I leave batteries plugged in all the time in all my planes and cars. Does yours have a true on/off switch? My dad's skyfly just plugs in and has no switch, so it may be off but the system is actually on. Is it a lipo battery, maybe its just a wierd lipo thing. I have left all my nicad and nimh reciever batteries plugged in for long periods of non use and they still have lots of power. I would try to return the battery or something, horizon hobby is supposed to have one of the best customer services.