the battery in the lfight box is a lead acid battery, that means it is rechargable. the carburator should have been closed or plugged when he put it up there. if it isn't, you should take the engine apart and clean it wth rubbing alcohol. on it's first run, run a tank of 5% nitro, 20% oil through it to clear out whatever, and get the engine back in shape. however, yes, all flight batteries should be replaced. if one goes bad, you will loose the plane. i know it was only $50, but there is an emotional factor involved