Burning Batteries!

It’s pretty normal for batteries to get hot when putting the charger one fast, but this time the battery actually began burning itself up! We’ve had the smart chargers for several months now and never had a problem with them, since they seem to be adaptable to any vex battery. For a day or two we left a 7.2V NIMH battery on the charger on safe charge. Normally the batteries, if they get hot at all, get hot when reaching their peek, but they normally don’t get any hotter. A day later when I walked into the room, I stepped on a battery that was just about as hot as a boiling pot of water: it was really hot! The battery had melted down to its the silver core and all the blue plastic was almost completely melted off. It also seared a really dark black stain into the carpet.

I’m guessing that this is a result of the charger sensor not recognizing the battery’s peek and over charging it. Am I right in assuming that the battery’s should start to cool down and stop charging once the peek is reached? How should I proceed to diagnose the problem without burning another battery? Is this a problem with the battery itself or is this a malfunctioning of the charger’s sensor? Have there been any other instances of this happening? We’ve left batteries on the charger for weeks before and they’ve never been hot for more than an hour or so, but is it save to leave batteries on the charger for a long period of time?

Mr Dinh, our team has had this happen to one of ours 7.2 NiMN 2000mAh batteries (http://www.vexrobotics.com/products/accessories/power/276-1456.html). You cannot charge these batteries with the discontinued Fast Battery Charger. If you are doing this I hope this solved your problem. Our battery actually killed itself at worlds last year in orlando, right when we needed it! However we left ours on the smart charger and it still heated up and burnt itself, strangely. Does anyone else have this problem?

Link to the official Q&A on this issue: