Very true about getting a field charger, I always carry my triton JR charger, it will cycle, charge and discharge my batteries and record all the info. I also carry a medusa research meter in my box, it's small and shows realtime draw and voltage on the pack, it can tell me if a single servo is binding or not by moving the surface and watching the current draw. I originally bought it for my electric heli's, but I don't fly them anymore, so I adapted it for my flight packs. The only real way to test your packs is charge them with a accurate charger that records total MAH and discharge them at the same rate. it should be very close to the same time on charge and discharge, as far as the plane goes, a voltwatch is a pretty good tool to have onboard, it's simple and lets you know how everything is doing.