I was involved in early testing of A123's with Fromeco... we intentionally overcharged them until they gassed, but I was never able to make one do anything other than gas out.. then it failed completely.. that happened around 4.5 volts... Its a strong very noticeable acrid smell, and it got very hot.. The next morning it was dead..

I feel pretty safe with the A123s from that perspective... I also picked up a pack out of a burning wreckage a year back and they were intact.