Hi I just purchased a 93' 14' Discovery Voyager boat, with a 35 hp Johnson. I would like to add a second Bat. for the trolling motor, and other acc. It is an electric start model, so is it safe to assume that it has a charging circuit? I am trying to figure out where to connect the wire from the centre pin on the isolater. Do I just attach it to the pos. term. on the start solenoid?