You just don't want that to happen to anything i guess . This happened due to improper use (charged immensly wrong), but does show what can happen. I'm rebuilding my DX7 now, with help of my LHS guy; he has GIVEN me a 2000mAh NiMH and some electronics cleaning stuff to start rebuilding. And YES, i WILL charge it in the proper manor now . I'm now charging the new pack, but also in a metal case, just to be sure. Also charging on 1/20th of the capacity... Cleaned the inside of my DX7 with some kind of stuff. I cleaned out a lot of dust/ash which immediatelly smelled the same as when it just happened.