All modern cars, trucks, buses, and yes, motor homes, have parasitical draws on the starting batteries like clock, radio presets, and finally all power train control modules to keep memory intact. As such, you need to charge the chassis ( starting battery) battery from time to time. You can do this easily with a solar charger or you can run an extension cord to a battery tender dedicated to tour chassis battery but, if you are going to run an extension cord, why not just plug your whole coach in.
Solar is easy, quiet, and no more pesky extension cords or, in my case, huge 4 wire 6 gauge wire cables powering the whole coach.
-Paul R. Haller-