When I installed my new 3 way fridge I added a 30 amp fuse directly off the TV battery
. From there I ran #10 wire ( pos & neg )back to the taillight area in the TV. There I addad a 30 amp relay in the circuit. This relay coil is connected to the running lights
of the TV. From there the wire goes through a new 7 way connector to the fridge in the trailer.
No other 12 volt scource is connected to the circuit as you never want to run the fridge off the egg battery
as it will run it down quickly.
When travelling, the fridge only runs off the van when the lights
are on thereby assuring that the TV battery
is never left connected inadvertently. Still, I always unplug the egg when setting up just in case.
When getting ready I run the frig off the 115 ac for a full day taking care to first add something of voume inside. I also freeze anything I can in the home frig and add this to the camper frig immediately before departure. With this method, my frozen food is still mostly frozen two days after departing.