Revive dead nimh batteries

[jordan7831]

Hello everyone,

Bit of a noobish question here but I found in my parts box an old NiMh battery and was wondering if anyone had any tips to revive it. Its probably dead but just wanted to see if its possible. Why toss out a good battery right?

Its a 8.4V 1400Mah Intelect battery.

Thanks guys,

Jordan

[lurkingknight]

plenty of faqs out there to revive dead cells... most involve over volting the cell and possibly blowing them up :P

The problem is all methods invovle stripping it apart and evaluate each cell and rebuild the pack.

[jordan7831]

Thanks, a google search turned up results like that where it involves connecting the pack to a current that is way higher than the pack itself. I was wondering if anyone had any experience on here doing it.

Edit 1: So I think I am on the right track to bringing it back from the dead. I plugged it into my smart charger and it took about half an hour before enough juice trickled into it before it even recognized it as a battery. After that it charged it in about 2 minutes, which gave enough juice for about 30 shots from my G36. Plugged it in again, charged for 5 minutes, lasted about 60 shots on full auto. Each time I charge the battery, it seems to gain back more and more of its charge.

Edit 2: So ive done this about 5 times now. It takes about half an hour per charge and I can get about 300 rounds on full auto off before it dies. Getting there I guess.

[Crunchmeister]

If you read lurkingknight's reply, that's exactly what he said.

Personally, I would just get a new battery pack.

[Blackthorne]

I do it from time to time. The trick is not to hit it with allot of voltage or risk it blowing up.

Most smart chargers won't charge a battery that is completly dead. Then sense 0 volts and simply won't charge it.

I have a basic Canadian Tire 6/12 volt trickle charger. I charge the battery for about 30 seconds to a minute. Throw on some eye pro and monitor for the battery heating. If it starts geting warm take it off and toss it as it won't take any charge at all and is converting it directly to heat. They have never gotten hot in my experience using this technique.

After that initial short forced charge, the smart charger will read voltage and start charging the battery. I have kick started 5 batteries I found in a drawer that were dead for about 2 years. If it still doesn't charge, toss it. If it does you might have to condition it.. (as you are now noticing)

[supermohawk]

I am not sure if it works for NiMh, but Nicad can be revived with a arc welder. It is extremely dangerous, and not recommended, but theoreticly possible.

[jordan7831]

Thanks for the replies guys. Seems the battery is coming back to life. I have other batteries. I wanted to see if I could coax some life back into this one. No point tossing a good battery right guys

@blackthorn Thanks for the reassurance. Good to know this method works for someone else as well!

@supermohawk I read that too somewhere seems too risky for me. I've never even touched an arc welder.

[lurkingknight]

yeah, that's the most basic method, if you have a dead dead cell though, it won't ever come back.

You'll know if you charge or discharge you will get one or two cells that are warmer than the others.

[ThunderCactus]

For NiMH, once you kick start it back to life, deep cycle it 3 or 4 times to recondition the pack.
Don't hit it with high voltage, It's only doing what blackthorn is doing in a much safer way with a charger.
The arc welder method is used to clear crystal dendrite growth that causes internal shorts in cells, but crystal dendrite only forms in NiCd batteries, not NiMH.

[jordan7831]

Thanks Thunder,

Just to clarify, by deep cycle do you mean fully charge, then fully drain and then fully charge again?

[ThunderCactus]

That is correct

[jordan7831]

Worked like a charm thank you gents!

[Blackthorne]

We can rebuild him. We have the technology.