Cell Recovery

[Wolf Lonesome]

Hello Everyone!
I've been reading the forum posts regarding especially
cell recovery methods. No matter what charge rate I use there
are constant misterminations. BTW, The C9000 refuses to charge these
really crappy cells.
Here's the method I have tried, but with no luck at all

http://www.candlepowerforums.com/vb/...age-depression

I have a couple of questions for Mr. Tom (SilverFox)
as he is the most experienced man in the field of cell recovery.
My statement comes from reading his posts in this forum.
1. What charger I should use after finishing the ChrisA method
2. What charging rate should be set for these really bad cells.
3. Maybe these batteries should have been recycled long time ago :)

Here are the chargers have:

La Crosse BC-700
Accupower IQ-328
Maha C-9000
Maha MH-C808M
and last but not least Schulze Charger

So, Tom please just let me know how to handle
these cells

 

[SilverFox]

Hello Wolf Lonesome,

Welcome to CPF.

If your need for the cells is urgent - recycle them and pick up some new cells to use.

If you want to play...

Put a cell into the BC-700 and discharge it at the lowest rate you can and then note the capacity. Then hook it up to the Schulze charger and select the 0.1C charge rate and let it go for a few days. Check and note the voltage every 12 hours. You are looking for a gentle rise in voltage. When the voltage stabilizes watch for a slight drop in voltage. When that happens the cell should be as fully charged as it can be. Repeat the discharge test and see if there is improvement.

The tread you referred to was from 2006. At that time I was thinking that NiMh chemistry followed NiCd chemistry with crystal formation causing voltage depression. I now no longer think that crystals are formed but there is something that happens within the chemistry inside the cell that can sometimes be reversed by gentle discharging and 0.1C charging cycles. The concepts are the same but I think the crystals are only formed in NiCd cells.

When you finish playing you should recycle the cells and put your efforts into keeping your new cells vibrant. I find that much more rewarding than spending weeks trying to revive a marginal cell.

Good luck. :)

Tom

 

[Wolf Lonesome]

Yes, I want to play :).
But charging for a few days??? It's a time consuming task.
Actually, I started last night after reading your post, Tom.
Well, after 12 hours the Ni-Mh cell voltage seems to be steady
around 1.78 ~ 1.79.

I do have a bunch of Eneloops and Duraloops.
No urgent need for fresh cells.
This is basicaly a test "if the crappy cells recovery can be done".
Let me ask you again - should I disregard the ChrisA method?
Also, I have a couple of smal 1.5V 50mA lamps.

http://www.thesource.ca/estore/prod...catalog=Online&category=Lamps&product=2720168

I use them as dischargers, when the light dies out, I try
again to charge a crappy cell by Accupower IQ-328 at 700 mA.
Thanks for your input, Tom.
I do really appreciate it :).
Peter

 

[SilverFox]

Hello Peter,

The reason more work isn't done on this is because it is very time consuming and has very few successes. Still some interesting observations can be made. At very low discharge rates you can see the voltage move around somewhat. This seems to be caused by the damage done to the chemistry and/or electrodes within the cell.

When working on a perceived impossible task I would leave any stone unturned. Use any method you can and make up some new ones. I don't think Chris had much success but maybe a twist on it may work better. The first step is to demonstrate improvement and then you need to find a way to minimize the amount of time you have to spend on it. At one time I thought a charger could have a "recovery" program built in. It would tie up the charger for a few weeks, but if it worked it would have some value. The Maha C9000 has the Break-In function and that comes close but to overcome high internal resistance needs more than just charging at a low rate.

Tom

 

[Wolf Lonesome]

It has been great improvement with that cell.
My crappy cells are just regular Duracell's made in Japan.
They are about 8 years old
Actually I'd lost my patience and terminated the charge after 26 hours.
The BC-700 reported 960 mAh after discharging @ 100mA
The Schulze charger is doing a non-timed, non-termination charge.
Let me ask you a question about an antique Ni-Cad AA charger.
Can use it for these slow charges because of its low charge current?
This old charger has two charging options.
I can put 4 cells and charge them @ 45mA (normal) or 150mA (quick).
I remember reading a thred that you successfully restored a couple
bad cells after 50 charge/discharge cycles.
So, Tom you are not longer support those deep discharge techniques,
described here by TTA (incandescent flashlight, SEARS solar LED lamp etc.).

 

[SilverFox]

Hello Peter,

Your old NiCd charger will work fine but keep in mind that many of those older chargers had a maximum time amount when using the "quick" charge.

It is not a matter of being for or against deep discharging and all that goes into trying to recover marginal cells. The real question is how many resources are you going to use trying to recover a $4 cell? And once recovered how well will that recovered cell work?

I think it is better to spend these resources maintaining cells so they have a longer maximum lifespan.

However, I also think it is important to go through the process of trying to recover old cells a few times. This process helps in identifying what is really old and what is just marginal and can be restored. There is also the possibility that someone may come up with the combination that will actually result in improved performance.

I happen to think that a deep discharge has a good possibility of being part of that process, but buy itself it does not work very well. With marginal cells it does help but the key is to find a way to reduce the cells internal resistance once it has creeped up.

Tom

 

[Wolf Lonesome]

Hi Tom!

Well, how to reduce the cells high internal resistance?
That's a very interesting question :).

The old Minwa charger (25 years old or so) says on the back panel.
7-8 hours at 150mA (quick)
16 hours at 45mA (normal)

Do you think I can do a quick charge and after 8 hour just flip the switch to normal
for 16 hours (a sort of "top off" charge).

Also, I have a Garrison 1AA LED flashlight, so I can run a crappy cell,
after the BC-700 finishes discharge.

I can use the ChrisA method and start a charge on this old Minwa thing.
I will NOT give up so easily trying to bring these bad cells back to life.

Have tried to let's say recover a bad cell using your Schulze charger?
Do you charge your Eneloop's with Schulze as well?

Thanks again, Tom.

Peter

 

[Alex E]

Well here's what I did and this was shooting from the hip... Zapped each AA with a 12 V charger which I use with my SLA 6 v/12 v batteries I put in my deer feeders. Maybe a few quick zaps then 5 seconds to top it off. At that point I was able to place the batteries which previously would not register anything into my smart charger and they charged right up. I'm sure this is destructive for the batteries but these 20 or so rechargeables wouldn't charge at all and had only been recharged a few times but the last round they sat in game cameras out on my ranch and they were deeply discharged. Usually I swap them out every month or so for recharging.

 

[SilverFox]

Hello Peter,

You will have to "play" with your charger to see if flipping the switch starts a new charge or goes on to top off the charge.

The Schulze allows for some "interesting" experiments and yes I have had some success in recovery. I mostly use the Schulze for battery packs but it works well for Eneloop cells.

I still think the key is to find a way to reduce the internal resistance.

Tom

 

[SilverFox]

Hello Alex E,

We used to do that with NiCd cells all the time and it worked well. However NiMh doesn't seem to handle the abuse as well. You get some recovery but it quickly falls off and you are back to where you started. Still, it is worth a try but be careful.

Tom