After adding a 190w panel to the roof and a Victron 75/15 smartsolar MPPT to specifically charge the Aux battery, I added a 2nd voltage sensing relay to help maintain the cranking battery when the patrol is parked in the sun for long periods.

So both batteries will connect to the other when their voltage is over 13.3v & disconnect when under 12.8v.

I'm in the process of running 8mm2 cable to the fridge to help minimize voltage drop when compressor is on.

I like it, all I need now is a decent aux battery