[lincpimp]

I would charge them at a low rate, like .3 amp and balance at the same time. It will take a while but when the pack is fully charged, make sure it is in balance and then let it sit overnight. If one cell drops voltage quicker than the others, you have a weak cell. Not a big deal if you charge the pack then run it soon after, but always make sure your packs are in balance before you run them. You could also give it a light run (not alot of hard acell or braking and moderate speed for a few mins) then measure the voltages of the cells and see if one is lower than the others.