While I have dual batts in the Patrol, the secondary is a 105AH deep cycle, I now have a 75Ltr Combi Engel and when we go camping I don't want it connected to the car if we go out 4wheeling. So a third battery in a box I think is needed. So. The fridge maximum current draw is 4.2amps. How do I work out what the best sized battery would be to buy to run this for atleast three days. Mind you I do have a solar panel setup too...
Plus what an AGM battery? I had in mind to just buy another deep cycle. D70ZZ.

Cheers.