Good going to find the problem. If you had a good charger I would suggest discharging the pack slowly down to 1 volt per cell (assuming a nicad or nimh and not lipo), then charging it slowly at trickle charge rate, or about .1 or .2 amps. Sometimes this will recondition and balance the cells and bring them back. Not always but sometimes. Could be the shorted cells are out of balance with the rest.