Im working on a project involving NIMH batteries and I am looking for someone who's well seasoned with these types of batteries and the chargers. Please PM me if you've got the time for a few questions and pointers.

Thanks!

I think you should just ask the questions in the thread, then if somebody has the same questions they can find the answers they are looking for. Sort of the whole point of a forum.

Well im looking to restore some nimh batteries from a hybrid car. The batteries are grouped by six in one pack. I'm assuming that the diminished performance is due to crystallization. Ive never done as much work with nimh as with lipo and im looking for some pointers on how to recondition these cells.

Im also looking for some advice on a good nimh charger. I was looking at the older pulsar 2 and 3's but I would like something with more feedback on a screen like the tc-1030. Any input on "the best" nimh chargers out there would be well appreciated!

Any lipo charger will be a good bet I have a Hitec X1 that can Discharge at 1 amp and charge at 6 amps and can be bought around 60 bucks . Its would be smarter to buy a lipo capable charger for future use . As for the Nimh just try to cycle them and watch the temp if they stay hot for to long the solder joints can become brittle and cause a broken connection.

When I was running nimh back in the day we used to drain them really low then dead short them then blast them with 10amps backing off as temps got to high, this would usually get a weak pack back in working order. Just be forwarned that the occasional cell did blow, we did this in a small metal locker thing.

Or try cycling them like crazy, get a charger that has false peak protection, a weak packs will false peak over and over again, I remember having to restart my old charger 10-15 times to "work thru" the false peaks, again I would do this with the battery in something safe as it can cause cell failure.

How low did you drain the packs to before you dead shorted them? I'm thinking of not going lower then .8v. I'm not gonna take the chance to blast the cells with high current, I can't really take the chance with these hybrid packs. I am however expecting for one or two of these packs to be bad. Regarding the charger, do all nimh chargers have false peak detection or is this something I should look for specifically. Ill add some pics once I have the massive battery pack apart..

We would take them much lower then that, and if your not going to hit them with high current I probably wouldn't dead short them.

I'd just try cycling them over and over keeping track of how much mah your able to get in each time, if the charger is telling you it's done and you've only put in a small amount of mah and you know for sure the pack is low then just restart the charger a few times, if it doesn't work thru the false peak then discharge and try again.

Any decent nimh charger should have false peak protection but even the best chargers can be fooled by a weak pack when your trying to get it back to life, my favorite charger for this was duratrax intellipeak digital pulse charger or a mrc super brain, both should be available dirt cheap used.

I do have a tc-1030 that might work well for this and I may pickup one or two more to speed up the job... They are fairly cheap online..

Charge em all the way up, kill them, freeze em solid, then let em thaw out at room temp, and charge em back up normally....worked for me with AAs

Ive heard about dead shorting them and freezing for storage but is there a benefit to freezing them if im just gonna let them thaw out and then charge them again?

This method is highly dangerous and I strongly recommend no one try it. The method described was a successful method used on Ni-Cd NOT Ni-mh.

The nature of Ni-mh is that they DO NOT LIKE TO BE FLATTENED, it is best to charge them often and do not leave uncharged/unused for long periods.

For maximum Ni-mh battery life they should be fully charged at least once per month, do not over charge and NEVER allow to be drained to dead flat.

Well I was told it was to put more liquid into the batt, so it holds more power lol, like I said, it may only work with AAs

That's the craziest stuff I've heard.

Am I an expert on nimh, you bet! After all it's the internet, and everything on the internet is true.

expert, would never make such a foolish claim. But I have enough experience to tell you that once you get the packs "worked passed" the false peaks it may take a few cycles to get them to start taking a decent charge. As you cycle them the mah they take in will increase.

Even if you're able to bring a pack back it may still have a couple bad cells in it. You can check this by temping each cell, they should be relatively close. (can't remember if bad cells get hotter than the rest or stay cold, it's been a while) The pack may still work with one or two bad cells, but the lack of performance will be easy to see.

It's interesting you say that, I haven't been in rc long enough to have used ni-cd's so maybe the method we used was passed down from the previous generation of racers, this method was common occurrence at our track. I had learned it from the local battery matcher/builder. Dangerous, yes. Unsuccessful, hardly. While I totally agree that the best thing to do is cycle them atleast once a month and to not let them self discharge to low, I must say that the method described above was quite effective at bringing nimh's back to life and was used regularly by a handful of racers at our club.

I sure as heck don't miss those days. I think I still have my Novak single cell discharge tray in storage if anyone needs one LOL
Long Live Lithium! Haha

Dead shorting NIMH....

http://www.petitrc.com/Tech/NexusRac...HBATTERIES.htm