# A look at slow charging



## SilverFox (Oct 27, 2007)

“What is a good rate to charge my NiMh cells?” and “Is this charger good?” are frequent questions that come up around here. Slow charging has been around forever, and it is used in determining cycle life. However, there is a provision in the testing standard for “Accelerated Test Procedures,” when testing for cycle life. The accelerated procedure involves charging and discharging at 1C. The goal is to achieve more than 500 cycles. The accelerated test procedures have a footnote that states that 1C charging should be done for 1 hour, or with appropriate charge termination, as recommended by the manufacturer.

The next step is to review what the battery manufacturers have to say about “appropriate charge termination.”

All of the battery manufacturers recommend charging at either 0.1C for 16 hours, or in the range of 0.5 – 1.0C with proper charge termination. They list peak voltage, change in temperature with respect to time, and total temperature rise as the preferred termination signals, but also recognize that –dV can also be used. 

NiCd charging started with simple timed chargers. From there, they realized that NiCd chemistry was fairly robust, and most of the time cells were being charged from more, or less, empty. They then advanced to 3 or 5 hour charging. Realizing that there was a voltage drop as the cell reached full charge, the fast chargers were ushered in. Now we had 0.5 to 2 hour chargers available. The chip manufacturers jumped in and gave us an abundance of charging chips that allowed us to select charging rates and utilized –dV to terminate the charge.

When NiMh cells became available, the charger manufacturers realized that they could use the same NiCd chargers to charge NiMh cells. However, further study indicated that the overcharging involved using the –dV values for NiCd cells when charging NiMh cells resulted in around a 20% loss of cycle life. This was a direct result of overcharging and heat.

The charger manufacturers realized that –dV termination was easy to implement and fairly reliable, so they approached the chip manufacturers about modifying their existing chips to accommodate NiMh charging. The result was increasing the “dead time” where the charger would not accept a fluctuation in voltage as a end of charge termination signal, and reducing the value of the –dV from 10 – 15 mV to 3 – 5 mV. They also come up with charging in pairs, thinking that the combined voltage drop from two cells would be easier to detect.

With a few exceptions, most of the quick or smart NiMh chargers available today utilize –dV charge termination. If you are checking out a charger, you should probably assume that it utilizes –dV termination, unless it states something different.

When picking out a charger for NiMh cells, the first thing you need to know is how does it determine charge termination. Once you know that, you can then check to see if the charging rate of the charger is suitable to produce a strong end of charge signal. In the case of chargers that utilize –dV termination, the suitable charge rate is in the range of 0.5 – 1.0C.

The next thing to look at is the trickle charge rate at the end of the charge. If this rate is too high, and you leave your cells on the charger, you will cook your cells and greatly reduce your cycle life. The optimum is to have the charger trickle for awhile, then shut off. However, some people become over concerned with the self discharge rate of NiMh cells and want a charger that keeps the cell at a full state of charge through trickle charging. In this case, you want a very low trickle charge rate. You can refer to the various battery manufacturers for their definition of what a suitable trickle charge rate is. I don’t recommend leaving cells on the charger trickle charging, but if that is what you think you need to do, I believe the newer Maha chargers trickle charge at a low enough rate that the cells may actually self discharge a little while still on trickle charge. That seems like a suitable rate to me…

So much for the introduction, now let’s take a look at charging rates.

The Schulze charger has a long term formatting setting that they label 0.1C charging. There is no time limit or charge termination when using this setting. The charger continues to pulse charge until you manually stop it. The duty cycle is 25 seconds at 400 mA followed by 75 seconds at 0 mA. I use this setting for forming cells and battery packs, and balancing battery packs.

I have noticed, from time to time, that there is a voltage drop during this slow charge. It doesn’t always show up, but with healthy cells and a balanced pack, it usually does.

Let’s take a look at one of my 4400 mAh NiMh B90 prototype packs with less than 100 charge/discharge cycles on it. This pack was charged and balanced, then partially discharged for this study. Peak voltage was reached at around 110 minutes into the charge. It took 6300 seconds (105 minutes) to develop a –dV of 2 mV per cell.

Here is the graph:







You may be curious why I listed the time to –dV drop in seconds. Checking out the specifications on the charging chips available from the various chip manufacturers, I have observed that when they are looking for a –dV value, they use a time ranging from 100 – 300 seconds. If I was using one of these chips hoping to terminate this charge, I would miss the signal because of the long time (6300 seconds) it took to develop the signal.

The result is a missed termination.

Fortunately, at the 0.1C charge rate, there is little consequence with a missed termination. However, if you increase the charge rate, you can run into problems.

A Swedish study looked at the affects of a 30% overcharge. It found that charging at 0.3C with a 30% overcharge yielded around 225 charge/discharge cycles before the cell capacity dropped to below 80% of its initial capacity. Charging at 1.0C with proper termination (actually they were using a –dV of 10 mV which I think is high. They would have obtained better results using a –dV of 2 mV, but this study was done a few years ago) yielded around 500 cycles before the capacity dropped to below 80%. The study goes on to illustrate that overcharging at 1.0C is more detrimental than overcharging at 0.3C, but the point is well made that overcharging, even at lower charge rates, is bad for the health of the cell.

OK, let’s throw some numbers out… If you have a 2000 mAh cell, a 0.3C charge rate would be 600 mA. If your charger misses the end of charge termination, it will continue to charge until the safety timer shuts off. If your safety timer is set to 3000 - 3300 mAh (BC-900) or 4000 mAh (C-9000), or 8050 mAh (Vanson BC1HU), you will end up with an overcharged cell. A 30% overcharge on a 2000 mAh cell is roughly 2600 mAh.

I have some aged AAA Moden 850 mAh cells. These cells were revived from near death due to low voltage due to improper long term storage. They are not the most vibrant cells, but they do a good job at lower current draws. I use them in my Peak Matterhorn that I EDC on my key chain.

Here is a graph while charging at 0.25 amps (roughly 0.3C):






As you can see, there was no –dV signal. I terminated the charge because the cell started to warm up more than “normal.” If I repeatedly charged this cell at this rate on a charger that utilized –dV termination, I would end up with reduced cycle life due to overcharging.

Here is the same cell charging at 0.5 amps:






At this rate there is a strong end of charge signal, and the problem with overcharging is eliminated.

Getting back to the original questions… What is the best rate to charge NiMh cells at? It depends on the method your charger uses to terminate the charge. If your charger utilizes –dV termination, you will get a more reliable signal if you charge in the range of 0.5 – 1.0C.

Now, if your charger utilizes peak voltage termination, things change. If you look at the graphs, you can see that the voltage rises to a point, then does not rise further. If you terminate the charge when the voltage stops rising, this can be observed regardless of the charge rate. You will notice that it is present in the 0.1C charge of the 4400 mAh battery, in the 0.3C charge of the 850 mAh cell, and also in the 0.6C charge of the 850 mAh cell.

When using peak voltage termination, you now need to look beyond termination to determine the best charging rate for your cells. Slow charging produces large crystals, and large crystals produce voltage depression. Once again, ultra slow charging may not give you the best performance. Now we are in an area that is application dependent. I have often heard that you should charge at about the same rate that your application uses the cells. There may be a lot of truth in this.

It is interesting to observe the habits of the RC people. Their NiMh packs used in their cars, trucks, airplanes, and helicopters are often charged at 2 – 3C, but the battery packs in their transmitters and controllers are usually charged at 0.1C for 14 – 16 hours. While their vehicle battery packs are only prime for around 20 – 50 cycles, their transmitter packs seem to last a long time.

The questions remains, Why does Sanyo in the Eneloop site seem to contradict the recommendations in their main site? Perhaps the Eneloop chargers have changed from –dV termination to peak voltage termination. I think some testing may be in order…

Tom


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## Luxbright (Oct 28, 2007)

Hi Tom,

As always, great contribution to the CPFers community. :thumbsup:


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## koala (Oct 28, 2007)

Your not alone. I usually set my ICE charger to 0.1C charge rate for charging empty cells. Setting the -deltaV charge termination to 20-25mV/cell makes the charger 'blind' and immune to the -deltaV termination. This is a good setting to defeat unstable power supply and early termination.

The charger will terminate as soon as it reaches the user preset maximum capacity. A good way of turning an analyzer in to a slow charger. 0.1C is actually a good charging rate for balancing NiMH battery packs.

Regarding Peak Voltage Termination, is the voltage the same for all cells? If not how does it work? Charge will terminate once the cell reaches certain high voltage for certain period of time? There is another type of termination called 0v delta peak termination, where the detection system works by detecting the peak voltage.

Can you please post the sanyo link? Interesting stuff...


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## SilverFox (Oct 28, 2007)

Hello Vince,

I believe that if you set the -dV value to 0 mV you have peak voltage detection.

Here is the Sanyo Eneloop link. There seems to be some bad information here. I believe my 2 cell and my 4 cell chargers are both independent channel chargers that will charge single cells. The question comes from question 12. It states that you shouldn't use quick charging, but should us a charger that charges in 2 hours or more. I like the 2 hour part, but have problems with the more part. Also, the last time I checked, 2 hour charger is considered quick charging.

Tom


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## mdocod (Oct 28, 2007)

Tom, I am always thrilled by your dedication to exploring and learning and sharing with us about the world of rechargeable cells, I learn so much form you I feel I should be paying tuition....

On a side note, I was thinking... Assuming $2.50 per premium label NIMH AA, even if you do everything in your power to charge them incorrectly, and only manage to get 50 cycles out of them, that's still like 5 cents per cycle.... Still cheaper than alkaline!!!!


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## UnknownVT (Oct 28, 2007)

Tom/SilverFox - 
your comments please on the BatteryUniversity.com page -

Charging nickel-based batteries 

about 2/3 down the page -under
*Charging nickel-metal-hydride* -
"_Nickel-metal-hydride should be rapid charged rather than slow charged. Because of poor overcharge absorption, the trickle charge must be lower than that of nickel-cadmium and is usually around 0.05C. This explains why the original nickel-cadmium charger cannot be used nickel-metal-hydride. _

_It is difficult, if not impossible, to slow-charge a nickel-metal-hydride. At a C?rate of 0.1-0.3C, the voltage and temperature profiles fail to exhibit defined characteristics to measure the full charge state accurately and the charger must rely on a timer. Harmful overcharge can occur if a partially or fully charged battery is charged with a fixed timer. The same occurs if the battery has aged and can only hold 50 instead of 100% charge. Overcharge could occur even though the battery feels cool to the touch._"

This explains the preference of fast charge over slow charge on the basis of end of charge detection.

BUT there is also the third point under *Simple Guidelines:*
"_nickel-based batteries prefer fast-charge. Lingering slow charges cause crystalline formation (memory)."_

Other references -

Panasonic NiMH Charging Manual pdf

Energizer pdf NICKEL-METAL HYDRIDE Application Manual


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## koala (Oct 28, 2007)

hey mdocod - in case you don't know, Tom is try to make up for his Renewable Energy Thesis which is long overdue. :naughty:

I haven't seen a picture of _crystalline formation. _I am wondering if it could be inspected under a microscope. All I have seen is illustration. It would be cool if one could disassemble(with safety precautions) a NiCd and NiMH that has 'memory' then compare them. I would certainly do it if I have a microscope.

I am pretty sure battery manufacturers do this sort of testing in their lab but they would probably never release such information.


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## SilverFox (Oct 28, 2007)

Hello Vincent,

My comment on the Battery University information is that they give some good advice...  

Tom


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## SilverFox (Oct 28, 2007)

Hello Vince,

In this thread I discussed voltage depression and memory issues. I believe there are some references in it that illustrate the difference in crystal size.

Tom


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## BentHeadTX (Oct 28, 2007)

I have seen the effects of crystal formation in 12V 2.5 Ah Ni-Cd batteries. The charger/conditioner device would indicate "discard" although the packs were a year old so I kicked it "old school". 

Grabbed a 24V 100W bulb and attached it to the negative and positive output and the voltage started falling rapidly to below 10V or under 1.0V per cell. The light was bright as the voltage kept dropping to 7V then 6V and stabilized at 5.85V. Odd, the bulb was quite bright and putting out some serious heat. Then it happened, the voltage started creeping up for the next 15 minutes and peaked at 6.31V before a slow decline to eventually 0.1V. 

Here is my wild *** guess what happened. The battery was trickle charged continously and built up huge crystals causing major voltage depression. The conditioner detected very little capacity above 1.0V per cell and rejected the pack. The light bulb pulls less current naturally as the voltage falls and more current as the voltage rises. Once the crystals started breaking down in the electrolyte, this boosted the voltage from 5.85V to 6.31V as the crystals have more surface area when breaking even though the current load went up. 

Upon dropping down to 0.1V with the light bulb, I shorted the battery with a jumper wire and left it shorted over the weekend. Put the pack back on the charger/conditioner and it cycled fine with a "pass" indication the next day. The guys at work pulled out even more packs that failed and so far, I am 10 for 10 with the old school bulb and shorting discharge trick.  

Yes, I told the guys that trick only works with Ni-Cd as it is very robust. 

I have a BC-900 Version 32 and lucked out, it does not start on fire or miss terminations. It is rare I charge at 200mA as my preference is 1000mA with Powerex 2700's. My Eneloop AAA cells were discharged initially at 100mA and charged at 200mA (C/4) with no problems. Recharging is done at 500mA (C/1.6) with no problems noted. 

The only time I prefer a slow charge is for the C/10 forming charge. Have an 8 pack of AA Eneloops still the in package waiting for a Cadex analyzer to arrive at work. I want to discharge at 400mA to 1.0 or 0.9V and form at C/10 (200mA) The cells were manufactured September 2006 so I am curious what their self-discharge rate is. 

Should I charge the Eneloops after the forming cycle at C/2 1000mA or lower? It will do two cycles and finish with C/5 400mA as the discharge rate to 1.0V per cell. 

I will give a detailed report of each AA Eneloop and how it performed after sitting around for 14 months. Just wonder what the "official" CPF way of charging involves. C/5 is the standard discharge and I am assuming 1.0V as the cut-off.


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## koala (Oct 28, 2007)

Hey Tom, somehow I missed that thread. Saw the two pics of the crystalline in the pdf very cool! I remember in the early 90s, battery charger manufacturers started to produce so called "negative pulse charger". They were suppose to blast those whiskers away.

Then when I got my Triton Charger(maybe ICE), the manual mention that the negative pulse charging algorithm is only suitable for NiCd and not NiMH.

Hey BentHeadTX, lucky you to have a Cadex to play with. Are they from Battery University?


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## Mitch470 (Oct 28, 2007)

*Great Information*



SilverFox said:


> “What is a good rate to charge my NiMh cells?” and “Is this charger good?” are frequent questions that come up around here.
> 
> The questions remains, Why does Sanyo in the Eneloop site seem to contradict the recommendations in their main site? Perhaps the Eneloop chargers have changed from –dV termination to peak voltage termination. I think some testing may be in order…
> 
> Tom


 
Tom,

That was a great treatise on rechargeable NIMH batteries. I learned a lot.

However, I'm still of the opinion that a NEW DOCTRINE is going to emerge for charging LSD batteries including the Eneloops. I'll wait for your research to continue. Perhaps, optimimum charging for them will entail procedures not yet discovered. Perhaps, there will be new chargers introduced by Ansmann, LaCrosse and Maha SPECIFICALLY to be used for the new LSD batteries. GE/Sanyo Eneloop DOES have specific chargers available for their batteries. However, their chargers are not as flexible in use as the LaCrosse BC-900.

In the meantime, I am convinced the LaCrosse Version 33 BC-900 DECISIVELY beats Maha and Ansmann at this moment in time for addressing the needs of the new LSD AA and AAA batteries. Maha stipulates that their charger can never be used below .33C safely. Ansmann has fixed current applications and cannot be adjusted at all. Only LaCrosse stipulates the low charging rates implied as necessary by the Eneloop literature.

I believe that for Standard AA and AAA NIMH's the Maha C9000 is probably the best out there. For C, D and 9V NIMH's the Ansmann is probably the best out there.


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## redfish (Oct 28, 2007)

*Re: Great Information*



Mitch470 said:


> Tom,
> 
> In the meantime, I am convinced the LaCrosse Version 33 BC-900 DECISIVELY beats Maha and Ansmann at this moment in time for addressing the needs of the new LSD AA and AAA batteries. Maha stipulates that their charger can never be used below .33C safely. Ansmann has fixed current applications and cannot be adjusted at all. Only LaCrosse stipulates the low charging rates implied as necessary by the Eneloop literature.
> .




Oh man, this guy has a major case of choice-bias. When will he stop?


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## UnknownVT (Oct 28, 2007)

SilverFox said:


> The questions remains, Why does Sanyo in the Eneloop site seem to contradict the recommendations in their main site? Perhaps the Eneloop chargers have changed from –dV termination to peak voltage termination. I think some testing may be in order…


 
Even eneloop.info (the earlier European site) seems to offer a differing take on this page:

"_*Other Chargers* _
_Basically eneloop is a modern Ni-MH battery, which can be charged like any other Ni-MH battery. _
_Therefore eneloop can be charged also with other, modern chargers, which are suitable to charge Ni-MH batteries. _
_However, SANYO cannot accept any liability for the function or safety of chargers made by other manufacturers. _
_Also SANYO cannot be held responsible for any damage to eneloop batteries caused by unsuitable chargers."_

This is very much in line with the entry at Wikipedia 5.1.1 Low Self Discharge Batteries (I could not find the source reference to that information, but generally the Wikipedia is accurate because of the open exposure and correction/refereeing)
"_Besides the longer shelf life, they are otherwise similar to normal NiMH batteries of equivalent capacity, and can be charged in typical NiMH chargers._ "

Of course eneloop.info on the same page also do say -
_"*SANYO Chargers* _
_SANYO offer special chargers for the eneloop. These chargers have been developed by SANYO and have been tested for charging eneloop batteries. _
_With the charger MDR03 you can charge two eneloops of size AA in 250 minutes or two eneloops of size AAA in 170 minutes. The charger works with AC-voltages from 100V to 240V and is therefore ready to join you on your trips to other countries. "_


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## GaryF (Oct 28, 2007)

Mitch470 said:


> Only LaCrosse stipulates the low charging rates implied as necessary by the Eneloop literature.





Mitch470 said:


> So far as Termination Detection, I have my own ad hoc way of preventing a miss. I charge 4 batteries or more at one time and take the last one to terminate out of the charger when all the others have already reached a termination detection. I don't really care if it was slightly undercharged. I then check its voltage. If it is less than the others, I put it back in the charger for another hour.



Do you still charge 4 batteries at a time and terminate the charge manually? It seems like a lot of trouble, especially for someone planning to throw their batteries out in a year due to obsolescence. My Eneloop literature recommends charging at a rate that will take 2 hours or more, so I charge at 1000mA and don't worry about supervising the process. FWIW, the batteries barely get warm, and I expect them to last many years.

I guess if Sanyo ever comes out with a "NEW DOCTRINE" for recharginging Eneloops, then we will need to pay attention. But thus far, everything points to them being regular NiMH chemistry with a few design optimizations which do not require special chargers or charging routines. 

Do you have any thoughts on large crystal formation during slow charging, and what is it about Eneloops or the LaCrosse charger that you think would allow them to avoid this problem? Anything more than a hunch?


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## Mitch470 (Oct 28, 2007)

GaryF said:


> Do you have any thoughts on large crystal formation during slow charging, and what is it about Eneloops or the LaCrosse charger that you think would allow them to avoid this problem? Anything more than a hunch?


 
I am NOT an Electrical Engineer. Is anyone else here an Electrical Engineer? I am just a gadget hobbyist. I used to just buy regular batteries and THROW them away. Then I proceded to get Standard NIMH's due to their more advanced technology. I only used the Ansmann Energy 8 with them. Frankly, if someone introduces a 6000 mAh non-rechargeable Lithium, I'll go with that one and discard all the rest. I'd even pay a premium price for it. Right now I still mostly use 3000 mAh Lithiums - nonrechargeable.

Now, I have become a fan of the LaCrosse BC-900 Version 33. If I don't see new gadget batteries and chargers in 12 months, I will be very disappointed. This is all GADGETRY for me.

I know that you MH-C9000 fans are very upset that I much prefer the LaCrosse BC-900. Live with it.

I expect to be getting involved with the new Garmin Nuvi 750 GPS when it comes out this week. I hope to see even newer gadgets next month.


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## TorchBoy (Oct 28, 2007)

Mitch470 said:


> I know that you MH-C9000 fans are very upset that I much prefer the LaCrosse BC-900. Live with it.


You know, Mitch, it's not so much that (I think most MH-C9000 owners would happily admit it's a good charger) as how you are using it, while authoritatively claiming that it's the best way to use it and that it's THE best there is. Based on what? Feelings and misunderstandings? There are people here who do understand very well what NiMH cells are doing when they charge and you're going to have to come with some very good reasons to convince them that their genuine good understanding is bad misunderstanding. I suggest you listen to them and figure out why they're saying what they do.

It's cool that you like gadgets. I can appreciate that since I've got a slow but steady stream of new toys coming from DX and KD. It's like Christmas all year round. :twothumbs


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## MrAl (Oct 28, 2007)

koala said:


> Hey Tom, somehow I missed that thread. Saw the two pics of the crystalline in the pdf very cool! I remember in the early 90s, battery charger manufacturers started to produce so called "negative pulse charger". They were suppose to blast those whiskers away.
> 
> Then when I got my Triton Charger(maybe ICE), the manual mention that the negative pulse charging algorithm is only suitable for NiCd and not NiMH.
> 
> Hey BentHeadTX, lucky you to have a Cadex to play with. Are they from Battery University?




Hi Vince,

I am starting to favor the temperature rise method because that can
detect end of charge sooner than minus delta V, which i have proved
with my battery monitor chip and software.
BTW, you will have a battery analyzer too as soon as i get the check
from Tom. He said his wife was sending it and that was last weekend
but i havent seen it yet.

Also BTW, anyone else interested in a battery analyser circuit for under
20 dollars (more like 10 dollars) just PM me.


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## TorchBoy (Oct 28, 2007)

BentHeadTX said:


> ... I kicked it "old school".
> 
> Grabbed a 24V 100W bulb and attached it to the negative and positive output and the voltage started falling rapidly to below 10V or under 1.0V per cell. The light was bright as the voltage kept dropping to 7V then 6V and stabilized at 5.85V. Odd, the bulb was quite bright and putting out some serious heat. Then it happened, the voltage started creeping up for the next 15 minutes and peaked at 6.31V before a slow decline to eventually 0.1V.


I can understand it would work wonders, but doesn't it seriously reverse charge some of the cells?


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## Bones (Oct 28, 2007)

Firstly, thank you for yet another very educational treatise Silverfox.



SilverFox said:


> The questions remains, Why does Sanyo in the Eneloop site seem to contradict the recommendations in their main site? Perhaps the Eneloop chargers have changed from –dV termination to peak voltage termination. I think some testing may be in order…





MrAl said:


> I am starting to favor the temperature rise method because that can detect end of charge sooner than minus delta V, which i have proved with my battery monitor chip and software.



The manual for the model MQN05 contains the following statement under the 'How to Charge' heading which appears to bear some relevance here:



> Do not plug-in upside down. If plugged in upside down, it will finish charging before it is fully charged.


Given my very limited knowledge on this subject, I have only been able to surmise that it pertains to temperature, ie: that there may be sensors in a location where they would reach a given temperature prematurely when the charger is upside down.

On a side note, the statement infers that the premature termination will happen in every instance, indicating that there is also a fairly narrow tolerance at play, so the sliding cover may serve as more than just a decorative touch if the statement is indeed temperature related.


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## TorchBoy (Oct 28, 2007)

Bones said:


> ... the sliding cover may serve as more than just a decorative touch if the statement is indeed temperature related.


That's interesting. The manual of a NiMH charger I have says make sure the cover is closed before charging. Would that be to help sense heat too? All other charger manuals I've seen say leave the cover open - in case of venting and to help keep things cool is my guess.


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## BentHeadTX (Oct 28, 2007)

TorchBoy said:


> I can understand it would work wonders, but doesn't it seriously reverse charge some of the cells?



Yes, it will do that but not for a very long time... all cells will eventually go to 0.00V under load and stay shorted for a day or two. Back in the 80's, we used to drive 120 cell 144V Ni-Cd packs and attach them to large banks of light bulbs to run them down overnight. After that, we would place shorting bars across each cell and let them sit like that for a day. The packs would go through this every 6 months and would last 5 to 8 years before replacement. 

That is why I love Ni-Cd for harsh use... they keep going and can be revived. Could be the reason so many defibrillators still use 12V 2.5 Ah Ni-Cd cells. 

One of the cells gave me hell overseas, it would constantly trip the Cadex with various errors. I then did the light bulb trick and left it dead shorted over the weekend. It still failed but later in the cycle. Performed the dead short trick again and it almost passed. Got a wild hair and did very bad things to that battery!  

I noticed it would not charge all the way up and give a low voltage error. I charged it at 3.6 amps which is C3 considering it has 1.2 Ah cells. The thing hit 1.37V and stalled and tripped the heat sensor at 45C. I let it cool down for a few hours and hammered it at C4 (4.8 amps) and it charged to 1.56V and shut down. The temp was at 43C so I juuuuust made it. Let it cool for several hours and did a 2.4 amp discharge to 0.4V per cell followed by two cycles of C1 1.2A charge/discharge. The battery finally spewed out a result of 93% and was returned to service. 

The downside of that was the time it took to get it going, almost two weeks! The unit was being replaced in three months and it takes at least a month for a replacement battery to make it to that side of the world. 

If I was going to be trapped on a desert island for 10 years and had a choice of batteries to get me through... make mine Ni-Cd... they can be revived. When the Cadex makes it to work I have a special battery, a 9.6V Makita drill battery manufactured in April 1992... it could be time for "ride the lightning" but that is another story. 

Another chemistry that I find can handle a beating is Lithium Iron Nano-Phosphate from A123 Systems. Have four of those batteries and they work very well and no problems after a year of using four of them. Time will tell their shelf-life though... I am thinking positive on LiFePO4 in general so things are looking up.

BTW, don't beat the hell out of NiMH or Li-ion, they will fail on you.


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## Mitch470 (Oct 28, 2007)

BentHeadTX said:


> If I was going to be trapped on a *desert island* for 10 years and had a choice of batteries to get me through... make mine Ni-Cd... they can be revived. When the Cadex makes it to work I have a special battery, a 9.6V Makita drill battery manufactured in April 1992... it could be time for "ride the lightning" but that is another story.


 
Its doubtful you will have electricity on a desert island. Non-rechargeable Lithium batteries in a large supply would be best. Chargers would be simply JUNK there unless you get a solar charger.


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## Mitch470 (Oct 28, 2007)

*Garmin Nuvi 750 GPS*



TorchBoy said:


> It's cool that you like gadgets. I can appreciate that since I've got a slow but steady stream of new toys coming from DX and KD. It's like Christmas all year round. :twothumbs


 
Get that Garmin Nuvi 750 GPS coming on November 1, 2007. Its the best new toy out this week. IMHO it beats both the LaCrosse BC-900 AND the Maha MH-C9000 for pure enjoyment.

I tend to be fickle about my toys.


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## Grog (Oct 28, 2007)

Mitch470 said:


> Its doubtful you will have electricity on a desert island. Non-rechargeable Lithium batteries in a large supply would be best. Chargers would be simply JUNK there unless you get a solar charger.




Solar cells are easily packable for use with a low-amp-draw charger such as those from maha...........


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## VidPro (Oct 28, 2007)

SilverFox said:


> “
> 
> 
> 
> ...


 
some of this slow junk that could never happen. This continual rise into oblivion, because they have a peak total voltage available for each cell unit.
that means when they reach the say 1.53V the charge tapers as the voltage differential is lower, the current flow slows down.

so there is no termination on some chargers but it never gets completly out of control because they dont have 2V on each channel, so it cant even do that.
example of that are them dumb series timed things with about 3.2-3.5v for 2 cells max.


when you have a 2volt channel if your computerised stuff goes braindead, there is nothing to prevent what occured in this graph.
but was it really so high? read the actual battery voltage, its the LOW part of the line, not when the chargers pulse is ON, and it does 0V a few times.

so although the rate never goes over the overcharge rate, the voltage is going higher here, far beyond what the voltage is in lots of the cheap chargers.
besides the rate on computerised stuff is an averaged PWM, not a low current rate, with the averaged PWM you have (again) a completly different charge alogrythm, for better or for worse.

for better, it is not charging at 250ma , its charging at 1000ma, so therefore its not making different crystals than 1000ma, for better , its IS charging at 1000ma, not 250, but pausing between which keeps the cell cool, and keeps it from reaching an overcharge state.
for worse, keeping the cells cool, and having such a low rate, keeps it from Vdrop, but its not really at a low rate, each charge pulse is at a high rate, course that could be better or worse, because this cell still didnt collapse, it didnt vdrop, so it still didnt reach gassing up and all.
(assuming this is a computerised charger thing your using)

so basically different charge alogrythms, which really cant be compared DIRECTALLY to similar charge alogrythms on devices that dont use PWM, or high voltage maximums.
so you cant use a PWM charger to determine the negative effects of a Dumb slow charger.

stuff like these new wizz bang computerised analising chargers DO have the 2V max per cell capacity, DO use PWM ,and they CAN incur this kind of wrath.

this cell probably has lower resistance, and it is a AAA, which have cruddy resistance. but it does show that after TIME, when something even like an Enloop itself gets higher in resistance or sits on a shelf or in a light for ages, it will have properties similar to this. but a new one working great, will be of low resistance and would not act that way.
besides the voltage on the cell itself isnt to 1.6v yet even, what its at 1.58 or something? and may not ever reach that, a AAA with low resistance could have terminated higher than that with a higher current, so was it toasting it, or about to heat up and go into an overcharge state?

ya still didnt show that it Ruined the cell, although anything ruins AAA cells  i can slow charge a AA enloop for a month, did it, and it didnt give a crud. but my charger doesnt have 2Volt channels. but my AAA enloops are becomming offset from eachother (in capacity), and i treated them all nice :-( used all that proper termination junk and 2 of them are at about 750 and 2 are at 800, and i am guessing it cause of a minor reverse charge.

then "here is the same cell at .5amps"
Is it the same cell? it IS if it was done at the .5amps first, but if it was just "Formed"  and cycled on the last slow charge you did, then it didnt have the same resistance anymore  
so the only "proof" would be if the one test was done after the other, or that the first test was done again. because this time that same cell might terminate. for a AAA cell to not terminate at 250ma???? its either a crap cell (throw it out or your charger sucks  the charger must have been expecting that the cell suffer miserably first  before it determines that it is beaten down enough. whatasa matter cant it detect the big fat 0 there.

suuuureee you got a big fat drop there when your cycling the cell around on that day or week, but ya dont get such pretty huge drops on cells that are all unused and un cared for. 

my charger would terminate most AAA cells with 250ma, at a high voltage, but well within the "capacity" of the cell. meaning the readout or the time is never soooo different than the tested discharge capacity.


(ok i edited the heck out of that, just soes you know)


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## VidPro (Oct 29, 2007)

koala said:


> Then when I got my Triton Charger(maybe ICE), the manual mention that the negative pulse charging algorithm is only suitable for NiCd and not NiMH.



them negative pulse charging did accomplish one thing. or at least on the idea behind it.
the idea was to load the battery after a charge pulse, i donno how "negative" it was, but basically it would charge and put a load on Draining some of that charge, then charge again, drain again, on and on.
and this type of alogrythm is very similar to Cycling a battery if you think about it.
at each charge pulse there is a Use pulse, while countering eachother, the ammount of USE or load, is insuring that section or part of the battery is getting fully cycled.
for a battery that was uncycled and low resistance and all that other stuff, it should help it out by 1/4 or so which was then cycled. because 1/4 is the most they would re-drain what they just charged.

plus it does pulse charging.
it would be usefull for some situations, and totally useless in others.


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## jeffosborne (Oct 29, 2007)

Hey Mitch470 - I am an eletronic design engineer! Mostly digital stuff, never had to design a battery charger I must say.Thanks a ton Silverfox for your fine writeup! To be honest, I thought the better chargers used a short DISCHARGE periodically to 'burp' the chemistry, especialy for the rapid chargers. Anyway this post and set of informed replys is why I keep coming back. Good stuff!Jeff O.


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## LuxLuthor (Oct 29, 2007)

Tom...first of all :bow::bow::bow:

So great to take the time to read this thread. Great additional points raised from others also.
On a practical basis, it seems the 0.1C x 16 hrs with a timed termination (I usually just set an alarm)j would not be long enough to lead to large crystal formation if you made sure they were discharged to 0.9V/cell first. Is that correct?
_*(I just want to make sure that no one comes away from this discussion with a downside to 0.1C forming charge, and how important it is.)*_​
Ignoring the Eneloop link controvery, *it appears that the best general charging rate for most users is 0.5C in terms of prompting adequate -dV signal for proper termination, and thereby avoiding (smaller) crystal formation*. Is that your NiMH recommendation for general uses?

This again underscores for me the importance of *attending to my charges*. Watching the time, increasing mA and voltage, looking for a plateau & possible failed termination, feeling the cell temps, etc. For those readers who are not as able to absorb the technical aspects of this discussion, I think it is always useful to emphasize/reinforce the optimal general guidelines.
Many thanks again! :thumbsup:


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## wptski (Oct 29, 2007)

Tom:

Not near my manuals but I don't think that a ICE or Triton allow a zero volt setting for termination.


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## koala (Oct 29, 2007)

Hi Bill, :wave:

Duratrax IntelliPeak ICE charger(DTZ4170/DTXP4170) manual version 1.0, pg.12 #4.
http://manuals.hobbico.com/dtx/dtxp4170-manual.pdf
PDF Online version 1MB

ElectriFly Triton Charger has it (Because both IntelliPeak ICE and Triton are made by SJPROPO from Korea, note: your manual is printed in Korea 
http://web.archive.org/web/20060813115426/www.electrifly.com/charger.html - webarchive because old Triton is removed from the official website
* "zero deltaV" peak detection for NiCd and NiMH (0-V) *

ElectriFly Triton2 Charger has it too right in the specifications
http://www.electrifly.com/chargers/gpmm3153.html
* “zero deltaV” peak detection NiCd/MH
*
Question.
Which other charger has zero deltaV peak detection?


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## SilverFox (Oct 29, 2007)

Hello VidPro,

Let me try and answer some of your earlier comments...

The missed termination causes the charger to keep charging even when the cell is full. I don't know that limiting the voltage would be a protection against overcharging. Voltage control was tried early on, and resulted in thermal runaway. When the voltage of the cell drops, the charger keeps charging and eventually things got out of hand.

The charger used for this demonstration was my Schulze. When charging at 250 mA, a typical cycle is 92 seconds at 250 mA and 8 seconds a 0 mA. I believe you were thinking of the C-9000 when you commented on the PWM charge rate of 1000 mA. Not the case here.

I agree, these cells are marginal. I picked them up to compare the termination algorithms of the C-9000 and the BC-900, and the improved algorithm in the improved C-9000.

They are very repeatable. The BC-900 misses the termination about 85% of the time. The improved C-9000 usually terminates, but I have also observed missed terminations on it as well. The Schulze will miss the termination every time at this low charge rate. The Schulze, and other hobby chargers, are most reliable at 1C charge rates with NiMh chemistry. Keep in mind that I disabled the safety back up with the Schulze. I normally set the maximum charge capacity to guard against missed terminations, but for the purpose of this test, it was set at 2500 mAh instead of a more respectable 1200 mAh.

Of course, even the safety timer doesn't help if the cell isn't completely discharged, as was the case here.

Mark at www.e-lectronics.net had a box of these cells sitting around. We went through them and picked the ones that were at 0 volts. Mark donated them to the battery testing cause... Thanks again Mark.  

You can tell that these cells have "issues" by looking that the charging voltage of the cell. For comparison, the Eneloop AAA cells usually have a maximum charge voltage of around 1.5 volts.

Tom


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## SilverFox (Oct 29, 2007)

Hello LuxLuthor,

It seems charging is a bit of a balancing act...

Battery electrodes are kind of like a sponge material. In order to evenly distribute the electrolyte and the charge, a slow charge is needed, but slow charging produces large crystals. When you charge at higher rates, the deeper "holes" may not be evenly charged. The balance comes from starting with slow charging, then moving on to quick charging. Every 20 - 50 cycles, a slow charge brings everything back to normal.

If you use cells in applications that only draw 0.2C from them, only using the "standard" charge will give you very good performance. If your application draws more than 0.2C, and you only use the "standard" charge, you will suffer from voltage depression and reduced cycle life because of large crystal growth.

So, I guess there can be a down side to the "standard" charge, but if used properly, its benefits far outweigh its down sides.

The battery manufacturers recommend charging in the 0.5 - 1.0C range. The hobby charger manufacturers (Schulze) recommend charging at 1.0C. I tend to charge closer to 1.0C, depending on the charger.

With my AA Eneloop cells, I use 1500 mA with 2 cells in the BC-900, or 1000 mA with 4 cells. I use 1500 mA with the C-9000 because at 2000 mA the charger tends to heat up. I use 2000 mA with my Schulze.

I almost always attend to my charging. I have a talking timer (search eBay for talking timer) that I set every time I charge. I happen to check my used cells with the ZTS tester and set my timer for the amount of time to put 100% back into the cells based on the ZTS results. I start the charge first, then set the timer, and usually the timer goes off just as the cells finish charging. If the cell doesn't properly terminate, I pull it and run tests on it.

After all of this, I run outside and play with (oops I meant to say use...) my flashlights...

Tom


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## Mitch470 (Oct 29, 2007)

*BC-900 V.33 NEVER Missed Termination*



SilverFox said:


> They are very repeatable. The BC-900 misses the termination about 85% of the time.


 
Tom,

I have charged 16 AA Eneloops and 8 AAA Eneloops with not a single missed termination with the LaCrosse BC-900 Version 33. I repeated one AA to boost its capacity and ran the 8 AA's a second time to boost their capacity. I notice they all terminate shortly after hitting 1.52V.

At the currents I use (200 mA for AAA and 500 mA for AA) they should all terminate in 4 hours from the empty capacity point. So far all terminated in about 3 hours and 45 minutes - well within the expected time.

Thus, I have 33 battery runs and not a single battery missed its termination point. My experience departs widely from yours with the BC-900.

I always watch the last battery to finish for 30 minutes to see if it terminates properly and would yank it if required. It never happened.

The only reason I can think of to cause this wide disparity in test results is either I am a LaCrosse EMPLOYEE or you are a Maha Employee. I know I am not a LaCrosse employee. I can't speak for you, however.

The other reason for all these disparities in experience is the tendency of all consumers to favor whatever brand they happened to purchase unless they had a very bad experience. Hey, some of us are Yankee fans and some are Red Sox fans. Its hard to get folks on one side to cross to the other side.

I only purchased the LaCrosse BC-900. Maybe, if I had purchased the MH-C9000, I would be favoring them now instead.

Also, I've been purchasing all kinds of LaCrosse instruments for years. I am very satisfied with their products. At the moment I have a digital LaCrosse window thermometer running and its GREAT.


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## StandardBattery (Oct 29, 2007)

This is a very interesting thread, always interested in the various issues around using rechargable cells.

Coincidently I am just unpacking a new BC700, that I intend to use with eneloops (maybe others). I got the BC700 because I really don't need the higher charge rates, in terms of time to recharge vs. proported shorter life.

The BC-700 defaults to 200ma Charge Rate (but it can be changed), and on the back of the package it states: "All charge modes automatically default to 200ma charge (the optimal setting for prolonged battery life)".

I plan to use 500ma Charge rate, but I can see myself forgetting on occasion to change the default.


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## SilverFox (Oct 29, 2007)

Hello Mitch,

I guess you missed the part where I stated that the cells I was using for this were aged cells... When you get 300 charge/discharge cycles on your Eneloop cells, come back and let us know how well they are doing at your selected charge rates. 

If you look at the information I have provided, you will find that I did not state that you could not get an end of charge termination signal at low charge rates, it’s just that it is not reliable over the life of a NiMh cell. To get a reliable end of charge termination signal over the life of the cell, you should be charging in the range of 0.5 – 1.0C.

Nickel based chemistry is fairly robust. You can get away with abusing it and still usually get over 100 cycles from a cell. Most people will find this more than adequate and will move on to newer cells when their old cells under perform. However, there are some who are heavy users. Heavy users could wear out cells through abuse before new technology becomes available. Having to replace cells because of abuse every month gets expensive and tiresome. Been there, done that… In those cases, I have switched everyone to primary cells and not worried about recharging.

Tom


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## Mitch470 (Oct 29, 2007)

*I agree on this*



SilverFox said:


> Nickel based chemistry is fairly robust. You can get away with abusing it and still usually get over 100 cycles from a cell. Most people will find this more than adequate
> Tom


 
Tom, 

I agree on this statement. I doubt if I will even get 15 cycles in the next 12 months and will probably replace them with something else then.

In the last year I had 2100 mAh cells, then 2500 mAh cells and finally 2700 aHh cells all from Maha which have now ALL been given away.

I'm now using these 2000 mAh AA Eneloops and 800 mAh AAA cells.

Thus, I will probably never be able to see how all this plays out with old cells. I will never own old cells.

As a side note, I finally purchased my Garmin 750 GPS from Amazon for $ 600 and just 2 hours later noticed that the same product was available on eBay for $ 500. Things always keep changing.

I notice that 2100 mAh LSD NIMH's are widely available now. I just got those 2000 mAh LSD Eneloops 2 weeks ago. They are ALREADY OBSOLETE.

I notice that prices for both the BC-900 and MH-C9000 are dropping now at retail outlets. That usually means a new generation of chargers is just around the corner.

As that old song goes: "the times they are a'changin'."

Having the latest and the greatest does cost money.


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## SilverFox (Oct 29, 2007)

*Re: I agree on this*

Hello Mitch,

While the other LSD cells may be labeled 2100 mAh, they seem to actually test out to about the same as the Eneloop cells...

What type of cells does your new Garmin run on?

Tom


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## Mitch470 (Oct 29, 2007)

*Re: I agree on this*



SilverFox said:


> Hello Mitch,
> 
> While the other LSD cells may be labeled 2100 mAh, they seem to actually test out to about the same as the Eneloop cells...
> 
> ...


 
Tom,

It runs on a Lithium Ion cell capable of 5 hours of discharge. By the way, I was able to cancel on Amazon 4 hours after placing the order and purchased the item on eBay to save myself $ 100. One must think fast.


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## StandardBattery (Oct 29, 2007)

I'm not sure if people here would be interested in this new charger.

eStation BC6 - http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=2005

e-Station BC-6 AC/DC Balancing Charger for NiMH/NiCD/Li-PO/Li-Fe/SLA

The nice thing is it has USB port for charge monitoring.

Apparantly it's the latest and greatest, maybe someone can comment. 

Definetly not a typical home charger, but seems like more than just for RC stuff.


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## BentHeadTX (Oct 29, 2007)

StandardBattery said:


> I'm not sure if people here would be interested in this new charger.
> 
> eStation BC6 - http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=2005
> 
> ...



Thanks for the tip!

Some ponderings from an old school old fool and chargers. Back in 2003 I bought a AccuManager 20 to recharge AAA/AA/D/9V cells and it works very well. I still use it. Total number of missed terminations are zero, zip nada! 

HOWEVER! I NEVER use NiMH cells that are older than 3 years! NEVER! 

I bought a BC900 Version 32 and it has NEVER missed a termination EVER! 200, 500, 1000, 1500 or 1800mA it has never failed ever. Maybe I got a good one. My new (at the time) 2100, 2300 and 2500mAH cells were run at 200mA and they always terminated. Even my Eneloop AAA cells were run at 100mA discharge and 200mA charge in test mode and terminated normally. 

Sure, I've read about the horrors of Version 32 and it sits on a steel plate in case it ever acts up but it does not. As Tom mentions, it probably has to do with old cells which I don't use. My oldest are Wal-Mart "Digital" 2000mAH cells from 2005 and it is fed a steady diet of Powerex 2700mAH cells and now, Eneloops. The cheapo Digitals (my wife bought them) they keep plugging along looooooong after my Sony, Energizer, Powerex 2500's hit the recycle bin. 

Normally, I use the 1000mA charge rate on my Powerex 2700 cells. The other rates are pretty much ignored except for 500mA with the Eneloop AAA cells. Never had a problem with the LaCrosse or Accumanager 20 chargers with termination.

Then again, I am ANAL about my cells! Once they get to 80 to 85% or 3 years, off to the recycling bin they go. Life is too short to have marginal cells crap out or smoke your charger. Yep, I have $140 worth of chargers and don't want a $2.50 battery tearing them up. Protect your chargers, use the discharge function, take care of your cells and junk them at 3 years. Next year the Digital 2000's and Sanyo 1700's hit the recycle bin to be replaced with Eneloops. 

Oh yeah, the Cadex at work will be on duty in a few weeks so I can run conditioning etc and rock on. My hope is the Maha C-9000 will come out with a revision that allows it to be more programmable to select deep discharge rates (Cadex allows 0.4V with very low mA discharge that is tapered lower as the voltage drops) Oh yeah, the Cadex won't miss a termination even with a 100mA charge rate on a 2700mA cell (I tried) 

Condoms don't get marginal until they get old, same with batteries. One will knock up and the other will knock out... NiMH is only good for 3 years for consumer cells... 

(flame suit on)


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## SilverFox (Oct 29, 2007)

Hello BentHeadTX,

It is interesting that you bring up the 3 year service life. I have read that from various sources. I am not sure if it holds true or not.

On the other hand, if you are expecting to get 1000 cycles from your cells, that works out to close to a charge/discharge cycle a day for 3 years... 

Tom


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## jeffb (Oct 29, 2007)

Purchased a LaCrosse BC-900, when they were first released, charged AA and AAA cells (new) and never missed a termination, at 200ma, as was under the impression that lowest was "best". Due to reading of problems with the LaCrosse, purchased the Maha C-9000, used with no problems and upgraded to the latest version, courtesy of Maha. (Now charge at higher rates, usually as recommended by Silverfox!). Thanks Tom for all your testing and input, I have learned a great lot!!

Usually use Eneloops, now and the Maha works fine.

Also purchased a Triton several years ago and charge Li-ons with the Triton.

Have never had issues with the Triton either.........I am not probably considered a "heavy" user.

I guess I like toys, too . (Yes, have a Gramin Nuvi 650 and waaay too many custom flashlights........but we are talking chargers and batteries!)

jeffb


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## VidPro (Oct 29, 2007)

(in referance to the whole thread)
like he said, its not the charger so much, its the cell, a cell of high resistance is "loose" its "not as well connected to the charger" so the voltage can go up more before it starts gassing up.

any cell that is new, has been being used regularly, has been cycled, still has good capacity and low resistance, Snaps hard at the overcharge state, and the Vdrop moves down fast.

cells that are parked for a long time, discharged poorly, weak , dont get used, will not snap down and the computers are set to detect what might be concidered a harsh drop, compared to the computer realising that the temps or the pressure , or the voltage has just balanced out. 
the Vdrop is the most reliable method of destroying the cell  err i mean of detecting end of charge, because the other methods can stop charge early.

NO enloops this week should be acting all low resistance, except when you first buy it, which is porbably why some would say to "form"it
forming is a charge that requires no termination, but Still cycles the cell .

i think more people have a fit when thier cell is 1/2 full, than when the charger takes it to an overcharge state.
imagine the Forums saying some charger only charged to 75% , nobody would have that charger 

pluss add in that the chargers are more like AA chargers that happen to charge AAAs also  and an AAA can cause the worst problems of anything.


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## VidPro (Oct 29, 2007)

SilverFox said:


> They are very repeatable. The BC-900 misses the termination about 85% of the time.
> 
> Tom


 
so it misses termination on the AAAs? 
does your 900 miss termination on AA cells that are charged at 500ma (averaged) ?

and, on EITHER the AAs or AAAs when the termination is missed , does the Capacity shown in the readout go WAY over the cells known capacity? or did you get disgusted with it toasting the cells and pull them when they heated up?

I am hoping Mr ALs new toy is something that is very usable and reasonably priced.


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## turbodog (Oct 30, 2007)

BentHeadTX said:


> ... The light bulb pulls less current naturally as the voltage falls and more current as the voltage rises. ...




First, I have only skimmed the thread so this may have ben said already.

But.... the light bulb thing isn't right. A dc bulb has an inverse voltage/current relationship. Less amps at higher volts.

I guess this assumes a power source capable of delivering whatever amps the bulbs wants though..... which is not always the case when dumping cells.


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## SilverFox (Oct 30, 2007)

Hello VidPro,

As I said, these AAA cells are marginal. Marginal AA cells behave in a similar fashion. 

The marginal AA and AAA cells time out after about 3000 mAh has been put into them when charged on the BC-900... The AA cells will terminate properly on the C-9000, but the AAA cells will usually terminate properly, but sometimes they will charge to more capacity than they should.

Tom


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## VidPro (Oct 30, 2007)

SilverFox said:


> Hello VidPro,
> 
> As I said, these AAA cells are marginal. Marginal AA cells behave in a similar fashion.
> 
> ...


 
ahhh i see.
i charge AAAs on the lacross900 at 500ma, and run the AAs on the 900 at 500ma or 700ma, 700ma if i dont trust them or need more speed.

basically i just stuff everything on at 500ma because its the 50-50 pulse, i often run a "test" cycle when things go on the 900, so often i wouldnt even know what the charge only capacity reached was.
one good reason to get an 9000, where you can scroll back through previous results?

with the test cycle i know one thing, it will discharge in a machine that discharges them, and it has 98% of the capacity.
all of my 2300s and 2500s and the enlooops AAs all have 98-100+ the original capacity still. but the energysers have the self discharge, some so bad i tossed them.

only time will tell, but so far, every enloop AA tests out as if nothing has damaged it yet, which proves nothing when the energysers still have (about) 2.54A reading on them TOO.

but AAAs drive me up the wall, and heck they were charged at the 1/2c i really thought the AAA enloops would solve my AAA problems. on the TOYS they basically read about the same resting termination voltage, but test says they are going by by, just like the others.

only One set of 4 AAAs (energysers) have 100% of thier original capacity AND full capacity balance, and they have only 3 cycles on them, Much Time but few cycles, woopie.

the rest of the non enloop AAAs that have been used extensivly are all over the board, and basically because of the reverse charge now, might just as well be tossed out. I can match a few similar capacity , but they suck. the enloops AAAs act like they are going to head that same route, far from it now, but headed that way.


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## TorchBoy (Oct 30, 2007)

turbodog said:


> But.... the light bulb thing isn't right. A dc bulb has an inverse voltage/current relationship. Less amps at higher volts.


Um, noooo...

V = IR (Ohm's law) still holds. As a bulb filament heats up its resistance increases slightly. But the current still has to increase to keep the law happy, so to speak, but it's not quite as much increase as V increases.


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## VidPro (Oct 30, 2007)

TorchBoy said:


> Um, noooo...
> 
> V = IR (Ohm's law) still holds. As a bulb filament heats up its resistance increases slightly. But the current still has to increase to keep the law happy, so to speak, but it's not quite as much increase as V increases.


 
i find that to be true also, i see on the forum they say the dim glowing filiment wire is lower resistance, so therfore there is MORE current flowing through it.
from my testing , which is very minimal, the glowing filiment certanlly sucks up battery for no usefull light, but the less voltage across it, the less current flows through it, be it bright , or dim or barely warmed up, the brighter it is the more current is flowing.

so a dimed or glowing incadescent still uses lots of power, but always LESS current flow then when the voltage (battery) was higher, and its bright.
is that right?
or are there instances when a White glowing ready to drip on the floor hunk of tungstun has less current flow through it, when the voltage is higher.

and isnt there an instance for an instant (or 2) where the wire is cold and the first hit of well charged batteries the current it high, and that is why they pop protection on startup, and need soft start and all?

hmm can i even say that correctally


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## NiOOH (Oct 30, 2007)

An interesting discussion here. In my experience with the BC900 (v32, 33) C9000 and may other consumer chargers (Vanson, BC1Hu, LP4KN, GP, CCrane,Sanyo and Chinese cheapies) I have never encountered missed terminations. Depending on the charger and cells the currents have been as low as c/5.


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## SilverFox (Oct 30, 2007)

Hello NiOOH,

Missed terminations seem to be rare with good cells, but can occur more often when the cells have aged. If you go through the C-9000 topics, you will even find 1 or 2 cases where brand new Eneloop cells suffered missed termination. As the chemistry breaks down through use, or becomes oxidized through over discharge, it changes and no longer behaves normally. Usually, I believe this change in chemistry results in the cell no longer holding a charge, but it seems that it can also happen with cells that appear to be "normal."

Perhaps we need to go over the signs of a missed termination. At low current charging rates, the major sign is that it takes longer to charge your cells. The cells will warm up a bit more, but in the testing that I have done, it only amounts to a 5 - 10 F increase. This is barely noticeable, unless you are looking for it.

Most chargers do not tell you how much they have put into the cells, so you have no idea if they terminated properly, or timed out. A lot of people put their cells in a charger and come back in a few days, or a week, or longer, when they need charged cells. Without some sort of analyzer or testing, they have no idea if their cells are performing properly. They use them until they think the performance has dropped off, then put them in the drawer hoping that new technology may come along to revive them.

When Maha was doing research on the C-9000, they noticed that there were a few times when the charge would not terminate. This led them to take another look at their charging algorithm. Looking at the response from these cells, they found that at some charge rates, there was no voltage drop, or temperature increase at the end of the charge. As I understand it, they tested thousands of batteries from a variety of manufacturers, including aged cells. I think they were surprised when the CPF people came up with more missed terminations than they had uncovered in their testing. It appears that in addition to having some of the most advanced flashlights, we also have a good selection of "crap" cells...

In reviewing information on the various hobby chargers, I discovered that years ago Schulze ran into similar issues. People were reporting missed terminations with the early Schulze chargers. His response was to tell people that while they had a variety of charging current choices, they should either charge at 0.1C, or at 1.0C. Use 0.1C for forming and balancing, and 1.0C for charging. 

I think missed terminations are more frequent than we realize, its just that we aren't aware of them.

Tom


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## turbodog (Oct 30, 2007)

VidPro said:


> ... correctally



colo rectally?

 

Well ok, let me back up then. I'll go with more amps at higher voltage because the voltage delta outweights the resistance delta.

I guess my point I was really trying to make was the increase in resistance with increase in temp.

But to speculate a little....

A 50w 12v bulb, ran from a 2v supply (think of a single celled lead acid battery, the size that is used in an off-the-grid setup), would have to pull incredible amps.

Anyway..... wrong thread. MAybe I can come back to this later with some actual measured data.


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## TorchBoy (Oct 30, 2007)

SilverFox said:


> As I understand it, they tested thousands of batteries from a variety of manufacturers, including aged cells. I think they were surprised when the CPF people came up with more missed terminations than they had uncovered in their testing. It appears that in addition to having some of the most advanced flashlights, we also have a good selection of "crap" cells...


Not any more - mine all got well toasted by my early MH-C9000s. 

But I have to agree. I think there are more crap cells floating around and in regular use than most of us would guess. The big question is whether CPFer's total collection of cells is any better than the general public's.


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## LuxLuthor (Oct 30, 2007)

StandardBattery said:


> I'm not sure if people here would be interested in this new charger.
> 
> eStation BC6 - http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=2005
> 
> ...



This model has an advantage of a built in power supply, and disadvantage of only 50W charging power. It makes me lean towards the BC-8 which uses an external power supply (which I already have) and outputs 150W for charging.

As I look around at chargers that give a graphical display of charging, including per cell....this is one of the few that does USB to PC graphical displays of your charging, and with per cell popup voltages. 

The FMA that Petrev uses gives a complete linear display graph of individual charging voltage, but only does Lipo chemistries.


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## BentHeadTX (Oct 30, 2007)

turbodog said:


> But.... the light bulb thing isn't right. A dc bulb has an inverse voltage/current relationship. Less amps at higher volts.



Thanks for the tip 
I need to send my Fluke true RMS multimeters, o-scopes and power supplies back for a refund. They have been defective for years. 

If the voltage drops and the amps increase... does that not make a light bulb a regulator? That would be great when I plug a 120V bulb into a 220V outlet.  Maybe I should use different bulbs.


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## n3eg (Oct 30, 2007)

I think any cell that shows almost 1.6 volts when charging should be tossed. I laugh every time I put a pack on the Cadex and it shows high voltage...I know it will give me the "fail" buzzer really soon.

This thread reminds me of something I used to do to test N size nicads in pagers. I would crank the current limit on the power supply up to 2.5 amps and put the clip leads on for a second. If I saw any more than 2.5 volts, it had high impedance and was tossed. I called this the "impedometer" test. I've found that batteries with high impedance are high risk for missed or late termination, and even get hot in the Cadex.


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## TorchBoy (Oct 30, 2007)

n3eg said:


> I would crank the current limit on the power supply up to 2.5 amps and put the clip leads on for a second. If I saw any more than 2.5 volts, it had high impedance and was tossed.


I think that's basically what the MH-C9000 does, but their cut-off is a little over 2V. I don't know what burst current it uses for the test.


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## Burgess (Oct 31, 2007)

Lots of great info on this thread.


Thank you to everyone for their contributions. :thumbsup:


And especially to SilverFox ! :bow:

_


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## bob_ninja (Oct 31, 2007)

I still don't get this fascination with 0.5C to 1C charge rates. What problem are you trying to solve?
You and others keep saying that you discard batteries when their capacity drops by 20%. Therefore you DON'T HAVE ANY crap cells that may not give dV termination signal. Everyone keeps saying that they have zero problems with new cells (except for specific issues with specific chargers). So if 0.1C and 0.2C and 0.3C charge rates work as well for new cells then why wouldn't I have the freedom to choose below 0.5C????

As mentioned here, some cells age faster than others and you could possibly have a mix, not notice some cells became crap. If someone is truly lazy or too busy with kids and other stuff, then he/she will get the 15 min charger and smack them with 10C. They won't bother with LaCrosse and Maha chargers, monitor them, etc. So again no chance of missed termination.

Even if people want to keep using cells past 80% threshold, such as me say, then there are a number of methods to eliminate the risk of missed termination besides using 1C charge rate. In fact most of other methods are superior:

- BC900 and others have a time limit; still you could put your own timer on the power supply; missed termination doesn't matter if charger is shut off after max possible charge time for a cell
- monitor yourself from time to time, check temperature and such (if willing)
etc.

If I were really concerned about missed termination then I wouldn't really care what charge reate is set. I wouldn't believe any rate. I would place a timer on the outlet and calculate the maximum safe charge time. Simple.

So this charge rate nonsense is pointless. Of course manufacturers will suggest higher charge rates to produce a stronger signal as they want to minimize liability. As a side benefit they can heat up reducing their lifespan so that you have to buy more new cells sooner. Win-win for them.

For us not so. If you don't like the X% risk of missed termination at 0.1C then you won't like a X-20% risk of missed termination at 1C either. Crap cell is still crap cell. I wouldn't trust it at any charge rate. So either discard (as you said) or place a timer. Higher charge rate doesn't solve anything.

Now, I refuse to believe that I have to heat up cells a lot to obtain a reliable termination signal. If Maha and other fancy chargers can keep them cool at 1C then by all means go for it. I only have BC900 and I think they get fairly warm at 0.5C so I won't go any higher. One day when I get Maha 9000 then I'll try 0.5C and 1C, see how hot they get.

In any case I refuse to heat up my cells too much, new or old. I know it is a subjective measure we already fought over. It is also subjective choice to keep batteries below 80% remaining capacity or longer than 3 years. I don't want to waste stuff and pollute environment due to unfounded paranoia of missed termination. If I lived my life that way I would lock myself in the basement and never set a foot outside. Too much risk 

Seriosly, you have far higher risk of a traffic accident, some sort of crime and other stuff than from a missed termination on BC-900 due to a lower charge rate burning down your house and you in it. Let's put things into perspective here. There are people duying all over the world from far more mundane things including hunger. Get over it.

by Stubborn-sub-0.5C-SOB 

P.S.: On the other hand you did post good questions about Sanyo's sub-0.5C reccomendations for Eneloops. That is a far more worthy topic of investigation IMHO


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## TorchBoy (Oct 31, 2007)

Bob, 0.1C is really only used with a timed 16 hour charge. (Or sometimes just 14 or 15 hours.) And if I understand the heat thing correctly, with good cells you'll only get much heat when they're full, which is when you want the thing to stop being charged. At the higher charge rates it's more likely to stop at that point. Overcharging damages cells, so why not use a rate which will be most likely to prevent that?


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## SilverFox (Oct 31, 2007)

Hello Bob,

Interesting comments, however let's take a little closer look at them...



bob_ninja said:


> I still don't get this fascination with 0.5C to 1C charge rates. What problem are you trying to solve?



One of the biggest complaints I hear about using rechargeable cells is that no one seems to be able to get anywhere near the expected 500 cycle life. Some people report that their cells die after as few as 50 cycles.

There are basically 4 things that control cycle life: quality of construction, storage conditions, usage, and charging. 

A lot of people are under the mistaken belief that they can improve cycle life through slow charging. I have demonstrated that this is not entirely true. You can get away with slow charging when the cells are new, or if you limit the maximum charge rate to 0.1C, but as cells age, their chemistry changes a little. This change can throw off the end of charge termination signal.



bob_ninja said:


> You and others keep saying that you discard batteries when their capacity drops by 20%. Therefore you DON'T HAVE ANY crap cells that may not give dV termination signal. Everyone keeps saying that they have zero problems with new cells (except for specific issues with specific chargers). So if 0.1C and 0.2C and 0.3C charge rates work as well for new cells then why wouldn't I have the freedom to choose below 0.5C????



I guess you missed the part where I said that the cells used for the demonstration were marginal cells, but did not yet qualify as crap cells. These cells are 850 mAh cells, and are performing to about 700 mAh. That puts them at around 82%. However, I could very easily turn them into crap cells by continuing to charge them at a rate that causes missed terminations.

So, now I have a choice. I can slow charge my cells, suffer through missed terminations, and end up with 10 - 20 cycles from them, or I can use a proper charge rate and get 100 - 200 cycles from them.

I will admit that a person that doesn't care about cycle life will probably not be interested in the information in this thread...



bob_ninja said:


> Even if people want to keep using cells past 80% threshold, such as me say, then there are a number of methods to eliminate the risk of missed termination besides using 1C charge rate. In fact most of other methods are superior:
> 
> - BC900 and others have a time limit; still you could put your own timer on the power supply; missed termination doesn't matter if charger is shut off after max possible charge time for a cell
> - monitor yourself from time to time, check temperature and such (if willing)
> ...



Let me get this straight... a timer is superior to detecting the charge termination signal... I am sorry, but this is absolutely not true.

Here is an example. I have my 850 mAh AAA cell that I have been using for a few days, but this weekend I am going camping and I want to make sure it is fully charged up and ready to go. I haven't really kept track of how much I used the cell, so what do I set the timer for?

The only way this works is if you completely discharge the cell before charging. This is not practical because a complete discharge reduces cycle life, and this whole process takes a lot of time. In addition, a lot of chargers do not have a discharge function.

All of the sudden what you thought was simple has now become complex... Now, instead of simply putting the cell in the charger and choosing an appropriate charge rate, we now have to log the number of minutes that we use the light, how long since the cell has been charged so we can account for self discharge, and we need to test for the internal resistance of the cell so we can factor in the charge acceptance. Once we have all of this information, then we can pick a proper charge time.

Looking at the timer used in the BC-900 we find that it is set for around 3000 - 3300 mAh. I put my partially discharged 850 mAh AAA cell in the BC-900 and choose a slow charge rate. It puts 3000 mAh into the cell before timing out because of the missed termination. How may cycles do you think it will last under this type of abuse?



bob_ninja said:


> So this charge rate nonsense is pointless. Of course manufacturers will suggest higher charge rates to produce a stronger signal as they want to minimize liability. As a side benefit they can heat up reducing their lifespan so that you have to buy more new cells sooner. Win-win for them.
> 
> For us not so. If you don't like the X% risk of missed termination at 0.1C then you won't like a X-20% risk of missed termination at 1C either. Crap cell is still crap cell. I wouldn't trust it at any charge rate. So either discard (as you said) or place a timer. Higher charge rate doesn't solve anything.



Since no one wants to follow the battery manufacturers recommendations, it is pure speculation that charging at their suggested rates will reduce a cells life span. In fact, as I have demonstrated, following their recommended charge rates has a very good probability of exactly the opposite.

I would suggest that you re-read the first post. The cell that did not provide a strong end of charge signal at a low charge rate, provided an excellent end of charge signal when charged within the 0.5 - 1.0C range. Also, as I mentioned earlier, the cell is an aged cell, but not a crap cell. I don't believe that it is pointless to use a proper charge rate in a effort to maximize the life from my cells.



bob_ninja said:


> Now, I refuse to believe that I have to heat up cells a lot to obtain a reliable termination signal. If Maha and other fancy chargers can keep them cool at 1C then by all means go for it. I only have BC900 and I think they get fairly warm at 0.5C so I won't go any higher. One day when I get Maha 9000 then I'll try 0.5C and 1C, see how hot they get.
> 
> In any case I refuse to heat up my cells too much, new or old. I know it is a subjective measure we already fought over. It is also subjective choice to keep batteries below 80% remaining capacity or longer than 3 years. I don't want to waste stuff and pollute environment due to unfounded paranoia of missed termination. If I lived my life that way I would lock myself in the basement and never set a foot outside. Too much risk
> Seriosly, you have far higher risk of a traffic accident, some sort of crime and other stuff than from a missed termination on BC-900 due to a lower charge rate burning down your house and you in it. Let's put things into perspective here. There are people duying all over the world from far more mundane things including hunger. Get over it.
> ...



Who said anything about heating the cells up a lot? When I charge at 0.1C, I notice that my cells warm up around 10 F over ambient. The cell that missed termination went to 20 F over ambient when I terminated the charge. The cell that terminated properly ended up 15 F above ambient. In this case, a properly terminated cell charged at a higher charge rate ended up at a lower temperature. If I had left the non terminating charge rate cell on the charger for a longer period of time, I am sure the temperature would have increased a little more.

By all means, keep your cells cool. They will warm up while charging, but they should not get hot. I am not worried about a missed termination burning someones house down (unless they are using the BC-900 :devil: ), but I am concerned about destroying cells through improper charging methods.

Tom


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## cy (Oct 31, 2007)

either .1c or 1c with schulze for me...


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## koala (Oct 31, 2007)

Regarding timer based charging setup. It's only good for breakin in new cells. If you like to use timer based charging, I suggest that a undercharge time is better than a full charge time. This is why...

A dumb charger with a set rate of charging is built cheap, and cheap comes at a cost. The electronic parts, of course are not close tolerance so a 200mA charger may be supplying 160mA to 240mA (+-20% tolerance). 
So you have a 2000mAh cell, say you do a standard 16hr x .1C charge you should get 3200mAh but because of tolerance you may end up with 3840mAh. That's a lot of gentle over-charging there.

The total amount of current going in to your cell also depends on the age(internal resistance) of the cell, ambient temperature, cell temperature. It's all in one. There's nothing wrong with gently charging these cells but make sure that you are not over feeding otherwise it defeats the purpose of gentle charging.


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## Bones (Oct 31, 2007)

SilverFox said:


> So, now I have a choice. I can slow charge my cells, suffer through missed terminations, and end up with 10 - 20 cycles from them, or I can use a proper charge rate and get 100 - 200 cycles from them.



Pretty dismal choice when even the most reputable manufacturers are now advertising up to 1000 cycles.

How can they do that considering your best case prediction is only 10 to 20 percent of that number?


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## Bones (Nov 1, 2007)

SilverFox said:


> So, now I have a choice. I can slow charge my cells, suffer through missed terminations, and end up with 10 - 20 cycles from them, or I can use a proper charge rate and get 100 - 200 cycles from them.





SilverFox said:


> The only way this works is if you completely discharge the cell before charging. This is not practical because a complete discharge reduces cycle life, and this whole process takes a lot of time. In addition, a lot of chargers do not have a discharge function.



I'm also curious as to whether you would predict more or less than 100 to 200 cycles if you actually carried your latter thought on charging at .1C to fruition?

Say Mr.Al designed a charger that would discharge to .9 volts, if that's deemed optimal for this purpose, and then did a timed charge at .1C.

Would this not negate the large chrystal growth you've mentioned and absolutely prevent overheating and overcharging?

With a little testing you could determine how long it takes your particular cells to reach a fully charged state, which I understand should be between 14 and 16 hours.

After that, it would very much seem to be a safe, simple, foolproof, set it and forget it function, and especially practical if the charger can be built inexpensively.

Any shades of Ronco infomercials invoked by the phrase 'set it and forget it' is absolutely unintentional...


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## SilverFox (Nov 1, 2007)

Hello Bones,

Please understand that my comment about the 100 - 200 cycles was directed to the aged 850 mAh AAA Moden cells. They already have over 100 cycles on them. If I continue to slow charge them (using a charge rate in the 0.2 - 0.4C range) and get multiple missed terminations, I would only expect 10 - 20 cycles would be remaining in them until they qualified as crap cells. However, if I continue to charge at the recommended 0.5 - 1.0C rate, I would expect that there would be 100 - 200 cycles remaining in them.

Now moving on to a general statement that I may have mentioned earlier...

If you charge cells at 0.1C and use them in applications that draw a maximum of 0.2C, you can expect to get 500 cycles from normal NiMh cells, and Sanyo seems to think that the Eneloop cells would be good for 1000 cycles. You also have to stop the discharge when the cell reaches 1.0 volts under load.

If your application involves currents higher than 0.2C, you may suffer from voltage depression by large crystal growth from charging continually at 0.1C.

There is no exact formula for crystal size, but in general, crystal size is proportional to charging current. Slow charging forms larger crystals than quick charging. The old saying that you should charge at the same rate that you discharge at has some truth in it, until you get to discharge rates exceeding 1C. The various studies with the 15 minute chargers have shown that charging at high rates cuts into cycle life. Charging at 2 - 4C gives you cells that perform very well, but you have to live with 100 - 200 total cycles.

The 0.1C charging rate is low enough that you can have some degree of overcharge without damaging the cell. Using a timed charger that charges at 200 mA, you could charge your Eneloop cells for 14 - 16 hours and not have to worry about heat and damage due to overcharging. When the cells are fully charged, grab them and use them in your 400 mA application, and you are good to go.

However, if you want to use your Eneloop cells in a Mag85, you won't get the best performance using that charge regime.

Tom


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## Bones (Nov 5, 2007)

SilverFox said:


> If your application involves currents higher than 0.2C, you may suffer from voltage depression by large crystal growth from charging continually at 0.1C.



Thanks for another very informative response SilverFox.

However, I seem to be confused with how large chrystal growth is dealt with.

It has been my understanding that large chrystal can only be broken up by a deep discharge (apparently to 1 volt).

Since my model provides for a discharge to 1 volt before every recharge at .1C, I don't see how large chrystal growth and the attendant voltage depression could ever be a factor.


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## SilverFox (Nov 6, 2007)

Hello Bones, 

You have to factor the discharge rate into things...

If you discharge at 0.2C or lower, there should be no problems with voltage depression, however, if you discharge at 1C, the large crystals you have will not readily dissolve, but simply depress the voltage as they try to give up their energy.

Tom


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## koala (Nov 6, 2007)

Okay, so how often should one do a 'slow' discharge to dissolve the crystals? Once every 20 cycles?

I am thinking... cells in camera flash application. They are subjected to momentary high current discharge. Does it cause large crystals too?

Sorry if I am asking questions that has been answered, I am the kind of kid who sit at the back of the class, playing with some nonsense...


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## SilverFox (Nov 6, 2007)

Hello Vince,

It would be best to take care of your cells so that large crystals don't form in the first place...

The crystals are formed during charging, or during the initial self discharge from full charge, so I don't believe there is any issues with using your flash.

I try to do a slow discharge once a year to check the health of my cells. When performance drops, I will try to re-condition them to see if they will come back.

So, when you notice your cells under performing, you can do a slow discharge to see if they are simply worn out, or if they can be helped by trying to dissolve the large crystals.

Tom


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## MrAl (Nov 6, 2007)

Hi again,

Tom, when you do your slow discharge what do you use to discharge
them? Do you think a 5 ohm resistor (about 200ma) is too fast?


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## SilverFox (Nov 7, 2007)

Hello Al,

I generally do a standard 5 hour discharge. I have been using my CBA for this, but since getting the C-9000, I have been using it on Break-In.

Tom


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## LuxLuthor (Nov 7, 2007)

Tom if you are using your Schultze, etc. do you use the recommended *4mV/C dV termination* for 0.5 - 1C NiMH charging?


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## SilverFox (Nov 7, 2007)

Hello LuxLuthor,

My Schulze (isl 6-330d) does not allow me to adjust the sensitivity for charge termination. I put it on Auto C and end up with fully charged, cool cells. To get warm cells, I have to select a 1C charge rate. 

I am not sure what Schulze uses for termination. I have seen cells terminate on a number of differing parameters. 

Tom


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## LuxLuthor (Nov 7, 2007)

I asked because there is also an Auto mode with my Hyperion 1210i that sets it to the "standard" 4mV/C but I can lower or raise it in manual mode. That's strange since I get "warm to hot" end charging of NiMH cells even if I select 0.5C. I mostly have been using it for the Elite AA and 2/3A cells/packs.


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## SilverFox (Nov 7, 2007)

Hello LuxLuthor,

Must be a different charging algorithm. Also, I wasn't aware of any "standard" for -dV termination. Sanyo has a lot of testing done using 10 mV, but a common range is 2 - 5 mV for NiMh cells.

Does your pack also get hot at 1C charging?

Tom


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## LuxLuthor (Nov 7, 2007)

SilverFox said:


> Hello LuxLuthor,
> 
> Must be a different charging algorithm. Also, I wasn't aware of any "standard" for -dV termination. Sanyo has a lot of testing done using 10 mV, but a common range is 2 - 5 mV for NiMh cells.
> 
> ...



The Hyperion manual is where they stated NiMH -dV should be 4mV/C for NiMH, and 8mV/C for NiCd in case you changed the Auto profile. I set it to 2mV/C a couple times on Manual mode, and that seems to work great while I observed the charging cycle, but I mostly use their 4mV "standard" for this Hyperion model.

Yes, it gets hot (not excessively) at end of charge cycle at 0.5C, 1C, and 2C which I have tried all on these Elite cells just to see how they came out. I can tape on my Fluke 179 temp probe next time to see how hot if you want.


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## SilverFox (Nov 8, 2007)

Hello LuxLuthor,

If it is not too much bother... it would be interesting to check out.

The Schulze adjusts the charging current (regardless of what you set it at) according to the internal resistance of the battery pack, or cell. I noticed around a 15 - 25 F temperature rise when charging the NiMh B90 replacement packs. These were 3700 mAh cells being charged at 2 amps. I was able to get higher temperatures by charging my Mag85 9 cell battery with Titanium PowPower 1800 mAh cells at 4 amps.

Tom


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## LuxLuthor (Nov 9, 2007)

SilverFox said:


> Hello LuxLuthor,
> 
> If it is not too much bother... it would be interesting to check out.
> 
> ...



Tom, I will check out what you are asking, but I'm not sure what you want me to be checking/charging current/timing, etc. I have a Fluke 179 so I could get accurate temps on the cells.


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## SilverFox (Nov 9, 2007)

Hello LuxLuthor,

Sorry, I am interested in the temperature of the cells when they are charged at 1C.

Tom


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## LuxLuthor (Nov 15, 2007)

SilverFox said:


> Hello LuxLuthor,
> 
> Sorry, I am interested in the temperature of the cells when they are charged at 1C.
> 
> Tom



Tom, I wanted to check this on several types of cells with my Hyperion 1210i before answering you. These were welded packs with 16AWG charge leads on end cells.

The 14.4V (12s 2/3A Elite 1500mAh NiMH) pack reaches temp peak of 105° to 107°F when charged at 1C & .8C at -ΔV 4mV termination on two test runs. 

4s Eneloop pack charged at 1C was 98°F & 92°F at 0.8C at -ΔV 4mV termination.

7s Elite 1700mAh AA pack peaked at 102°F with 1C at -ΔV 4mV termination.


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## SilverFox (Nov 15, 2007)

Hello LuxLuthor,

Those seem like very reasonable temperatures.

Tom


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## Utik (Nov 16, 2007)

What does all this say about the usefulness of the Maha 401FS? Based on earlier testing reports, it gets cells too hot on fast charge. Now with the concerns about missing charge termination on slow charges, does this render this charger a bad option?


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## Hollow Man (Nov 16, 2007)

Granted I'm by no means an expert, but I posted my findings with the C401FS here. Basically, I've been happy with it, but I admit that I've only been using cells that are no longer than a year or so old, and I don't cycle them tons. Perhaps as time goes on they'll miss terminations, but with the way I use batteries, I tend to get quite a few years out of them, so I'm definitely saving money over using alkalines.

The oldest cells I use are 850 mAh Energizer AAA in my mp3 player. Those things are probably crap by the standards of this forum. I can't check, since I don't have a fancy charger to see what their capacity currently is, but the pair I swap in and out still work well enough for me.

But it's probably time to swap them for my 1000 mAh PowerEx and see how much more life I get in the player. It won't kill me: I have more batteries waiting around doing nothing (fairly new ones to boot!) than I have in devices. 


-HM


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