Thank you all.
Boat has never had refrigeration but good block ice is getting hard to obtain and we are cruising more so it's time to add it. In typical boat project scope creap this means we need to add battery charger, 110, etc.
Plan is to add 40A or 50A battery charger to charge the existing 2 4D's and Group 31 starting battery and hot water heater when at dock. Refrigration will be powered thru the 4D's.