Bought a Schumacher automatic pro series (computer controlled charging) and there was a sprinkle of rain that wetted the charger and it went nuts and has never been the same again. Buy a old school type charger with a regular rectifier and no circuit boards. I'm on charger #2 and just purchased a Schumacher Farm and Ranch model that looks like old school type construction/ no touch buttons or computed charging, just a plain ole charger. $119 Amazon
http://www.amazon.com/Schumacher-SE-.../dp/B00030BFO2