You say "It seems to need a recharge after 2 flights". On what basis are you making this statement? You should be checking the battery pack with a loaded voltmeter. If it reads 4.4 volts (for a 4-cell pack) then you are definitley done flying until you recharge. If the loaded voltmeter reads 4.8 volts, then the pack could still have a lot of energy left in it. As RCKen said, you need to check the battery with a cycler. The general procedure is like this: Charge fully and fly perhaps two timed flights. put the pack on a cycler to measure how much was left. with this information, you know how much longer you can fly the next time.