I would not get in a position where it needs to be "topped up" unless you boondock. If you are storing it where you have access to AC to use the maintainter while the batteries are still in the trailer, just get a dog bone to convert the RV shore power plug down to a standard 110 house plug and keep the trailer plugged in all the time, than in the warm season it is always full and being maintained by the built in converter/charger in the trailer. For winter take the batteries out of the trailer, Canadian winters will crack them and permanently damage them. Store the batteries on a maintainer in an above freezing location for the winter.