A blatant plug here for completing your profile and adding a signature like with your camper's make and model
In the Georgetown, battery charging is handled by a device called the Battery Control Center (BCC). It allows any source of charging current to charge BOTH the storage (house) and starting (engine) batteries while preventing one from discharging the other.
There are a few resettable fuses and a relay (that ties the two together if the engine battery is dead and the house battery is not) that you should look at.
Here is what one looks like schematically; some info on the BCC, and a schematic of a "generic" Georgetown:
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW