I have a 3-way fridge, and it sucks >20 amps on DC power, which is more than the truck sends back to the camper batteries. So I’ve wondered about running a power cord from the in-cab inverter, running the fridge on 120VAC. It draws approx 300 watts AC, which is slightly more than when running on 12V, but in this case it would be leaving the camper batteries intact. Having said that, I sometimes run it on propane while driving, and sometimes pre-load it with frozen water bottles in “ice-box” mode. Because of the excessive DC draw, that’s now my last option.