Bringing Ni-MH cells back to life

[THEYTOOKMYTHUMB]

Anyone know any secrets? I got a couple of old Tenergy packs that seemed to take a charge fine, but ran like they were dead. They might be shot, but before writing them off I figured I'd ask around. I figured I would try cycling them a couple of times to see if they show any signs of life. I don't have any fancy equipment to check them on. I use an EOS0606i which might be able to give me a little info. Anyone have any suggestions?

[Charlie don't surf]

If they were not cycled regularly ( 2-4 times per mo) the only was to bring em back is voodo--but don't forget to recycle (no pun intended) them properly

[THEYTOOKMYTHUMB]

If they were not cycled regularly ( 2-4 times per mo) the only was to bring em back is voodo--but don't forget to recycle (no pun intended) them properly

I think they're off to the recycler. I already tried a traditional voodoo dance and sacrificed a chicken. ...well actually I just thought about my problem while eating a bucket of KFC. It was the best I could do with my resources...

[Charlie don't surf]

If they were not cycled regularly ( 2-4 times per mo) the only was to bring em back is voodo--but don't forget to recycle (no pun intended) them properly

I think they're off to the recycler. I already tried a traditional voodoo dance and sacrificed a chicken. ...well actually I just thought about my problem while eating a bucket of KFC. It was the best I could do with my resources...

[SteveK]

Try peaking and discharging them at 15-20 amps a few times, see if that helps. It works for NiCads that are even several years old. I do this to new packs before I use them to 'train' them to put out max amperage at a consistent rate, kind of like running wind sprints.

[Jay Dub]

NiMh cells are very finicky. Every type of cell, from every manufacturer, from every individual batch can require specific care and storage processes. Like Charlie said, if they weren't kept cycled and at a relative state of charge while being stored, than they are propably junk. One of the biggest issues (and least well known) is in their discharging, or more correctly overdischarging. I have seen/done my self brand new packs ruined because they were discharged too far. Typically this is somewhere between .8 and .9 volts per cell. This is on an individual cell basis. Over discharge a single cell in a pack, and it usually will suffer irreversable damage. This is easy to do, and is usually done by running a pack until it begins to dump, or worse until it slows to a crawl. Once this has occured the damage has been done and nothing can reverse the problem. From what I have been told, the plates in the cell begin to get holes and oxides around the holes, and this effects its internal resistance, voltage and capacity (all in a bad way). And this can happen on the very first run! . I have been experimenting with old packs , and have found nothing significant to help bring the packs back to life. Individual cell discharging and cycling, storing cells fully charged, trickle charging. The weirdest thing I have found is how inconsistent the packs get with age. Some cycles are great, followed by horrible false peaking, and or discharge cycles. Do yourself a favor and dump the packs, and invest in some reputable LiPo's. If you do want to continue to use NiMh's, never discharge them any more than necessary (eg, a 5 min race or qualifier), cycle them every 2 to 4 weeks, and always put a 1000 Mh charge in them for storage, for every week they will sit (some need more) e.g. 3 weeks between cycles = 3000 Mh of charge for storage. Also most of these cells need several days between cycle to fully recover ( I don't know why) and they should be trayed/cells balanced at least every other cycle. PS Lipo's don't need any of this BS. -Jeff

[THEYTOOKMYTHUMB]

Thanks for the tips all. I have plenty of batteries, mostly Lipo and Nicad. I only have about 3 working nimh packs. I got a couple of extra nimh packs in an ebay purchase. I obviously know why they were thrown in extra. No biggie if they work or not, but you can never have too many batteries in my opinion. My Lipos will probably go bad from lack of use. Especially the 3s. It's just too much power to be fun. Might sound impossible, but after a few moments of thrills I prefer a stock brushed motor and a simple 7.2 volt battery for cruising around. Just for the hell of it I'll try to breathe life back into them. I had a few 1200mah nicads that had to have been in a tote in the basement for 15 years and they actually took a charge and ran pretty well. Run times suck, but as far as punch they were like new. I wouldn't mind having a few more nimh, but Lipo is getting just as cheap. I follow all the storage rules for my Lipos, but I have to be killing them. At least they'll be cheap to replace.