Below is what can happen when you over charge a pack of batteries. Sounds like a shot gun going off. Fire and burning parts every where, the end of cell can blow off... this can blind you, distort your vision, mane you, burn all your hair off your head, blow off your fingers and could even kill you!

DON'T EVER CHARGE A PACK WITHOUT BEING THERE. (WATCHING THE TEMP).
DON'T OVER CHARGE. NEVER OVER 10 MV DELTA PEAK (THRESHOLD) PER CELL.
NEVER CHARGE OVER 6 AMP.
NEVER CHARGE OVER 120 DEG TEMP.
NEVER USE A METAL BATTERY HOLD DOWN AS THEY HAVE BEEN KNOWN TO SHORT OUT BATTERY PACKS.
ALWAYS WATCH THE TEMPERATURE OF BATTERY AND CHARGER.
NEVER CHARGE ON A METAL SURFACE THAT CAN SHORT OUT CELLS.
THESE BATTERY ARE POWERFUL AND BY NOT BEING CAREFUL YOU CAN AND WILL HURT YOURSELF OR SOMEONE YOU LOVE.

MIKE