old AA nihms
 

I have some older AA nihms(2000 and 2300 mah) I found in the garage. They have been probably out of use for a good 3-4 years, maybe more. I am using them in my radios and I am finding 1 cell always seem to drain strait to zero with in a few minutes. So I'll take it out and place another fresh cell in and the same thing happens and keeps happening. Is there anything I can do to make these usable again?

--pakk

Get a holder from radio shack for 4 cells or two cells and charge them really slow, like 0.1 amp, then discharge them at the same. You might have to do this a couple of times. Then hit them at an amp for one charge, and discharge at 0.1 amp. Then charge them up and see what happens. You might get them to be usable again. Basically all you are trying to do is give them a good deep cycle.

ok sounds like a plan. I have a TP601c which is capable of 14 nihm cells. Would it be a bad idea to hook up 14 of them to try to get this process to go by a little faster?

--pakk

Yeah that's what I have to do with my old enegizer 2500's. with 8cells it was showing 1.3v, they are SLOWLY getting better and better. Each time they hold a higher/better charge than the last. I charge at .1amp and then use them in my radio, then charge them again at .1amp.

It's a VERY LONG process, but to me it's worth it. I guess in theory 2500mah would take 25 hours to charge at .1amp, and my Team Check Point charger has an automatic shut off if it runs too long... like 12hours or something. I'm sticking with it though.

J

Thats theoretically possible, but its not practical. When I've done that, there are cells that just don't seem to get a good charge. I'd stick to a 4 or 8 cell holder and do either 4 or 8 at once. Make sure you rotate their position in the holder from charge to charge also.

If time is an issue, buy new ones, saving these is going to take time after leaving them sit for 3-4 yrs, and you may not be successful with all of them anyway.

Like Duster said it takes a lot of time... but I kind of get my kicks taking something that's all messed up, and bringing it back to life. So to me it's worth it

Jay

Hmm...I got a bunch of these as well, that just don't seem to hold a charge anymore. I was thinking of cooking them at 3A, but a lower amperage is the trick?

Yeah if you run them at a high rate, they are just going to false peak. Slow and stead is the key! Oh yeah and time, and a ton of cycles.

Jay

I'll give that a try then. Right now I have a ton of generic alkaline batteries, and all my radios are the newer Spektrum 2.4Ghz RTR's and a DX3S, so only use 4 batteries each. The DX3S manual states I should see about 16 or so hours out of a fresh set, so I think the current draw from these newer radio systems is far less than the older setups......

Yeah the new DSM style radios dont need to put out a brute force style signal, they pick a crystal clear 2.4ghz feq, lock it out from other people and next thing you know your racing!

Jay

So maybe those cheap AA wall chargers from Wal-mart for 5$ are not such a bad idea then? :lol:

Nope I guess not. But I still like using my team checkpoint 1030 so I can monitor voltage and mah.

Jay

I am still in the process of doing this(right now the cells are charging at .1amp). My charger can also discharge and charge at .05 amp, would that be better? And once these cells are in good shape, I was just curious to what the highest amp I can charge them at was.

--pakk

Charge it at .1amp, .05amps would take FOREVER! Don't forget they have to be cycled. So you my have to do a full charge-full discharge cycle anywhere from 5-10 different times. Some times though there's no bringing a dead battery back. Good luck

Jay

Camera guys have done a lot of work with AAs and they say max charge rate for AAs is 1amp.

I have a $100 AA/AAA charger, Maha MH-C9000 WizardOne. In the skimpy instructions they outline a recovery plan for batts that have been unused for 3months or longer thats similar but diff than whats been talked about here. They have it as a canned charge routine in the charger - 0.1C charge for 16hrs followed by a 1hr rest.This is followed by a 0.2C discharge, another 1hr rest and finally another 16hr 0.1C charge. Takes 39 to 45hrs to complete.

Their advice is to do this 1 to 3 times but only if capacity increases mor ethan 10% between steps. Their adive for AAS that don't increase - discard.