I am using 3s 2100 thunder power li-polys and am getting flight times of 12 to 20 minutes depending on throttle. Except one pack is now lasting maybe 5 minutes. It charges fine and after power drops off (about 5 minutes) and landing the battery still reads 11.6 volts but not enough power to fly. Is this what happens to polys? Could it be from over drawing the pack? I did bump the gear shaft and didn't notice it was binding one time until I landed and flipped the prop. Thanks for any reply