I just purchased 2 new interstate batteries. One starting, and one deep cycle. My Perko switch is marked: Bat 1, Bat 2, Both, and off. My question is this: When starting the boat, does it hurt anything if I select Both on the switch, and then just leave it there to charge both batteries? or should I use only the starting battery, and then move the switch to Both? This may be a dumb question, but I just don't know.