Too many variables at this stage of the game.

First thing I'd suspect is that one or more of the cells in the pack has gone bad. Before you charge it again, you need to measure the voltage in each cell separately. Charging it again could cause it to burst into flames if there's a dead cell, and the charger is overcharging the remaining cells in the pack. Remove the shrinkwrap if you have to. The cells all have to have roughly the same voltage to a tenth of a Volt, and they all need to be above 3.0 Volts per cell.

Have you successfully flown this aircraft with these pack(s) in the past? How many flights have you gotten? What is the power system you're using? How many Amps does it draw? How agressively do you fly the aircraft?