Thanks for all this info guys, as this is something i have had a prob with also. Like Nek said, The battery compartment in my boat is a pain in the shorts to get into and i'm in the market for an onboard charger. I have 2 batts on my boat, 1 just runs the trolling motor and the other runs everything else and the big motor charges the one one while running. So, if i get an onbaord charger do i really need one that will charge both batteries? or just one for the troller? Also what size and where is a good place to get one and how much do they run? I asked about one at the boat dealer and he told me it would cost between 3 and 400 bucks which seems ridiculous to me!! Any thoughts on this would be appriciated.