I thought I did a pretty good job of summarizing the data from the Duracell graph. The cells used are probably the same cells used in the PDF document on the Duracell website. Unfortunately, they don’t tell you what cells were used. I believe the 2002 data is the most current available, except for the data that I have generated. The book uses many of the same graphs that are displayed on the website, so all of this data may be less than current. I believe, if you go back and read what I wrote, you will find that the charging and discharging was done at 1C. I did leave out what the room temperature was, but only because Duracell left it out too.

Your comment about me misleading folks is unfounded. I was not presenting my opinion, I was merely stating the Duracell test results. I should also point out that the Duracell graph you are referring to is Figure 7.1.1 on the website and it is titled “Impact on cycle life from repeated charging and discharging at various ambient temperatures.” It is good to understand that if you live in a hot climate and are charging and discharging in 104 F ambient conditions, your cells will only last for 60% of their expected cycle life.

My opinion is that 160 F is too hot. 150 F may also be too hot, but below that I don’t know. Duracell (and others) like a maximum of 140 F, but don’t expand on it. One could argue that as long as your cells stay below 140 F, you should get 500 cycles from them. However, I have proven that wrong with my cycle testing. 

I agree that the C9000 heats the cells up. I disagree that is the basic problem with it. The basic problem with it is that it misses the end of charge termination.

I can live with warm cells, but missing the termination signal needs to be addressed by Maha.

I have thrown the gauntlet down. Show me the – dV values for charging at 0.1C and then we can continue this discussion.

By the way, the C9000 runs a lot cooler outside of its case, and it has a high temperature shut off. I used a heat gun to heat up the negative end of some cells and measured the termination when the cells hit 143 F. This was after I took my charger apart and added some thermal paste to get better contact between the temperature sensors and the metal strip that is used to monitor cell temperature.

Tom


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## NiOOH (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hi Tom.
After several of my IG Sanyo 2500 mAh cells developed higher self-discharge and all of them show signs of increased internal resistance, I retired them.
These cells were used a little over a year and had 100-150 cycles behind their backs (approximately 2/3 of them shallow), charged on the following chargers:
Lenmar Pro66 (not overcharging)
Lenmar Mach1 Gamma (possibly undercharging slightly)
Vanson BC1-HU (overcharging slightly)
Lightning Pack 4000N (possibly undercharging slightly)
La Crosse BC900 at 700-1000 mA (overcharging slightly)

As you know, I am trying to select chargers and charging conditions that are gentle to the cells. I cannot say that these cells were abused in any way, electrically or mechanically. They were used in a digital camera, couple of low current draw Mags, radios, walkmen, in other words nothing that would draw more than 1A peak current if that. They were discharged to 1 V/cell every 3-5 cycles, and were run through a conditioning charge at 200 mA on average once every 15 cycles. 
Despite all this care they failed way to soon IMO.

At the same time, I have and still use 1600 mAh cells made by Sanyo (Kodak-branded) purchased in 2002. These cells have something like 400 cycles and still hold 90% of their initial capacity under 0.2C load with good self-discharge and internal resistance.
Clearly, the new, high capacity cells do not hold as good. So, I replaced my failed IG 2500 mAh cells with 8 Eneloops, 4x2100 mAh and 4x1700 mAh Sanyo cells. This happen a couple of months ago, so it is still too early to judge their long-term performance.


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## NiOOH (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

... and concerning the brief overcharge issue,
Tom, I believe you have the Catella Generics report, ordered bu the Swedish Consumer Right Council translated in English.
There, you can see what a relatively brief overcharging at 1C does to cycle life. Charging at 1C to -dV of 10 mV takes approximately 70 minutes. These means that the overcharging applied to these cells was no more than 10 minutes at 1C. I also know that there are chargers that would apply this amount to overcharge due to inpropper design. The overcharged cells berelly lasted for 100 cycles under high discharge load conditions. Think what is going to happen with cycle life if your cells are subjected to missed termination at 1C, say every 10th cycle and receive 200% input current. It is my guess that these cells would last less than 100 cycles no matter what capacity they are. There is also a risk of venting or at least melting of the wraps.


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## bmoorhouse (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



3rdDerivative said:


> Then noticed last night on Amazon, the BC-900 is now $35. So what the heck, I ordered it also.



Do you have a link for that? I just checked and couldn't find it. Perhaps I missed the boat. If not, I would order one to get it at that price as a back-up in case the C9000 I ordered and should receive either today or Tuesday has problems.


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## SilverFox (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello NiOOH,

It seems that the problems with the 2500 mAh cells will never end… I still have some Energizer and Sanyo 2500 cells, and I am waiting for them to develop the problems with high rates of self discharge.

Thank you for reminding me of the Swedish study. It is unfortunate that they did not monitor the cell temperatures during their testing.

The Swedish study can be found here .

Their test was conducted with Duracell 1800 mAh cells. They did some cycling to break the cells in and measured their capacity. Table 1 shows that with a 0.2C discharge rate (C/5) the cells tested at 1673 mAh, and at a 1.0C discharge rate (C/1) they tested at 1589 mAh. I believe there is a comment that these cells should have been labeled as 1600 mAh cells, but they tested them as if they were 1800 mAh cells.

They studied 3 cases.

Case 1 involved normal charging. They charged at 1800 mA and terminated the charge with a 10 mV – delta V.

Case 2 involved a timed overcharge. The charged at 1800 mA for 1.33 hours.

Case 3 also involved a timed overcharge. This time they charged at 600 mA for about 4 hours. 

Both Case 2 and 3 result in a 30% overcharge. You brought up that a 1C charge actually takes around 10% more than an hour, but in this case the cells tested out at 1600 mAh, but were treated as 1800 mAh cells. In this case, charging at 1800 mA results in a full charge in roughly 60 minutes. 

The question is: What is the effect of a 30% overcharge on 1800 mAh cells?

The answer is shown in Figures 2 and 3. Figure 2 shows discharge capacities as a function of cycles with a discharge current of 1800 mA. Figure 3 shows the same data, but the discharge current of 300 mA.

Remember that cycle life is defined as the number of cycles to where the capacity drops to 80%. At a normal terminated charge of 1800 mA, these 1800 mAh cells are good for around 500 cycles. When overcharged by 30% using an 1800 mA charge rate, the cycle life drops to 100 cycles.

Figure 4 shows the difference between overcharging by 30% at 1800 mA, vs. overcharging by 30% at 600 mA. In both cases we have a 30% overcharge, but you can see that the higher charge rate does more damage. I can’t help but think that this is where the temperature effects come in, but that data is not included in the report.

I think all can see that proper termination is needed for long cycle life. If the cell is overcharged, it is better if it occurs at a lower charge rate rather than a high charge rate. 

Tom


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## Mike abcd (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> I see we still are not communicating… Let me try again…
> 
> ...



https://www.candlepowerforums.com/posts/1783674&postcount=308

Long post by you concluding that lowering the C-9000 "termination voltage" might help things. 

You also said "Have you ever noticed that the BC-900 will immediately indicate Full when you insert a fully charged cell? This is because the maximum voltage termination value has been tripped by the fully charged cell."

https://www.candlepowerforums.com/posts/1784003&postcount=311

Long reply by me stating I've never even seen maximum voltage discussed as a "valid" charge termination technique. My apologies for using "valid" and not making clear that I was referring only to NiMH batteries. I have no current interest in charging NiCad AA/AA cells.

I also pointed out that the BC-900 "Full" indication on batteries inserted with a voltage >= 1.40 V is only an initial check and NOT used for charge termination. Let me add now that every cell I have charged on the BC-900 ALWAYS hits more than 1.40 V when charging cells even at 200 mA. The initial voltage check value is NOT used for charge termination. I've seen it hit at least 1.60 V with some cells. Might there be a higher voltage used for fault detection and not mentioned in the docs? Possibly, but it has NOTHING to do with the initial voltage check.

https://www.candlepowerforums.com/posts/1784322&postcount=314

Long reply from you. Some quotes and comments.

"Here is a manufacturer that utilizes peak voltage detection for charge termination. It is interesting to note that PVD is the main method of termination for charge rates under 2C."
My apologies for assuming that you thought PVD was using a voltage value for charge termination. However, the 2.0 V level used for charge termination is clearly not used for charge termination just gross fault detection. I fail to understand your purpose in posting the reference.

"I find it interesting that people think that their low charge rate low cost charger somehow has a "magic" end of charge termination signal enhancer that enables their charger to see and end of charge signal when there is no signal present. I believe these chargers are terminating on a lower maximum cell voltage."

Dead wrong. Lower charge rates result in LOWER peak voltages. An NiMH cell will never hit as high a voltage (regardless of the over charge) as the same cell charged at a much higher rate, 200 mA vs 1000 mA for example.

Hopefully this graph from the Sanyo doc will convince you where I have failed. NiMH voltage checks don't work in detecting over charge.




I did not claim that -dV is reliable at low rates just that my BC-900 is capable of detecting it even at 200 mA on a 2500 mAH cell. Here's some data from a test I did with time and cell voltage noted.

Time V
7:00 1.39
8:00 1.40
9:00 1.41
10:00 1.42
11:00 1.46
11:30 1.47
12:00 1.47
12:50 1.47

Please tell me why the charge terminated if not on -dV. It's clearly not on max voltage, cells only hit slightly over 100 F, total charge input is well under the 3000 mAH BC-900 limit... I can't imagine anything other than -dV. When I get a chance, I'll see if I can log some BC-900 voltage readings on a 200 mA charge and give you a picture that can convince you where words cannot.

Duracell, Sanyo etc specify 104 F as the maximum ambient temperature for charging. They don't "like" 140 F. They just specify it as a backup to terminate charge when other methods have failed. The C-9000 circuitry heats the cells so much that they spend most of the charge cycle at and above a 104 F "ambient".

The current Sanyo doc shows a huge life cycle hit from elevated temperatures. Take a look at section 2-4-2.
"We recomend using the Twicell within a temperature range of 0 to 40 C. *In particular, to prolong the service life of the Twicell, we recommend charging it at room temperature" *(bold emphasis by me)
Again the elevated cell temperatures we're seeing are not the result of gross overcharging as can be seen by comparing charge input to cell capacity. I can't understand how you can conclude that those temperatures only cause about a 5% loss in cycle life based on a test on over charging lower capacity cells that didn't even provide cell temperatures while ignoring the more relevant data in the current Sanyo doc.

Since you've already opened your C-9000, can you run a test on 4 AA cells at 2000 mA and post the temperatures of the cells to compare with our other tests.

Tom, with all due respect, I'm not going to continue going in circles with you on this. I'd rather spend the time posting some of my voltage monitoring tests.

Mike


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## SilverFox (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

You are correct...

The cell voltage is lower at low charge rates.

However, I am also correct...

There is no discernible - dV signal at low charge rates.

So the question remains, how does the BC-900 terminate the charge? Perhaps it is using 0 dV...

I believe the C9000 was running around 10 F cooler without the case. I will try and get some numbers later on. I am in the middle of something else right now.

Tom


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## Mike abcd (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> However, I am also correct...
> 
> There is no discernible - dV signal at low charge rates.
> ...
> ...



There's no discernible -dV on the graph even at .5 C...but there is in the real world or missed terminations would be incredibly common.

I'm going to post some 1000 mA charge data on Energizer 2500s, < .5 C. Tell me if you can see a -dV.

I'll run a test at 200 mA on the C-9000 when I get time. I've got some other stuff I need the meter for first.

Mike


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## Mike abcd (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Here’s my my very long and long overdue post on the results of logging the battery voltage during C-9000 charging. I’m not sure how long these graphs will stay available. If anybody is willing to host them, you can download them, PM me with the links and I’ll edit this post.

I'm using a Radio Shack 22-812 meter with a serial interface and PC data logging S/W. It only logs data once per second but appears to have a sample and hold on its front end with a very short aperture time. The data plots look really ugly with samples at the resting voltage, higher voltage during the charging pulse and in between. However at 1000 mA charge, the bulk of the samples appear to be taken during the no current "resting period" due to the low duty cycle.

It's easy to track the upward trend on the lower end of the sawtooth plots @ 1000 mA charge rate. I've done LOTS of spot checks and the lower readings are always within .010 and .015 volts of the Maha voltage display and increase monotonically by the meter's 1 mV resolution (until the voltage flattens and drops at the end of charge) with occasional .001 V jitter (1 digit) that is to be expected.

I'm convinced it's showing an accurate picture of the cell voltage during a 1000 mA charge but others may disagree.

The first 2 images are of a single Energizer 2500 charged at 1000 mA in slot 2. First the full charge cycle, then zoomed in on the end of charge.

You should be able to click on either the link or the thumbnail for each graph to see the full version. 

http://123pichosting.com/images/2247Maha dV test 1 Full.jpg





http://123pichosting.com/images/7145Maha dV test 1 zoomed.jpg







No big surprises here. The graph shows the PWM charging used by the C-9000 with the voltage measured about .1 V higher during the charge pulse than during the off period and “resting time” where the C-9000 reads the cell voltage according to William C. They also show the charge being terminated when the resting voltage drops exactly or very close to .005 V (5 mV) that William posted.

Well actually there is something VERY interesting here but I didn’t spot it until after I had run some other tests. Take a look at the “big” picture and see if you’re quicker than I was. If not, we’ll see it real soon anyway… 

I repeated the charge test at 2000 mA with four Energizer 2500 cells. The charger circuitry got significantly hotter as did the cells but otherwise it looks the same as with one cell.

http://123pichosting.com/images/5344Maha dV test 2 Full.jpg





The graph again shows the fast charge termination at or very close to a –dV of 5 mV. I’m including it here because I ran it for a bit after the fast charge terminated. It seems to show the top off charge starting after the fast charge terminates. It’s the much smaller peak to peak “hash” that you see as the battery voltage drops after the high fast charging current has ended. You can also see the start of this on the earlier graph.

William has stated the top off is 100 mA for 2 hours. What surprised me is that the C-9000 seems to be doing this even after it apparently terminated on –dV. I’m not aware of any cell manufacturer that advises a top off after –dV termination. They only advise .1 C for ½ hour when terminating on dT/dt. It really concerns me if it happens on AAA cells of much lower capacity.

Moving on… 

I initially though I couldn’t get any useful data much above a 1000 mA charge rate. Above 1000 mA, the duty cycle increases so that my meter has a much smaller chance of sampling the data during the off/resting period and I couldn’t get enough samples to track the voltage that the C-9000 uses for charge termination. Then I realized, at 2000 mA, the meter samples the data during the “on” charge pulse pretty consistently so I decided to do a quick test.

Here’s the graph of a single energizer 2500 that was already charged on the C-9000 then allowed to rest overnight. The charge rate is 2000 mA here and we’re looking at the “top” of the curve tracking the cell voltage during the charge pulse. The voltage readings again tracked the C-9000 displayed readings closely except here my logged values were consistently about .10 V higher since they were measured during the charge pulse vs the C-9000 measurement during the off/resting portion.

http://123pichosting.com/images/4869Maha dV test 3 2000 mA 1 cell.jpg





This one really surprised me. The voltage is higher since we’re tracking the voltage during the charge pulse and increases much more quickly since the cell was already charged and being charged at a higher rate. None of that was surprising.

Now look at the voltage drop before the C-9000 terminates the charge! Notice it’s a LOT bigger than the 5 mV –dV termination that we saw earlier.

Zoomed in on the end of charge for a closer look…

http://123pichosting.com/images/4681Maha dV test 3 2000 mA 1 cell zoomed.jpg





Hmmm, ~13 mV drop before charge termination… Why didn’t the C-9000 terminate sooner??? 

Now go back and look at the first graph. Even though we have much better tracking there of the resting voltage than the voltage during the charge pulse, you can easily see that the –dV under charge is larger than under rest where the C-9000 does its checks. Roughly 2.5x-3x bigger!

So what? Well I can’t remember seeing pulse charging discussed anywhere in any of the cell manufacturer’s NiMH docs I’ve read. They all seem to assume the use of a constant charging current with cell voltage measured while the charging current is applied. That’s what all their graphs show.

Now I understand why Maha used PWM pulse charging, as it’s cheaper to implement variable rates on multiple independent stations. It’s also probably cheaper and/or simpler to measure the voltage under rest. However, it seems to significantly reduce the potential to sense –dV. I’m sure some chargers are far worse. But sensing during rest at a threshold of 5 mV –dV looks equivalent to sensing during charging at a sensitivity of 13-15 mV dV. Not terrible but I think it makes it much more understandable why the C-9000 is missing charge termination on cells that other chargers handle fine.

BTW, I ran the test on different fully charged cells charged individually at 2000 mA multiple times and they all look the same.

Now a look at four Energizer 2500 AA charged from a discharged state at 2000 mA.

http://123pichosting.com/images/901Maha dV test 7 2000 mA 4 cells Slot 3 All data.jpg





And zoomed in on the end… 

http://123pichosting.com/images/8064Maha dV test 7 2000 mA 4 cells Slot 3 Zoomed.jpg





So why did the charge even terminate??? The cell voltage seems to have leveled off but didn’t drop. The peak cell voltage is even lower than in the first charge graph at 1000 mA. (Hope you’re reading this Tom…)

Frankly I have no way of knowing why it terminated there. I’m reasonably sure it could only have been on the basis of temperature. I wasn’t trying to measure temperature closely to avoid disturbing the connections to the meter. However, I checked it right after termination and the cell temp was 138 deg F. I strongly suspect it terminated either on the basis of max temperature or dT/dt. 

I ran this test twice, once each on slots 2 and 3 and both results were the same. The surface of the charger gets a LOT hotter when charging 4 AA cells at 2000 mA than any of the other tests. I measured temps up to 125 deg F aiming my IR thermometer at the charger surface between slots 1 and 2 and slots 2 and 3. I think that contributes most of the cell heating that we’re seeing. It certainly doesn’t appear to be caused by significant overcharging of the cells although it’s worth noting that Sanyo’s data shows the –dV inflection moves out to higher overcharge levels as cell temperature increases.

I think Maha might be able to improve things a bit by moving the power transistors with a PCB revision so none of them are located under the charging slots. More case venting would also help. An internal fan would be a major improvement but probably requires a completely new case design.

A few final thoughts before I run for cover from Tom. 

Things are only going to get worse with higher ambient temps as summer rolls around. Stretches of 100+ F weather are common where I live and I find the heat more manageable if I allow the house temps to go up…not to mention avoiding insanely high electric bills…

I’ve thought about the possibility that the higher load of charging 4 cells at 2000 mA and the resultant much higher internal temps may be affecting the charger’s ability to deliver current and leading to the “flat top” on the last graph. It’s possible but probably not likely and I have no way to explore it. Someone with an oscilloscope and current probes might. 

Now where’s my Nomex suite???? 

I hope some folks find this data interesting. Comments and questions welcomed although I'd request folks who aren't familiar with PWM etc sit this one out and follow the comments from the folks who are.

Mike

PS I'd love for somebody with a digital scope to try and verify my results at least qualitatively. 8 bits probably won't cut it but 10 or 11 bits of resolution should work if it can be set up over a 0-2V range. You could get by with less bits of resolution if you float the scope and use a charged battery to offset the signal ground from the C-9000 cell ground and use a lower voltage range.


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## wptski (Jan 13, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike abcd:

PWM is used to increment the current level just as the BC-900, C808M and many other chargers. A cell temperature of 138F isn't anything as I've measured them well above 140F with the metal sensor between the cells being at 125F. This is still below the 131F cutoff stated by William Chueh. It would seem that by the time that sensor reached 131F the cells could well be above 150F!

EDIT:

Trying to measure cell voltage on the OFF pulse is hard to do. Trying to show it as a graph is very hard to do!!


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## 3rdDerivative (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Wptski

If you know, on the other chargers that use the PWM, do they also read voltage at rest? I assume yes. It is just inherent with the design.

Also, could this is be sampling rate issue that is not fast enough to see the -DV event? Or a possible fatal combo of both issues i.e. using resting voltage and missing a sample? Again, I would assume no, since I thought I read that the -DV lasted a few seconds. And are to believe the sampling rate would be that slow.

But just wondering. Thanks


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## wptski (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



3rdDerivative said:


> Wptski
> 
> If you know, on the other chargers that use the PWM, do they also read voltage at rest? I assume yes. It is just inherent with the design.
> 
> ...


I don't know how other charger work as far as measuring -DeltaV, we're not given that information. I've tried to see/read/measure it on other chargers but never could get a handle on it but probably never went about it correctly. The higher the current, the higher the duty cycle or longer the ON pulses and the shorter the OFF pulse! It's anybody's guess here!


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## wptski (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Mike abcd questioned the results of my 2A tests in Post#264, stating that the cells weren’t fully discharged but I know for a fact that they were! I wanted to repeat a test with some cells connected externally to see how much heating difference there was, so I used 2A charging rate. These are the same 2.3Ah Duracells used in the last two tests in the same slots too. Slot#3/4 are connected externally to the charger with wires and clamps. As you can see Slots#3/4 are much cooler that the others. I might add that "all" slots showed dT/dt several minutes before the DONE time.

I was surprised to see that this time the middle slots finished close to the others with Slot#4 being a bit behind. Why the difference before? If they weren’t fully discharged, it would be a problem with the C9000 discharge cycle. This test was done in my basement where the other tests were done upstairs where the temperature is about 8F higher. I guess the only way to prove it, is to rerun the 2A where I did it the first time!

Here’s the input charges and discharge capacities at 500ma.

Charge/Discharge
Slot#1 = [email protected] min/[email protected] min
Slot#2 = [email protected] min/[email protected] min
Slot#3 = [email protected] min/[email protected] min
Slot#4 = [email protected] min/[email protected] min

Slot#1






Slot#2





Slots#3/4


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## wptski (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Tom:

In one of your posts above where you mentioned adding thermal grease to the temperature pickup and using a heat gun to heat the negative end of a cell to 143F. The C9000 shut off for high temperature then? Did it give a error on the screen?

I've had IR images that show cell temperatures higher than 143F and I think they are posted above somewhere but that didn't stop the C9000.

You had the wrapper melt on one of your cells. If you would have had the thermal added before that, it wouldn't have happened, probably not?

EDIT: That's Post#166 and the negative end of Slot#3 is at 143F. Maybe some thermal grease would help!


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## SilverFox (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Mike,

Nice graphs…

Is it possible to zoom in on both the “on” voltage and the “off” voltage on the first graph. Looking at the big graph, I see roughly a 15 mV drop in the “on” voltage while the “off” voltage is showing the 5 mV drop.

Can you confirm this?

Your “peak voltage” termination graph is interesting. It appears to have a different charge slope than your – dV graph. I wonder if there is some kind of moving average at work in the termination algorithm…

I checked the temperatures of some Titanium 2400 mAh cells while charging 4 cells at 2 amps. With the stock unit, I am getting around 142 F, with the charger removed from the case, I am getting around 133 F.

Tom


----------



## SilverFox (Jan 14, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*

Hello Bill,

I was waving the heat gun along the lower end of the cells, while trying to keep it away from the display. The purpose of the test was to see if the charger would shut off at high temperature, what it would do when it shut off, and lastly, a rough idea of the shut off temperature.

I was holding the heat gun in one hand and my IR probe in the other. There probably is some error in making a measurement in this fashion...  

The test was done after I added the thermal grease.

I had just started charging some cells that were completely discharged, so there would be no problem with cell charge termination interfering with the test.

When the contact strip heated up, the charge cycle indicated "Done" and the charge stopped. The only indication of something being wrong is that the total charge time was only something like 10 minutes.

I did not see any error message. The charger simply went from "Charging" to "Done."

Tom


----------



## EngrPaul (Jan 14, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Just an update-- I've tested 52 cells (~half AA, half AAA) in the Recharge & Analyze mode, 16 in the break-in mode. 

Of all of these, only the two older AAA's failed to terminate, it just so happens I tested my oldest batteries first.

I have not been able to follow Bill and Tom's detailed discussion. I do not mind these being here. In fact, I'm going to change the title to a more appropriate name.


----------



## Mike abcd (Jan 15, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



SilverFox said:


> Hello Mike,
> 
> Nice graphs…
> 
> ...



Hi Tom,

Sorry for the delay in replying.

The meter software allows saving the data to a file but doesn't allow reloading it. You can zoom in on the jpg and get a pretty accurate value though. The "on" -dV appears to be .015-.017 V, about 3x the -dV measured in the "off".

The slopes are different in the two 2000 mA tests posted because the first was just a "top off" while the second one on four cells @ 2000 mA was a full charge. My apologies for not being clear about that. I also did a full charge on one cell @ 2000 mA but apparently forgot to save the results. However, the charge termination "off" -dV was 5-6 mV and the "on" -dV was ~13-16 mV, basically the same as the top off test although the "voltage ramp up" and "slope" was like the four cell full charge @ 2000 mA test.

With only one cell @ 2000 mA, the C-9000 seemed to terminate "normally" on -dV. With four cells at 2000 mA, cell heating is much higher and the C-9000 appears to terminate on max temp or possibly some value of dT/dt much higher than the standard 1 deg C / min "spec". Sanyo's data shows -dV moves out to higher charge levels as cell temperature increases so this makes sense to me. I suspect the -dV would still have happened if the C-9000 had continued the charge although the cell temps would have been even hotter than the 138 F I measured and the cells would have received even a higher over charge.

Thanks for running the C-9000 open case test. I'd hoped for more of a drop in cell temperatures...

Here's another test you might find interesting, an Energizer 2500 AA @ 500 mA charge on the BC-900. I drained a few 100 mA (300-400???) from it fully charged for this test. The charge rate works out to ~.22 C of C-9000 measured capacity 

http://123pichosting.com/images/3729BC900 Passed dV 500 mA.jpg




http://123pichosting.com/images/9351BC900 Passed dV 500 mA end zoomer.jpg




The BC-900 appears to have terminated the charge based on a -dV of 5 mV on the "on" pulse and at most 3 mV on the "off" pulse. I'm pretty impressed by this. It's got me considering purchasing another BC-900 and hacking it to charge cells externally based on the cell temperatures Bill got in his test of the C-9000 charging external cells. Based on this one test, the BC-900 -dV seems superior to the C-9000's.

I also found it interesting that my meter seemed to pick up mostly the "off" voltage until the cell voltage "slope" got smaller near the end of charge. At 500 mA on the BC-900, I was expecting to see results more like the C-9000 test @ 1000 mA with more samples on "off" but still tracking the "on" pretty well. The BC-900 might actually be doing something smart with the PWM period or charge current when the cell voltage slope gets smaller that aids it in detecting the -dV.

I'll try looking st this more when I get time. Makes me really wish I had an oscilloscope to look closer at the BC-900 charge.

BTW, I now consider the Energizer 2500 cells I'm using well abused after all the heating they've endured in 15+ C-9000 test cycles. I may try a fresher cell and see if I can duplicate my earlier results with the BC-900 terminating on -dV at under a .1 C (200 mA) charge rate.

Mike


----------



## Mike abcd (Jan 15, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



wptski said:


> Mike abcd questioned the results of my 2A tests in Post#264, stating that the cells weren’t fully discharged but I know for a fact that they were! I wanted to repeat a test with some cells connected externally to see how much heating difference there was, so I used 2A charging rate.
> ...



Bill,

Please accept my apologies if it seemed like I was questioning your honesty or competency. I wasn't and have found your contributions here very valuable.

I was just trying to figure out why your earlier 2000 mA seemed to show an earlier charge termination on slots 2/3 and was wondering if it was repeatable.

I thought that explained why you'd seen lower temps on slots 2/3 while my tests have consistently shown higher temps. Again my apologies for not expressing my thoughts better!

I also want to thank you for posting the temperature data with the cells connected externally. I've been blaming the C-9000 charger circuitry heating for the high cell temps we're seeing but I didn't expect the difference to be so large while using -dV termination. It's got me seriously contemplating hacking an existing charger for external charging stations while I continue to wait for a charger that "works right".

Mike

PS If you post the make/model of your oscilloscope, I'll take a look at the specs and see if I can come up with any ideas on how you might be able to measure both the "on" and "off" voltages better.


----------



## NiOOH (Jan 15, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Hi Mike.
Thanks for the great results here and earlier as well. Can you please run the same test with fully discharged cells, i.e. tracking the voltage from the begining of the cycle and at higher currents as well. 
NB: I am also begining to change my opinion about BC900, especially considering its price..


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## Mike abcd (Jan 15, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



NiOOH said:


> Hi Mike.
> Thanks for the great results here and earlier as well. Can you please run the same test with fully discharged cells, i.e. tracking the voltage from the begining of the cycle and at higher currents as well.
> NB: I am also begining to change my opinion about BC900, especially considering its price..



Were you requesting BC-900 runs? I'm probably going to run a couple/few more but I might not be able to do them right away and I probably should post them in another thread.

BTW, I never thanked you for the info you posted on the Lenmar Mach 1 charger. It was appreciated. I was aware that it did a top off charge but I don't like not knowing when it's complete and that I couldn't tell if it was overcharging. I have noticed that the cells seem to get warmer (but not hot) during the top off than they do during the fast charge.

Mike


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## wptski (Jan 15, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Mike abcd:

No problem! You were correct as there was something wrong with the first 2A test. Either the cells "didn't" fully discharge or it something to do with room temperature differences between the two tests. I will repeat the 2A test when time allows.


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## SilverFox (Jan 15, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Hello Mike,

Very interesting...

If the "on" voltage is used for termination, it will be more sensitive than using the "off" voltage. I believe my Schulze uses the "on" voltage and a termination value of 3 mV/cell for NiMh chemistry.

Tom


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## wptski (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Tom:

It probably doesn't use the ON pulse for termination as it's the cell voltage that does the drop. The Triton's screen shows current go to zero and the voltage shown lower than voltage when current is ON as it checks cell volatge. There'd be no reason to do this other than being used for termination. Altough, the period it does this isn't very often.

The C9000 checks cell voltage on the OFF pulse but what does it compare it to? The last OFF pulse?


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## SilverFox (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Hello Bill,

I have watched several cycles on the Schulze. It always seems to terminate on a drop in the "on" voltage. I believe it uses the difference in "on" and "off" voltage to do an internal resistance check of the battery and adjusts the charging current to prevent heating.

Tom


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## wptski (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



SilverFox said:


> Hello Bill,
> 
> I have watched several cycles on the Schulze. It always seems to terminate on a drop in the "on" voltage. I believe it uses the difference in "on" and "off" voltage to do an internal resistance check of the battery and adjusts the charging current to prevent heating.
> 
> Tom


Tom:

It may compare to adjust current but in any documents from Duracell, Sanyo, etc. have you read anything that states that -DeltaV is a drop in charger voltage? The charger may be fast than the software or your eyes.

I've been trying different ways to capture -DeltaV on a scope graph with the C9000. I've caught a drop but timing is so fast, the smallest division isn't small enough to catch the event. It does but measures over 10mv I'm trying other ways but it isn't going to be a graph but just pulses and one OFF will be compared to another OFF pulse. I forget whatever I was trying last night and I lost power due to a ice storm. Hey, keep your storms to yourself!


----------



## Mike abcd (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Tom:
> 
> It may compare to adjust current but in any documents from Duracell, Sanyo, etc. have you read anything that states that -DeltaV is a drop in charger voltage? The charger may be fast than the software or your eyes.
> 
> I've been trying different ways to capture -DeltaV on a scope graph with the C9000. I've caught a drop but timing is so fast, the smallest division isn't small enough to catch the event. It does but measures over 10mv I'm trying other ways but it isn't going to be a graph but just pulses and one OFF will be compared to another OFF pulse. I forget whatever I was trying last night and I lost power due to a ice storm. Hey, keep your storms to yourself!



Bill,

Since the charger is a currrent limited source, the voltage read under charge is the battery voltage at that charge current. None of the manufacturer's docs I've read even discuss pulse charging or "pausing" charging to check battery voltage. The voltage vs capacity curves are also all consistent with measuring the battery voltage while charging.

What oscilliscope do you have? From what I've seen, the battery voltage -dV is a relatively slow event and slowing down the sampling might still give you enough random captures of the "on" and "off" levels to get a good picture of the levels involved. That seems to be why my crude method seems to present a (hopefully) valid picture of what's happening.

Mike


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## wptski (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Mike abcd:

Why does a non-pulsed current charger like a Triton stop charging and display the cell(s) voltage then?

The other problem is that my Fluke 199B is picking up a variation 10-15mv at times even on the OFF pulse if I look at the individual pulses as opposed to trying to graph it which is the best way to show n tell. I'm not a scope expert user either! I'm a mechanic by trade with military electronics background, most all I have forgotten.


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## Mike abcd (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Mike abcd:
> 
> Why does a non-pulsed current charger like a Triton stop charging and display the cell(s) voltage then?
> 
> The other problem is that my Fluke 199B is picking up a variation 10-15mv at times even on the OFF pulse if I look at the individual pulses as opposed to trying to graph it which is the best way to show n tell. I'm not a scope expert user either! I'm a mechanic by trade with military electronics background, most all I have forgotten.



I haven't really looked at the Triton. Way too expensive for my NiMH use and I only use "balance chargers" with independent channels on my LiPo packs. Triton offers a "bleed type" balancer but I never found them cost effective there either. Seems a decent solution for folks using the BIG LiPo packs but I like the smaller/mid sized helis as it's far easier to find place to safely fly them.

If you post the triton model # and a description of when it's pausing though, I'll take a look and see if I can hazard a guess.

Consider this though. The -dV drop is caused an increase in the battery temperature. NiMH battery voltage drops when temperature increases. The increase in the battery temperature is caused by the charge current into the battery which has reached and slightly gone over 100% capacity. No charge current in -> no temperature increase -> no voltage decrease.

Now this is obviously a simplistic view but I think it's basically valid. The C-9000 still sees a -dV since the temperature increase due to the "last" charge pulse takes time to "propagate" through the cell, etc, it just appears significantly less sensitive in sensing -dV than measuring voltage while the charge current causing the cell heating and voltage drop is occurring.

I'd guess the variations you're seeing on the off pulse might be due to cross coupling between the charge channels although I'm surprised I didn't see them. I'd be VERY interested though if you can try a slower sampling "graph" test to see if you get results similar to mine. I'd also be interested in seeing some pics of "clean" off cycles vs the ones with the 10-15 mV variations. You might be picking up some high frequency noise that my meter and the C-9000 both average out during the sampling period. I suspect both my meter and the C-9000 are using some form of integrating A/D converter.

Mike


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## wptski (Jan 16, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Once a cell reaches passes the dT/dt point on to ZeroDelta heading toward -DelataV the temperature is still climbing at maybe 4-5F/min. It continues to heat up even after termination.

A "clean" OFF pulse would have to be someother charger. The scope will do averaging too but still there's a bit of variation shown on the OFF pulse, more than its said 5mv value.

If -DeltaV is caused by a increase in battery temperature, what happened in the oddball Slots#2/3 2A test? Conditions for dT/dt were never met! The test was flawed "somehow" but it terminated without any rapid heating.

EDIT: Captured some stuff charging a 2.5Ah cell at 1A the second time. The first time I lost power. It looked pretty good at the start but at the end, the time compression messed it up a bit. Still clearly looked like a 16mv drop on the OFF pulse but how do you know if it didn't drop the required 5mv in between? Shouldn't it be a drop of at least 5mv? Who's to say that it doesn't drop more in that approx 500ms??

I have three software programs that I can use with my Fluke 199B and currently having a problem downloading TrendPlots into one of them. This programs is a bit better than the Fluke software when using the cursors to get values. I've emailed the author for help.


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## wptski (Jan 19, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Mike abcd:

Okay here's a 2Ah PowerEx AA charging at 1A on the C9000. Look at the cursor values at the right, value of dY, the difference of the two OFF pulses. I finally figured a scope setup to show it well but I have to be there when it happens!  If not, it starts saving more screens and compressing them which distorts everything.


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## VidPro (Jan 20, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

"""Is any one besides Mike (and me) concerned about the 2 hour 100ma, since the charger seems NOT to use dT/dt?"""

i wouldnt for a AA battery of at least 1200+ capacity as that would be within the overcharge rate for it. but for an AAA battery , basically any of the capacity that is now available, that might be to close to the overcharge rate.

IMO any Voltage drop or high temp rise significates the "end of charge" because at that point the battery is done being charged, it is heating , expending waste heat, as opposed to "accepting" the power being tossed at it.
and the voltage drops ONLY at high rates, because only at high rates is it going into overcharge, overcharge that is past the ability for it handle the overcharge.

so IMO (and mabey only my opinion in the whole world) the detection method, is testing for damage, the damage occurs for a few seconds/minutes, and the "smart" charger spots this , as it is easily spotted by modern electronic microprocessors, and stops the charge.

NOW if the thing is going to go into a "trickle" or Top-OFF or pulse holding charge, it should do so at a rate that is WELL below overcharge rate, especially if it just HIT overcharge.

there are 2 things that can occur to improve this stuff, both of which were not going to see happen.

1) stop the charge prematurely, and go "dumb slow" and trickle ,or trickle pulse, the battery up to full. were not going to see that, because someone will analise that the charger doesnt get the battery to full, untill you wait for it to finish , awww, to bad.

2) after reaching overcharge levels (to you guys that is the voltage drop) WAIT at least a few minutes before continuing with the topping or trickle charge, that will maintain the charge as long as it is on the charger,but not continue to be so harsh on it , when it just reached overcharge.

a consumer charger can go into a very slow trickle , or pulse trickle that is far below the overcharge rate, and close to the self discharge rate for the ENTIRE time it sits on the charger.

SO
if its a actual topping off charge and charging had been prematurly terminated, then its ok at 100ma. but you said charging had reached delta borke or whatever you want to call it, if the cell is dropping in voltage, hey its quite done with having a hard charge hitting it, and 100ma OC for a 850-1000ma AAA doesnt sound good for it.

if they had a AA or AAA Switch, or button, then i would go with mabey 25ma for AA and 10ma for AAA for a holding charge after proper termination of that type.
IF
they had PRE_Terminated before overheat and overcharge, then they could do a topping charge to finish charging the cell.

so IMO, that seems incorrect.
i appretiate all the work you guys did, and the pics and studies. you know i would still USE this charger, but i would use it at "sweet spots" for proper detection of the type of cell i was using, and i really would HATE that 100ma on my AAAs, they have a hard enough time on "universal" AA chargers that can barely do AAAs proper too.

from battery U
http://www.batteryuniversity.com/images/partone-11.gif

again all of my post is opinion, but you asked if anybody else had a problem with that.


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## flashlight (Jan 20, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

OK so I flunked Battery U & I've got a headache now.  What I want to know since I already got a MH-C9000 on the way to me (and for which I paid too much for too! ) is - is this a good charger to have & safe to use or do I have to watch out for this or that & have a degree in electrical engineering, electronics, etc in order to correctly & safely use it? :huh2:


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## 3rdDerivative (Jan 21, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



VidPro said:


> """Is any one besides Mike (and me) concerned about the 2 hour 100ma, since the charger seems NOT to use dT/dt?"""



Yes, I expressed the same concern after Mike posted it. However, someone dismissed it as a concern, since the solution is to remove the cells after charging.


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## tacoal (Jan 21, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Mike abcd:
> 
> Okay here's a 2Ah PowerEx AA charging at 1A on the C9000. Look at the cursor values at the right, value of dY, the difference of the two OFF pulses. I finally figured a scope setup to show it well but I have to be there when it happens!  If not, it starts saving more screens and compressing them which distorts everything.


 
So the C90000 uses 0.5 Hz charging cycle while the BC-900 uses 51Hz...


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## jtr1962 (Jan 21, 2007)

*Re: MH-C9000 Two bays not terminating AAA charge @.7C (4C and still going)*



Mike abcd said:


> Now I understand why Maha used PWM pulse charging, as it’s cheaper to implement variable rates on multiple independent stations. It’s also probably cheaper and/or simpler to measure the voltage under rest. However, it seems to significantly reduce the potential to sense –dV. I’m sure some chargers are far worse. But sensing during rest at a threshold of 5 mV –dV looks equivalent to sensing during charging at a sensitivity of 13-15 mV dV. Not terrible but I think it makes it much more understandable why the C-9000 is missing charge termination on cells that other chargers handle fine.


I remember reading that the reason for using PWM charging as opposed to true constant current is better charge acceptance, especially at the low charge currents that the MH-C9000 might be using when forming cells. In other words, less of the charge energy becomes heat if you use a 2A current at a 12.5% duty cycle (average current of 250 mA) instead of a constant DC current of 250 mA. Whether long-term this PWM is worse for the cells I don't know.

As for the decision to sense the current during rest, it probably makes sense because even a small change in battery position during charging might change the measured voltage enough to cause false termination. For example, if you put your hand on a cell being charged to feel how hot it is getting you might well inadvertently rotate or otherwise move the cell a bit, perhaps causing a slight voltage change. Sensing during rest avoids this problem since contact resistance is out of the equation. What puzzles me though is that it should be possible to very accurately sample cell voltage during rest, and thus use the point of inflection to terminate fast charge. This is the point at which the slope of the voltage versus time graph goes from positive to negative, or put mathematically when dV/dt = 0. Doing this would of course mean a less complete fast charge, but following it by a 100 mA topping charge for 2 hours would be safe, even for AAA cells.

All that being said, it might be nice to have a provision to enter cell capacity before charging, and use 1.2C as the point to terminate fast charge if the charge fails to terminate normally. Also, the absolute maximum termination temperature seems to be set too high based on the observations in this thread. Perhaps it's a quality control problem-maybe the thermistors just need some thermal paste so they make good thermal contact with the metal bands the cell sits against. I haven't taken my charger apart so I don't really know if this is the case.

Very interesting thread. I haven't had time to read it entirely but I plan to, and may have additional comments when I do.


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## wptski (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

tacoal:

Yes, .5Hz for the C9000 and 51Hz sounds familiar for the BC-900.


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## tacoal (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> tacoal:
> 
> Yes, .5Hz for the C9000 and 51Hz sounds familiar for the BC-900.


 
wptski,

This is like other Maha's charger using slow charging cycle.

I think this might be the reason why the batteries are not hot as ones in BC-900 towards the end of charging with the same charging rate.


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## wptski (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

I wouldn't call +140F cool, which I've seen on the C9000. I've never checked the BC-900 prior to getting my v33 replacement, so I can't comment on the max temperature of a v32 version. Seems like I did a comparison of inserted against external connection on the BC-900 and it was 15F cooler whereas the C9000 is 30F cooler!


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## SilverFox (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

I ran a check on what happens to AAA cells during the top off charge at the end of the charge cycle.

I used 700 mAh Saft AAA NiMh cells and charged them at the default 1 amp rate. A few minutes after the charge completed, the voltage dropped to 1.42 volts. It seems there is a "resting" period before the top off charge starts.

In 15 minutes the voltage was at 1.46 volts, and it stayed there for two hours. At the end of the two hour top off, the cells were at 88 F, and the voltage dropped back down to 1.42 volts.

The 100 mA top off charge rates represents a 0.14 C rate for these cells.

I was expecting to see a drop in the voltage because of the cell being charged on top of the full charge. It seems these cells "accepted" the additional charge without problems.

Tom


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## wptski (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Tom:

Look at Post#366. The smaller pulses are the topoff, it starts right after it shows DONE. I have no idea what your seeing as to the voltage. Topoff is a very short ON pulse, maybe the displayed voltage isn't accurate for some reason?


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## SilverFox (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Hello Bill,

Yes, I saw that. Have you ever looked out 3 - 5 minutes after "Done?"

Tom


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## wptski (Jan 22, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Tom:

Yep, I'm the person the posted that the topoff charge went for two hours instead of the listed specs of one hour.


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## 3rdDerivative (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Found this site (Robert's Photography Blog) that has tested the C9000 and had termination problems also. He got this reply back from Maha on the issue. 

"Update Jan. 18th: Maha’s response to the problem of charge termination is, “if the charging was done at 0.2C and the MH-C9000 will not terminate properly with new or older batteries, please proceed to use the rate at 0.5-1C “. This response is simply unacceptable. The same batteries can be charged at slow or fast currents with the BC-900. Why should I have to wait 6-8 hours to find out whether of not the MC-C9000 will terminate charging? Then, set it up again. Also, charge rates of 0.5-1C (C=capacity) are detrimental to battery longevity."

I called TD before I returned my unit about two weeks ago. The guy at TD claimed he had not heard of any problems. And he had never heard of CPF either. So I figured this issue with C9000 will takes months to resolve. Maha first have to acknowledge a problem and then be willing to fix it.

I got a BC-900 when Amazon had them at $35. I also got a Maha C800s. So far both seem to work fine. And I have charged several set of batteries of varying ages in the BC-900 at 200 MA. So far the BC-900 had terminated without issues.


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Mike abcd:
> 
> Okay here's a 2Ah PowerEx AA charging at 1A on the C9000. Look at the cursor values at the right, value of dY, the difference of the two OFF pulses. I finally figured a scope setup to show it well but I have to be there when it happens!  If not, it starts saving more screens and compressing them which distorts everything.



It's pretty hard to tell from the posted pic but you might just be dealing with the resolution limits of the oscilloscope. I took a quick look at the Fluke 199B manual and it looks like it has 8 bit A/D (256 interval) converters in the oscilloscope section.

Mike


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



SilverFox said:


> I ran a check on what happens to AAA cells during the top off charge at the end of the charge cycle.
> 
> I used 700 mAh Saft AAA NiMh cells and charged them at the default 1 amp rate. A few minutes after the charge completed, the voltage dropped to 1.42 volts. It seems there is a "resting" period before the top off charge starts.
> 
> ...



Tom,

There isn't any resting period before the top off. The initial voltage drop after the fast charge is just due to the charge rate drop from 1000 mA to 100 mA. The voltage level then slowly climbs back up due to the over charge but the -dV was already hit during the fast charge and won't happen again.

200 mAH after -dV termination is a hefty over charge on a 700 mAH cell IMHO.

Mike


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## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



Mike abcd said:


> It's pretty hard to tell from the posted pic but you might just be dealing with the resolution limits of the oscilloscope. I took a quick look at the Fluke 199B manual and it looks like it has 8 bit A/D (256 interval) converters in the oscilloscope section.
> 
> Mike


Mike abcd:

In respect the what? Or what are you trying to imply? You don't agree with the graph?


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## bmoorhouse (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



3rdDerivative said:


> Also, charge rates of 0.5-1C (C=capacity) are detrimental to battery longevity."



That's something I have been asking about for a couple of weeks. 

Will the 0.5-1.0 C charging rate (which is basically Fast and Faster) damage the batteries over time and effect their longevity? Along the same lines, I understand the C9000 slightly overcharges the cells with every charge. Won't that also have some long term effects on the batteries longevity?


----------



## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

The -deltaV method of termination is used by most chargers and does overcharge by it's definition. The C9000 doesn't do anything different in that respect compared to many other chargers on the market today. Charging rates of .5-1C are common practice and better with the newer high capacity cells to insure proper -deltaV termination.

I just wonder if their 3-5mv termination voltage drop is a bit too small to be detected repeatedly??


----------



## tacoal (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

it looks like confusing about the graph. If Mike said is true that the 199B only has 8 bit A/D, then the resolution is for that graph is about 12mv (1.55*2/256). This mean the scope cannot tell the difference less than 12mv. But the difference showed on the graph is 3mv. So either the 3mv is faked one or the scope use 10 or more bit A/D converter.

A 10 bit A/D in a 2V range will give you about 2mv resolution. Considering the various error and noise (PWM is a noisy guy), the best resolution might be about 2 to 3 LSB, that's about 4 to 6 mv. I think BC-900 uses the value around this.


----------



## bmoorhouse (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> The -deltaV method of termination is used by most chargers and does overcharge by it's definition. The C9000 doesn't do anything different in that respect compared to many other chargers on the market today. Charging rates of .5-1C are common practice and better with the newer high capacity cells to insure proper -deltaV termination.


 
Thanks for the reply. But I have to ask then about the Maha 800S. It uses 500 mah and 1000 mah, which would be 0.25C or 0.5C for a 2000 mah battery and lower for higher capacity batteries, yet I haven't heard any reports of it missing a termination with batteries of any capacity.

Like others, I think MAHA has given us a good analyzer, but the charging and terminiation circuitry in this C9000 is inferior.


----------



## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

tacoal:

I think that Mike abcd really wanted a graph showing 10-15mv drop because that's what he believes in! I actually can/could move the cursors around to show a 1mv dV too but 3mv was the max. I could also post a graph which showed the charging voltage or ON pulse start a long slow drop way before termination.

It seems like there are some people that are always going to have their beliefs about this charger and it don't matter whatever or whoever posts anything I like to keep an open mind.


----------



## 3rdDerivative (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



bmoorhouse said:


> Thanks for the reply. But I have to ask then about the Maha 800S. It uses 500 mah and 1000 mah, which would be 0.25C or 0.5C for a 2000 mah battery and lower for higher capacity batteries, yet I haven't heard any reports of it missing a termination with batteries of any capacity.
> 
> Like others, I think MAHA has given us a good analyzer, but the charging and terminiation circuitry in this C9000 is inferior.



This is my problem too. If .5C or 1C is the recommendation now per Maha. Then why does the C800s, which only became available last fall, not "support" Maha own recommendations for cell like 2700 or 3000mah. And still seems to work as other chargers like BC-900 with these higher cells at much lower than .5C levels?

Also, if negative delta V overcharges by definition, which it does. Why then run a topoff? It just does not make sense, unless the charger was assuming most terminations would not be done by -DV. Surely Maha understand how -DV works. 

Something is not right.

Last fall when I saw the C9000 marketing material, I just assumed the C9000 would have every termination method and safety feature known to man. Perhaps my over reading the hype about the super charger. But I did not expect worst performance than a C800S or BC-900 regarding charging ability or safety.


----------



## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

The 800 Series may use a bit higher -deltaV? In using the 3-5mv on the C9000, they added topofff to insure a full charge? Both are pure guesswork though!


----------



## 3rdDerivative (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> The 800 Series may use a bit higher -deltaV? In using the 3-5mv on the C9000, they added topofff to insure a full charge? Both are pure guesswork though!



Perhaps, but as I understand, the reason for the drop in voltage is the battery is charged. You get the -DV and the associated temperature increase when the battery is overcharged. This is just way -DV work. You overcharge. Always. Not need for topoff- ever, as I understand.

I think the common understanding is the overcharge is actually around 120% or even higher for -DV.


----------



## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



3rdDerivative said:



> Perhaps, but as I understand, the reason for the drop in voltage is the battery is charged. You get the -DV and the associated temperature increase when the battery is overcharged. This is just way -DV work. You overcharge. Always. Not need for topoff- ever, as I understand.
> 
> I think the common understanding is the overcharge is actually around 120% or even higher for -DV.


What happens if the -deltaV is set to say, 20mv? What the difference? What's going to happen?


----------



## 3rdDerivative (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> The 800 Series may use a bit higher -deltaV? In using the 3-5mv on the C9000, they added topofff to insure a full charge? Both are pure guesswork though!



Perhaps, but as I understand, the reason for the drop in voltage is the battery is charged. You get the -DV and the associated temperature increase when the battery is overcharged. This is just way -DV work. You overcharge. Always. Not need for topoff- ever, as I understand.

I think the common understanding is the overcharge is actually around 120% or even higher for -DV.


----------



## NiOOH (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> What happens if the -deltaV is set to say, 20mv? What the difference? What's going to happen?


 
The higher -dV value, the more overcharge there will be. No overcharge is at 0dV i.e. peak voltage. Anything after that is overcharge.


----------



## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

NiOOH:

Correct, except I've never seen anything mentioned about peak voltage. Oh! You mean ZeroDeltaV!!


3rdDerivative:

The -deltaV keeps dropping.


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## tacoal (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



3rdDerivative said:


> Also, if negative delta V overcharges by definition, which it does. Why then run a topoff? It just does not make sense, unless the charger was assuming most terminations would not be done by -DV. Surely Maha understand how -DV works.


Good point! I think it is for marketing since many people want to have the function of topoff and/or trickle charge after normal charger to keep the capacity at maximum.



3rdDerivative said:


> Last fall when I saw the C9000 marketing material, I just assumed the C9000 would have every termination method and safety feature known to man. Perhaps my over reading the hype about the super charger. But I did not expect worst performance than a C800S or BC-900 regarding charging ability or safety.


Yeah, we expected a perfect charger for its price after two years introduction of not-perfect BC-900, hoping that all the bugs in BC-900 should gone. Yes, C9000 has some good features over BC-900. However, some basic functions are not as good as those old guy.


----------



## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> tacoal:
> 
> I think that Mike abcd really wanted a graph showing 10-15mv drop because that's what he believes in! I actually can/could move the cursors around to show a 1mv dV too but 3mv was the max. I could also post a graph which showed the charging voltage or ON pulse start a long slow drop way before termination.
> 
> It seems like there are some people that are always going to have their beliefs about this charger and it don't matter whatever or whoever posts anything I like to keep an open mind.



Wow...I will admit I had expectations that I wouldn't get insulted or have words put in my mouth. So much for expectations. I'll work on keeping an open mind.

Let me try again Bill. My apologies in advance if you understand this stuff but your reply to my post and tacoal's attempt to explain it seems to show otherwise. Take a look on page 96 in your manual. "Digitizer Resolution - 8 bits, separate digitizer for each input".

That means the oscilloscope section uses 8 bit analog to digital converters to aquire the signal. An 8 bit converter gives values between 0 and 255. These 256 possible values are spread over the input range selected. For example, for a 0 to 255 V input range, the minimum resolvable voltage change would be 1 volt.

The *ONLY *thing I was saying in my reply was that 8 bits of resolution is not enough to accurately track changes of a few millivolts on a 2 V input range. I stated and intended *nothing *else. Please don't put words in my mouth.

My reply assumed your graph was done in your Fluke's oscilloscope mode and not using its' DMM section. According to the manual, the DMM section has much higher resolution listed as "5000 counts" (pg 103). In comparison, that's 12+ bits of resolution. I couldn't find the sample rate for the DMM mode. although the "Recorder" mode lists 5 per sec max in both DMM and scope for "trendplots".

Looking further, the graph you posted is showing a time difference between the 2 successive "pulses of 2.8 sec (dX). I didn't notice that before I replied. Since you were evidently sampling pretty slowly, you might have been using the DMM section and its' much higher resolution. That seems to explain that you had enough resolution to track voltage to sub mV levels. However it also means that your samples were acquired at a rate too low to accurately catch the voltage levels during the pulse transitions. That's the case with the graphs I posted. As I stated in my post, my sample rate was too low to catch every pulse high or low accurately and had to be viewed across a number of pulses to pick up the trend. looking at the variations (up and down) in the "on" (high) pulses in your graph, that seems to be the same situation in your graph although your apparent higher sample rate seems to do a bit better than mine.

-dV on NiMH is a relatively slow event that happens across 10s of seconds to minutes depending on the charge rate (C). The variation in a single off or on pulse you're seeing are probably either due to the sampling rate issues I mentioned and/or the short term voltage drop/rise that happens over time when the charge pulse is stopped/started. From my tests on both the C-9000 and BC-900, it appears that charge termination by -dV is determined from the voltage drop across multiple samples.

If my response is not clear, I'd appreciate it if you ask me to try and make it clearer but please don't make assumptions about my expectations again.

It would help if you posted your Fluke's settings (mode, time base, input range) along with the graphs. You asked for my comment so had to guess at the setup and that was reflected in my comment.

Mike


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



NiOOH said:


> The higher -dV value, the more overcharge there will be. No overcharge is at 0dV i.e. peak voltage. Anything after that is overcharge.



http://123pichosting.com/images/5367Sanyo dV graph.jpg




This graph from Sanyo's NiMH doc seems to show that even zero dV seems to occur at slightly over 100% charge. I'd guess about 105% from zooming in on it.

Mike


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## tacoal (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Please calm down, folks.

If my understanding is correctly, the 10 to 15 mv drop mentioned by Mike is from the maximum voltage, while 3mv drop mentioned by Bill is the voltage drop between the last two charging cycle. So 3mv is a part of 10 to 15 mv. Both of you are correct.

If the manufacture of NiHM battery charger looks the document Mike's mentioned, I think they will decide not to use negative voltage as the terminating criteria. It seems only 1C charging rate will generate good negative voltage.


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## tacoal (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



Mike abcd said:


> This graph from Sanyo's NiMH doc seems to show that even zero dV seems to occur at slightly over 100% charge. I'd guess about 105% from zooming in on it.
> 
> Mike


 
I think you mean the charging efficiency is 100% when you say this.


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## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



tacoal said:


> Please calm down, folks.
> 
> If my understanding is correctly, the 10 to 15 mv drop mentioned by Mike is from the maximum voltage, while 3mv drop mentioned by Bill is the voltage drop between the last two charging cycle. So 3mv is a part of 10 to 15 mv. Both of you are correct.
> 
> If the manufacture of NiHM battery charger looks the document Mike's mentioned, I think they will decide not to use negative voltage as the terminating criteria. It seems only 1C charging rate will generate good negative voltage.


Not sure if Mike ever mentioned 10-15mv drop above anywhere. I just used that value to mean "something" other than the 3 or 5mv that somebody, maybe SilverFox mentioned.


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## wptski (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*

Mike abcd:

I used the scope mode TrendPlot not meter mode for the graph with a setting of 500mv at 500microseconds. I tried various ways of showing this and tried to come up with the best way but it's still not good enough or to say my scope isn't good enough. Okay no graphs, I'm done!


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



tacoal said:


> ...
> 
> If the manufacture of NiHM battery charger looks the document Mike's mentioned, I think they will decide not to use negative voltage as the terminating criteria. It seems only 1C charging rate will generate good negative voltage.



-dV is greater at 1C than lower rates but still very detectable even at .25 C from what I've seen on a BC-900 500 mA charge on a 2500 mAH Energizer. The scale of the graph is too small to see 10 mV.

Mike


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Not sure if Mike ever mentioned 10-15mv drop above anywhere. I just used that value to mean "something" other than the 3 or 5mv that somebody, maybe SilverFox mentioned.



I observed a 12-13 mV decrease in the "on" portion of the charging pulse when the C-9000 terminated on a 4-6 mV decrease in the "off" portion of the charging pulse. That was for a 1000 mA charge rate on Energizer 2500s.

The differences in voltages were from the peaks observed in the "on" and "off" values to the values at termination.

That's the only observation of that type I remember seeing posted in this thread.

Mike


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## Mike abcd (Jan 23, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> Mike abcd:
> 
> I used the scope mode TrendPlot not meter mode for the graph with a setting of 500mv at 500microseconds. I tried various ways of showing this and tried to come up with the best way but it's still not good enough or to say my scope isn't good enough. Okay no graphs, I'm done!



Bill,

Unless I'm badly mis reading your Fluke's specs, the 8 bit resolution of the scope mode is probably too low to offer a maningful picture of -dV termination. I think it would take 10 bits at a minimum.

I didn't read the rest of the manual but suspect the displayed data may be interpolating between actual measured values making it look like more resolution is available.

The manual seemed a bit vague on the sample rate in the DMM mode but at "up to 5 samples per sec", it's a lot faster than my meter and has a bit more resolution (5000 vs 4000 counts). I suspect you could get better graphs than mine if you tried to track both the on and off voltages at higher charge rates. You'll still get lots of samples randomly between the on and off charge pulse levels but should still have plenty to accurately track the voltages.

Sorry to see you give up on graphing the charge cycles but I'm about to do the same thing myself. I've seen enough to decide my C-9000 is headed back to TD.

Mike


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## wptski (Jan 23, 2007)

Mike:

Try 2.5GS/s sampling rate, 27,500 samples for scope record at 500 microseconds in this calculator: AutoNerdz 

I haven't given it up, I just gave up posting them!


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## wptski (Jan 24, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



tacoal said:


> it looks like confusing about the graph. If Mike said is true that the 199B only has 8 bit A/D, then the resolution is for that graph is about 12mv (1.55*2/256). This mean the scope cannot tell the difference less than 12mv. But the difference showed on the graph is 3mv. So either the 3mv is faked one or the scope use 10 or more bit A/D converter.
> 
> A 10 bit A/D in a 2V range will give you about 2mv resolution. Considering the various error and noise (PWM is a noisy guy), the best resolution might be about 2 to 3 LSB, that's about 4 to 6 mv. I think BC-900 uses the value around this.


The listed low end sensitivity for the model is 5mv. So the software downloads from memory and then what, fudges it? Not sure if I can get a 3mv drop on the scope itself as I didn't try that.


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## tacoal (Jan 24, 2007)

*Re: MH-C9000 Termination Issues [Renamed title]*



wptski said:


> The listed low end sensitivity for the model is 5mv. So the software downloads from memory and then what, fudges it? Not sure if I can get a 3mv drop on the scope itself as I didn't try that.


 
Hi Bill,

After checking the manual and look again your graph, I find there are other possible case I ignored before. It seems the possibility to fudge the data is very low due to the new findings.

First, TrendPlot can recording the DMM input too, which has 5000 counts resolution. I know you said you didn't use this mode but this mean the memory has enouth room to store the high resolution data.

Next, in the previous post, I just looked the "Y At 50% = 1.550V" and thought the full range is 1.55X2=3.1V. However, when I looked it again, I found the range does not start at 0V. It starts from 1.350V. The full range is onlt 0.4V (from 1.350 to 1.750). With a 8 bit ADC, you still can get .4/256V, about 1.56mv resolution and 3mv you mentioned is about 2LSB (with 0.125mv error). This explains your graph perfectly and your measurement is correct.


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## wptski (Jan 24, 2007)

tacoal:

Thanks for figuring that out!  I did try the DMM TrendPlot last night and that showed only a 1mv drop at termination. It also show a couple of OFF pulses that were 5mv higher in value some 23 seconds before termination! Like why didn't it terminate then? Oh well, I'll post it as it is interesting or confusing. I see now that I actually have the Y1 cursor on the wrong pulse but both of those two OFF pulses have the same value anyway.


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## tacoal (Jan 24, 2007)

Hi Bill,

It is better to average the voltage in off state of one cycle and compare to that of other cycle. This will filter out the noise and the result will be more reliable.

I don't think the charger designer will use the voltage drop between two adjacent charging cycle as the termination criteria because this change is very small. In most case, They will use the voltage drop from maximum voltage (I think BC-900 does this way) or voltage drop in a specified period, like 5 minute.


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## wptski (Jan 24, 2007)

tacoal:

In my earlier graph which you said is correct with a 3mv drop from the last full cycle OFF to the next on which it terminated. Now your saying that they probably average out values and not compare. Are you backpeddling?

Looking again at this latest graph, I noticed that there is a difference between two full pulses at the end which is 6mv. The earlier graph, all OFF pulses appear to be the same. So which graph is correct now?


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## tacoal (Jan 24, 2007)

wptski said:


> tacoal:
> 
> In my earlier graph which you said is correct with a 3mv drop from the last full cycle OFF to the next on which it terminated. Now your saying that they probably average out values and not compare. Are you backpeddling?
> 
> Looking again at this latest graph, I noticed that there is a difference between two full pulses at the end which is 6mv. The earlier graph, all OFF pulses appear to be the same. So which graph is correct now?


 
Hi Bill,

I am sorry for confusing you.

First of all, your measurement is correct in both case. The point is what is the difference of your measurement and charger's one.

If you move one of cursor a little bit left or right in your graph, you will get different voltage. So you don't know which one is more real than another and you cannot suppose what you measured is the same as what the charger did. In fact, you can get 5mv voltage drop in one off period like the third off period (time about 4 second) in the graph of post #408 from the start to the end of off period. But you cannot use this as the criteria to terminate the charging process.

In real application, the charger might measure many times during the off (on) period and do some kind filtering, like removing maximum and minimum point(s), averaging the remaining and use the result as the measurement of this off(on) period. This will give you more reliable and accurate measurement.


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## wptski (Jan 25, 2007)

tacoal:

I can't view my graph right now as I have pics turned off, so I can load these big pages!!

Okay, we really don't know how the charger works and there's a good chance that MAHA won't tell us how either. If it does average over a series of pulses, it's funny that those two pulses I mentioned didn't cause it to terminate. I think that I seen more than once that the cell's voltage drop .01V on the C9000's screen long before it terminated.

Yes, I moved the cursors around looking for the maximum difference. In Post#408 that was only 1mv.

I'll have to do a few more tests using the DMM ScopeTrend plot and look for variations.


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## Mike abcd (Jan 25, 2007)

Bill,

I'm pretty sure that you're just "zooming" in on the acquired data and not seeing the actual resolution of the Fluke in scope mode. I've done some more looking through the manual and it still looks like the 8 bit resolution of the scope digitizers is across the full input range used. I've never run across a scope that can selectively use the input range over a 1.25V-1.75V interval directly (as an example).

However it looks like you can do that pretty simply by using an external voltage reference. Your fluke has "isolated inputs". That means that the input low ("ground") is floating and not referenced to anything directly. That's also sometimes referred to as "differential input". It will read the difference between the input high and low even when the low input is not at ground. It even has a separate "reference input" which makes using it easier.

If you want to get more resolution on the end of charge termination, you could hook up a voltage reference between the battery negative on the C-9000 and your Fluke. For example, if you connected an alkaline cell with a 1.500 voltage between the battery ground on the Maha and your meter's ground (battery - to Maha battery -, battery + to your meter -), your meter + will read only the voltage above and below 1.5 V.

That would allow you to use a .1 V or .2V full scale input range to track the charge termination. Since the Fluke's input resolution would be over a much smaller voltage range(1.4-1.6V or 1.3-1.7V in this example), it will be able to measure much smaller voltage changes. You can probably improve the resolution on the voltage range of interest by at least 10x by using this technique.

I've done this in the past with scopes with non isolated inputs by "floating" the scope using a 2 to 3 prong adapter and leaving the ground lug unconnected and it definitely works. It's hard to explain so if the above is not clear but you're interested in pursuing it, let me know what makes sense and what doesn't and I'll try to explain it better.

You have to be careful with connections as it's possible to create shorts etc if you don't connect things right. With a low power source like an alkaline AA as a voltage reference, you probably can't damage anything connecting things wrong but it might be possible. Done correctly, there is no chance of harming your Fluke.

I used this technique in the past looking at digital logic on a board that was running on top of a 120 V AC line. In that case, you had to be VERY careful as the scope was at AC line potential and you could shock yourself with 120V AC or short the meter with a full 120V 15A if not careful.

Mike


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## wptski (Jan 25, 2007)

Mike:

I didn't "zoom" in on any portion, I took pains to capture it in one screen. You and "tacoal" can duel it out on wether my scope can or can't do this with 8-bits or not.

The DMM section lowest range is 5V but it does have a relative, zero, delta or whatever you want to call it function. Is this sort-of what your suggesting for the scope input? Connect to the cell and use the relative function prior to entering TrendPlot? On the scope inputs, your making ground 1.5V instead, correct?

EDIT: The scope won't allow the use of the relative function during TrendPlot!


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## tacoal (Jan 25, 2007)

Hi Mike,

You can do the offset stuff, so the scope does.

How do you think what the scope does when you move the Y axis up/down without change the range? Does the resolution be changed? I think it just add a offset to Y axis. You might argue that the ADC is set to bigger range than the window, but this will lower the resolution and I don't think the designer would do this. If I would do the design, I will use 250 out of 256 to cover full Y axis window, leaving extra 6 point to process the over range stuff.

If you still doubt what I said, just look at the Y axis shift part of any scope schematics.


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## NiOOH (Jan 26, 2007)

Another review of the C9000 and yet another missed termination 
http://www.robertphotoblog.com/2007/maha-mhc9000-review/

Another discussion on c9000 and a few more users with termination issues
http://forums.dpreview.com/forums/readflat.asp?forum=1023&message=21512579&changemode=1


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## coppertrail (Jan 26, 2007)

It sounds like Maha is dodging the issue based on their response to the reviewer's report of failed termination.


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## verge (Jan 26, 2007)

I believe I have my first case of missed termination with MH-C9000. The batteries feel warm (not hot) when I touch them.

First, BREAK-IN four JWIN 850mAh AAA.

JWIN 850 NiMH AAA (new)
MH-C9000 / BREAK-IN 
Batt.1	717 MAH	383 MIN	1.44 VOLT
Batt.2	773 MAH	502 MIN	1.45 VOLT
Batt.3	728 MAH	445 MIN	1.42 VOLT
Batt.4	663 MAH	295 MIN	1.40 VOLT

Second, DISCHARGE of the same set of JWIN AAA batteries.

JWIN 850 NiMH AAA (new)
MH-C9000 / DISCHARGE (400 MAH)
Batt.1	759 MAH	172 MIN	1.25 VOLT
Batt.2	787 MAH	234 MIN	1.24 VOLT
Batt.3	761 MAH	217 MIN	1.23 VOLT
Batt.4	763 MAH	140 MIN	1.24 VOLT

Third, CHARGE those batteries.

JWIN 850 NiMH AAA (new)
MH-C9000 / CHARGE ongoing (300 MAH, 1-26-07 04:07AM - 08:07PM)
Batt.1	4374 MAH	296 MA	960 MIN	1.48 VOLT
Batt.2	4408 MAH	297 MA	960 MIN	1.50 VOLT
Batt.3	4411 MAH	292 MA	960 MIN	1.45 VOLT
Batt.4	4371 MAH	292 MA	960 MIN	1.45 VOLT

CHARGE process is still ongoing and I have decided to pull the batteries out of the MH-C9000 at the time of this post. The display show the four batteries in the range of 4516 MAH to 4560 MAH and 1.46 VOLT to 1.48 VOLT.


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## wptski (Jan 26, 2007)

Mike:

Here's a graph with the same scope settings as before but used a alkaline on the ground side as you suggested. Where the Y2 cursor sets, I can move it and get from -4 to 10mv drop but one pulse ahead which is the termination point only -1mv. Anyway, using a battery works. I remembered seeing some kind of voltage reference function in the scope options. Sure enough, there is, you set to a value and there is a 0,+1,+2,+5 and +10 pixels adjustment but I don't understand what it's for. It's only for the scope mode though.


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## SilverFox (Jan 26, 2007)

OK, I finally had a missed termination.

Tenergy 2600 mAh cell charging at 500 mA. Cell temperature stayed at 100 F while the 3 others terminated. I left it for an hour after the others terminated and finally pulled it.

I think 500 mA is too slow a charge rate for these cells, but there are some chargers that use that as their charge rate. Not a good idea for the C9000.

Tom


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## NiOOH (Jan 27, 2007)

SilverFox said:


> OK, I finally had a missed termination.
> 
> Tenergy 2600 mAh cell charging at 500 mA. Cell temperature stayed at 100 F while the 3 others terminated. I left it for an hour after the others terminated and finally pulled it.
> 
> ...


 
Yes indeed, like the BC900. I've used mine for a year charging 2500 Sanyo cells at 500-700 mA. Never had any termination problems.


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## rickd (Jan 27, 2007)

The C9000 is a great battery analyser, but it is not even a good charger! 

I've compared the outside cell temperature of a Powerex 2000 cells recharging at the same rate (1 amp) on the 801D, the BC900 and the C9000. The 801D's temperature peaked at 44 C for a few minutes, while the BC-900 peaked twice at 55; it shutdown once with the cell I had the probe on, twice with the others I had in the charger at the time. The C9000 constantly kept a higher temperature then the 801D and peaked at 55 C. I'm sure I seen a missed termination with a temperature cuttoff based, but I can't comfirm. The funny thing is that I got the C9000 because I did not like the higher temperatures I was seeing with the BC900 and was convinced that the C9000 was going to be based on the same charging technology that went in the 8xx. I even bought the 12V adapter cord so I can use it as my travelling charger






I'm highly disappointed with Maha as it does produce the best charger (IMHO) with their 8xx lines. At least the "discharge" and "breakin" mode work great, and I'll be using those features exclusively.


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## NiOOH (Jan 27, 2007)

Hi rickd.
Although I haven't used the C9000 I agree with you. Shame that Maha couldn't incorporate better termination into, what is otherwize a very well built and functional analyzer. With BC900 you, at least have the option to decrease the charging current to 700 or 500 mA and it will terminate reliably without too much heating. From what I've seen here and elsewhere on the net, this is not an option with the C9000. Decreasing the charging current much below 0.5C causes missed termination. So, you are left with two options:
1. Charege at 0.5-1C and accept quite warm cells.
2. Charge at lower rates and watching the charger to unplug it manually if it misses termination point.
Both are highly unacceptable to me. I hope that the engineers at Maha will make the necessary hardware/software upgrades to C9000.


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## EngrPaul (Jan 27, 2007)

rickd said:


> The C9000 is a great battery analyser, but it is not even a good charger!
> 
> I'm highly disappointed with Maha as it does produce the best charger (IMHO) with their 8xx lines. At least the "discharge" and "breakin" mode work great, and I'll be using those features exclusively.


 
Good observation. I have to agree, I use my 9000 for these purposes, but for general charging I go for the 800 series.


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## tacoal (Jan 27, 2007)

NiOOH said:


> Hi rickd.
> Although I haven't used the C9000 I agree with you. Shame that Maha couldn't incorporate better termination into, what is otherwize a very well built and functional analyzer. With BC900 you, at least have the option to decrease the charging current to 700 or 500 mA and it will terminate reliably without too much heating.


 
This is exactly what I think about the Maha and C9000. Two years after BC-900 introduction and comparing to the rookie La Crosse, Maha made a really shamefull product, the C9000. It's better to call it battery analyzer rather than charger.

Maybe we expected too much from Maha and/or C9000.


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## wptski (Jan 27, 2007)

If a BC-900 can detect -deltaV at .33C and the C9000 can't it means either the 3-5mv used by the C9000 is too small or their process for detecting it at lower charging rates is flawed. We don't know what the BC-900 uses for -deltaV detection voltage but we do know that the BC-900 runs at 51Hz and the C9000 at .5Hz. I don't remember for sure but I think that the C808M ran slow too but it don't charge lower than 1A.


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## NiOOH (Jan 27, 2007)

wptski said:


> If a BC-900 can detect -deltaV at .33C and the C9000 can't it means either the 3-5mv used by the C9000 is too small or their process for detecting it at lower charging rates is flawed. We don't know what the BC-900 uses for -deltaV detection voltage but we do know that the BC-900 runs at 51Hz and the C9000 at .5Hz. I don't remember for sure but I think that the C808M ran slow too but it don't charge lower than 1A.


 
The termination algorithm used by C9000 is apparently flawed. There are dozens of chargers that terminate reliably at less than 0.5C. BC900 aside, look at chargers such as Vanson BC1-HU , Lightning pack 4000N, even Maha 401FS in slow mode, and many others. IMO it is a case of faulty implementation we are dealing in here.

IMO Maha Energy will be better off recalling the already sold units and redesigning the unit.


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## dekelsey61 (Jan 27, 2007)

NiOOH, I totally agree with you on what Maha should do when they update this charger. Hopefully they show great customer service like they have done in the past! I have several not to old batteries that will not terminate in the C9000 at charge rates of 0.5C or better but will terminate just fine in my Maha C801D or my Maha C808M chargers which use a lower charge rate. Something is wrong. Hopefully we all hear something soon on this issue.
Dan




NiOOH said:


> The termination algorithm used by C9000 is apparently flawed. There are dozens of chargers that terminate reliably at less than 0.5C. BC900 aside, look at chargers such as Vanson BC1-HU , Lightning pack 4000N, even Maha 401FS in slow mode, and many others. IMO it is a case of faulty implementation we are dealing in here.
> 
> IMO Maha Energy will be better off recalling the already sold units and redesigning the unit.


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## wptski (Jan 27, 2007)

Has anybody ever heard of a recall on a battery charger? How any other smaller electronic device? :thinking:


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## coppertrail (Jan 27, 2007)

wptski said:


> Has anybody ever heard of a recall on a battery charger? How any other smaller electronic device? :thinking:


A question now is:

Return now, or await a (possible) recall?


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## dekelsey61 (Jan 27, 2007)

We don't know how Maha is going to handle this yet. I hope they will solve the problem and make it good with all of us.
I have a JVC DVD recoreder which is 3 years old(Well past the warranty period). Recently It quit working and a message came up on the screen. I did some looking into this problem and called JVC and told them about the problem. They told me they were aware of this problem and wanted me to send it in for repairs at NO CHARGE to myself. It works just fine now. Almost every unit had this problem. There was never no recall on the units but if you called the maker of the unit and since they knew there was a wide spread problem they fixed it for free. 
Hopefully this will turn out good also. Sorry for the story but I thought it was very close to what is happening with this charger.
Dan




coppertrail said:


> A question now is:
> 
> Return now, or await a (possible) recall?


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## rickd (Jan 27, 2007)

NiOOH said:


> The termination algorithm used by C9000 is apparently flawed. There are dozens of chargers that terminate reliably at less than 0.5C.


 
Fixing the termination problem would be nice, but I would still be disappointed unless they also change the charging electronics. I'm a strong believer that cell temperature as an adverse effect on the longevity of the cell, not charge current. At 2 amps, my C801D produced a lot less temperature on my cells most charger do at 1 amp. I wouldn't bother having my unit replace if they only fixed the termination issue, as I would still be useless to me has a charger. I'd still keep it, has I enjoy using the analyser portion of this charger more then that of the bc-900.

Maha's engineers obviously know how to build good chargers, why did they short changed us with this one?


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## SilverFox (Jan 27, 2007)

Hello Rickd,

Welcome to CPF.

If you look at the temperature graphs you will notice that they are very reasonable throughout the charge. The rise in temperature occurs as a spike at the end. If the cell terminates earlier, there will be less peak temperature.

Tom


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## knightc2 (Jan 27, 2007)

I came across this thread while searching for reviews on the C9000 and I too am worried about the termination issues. Everything else looks great aside from that. I hope that MAHA does something about this. Until then I'll stick with the C800S and keep checking for updates.


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## dekelsey61 (Jan 27, 2007)

Can anyone explain why most of the termination failures are when using AAA batteries? At least that is what it seems like to me. I have had many problems with AAA batteries. I am using a charge rate above the 0.5C rate.
Dan


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## wptski (Jan 27, 2007)

SilverFox posted a link that showed that AAA had a higher internal resistance than AA cells. Maybe that's the reason but just a guess on my part!


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## wptski (Jan 27, 2007)

I have a 700mAh LaCrosse AAA externally connected to the C9000 charging at 200ma. It's at 1100mAh input which looks like it missed termination. I have a current clamp probe connected for periodic checks. It's currently still charging.

I will update this post.

1240mAh, 1.48V, 75F and still charging!
1586mAh, 1.49V, 75F and still charging!
1752mAh, 1.49V, 75F and I pulled the plug!!

Being externally connected means that it going to run cooler anyway.


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## tacoal (Jan 27, 2007)

wptski said:


> Has anybody ever heard of a recall on a battery charger? How any other smaller electronic device? :thinking:


 
panasonic bq-830 has been recalled.

It seems the BQ-830 use the temperature as the criteria of termination. But this fails often when room temperature is high and overchanges the battery. First, panasonic tried to fix this by updating firmware and it seemed not working. So panasonic recalled it and refunded the charge. Since then, Panasonic does not have any new charger coming out. It only change the max timer of BQ-390 to accommodate new high capacity battery.


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## SilverFox (Jan 27, 2007)

Here is another missed termination... This time on the BC-900.

I took the same cells that I used to test at 500 mA charging current in the C9000, drained them and am charging them on the BC-900. These are the same cells referred to in post 420.

3 of the 4 cells terminated an hour ago, and the same cell that would not terminate on the C9000 is not terminating on the BC-900. The cell is hotter on the BC-900. It is up to 108 F. Voltage is 1.48 volts.

The other cells terminated after putting roughly 2000 mAh into the cells. The 4th cell is still charging after 2600 mAh have been put into it. 

It should time out at 3000 mAh, so I will let it go until then.

Once again I will repeat that 500 mA is too slow a charge rate to pick up an end of charge termination signal with these high capacity cells.

I will have to say that 3 of the 4 cells did terminate on the BC-900, but they also terminated on the C9000.

What does this all mean? 

Have you ever wondered why Duracell and Sanyo use a 1 C charging rate for their performance graphs?

It means that the end of charge signal is not reliable at low charge rates. You can't fabricate something out of nothing. I don't care what charger you are using, at low charge rates there is not a reliable end of charge signal. Your chargers that are terminating on time or maximum capacity or peak voltage, but not on negative delta voltage. Also, temperature change is not taking place, so you won't get a change in temperature slope that allows you to terminate on that.

I also need to point out that the minimum charge current is dependent on the state of health of the cell. Cells that are in great health seem to have enough of a signal to terminate even at lower charge rates. However once a cell develops some higher impedance, all bets are off.

Tom


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## dekelsey61 (Jan 27, 2007)

Hi Tom, How do you explain some of my batteries that are fairly new terminating just fine in the soft mode(350Ma for AAA batteries)on my C801D charger but if I set the charge rate on the C9000 charger at 500Ma for those same batteries(AAA 850Mah) they keep going on and on and never terminate? Thank you.
Dan


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## SilverFox (Jan 27, 2007)

Hello Dan,

I don't have all the answers, but let's look at what you are saying.

You have a cell, or perhaps several cells, that you discharge to 1.0 volts, then charge them on the 801 at 350 mA and they properly terminate. You determine that they properly terminate by timing the charge and all the cells terminate at the same time, in roughly 2.5 hours.

You then take those same cells, once again discharge them to 1.0 volts and this time charge them on the C9000 at 500 mA. This time, they do not terminate.

Is this what you did?

Tom


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## TorchBoy (Jan 28, 2007)

SilverFox said:


> Have you ever wondered why Duracell and Sanyo use a 1 C charging rate for their performance graphs?
> 
> It means that the end of charge signal is not reliable at low charge rates. You can't fabricate something out of nothing. I don't care what charger you are using, at low charge rates there is not a reliable end of charge signal. Your chargers that are terminating on time or maximum capacity or peak voltage, but not on negative delta voltage. Also, temperature change is not taking place, so you won't get a change in temperature slope that allows you to terminate on that.
> 
> ...


Tom, are you saying all older cells should be charged at 1C?

FWIW I've just done a 400mA charge & discharge cycle on my old set of AAA cells (break in tested capacity 651-687mAh for nominal 800mAh). Two cells stopped at 725mAh and 763mAh charging input, while the other two continued until 1202mAh input, 200 minutes, where I decided not to let them suffer any more and pulled them out. They were too hot to touch for more than a second or so. The voltage at that time was 1.49V on each and had been slowly increasing, so I'm not sure they missed terminating, but surely that can't be good?

Above results aside, would these be better off being charged at 800mA?

Edit: Forgive me if it's been asked before, but how much of the worrying about missed termination with the C9000 is because we can now see how much juice has been put into the cells?


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## JackJ (Jan 28, 2007)

Another example of "It's not just the C9000". After discharging some brand new Eneloop AAAs in the C9000 I put them to charge in my 808M at the "soft" rate. When I checked, 3 of four cells were done, and quite cool to the touch, but one was still going. I let it go an additional 40 minutes before pulling it. It was warm, not hot, in my 50F degree garage, and measured 1.53 volts. I didn't want to wait any longer, but am fairly confident it would have kept charging away. 

This is the first missed termination I've encountered on any other charger besides the C9000, and even the latter has just missed once, also on an AAA, though an Energizer 850 mAh. I've been trying to get that same cell to miss again, but haven't been able to after 4 R/A cyces w/ a 500 mAh charge rate.

Jack


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## dekelsey61 (Jan 28, 2007)

Hi Tom, Thanks for your reply. Yes it was. I didscharged the batteries and then put them in the 801 to charge in the soft mode which charges AAA at 350Ma. Almost 2 1/2 to 3 hours later the DONE came on. That is how I know they terminated. Then discharged them down again and put them in the C9000 at a charge rate of 500Ma and more than 5 hours later they were still at 1.48 volts and not terminating. I just pulled them out. The cells were not HOT. They were warm to the touch. It does seem the missed terminations is greater with AAA batteries. Thanks again.
Dan




SilverFox said:


> Hello Dan,
> 
> I don't have all the answers, but let's look at what you are saying.
> 
> ...


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## SilverFox (Jan 28, 2007)

Hello Ian,

No.

What I am saying is that the end of charge signal is not reliable at lower charge rates. When you charge at a lower charge rate, you need to keep an eye on things. You also need to expect missed terminations.

This is not an excuse for the C9000 missing so many terminations, and continuing to charge full cells for extended periods of time.

It has been estimated that the leading cause of cell failure is leaving them for extended periods of time on a charger trickle charging at too high a rate. This is closely followed by excessive heat. 

Unfortunately, the C9000 has demonstrated problems with both of these issues.

The strong point with the C9000 is that it gives us information so we can see what is going on. The BC-900 also gives us this information, but I am not sure anyone has taken a critical look at it. 

The C9000 was designed so you could do a Break In charge on high capacity C and D cells, using an adapter to hold the cell. This requires that the safety timer be set at a higher value. I speculate that if Maha had used (for AA cells) 3000 mAh like the BC-900, or 2500 mAh like the original BC-1HU, or 3500 like the current BC-1HU sometimes called the BC-2HU, we probably would not be having these discussions. There would be some comments about a hot battery every once in a while and perhaps someone would notice that one of their cells put 3000 mAh in while the other cells only took 2000 mAh, but that would be about it.

I charge cells on the BC-900 all the time. I can not remember ever using the 500 mA charging rate until these tests. I always charge at 1000 mA for 4 AA cells and 1500 mA for 2 AA cells. I also don't recall having a missed termination with cells up to 2500 mAh. I rarely use the soft charge option on the Maha 808, and have not had any problems with missed terminations on it.

I have a Schulze charger. It has one of the most advanced NiMh charging algorithms around, and is capable of getting a very full charge on a cell without the cell heating up. The algorithm is based on healthy cells and factors in lead wire and connection resistance along with cell impedance. When I charge a 4500 mAh cell and notice that the auto charging rate is only 500 mA, I know something is wrong. When I move the charging rate up to 2 amps or higher, the cell get hot. I am now in a difficult place. Charging at 500 mA will not give me a reliable end of charge signal, however charging at 2 amps or higher will overheat the cell. At this point my inclination is to recycle the cell. If I really need to use it, I will set a timer and charge at 500 mA for 16 hours.

As "smart" as the Schulze charger is, it does not reliably terminate at low charge rates. However, it does utilize a back up timer to minimize the overcharging risks.

OK, back to your question...  

With old cells, I would recommend running a Break In on them, then charging at a minimum of 0.5 C. If they get hot, that means the impedance of the cell has increased and they are getting near the end of their life. Sometimes you can revive them by running 10 cycles on them, and then keeping them in constant use. Other times they just die.

Always remember to keep an eye on things, and if something doesn't seem right, stop the charge.

If money is tight, or if you want to play, you can try keeping them to see if you can come up with the right combination to get the chemistry working again. If performance is critical, replace the cell.

Tom


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## SilverFox (Jan 28, 2007)

On a side note...

I received a call from my Mother in law yesterday. She has a 4 hour Energizer charger and was charging Energizer 2500 mAh cells on it. When she checked on it, all of the shrink wrap had split on the cells, the cells had vented, and the plastic of the charger was melted in places.

Her question was, What Happened?

I laughed and told her about the discussion we were having on this thread.

Tom


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## wptski (Jan 28, 2007)

If you look at Post#60 where I tried to force a termination miss by charging some 1.8Ah cells at 600ma. Only one cell terminated on time, two went way over and the last never finished. I pull it at 20hrs. for 6C!

Strange thing is that the one cell never got over 127F. If you miss termination at higher rates the cell(s) will be warmer but at .33C it's not excessive.


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## verge (Jan 28, 2007)

I now know if my MH-C9000 missed a CHARGE termination. My curious question is how will I know if MH-C9000 missed a DISCHARGE termination? What is the recommended cut-off mAh, volt and time?


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## SilverFox (Jan 28, 2007)

Hello Verge,

If the voltage drops to 0.9 volts, it has missed a discharge termination. It is supposed to stop at 1.0 volts.

Tom


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## verge (Jan 28, 2007)

SilverFox said:


> Hello Verge,
> 
> If the voltage drops to 0.9 volts, it has missed a discharge termination. It is supposed to stop at 1.0 volts.
> 
> Tom



SilverFox, thanks much for the info.


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## dekelsey61 (Jan 28, 2007)

Something interesting. I have had 3 energizer 850Mah AAA Batteries that would not terminate in the C9000 charger with a charge rate of 500Ma(That is above the recommended rate of 0.5C recommended by William)
Then I drained then down again and set the charge rate at 800Ma(Just below the 1C rate). To my surprise all 3 batteries terminated with-in several minutes of each other. The batteries did not heat up that bad this time. Any ideas what is going on? I do know charging at a higher rate(near the 1C level) cause more heat. Thank you.
Dan


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## NiOOH (Jan 28, 2007)

"Have you ever wondered why Duracell and Sanyo use a 1 C charging rate for their performance graphs?"

To me, the main reason is that with a new (properly formed and broken-in) cell charging at 1C to -dV of 10 mV can yeld 3-4% more discharge capacity and higher voltage during discharge compared to other charging methods. Thus, their discharge graphs would look more presentable.


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## SilverFox (Jan 28, 2007)

Hello NiOOH,

I am not sure that is correct. I think you get the most capacity utilizing the "standard" charge of 0.1 C for 16 hours.

Tom


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## Mike abcd (Jan 28, 2007)

According to the manufacturers, a 1C charge rate terminated at 10 mV -dV is a slight over charge. A .1C rate for 16 hours is a much larger over charge.

Over charging increases measured capacity but decreases the number of useful cycles. 

Most of the data on cycle life seems to be at 1C -10 mV dV termination. Most of the data on capacity seems to be at .1C for 16 hours.

A sterling example of marketing over engineering...

Mike


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## Mike abcd (Jan 28, 2007)

SilverFox said:


> ...
> 
> What does this all mean?
> 
> ...



Tom,

I certainly agree that -dV termination is not reliable at low C rates. At lower C rates, the size of the voltage drop decreases and depending on the cell and rate may not happen at all.

However, that doesn't mean that -dV can't be detected at .2 C and even lower on some cells. I've already posted a graph in this thread of the BC-900 terminating charge on -dV at 500 mA on an Energizer 2500. Take another look. It clearly wasn't terminated on "time or maximum capacity or peak voltage" as you claim. BTW, didn't we debunk the "NiMH peak voltage termination" fallacy already and you agreed you were wrong on that one?

As a recent example that you're aware of, a member has a new BC-900 reporting high mAH delivered in one slot relative to the others. He ran 4 charge cycles at 200 mA on 4 Eneloops on his BC-900. Total of 16 charges at 200 mA on 2000 mAH cells. All at .1C. All apparently terminated. They certainly didn't terminate on ""time or maximum capacity or peak voltage". What other explanation than -dV???

Again, I completely agree that -dV termination is not reliable at lower rates. However that doesn't mean that -dV doesn't happen at .2C and lower on many batteries and that some chargers can detect it.

Have you found a battery yet that terminates on the C-9000 that doesn't on the BC-900? Now that would be interesting. We certainly have lots of cases where neither terminates or the BC-900 does but not the C-9000.

Mike


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## SilverFox (Jan 28, 2007)

Hello Mike,

You are correct. Sometimes you can detect - delta V at a low charge rate, but it is not reliable. If you want a more reliable termination, charge at a minimum of 0.5 C. If you want a very reliable termination, charge at 1 C.

Our discussion about peak voltage was in reference to a particular chip that I had referenced. On that chip, peak voltage detection was set to 2 volts. Using a 2 volt maximum voltage criteria is not useful for determining the end of charge signal.

Peak voltage detection is used as a termination method and is available on other controller chips. It has problems with new cells because they often have a plateau in the charge voltage causing premature charge termination. Once the cell get broken in, it works quite well.

You may want to take a look at post 439. I took 4 cells and they terminated properly on both the BC-900 and the C9000 when charging at 1000 mA. Discharged the cells and one of them failed to terminate on the C9000 at a 500 mA charging rate. Once again I discharged the cells and placed them on the BC-900 at 500 mA. The same cell failed to terminate on the BC-900.

Tom


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## Handlobraesing (Jan 28, 2007)

SilverFox said:


> Hello NiOOH,
> 
> I am not sure that is correct. I think you get the most capacity utilizing the "standard" charge of 0.1 C for 16 hours.
> 
> Tom



Would you say the difference in final capacity is negligible between 0.1 and 0.2C charge current with the charging time adjusted inversely proportional?


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## SilverFox (Jan 28, 2007)

Hello Handlobraesing,

I have never tested that, but I wouldn't think there would be too much of a difference.

Tom


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## Mike abcd (Jan 28, 2007)

SilverFox said:


> Hello Mike,
> 
> You are correct. Sometimes you can detect - delta V at a low charge rate, but it is not reliable. If you want a more reliable termination, charge at a minimum of 0.5 C. If you want a very reliable termination, charge at 1 C.
> 
> ...



Tom,

I'm used to seeing "peak voltage" referred to as "0 dV". I think it can be very effective with few false terminations as long as it isn't used below a voltage threshold like 1.40 V. I agree about new cells as they will often terminate falsely even with -dV in the first couple/few charges depending on the quality of the cell, etc.

I'm aware of a number of cases of the same cell failing termination on both the BC-900 and C-9000. I'm aware of a number of cases of the same cell failing to terminate on the C-9000 and terminatting normally on the BC-900.

I'm not aware of ANY cases of the same cell failing to terminate on the BC-900 and terminatting normally on the C-9000. Have you seen that happen?

I've only logged voltage on a few BC-900 charges but comparing them to a lot of C-9000 charges, the BC-900 seems to terminate on a smaller -dV. Maha specs it at 5 mV -dV but measures voltage while the cell is not under the charge current. From the graphs it looks like that reduces the effective sensitivity by 2.5x-3x compared to the voltage drop on the charge pulse.

I'm not sure what the BC-900 is using but it appears to either be a smaller -dV or it's measuring voltage on the charge pulse.

Mike

Edit Maha -dV spec typo corrected. Was 50 fixed to 5 mV


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## SilverFox (Jan 28, 2007)

Hello Mike,

Unfortunately I can not help you. I charge at high charge rates attempting to maintain at least 0.5 C (but prefer 1.0 C) when expecting a charger to terminate the charge. I monitor the impedance of my cells, and when it rises to the point where they heat up higher than normal during charging, I recycle them and move on. 

The result of this practice is that I don't experience missed terminations.

Tom


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## Mike abcd (Jan 29, 2007)

SilverFox said:


> Hello Mike,
> 
> Unfortunately I can not help you. I charge at high charge rates attempting to maintain at least 0.5 C (but prefer 1.0 C) when expecting a charger to terminate the charge. I monitor the impedance of my cells, and when it rises to the point where they heat up higher than normal during charging, I recycle them and move on.
> 
> ...



How do you monitor impedance? What cell temps do you see at EOC @ 1C? I'm still looking for a charger than keeps cell temps reasonable.

Mike


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## Mike abcd (Jan 29, 2007)

wptski said:


> Mike:
> 
> Here's a graph with the same scope settings as before but used a alkaline on the ground side as you suggested. Where the Y2 cursor sets, I can move it and get from -4 to 10mv drop but one pulse ahead which is the termination point only -1mv. Anyway, using a battery works. I remembered seeing some kind of voltage reference function in the scope options. Sure enough, there is, you set to a value and there is a 0,+1,+2,+5 and +10 pixels adjustment but I don't understand what it's for. It's only for the scope mode though.



Bill,

Sorry for the long delay in replying. I wanted to go through your Fluke's manual in detail but that hasn't happened yet so here's some comments based on my earlier look and your pics.

You and tacoal look like you were right and you can "offset" the input range of the scope's A/D converters. In this plot. it looks like an input range of 400 mV. That should give you about 1.6 mV resolution for 1 bit. You can probably go to the next lower input voltage range and get better resolution (20 mV/div???) but you might not be able to see both the "on and off" portions of the charge pulse together and only be able to track "one at a time".

Well done on using the external reference! I didn't explain it well. You apparently didn't need it but it's a neat trick to know and can get you more range than your meter probably allows without it. Fluke put some nice features in! The internal voltage offsets are neat.

As I mentioned earlier, -dV is a fairly slow event from what I've seen and takes at least 10s of seconds to a few minutes depending on the "C" rate. I think you have to monitor over a longer time period to see the -dV that it's using for termination.

On this plot and a few others, you're comparing levels (cursor readouts) on the last charge pulse and the level of the pulse after the higher active charging level. At that point, the charge has stopped and you're comparing to the much shorter top off pulse resting period. The charger made the decision to stop before that happened and you're looking at a voltage that is decaying due to the drop in charging current and not the -dV.

To look at -dV, you have to sample over a longer total time period. I don't know if the memory can hold more data than you're showing and allow you to scroll through it. If not, you'll have to slow down the sampling rate even if it means the pulses run together and get ragged like in my graphs.

When a charge pulse stops/starts, it takes time for the voltage to drop or decay and you're seeing some of that in the "rounded" leading edges. I suspect Maha uses the portion near the end of the resting period when the voltage is more stable for measuring -dV. That's just a guess without knowing the type/performance of the A/D converter. It might be averaging over a longer portion of the pulse depending on the type of converter (integrating vs successive approximation).

I'm very curious what the pulses look like sampled faster. I'm interested in how "clean" they are. Have you looked at individual pulses sampled at a higher rate?

Your Fluke is a nice toy! Wish I had one. I've played with a few in the shop but haven't been able to justify the cost given other expensive interests.

Mike


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## TorchBoy (Jan 29, 2007)

Ongoing testing with these middle-aged 800mAh AAA cells to find a suitable charging current - I've added 600mA to the "not healthy" list, with 3 of 4 failing to stop. One cell got 1450mAh before I pulled it out (then dropped it, ow). I know that's not as bad as most overchargings mentioned, but I really like things to just work and it's not managing that. (800mA seems to stop every time, but early.) With my new Eneloops it's done alright but two channels have been much higher (~33%) than the other two. Combined with the high impedance assessments it's given many of the old cells I've reached the conclusion I shouldn't have given my previous charger away. It worked fine with them all. I expected so much better from a Maha charger. :thumbsdow 

Sigh. I've started looking for an EDC (everyday charger) and keep the C9000 for analysis. If only I had some money left. :laughing:


----------



## wptski (Jan 29, 2007)

Mike abcd said:


> Bill,
> 
> Sorry for the long delay in replying. I wanted to go through your Fluke's manual in detail but that hasn't happened yet so here's some comments based on my earlier look and your pics.
> 
> ...


Mike:

The scope has enough memory to capture hours but it compresses so much if you zoom in towards the end, those pulses won't look the same. Can't check right now but I believe it was 12s per screen. I can try grabbing several screens and see how good it looks.

I used a used a old alkaline that happened to be laying around. A fresh cell might narrow the range more.

I posted a screen showing a single pulse in the C9000 FAQ thread. Take a look, it isn't clean at all and that was my question as I posted a pulse from a C808M too!


----------



## wptski (Jan 29, 2007)

Mike abcd said:


> How do you monitor impedance? What cell temps do you see at EOC @ 1C? I'm still looking for a charger than keeps cell temps reasonable.
> 
> Mike


Mike:

What's needed is a multi-cell charger that has the power supply and electronic circuits housed seperately from the cell holder.


----------



## wptski (Jan 29, 2007)

SilverFox said:


> Hello Mike,
> 
> Unfortunately I can not help you. I charge at high charge rates attempting to maintain at least 0.5 C (but prefer 1.0 C) when expecting a charger to terminate the charge. I monitor the impedance of my cells, and when it rises to the point where they heat up higher than normal during charging, I recycle them and move on.
> 
> ...


Tom:

If high internal resistance causes higher temperature then a AAA cell should get warmer at the same charging rate/C than a AA cell using the link you posted in some other thread. It showed AAA cells had twice the internal resistance of a AA cell.

Seems like we are seeing more missed terminations with AAA than AA cells.


----------



## wptski (Jan 29, 2007)

Mike:

Tom posted a link to a site that listed the impedance for "some" Ni-MH cells but not anything over 2Ah. It listed a procedure as impedance equals the volltage drop for 500ms divided by the 500ma or the charging rate. This can easily be done with a scope and a good non-PWM discharger. The Durtrax ICE holds current levels fairly stable without ramping up, so it's a good source. The ICE returns a impedance value on discharge but takes almost 2 min to do that!

Something else to fiddle with! 

EDIT: I misread their procedure! It's not discharging at 500ma but charging at 500ma. The only thing that I question is that Ohm's Law is R=V/I where I=Ampa not ma! I'll have to try this.


----------



## SilverFox (Jan 29, 2007)

Hello Mike,

There are several ways to measure impedance. The method that Bill referred to works, or you can use a battery impedance meter for a quick AC check.

As far as chargers go, it is difficult to find a charger that is capable of charging at 1 C. The highest capacity cells that I have are 2600 mAh. My Schulze charges them at 5 amps and at the end of the charge they are at 125 F. On the C9000 at 2 amps they get slightly hotter.

Tom


----------



## wptski (Jan 29, 2007)

Tom:

Duratrax ICE will do at least 2.3A on a 2.3Ah Duracell with the highest temperature of 106.8F. Did you get your impedance meter yet?


----------



## SilverFox (Jan 29, 2007)

Hello Bill,

 Yes  

Now I have to figure out what it means and how useful it is.

Tom


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## Papuga (Jan 29, 2007)

I received my C9000 last Monday, and since then I have thrown every battery conceivable at it trying to get it to overcharge. To date, it has not missed a single termination on both AA and AAA batteries, Have not tried any of my eneloops yet, but I may give that a shot tonight. 

Now, truth be told, I have been using the .7C or .8C range for each battery I have tried, and it has yet to miss a termination. Each battery terminates within 5% of each other, and no battery is too hot to handle. My IR thermometer shows that the maximum temperature reached so far is 102.6 degrees. I have seen my Ansmann Energy16 shoot way higher than that temperature, and miss quite a few terminations, especially on "marginal" batteries. None of the batteries that I have thrown at it have been truly pampered, as they are all from my daughters toys, so deep-discharge is a very common result. 

My real question is has Maha made any firmware changes since the first shipment, and is there any way to tell? Don't get me wrong, I am happy that it is terminating correctly, but after following this thread for some time now, I am still nervous to leave the batteries by themselves or use it on any of my high capacity or eneloop cells.


----------



## SilverFox (Jan 29, 2007)

Hello Papuga,

Welcome to CPF.

I am not aware that Maha has anything but the original C9000. I know they are reviewing the data we have presented, I just don't know what they are going to do about it, and how, if anything is done, it will be handled.

For now, keep charging at higher rates and enjoy proper termination... If your cells are in good condition, you will also not experience high temperatures.

Tom


----------



## webfors (Jan 29, 2007)

Just received my c9000 today, and what a toy!! :rock:

I've read hours and hours of threads on the c9000 and have concluded that there's no reason to charge at less then .7C, so that's how it's going to be from now on. No sense in *trying* to get a missed termination, since we all know it's possible, and is an inherent risk of charging batteries. With the c9000 that risk is compounded since there's no timer cutoff until 20k mah pumped into the battery and there isn't enough heat generated below .5C to trigger the temp cutoff. 

What I would like to know is, how many missed terminations are there with *healthy* batteries, at or above .7C? Not many I bet. After my bc900 meltdown:

http://webfors.com/pictures/bc900_meltdown/

I take precautions with any charger, like plugging the c9000 into a simple timer which you can program to your hearts desire. 

I thought of getting another bc900 with the new v33 firmware, but the thought just gave me nightmares! I mean, temp cuttoff is supposed to work, and from what I've read the current most likely jumped from the 500ma that I programmed to 1800ma which caused the meltdown. It's one thing for termination to be missed, but for the temp cuttoff to malfunction *and* for the current to be more then tripled is engineering at it's worst.


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## Mike abcd (Jan 29, 2007)

SilverFox said:


> ... If your cells are in good condition, you will also not experience high temperatures.
> 
> Tom



How I wish that was really true 

I get 135+ deg F consistently on slots 2/3 charging 4 AA cells @ 2000 mA. That's on Duracell 2300, Energizer 2500 and Maha Powerex 2700. All of them test within 5% or better of their original tested capacity after break in.

Can I get some of what you're smoking Tom?

Mike


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## TorchBoy (Jan 29, 2007)

Can someone remind me what temperature the C9000 is supposed to terminate at? Cells too hot to hold (which I've been getting) I think means >50°C (122°F), so I presume it's somewhat greater than that.


----------



## webfors (Jan 29, 2007)

Mike abcd said:


> How I wish that was really true
> 
> I get 135+ deg F consistently on slots 2/3 charging 4 AA cells @ 2000 mA. That's on Duracell 2300, Energizer 2500 and Maha Powerex 2700. All of them test within 5% or better of their original tested capacity after break in.
> 
> ...




Yikes! 135 degrees? I just got mine today so I can't confirm. If that's true I'll be doing all charging in my 808M, which is the coolest charger I've ever used.

I don't think my energizer 15 minute charger even gets that hot.. Mike, I hope your unit is defective


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## wptski (Jan 29, 2007)

The C9000 is supposed to cutoff at 131F but the location and operation of the sensors are in doubt! If you look way back in this thread I have posted some temperature graphs and IR images which you may find interesting.


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## Mike abcd (Jan 29, 2007)

webfors said:


> Yikes! 135 degrees? I just got mine today so I can't confirm. If that's true I'll be doing all charging in my 808M, which is the coolest charger I've ever used.
> 
> I don't think my energizer 15 minute charger even gets that hot.. Mike, I hope your unit is defective



Unfortunately, I'm not the only one who gets temps that hot. The highest i've seen is 147 deg F.

A couple of examples from Bill (wptski) with graphs and IR images.

https://www.candlepowerforums.com/posts/1768763&postcount=166
https://www.candlepowerforums.com/posts/1781755&postcount=299

The worst case is slots 2/3 charging 4 cells at 2000 mA but I've seen temps over 130 F @ 1000 mA with 4 cells. The only way I've found to keep them under 130 F consistently is charging only 2 cells in slots 1/4 @ 1000 mA.

The charger circuitry gets very hot when charging multiple cells at higher rates and is a major cause of the high cell temps. Bill charged some cells connected externally and got temps below 110 F from what I remember.

Mine is going back as soon as I get a chance to pack it up and ship it.

Mike


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## Mike abcd (Jan 29, 2007)

wptski said:


> Mike:
> 
> The scope has enough memory to capture hours but it compresses so much if you zoom in towards the end, those pulses won't look the same. Can't check right now but I believe it was 12s per screen. I can try grabbing several screens and see how good it looks.
> 
> ...



Bill,

I think I found the post. You were monitoring current in the one I found and it looked really ugly with an oscillating level on top of it.

I'm surprised it doesn't seem to show up (as much?) in your voltage plots.

Mike


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## Mike abcd (Jan 29, 2007)

wptski said:


> Mike:
> 
> What's needed is a multi-cell charger that has the power supply and electronic circuits housed seperately from the cell holder.



That would be really nice but I suspect using an internal fan to cool the electronics would be a huge benefit too. 

My Lenmar Mach 1 uses an internal fan just to cool its' internals and both the charger and batteries stay very cool. A lot of that is it undercharges in fast charge mode but batteries in the C-9000 get a lot hotter from the charger's waste heat than in the Lenmar...and that's before they really start to cook due to their self heating as they approach fully charged.

Mike


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## webfors (Jan 29, 2007)

Mike abcd said:


> The charger circuitry gets very hot when charging multiple cells at higher rates and is a major cause of the high cell temps. Bill charged some cells connected externally and got temps below 110 F from what I remember.



Sounds like an internal fan might be in order to vent that heat out the top. Just finished charging my first set of 2000mah eneloops at the default charge rate of 1000mah, all terminated fine, temps were slightly lower then temps on my 204w, definitely higher then my 808m, however I confess that I have no official way to determine the official temps.

I don't think it'll go back. It simply has too many other useful features, and with the 3 year warranty I'm pretty sure maha will back it up as they have with my other chargers in the past, assuming any changes are made to the charger. Besides, I live in Canada, and I don't want to pay for shipping back to TD


----------



## wptski (Jan 29, 2007)

Mike abcd said:


> Bill,
> 
> I think I found the post. You were monitoring current in the one I found and it looked really ugly with an oscillating level on top of it.
> 
> ...


Mike:

Yep, you've found it!


----------



## wptski (Jan 29, 2007)

Guys:

What about the users that tried a fan and had termination problems? What's that all about??


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## TorchBoy (Jan 29, 2007)

webfors said:


> I don't think it'll go back. It simply has too many other useful features, and with the 3 year warranty I'm pretty sure maha will back it up as they have with my other chargers in the past, assuming any changes are made to the charger. Besides, I live in Canada, and I don't want to pay for shipping back to TD


My one isn't going back either, even with this happening more than once. I do really like it, or at least I like it how it should work. And New Zealand is even further from TD.


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## wptski (Jan 29, 2007)

Mike:

Another graph over 3 min., 500mv, 200microseconds, scope TrendPlot. You can see how the charging voltage starts to drop, cursors show a 20mv drop. Can't show both but the low pulse end to end was about a 10mv drop but still looks level from the graph though, not like the high points!


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## Mike abcd (Jan 30, 2007)

Bill,

The -dV looks a lot smaller on the resting pulse than on the active charge pulse. It's hard to tell just from looking at the graph but it looks very similar to what I measured.

That's a good illustration of -dV taking a while as I mentioned earlier.

Mike


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## Mike abcd (Jan 30, 2007)

wptski said:


> Guys:
> 
> What about the users that tried a fan and had termination problems? What's that all about??



I wish I knew...a wild guess is that the fan limited the temp rise near the end of charge which causes the voltage drop and the Maha missed it because of the smaller magnitude.

I never got around to monitoring voltage while using a fan.

Mike


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## jusko (Jan 30, 2007)

If you use a fan right over the charging batteries, its very likely that there is missed termination. If you think that there is a missed termination, try move away the fan when the batteries should have been fully charged, "DONE" will show up in a few seconds.


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## wptski (Jan 30, 2007)

This site: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1666 is actually the one posted by Tom in another thread. If you go to aplication notes and battery managment, there's all kind of stuff.

This link shows a Maxim 712 chip which is a Ni-MH charger that uses zero/peak voltage for temination and "they" don't recommend using -deltaV. a Maxim 713 is a Ni-CD chip that uses -deltaV. There is also a MAX712EVKIT which the whole circuit, less the chip. You can use either.

If I wasn't electronicly challenged, I might try one, although buying a single chip/board might be a problem!

A bit OT but lots of info there but is it dated?


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## SilverFox (Jan 30, 2007)

Hello Mike,



Mike abcd said:


> How I wish that was really true
> 
> I get 135+ deg F consistently on slots 2/3 charging 4 AA cells @ 2000 mA. That's on Duracell 2300, Energizer 2500 and Maha Powerex 2700. All of them test within 5% or better of their original tested capacity after break in.
> 
> ...


[/quote]

There is no doubt that cells with higher impedance will heat up hotter during high current charging. They are also more likely to not signal a strong end of charge termination signal. 

I decided to take another look at the 2 amp charging rate on the C9000.

You will remember that, at that rate, I had 4 Powerex 2500 mAh cells get up to 159 F. After that, I took my charger apart and put some thermal paste in the area where the temperature sensor contacts the metal contact strip. Using a heat gun, I determined that my high temperature shut off was still functional. It seems to be set at roughly 135 F on my set up.

I selected 4 different cells for the test and placed a piece of "88" tape in the center of each cell for a similar IR target response. The batches of cells were discharged at 1 amp, rested for 30 minutes, then charged at 2 amps. Room temperature is 68 F.

The cells all spent most of their charge time at 100 - 110 F, then the temperature spiked at the end of the charge. The maximum temperature from the Sanyo 2500 mAh cells registered 122 F in the middle slots, the Powerex 2500 mAh cells came in at 131 F, the Titanium 2600 mAh cells came in at 132 F, and the Titanium 2400 mAh cells came in at 129 F.

I did notice that the top end of the charger was showing a peak of 135 - 140 F, and the area under the cells seemed to be running around 10 - 15 F lower than that. This charger does seem to warm up when charging 4 cells at the maximum 2 amp rate, but the cell temperatures seem reasonable, if your cells are in good condition. 

If your cells are developing higher internal resistance, they will heat up when charged at this rate. You have also indicated that your cells get hot when charged in the outer slots at 2 amps. What happens when you charge them at 2 amps on other chargers? I have notice that my cells end up at around 105 - 120 F when charging at 2 amps on my C808M. It would appear that the C9000 circuitry is adding an additional 10 - 20 F.

I am not sure why we are seeing such differences in cell temperatures, but have to believe that the cell condition has a lot to do with it.

Tom


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## SilverFox (Jan 31, 2007)

Exploring this a little further...

With the purchase of my C9000, I also picked up some Powerex 2000 mAh cells. I decided to see what temperatures would be involved with charging these cells at 2 amps.

I first did a Break In cycle on the cells (they are coming in at around 1840 mAh), then discharged them and let them rest. 

Charging at 2 amps, I am seeing maximum temperatures of 119 F.

Perhaps we need to "bin" our cells based on cell temperature during charging. As Mike has pointed out, his cells are still at 95% of capacity, but it seems that they may be developing higher internal resistance. I think the only way to check for this is to plot a discharge curve and see if there is a higher drop in Watt Hours.

So far we have seen a wide range of temperatures. I am seeing 120 - 130 F, but have had one case of 159 F with cells that are known to have issues with high self discharge and high internal resistance. Bill is seeing 130 - 145 F, and Mike is constantly at 135+ F. 

We are all charging with the same charger, at the same rate, and have roughly equal ambient conditions.

The only variable is the cells...

Interesting...

Tom


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## SilverFox (Jan 31, 2007)

Oops, double...

Tom


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## wptski (Jan 31, 2007)

Tom:

Was I seeing double? Darn server!

Did you say what the "known" impedance cutoff of the C9000 was? I'm remembering something about 160milliohms.

The Duratrax ICE measures internal resistance on a discharge, so I've been playing a bit with that procedure from the Dallas-Maxim site. If you have a constant charging current source like the ICE and a DMM that has at least three place decimal with a REL/ZERO function, it's easy. Connect to the cell, set REL/ZERO and then apply the 500ma charge. They used 500ms but just look for the initial change. Say it's 20mv, divide by .5 and you have 40milliohms which matches the ICE.

I can use the ICE either way but there should be a simpler way. I've found a self contained digital battery load test but it's only two place decimal, although that good enough to show a cell with fairly high impedance! It displays the voltage with and without the load. It's priced at $32.95.


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## SilverFox (Jan 31, 2007)

Hello Bill,

According to my AC impedance meter, it will accept cells with 419 milliohms, if I hold them in my hand and warm them up a little. The 160 value came from the Maxim site. It rejects 1.245 ohms. It accepts 120 milliohm cells without problems. 

These are the only questionable cells I have. They are from the cycle testing. The high values are from the Sanyo 2500 mAh cells, and the Titanium 2000 mAh cells are coming in at 120 and 90 milliohms.

All of my other NiMh cells are under 50 milliohms, with most of them under 30. The Titanium Power Max 1800 mAh cells are around 17 milliohms.

Tom


----------



## wptski (Jan 31, 2007)

Tom:

How does that compare to checking impedance using the CBA-II?

The digital battery load tester mentioned above won't work as one cell won't power the unit!


----------



## wptski (Jan 31, 2007)

Here's a graph just for comparision. I'm using the DMM TrendPlot with a 2.5Ah Energizer on a Duratrax ICE charging at 1.5A. The hump near the start is where I decided to increase the current from .5A to 1.5A. Termination is clearly seen here.


----------



## SilverFox (Jan 31, 2007)

Hello Bill,

The impedance values are close to what I get on the CBA, but not exact.

For example:
Cells that have 30 milliohms AC have around 40 DC,
Cells that have 17 AC, have around 30 DC,
Cells that have 215 AC, have 270 DC,
Cells that have 120 AC, have around 140 DC, and
Cells that have 113 AC, have around 90 DC.

Not exact, but close.

Tom


----------



## wptski (Jan 31, 2007)

Tom:

It varies up/down, hey? Is your impedance tester made by Kilter Electronics? I did a search and found three made in China by that company.


----------



## SilverFox (Jan 31, 2007)

Hello Bill,

Yes, that's the one. I have the LT-97.

Tom


----------



## wptski (Jan 31, 2007)

Tom:

Your lowest is 200milliohms but the LT-97A has a 20milliohms range. Hmmm, nothing in between! Terrible two's!


----------



## SilverFox (Jan 31, 2007)

Hello Bill,

There is one available from time to time from Great Britain, but I don't remember what the ranges on it are. I have seen it on eBay.

Tom


----------



## wptski (Jan 31, 2007)

Tom:

Yep, I seen that one too! I haven't looked on eBay.


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## Mike abcd (Feb 2, 2007)

SilverFox said:


> Hello Mike,
> 
> There is no doubt that cells with higher impedance will heat up hotter during high current charging. They are also more likely to not signal a strong end of charge termination signal.
> 
> ...



Tom,

With the exception of the Sanyo 2500 and Powerex 2000 mAH, the temps we're seeing are actually very close. My room temps have been at least 2-4 deg F higher than your 68 deg F ambient so add that in to start with.

Are you measuring the temperature at charge termination or the max temp that happens a few minutes later as the internal cell heat reaches the cell wrapper? My post was for max temp reached and I see the temp reach 3-5 deg F higher in the 3-4 minutes following charge termination.

Are you SURE none of your tests terminated on max temp? I suspect that's possible/likely with the improvement you did to the sensor heat conductivity. Take a look at the graph I posted on 4 energizer 2500 AA charged at 2000 mA. It showed a "flat" voltage peak with no -dV yet terminated. I suspect it was on max temp but it seems inconsistent and certainly above Maha's stated 131 F on my unmodified C-9000.

Are you SURE you're catching the peak cell temperatures on all your tests? If so, kudos to you. Personally I found it tough to do when I wasn't data logging the voltage and able to see the voltage peak approaching graphically. I managed it a few times without data logging but had previous charge times to use as a guide and still missed it as often as I caught it. I'm very surprised that you managed it on so many runs in such a short time.

Bill posted temps on slots 2/3 on one run when they were surprisingly low and lower than slots 1/4. It turned out not to be reproducable and was probably due to an unexplained early charge termination. I'd be very interested if your results on the Sanyo 2500 and Powerex 2000 are reproducible.

What's "88" tape? I've found the emissivity of all the cells I've looked at to be high enough to get pretty accurate results. I've tried using black electrical tape in the past on shiny silver brushless motors that have a very low emissivity that causes large IR temp errors. It got me closer but still introduced significant errors since it acted as an insulator and read lower than the surface below. The error gets larger as the surface temp is higher than the surrounding environment.

"They are also more likely to not signal a strong end of charge termination signal. "

If you're referring to -dV as EOC termination, I suspect you are wrong. I'd expect less as the voltage is a function of the temperature rise. The C-9000 seems to have relatively poor -dV detection compared to the BC-900 and I suspect the lower -dV magnitude may be the cause of folks seeing missed terminations on Eneloops.

"It would appear that the C9000 circuitry is adding an additional 10 - 20 F."

That's probably a fair estimate compared to chargers that add far less heat from charger circuitry. Bill's external charging results seem to show that the total temp increase is quite a bit higher though. I think he saw ~30+ deg F cooler when charging cells externally than with 4 AA @ 2000 mA internally.

That of course was the reason for my post in reaction to you telling the poster to "enjoy low temps" on his C-9000.

BTW, you've consistently posted lower temps than Bill or I in general although you seem to also have the "record" at 159 deg F by a big margin. I've suspected it was due to your use of the CBA probe although you've claimed yours was giving you accurate results. It's nice to see you finally using your IR thermometer and the results we're getting are fairly close with the exception of the Sanyo 2500s and Powerex 2000s which are suspiciously low.

BTW, I agree that some of my cells are probably developing higher impedance. I be surprised if they haven't based on all the thermal abuse they've suffered in my C-9000 charging tests 

Mike

PS Actual charging rates on the C-9000 seem to be ~10% lower than the rate displayed during the charge cycle and that often is lower than the rate selected. That's based on calculating the charge rate on the basis of the reported mAH delivered and time.


----------



## SilverFox (Feb 2, 2007)

Hello Mike,

Yes, I am sure I am getting the maximum temperature from the cells. As well as it can be obtained from an IR probe taking a reading off of 88 tape. My IR probe measures a 0.2" diameter at 0.5". I cut 0.25" squares of tape and placed them on the middle of the cells and took the readings at 0.5" away at an angle of roughly 15 degrees off of vertical. This was to minimize the effects of the high case temperatures around the cell. A wider angle of view would pick up case temperatures and would not represent the temperature of only the cell.

I used the tape to insure I was getting similar readings from each cell in spite of the differences in shrink wrap used on the cells. This leveled the playing field. I did not notice a large difference between taking the reading off of the 88 tape as opposed to taking it off of the shrink wrap. There was more of a difference between taking the reading from the top of the cell vs the bottom of the cell.

The termination on a flat voltage peak is called peak voltage termination. I have been advised that it is one of the termination checks that the C9000 uses.

My "improved" unit reads temperature at the bottom of the cell. It terminates on temperature when the cell reaches roughly 135 F. Since the lower end of the cell was always lower than the mid cell temperature, I am certain that I was not seeing a termination based on temperature.

It is good to see that we are coming close in agreement. It will be interesting to see if Maha addresses the issues that have been brought forth.

Tom


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## dekelsey61 (Feb 2, 2007)

Hi Tom! Thank you for all your imformation you give all of us! I am sure Maha will address these issues and put out a revised C9000 charger. My question is what will they do for all of us who bought this first run units? Maha has been very quiet lately! I have seen most of my termination issues with AAA batteries. Thanks again.
Dan


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## Mike abcd (Feb 2, 2007)

Tom,

Get closer to the cell and take the temperature at parallel the surface, not on an angle. My spot size is 1:1 and I put the sensor almost directly (.1") on the cell to get accurate readings.

What was the difference without the tape? We're debating a couple/few degrees here on most of our cells so any difference is significant. My experience with electrical tape as an IR target is not good due to its insulating property.

Again, are you SURE you're always catching the charge termination? Are you tracking after termination until the cell wrapper temp peaks.

If the C-9000 really did "zero dV" termination, it should never miss terminating. I'm very skeptical of that claim. Perhaps it does zero dV about as well as it does dT/dt?

Maha can probably improve things a little by improving case venting and/or a new PCB layout. Getting it right probably means a case fan to dump the heat from the charge circuitry.

I think their real problems will start when summer rolls around and folks start using it in 80 deg F and higher ambient temps.

Are we getting closer to agreement? Frankly I don't see it but my judgment is probably clouded by all my observations being questioned and blamed on high impedance cells here and in other threads and being dragged back through the same topics repetitively.

-dV magnitude on lower impedance cells? Any data to support lower impedance yields a higher -dV?

Mike


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## dekelsey61 (Feb 2, 2007)

Hi Mike,
You are right about when summer hits there will be a big problem with this charger when the room temp. is 80F. The room temp. where I charge my batteries is 68F and I see cell temps of 120F-125F at the end of there charge cycle. I asked this question to a rep. at Maha about higher temps. coming means higher cell temps. coming. They really did not have any comment.
Dan


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## wptski (Feb 3, 2007)

Mike:

Here's a link for the Fluke 60 Series manual:IR. Read under Emissitivity about using tape. As it states, you just wait till it reaches the object temperature. If you put the tape on when the cell is inserted, there's no problem. If you think think that tape is a insulator, what about the wrapper??

I have to agree with Tom as I've seen no difference in IR images when using tape.


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## tacoal (Feb 3, 2007)

I don't understand why some people try to cover the defect of C9000 by these or those factor, not the charger itself.

We blamed BC-900 melting down case before. This didn't mean other charger did not melting down but the ratio in BC-900 is considerably high. The same is when we blame C9000 has the terminatiion problem, it means it has the high ratio rate comparing to other chargers.

I'm not aware if there is a way to avoid the terminating problem on C9000. But for BC-900 melting down case, you can predict what will happen in most case and you could avoid this by some measures.


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## SilverFox (Feb 3, 2007)

Hello Tacoal,

I don't believe we are trying to cover any defects... The C9000 has termination issues. Period.

We are also noticing that some people have cells get hotter than others. We are exploring that.

How do you explain how someone can charge cells without excessive heat, and someone else charges the same brand of cells and they melt the shrink wrap off? 

If the charger was at fault, all cells charged on it would end up with melted shrink wrap. Since this does not seem to be the case, I think it has something to do with the state of health of the cells.

Charging 4 cells at 2 amps with the C9000 will cause the unit to heat up. This heat is passed on to the cells resulting in higher cell temperatures. Once again, the question we are looking at is why do some cells get a lot hotter than others?

I don't think your assessment of the BC-900 problem is correct. There is a marginal component in the BC-900. When this component fails, it either goes open or shorts out. If it goes open, the charger stops working. If it shorts, it charges flat out until it melts down.

There are other "noise" issues with the BC-900, and those you can fix or work around, but the main failure is still a wild card. It is our hope that this marginal component was changed with V33, but there have still been a couple of V33 melt downs.

Tom


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## tacoal (Feb 3, 2007)

Hi Tom,

I agree with you that the failure on C9000 is related to the state of battery's health. It is the same on BC-900.

We all know that BC-900 melted down on some high capacity (>2500mah) batteries. I don't know how you can connect this to the component failure. If it was component failure, the melting down would happen on any capacity battery, not just for *some* of high capacity battery. If it was component failure, why a cooling fan could avoid this failure.

Some BAD batteries, which C9000 thought, are GOOD battery on BC-900, how can you explain this?

As for the glitch, it is a design bug due to the budget design.

My point is the expensive C9000 is a good analyzer, not a good charger.


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## TorchBoy (Feb 3, 2007)

Mike abcd said:


> I think their real problems will start when summer rolls around and folks start using it in 80 deg F and higher ambient temps.


Since you mention it, by chance I have a temperature gauge sitting next to my C9000 and from memory it has been reading room temps of up to 27°C (80.6°F). I haven't thought it might be connected with the problems I've seen with the C9000s but I guess I might make a note it from now on.



tacoal said:


> My point is the expensive C9000 is a good analyzer, not a good charger.


Just a pity that charging is such an important part of analysing, then, eh?


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## SilverFox (Feb 3, 2007)

Hello Tacoal,

There are two main issues with the C9000. First, the unit heats up quite a bit when charging 4 cells at 2 amps. Second is the missed terminations. 

The BC-900 limits the charge rate to 1 amp when charging 4 cells to deal with the heat issues. The 15 minute chargers utilize a fan. I am not sure what Maha is planning on doing about this, but, as Mike has pointed out, the problem will get worse at higher ambient temperatures.

All chargers miss terminations from time to time, but they use a safety timer as a back up to end the charge. Unfortunately, the safety timer for the C9000 is set at 20000 mAh. If it were set for 2700 - 3000 like the BC-900, there would most likely be no issues with this.

Cells that do not exhibit a strong end of charge signal will eventually terminate on the C9000. After 20000 mAh it shuts down.  

Charger design is a compromise. On one hand you want completely charged cells, so you relax the end of charge criteria. The problem with this is that you run the risk of missed terminations and the cells will get hotter during charging. This is great for performance, but you take a hit on cycle life. On the other hand if you tighten down the end of charge criteria, you end up with cells that are less than fully charged. They will remain cool and you will enjoy longer cycle life from your cells, but you will not get maximum capacity or "hot off the charger" performance from them.

It appears that the C9000 was going for a full charge, while the C808M is trying to be very gentle with the cells at the expense of not quite a full charge. A programmable charger allows you to select what you want, but also allows you to screw things up through an improper selection. It would be nice of Maha could tighten up the termination criteria, while still allowing us to utilize a full charge when we want to.

The BC-900 melt downs did not have anything to do with the capacity of the cells. At the time of the introduction of the BC-900 we were using 2300 - 2500 mAh cells, and that is its relationship to high capacity cells. The puzzling thing about the melt downs was that they occurred at the default 200 mA charging rate. This works out to around a 0.08 C charge rate for 2500 mAh cells. 

The whole problem with this is that you can charge a cell continually for a year at 0.1 C and the cell will not heat up enough to melt plastic. The other problem is what happened to the safety timer shut off?

So, we have a cell, that can be charged for a year without heating up at the low charge rate used during the melt downs, suddenly heating up and melting the charger. How does this happen?

Further investigation revealed a component that was at the limit of its heat dissipation limits. It seems that when this component fails open, the charger simply stops working. I believe we had several people complain that their chargers suddenly stopped working when the BC-900 was first introduced. However, if it fails shorted, it bypasses all of the safety timers and termination signals, including high temperature, and charges at the highest rate possible. 

This sound very plausible.

Keep in mind that all of this analysis was done by hobbyist's, and there may be more to it than what we have uncovered. Since La Crosse considers the incidents as "statistically insignificant," there will probably never be an "official" look into this.

V33 came out and the problem seems to have gone away. I have only heard of 1 or 2 incidents with V33 chargers. The official word from La Crosse was that they simply wanted to keep track of the manufacturing date, however we know that the maximum battery temperature cut off was lowered, and the maximum capacity cut off timer was raised slightly. Perhaps they also raised the specifications of some of the components as well.

Tom


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## bp044 (Feb 3, 2007)

Bottom line question: Can I use either the bc-900 or the c9000 with Eneloop or other simular low capcity cells at a charge rate of 1C or slightly lower and not have problems with overheating or missed termination ? Is the solution simply the lower capacity cell usage


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## SilverFox (Feb 3, 2007)

Hello Bp,

I charge my Eneloop cells in both the BC-900 and the C9000 at 1000 mA for AA cells and 700 mA for AAA cells on the BC-900 and 1000 mA for AAA cells on the C9000.

No problems with terminations or hot cells.

Tom


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## bp044 (Feb 3, 2007)

HelloTom ; Two more hot potato questions please. If you had no cells or charger. ,would you choose bc-900 or c9000 ? Eneloop or Hybrids ?


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## dekelsey61 (Feb 3, 2007)

Hi All,
I have a question and hope someone can answer it.
5 days ago I charged up my 4 Sanyo 2700Mah. After sitting for 5 days I put them in my C9000 charger to do a refresh/analyze mode. I set the charger at 1400Ma charge and a 500Ma discharge. The discharge capacity was-
1-2556Mah
2-2548Mah
3-2567Mah
4-2540Mah
All terminated just fine. After they were all done charging back up I took them out of the charger for 1 hour. I then put the back in the charger and did a R/A mode again with the same settings as before(1400Ma charge+500Ma discharge). The discharge capacity for all 4 batteries in the exact same order and for the same battery was-
1-2653Mah
2-2613Mah
3-2636Mah
4-2617Mah
All terminated just fine.
Here is my question- Why did I see higher discharge capacity on the 2nd R/A after being out of the charger for 1 hour than on the 1st R/A after being out of the charger for 5 days?
The first R/A the voltage after the first charge went up to 1.51volts and then rested for 1 hour before discharging. The 2nd R/A the voltage after the 1st charge went up to 1.54volts and then rested before discharging. Did the higher voltage cause the higher Mah reading on the 2nd run even though they went into the rest mode like before?
Thank you very much.
Dan


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## wptski (Feb 3, 2007)

Dan:

First off, many chargers warn you, not to charge a already charged cells which is what you really did. You probably forced in a few more mAh on the second R/A by doing so. The first R/A is more correct as the cells had time to self discharge a bit.


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## dekelsey61 (Feb 3, 2007)

Bill,
Thank you for your reply!


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## SilverFox (Feb 3, 2007)

Hello Bp,

My BC-900 has not melted down, however I take extra care when using it. I have seen how the C9000 handles hot situations, and prefer it. It is my hope that Maha will address the issues that have been raised in this thread, but even if they do nothing, I will continue to use the C9000 with confidence. I continue to use my BC-900, but expect it to melt down every time I use it. I take precautions accordingly and am pleased when it does what it is supposed to do.

I have been using and testing the Eneloop cells for a year now, and have not looked at any of the other low self discharge cells. So today, because of familiarity, I would go with the Eneloop cells. Ask me a year from now and I may have more information on the other cells that have come forward.

Tom


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## SilverFox (Feb 3, 2007)

Hello Dan,

When cells get warmed up you can usually force a little bit extra into them.

If you want a better methodology, first discharge the cells, then run the R&A program.

Tom


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## dekelsey61 (Feb 3, 2007)

Tom,
Thank you for your reply. Thank you again for all you do on this forum for all of us.
Oh, by the way, I did hear that Maha is going to come out with a low discharge battery like the Sanyo eneloop batteries. They told me they will be out in March. I am sure they will be good.
Dan


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## bp044 (Feb 3, 2007)

SilverFox said:


> Hello Bp,
> 
> My BC-900 has not melted down, however I take extra care when using it. I have seen how the C9000 handles hot situations, and prefer it. It is my hope that Maha will address the issues that have been raised in this thread, but even if they do nothing, I will continue to use the C9000 with confidence. I continue to use my BC-900, but expect it to melt down every time I use it. I take precautions accordingly and am pleased when it does what it is supposed to do.
> 
> ...


 Tom thanks for the info.Is your concern about melting with the version 33 as strong as the 32 ?


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## SilverFox (Feb 3, 2007)

Hello Bp,

Since we have had a lot fewer incidents reported with V33, I would say no. However, I am not sure of all the changes so I still think more caution is necessary when using the BC-900 than when using the C9000.

Tom


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## 3rdDerivative (Feb 4, 2007)

I have a second C9000 after my BC-900 failed after two weeks. 

So after a few normal charge test cycles, I put 2 fully discharged AA 2.5ah cells and charged at 300ma. They terminated normally. Had a few extras, so ran a 2nd test. None terminated and pulled them at 3500mah. All were just warm.

Currently running one more test, this time 3 AA 2.5ah cells at 200,300,400 ma charge. Hey, test the limits!

BTW, all the cells so far have terminated at 500ma to 2000ma on C9000. None seems to have any high impedance issues and all charge cool on a C800S.

And the C9000 is light years ahead in built quality over the BC-900, IMHO. Just the display and switches are oblivious improvements. And I "luv" the discharge cycle.


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## TorchBoy (Feb 4, 2007)

3rdDerivative said:


> ... AA 2.5ah cells and charged at 300ma. ... Had a few extras, so ran a 2nd test. None terminated and pulled them at 3500mah. All were just warm.


300mA is pretty close to 0.1C for those cells of 250mA, and after 16 hours that would put a nominal 4000mAh into the cells (or 3600mAh at the 0.9 duty cycle I think the C9000 uses), so they could arguably not have reached a termination point by then. How much did the cells on your first run take before they terminated?



3rdDerivative said:


> Just the display and switches are *oblivious* improvements.


:laughing: Yep, they're pretty good.


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## tacoal (Feb 4, 2007)

Hi Tom,

Thanks for the lengthy reply.



> The BC-900 melt downs did not have anything to do with the capacity of the cells.


Would you point me to the case of melting down on BC-900 with low capacity batteries?

I don't think there are any hardware change between V32 and V33 except for adding the thermistor stand. It is easy to link this to the reduce of melting down case on BC-900.


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## SilverFox (Feb 4, 2007)

Hello Tacoal,

Here you go... but this one was caught early on.

I believe the V32 also had a thermistor stand, so that may not be a difference.

We are still left with the question I asked earlier...

_"So, we have a cell, that can be charged for a year without heating up at the low charge rate used during the melt downs, suddenly heating up and melting the charger. How does this happen?"_

Tom


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## 3rdDerivative (Feb 5, 2007)

TorchBoy said:


> 300mA is pretty close to 0.1C for those cells of 250mA, and after 16 hours that would put a nominal 4000mAh into the cells..How much did the cells on your first run take before they terminated?


Had to take a trip, but did get two of the AA cells at 400ma charge done. One was around 2800+ or so. The other run much longer but terminated at 5000+. Did not write down due the trip rush and had to pull the others. Might try later, but it seems best to charge on C9000 as noted in manual at .33C or higher.


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## wptski (Feb 5, 2007)

3rdDerivative said:


> Had to take a trip, but did get two of the AA cells at 400ma charge done. One was around 2800+ or so. The other run much longer but terminated at 5000+. Did not write down due the trip rush and had to pull the others. Might try later, but it seems best to charge on C9000 as noted in manual at .33C or higher.


MAHA's William Chueh has already stated in the thread or the FAQ one that the minimum charge rate should be changed from .33C to .5C.


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## webfors (Feb 5, 2007)

I've cycled several of my battery sets. The only ones which failed to terminate so far (1000mah default charge current) were old nexcell 1800 mah's which were sitting unused for months. 

After using the 'break-in' mode on them, and cycling them a few more times, only two out of 8 would not terminate consistently. These also happened to be the same cells which showed high voltage and very low capacity (around 1100 mah). So I pitched them.

I'm going to run my energizer, sanyo, GP, and eneloop batteries through a few more cycles and will let you know if any don't terminate. It does seem to be more of an issue with poor quality cells. I can't say if the low charge rate could be a problem since I don't use them. I'm sticking with the .5c recommendation minimum charging current.


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## tacoal (Feb 5, 2007)

SilverFox said:


> Hello Tacoal,
> 
> Here you go... but this one was caught early on.
> 
> ...


 
This is really scientifically insignificant and it is not the melting down. If you said this is melting down, then the C9000 would have many melting downs. 

The earliest V32 didn't have the stand, PCB revision 05. From PCB revision 06, the stand is there.

I have 3 BC-900s and over 100 batteries including some over 10 year old ones. What I did is to push battery hard to make the thermal contact well and put the charger in a slanting position. The melting down never happened. There are some cases of overcharging to 140% for some 700mah AAA batteries and this could be avoided by adding a cooling fan.

If the battery was good enough, every charger would work fine. The battery is not excuse for charger failure. However, if a cell is good on one charger and bad on another one, we know which one is better.


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## SilverFox (Feb 5, 2007)

Hello Tacoal,

I see we are still having a problem communicating...

Let me reword the question this way:

Can you find any AA 2000 mAh, or higher capacity cell, that heats up to 203 F (95 C) or higher, while charging at 200 mA in room temperature conditions?

Tom


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## tacoal (Feb 5, 2007)

I think what you want to say is that BC-900 has design problem even charging current is 200ma. We already agreed on that. But the reason is unknown. You think it is due to the device defect. Supposing you are currect, I don't want to say my opinion again since this thread is for C9000. Talking about too much about BC-900 is not proper.

Supposing the C9000's overcooking is due to the bad batteries too. How can you explain why some BAD batteries that C9000 thought behave well on BC-900, please answer directly.


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## SilverFox (Feb 6, 2007)

Hello Tacoal,

Correct, and we agree. The BC-900 seems to have a component that is on the edge of its limits. Most of the time it works fine. You and I both have V32 units that work fine. However, it is my humble opinion that a charger should never melt down to the extent that the BC-900 has done.

A charger may cook cells and ruin them occasionally, but it should never melt the plastic on the charger and cause damage to the surface that the charger is sitting on. This is unacceptable.

OK, enough on the BC-900.

Moving on to the C9000...

The C9000 is "cooking" cells because it has an aggressive charge algorithm designed to get a full charge on the cells. Also, it runs hot when charging 4 cells at high charging rates.

The cells that miss termination on the C9000 are not necessarily bad, they just have higher impedance.

If the BC-900 misses the end of charge termination signal, it times out. The C9000 will also do that, but it will take a couple of days to do so. The extended overcharge will take its toll on the cells and shorten their cycle life.

OK, let's move on to the case where the BC-900 does a proper termination and the C9000 misses the termination signal. 

If you review the data in the Charger Comparison thread, you will find that the BC-900 charges cells to about 90% full. I think that Maha was going for a more complete charge, and it seems that they pushed things a little too far.

In order to get a fuller charge, you have to charge longer. When you charge longer, it can get difficult to detect the end of charge signal. I expect Maha is looking at what they have in their 800 series chargers, and may consider changing back to that for the C9000. 

Please understand that this is my "best guess." I think Maha is working on this, but we have not heard much from them lately. Charging algorithms often need to be "tweaked" for optimum performance. I love my Schulze charger and think it does a wonderful job of charging. In spite of this, I just found out that I am 3 revisions behind. One of the revisions optimizes NiMh charging. It looks like the best is getting better.

Tom


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## Anders (Feb 6, 2007)

Hello.

I cykled 4 DIGITAL cells, 2000 mAh, (charge 1000 mAh, discharge 400 mAh)
First slot, cykle 2, didn't terminate, i took out the cell at 10A, it was hot.
Fourth slot, cykle 3, didn't terminate, took out the cell at 5555 mAh, it was hot.
The cells was bought 2005 in September, maybe 30-40 cykles on them.
The other two slots terminated and is now in the last discharge mode.

The first cell showed HIGH now after resting 15 hours, the fourth cell terminated after a couple of minutes when i put it in the C-9000, just a couple of minutes after that i removed it, in refresh & analyse mode, same settings as the others.

All of this cells terminate properly in my MH-C808M.
*
*

Anders


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## SilverFox (Feb 6, 2007)

Hello Anders,

It looks like you used excellent settings, and it still did not properly terminate...

Bummer...

Tom


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## n3eg (Feb 6, 2007)

Since I've been drawn into this by being quoted...

I had a near-meltdown with old and somewhat abused 1800 Eveready batteries charging at 1000 mAH. No surprise. I've had batteries get hot and explode on a Cadex 7000 series at work, and I know the Cadex terminates on overvoltage (high cell impedance). I've had 7 year old Motorola batteries boil on their chargers once in a while. Stuff happens, especially with old batteries. I've always suspected that batteries can "run away" just like the old thermal runaway in transistors. How else can I explain 1200 mAH Nexcells melting down when trickle charged at 100 mA? One fun example is with NiCd button cells. Good ones cycle fine at 0.2C, but bad ones will always explode.

I posted in another thread about "Digital" 1000 mAH AAAs measuring in the mid 600s. My "Digital" 2100 mAH batteries measure in the mid 1500s. Hot when charging at 1000 mA? Again, to me, no surprise. Cadex's default charge/discharge rate is 0.5C for NiMH, and even then they get a little warm.

I've never had any battery get hot on my BC-900 charging at 200 mA. Everything terminates around 1.47-1.5 volts. 500 mA works well too. I have, however, started junking...excuse me, recycling...cells at Motorola's recommended 80% or less capacity.


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## tacoal (Feb 7, 2007)

Hi Tom,

Please stick to the topic to avoid drifting away.



SilverFox said:


> If you review the data in the Charger Comparison thread, you will find that the BC-900 charges cells to about 90% full. I think that Maha was going for a more complete charge, and it seems that they pushed things a little too far.


 
Did you mean BC-900 is undercharging the cell?

When negative voltage happens, the cell is already in the state of overcharging. So Maha is trying to overcharge the battery to get more capacity out of cell in its design.


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## SilverFox (Feb 7, 2007)

Hello Tacoal,

Interesting isn't it...

Since I think that all of the chargers compared in the Charger Comparison thread utilize negative delta V, it would appear that there is more to it than a simple measurement.

Tom


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## wptski (Feb 7, 2007)

Okay, -deltaV is a overcharge condition but lets say that you increase the value from 5mv to 10mv. It would be easier to detect I guess but aren't you going to overcharge the cell more at the same time?


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## NiOOH (Feb 7, 2007)

wptski said:


> Okay, -deltaV is a overcharge condition but lets say that you increase the value from 5mv to 10mv. It would be easier to detect I guess but aren't you going to overcharge the cell more at the same time?


 
That's correct. The larger the magnitude of -dV, the more overcharge there is. Although -dV is not recommended for charge termination of NiMH cells, when it is used the -dV magnitude should be limited to a max of 10 mV per cell.


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## wptski (Feb 7, 2007)

NiOOH said:


> That's correct. The larger the magnitude of -dV, the more overcharge there is. Although -dV is not recommended for charge termination of NiMH cells, when it is used the -dV magnitude should be limited to a max of 10 mV per cell.


NiOOH:

I actually knew that! It has been suggest that they fall back to the 800 Series termination method which charges to a somewhat less percentage than the C9000. It's been metioned here that MAHA was trying to get a near full charge. If they were using 3-5mv, how's that a near full charge??

What I may be asking is, how is the percentage of charge controlled using -deltaV on Ni-MH other than increasing the value of detected voltage drop?


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## SilverFox (Feb 7, 2007)

Hello Bill,

I think the C808M uses peak voltage detection as its primary termination method, but I don't know any of the details.

There are a number of variables involved including sample rate and number of samples.

Tom


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## wptski (Feb 7, 2007)

SilverFox said:


> Hello Bill,
> 
> I think the C808M uses peak voltage detection as its primary termination method, but I don't know any of the details.
> 
> ...


Tom:

So that's dV/dt and that would occur after dT/dt but before ZeroDeltaV, correct?


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## SilverFox (Feb 7, 2007)

Hello Bill,

It may be that temperature and peak voltage occur at about the same time.

Tom


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## webfors (Feb 8, 2007)

sorry to go off topic. Since c9000 heat was brought up a few times, and I noticed this myself when charging at >= 1.5amps, I decided to get creative.

I solved the heat issue by placing a small fan on top to *pull* the hot air out from over the coils:

http://webfors.com/pictures/c9000/

What a difference it makes. I know a fan was mentioned previously, but every instance I've read mentioned *blowing* air onto the cells, which could interfere with the heat sensors.

Those coils (4 of them) generate a lot of heat, which as mentioned previously, contribute to greater cell temps. Pulling that hot air out makes a huge difference and took just a few minutes. That blue stuff is the stuff you use to hang things on the wall with that you can get at staples for $1... works like a charm 

Now, on to try that 2amp charge current for heat comparison. Sorry, I only have fingers to test with.. no fancy temp detecting equipment in my house =)


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## Mike abcd (Feb 8, 2007)

Hello Tom,



SilverFox said:


> Hello Tacoal,
> 
> Correct, and we agree. The BC-900 seems to have a component that is on the edge of its limits. Most of the time it works fine. You and I both have V32 units that work fine. However, it is my humble opinion that a charger should never melt down to the extent that the BC-900 has done.
> 
> ...



Like you, I'm running a BC-900 v32 without issues. I've had it for 18+ months of heavy use.

A charger that "may cook cells and ruin them occasionally" is also unacceptable to me and thankfully I've never had that happen in the 18+ months I've had the BC-900.

The BC-900 also gets AA batteries hotter than I like charging 4 AA cells @ 1000 mA or 2 cells over 1000 mA so I usually use lower rates or less cells and still have never had a missed termination.

For the last year, I've also been using a Lenmar Mach 1 Gamma charger that uses an internal fan to cool the charger circuitry (not the cells) and terminates on dT/dt. It keeps the cells VERY cool compared to anything else I've seen but only fast charges AA/AAA to ~80/75% capacity compared to the BC-900. I usually fast charge on the Lenmar and then complete charging on the BC-900 at .4-.5C. No missed terminations and very low cell temps. I wanted the C-9000 for its higher rates on both charging and discharging but can't accept the high temps and missed terminations.



> Moving on to the C9000...
> 
> The C9000 is "cooking" cells because it has an aggressive charge algorithm designed to get a full charge on the cells. Also, it runs hot when charging 4 cells at high charging rates.


I've got to strongly disagree with you here. the fast charge is not DESIGNED to be "aggressive". Let's look at the C-9000 specs.
- dT/dt termination
- peak voltage (0 dV termination)
- 5 mV -dV termination

None of these is "aggressive" IMHO.

BTW, I doubted it tries to do "peak voltage" when you posted it but it's in the C-9000 specs at TD.

Unfortunately the reality is very different than the specs. 

It clearly fails to implement proper dT/dt (1.8 C / minute) based on the cell temp rises that Bill and I have monitored.

The "5 mV -dV" is measured on the "resting pulse" and seems equivalent to 12-15 mV -dV measured on the charging pulse.

Same thing for "peak voltage". I've seen it terminate a charge with 4 AA @ 2000 mA on zero V slope but never at lower charge rates or with fewer cells so I'm forced to conclude it terminated on max temp as the cells got VERY hot (135+ F). The missed terminations are also strong evidence that the "peak voltage" termination is not working as it should stop the charge termination failures (gross overcharges of 130+%) that many folks have seen.

I also don't see any significant increase in capacity tests compared to the BC-900 when the cells are pulled at the "DONE" indication. It's not the charge algorithm that's cooking cells, it's the heat from the charging circuitry. Bill saw cell temps ~30 deg F cooler when charging cells externally compared to slots 2/3 internally. Same charge algorithm, same charge rate.

While we're on the C-9000 charging though, a rant...

What was Maha thinking with the 200 mAH "top off" charge that appears to always get done??? I can see using it after dT/dt termination on AA cells as Duracell advises a 5% C top off after dT/dt (1/2 hour at .1C). But the C-9000 always does it even after terminating on -dV!!! 2500+ mAH AA cells can probably tolerate it well but it's a 25% additional overcharge on an 800 mAH AAA!!!



> The cells that miss termination on the C9000 are not necessarily bad, they just have higher impedance.


You seem to always blame missed terminations on higher impedance cells. Do you have any evidence to support that??? How do you explain the multiple reports of C-9000 missed terminations on Eneloops?

I've asked before whether you had evidence that lower impedance cells make it easier to properly detect charge termination. I'm not trying to give you a hard time. It's just not intuitive to me.

- Lower impedance cells have less temperature rise so dT/dt should be tougher.
- Lower impedance cells have less voltage increase during charge. Since the voltage drop used for -dV is caused by an increase in cell temperature, I'd expect the smaller voltage and temperature increases to result in a smaller and harder to detect -dV.


> If the BC-900 misses the end of charge termination signal, it times out. The C9000 will also do that, but it will take a couple of days to do so. The extended overcharge will take its toll on the cells and shorten their cycle life.


20,000 mAH for maximum charge termination on the C-9000. What were they thinking???


> OK, let's move on to the case where the BC-900 does a proper termination and the C9000 misses the termination signal.
> 
> If you review the data in the Charger Comparison thread, you will find that the BC-900 charges cells to about 90% full. I think that Maha was going for a more complete charge, and it seems that they pushed things a little too far.


I won't beat a dead horse here. Others have already correctly pointed out that the BC-900 overcharges NiMH as does any charger that uses -dV. Other chargers may overcharge more but the C-9000 doesn't appear to be one based on the capacity measurements done after fast charging only.


> In order to get a fuller charge, you have to charge longer. When you charge longer, it can get difficult to detect the end of charge signal. I expect Maha is looking at what they have in their 800 series chargers, and may consider changing back to that for the C9000.
> 
> Please understand that this is my "best guess." I think Maha is working on this, but we have not heard much from them lately. Charging algorithms often need to be "tweaked" for optimum performance. I love my Schulze charger and think it does a wonderful job of charging. In spite of this, I just found out that I am 3 revisions behind. One of the revisions optimizes NiMh charging. It looks like the best is getting better.
> 
> Tom



IMHO, the C-9000 had the potential to be a GREAT charger. It's much larger size compared to most competitors should have allowed it to avoid the common issue of charger circuitry heating of the batteries. Unfortunately, they implemented minimal case venting, no internal cooling fan and put some of the power transistors directly under the cells, etc. Firmware revisions can't fix it IMHO and in its present form, it's a poor to mediocre charger at best.

It's the 3rd time I've been burned (almost literally true) by Maha on a charger and I won't purchase another until I see LOTS of user reports first, no matter how attractive it looks on paper.

Mike


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## Mike abcd (Feb 8, 2007)

wptski said:


> Mike:
> 
> Here's a link for the Fluke 60 Series manual:IR. Read under Emissitivity about using tape. As it states, you just wait till it reaches the object temperature. If you put the tape on when the cell is inserted, there's no problem. If you think think that tape is a insulator, what about the wrapper??
> 
> I have to agree with Tom as I've seen no difference in IR images when using tape.



Hi Bill,

The cell wrapper is definitely an insulator and I see higher temps after the fast charge terminates as the internal higher temps reach the surface. Measuring temps there is just the best I can do.

I suspect electrical tape doesn't result in large differences especially when temps are stable or changing slowly and any error is reduced the closer you are to the ambient environment.

I'll definitely defer to you here with your fancy IR camera, drool  but I'm surprised you cantt even see the outline of the tape when cell temp is changing fairly rapidly near the end of charge. How big of a temp difference would it take to see it with the cell surface temp around 135 F?

OTOH, if you can't see it, it also means the tape doesn't help in getting more accurate readings... Have you ever seen higher temps with your IR camera on the adhesive tape except when using it on surfaces with grossly low emissivity such as chromed polished surfaces?

Mike


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## webfors (Feb 8, 2007)

Mike abcd said:


> 20,000 mAH for maximum charge termination on the C-9000. What were they thinking???Mike



With all the user selectable options this charger comes with, they could have simply added one more, maximum charge capacity or max charging time. Half the issues we have with this charger would be solved by simply allowing the user to enter max charging time, or max charging capacity to avoid cooking cells to 20k mah in the event of a missed termination. 

That being said, I have yet to experience these infamous missed terminations on healthy cells with the c9000. Only two missed terminations so far on some really crappy old nexcell 1800mah's that registered around 900mah, and very high voltage. The funny thing is, now that I'm 'illuminated' to the concept of missed terminations, I've seen more on my other chargers in the past week then I have with the c9000. My 401fs missed several with my 2700 sanyos, and my 808M missed 3 with some sub-par lenmar AA's.. man did they get *hot*, I had to put gloves on to pull them out.

BTW: with that fan pulling the hot air away from the coils, I just charged 4 AA eneloops at 2amps. The batteries terminated correctly, and about the same temps as when they come out of my 808M at 2amps. Just slightly warm to the touch. So this tells me the coils are the biggest contributer to high cell temps. A simple fan design by maha could have solved any potential heat issues, or at least better case venting. I'll be leaving that fan on permanently until Maha comes out with the c9000 revision II, after which I will ask for a replacement under my 3 year warranty 

Until then, it's a great tool to have around. And *NO* I will never use a bc900 again after it melted down and damaged my new PSB monitors. The c9000 may have some flaws, but they pale in comparison to melted blue and white plastic goo, and bubbling batteries that needed to be pried from the death grip of the bc900 


I have a Q for you engineers/geeks/techies... does a 2 channel charger that charges in pairs have less chance of missed terminations, or does charging two batteries on the same channel make any difference with respect to -dv? I'm asking because my lp4000n has never missed a termination, and has never made a single battery more then 'warm' in the 1.5 years I've used it.


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## wptski (Feb 8, 2007)

Mike:

There's no difference between the black tape and a cells wrapper or at least the ones I tried it on! The emissivity of the cells wrapper and the tape must be the same. Funny that you should mention chrome. If you have PVC plumbing in your kitchen, bathroom, etc. this IR imager will find a partial/solid blockage like you wouldn't believe.  Chrome pipes, traps, etc. are another story. They vary with reflections because they are round and the temperature varies from hot to cold. Yes, tape can be "clearly" seen on chrome as a sharp outline.


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## SilverFox (Feb 8, 2007)

Hello Mike,

You may be right. “Aggressive” is a very strong word. Let me just say that the C9000 appears to do a more complete job of charging than several of the other chargers available, including the BC-900. 

Let’s look at some numbers. The BC-900 came in on the charger comparison with 1.934 Amp Hours, 2.355 Watt Hours, and ran for 116.1 minutes. The C9000 comes in at 2.081 Amp Hours, 2.511 Watt Hours, and ran for 124.9 minutes. This is almost as good as the Schulze. Charge rates were 500 mA on the BC-900 and 1000 mA on the C9000. Cells were pulled as soon as the BC-900 indicated Full, and as soon as the C9000 indicated Done. Cells were rested 30 minutes after charging before the discharge test. Discharge rate was 1000 mA. Cell temperatures did not exceed 125 F on either charger. The same Titanium 2400 mAh cells were used for both tests.

I can understand your confusion on the role impedance plays on charging. Higher impedance cells heat up and the voltage rises to a higher level, however as the cell heats up, the impedance can drop and the voltage may plateau. If this dynamic is going on near the end of the charge, it is possible to end up with no end of charge termination signal. On top of that, if the charge rate is moderate, the cell temperature will not increase to the maximum temperature cut off either.

It is a very interesting exercise to monitor the impedance during the charge, especially with cells that are in “questionable” condition.

In this day and age, it is unbelievable to have a manufacturer listen to their customers and try to accommodate them. The C9000 seems to be Maha’s answer to the BC-900. When the BC-900 came out, a frequent question was if this charger could be used to charge C and D cells. I am under the impression that the 20000 mAh capacity limit was supposed to be for “our” benefit. It is too bad that this seems to have come back to haunt Maha. I hope Maha will be able to resolve the “issues” with the C9000 without having to eliminate this feature. C and D cells are very prone to false peaking when new. It would be very nice to be able to do a standard charge and a standard discharge on new cells of this size.

You keep throwing out that your cells are being overcharged. Since state of charge is defined as discharge capacity, it is easy to determine if your cells are being overcharged or not. As a matter of fact, there are standards in place to determine this.

In order to determine the capacity of a cell, you take a new cell, charge it at 0.1C for 16 hours. This is called a standard charge. Let it rest, then discharge it at a 0.2C rate. This is called the standard discharge. The result is the standard capacity of the cell. 

We hope that this capacity comes close to what the label on the cell states as its capacity, but sometimes this is not the case.

Now we have a benchmark to compare to.

You can then proceed to charge at whatever rate you care to, terminate the charge however you think it should be terminated, then you can do a standard discharge to determine if you were able to match the discharge capacity of the standard charge.

If you would like to study the effect of different discharge rates, you can do a standard charge, followed by a standard discharge to get your benchmark. Now you can do another standard charge and discharge at a rate that you are interested in. Now you have another benchmark to compare to. Once all of this information is in place, you can go back to your normal charge rate and see how the discharge capacity compares.

When you overcharge cells, your discharge capacity will exceed the standard charge/standard discharge capacity. If you overheat your cells to the point of damage, the capacity will be less. If you manage a full charge, the capacities should be nearly the same.

So, are the cells actually being overcharged? No! 

The cells are heating up during the charging process. What causes cells to heat up? Hmm, now we are back to considering impedance along with the other variables such as charge rate…

It is my humble opinion that the C9000 is a great charger, but it has a few quirk, especially with “older” cells that are not in their prime. 

Can it be improved upon? Yes. We all hope that a few minor improvements can be made to take care of most of the issues, but there will always be room for the “professional” model that incorporates all of our suggestions.

Tom


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## wptski (Feb 8, 2007)

As Tom knows I just got a battery tester, so-called that measures a cell/battery impedance using the AC method similiar to Toms unit. This one will log voltage/impedance and download to a PC. The software is a bit lame and I may have to learn how to graph in Excel after importing a basic file!  

I've been playing with different cells. I have a old 2Ah PowerEx cell that measure 120mOhms which is a bit high. I discharged it at 1A on the C9000.

Discharge
Warm off the charger=90mOhms
Cool=107mOhms

Charge
Warm off the charger=70mOhms
Cool=110mOhms

Like Tom states above when a cell gets warm, impedance drops. I'll be trying that again with cells in better shape shortly.

In Post#60, I tried to forced a miss termination on some 1.8Ah PowerEx cells by charging at .33C. One terminated on time, two were late and one never did. I stopped it at 6C. Three cells measured 24mOhms and the one that missed termination measured 27mOhms. High impedance wasn't the cause of this missed termination here.

So if a cell's impedance drops as it heats up and the C9000 heats up the cells, what happens then? Low impedance is supposed to be good, less voltage drop under load and less heat generated by the cell itself while charging too.


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## bob_ninja (Feb 9, 2007)

SilverFox said:


> Hello Mike,
> In this day and age, it is unbelievable to have a manufacturer listen to their customers and try to accommodate them. The C9000 seems to be Maha’s answer to the BC-900. When the BC-900 came out, a frequent question was if this charger could be used to charge C and D cells. I am under the impression that the 20000 mAh capacity limit was supposed to be for “our” benefit. It is too bad that this seems to have come back to haunt Maha. I hope Maha will be able to resolve the “issues” with the C9000 without having to eliminate this feature. C and D cells are very prone to false peaking when new. It would be very nice to be able to do a standard charge and a standard discharge on new cells of this size.
> Tom



True, it is a nice feature to be able to charge higher capacity Cs and Ds. Good. The implementation of this feature was screwed up. Clearly the charger is designed for AAAs and AAs. As such its built in default limit should be for those types, say 3Ah or even 4Ah. That is the reasonable limit for AAs today and some time into the future.

Next, the charger should have a feature to override this default limit to up to 20Ah. So if I manage to connect Cs and Ds then I still have to take a specific action to program the charger to increase the limit. That way you don't end up with accidental 20Ah put into AAAs and AAs. Users CHOOSES to increase the limit because user is using some bigger cells, thus responsibility shifts to the user.

I am not bashing Maha. This is a simple oversight. Happens all the time with high tech products. Should be a simple adjustment.

I do think it is an important safety feature. Considering the exploding LiIons and metling NiMhs, as well as all the other complex issues (older cells with higher impedance, temps, etc.) any new smart/quality charger must have some sort of means to limit the total charge, either reasonable default (like 3Ah) or programmable setting. That is the only way I can walk away from the charger and not have to worry about overcharge dangers.


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## knightc2 (Feb 10, 2007)

I want to thank everyone for all the great info on the c9000. I decided to wait and got the 800S and a bunch of Eneloops instead. I really wanted a good charger for analyzing and break-in, but I think I will wait and see what Maha does here. Maybe a firmware update coupled with using a fan to cool it down might be a suitable solution. Anyway, I am just a little leery about the failed terminations and leaving the charger unattended for any length of time.


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## wptski (Feb 10, 2007)

Here's a impedance/voltage graph of a 2.5Ah Energizer cell on the C9000 at 2A logging at 1 sec interval. Notice the area where the impedance drops to zero at times. I have no idea what it all means yet. Just thought that I'd post it the generate a bit of conversation on impedance! 

I may find a better way later to display these graphs using Excel.


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## SilverFox (Feb 11, 2007)

Hello Bill,

Very interesting...

I knew impedance is dynamic during charging, but I really didn't expect as much variation. There is an interesting pattern developing near the end of the charge.

What happens if you go to a 1 minute interval?

Tom


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## cdosrun (Feb 11, 2007)

Bill, forgive my ignorance, but how can you test the impedance of a cell whilst it is on charge without the results being affected by the charging circuitry? Does it test the impedance between the charging pulses or, being AC, is it just relatively unaffected by the voltage from the cicuitry? Even with the latter, I don't see how the relative impedance of the transistorised power supply in the charger doesn't affect the readings. I'm sure it is just a result of lack of knowledge in this field.

Thank you,

Andrew


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## SilverFox (Feb 11, 2007)

Hello Andrew,

AC impedance is not supposed to be effected by charging or discharging loads. However, this may be in reference to constant current loads. It looks like some "noise" develops with pulse currents. This may smooth out with a different sample interval.

I think the best measurements would come with data taken during the off cycle, but I don't think Bill is set up to do that kind of timing.

Tom


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## cdosrun (Feb 11, 2007)

Tom,

thank you for that, I was wondering. It is quite possible that the impendance of the charging circuit is having an affect then. Could the change seen on the graph have been the effect of a top-off charge at that point, or would the charger still have been in bulk charging mode?

I suppose the only real way of doing it was as described by Will(?) from Maha by timing the test with the absence of pulses. As you said, it is unlikely Bill has the facilities of that. Interesting nonetheless though, I hadn't considered impedance changes in the battery previously. I am interested in keeping an eye on this thread because I am still amazed at the amount of skill and knowledge on CPF & that is shared so freely (the way it should be .

Andrew


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## wptski (Feb 11, 2007)

Tom:

This is another 2.5Ah Energizer at 2A again but at one minute interval this time and it does smooth it out a bit. Funny thing is that I have four of these 2.5Ah Energizers. They laid uncharged after a usage and I noticed that one or two had a very low voltage. I assume that I have some of the cells that have a high self discharge rate! This cell took in 2372mAh. As you know, discharged cells are supposed to have a higher impedance than charged cells. Well, this cell had 25mOhms before charging and after cooling, it had 30mOhms. It would nice if this was a way to detect cells with a high self discharge rate! There is something odd about it as every other cell that I checked before/after read as the book states.


Cdosrun:

The first graph I’m unsure of how long it ran before I stop it but this one I allowed it to make at least one or two reads after showing DONE. It has audible beep whens it reads.

Hardly anyway to read just on the off pulse, let alone any other type of reading. The PWM makes it difficult










I put them both together for comparision.


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## SilverFox (Feb 11, 2007)

Hello Bill,

That did smooth things out. I don't know if a longer interval would help or not. Want to try one at 2 minute intervals?

It looks like the impedance remains somewhat level until the cell heats up at the end of the charge. It then drops a little. Once the charge has completed, it heads back up.

I saw a graph of impedance vs state of charge. It did show increased impedance when the cell was fully discharged and also when it was fully charged, but I remember the difference only being around 0.005 ohms.

Tom


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## wptski (Feb 11, 2007)

SilverFox said:


> Hello Bill,
> 
> That did smooth things out. I don't know if a longer interval would help or not. Want to try one at 2 minute intervals?
> 
> ...


Tom:

Yep, I can do a two minute inteval but it's going to be a different brand and capacity of cell. Since that was done outside of the charger, it happened to check the temperature right when it was DONE at 108F


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## wptski (Feb 11, 2007)

Tom:

A 2.3Ah Duracell cell at 2A with a two minute interval. Oddly, the cell measured 34mOhms before charging and 39mOhms afterwards! Seems that different brands have a somewhat look different!

I've added a graph of the same cell after discharging and charged at 2A on the Duratrax ICE which uses constant current, no PWM.

The sharp increase at the end is where charging stopped and I allowed it measure twice using the same two minute interval as the other graph.

I've had two 2.3Ah Duracells increase in impedance after charging which is the opposite of what it's supposed to do!


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## webfors (Feb 12, 2007)

FYI: I've cycled all my batteries a couple of times each in the c9000. Battery collection consists of:

AA's:

Sanyo 2500 x 8
Energizer 2500 x 16
Energizer 2200 x 4
Powerex 2000 x 8
Powerex 2300 x 4
Powerex 2700 x 4
*Nexcell 1800 mah 
*Lenmar 2450 mah

AAA's = haven't tested any yet. Will do this week sometime.

I used a .5c charge rate for all, and all terminated perfectly, except the nexcells and Lenmars, which I have determined are ready for the recycle bin. Before sending them off to the great unknown, I charged them in my 808M, and they experienced the same missed terminations and high heat they experienced in my new c9000. 

Moral of the story is, it's definitely an issue with the quality/health/state of the batteries, for me anyways. Therefore, I consider this issue closed, in my mind of course, and have full confidence in the c9000. That being said, obvious precautions should be taken, as with any charger. Especially one that provides the possibility of pumping 20k mah into a AA battery.

side note: tested the efficiency of my chargers by charging in each, then discharing at a rate of 1000ma, using the same 4 batteries. The edge (in terms of discharge capacity) goes to the 204f. Not by much, but surprising nonetheless. The 204f and the lp4000n were always my favourite due to the very low heat generated on any charge cycle.. now I have a new reason to love them now that my c9000 has confirmed how well they work 

Chargers I own: lp4000N, 808M, and c204f, E15.


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## SilverFox (Feb 12, 2007)

Hello Bill,

The ICE gives a much cleaner graph. That's nice.

Tom


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## PhotoWiz (Feb 15, 2007)

I'd like to know if there is anything inherently bad about slow charging. I understand that 1) it takes more time and 2) that it can cause termination failures on some chargers. But is slow charging problematic aside from these concerns?

I have two chargers, both MAHA — the C401 and the C9000. Somewhere I saw a post from SilverFox that a charging rate of 0.5C to 1.0C was ideal. Is that just with the C9000 because of termination issues? As I recall, the original recommendation was updated from 0.33C to 0.5C because of termination failure.

If I use my 401 on slow charge, I can't charge anywhere near 0.5C. I've also learned that on fast charge, the 401 does an uneven charge and also can cook the cells. So, is my 401f obsolete for my typical batteries (2300-2650ma capacity?) So far, using the slow charge on the 401 seems to do a good job (as verified by a discharge test on my C9000.


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## webfors (Feb 15, 2007)

using the slow charge on the 401 increases the chance of a missed termination. Having said that, I rarely ever experienced one on my 401, however it could have missed and I never noticed, since there is a max timer on the 401 that will prevent the charge cycle from continuing forever.

So it's not obsolete, and will continue to work well for years for you. However, if you were shopping for a charger there are better chargers out there for less money. I gave away my 401 to a family member, since I rarely used it anymore. My favourite charger at home is my 808M, and for the road I like my RipVan LP4000N. Both do an excellent job of fast charging, with *very* little heat. The RipVan being substantially cheaper then the 401, and charges must faster.

My c9000 is used mostly for analysis, and is always being used lately, since all my batteries had to take a turn in it


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## SilverFox (Feb 15, 2007)

Hello PhotoWiz,

Welcome to CPF.

The biggest difficulty with slow charging is the weak termination signal. Slow charging is easier on your cells, and can often give a more complete charge.

Many people only slow charge.

Performance wise, the major argument against slow charging is that it forms large crystals. This increases the internal resistance of the cell and limits the usable current draw from it. In high drain applications, you want to charge at high rates. In low drain applications, slow charging works great.

The actual defination of "high drain" is somewhat illusive. Some suggest that when you get to a 2 hour discharge you are in the high drain area, others stretch that out to a 1 hour discharge. Everyone seems to agree that if you drain your batteries in under an hour you are in the high drain area.

The question of termination is difficult. The easiest way is to use a timed charge, and do a complete discharge each time before charging. This works well, but will waste cycle life. NiMh cells last longer if you don't do a 100% discharge with every cycle.

This also eliminates your ability to top off the cells before use.

This brings us back to needing a way to terminate the charge.

The battery manufacturers state that you need to charge at 0.5 - 1.0 C to get a strong termination signal. Even at those rates the signal is sometimes missed, depending on the condition of the cell.

Fortunately, extended overcharging at low rates does less damage to the cell than overcharging at higher rates. So when a termination signal is missed at a low rate, it usually is not a real big deal and the charger simply times out.

I was taught that you terminated slow charging with temperature. When the cells got "warm," they were charged. Many people use a temperature rise of 10 F over ambient as a termination signal. The problem with this is that as a cell ages, it developes higher internal resistance. The higher internal resistance causes the cell to heat up faster. You can have a cell that is "warm," but is not fully charged. If you are trying to match cells in use, you will have reduced performance, even though you thought your cells were fully charged.

When I get new cells, I do a forming charge at 0.1C for 16 hours, then try to charge at 0.5C or higher. If I find myself doing a slow charge, I make sure I set a timer so I can check to make sure the charge has been terminated.

I also recycle cells that have fallen below 80% of their initial forming charge capacity. 

It seems like most chargers will work with cells that are in good condition. The problems come with brand new cells, and those that are wearing out.

Tom


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## PhotoWiz (Feb 15, 2007)

Thanks Tom,

That helped a lot. Now, let's see, I have two typical applications — a small flash and a radio transmitter/receiver, all of which take four AAs. The radio transmitter/receiver can go all day and not be exhausted, so it's obviously a low drain application. The flash I'm not so sure about. In use, it lasts more than two hours, but its instantaneous drain would be quite high. If I kept flashing the flash as fast as it could recycle for an hour, I don't believe there would be much left (including the flash, which is probably smoked at that point!) But the drain rate is high and I do want recycle time to be as fast as possible. That suggests that I want to use the higher charge rate — right?

If you charge at a high rate — doesn't the trickle charge make up for the incomplete charge if you leave the cells in the charger for a time after they are finished? Or does that then form large crystals too?

Once crystals have been formed in a cell, can that be reversed by fast charging?

Thanks again for your help,

Bill


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## SilverFox (Feb 15, 2007)

Hello Bill,

Gee Whiz... now you go and muddy the water up with pulse loads...  

I view pulse loads as high drain applications. I look at it from the perspective that if the pulse was sustained, how long would the battery last. I am not sure it is technically correct to look at it this way, but it is my personal preference.

A trickle charge is used to minimize the self discharge rate of the cell. The top off charge is what brings the cell to a full charge after a rapid charge. Some chargers do not utilize a top off charge and go straight to a trickle charge. 

Large crystals are formed by repeated slow charging, extended trickle charging, and extended self discharge. When they get big enough we end up with voltage depression, which is often referred to as the "memory effect."

The large crystals are broken up during discharge. It is recommended to do a full discharge (down to 0.9 - 1.0 volts per cell) around every 20 cycles or at least once or twice a year to eliminate any build up of large crystals. In "critical" high drain applications, it is recommended to store cells in a discharged state and to cycle them through a charge/discharge cycle every 30 days. This minimizes any large crystal growth from self discharge, yet seems to keep the chemistry "fresh."

It seems that the low self discharge cells, like the Eneloop cells, have an improved separator with a higher dielectric strength. It is believed that this slows down the interaction within the cell and slows down the self discharge rate. It is also speculated that this will slow down the large crystal formation. This is new technology and it is hard to find information on how it works.

Tom


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## PhotoWiz (Feb 15, 2007)

Thanks Tom,

I guess I overlooked the forum rule that says that newbies can only ask easy questions. I'll try to do better in the future!

I do appreciate the help. I've been reading through this forum and several others — and I'm sure all the pieces are there. I was just having difficulty putting all those pieces together into a comprehensive summary.

Bill


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## mbvdlza (Mar 5, 2008)

So guys, was there every anything else to be said here?
Was a newer release every made of the c9000, this thread was like a movie to, and the end is very abrupt...


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## SilverFox (Mar 5, 2008)

Hello Mbvdiza,

Welcome to CPF.

Yes. The "improved" C9000 is all that is available now. I believe you can search for a review of the C9000 in the reviews section to get some details on what changes were implemented.

Tom


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## mbvdlza (Mar 11, 2008)

Thank you very much.
I ordered/bought the C9000 a few days ago, have already used it on 5 sets of cells of different brands and ratings, and all seems perfect!


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