Another option would be to install a Trik-l-start. Three small wires and no requirement for 120vac. Mount it and forget about it. It will keep all your batteries charged when connected to shore power.
Many use a battery minder (small battery charger), but it requires that you plug it into 120vac for it to operate. No big deal if your rig is already connected to shore power, but you will have to connect, disconnect each time you travel.
Ron