If you are using NiCads make sure you cycle the batteries multiple times to insure you get the most out of your packs. It gives you an idea of how much capacity your batteries actually have. Your flight pack discharge will vary based on your servo current drain and how much you use your servos during flight ( 3D vs Pattern type flying). I also carry one of the Hobbico battery testers in my flight box to check voltage after several flights. I picked my tester up at a swap meet for $5.00! Cheap insurance.