We have a Starcraft 10RT that's kept plugged in in our garage all the time when not in use. The panel gives us a maximum charge of 13.5 volts. We also have a big solar panel on top, wired directly to the batteries. When in the sun, we get up to 14.4 volts. This is with a pair of new Trojan 12V AGM batteries (didn't have enough room for 6 volts). Should the built-in charger be giving us better than a 13.5 charge?