That's handled by the power control center, it automatically selects what source to use, When on shore power or the genset, the house battery is charged from those sources. The coach battery is only charged from the alternator, which is why you need a float charger on the coach battery even if stored and plugged in.
When driving both the house battery and the coach battery are charged from the alternator, unless the genset is running. At least thats how it works on our unit.
Dear Wife and me, in our
2016 Jayco 26XD
5 fur babies