I added a house bat to the port locker just aft of the bat box. It is in it's own plastic box secured to the wooden bulkhead and wired directly to the 2 other house bats. I have a third system in it's own box under the seat/ berth at the nav table. It is switched directly to the power panel and fused. It is not wired for starting but will run everything else. I charge it but switching it on and read it's charge rate on the ships ammeter.