my buddy and i both keep our boats in storage and both have on board battery chargers. the last 3 times we have gone out and plugged in the chargers, the next time we check on the boats the gps unit has come on. i have turned mine off and then come back 1 hr later to find it on again. today i found it on, turned it off and then unplugged the charger to have it come back on again. what gives? any solutions appreciated.