# Interesting... but not recommended...



## SilverFox (May 20, 2010)

Children often forget to turn off their battery operated toys. Sometimes they will go 
back to play with the same toy again, but often they just move on to the next 
adventure.

I always recommend trying to train everyone, including children, in the proper use and 
care of rechargeable batteries, but some are more receptive to the information than 
others...

I like Eneloop cells. They do everything a rechargeable cell should do and seem to 
handle a fair amount of abuse also. My toys, oops, I mean my grandchildren's toys  , 
are all powered by Eneloop cells. Most of my cell testing has to do with performance, 
but this time I ventured into the "dark side" - abuse testing.

From here on, the story gets a little abusive, so kids and sensitive people should 
probably tune out... :devil: 








Still with me...?

OK, how many times has it been mentioned that it is not the best practice to over 
discharge cells? Yes, lots and lots is a very large number.

Still, I run into people that don't want to use excellent cells in their toys, or their 
children's toys because they fear over discharging them, and ruining them.

I grabbed an Eneloop cell that I had purchased some 3 years ago and have been 
abusing it by not using it. 

I ran a discharge at 500 mA to see if there was anything left in it, and it came in at 
1250 mAh on the C9000. Not too bad, about 64% capacity left after 3 years of storage, 
and these cells weren't completely charged to start with. I believe they started at 
around 75% of full charge.

The next step was to do a Break-In cycle. The cell came in at 1925 mAh.

I then put the cell in a light and drained it. I left it in the light overnight and over 
discharged it. I then took a piece of foil and clamped the cell with the positive and 
negative terminals in a direct short.

Two days later, I took the cell out of the clamp. The voltage rebounded to 0.1 volts.

Please note that I am working with a single cell and there is no opportunity for reverse 
charge. If I can bring myself to do it... I may drag out another cell and repeat this 
with a pair of cells.

At any rate the C9000 accepted the cell for charging without problems. I did another 
Break-In cycle and the capacity came in at 1939 mAh.

Wow, a slight increase in capacity in spite of being discharged overnight and shorted 
out for an additional two days.

I asked my grandchildren how long they would "loose" toys trying to figure out where in 
the spectrum of things two or three days fit in. They assured me that most of their toys 
would be played with in two or three days, but there may be some that could possibly 
get "lost" and go a little longer. Mom nodded in agreement, but thought that a week or 
two may be more realistic.

The next step was to once again drain the cell in the light overnight. I then shorted it 
out with my clamp and foil set up and left it for 5 days.

When I removed the cell from the clamp, the voltage rebounded to 0.008 volts. Once 
again the C9000 had no problems initiating a charge on the cell, however, once again I 
ran a Break-In cycle on the cell. This time the capacity came in at 1943 mAh. Wow, 
once again a slight increase in capacity.

The point of this exercise is that as long as the cell is not reverse charged, it seems to 
handle over discharging with ease. At least with a high quality cell and with the cell 
being totally shorted out for 5 days. Even in multicell applications, when Eneloop cells 
are being used, they should be well balanced and there should only be a very remote 
chance of cell reversal.

At any rate, if you go around and make sure the toys are shut off every 5 days, your 
cells should survive.

There is more...

Anticipating that some parents have very busy schedules, and checking the status of 
toys every 5 days would just be too much effort, I decided to do another test.

This time I discharged the cell in the light overnight, then shorted it out and clamped it 
and this time I left it for 14 days.

When I removed the cell from the clamp the voltage rebounded slowly to 0.002 volts. 

The C9000 had no problem recognizing it and I got an IR reading of 1.56. I ran 
another Break-In cycle and the capacity came in at 1946 mAh. Another slight increase.

I can't believe that shorting a NiMh cell is good for it, but it looks like it isn't too hard on 
it either. Wondering if the low self discharge capability was effected I let the cell sit for 
a little over 2 weeks, then ran a 500 mA discharge on it. It came in at 1746 mAh.

Many people save their crap cells to use with toys. The justification is that the cells are 
already crap so over discharging won't hurt them too much. I think that care for toys 
should be part of the experience of playing with powered toys, and I also think that 
crap cells should be recycled. Quality cells work much better in toys, and I think that 
children begin to understand that their toys last much longer because of the quality 
cells that are being used.

This round of abuse testing seems to indicate that even if the toy is left on and 
forgotten for two weeks the cell still has a chance to recover.

In the spirit of full disclosure... I will mention that this round of testing was sponsored 
by the influential chairman of "CSOCC."

That would be ME :devil:

Tom
Chairman of the Coalition to Stop Out Crap Cells (CSOCC)


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## Egsise (May 20, 2010)

:thumbsup:

Any information on what happens in multi-cell toys?


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## crizyal (May 20, 2010)

This is very interesting. I wonder what (if any) difference you would see with other brands of cells. I am particularly interested in the Titanium Brand of LSDs.


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## Ray_of_Light (May 20, 2010)

Hi Tom,

check "Guideline n. 1" on Ni-CD batteries at NASA:

http://www.nasa.gov/offices/oce/llis/0644.html

This is half-true with traditional Ni-MH, and is invariant for Ni-MH LSD. As long as you don't reverse charge them, LSD batteries should report no damage from "clamped" storage. In traditional Ni-MH (not LSD) the decay of the lattice alloy continues in any case, accelerated from temperature and overcharge.

The little capacity increase you measured is because you exercise the deeper layers of the nickel positive electrode with a 100% discharge. 

I fully agree and endorse the findings and implementation of your egregious committee on the ban of "crap" NiMh cells. 
My un-based feelings tell me that the "big boys" may want to start selling more down-to-earth, reasonable but lower capacity Ni-MH batteries, and then make a blanket replacement with LSD batteries. 
It would be the greenest move of all times in the battery world, which would reduce drastically the number of "crap" rechargeable batteries around. Provided that they can convince people to keep the batteries away from the chargers, after decades they have been saying the opposite.

Regards

Anthony


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## bthrel (May 20, 2010)

Why not do the clamp and foil set up whilst fully charged.. 

Just kidding, great test and information, gotta love those eneloops.

Brian


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## SilverFox (May 20, 2010)

Hello Egsise,

As soon as I can convince my grandson that he needs to loan me one of his toys for some testing I will try some actual testing with a multi cell toy.

My thought is that the Eneloop cells are very close in capacity, so if they are charged in an independent channel charger, there should be little chance of reverse charging.

How this works out in real life... who knows?

Tom


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## SilverFox (May 20, 2010)

Hello Crizyal,

I have no idea how other brands will perform, but if your guard against reverse charging during the discharge, they should be similar.

Try some and report back what happens.  

Tom


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## SilverFox (May 20, 2010)

Hello Anthony,

That Guideline is what gave me the courage to try this...

Do you have any idea what "long term" shorting (like months or years) would do to both NiMh and LSD chemistry?

Welcome to the CSOCC group.

Tom


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## crizyal (May 20, 2010)

I do not have the analyzing charger as you do and my results would be difficult to document. Might need to invest in yet one more battery charger... My wife can't figure out WTH I am doing with all of those chargers.


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## Ray_of_Light (May 20, 2010)

Tom, 

atomic hydrogen is stored in the "interstices" of the lattice alloy very tightly; this happens because the spatial charge distribution of the hydrogen atom, which is complementary to those of the reticule constituting the alloy.

Storing the Ni-MH battery in a clamped state leaves the alloy "reticule" empty.
There should be no difference in theory, in the sense the alloy shouldn't degrade faster if left empty. Practically, based on the design of the alloy which varies by battery brand, the hydrogen may well concur, on the long term, to keep the stability of the lattice structure.

In traditional Ni-MH batteries (those with cobalt and manganese in the alloy at the negative electrode - and no yttrium in the positive nickel electrode) the degradation of the alloy, especially in those with "high capacity", proceeds so fast that I doubt the lack of hydrogen may count as a significative factor of degradation.

In good LSD batteries, where useful lifetime can be a couple of decades or more, the lack of hydrogen in the alloy may favour a possible collapse of the reticule, by enhancing the effect of impurities in the long term.

In both non-LSD and LSD types, I don't see, at least theoretically, any negative effect on the positive electrode nor on the electrolyte - by clamped storage.

Now talking as flashaholic... I don't see the need to store LSD batteries in a shorted state, and I have already thrown away all non LSD ones. LSD batteries are a major - yet unnoticed - technological breakthrough, which I'm fully enjoying after the past nightmares with rechargeable batteries - of which, clamped storage makes me reminiscent...
...but. For the love of knowledge, and to better understand what happens to batteries left in toys turned on, I will discharge and then short circuit one LSD cell with known parameters, and we will check back here in six months time...

Anthony


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## TorchBoy (May 20, 2010)

Tom, my many thanks for doing this testing - not only useful data but well written also! This gives me great confidence in running single AA lights completely flat (or at least not worrying if I seem to be overusing them).

A while back I left a multi-cell caving headlamp on after a trip and when I found it many days later there was no sign of light at all. I vaguely recall cell voltages in the 0-0.4 V range. But I have no idea which cells they were as there wasn't any noticeable difference in performance. I strongly suspect you're right about them being fine if they have an equal charge to start with.


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## march.brown (May 20, 2010)

I have also got rid of all my non-LSD cells ... To be more accurate , I gave them to my Son-in-Law , as the Grandchildren get through a lot of batteries ... I also gave him three chargers as well , as I did have too many.

The other day , I was talking to him about LSD cells and he didn't know much about them ... After a few minutes , he asked me which were the best ... I said that my Eneloops were as good as any others , though I still use the GP Recyko cells and Hybrios ... Anyway , he has now sent off for eight AA Eneloops and has said that he will buy a few more each month plus a few AAAs as well.

I think that eventually most manufacturers will gradually cease production of non-LSD cells and as far as I am concerned it can't be too soon ... I used to top up my batteries every month or so ... Now I do it a couple of times per year ... I might have to consider discharging them fully at least once a year ... Perhaps I will make up a multi-cell discharge box with five ohm resistors ... The AA Eneloops should discharge overnight in 8 or 9 hours ... If I left them on for 12 hours , that should be OK.
.


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## 45/70 (May 20, 2010)

SilverFox said:


> This round of abuse testing seems to indicate that even if the toy is left on and
> forgotten for two weeks the cell still has a chance to recover.



Wow! While I was aware that eneloops are probably the best of the LSD cells, and LSD cells in general are much more resistant to abuse, I had no idea that a cell could hold up to that much abuse, and survive. Amazing results. oo:

I'd be curious to know if this cell has different discharge characteristics after being subjected to this torture test. The fact that the Maha seems to accept it and shows a very reasonable voltage during the impedance check, seems to indicate that the cell remains, more or less normal.

It would be interesting to do a discharge on the Maha to see if the voltage during discharge was "normal", or if the cell is suffering from voltage depression, however all indications point to this likely, not being the case.

What I'm wondering about, is how this cell would perform in a series application with other cells. I have some cells that are not in dedicated groups of 2, or 4 that I use for random applications, such as single cell lights. Occasionally cells from this random group are used in series applications of 3-8 cells. These applications don't rate a dedicated set of cells because of their infrequent use. I just wonder how mistreating some of the members of this group this severely, would affect others in the group in the long run. :thinking: Of course, this group does get analyzed once in a while, and relabeled according to capacity. The voltage under load is frequently ignored however, as they usually seem to be about the same.

Dave


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## Burgess (May 20, 2010)

Great thread, SilverFox !

:thumbsup:



Gives me even MORE respect & admiration for Sanyo Eneloops.

lovecpf
_


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## DM51 (May 21, 2010)

Superb story, and very useful to know! Many thanks, Tom


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## Black Rose (May 21, 2010)

Very interesting results.

I'm really impressed with how resilient that Eneloop is.

One thing I am curious about....what will this level of abuse do to the cells LSD capabilities?

I don't plan on brutalizing my Enloops & Duraloops like that  but I do happen to have a ROV Hybrid AA cell that was overdischarged a few months ago in a Wii remote.

I charged it up as soon as I found it and set it aside for a self-discharge test. I think I did a R&A on the cell and noted that the capacity had dropped a bit from previous results for that particular cell.

This weekend I'll be discharging it to see if the self-discharge rate has increased as a result of being over discharged.

Even if it is, the results from that test likely can't be applied across the board, due to differences in the components used for the various brands LSD cells.


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## glockboy (May 21, 2010)

:thumbsup:


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## BigHonu (May 21, 2010)

Thank you for the testing and information!


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## SilverFox (May 21, 2010)

Hello DM51,

Keep in mind that this is still experimental. Before we jump into this with both feet, I think it would be prudent to do more testing.

I was expecting some loss in capacity, and am surprised at the results - so far.

However, if further testing bears this out, we can drop the concern of over discharging and focus on reverse charging. It is also important to remember that Eneloop cells are very robust. Until we have similar data from other brands, I think caution should be exercised.

Tom


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## SilverFox (May 21, 2010)

Hello Black Rose,

I didn't see any drastic change in the LSD performance over a couple of weeks. Anthony (Ray of Light) is going to short a cell out for 6 months and see what happens. That should shed more light on this.

Tom


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## Curious_character (May 21, 2010)

Thanks for doing the test -- very interesting. Some time back, I was dinged, with a plausible counter-argument, for suggesting that overdischarging NiMH cells wouldn't be harmful to them, based on a lack of manufacturers' warnings against it. Looks like it turned out to be correct after all, at least for Eneloops.

One caution about measuring capacity with the MH-C9000: Early models will show considerably higher capacity for high-resistance cells than the cells actually have. The first units sold disconnected the discharge load momentarily to read cell voltage, terminating the discharge when the voltage reached a predefined level (0.9 or 1.0 V., I don't recall which). I had some old NiMH cells which had high internal resistance. Because the charger disconnected the load before measuring the voltage, the effect of the internal resistance was minimized. Consequently, the Maha indicated much higher capacity than a straight constant-current discharge to the voltage end point did. In a regulated flashlight, the current increases as voltage drops, so the Maha measurement would be even farther from observed capacity.

Maha changed this some time ago, so current models give a more realistic indication of capacity when cell resistance is high. As a possible way to spot which charger you have, look at the voltage while discharging at around C/4 (about 500 mA for an AA cell). My older one reads well above 1.2 volts at the beginning of the discharge; the new one starts out around 1.18 or so. The older units apparently disconnected the load to eliminate the contact voltage drop from the measurement. The newer ones read lower because of the drop caused by load current through the contacts.

So if you're using an older MH-C9000 for tests, you might want to check and make sure the cell resistance hasn't gone up as a result of the abuse. I doubt that it has, but my point is that an older Maha wouldn't catch it.

c_c


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## TorchBoy (May 21, 2010)

You should be able to get an idea of cell resistance by the initial resistance test the MH-C9000 does before starting to charge. If the figure is about 1.6 V (I think) then internal resistance of the cell won't have changed much.


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## Turbo DV8 (May 21, 2010)

SilverFox said:


> Wow, a slight increase in capacity in spite of being discharged overnight and shorted out for an additional two days... This time the capacity came in at 1943 mAh. Wow,
> once again a slight increase in capacity... I ran
> another Break-In cycle and the capacity came in at 1946 mAh. Another slight increase...


 

I don't know exactly what is going on here, but I don't think an increase in capacity with each abuse is necessarily indicative of a good thing. Right before each and every one of my ROV Hybrid AAA cells developed high rates of self-discharge (and just recently I've added two AA cells to that list) the accelerated self-discharge rate was preceeded by higher test capacities. I started a thread about it a while back, but nobody picked up on it. Again, don't know exactly what is going on, but the results of your experiment completely reminds me of what I began seeing immediately preceeding my cells going high SD. You may be measuring higher capacities with each abuse, but I would wager you are rapidly tossing away your low self-discharge traits of the Eneloops.


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## SilverFox (May 22, 2010)

Hello Turbo DV8,

Interesting...

Do you happen to have a link to that thread?

While the capacity did increase, it didn't do so by much. I also see some increase in capacity just by normally using the cell. 

However, I agree that more testing is needed, and we need to look at how different brands respond to being shorted out.

Tom


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## Black Rose (May 22, 2010)

SilverFox said:


> Hello Turbo DV8,
> 
> Interesting...
> 
> Do you happen to have a link to that thread?


Here it is: https://www.candlepowerforums.com/threads/253900

FYI, I tested the Rayovac Hybrid AA cell that was overdischarged in a Wii remote and it appears there is a very slight increase in it's self-discharge rate over the 4-month period it was set aside.

The overdischarged cell lost 332 mAh capacity, compared to 314 mAh for other battery that was in the same Wii remote.

I'm going to run another R&A on the pair of cells and then set them aside for another 4-month test.

EDIT: I had forgotten to mark the new capacity of the affected cell (found the voltage and capacity in a thread here ). 
The affected cell actually only lost 332 mAh capacity, not 399 mAh as previously posted.
The cell seems to have taken a hit on it's capacity rather than it's self-discharge rate, which is only 1.5% off from the other cell.


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## TorchBoy (May 22, 2010)

So it could have been reverse charged, because it was in a pair in the Wii remote?


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## Black Rose (May 22, 2010)

TorchBoy said:


> So it could have been reverse charged, because it was in a pair in the Wii remote?


It was down to 0.32v when I took it out of the Wii remote, so I don't think it was reverse charged.


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## Bullzeyebill (May 22, 2010)

Hi Tom, do you have a response for Curious Character's post, #21?

Bill


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## Lynx_Arc (May 22, 2010)

I bet if you did that 5 day clamp test on a rayovac hybrid you would lose about 1/3 of the capacity of the cell.


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## Mr Happy (May 22, 2010)

Black Rose said:


> It was down to 0.32v when I took it out of the Wii remote, so I don't think it was reverse charged.


On the contrary, I think that is almost a guarantee that it was reverse charged. When I NiMH cell has a resting voltage below 0.9 V that means it has practically no charge left at all -- it would struggle to provide more than a few mA of current. For all practical purposes such a cell would behave like a resistor in a series circuit.

Now on the plus side, mild reverse charging might not be all that harmful. It probably takes repeated and extended reverse charging to do major damage to a cell.


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## 45/70 (May 22, 2010)

Mr Happy said:


> On the contrary, I think that is almost a guarantee that it was reverse charged. When I NiMH cell has a resting voltage below 0.9 V that means it has practically no charge left at all --



I think Mr H has a good point here. In my experience with reverse charging cells, which is mostly with NiCd cells, any cell that has an OC voltage of 1.00 Volt, or below has most likely been reverse charged if it was used in series. If you take the voltage reading fast enough after use, you can still someimes get a negative reading. After a few seconds though, it will return to a positive voltage. Of course if the cell has been reverse charged for any length of time, it will remain at a negative voltage.

Dave


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## TorchBoy (May 22, 2010)

45/70 said:


> In my experience with reverse charging cells, which is mostly with NiCd cells, any cell that has an OC voltage of 1.00 Volt, or below has most likely been reverse charged if it was used in series.


Tom found that his cell rebounded to a whole 0.008 V after being shorted for days, not after being reverse charged.


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## Mr Happy (May 22, 2010)

TorchBoy said:


> Tom found that his cell rebounded to a whole 0.008 V after being shorted for days, not after being reverse charged.


I was doing a test yesterday with deep discharging some cells. I had a cell that was over discharged down to 0.9 V OC, and when I attached a 2 ohm resistor to it the voltage dropped rapidly to ~60 mV. You can imagine under those circumstances it would take very little to reverse polarize it.

If you have a meter with a battery test function you could try a similar test. Measure an empty cell on the volts range and on the battery test range and see how much the voltage changes.


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## 45/70 (May 23, 2010)

TorchBoy said:


> Tom found that his cell rebounded to a whole 0.008 V after being shorted for days, not after being reverse charged.



Not sure what you mean here, Torch. I was just pointing out, as Mr H did, that if Black read 0.32 Volt off of a cell that had been used in series, that it almost certainly had been reverse charged. It's just that by the time you pull the cell out and measure the voltage, it has already recovered. The exception would be, if a cell were to be reverse charged for some time, then it may actually read a negative voltage for some time, or even permanently, until charged.

Dave


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## SilverFox (May 23, 2010)

Hello Bill,

Both of my C9000 chargers have the revised firmware.

Tom


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## jcw122 (May 23, 2010)

The original post is exactly why I use NiHMs, if you try any of that crap with Li-Ion you get a nice big  or simply an unusable battery. The power benefits of Li-Ion just don't outweigh the risks for me.


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## Turbo DV8 (May 25, 2010)

SilverFox said:


> Hello Turbo DV8,
> 
> Interesting...
> 
> Do you happen to have a link to that thread?


 

OK, my work computer has restricted features, so I cannot copy and paste a link, but if you search the batteries section for, "Why does a cell's apparent capacity increase...?" you will find it. Or search for posts started by myself and it is on the first page results. Silverfox actually did reply to the post.


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## SilverFox (May 26, 2010)

Hello Turbo DV8,

Found it.

I am not sure what was going on with your cells. It could be that the increase in capacity was due to heat, or the break down in the LSD feature may have exposed some additional electrode material.

In my case, I think the increase in capacity was simply due to exercising the cell. Keep in mind that these cells usually show a slight increase over the first few charge/discharge cycles. Also, remember that in my case the increase in capacity was very small. I think the first increase was 0.007% and the next increase dropped to less than half that.

However, we must keep in mind that this is a test. I may find that my LSD features on my cell have been damaged, and my cell will join yours...

Tom


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## TakeTheActive (May 27, 2010)

*Re: Interesting... but not recommended... (aka Running NiMH Cells FLAT!)*



SilverFox said:


> Children often forget to turn off their battery operated toys...


I'm going to suggest the same thing to you that I just did to Newbie *Gazoola* - please consider EDITing your title to include more information for others to find when SEARCHing:
*Interesting... but not recommended... (aka Running NiMH Cells FLAT!)*​
He might have found and read it, considering his current situation.


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## Ray_of_Light (May 28, 2010)

Ok, it is friday afternoon.

Two eneloops are discharged and clamped short circuit. They had 5 cycles on them, 1980 mAh capacity tested with the RS-900 (the European version of the BC-900), firmware revision # 32. They were manufactured in 2006, never used before this test. They both measured 1480 mAh capacity after almost four years from manufacture, I would say thay have an excellent charge retention capability.

The other tests I am running are about measuring the fading of LSD capability. The idea is to categorise the decay of LSD capability of LSD cells versus cell age, cell cycles, and cell overcharge.

I am using, for this test, three sets of four of 2100 mAh Ready-to-use Varta cells. The same cells are marketed as "ROV hybrids" in the U.S. Two sets are resting, one has been left in the charger which provides few mAs of "maintenancce charge".
For reference, I am running the same test on a set of four 2000 mAh white-top Duraloops.
I have run one cycle per day on each of the above Varta and Duracell batteries.
The batteries are recharged with a Duracell indicator charger, with a control cycle every ten on the RS900. I remove the batteries from the charger as soon the charge is ended. 

I run this for fifty days, so the batteries have 50 cycles each in a normal usage pattern.

Today are sixty days the batteries are resting. A measured the capacity of one of the batteries of each set, and the Varta showed 90%, the Duraloop 93%.
The Varta which has received sixty days of maintenance charge delivered 82% of the capacity.

I plan to keep the test going for another six months. At the end, I'll take care of cut open the cells to measure the decay of the lattice alloy and the eventual formation of nickel dendrides.

Up to now, I can say that LSD capability don't decay with the age of cells. ALmost five years old Eneloops, still working like new, confirm the hypothesis made from theorethical assumptions.

Regarding the decay of LSD capabilities with number of cycles, the reasonable theoretical hyphotesis is that the battery will give up its LSD when nickel from lattice alloy will deposit on the separator, which should start to happen at the 500 cycles mark (1500 on the revised eneloops...)
To verify this, I will have to add fifty cycles at the time to the test batteries, and wait six more months every time to measure the differential of LSD capabilities. 
We should have started these tests in 2006...

Regarding the decay of LSD capabilities with overcharge, I can already tell that it is the most likely LSD killer, as proved from the batteries left under "maintenance charge". I use quotes because I want to emphasise that "mainteinance" in this case is sinonimous of "killing"...
From a theorethical point of view, "maintenance charge" uses the catalyst properties of the lattice alloy at the negative electrode to recombine oxygen and hydrogen into water. The reaction produces a lot of heat, and protect the battery from explosion and leakage, but it has a destructive effect on the alloy. Any overcharge will decrease the capacity of the battery and its LSD property, this is why I pull off the batteries from the charger at the end of charge cycle.


Have a nice weekend you all

Anthony


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## 45/70 (May 28, 2010)

Good Information, Ray



Ray_of_Light said:


> Regarding the decay of LSD capabilities with overcharge, I can already tell that it is the most likely LSD killer, as proved from the batteries left under "maintenance charge". I use quotes because I want to emphasise that "mainteinance" in this case is sinonimous of "killing"...



This seems to further confirm what SilverFox and others have seen. LSD cells don't like to be trickle charged!

Dave


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## Ray_of_Light (May 28, 2010)

I just found a link to a document I had, which is very explicative about the stray deposits on the separator:

http://www.electrochem.org/meetings/scheduler/abstracts/216/0268.pdf

Look at the picture of the separator. The black deposit is manganese and cobalt coming from the lattice alloy. An Energiser AA 2500 mAh, and after 10 cycles had a similar situation.
Trickle charge produces such deposits even in absence of cobalt and manganese.

Regards

Anthony


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## Bullzeyebill (May 28, 2010)

So use a charger that does not trickle charge, and turns off when fully charge is reached? Which chargers do this? What voltage would be fully charged, but not overcharged? I have noted, from posts, that sometimes Eneloops will come off of a charger at almost 1.5 volts. Is that to much charge?

Bill


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## 45/70 (May 28, 2010)

Ray_of_Light said:


> Trickle charge produces such deposits even in absence of cobalt and manganese.



Well, I've known since I started using NiMH cells in the late 90's, that they were less tolerant to trickle/overcharge (and thus shouldn't be charged on NiCd chargers). That is likely a major part of the reason why.

Dave


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## lyyyghtmaster (May 28, 2010)

Yes, I seem to remember that intolerance to constant trickle charge being trumpeted by the big manufacturers right from the beginning. Now that we have LSD cells, where are the chargers that shut off completely and don't trickle charge at all?

On an earlier note, I run Eneloops in my D20 and a while back ran a pair to the completely dark point when I didn't notice it was on (full brightness) in my holster. I immediately marked the lower voltage of the two cells and have been tracking it over several complete cycles since. It does not seem to have suffered any ill effects from that mistreatment compared to the other cell of that pair! That is quite amazing! Maybe the flashlight acts to reduce the damage? This torch draws enough current at full that it dims way down when the cells still seem to have about a hundred mAh left in them, but I haven't measured how this observation relates to the discharge point where there is no light left at all.


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## Ray_of_Light (May 28, 2010)

The sealed Ni-CD batteries reforms water with an indirect chemical reaction, which requires the presence of oxygen under pressure (about 4 bars). This is a chemical reaction that, provided the Nickel and the Cadmium are of high purity and the seals of the battery canisters are of good quality, can go on indefinetively.

The Ni-MH battery reforms the water based on the catalytic properties of the lattice alloy. The main advantage of this is the fact that the positive nickel electrode doesn't need to be half-capacity of the capacity of the negative electrode, as it was in the Ni-CD to avoid formation of gaseous hydrogen. With the same size positive electrode, a Ni-MH battery has double capacity of a Ni-CD battery.
The negative side of using the negative electrode of Ni-MH battery as catalyst is the stress placed upon it. In a 2000 mAh AA Ni-MH cell, if you overcharge it of 2000 mAh, (even very slowly) it is like you detracted one cycle from its cycle life.

Regarding the end voltage of a Ni-MH battery, things are a bit complicated. The nickel has different oxidation states, which influences the voltage in manner which is not proportional to the state of charge of the battery. Also, the purity of the chemicals used, the concentration and composition of the electrolyte, the temperature of the battery, its state of conservation and the number of cycles influences the end voltage. Therefore, a charger stops the charge when the relative voltage (during the charge) stops climbing and starts a slow descent (from 2 to 10 millivolt, the famous "- delta V").
To add to this, some off brand or old batteries do not provide this voltage drop, further complicating the issue of charge termination. For these batteries, you need to use a timed charger or use a programmable charger set to "zero-delta-V" termination.

If you use any common, good single channel charger, and quality LSD batteries, just remove the batteries when the charger indicates end of charge. Voltage can well be 1.5 V off the charger, and setting to 1.4 V after 24 or more hrs. LSD batteries will stabilise around 1.3 volts in the months to come, while non-LSD will have a steady decline, which can last from few days up up to two months, depending on their charge retention capabilities and the ambient temperature.

Hope this helps

Anthony


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## Battery Guy (May 28, 2010)

Greetings Everyone,

So here's the deal with respect to over discharge of NiMH cells.

There are three stages of discharge, as shown this plot copied from the 3rd edition of the Handbook of Batteries:







The three stages of discharge are described as follows:

Stage 1: Normal discharge

No gas products are generated or consumed.

Negative electrode: MH + OH- --> M + H2O + e-
Positive electrode: NiOOH + H2O + e- --> Ni(OH)2 + OH-

Stage 2: Hydrogen evolution at the positive electrode (cathode)

Stage 3: Oxygen evolution at the negative electrode (anode)

As you can see from the graph above, the cell voltage must go negative in order to get to Stage 2 discharge. As long as the cell stays at a positive voltage, there is very little or no damage that should occur in the cell. 

The real damage comes when the cell goes into Stage 3 discharge, and oxygen is evolved at the negative electrode (which is actually the positive electrode during reversal, but let's not confuse the issue) simultaneously with hydrogen at the positive electrode (which is actually the negative electrode during reversal). During this stage of discharge, several side reaction occur in the cell that cause irreversible damage to the cell (e.g. corrosion of the metal hydride alloy). You are also electrolyzing your electrolyte during this stage, and will therefore loose water in the cell in the form of hydrogen and oxygen gas. 

Based on my experience with NiMH cells, you won't actually overdischarge them and cause damage unless you get into Stage 2 or Stage 3 discharge. Of course, in order to get to Stage 2 or to Stage 3, you need to drive the cell into reversal. This means that you should not get noticeable degradation in performance by simply shorting a cell and clamping it between conductors in order to drive the voltage to 0V. 

Cheers,
Battery Guy


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## 45/70 (May 28, 2010)

Real quick, as I have to go, I read somewhere where when a NiMH cell was discharged to a point below ~0.9 Volt, that the separator was weakened. As I remember, any damage done because of this, was dependent on how long and how far below this voltage the cell was discharged. This was in reference to regular NiMH cells, not LSD.

Dave


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## march.brown (May 29, 2010)

Battery Guy said:


> Based on my experience with NiMH cells, you won't actually overdischarge them and cause damage unless you get into Stage 2 or Stage 3 discharge. Of course, in order to get to Stage 2 or to Stage 3, you need to drive the cell into reversal. This means that you should not get noticeable degradation in performance by simply shorting a cell and clamping it between conductors in order to drive the voltage to 0V.
> Cheers,
> Battery Guy


 Does this mean that on a single cell torch , the battery will not be damaged by totally discharging it , whereas with a multi-cell torch it would be possible to drive one of the cells into reversal and thereby damage it ?

If this is so , it is a good reason to use a single cell torch in preference to a multi cell torch.
.


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## Battery Guy (May 29, 2010)

45/70 said:


> Real quick, as I have to go, I read somewhere where when a NiMH cell was discharged to a point below ~0.9 Volt, that the separator was weakened. As I remember, any damage done because of this, was dependent on how long and how far below this voltage the cell was discharged. This was in reference to regular NiMH cells, not LSD.
> 
> Dave



I have never heard of this, and cannot think of a reason why it would be true. That being said, I am always learning new stuff about batteries, so I cannot exclude the possibility. If you can find the reference that you read this in, I would love to take a look at it.

While Stage 2 is certainly not healthy, the real damage to the cell occurs during Stage 3. NiMH cells are designed to have an excess negative electrode capacity to make Stage 2 sufficiently long that you are unlikely to get to Stage 3.

So the observations that Silverfox has made on the LSD cells are consistent with what one would expect from any NiMH chemistry. As long as you don't go to negative cell voltages, you should be fine.

Cheers,
Battery Guy


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## Battery Guy (May 29, 2010)

march.brown said:


> Does this mean that on a single cell torch , the battery will not be damaged by totally discharging it , whereas with a multi-cell torch it would be possible to drive one of the cells into reversal and thereby damage it ?



Yes, that is exactly what it means.



march.brown said:


> If this is so , it is a good reason to use a single cell torch in preference to a multi cell torch.



Well, you could use multiple cells in parallel. Then you never have to worry about imbalance. 

Of course, the more cells you have in series the more careful you need to be. With two cells in series, you will never get to Stage 3. With eight cells in series in a high power light, you could easily push a cell into Stage 3 discharge.

Another conclusion you might draw is that when running multiple cells in series, be sure to use high quality, well matched cells. Also, don't run your battery pack to complete depletion. In other words, use the same good battery management practices that have been recommended for years.

You should note that NiMH cells are designed to have an excess of anode capacity. This excess anode capacity provides the Stage 2 plateau, and gives you some amount of breathing room. So if you have a low capacity cell in your series string, it will be driven to Stage 2, but probably won't make it to Stage 3. The excess anode capacity is significant, typically 150% of cathode capacity. So you do have quite a bit of buffer before you do real damage.

That being said, one of the things that cell manufacturers do to get to higher cell capacity is reduce the amount of excess anode. So, in general, high capacity cells are not going to have a shorter Stage 2 plateau than low capacity cells. Some manufacturers may also reduce the amount of excess anode to save $$$.

Cheers,
Battery Guy


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## 45/70 (May 29, 2010)

Battery Guy said:


> I have never heard of this, and cannot think of a reason why it would be true. That being said, I am always learning new stuff about batteries, so I cannot exclude the possibility. If you can find the reference that you read this in, I would love to take a look at it.



Well, I think it's already a pretty well established opinion that NiMH cells are less tolerant of being deep cycled than NiCds. However, at the moment all I can find are a couple vague references from Battery University ....... here,



> [FONT=Verdana, Arial, Helvetica, sans-serif]Among battery chemistries, nickel-cadmium is least affected by repeated full discharge cycles. Several thousand charge/discharge cycles are possible. This is why nickel-cadmium performs well on power tools and two-way radios that are in constant use. nickel-metal-hydride is less durable in respect to repeated deep cycling.[/FONT]


and here,



> The NiCd battery is least affected by repeated full discharge cycles. Several thousand charge/discharge cycles can be obtained with this battery system. This is the reason why the NiCd performs well on power tools and two-way radios that are in constant use. The NiMH is more delicate with respect to repeated deep cycling.


I'll try to find reference to the actual separator weakening, but am a bit busy this weekend.

Dave


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## 45/70 (May 30, 2010)

I haven't had a lot of time to look for a better explanation of what happens to the separator when standard NiMH cells are over discharged. I did look through a GP NiMH Handbook that I have (here is a link to a newer one) and they have this to say:



> 2.4.4 Deep discharge
> The cycle life is also affected by the depth of
> discharge. The number of charge/discharge cycles
> will decrease if the battery is repeatedly subjected
> ...


I am fairly certain that weakening of the separator results from over discharging standard NiMH cells, and I will keep an eye out for a link that better explains, what actually happens. With the advent of LSD technology, which uses a more robust separator with different chemical compounds, it may very well mean that over discharging these cells has less, or possibly no effect. The jury seems to still be out on this.​ 
Dave


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## Ray_of_Light (May 30, 2010)

Battery Guy said:


> That being said, one of the things that cell manufacturers do to get to higher cell capacity is reduce the amount of excess anode. So, in general, high capacity cells are not going to have a shorter Stage 2 plateau than low capacity cells. Some manufacturers may also reduce the amount of excess anode to save $$$.
> 
> Cheers,
> Battery Guy



I can confirm.
Some cheap chinese Ni-MH I have analised had no buffer area at all.
The problem is that, in these condition, the end of charge -dV signal is pretty inexistant.

Anthony


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## TinderBox (UK) (May 30, 2010)

The Maha C9000 seems like a great charger , can somebody answer this question.

I know that the four charging bays are independent and can charge and discharge independently.

But if i am going to charge four identical battery's do i have to adjust the setting of all four bays or can i just set the first one and the other three will have the same profile.

thanks for the help.


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## Mr Happy (May 30, 2010)

You have to set all four bays individually, but in practice it is not much of an issue. The user interface is fast and easy to manage.


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## TinderBox (UK) (May 30, 2010)

Thanks for that, are their any know problems with the C9000 , I bought lacrosse BC-900 but they had a problem of overcharging and melting down so i binned it.


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## Battery Guy (May 30, 2010)

45/70 said:


> I haven't had a lot of time to look for a better explanation of what happens to the separator when standard NiMH cells are over discharged. I did look through a GP NiMH Handbook that I have (here is a link to a newer one) and they have this to say:
> 
> I am fairly certain that weakening of the separator results from over discharging standard NiMH cells, and I will keep an eye out for a link that better explains, what actually happens. With the advent of LSD technology, which uses a more robust separator with different chemical compounds, it may very well mean that over discharging these cells has less, or possibly no effect. The jury seems to still be out on this.​
> Dave



Hey Dave

Ok, you have convinced me that I need to do some cycle testing. I simply cannot understand why discharging to 0.9V would be any different than discharging to 0V. But you have put forth enough references that indicate that it does make a difference, so I think I need to put it to the test. 

Stay tuned!

Cheers,
Battery Guy


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## spencer (Jun 1, 2010)

This is a great thread. Interesting discovery.


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## Battery Guy (Jun 1, 2010)

Battery Guy said:


> Hey Dave
> 
> Ok, you have convinced me that I need to do some cycle testing. I simply cannot understand why discharging to 0.9V would be any different than discharging to 0V. But you have put forth enough references that indicate that it does make a difference, so I think I need to put it to the test.



No test results yet (sorry!), but I have been giving this some thought and I think I might have an answer. 

I have been thinking about the Ni-MH packs in the Toyota Prius and other hybrid vehicles. These have proven that they can last over 10 years without replacement. The way that Toyota and others get this kind of longevity from their Ni-MH packs is to significantly limit the state-of-charge (SOC) window that they are cycled. My understanding is that these cells are only cycled over approximately 40-60% SOC. This is important for the following reasons:

1. No gas generation because the cells are never overcharged or overdischarged into reversal
2. Minimal strain on the metal hydride alloy because the hydrogen content does not change significantly

The latter is important, because "pulverization" of the metal hydride alloy is one of the important mechanisms for capacity loss in Ni-MH alloys.

So I think this is why people generally see more cycle life from shallow cycling of Ni-MH cells. However, if you discharge repeatably down to 0.9V, I don't think that will be substantially different from repeated discharges down to 0V because the difference in capacity (and therefore hydrogen content in the metal hydride alloy) will not be significantly different.

That is my hypothesis based on the information I have been able to dig up. Hopefully I can test this in the next few weeks.

Cheers,
Battery Guy


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## Curious_character (Jun 2, 2010)

Most interesting. Do you mean that the Toyota battery is never charged above 60% or discharged below 40% of battery capacity? If so, they're only using 20% of the battery capacity, so the package is five times as large, heavy, and expensive as it would be for a complete charge/discharge cycle. Longevity is important, but that sure is a steep price to pay for it.

Do they have problems with voltage depression with such shallow discharges?

c_c


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## Battery Guy (Jun 2, 2010)

Curious_character said:


> Most interesting. Do you mean that the Toyota battery is never charged above 60% or discharged below 40% of battery capacity? If so, they're only using 20% of the battery capacity, so the package is five times as large, heavy, and expensive as it would be for a complete charge/discharge cycle. Longevity is important, but that sure is a steep price to pay for it.
> 
> Do they have problems with voltage depression with such shallow discharges?
> 
> c_c



I may be off on the SOC window slightly. It could be 30-70%, but definitely in that range.

And yes, that means that the battery is bigger than it needs to be, but the batteries in those cars are pretty small, and longevity is a huge issue with automotive hybrid batteries. The makers of EVs and extended range EVs (e.g. Chevy Volt) would never be able to get away with this because the battery pack would be huge, but for a straight hybrid the size/longevity trade-off appears to be worth it.

Interesting question on the voltage depression. One might conclude that even if the battery did have voltage depression, you would never see it because you would never discharge the battery outside of its normal operating window. Another thought would be that you don't get voltage depression because you never fully charge the cell. Quite frankly, I don't know the answer. All I know is that those NiMH batteries are incredibly reliable, and everyone I have talked to that business claims that it is because of the narrow SOC window within which the cells are cycled.

Cheers,
Battery Guy


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## InHisName (Jun 2, 2010)

Battery Guy said:


> And yes, that means that the battery is bigger than it needs to be, but the batteries in those cars are pretty small, and longevity is a huge issue with automotive hybrid batteries. . . . . .
> Cheers,
> Battery Guy


You make it sound like this car has a fuel motor and generator to charge the battery. The wheels driven by electric motors. So for example if you had a 14 hp motor driving a 5KW generator as long as you didn't drive so hard to drain the batteries too fast then it should last a few hundred miles. Hwy or city. 

Maybe it has an 'idiot' light to say - "Stop and let me catch up the charger". Like while you're at a Mall, shopping etc. I suppose if you were a lane changer and passer on highway driving then your range may be greatly reduced from factory specs.

Now to imagine what size . . . I'm thinking of 1,000 eneloops @ 2000mah x 1.3v = 2.6kwh. If you averaged 5.5kw/hr highway then it would last approx 5 hours till empty with generator running the whole time. Near me are some turnpikes at 65 limit, so thats 325 range. Hmm, kinda interesting. Betcha the battery replacement would be scary! 
At Target there are packs of four for $12.99 (I think). So, 1,000 would come to: $3,442.35. Don't forget about the fuel for the generator.


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## Battery Guy (Jun 2, 2010)

InHisName said:


> You make it sound like this car has a fuel motor and generator to charge the battery. The wheels driven by electric motors. So for example if you had a 14 hp motor driving a 5KW generator as long as you didn't drive so hard to drain the batteries too fast then it should last a few hundred miles. Hwy or city.
> 
> Maybe it has an 'idiot' light to say - "Stop and let me catch up the charger". Like while you're at a Mall, shopping etc. I suppose if you were a lane changer and passer on highway driving then your range may be greatly reduced from factory specs.
> 
> ...



I don't mean to make it sound like something it isn't. I am not a hybrid vehicle guy. All I am saying is that the way Toyota and others get 10+ years of life out of their NiMH batteries is by limiting the SOC window. More information can be found in this article. Here is a key excerpt:

_To get maximum life out of the Prius battery pack, the car's computer brain does not allow the battery to fully charge or discharge. Toyota says that for the best service life, the Prius battery likes to be kept at about a 60 percent charge. In normal operation, the system usually lets the charge level vary only 10-15 percentage points. Therefore, the battery is rarely more than 75 percent charged, or less than 45 percent charged._

Hope that helps to clarify.

Cheers,
Battery Guy


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## bob_ninja (Jun 2, 2010)

Battery Guy said:


> I may be off on the SOC window slightly. It could be 30-70%, but definitely in that range.
> 
> And yes, that means that the battery is bigger than it needs to be, but the batteries in those cars are pretty small, and longevity is a huge issue with automotive hybrid batteries. The makers of EVs and extended range EVs (e.g. Chevy Volt) would never be able to get away with this because the battery pack would be huge, but for a straight hybrid the size/longevity trade-off appears to be worth it.
> 
> ....



I believe the range is 30% to 80% yielding about half usable capacity.
For instance, Volt has 16 kWh, usable 8 kWh, about 200 Wh/mile giving range of 40 miles.

Older hybrids like Prius and Insight are similar.


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## TorchBoy (Jun 2, 2010)

Curious_character said:


> Do you mean that the Toyota battery is never charged above 60% or discharged below 40% of battery capacity? If so, they're only using 20% of the battery capacity, so the package is five times as large, heavy, and expensive as it would be for a complete charge/discharge cycle. Longevity is important, but that sure is a steep price to pay for it.


I wondered about that, but figured it was only a quirk of the English language.



Battery Guy said:


> Here is a key excerpt:
> 
> _To get maximum life out of the Prius battery pack, the car's computer brain does not allow the battery to fully charge or discharge. Toyota says that for the best service life, the Prius battery likes to be kept at about a 60 percent charge. In normal operation, the system usually lets the charge level vary only 10-15 percentage points. Therefore, the battery is rarely more than 75 percent charged, or less than 45 percent charged._


You did mean that! :huh:


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## Mr Happy (Jun 2, 2010)

TorchBoy said:


> I wondered about that, but figured it was only a quirk of the English language.
> 
> You did mean that! :huh:



This is actually not as much of a surprise as it might seem. The job of the battery in a Prius is not actually to drive the car or replace the fuel tank. That would serve only to reduce the efficiency and increase the fuel consumption compared to a normal (non-hybrid) car. It would be counter-productive.

What the battery actually does, and what gives the Prius an advantage, is to support regenerative braking and improved power management. When you slow down the excess energy is stored in the battery (like winding up a spring). When you speed up again the energy is released. The actual amount of energy stored and released in this way is not all that large, so the battery can spend most of its time hovering around 50% charge.

Another benefit is to reduce the required size of the engine. In most cars the engine is sized for acceleration from a standstill. When you are driving along at normal speed the engine is using only a fraction of its power and wasting fuel (engines are inefficient when running at low power). With a hybrid car the engine can be sized for steady driving since it can rely on temporary electric assistance to help it get up to speed from a standing start. Since smaller engines have better overall economy this helps the Prius too.


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## Lynx_Arc (Jun 2, 2010)

maybe they are using all the dud 2500mah energizers AAs that are junk and charging them at those rates they don't go bad which would make them from 1000-1500ma. I would also say it is possible that a big brick of batteries if you discharged them all at high rates and charged them up full the heat trapped in a bank would dramatically increase the more capacity you managed as the charging voltage would stay high longer generating more heat.


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## TorchBoy (Jun 2, 2010)

Mr Happy said:


> This is actually not as much of a surprise as it might seem. ...
> 
> What the battery actually does, and what gives the Prius an advantage, is to support regenerative braking and improved power management. When you slow down the excess energy is stored in the battery (like winding up a spring).


Yes, of course. They need to allow some room to store that braking energy.


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## Mr Happy (Jun 2, 2010)

Curious_character said:


> Most interesting. Do you mean that the Toyota battery is never charged above 60% or discharged below 40% of battery capacity? If so, they're only using 20% of the battery capacity, so the package is five times as large, heavy, and expensive as it would be for a complete charge/discharge cycle. Longevity is important, but that sure is a steep price to pay for it.


This is not necessarily true. You've got to think about all the variables, and capacity may not be the most important performance consideration in the design.

Suppose for instance you are working with a D-size NiMH cell that can supply 10 A while not exceeding its specifications. Suppose furthermore that you wish to augment the engine with 40 hp of electric traction. Then you would have:

(power per cell) = 1.2 V x 10 A = 12 W
(traction power) = 40 hp x 750 W/hp = 30 kW
(number of cells) = (traction power)/(power per cell) = 30 000 / 12 = 2500

Therefore your battery needs 2500 cells to meet the performance requirements. Note that capacity did not come into this calculation.


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## Mr Happy (Jun 2, 2010)

InHisName said:


> You make it sound like this car has a fuel motor and generator to charge the battery. The wheels driven by electric motors. So for example if you had a 14 hp motor driving a 5KW generator as long as you didn't drive so hard to drain the batteries too fast then it should last a few hundred miles. Hwy or city.
> 
> Maybe it has an 'idiot' light to say - "Stop and let me catch up the charger". Like while you're at a Mall, shopping etc. I suppose if you were a lane changer and passer on highway driving then your range may be greatly reduced from factory specs.



It doesn't make any sense to run the car on the electric motors like this. The car will run far more efficiently if the wheels are driven by the gasoline engine rather than the battery. If you run the car on the battery like that, all you will do is increase your fuel consumption, reduce the life of the battery, and increase your running costs from buying more fuel and paying for early battery replacement.

The purpose of a hybrid car like the Prius is to make the most efficient use of gasoline, not to replace gasoline with electricity.


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## TorchBoy (Jun 2, 2010)

Mr Happy said:


> The purpose of a hybrid car like the Prius is to make the most efficient use of gasoline, not to replace gasoline with electricity.


Does that have serious ramifications for the Californians I've read about who have converted their Priuses into plug-in hybrids? Is what they're saving in fuel - getting 100+ mpg economy - going to rebound on them when they have to buy a new battery early?


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## Mr Happy (Jun 3, 2010)

TorchBoy said:


> Does that have serious ramifications for the Californians I've read about who have converted their Priuses into plug-in hybrids? Is what they're saving in fuel - getting 100+ mpg economy - going to rebound on them when they have to buy a new battery early?


It might have ramifications if they do put too much stress on the battery and have to pay for an early replacement. But I suppose if they are only doing a very short commute each day and can charge the battery up overnight it would work out fine.


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## core (Jun 3, 2010)

Mr Happy said:


> It might have ramifications if they do put too much stress on the battery and have to pay for an early replacement.



Not to get too far off topic here (but I think it's too late for that):

Anyone know if the batteries are covered by warranty? Modifications do not have to be permanent.

And I'm also curious about how you change a fundamental behaviour of the car just by keeping the batteries charged at night. (I know nothing about them, just so you know where I'm coming from.) But if everything said in this thread is true, it would use gas when it's designed to and I don't see how a higher state of charge would change that. Do they modify the computer on the car as well?


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## Battery Guy (Jun 3, 2010)

TorchBoy said:


> Does that have serious ramifications for the Californians I've read about who have converted their Priuses into plug-in hybrids? Is what they're saving in fuel - getting 100+ mpg economy - going to rebound on them when they have to buy a new battery early?



I believe that those conversions involve replacing the rather small NiMH battery with a substantially larger bank of lithium-ion batteries. So its not like they are using a larger SOC window from the same battery.

Cheers,
Battery Guy


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## Mr Happy (Jun 3, 2010)

Battery Guy said:


> I believe that those conversions involve replacing the rather small NiMH battery with a substantially larger bank of lithium-ion batteries. So its not like they are using a larger SOC window from the same battery.


Ah, that makes sense from an electrical point of view. I don't know about the economic point of view...


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## Battery Guy (Jun 3, 2010)

Mr Happy said:


> Ah, that makes sense from an electrical point of view. I don't know about the economic point of view...



I understand that the conversions are quite expensive ($20k+), and the batteries are unlikely going to provide similar lifetimes (10+ years) that the unmodified Prius battery does. However, I think that is the price some people are willing to pay to be on the cutting edge.

There are also potential safety issues. A few of these have had fires:

http://blogs.edmunds.com/greencaradvisor/2008/06/plug-in-toyota-prius-catches-fire-explodes.html

I believe that all have been electrical fires resulting from a combination of bad connectors and high voltage.

Cheers,
Battery Guy


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## WDG (Jun 4, 2010)

Battery Guy said:


> There are also potential safety issues. A few of these have had fires: http://blogs.edmunds.com/greencaradvisor/2008/06/plug-in-toyota-prius-catches-fire-explodes.html





Ann Colcord said:


> "...we're kinda hoping things were just a fluke in that car."



Would a statement like this inspire confidence in anyone here, were they an owner or potential purchaser of one of these vehicles?

Given the theatrics we've seen some lithiums being capable of on this forum, I've been wondering what happens when one of these things goes  in someone's garage overnight, or worse, with a toddler buckled into a car seat in the back.


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## Turbo DV8 (Jun 4, 2010)

Reading that article, and the response of Ann Colcord, part owner of Hybrids Plus, the outfit that does the conversions, I am left with one word which comes to mind ... "PUTZ!" She basically blamed the driver for the car catching on fire, even though there was a prior history of charger problems in their company's conversion of that vehicle. What a dufus.


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## bob_ninja (Jun 4, 2010)

There are different companies using different types of cells. Majority of companies and all of the bigger companies that care about their reputation do not use the Lithium chemistry used in computers and cell phones that can catch fire and explode. Instead they use newer chemistry like A123 Lithium Phosphate which cannot have runaway reactions and fires, etc.

These new chemistries have been tested and are being tested for safety. They are designed to be safe even without protection circuits. So odds of fires and explosions are almost nil.

I am fairly certain that at least one of the companies selling Prius packs does use A123 cells, not sure about all of them, what type they use.

Not to mention many power tool vendors using Lithium packs these days. Consider the risks of vibrations, heat, etc. They wouldn't use Lithum based power packs if there were a significant risk of fire.


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## Mr Happy (Jun 4, 2010)

However...A123 cells have much lower volumetric capacity so if you are interested in useful range for your battery pack this is not a good option. Also, with any battery technology the opportunity for electrical fires is there, and is even greater with batteries that have a high power fast discharge capability.


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## DIWdiver (Jun 5, 2010)

TorchBoy said:


> Does that have serious ramifications for the Californians I've read about who have converted their Priuses into plug-in hybrids? Is what they're saving in fuel - getting 100+ mpg economy - going to rebound on them when they have to buy a new battery early?


 
It doesn't even matter how long the batteries last. There's a more fundamental problem with the whole discussion.

For a plug-in hybrid, MPG numbers are meaningless. With a simple modification and some stupid driving habits, I could get 1000 MPG from my 1999 Ford Ranger pickup.

Here's how I would do it:
1. Defeat the interlock that prevents the starter from engaging when the cluch is engaged (clutch pedal NOT pressed). Not all vehicles would require this modification.
2. Reset the odometer.
3. Drive far enough to use 1 gallon of gas (about 18 miles in my case).
4. Disconnect the fuel line from the engine.
5. Drive the truck around the block using only the starter motor. This may need to be done in stages to prevent overheating of the starter.
6. Recharge the battery.
7. Repeat steps 5 and 6 until the odometer reads 1000 miles.

Viola! I have driven the truck 1000 miles on only one gallon of gas!!!

Note that I could have achieved any MPG number I chose, simply by changing either the distance driven on gas or the distance driven on 'plug-in'.

Of course this is stupid, but it serves to illustrate the illogic of using "MPG" and "plug-in" in the same sentence. Anyone doing so either doesn't understand reality, or doesn't want you to!

D


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## LuxLuthor (Jun 5, 2010)

Been gone from CPF a lot, but this was a great thread & information. Thanks!


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## cckw (Jun 10, 2010)

Back to the original topic:

I have some 07 dated Duraloops that I recently bought as new. In break-in they came in around 1920. I took 2 and tried the "Silver Fox method of battery refreshing" and then break-in again, they came out 1964 and 1967. 

I discharged in a couple 1x AA lights and shorted for 48 hours.


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## 45/70 (Jun 10, 2010)

cckw said:


> Back to the original topic:
> 
> I have some 07 dated Duraloops that I recently bought as new. In break-in they came in around 1920. I took 2 and tried the "Silver Fox method of battery refreshing" and then break-in again, they came out 1964 and 1967.
> 
> I discharged in a couple 1x AA lights and shorted for 48 hours.



These results seem similar to what normally would be expected from cycling new cells. Interesting. Obviously their capacity has not been affected, but the question still remains whether their LSD capability has been reduced.

I also wonder if a potential increase in capacity might result in part, from running cells down with this "method", that had not been in use for that long a period. Large crystalline formation is known to occur during storage in standard NiMH cells. I can't help but think that LSD cells suffer from this as well, albeit to a much lesser extent due to their low self discharge rate. I would think however, that the possibility could certainly exist in cells that have been in storage for three years.

Dave


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## cckw (Jun 13, 2010)

45/70 said:


> These results seem similar to what normally would be expected from cycling new cells. Interesting. Obviously their capacity has not been affected, but the question still remains whether their LSD capability has been reduced.
> 
> I also wonder if a potential increase in capacity might result in part, from running cells down with this "method", that had not been in use for that long a period. Large crystalline formation is known to occur during storage in standard NiMH cells. I can't help but think that LSD cells suffer from this as well, albeit to a much lesser extent due to their low self discharge rate. I would think however, that the possibility could certainly exist in cells that have been in storage for three years.
> 
> Dave



I did this with 2, I can set them aside with 2 of same that I didn't do and measure the remaining charge in 6 months.


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## VidPro (Jun 13, 2010)

:twothumbs cool
will be interested in seeing any further information people arrive at about long term or continual effects of "running flat"
thanks Silverfox.

i have a singular discharger thing that was originally designed for ni-cd, and i have used it with Ni-Mhy and it has not destroyed anything *as far as i can tell*, but telling differences would require more sofistication in tracking the batts than i do.
it is 10x single battery holders with a pr2 light bulb, pretty lame but it is used to full discharge visually. i use it mostly to discharge singularly a whole big series pack (that also uses holders) so i can discharge the pack quick as singles. often i have revived the resistance and capacity of the pack using it, but what long term damage occurs ???
still it has to beat the heck out of series discharge cycling of the pack, but others have mentioned puttin in a diode to stop the discharge at more normal levels.

also there was positive results posted of discharging to .7 and .4 but no loooooonnnnng loooooonnng followup info.
problem is with looong term followup of something like an Energyser 2500 , Well you get the point 

with enloops lasting long and long and long, a long term followup or testing is possible at least.

i have enloops that were run flat and overcharge endlessly and trickle charged endlessly , and i still cant tell the abused ones from the others (the fact that i dont really know which is which  well my fault, but a few of them have marks on them i dont remember what the mark means :wave:


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## Lynx_Arc (Jun 13, 2010)

VidPro said:


> but a few of them have marks on them i dont remember what the mark means :wave:



I have learned to number cells with a sharpie and keep a text tile of the capacities. I also mark Xs on those I consider poor condition or problematic till I get around to running them through my analyzer. The X cells are used in devices that can overdischarge them or essentially are low current so the lower capacity is not a problem.


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## Lynx_Arc (Jun 15, 2010)

I am in the middle of an interesting situation. I have a few rayovac hybrids that got overdischarged, possibly reversed and capacity on them tested out running refresh in my bc900 came out to be 250ma and 500ma. for fun I took the 250ma AA and put it in a taskforce 1AA and let it drain it to nothing (probably 0.4v) and then took the battery and stuck it in an energizer 15 minute charger for an hour making sure it was cooled off before I removed it. I then ran the same battery through the bc900 refresh cycling and it came up with over 500mah capacity. I now have a second one that is about 510ma I am doing the same torture test to, I shall see if capacity improves also. I am cycling them on the lowest setting.


----------



## TakeTheActive (Jun 15, 2010)

*I Don't Understand Your Logic?!?*



Lynx_Arc said:


> ...*I have a few rayovac hybrids that got overdischarged, possibly reversed and capacity on them tested out running refresh in my bc900 came out to be 250ma and 500ma*. for fun I took the 250ma AA and put it in a taskforce 1AA and let it drain it to nothing (probably 0.4v) and then took the battery and *stuck it in an energizer 15 minute charger for an hour* making sure it was cooled off before I removed it...


I don't understand your logic:
First, what Charge Rate did you use for the BC-900 REFRESH?
- How many 'REFRESH' Cycles did it go through before 'quitting'?
.
Second, WHY would you charge it at *4.0C for ONE HOUR?!?* 
- Did the 15-Minute Charger terminate at 15 minutes and you just left it there to cool?
- Or was it CHARGING for over 15 minutes, with the fan valiantly trying to cool it?



Lynx_Arc said:


> ...*I then ran the same battery through the bc900 refresh cycling and it came up with over 500mah capacity*...



At what Charge Rate?
.
What were the Capacities of these two cells BEFORE the mishap?



Lynx_Arc said:


> ...*I now have a second one that is about 510ma I am doing the same torture test to*, I shall see if capacity improves also. I am cycling them on the lowest setting.


Rather than STRESS the poor tortured cell with 4.0C, I would have NURSED it back with 0.1C (or less) for 16 (or more) hours. It was EMPTY - seems like a good opportunity for a '*Forming Charge*', which we all know '*gets into all those nooks and crannies and stirs things up*' MUCH better than a -DeltaV or MAX Voltage termination charge. :thinking: :shrug:


----------



## Lynx_Arc (Jun 15, 2010)

*Re: I Don't Understand Your Logic?!?*



TakeTheActive said:


> I don't understand your logic:
> First, what Charge Rate did you use for the BC-900 REFRESH?
> - How many 'REFRESH' Cycles did it go through before 'quitting'?



 several cycles


> [*]Second, WHY would you charge it at *4.0C for ONE HOUR?!?*  The charger is a smart charger it shuts off when it is nearly charged (but sometimes only 80-90 percent charged)





> - Did the 15-Minute Charger terminate at 15 minutes and you just left it there to cool?


it terminated well before 15 minutes but continues to charge at a trickle rate to completion. 


> At what Charge Rate?




I used the lowest charge rate (default) on the bc900


> [*]What were the Capacities of these two cells BEFORE the mishap?



250 and 500mah


> Rather than STRESS the poor tortured cell with 4.0C, I would have NURSED it back with 0.1C (or less) for 16 (or more) hours. It was EMPTY - seems like a good opportunity for a '*Forming Charge*', which we all know '*gets into all those nooks and crannies and stirs things up*' MUCH better than a -DeltaV or MAX Voltage termination charge. :thinking: :shrug:


tried that, ran it through the refresh twice at 200ma and it wouldn't improve, a AA nimh cell with 250mah capacity is useless so I figured maybe I could shock it back into shape. I seriously doubt the capacity of the 250mah cell will ever reach close to 1000mah nor the 500mah cell reach that either.


----------



## TakeTheActive (Jun 15, 2010)

*Re: I Don't Understand Your Logic?!?*



Lynx_Arc said:


> (Ever-so-slightly re-formatted with LIST since with just QUOTE, your replies were 'running together'...
> several cycles
> .
> it terminated well before 15 minutes but continues to charge at a trickle rate to completion.
> ...


So, you just said:
Two Rayovac Hybrid AAs with an *INITIAL Capacity of 250mAh and 500mAh* accidentally "*...got overdischarged, possibly reversed...*"
You then proceeded to run several BC-900 REFRESH Cycles @ 200mA/100mA and the Capacities remained at the original 250mAh and 500mAh.
You followed that with a Taskforce 1AA Discharge to 0.4VDC, a 15-Minute Charge (for 1 hour), then another BC-900 REFRESH set @ 200mA/100mA and now the 250mAh cell is up to 500mAh.
As far as I can tell, you lost nothing, gained 100% - the cells were REALLY *CRAP* (250mAh) before your mishap and now they're 100% better (500mAH, but still *CRAP*).

Also, keep in mind that a 200mA REFRESH on a BC-900 is *NOT* the same as a 0.1C @ 16 hours 'Forming Charge' (unless 3200mAh went in  ).

I still don't understand - if the cells were at 250mAh (12.5%) and 500mAh (25%) Capacity *BEFORE* the mishap, what's the problem? Nothing much changed by your accidentally over discharging them.


----------



## Lynx_Arc (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



TakeTheActive said:


> So, you just said:
> Two Rayovac Hybrid AAs with an *INITIAL Capacity of 250mAh and 500mAh* accidentally "*...got overdischarged, possibly reversed...*"
> You then proceeded to run several BC-900 REFRESH Cycles @ 200mA/100mA and the Capacities remained at the original 250mAh and 500mAh.
> You followed that with a Taskforce 1AA Discharge to 0.4VDC, a 15-Minute Charge (for 1 hour), then another BC-900 REFRESH set @ 200mA/100mA and now the 250mAh cell is up to 500mAh.
> ...



The cells were probably close to 2000mah before the mishap, and at 2000mah 0.1C would be 200ma which is what the BC900 was refreshing them at. The 250mah one is still refreshing and is at 537ma while the 510ma one I just put in an hour or so ago is up to 359ma. I will probably shock the 250ma one again after it finishes the process to see if I can improve it more. I have tried refreshing these at 200ma and 700ma and 1000ma with no previous luck but this drain them dry and toast em seems to be doing something perhaps too little.


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## TakeTheActive (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



Lynx_Arc said:


> *The cells were probably close to 2000mah before the mishap*...


*AHA!*  So they WERE *HEALTHY and VIBRANT* *BEFORE* the mishap (that's not what you said earlier ) 

(It's EXTREMELY difficult to diagnose the problem when the patient provides you with INCORRECT symptoms! )



Lynx_Arc said:


> ...*and at 2000mah 0.1C would be 200ma which is what the BC900 was refreshing them at*...


Yes, and again, *200mA with a TERMINATION* method is *NOT* *0.1C for 16 hours TIMED*. 



Lynx_Arc said:


> ...The 250mah one is still refreshing and is at 537ma while the 510ma one I just put in an hour or so ago is up to 359ma. *I will probably shock the 250ma one again after it finishes the process to see if I can improve it more*. I have tried refreshing these at 200ma and 700ma and 1000ma with no previous luck but this drain them dry and toast em seems to be doing something perhaps too little.


IMHO, this is an EXCELLENT situation to add to *SilverFox's* "*Let's Run *One* VIBRANT Cell Flat and See What Happens*" scenario (i.e. **Two* VIBRANT Cells Turned to ABSOLUTE *CRAP* by ONE* {*I'm SO Sorry!!!* :mecry:} *Over-Discharge in Series Event*). But, somehow, based on my *CRAP* cell experience with *CYCLES* vs "*Forming Charges*", I don't see your "*SHOCK Treatment*" as the answer. :shrug:

From my point-of-view, I can see a 0.1C (or even 0.05C) *SLOW* Charge as a way to GENTLY urge the cell back into maybe a somewhat HEALTHY condition. We all know (from our *VAST* reading of the *CPF 'Batteries Included' Archives*) that FAST CHARGING will *NEVER* achieve a 100% SOC before one of the 'Termination Methods' kicks in. Whereas, SLOW CHARGING is unrestrained... :thinking: (for 16 hours at least  )

[Those of you who know me will certainly realize that my penchant for EXCESSIVE FORMATTING has been DILIGENTLY held under control for MANY weeks now. Unfortunately for *Lynx_Arc*, a certain series of events occurred this evening (now morning) forcing me to reply to posts "PAST MY BEDTIME" and thus - THE RESULT! Some of you will ENJOY it and SMILE, while others won't COMPREHEND it...  ]


----------



## Lynx_Arc (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



> From my point-of-view, I can see a 0.1C (or even 0.05C) *SLOW* Charge as a way to GENTLY urge the cell back into maybe a somewhat HEALTHY condition. We all know (from our *VAST* reading of the *CPF 'Batteries Included' Archives*) that FAST CHARGING will *NEVER* achieve a 100% SOC before one of the 'Termination Methods' kicks in. Whereas, SLOW CHARGING is unrestrained... :thinking: (for 16 hours at least  )
> 
> [Those of you who know me will certainly realize that my penchant for EXCESSIVE FORMATTING has been DILIGENTLY held under control for MANY weeks now. Unfortunately for *Lynx_Arc*, a certain series of events occurred this evening (now morning) forcing me to reply to posts "PAST MY BEDTIME" and thus - THE RESULT! Some of you will ENJOY it and SMILE, while others won't COMPREHEND it...  ]



actually it is helping.... but probably not enough. my 510ma battery is up to 552ma now and this is only the first cycle. I could wire up my power supply to a timer and run it at 50ma for 24 hours and see what happens but this is more interesting


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## TorchBoy (Jun 16, 2010)

*Re: I Don't Understand Your Logic.*



TakeTheActive said:


> IMHO, this is an EXCELLENT situation to add to SilverFox's "Let's Run *One* VIBRANT Cell Flat and See What Happens" scenario (i.e. *Two* VIBRANT Cells Turned to ABSOLUTE *CRAP* by ONE {I'm SO Sorry!!! :mecry:} Over-Discharge in Series Event). But, somehow, based on my *CRAP* cell experience with CYCLES vs "Forming Charges", I don't see your "SHOCK Treatment" as the answer. :shrug:
> ...
> [Those of you who know me will certainly realize that my penchant for EXCESSIVE FORMATTING has been DILIGENTLY held under control for MANY weeks now. Unfortunately for Lynx_Arc, a certain series of events occurred this evening (now morning) forcing me to reply to posts "PAST MY BEDTIME" and thus - THE RESULT! Some of you will ENJOY it and SMILE, while others won't COMPREHEND it...  ]


I did smile, but I also wanted to turn off the Christmas tree.  :thumbsup:


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## TakeTheActive (Jun 16, 2010)

*Re: I Don't Understand Your Logic.*



TorchBoy said:


> I did smile, but I also wanted to turn off the Christmas tree.  :thumbsup:


Every so often, just typing the *SAME OLD TEXT* without the naturally accompanying '*Vocal Modulations / Facial Expressions*' just gets so...
*BORING!*​
You can *ALWAYS* choose to IGNORE my posts. :toilet:


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## TakeTheActive (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



Lynx_Arc said:


> *The cells were probably close to 2000mah before the mishap*...





Lynx_Arc said:


> *actually it is helping.... but probably not enough*...


I dunno. For the CAPACITY to drop from ~2000mAh (~100%) to ~250mAh (~12.5%) after *ONE* mishap seems a bit extreme... 

They're YOUR cells and you're free to do whatever you like with them. Personally, I would consider 0.05C for *MANY* hours.

I'm waiting to see what one of the Gurus / Chemical Engineers has to offer...


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## TorchBoy (Jun 16, 2010)

*Re: I Don't Understand Your Logic.*



TakeTheActive said:


> You can *ALWAYS* choose to IGNORE my posts. :toilet:


I'd rather just be able to read them (easily).


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## core (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*

Lynx_Arc, I'd also put them on a timed charge for a while. They are basically useless to you so anything at all would be an improvement. Have you measured the voltage of one of them under a known load? And compare that to a healthy cell?




TakeTheActive said:


> Those of you who know me will certainly realize that my penchant for EXCESSIVE FORMATTING has been DILIGENTLY held under control for MANY weeks now.



Oh wow TTA you had me laughing even before reading your aside there. And you were doing so well for a while? Kinda had me wondering if you were suffering from colour depression lately.

Just keep repeating to yourself:

Every day, in every way, I am getting *better and better*!


----------



## 65535 (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*

Just came across this thread. A few years back when I raced RC electrics, a few guys (generally those sponsored so as long as you got the highest voltage per run you didn't care about battery life as they were replaced at your whim free ~$100 a pack).

Anyways, some of these guys swore by dead shorting their packs when done with them for the day, these were mostly 3300mAh sub-C NiMH packs at the time 6 cell.

At some point a few companies even came out with dead short trays which did just that, shorted the cells individually for storage.

And some people swore by it. That it gave a higher voltage after charge and improved the discharge curve giving more on tap power for a race.

You guys would be surprised some people were balancing NiMH racing packs long before lithium made it out of portable electronics and into the consumers hands on a large scale.


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## Lynx_Arc (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



core said:


> Lynx_Arc, I'd also put them on a timed charge for a while. They are basically useless to you so anything at all would be an improvement. Have you measured the voltage of one of them under a known load? And compare that to a healthy cell?


 I haven't done that, but put them in a 1AA task force luxeon light and it works fine for hours.


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## 45/70 (Jun 16, 2010)

*Re: I Don't Understand Your Logic?!?*



65535 said:


> ......Anyways, some of these guys swore by dead shorting their packs when done with them for the day, these were mostly 3300mAh sub-C NiMH packs at the time 6 cell......



I wasn't aware of that. Admittedly, my R/C days were a long time ago. I sorta keep an eye on the hobby from time to time though. I Know they used to do that to NiCd's, but have never heard of doing it to NiMH packs.

I was never (at the time) really into R/C cars, they were pretty new at the time (all electric). I did have a couple "Monster Trucks" though. Mine were low end and used individual AA NiCd cells in the truck and a 7.2 volt NiCd in the transmitter. This was before NiMH cells were readily available.

Dave


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## Lynx_Arc (Jun 17, 2010)

Still toasting and strangling my damaged hybrid AA cells. I have completed two refresh cycles one of them working on the third while the other is working on the second. The 250ma one on it third session is showing 749ma while the 500ma on its second cycle is showing 620ma. I have two other "good" cells refreshing at the low rate that are still working on one refresh session as it takes days when they are over 1500ma I am guessing they have gone through several cycles with one at 1973 ma taking almost a day to charge and half a day to discharge.


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## TakeTheActive (Jun 17, 2010)

Lynx_Arc said:


> *Still toasting and strangling my damaged hybrid AA cells*...


If you're interested, look back (in this thread, IIRC) for the discussion of SECOND and THIRD STAGE DISCHARGE DAMAGE (or something to that effect). As I recall, SECOND STAGE was rather large. But, it's past the time for heading out on my evening walk (sun below the tall trees, mosquitos '_still sleeping_') so I'll try to look for it later (or tomorrow or...) :thinking:


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## Lynx_Arc (Jun 17, 2010)

TakeTheActive said:


> If you're interested, look back (in this thread, IIRC) for the discussion of SECOND and THIRD STAGE DISCHARGE DAMAGE (or something to that effect). As I recall, SECOND STAGE was rather large. But, it's past the time for heading out on my evening walk (sun below the tall trees, mosquitos '_still sleeping_') so I'll try to look for it later (or tomorrow or...) :thinking:



I am almost sure these got reversed, it is interesting that the bc900 went through two refresh cycles and didn't gain any capacity but this hard exercising has the two cells that were about 250/500 ma to 650/750 now. I think I will continue draining them to about half a volt and charging them with the 15 minute charger till there is no more improvement to them. It is possible the excessive heat from the hard charging is helping to regain some capacity but I suspect that it also is damaging them at the same time. I was at first trying to drain them to zero but don't have the patience to wait days for it to happen so I just put them in an LED light that drains them to about 0.4v, then short it with a paper clip for an hour and then fry it for 15 minutes on the energizer


----------



## TakeTheActive (Jun 18, 2010)

*Re: I Don't Understand Your Logic?!?*





TorchBoy said:


> *I'd rather just be able to read them (easily).*


Well, sadly, the FIRST thing that comes to *MY* mind is that you're a rather *DULL* / "*Set-in-Your-Ways*" / *STODGY* person.  (Sorry! If you research my post history, I'm FAIRLY CERTAIN that this is the *FIRST* time that I've replied to one of *YOUR* REPEATED criticisms NEGATIVELY.)

Life is short.

IME, we get OLD **WAY* too suddenly* (one day you're feeling *GREAT*, next day you get a '*Bad Report*' from a test your doctor just had you take, shortly afterwards, you get the '*'Required Surgery', and then the follow-up 'Required Surgery',  and then the follow-up to the follow-up 'Required Surgery'*' and , *life as you knew it is no longer the same...*  You're UNEMPLOYED / You're TOO OLD / Yada, Yada, Yada... ). So, if you can find opportunities to *LAUGH and HAVE SOME FUN* '_here-and-there_' (without HURTING anyone!), *DO IT!* 

A Sig Line that I created ALMOST A DECADE AGO for some new forums that I had just joined still, IMHO, applies today:

*"Low* Post Count <> *Low* Knowledge*"* *ergo* *"High* Post Count <> *High* Knowledge*"*​
My *"**Modus Operandi**"* when arriving at a NEW FORUM is to "*LURK & READ*", possibly for MONTHS before I actually register and begin posting. From *MY* perspective, at that '_point-in-time_', I have an idea of "*Who's Who*"




/ "*Who Knows What*" :thumbsup: / and "*Who's FOS*" :thumbsdow . 

MONTHS AGO, someone with THOUSANDS of posts, challenged my knowledge with a "*I'M NOT AN IDIOT! - LOOK HOW MANY POSTS I HAVE!!*" Only a few days ago, due to his '*notable*' Sig Line, did I eventually equate



- *DING, DING, DING!* (aka "_put 2 and 2 together_") *WHO* he was, *WHEN* I previously communicated with him, and thus, out of sheer curiosity, I CLICKed on "*Find all posts by ???*" from his CPF Profile - :huh2:
Let's face it folks - you can accumulate *THOUSANDS of posts* (in a_ relatively_ SHORT amount of time) on *ANY* forum.   (Honestly, I don't even know what this *"I'd hit it" smilie* means), but, IMHO, THOUSANDS of *THE CAFÉ* or short, incomplete "SNIPE" posts don't amount to a "*Hill of Beans*" towards someone's credibility (NO intentional slander to ANY SPECIFIC INDIVIDUAL intended!).

It takes just a minute or two to post a "SNIPE" - *it could take an HOUR OR TWO to post an intelligent, complete reply*.

One thing we *ALL* know though - *I'm Different!* 

You choose to REPEATEDLY criticize my (_random / light-hearted / humorous_) EXCESSIVE FORMATING - if "*Forced into a Corner*", I choose to challenge **YOUR** CPF Contributions. 
.



core said:


> ...*Oh wow TTA you had me laughing even before reading your aside there. And you were doing so well for a while? Kinda had me wondering if you were suffering from colour depression lately*...


See!
THAT'S the kind of response I like to read!!! :thanks:  
(Although I *REALLY* didn't intend to continue, another thread from a '_poor Newbie from Brazil_' induced me to INDULGE once again... )


----------



## TorchBoy (Jun 18, 2010)

*Re: I Don't Understand Your Logic?!?*

Way-hay! Is there a flash or strobe tag you could add in there?


----------



## 65535 (Jun 18, 2010)

*Re: I Don't Understand Your Logic?!?*



45/70 said:


> I wasn't aware of that. Admittedly, my R/C days were a long time ago. I sorta keep an eye on the hobby from time to time though. I Know they used to do that to NiCd's, but have never heard of doing it to NiMH packs.
> 
> I was never (at the time) really into R/C cars, they were pretty new at the time (all electric). I did have a couple "Monster Trucks" though. Mine were low end and used individual AA NiCd cells in the truck and a 7.2 volt NiCd in the transmitter. This was before NiMH cells were readily available.
> 
> Dave



Hey Dave, lets just say circa 2005 some people were making a living off of being good at racing high end ($1-5k) RC cars. Not to mention the money put into other non car parts of racing.


----------



## 65535 (Jun 18, 2010)

Lynx_Arc said:


> I am almost sure these got reversed, it is interesting that the bc900 went through two refresh cycles and didn't gain any capacity but this hard exercising has the two cells that were about 250/500 ma to 650/750 now. I think I will continue draining them to about half a volt and charging them with the 15 minute charger till there is no more improvement to them. It is possible the excessive heat from the hard charging is helping to regain some capacity but I suspect that it also is damaging them at the same time. I was at first trying to drain them to zero but don't have the patience to wait days for it to happen so I just put them in an LED light that drains them to about 0.4v, then short it with a paper clip for an hour and then fry it for 15 minutes on the energizer




Fast charging does nothing to help a cell, it will not boost the power, it will lower capacity and damage the cell even more.

Do a 16 hour charge on a wall wart putting out about .1C then discharge at .5C and repeat a few times, might work to bring back some life. Some people have had mixed results with zapping cells. (High current low impedance capacitive discharge through the cell at maybe 80 volts and some rather large amount of current) but it wasn't designed to increase life, just increase voltage and the discharge curve. It was never conclusively proven to work 100% afaik.


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## TorchBoy (Jun 18, 2010)

65535 said:


> Fast charging does nothing to help a cell, it will not boost the power, it will lower capacity and damage the cell even more.


So you're not a car racer who believes that cells should be charged at a similar rate to what they're discharged at?


----------



## Lynx_Arc (Jun 18, 2010)

65535 said:


> Fast charging does nothing to help a cell, it will not boost the power, it will lower capacity and damage the cell even more.
> 
> Do a 16 hour charge on a wall wart putting out about .1C then discharge at .5C and repeat a few times, might work to bring back some life. Some people have had mixed results with zapping cells. (High current low impedance capacitive discharge through the cell at maybe 80 volts and some rather large amount of current) but it wasn't designed to increase life, just increase voltage and the discharge curve. It was never conclusively proven to work 100% afaik.


what is .1C? is it based upon original mah stats of 2000mah or on current 650-750mah measured? I would have to tinker and monitor a power supply for 16 hours at 65ma etc... while my charger charges at 100mah for 6-7 hours with no changes.. trickle charging heats up a battery so does the 15min charger I don't know which is worse to heat it up at 2C for 15 mins or trickle for 16 hours. I would say neither is worse than the other I chose to scorch em for fun instead of falling asleep waiting for them to slowly fry trickling


----------



## TakeTheActive (Jun 18, 2010)

*Re: I Don't Understand Your Logic?!?*



TorchBoy said:


> *Way-hay! Is there a flash or strobe tag you could add in there?*


*4569 Posts + 1 vs 728...*
IMHO, If *EVERYONE* posted such **USELESS** replies as you, they *TOO* could amass *THOUSANDS* of posts. :toilet: 
(Why don't you INVEST some of your "_otherwise WASTED_" time looking up VALID replies to Newbie posts? )
Fortunately, that's *NOT* my goal. :wave: :goodjob:  (aka *Take the Bait, Hook, Line and Sinker ...*) :sick2: )
(Thus, by your response with yet another *WONDERFULLY IN-DEPTH* reply, you simply ADDED to my 'theory' of QUANTITY vs QUALITY. BAIT + FISH = GOTCHA!)

Why won't you just allow "*Off-the-Wall* / Willing / Able / **INTELLIGENT**" folks, like me, to (at least to ATTEMPT to) *COMPLETELY* answer questions (*SOMETIMES* in an UNORTHODOX / OVERLY FORMATED - but *STILL* POLITE *AND* LOGICAL!!! - manner- *not *THAT* often*), while *DULL* / "*Set-in-Your-Ways*" / *STODGY* folks, like yourself, stick to places like *THE CAFÉ*? :huh:

IMHO, if "*PUSH-Comes-to-SHOVE*", I feel that, for the *Contributions / aka Time-and-Effort* I've devoted to this forum (*CPF 'Batteries Included'*), you need to either *STAND DOWN* *OR* "*Make a Valid Case*" ("*$H!T or Get Off the Pot*" is another "_Old-Fashioned Phrase_" that come to mind). 

*What do *YOU* have to offer?*
(I try my *DARNEDEST* to avoid confrontations and "Take the High Road", but eventually you get PUSHED *TOO* FAR and need to take a stand for your beliefs!)​
If you find an ERROR in my posts, by all means, reply and correct it. Otherwise, I think you should follow the "Golden Rule" of "*If You Have Nothing Good to Say... yada, yada, yada*"  aka "*Move Along - These Aren't The Droids You're Looking For...*" )

I'm a _mostly_ "*Stuck-in-the-House*", semi-disabled, UNEMPLOYED, "*Old Fart*" trying to still USE MY MIND, LEARN new things, and help others, while you *[email protected]#$%'s* *STILL* find pleasure in ridiculing me!
*You must be SO PROUD of yourself!*​
So what if I go overboard with FORMATING every '_now-and-then_'! From *MY* point of view, I'm *STILL* doing more good than *YOU*! :nana:

P.S. *You [email protected]#$%'s are *SO* easy to BAIT!* 

(I apologize for this OUTBURST, but, there is just so much ***CRAP*** you can take from others...  )


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## TakeTheActive (Jun 18, 2010)

65535 said:


> *Fast charging does nothing to help a cell, it will not boost the power, it will lower capacity and damage the cell even more.
> 
> Do a 16 hour charge on a wall wart putting out about .1C then discharge at .5C and repeat a few times, might work to bring back some life*...





Lynx_Arc said:


> *what is .1C? is it based upon original mah stats of 2000mah or on current 650-750mah measured?*...


Geez! 

*TWO* folks (Myself and SOMEONE **SMARTER**!) are now suggesting that you CHARGE @ 0.1C (or less!) for SEVERAL HOURS and *HOPE* that the chemicals "*realign*".

What don't you understand? 

(And folks, with THOUSANDS of posts, continue to ridicule and MAKE FUN OF me?!?)


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## SilverFox (Jun 18, 2010)

Hello Lynx Arc,

As cells age, I base the 0.1C charge rate on the previous tested capacity.

If you have cells labeled as 2500 mAh, and they test to 2200 mAh, I would set the 0.1C charge rate to 220 mA.

Your cells are CRAP and should be recycled, however, since they are testing at around 700 mAh, do a 16 hour charge at 70 mA and see if there is any improvement. If they, for example, jump up to 1000 mAh, then increase the 0.1C charge rate to 100 mA.

While there is no set rule for this, I have used this a lot and found it to be effective in that I get lots of cycles from my cells and have good mid point voltage retention.

Tom


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## Lynx_Arc (Jun 18, 2010)

TakeTheActive said:


> Geez!
> 
> *TWO* folks (Myself and SOMEONE **SMARTER**!) are now suggesting that you CHARGE @ 0.1C (or less!) for SEVERAL HOURS and *HOPE* that the chemicals "*realign*".
> 
> ...



I understand completely, this is an experiment so far of my own I started. It is working to an extent so far. I may take one of the two cells and try the 16 hour ordeal and keep going on with the current regime on the other to see which improves the most.


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## Lynx_Arc (Jun 18, 2010)

SilverFox said:


> Hello Lynx Arc,
> 
> As cells age, I base the 0.1C charge rate on the previous tested capacity.
> 
> ...


I may try that with one of the two cells but as I don't have a constant current power source it would require me to use a power supply and monitor the current and adjust it many times to compensate for increase in the cell voltage while charging which would drive down the charging current. I haven't kept good track of this experiment it was just a whim of the moment I never considered it would have any interesting results and was a little shocked to see the batteries did improve in capacity while two sets of refreshing on my bc900 did almost nothing at all (less than 10mah improvement on one cell). so far it appears this method has about doubled the capacity of the cells but as I haven't really paid attention well I cannot remember if I did 2 or 3 cycles of toasting/refreshing on both cells or not 
I bought these hybrids and never got around to running them through my lacrosse like I have all my other cells I didn't start checking them except the ones that got overdischarged. Luckily these are the batteries got with the $5 off coupons I ordered from ebay so I have about $1 in each of them and I have plenty of them plus some duraloops so toasting these doesn't make me flinch unlike those insisting I "save" them . If they had been the $2+ duraloops I probably would have tried to resurrect them.


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## 45/70 (Jun 18, 2010)

In my experience, if you're dealing with cells that are poor performers due to having a damaged separator (leaking), that you can't really charge them at a slow rate such as 0.1C. At such a slow rate, most of the current applied is turned into heat and very little is left to charge the cell. So, really all you can do is "boosh" a high rate of current in, and hope for the best. It goes without saying, that cells in this condition are recycle bin/disposal items. 

Gotta quit posting now. It's Friday, and I have much _real_ work to do!

Dave


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## Lynx_Arc (Jun 18, 2010)

45/70 said:


> In my experience, if you're dealing with cells that are poor performers due to having a damaged separator (leaking), that you can't really charge them at a slow rate such as 0.1C. At such a slow rate, most of the current applied is turned into heat and very little is left to charge the cell. So, really all you can do is "boosh" a high rate of current in, and hope for the best. It goes without saying, that cells in this condition are recycle bin/disposal items.
> 
> Gotta quit posting now. It's Friday, and I have much _real_ work to do!
> 
> Dave


 
this makes some sense to me, I think I will continue one cell on the toast/drain to 0.5v/refresh via bc900 and the other I will attempt a 16 hour trickle at about 75 ma and see what happens. My guess is the 16 hour cell will improve perhaps 5% (or maybe nothing) and the toasted one will improve 10-20% more. I expect to be surprised for sure as I wasn't expecting anything from that 15 minute energizer charger in all of this


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## Lynx_Arc (Jun 21, 2010)

Ok, I just got through taking one AA hybrid that started at 250ma and was up to 750ma and put it on a power supply for 21 hours at ~80ma, then put it on my BC900 and it came up measuring 682ma which doesn't impress me at all. The other one that was 500ma is now up to 1023ma using the energizer charger and draining them to about half a volt then running it through the refresh mode at 100/200ma.


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## fyrstormer (Jun 21, 2010)

TakeTheActive said:


> Well, sadly, the FIRST thing that comes to *MY* mind is that you're a rather *DULL* / "*Set-in-Your-Ways*" / *STODGY* person.  (Sorry! If you research my post history, I'm FAIRLY CERTAIN that this is the *FIRST* time that I've replied to one of *YOUR* REPEATED criticisms NEGATIVELY.)
> 
> Life is short.
> 
> ...


I have to admit, I kinda want to stab TakeTheActive after trying to read one of those posts. In a friendly way, of course.


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## Curious_character (Jun 22, 2010)

Lynx_Arc said:


> I may try that with one of the two cells but as I don't have a constant current power source it would require me to use a power supply and monitor the current and adjust it many times to compensate for increase in the cell voltage while charging which would drive down the charging current. . .


All you need to produce a nearly constant current is a power supply capable of producing a voltage well above the charging battery voltage, and a series resistor. The greater the difference between the power supply and battery voltages, the more constant the current, but you can get by with a surprisingly small differential since NiMH cell voltage doesn't change too dramatically during charge.

c_c


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## Lynx_Arc (Jun 22, 2010)

Curious_character said:


> All you need to produce a nearly constant current is a power supply capable of producing a voltage well above the charging battery voltage, and a series resistor. The greater the difference between the power supply and battery voltages, the more constant the current, but you can get by with a surprisingly small differential since NiMH cell voltage doesn't change too dramatically during charge.
> 
> c_c


I have a variable Micronta (Radio Shack) Power supply that is about 1.5amp 0-25vdc.
The first 3 hours it changed enough I had to adjust it about 10ma each time but after that the change over the rest of the time dropped less than 5 ma total. I was hoping for an improvement of at least 10% in capacity but instead it got 10% worse which I could conclude is basically no improvement but perhaps just staying the same +/- 10%.


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## Hitthespot (Jun 22, 2010)

Interesting read Tom. I always appreciate your tests and sharing them with us. The first thing that comes to mind is, "Well I don't have to worry about over discharging my Eneloops after all, hurray run them dead." lol---- However, one of the delima's I went through when purchasing the Eneloops the first time ( I purchased 16) was the original cost and how long they would last in the real world, or put another way how many times I could use them and charge them before throwing them away. Eneloop claims upto a thousand charges, whatever that means. I guess what I'm saying is I don't mind charging my batteries at 0% left capacity or 50% left capacity as long as I know my cells longevity will love me for it.

So my question is, what do you think over discharging the Eneloops is doing to their longevity compared to normal discharge and charging? Am I trading extra capacity on each use ( running them completely dead ) for longevity?

Thanks

Bill


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## SilverFox (Jun 22, 2010)

Hello Bill,

The recommendation still is to not over discharge cells. This is just a look at what happens if you do so accidentally.

The extra capacity also comes up with normal charging and normal discharging, it just may take a little longer to show up. Quality cells are expensive and I think you should do your best to take good care of them. However, if you push the limits a little, I wanted to show that it was not sudden death to the cells.

I have no idea of other brands will behave in a similar fashion. A whole lot of additional testing will be needed in order to get a better understanding of what is going on, but it appears that if you have a quality cell and discharge it down to 0 volts, there is a reasonable chance the cell will survive.

Tom


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## Lynx_Arc (Jun 27, 2010)

I think I have reached a plateau on my drain and toast cell rejuvination experiment. after about 5 cycles to the hybrid that started at 500ma it is up to ~1040ma and the 250ma one that was up to ~750ma that I did the long trickle charge method recommended here I only got back up to 686ma after a complete refresh cycle and another disharge/fast charge cycle followed by a refresh cycle. I have basically taken two cells that were writeoffs as uselessly low in capacity and made them useful for low drain devices by doubling and tripling their capacities by mostly torturing them into better shape 
If they were not LSD cells I probably wouldn't have bothered with them as I have several non LSD cells 1500mah and less already.


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## lyyyghtmaster (Jul 11, 2010)

Have Rayovac Hybrids gone through improvements since being released? Were there some known bad batches at first?

I purchased about 24 back then, AA and AAA. _*Without even a single exception*_, every one of them I test nowadays, whether still on its first few charge cycles from being in a little-used device or having many cycles 'under its belt', comes in UNDER 1 VOLT OPEN CIRCUIT unless it was recharged more recently than about four months prior to test!!!

By contrast, not a single Eneloop I own (of about 64) has _*ever*_ entirely failed to hold a charge, or even come remotely CLOSE to this point, going back to cells I purchased in '06 and _*have just used for the first time two weeks ago without charging first!!!*_ Granted Eneloop always has been a more expensive cell, but not by enough to make *that* much of a difference!

I have always charged all my cells on a more or less random combination of Maha C204F (balanced sets of only Eneloops used in 2-AA or 4-AA device only), C401FS, and LaCrosse BC900 at 350 and 500 mA (for AA cells, sometimes 700mA for Eneloops). I have never done forming charges with any of my LSD cells. I have only rarely done refresh/recondition/test cycles on any of these cells. I simply do not have the time to get too heavily into analyzing my batteries, but it appears with Eneloop I don't need to!

So has ROV Hybrid improved since their initial entry to market? Because from my point of view I'm seeing a cell that behaves like a normal, old-style, lower-middle-capacity NiMH relabeled as a LSD cell. oo::huh::sigh:  :sick2::green::mecry::thinking::scowl: :hairpull: /rant


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## Turbo DV8 (Jul 11, 2010)

Don't get me started on ROV Hybrid AAA cells, I have about 50 that all behave just as you said, and it's not worth the hassle to try to weed out possible good ones which will also just be garbage before long anyway. So all my AAA Hybrids are going in the trash. It's not worth trying to match crap with equivalent crap. ROV Hybrid AAA cells were not a good investment for me. The AA's I've had better luck with, but definitely getting long in the tooth, and showing signs of significant degradation, compared to Eneloops purchased at the same time and used about the same, which still march onward. My future NiMH purchases will not inlcude ROV Hybrids.


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## ALW248 (Jan 7, 2012)

Ray_of_Light said:


> check "Guideline n. 1" on Ni-CD batteries at NASA:
> 
> http://www.nasa.gov/offices/oce/llis/0644.html
> 
> This is half-true with traditional Ni-MH, and is invariant for Ni-MH LSD. As long as you don't reverse charge them, LSD batteries should report no damage from "clamped" storage. In traditional Ni-MH (not LSD) the decay of the lattice alloy continues in any case, accelerated from temperature and overcharge.



So shorting is good for NiCd. Maybe it is good in some way for NiMH, as well.

Most of my damaged NiMH have high impedance. But my Sony 2300mAh (Sanyo OEM?) developed very fast self discharge, in 2 or 3 hours. But they have very low internal resistance and output very high current. 

Maybe the internal shorting causing the fast self discharge prevented internal resistance buildup. Maybe external shorting would also keep NiMH from developing high internal resistance.


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