It depends on what you need the "house" battery to do, but there's no reason you couldn't use a separate charge circuit to it that's isolated thru a relay unless the ignition is on. The house battery wouldn't be available for jump starting with that arrangement, though. My Diesel has dual batteries that should be matched as they're just connected in parallel for more starting power. It also has a Trailer battery charge relay that goes to the camper connector in the bed to charge the camper battery, and to the trailer connector. I don't use the battery charge circuit at the trailer connector, but it's there if I ever wanted to pull a trailer with a house battery.
