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Old 06-25-2008, 11:51 PM   #1
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Default charging NIMH Packs that sat for a year? HELP!!

I have about 7 NIMH packs that sat for a little over a year.

Any tips on charging them or getting them to take a charge??
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Old 06-26-2008, 04:30 AM   #2
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I'd say check the voltage of each cell before charging them, if there's a cell below 0.9V I wouldnt put the pack on a charger if I were you.
You can try charging if you put a temp probe on that cell.

Maybe someone else has more experience on this?
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Old 06-26-2008, 05:25 AM   #3
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I had 2 or 3 out of a lot I bought last year that were low (pack voltage 3.7-4.3), I started by charging those packs at I believe 1 amp (maybe .5), I then left it till it had like 3000 mah in it and pulled it off and put it on my discharge tray, discharged it and then fully charged it at 2amps ran it then charged normally and I never had any problems with those packs (GP3300) still use them for practice.
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Old 06-26-2008, 02:58 PM   #4
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Nothing beats a slow or trickle charge for safely charging iffy cells.

Trickle/Slow charge at 1amp or less.

If you have a adjustible discharger (I use my ICE Chrager), set the discharge rate for 1C of the cells and cut off of .9V per cell. Then equalize the cells.

Recharge the cells at 1C 5mv delta peak
Discharge at 2C, cut off .9V per cell, equalize again.

If the pack didn't get "hot" during the warmup charges it should be able to take a higher rate charge. 4~6amps. Charge the pack and let sit over night. Measure the voltage of the cells and if any are way low, consider swaping out that cell.
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Old 06-26-2008, 05:32 PM   #5
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So try to slow charge them first to get them up a bit and then discharge them to level them out and repeat..

I am working with a Trinity DPD and a Novak Millenium Pro charger soo i'm probably screwed

both very sensitive and a pain to charge even a decent fresh battery pack.. soo.. yah..
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Old 06-26-2008, 05:39 PM   #6
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When i did mine - 3300 not used for 16 months - the first few cycles were done at 1 amp - don't fully charge them - I let mine go in stages - 5 mintes then light discharge - 10amps (on Turbo 35) - then 10 minutes, and so on. Equalizing on a tray helped also.The run time was OK for practice - obviously no punch. I had 5 packs and only 1 cell that would not come back.

It was better than buying new packs for practice.

hope that helps.
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Old 06-27-2008, 02:21 PM   #7
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Thanks for the help Nikos.
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Old 06-29-2008, 09:05 AM   #8
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A slow charge and discharge is the key, I am just getting back into the hobby and have some cells that have sat for 12+ years. All have come back.

.5 amp charge rates for the first few cycles and discharges of 1a or less seemed to work for me. The old black cells seem as good as I remember but I just bought two lipo packs and two new nimh packs and battery tech has sure come a long way in a decade.
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Old 07-06-2008, 05:52 PM   #9
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So i'm trying to get some life back into a few of the packs now.

Currently charging a pack and it's showing 5.89 volts after about 10 minutes of charging. The shitty thing about the DPD discharger is it only discharges at either 5amps or 30amps.. And it's very sensitive and quick to say it won't discharge the pack..

What kind of numbers should I be looking for??

How do I know a pack is fully charged?
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Old 07-06-2008, 06:19 PM   #10
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If I check the individual cells with a volt meter and the cell shows no reading that cell is dead and can not be charged and the pack should not be used right?

Some cells are giving me a reading while some cells are giving me no reading..
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Old 07-06-2008, 06:39 PM   #11
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my Novak Millenium Pro is refusing to charge any of the packs..

So I guess that's it for them.. sucks.. thats like $600 in batteries gone..
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Old 07-07-2008, 12:41 AM   #12
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Quote:
Originally Posted by mcgmark View Post
If I check the individual cells with a volt meter and the cell shows no reading that cell is dead and can not be charged and the pack should not be used right?
not exactly... i m no expert in this NiMh battery maintenance thingy but i have been quite blessed as i managed to revive some old IB3800 and GP3300 packs..start at a low charge as recommended before and gradually increase the optimum charge rate. I never charge the batts at anything above 5 amp. I did the cycling in between with the integy reactor at 20amp discharge rate.

I dont expect the batts to perform any better than it was, its just a little comfort knowing i have at least two extra packs for bashing purposes...that NiMh thingy makes me crazy and that explains why i shifted into LiPo...problem solved.
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Old 07-07-2008, 04:34 AM   #13
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What you can do is solder the batteries apart and make new packs from the cells that do work.
If there are cells that are well above 0.9V (before you started putting extra charge in them), they will probably be ok.
Anything below that increases the chance of that cell having lost a lot of capacity, and trust me, you really dont want a cell with 1500mAh left in a pack in which the other cells are taking over 4000mAh...

If you know someone with a spintec charger, this work will be a lot easier
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Old 07-07-2008, 01:29 PM   #14
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What I don't understand is.

These packs sat for a year.. well how long do packs sit at a hobby shop for?

I just bought a stick pack so I atleast have something to run.

But I won't be surprised if this pack is dead too because it probably sat for 2+ years at this hobby shop...

What a sham...
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Old 07-07-2008, 01:36 PM   #15
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What cells were they? How much charge did they have in them when you put them away? Most hobby shops dont keep batteries on their shelves for a year.

Sucks you lost $600 in batteries but at least now you can replace all 7 packs with a lipo or two for a lot less.
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