I gotta admit, I really didn't know this was possible, but happened to me about a week ago and I finally got around to doing something about it. In my crawlers I run 3s1p A123 packs and thought I'd cycle my packs with some runs behind my house. I charged up the first pack at 4a fine with a Lipo Dapter between it and the charger, but the second pack (the one I didn't use as much) had the charger peak and then I heard a POP. Sure enough, that one ran like crap, and I checked the voltage yesterday to see it was only at around 7v while charging. Figuring it was a dead cell, I did trial and error, and found one of the three had only .004v.......yup, dead cell. I pulled the pack apart and rebuilt it as just a 2s, so now I have a 3s and a random 2s........this sucks.