Go to Tower and get a VoltWatch its $10 and tests your battery under flying conditions (load) and the different colored lights show you the condition of your battery I have one either on all planes or in my flight box to check the small planes....I buy my paks from tower too except a few tiny (110Mah) batts for my 1/2a pylon racers...when Nicds start to go ie loose charge..they go fast!....Rog