Check the voltage to see if the whole pack is bad or if you have a problem with just one cell.
On a side note, as you probably know, the higher the amperage, the faster it charges. However, by doing this, you do not "fill" the battery up all of the way. High amps causes the charger to cut off earlier than if you charged with low amps. I'm saying this just to let you know. I would charge fast too, just to get in the air sooner.
