Third Battery wiring advice wanted

[TimE]

I have searched but can't find answers to my questions.

I'm looking for advice, from suitably knowledgeable people, on how to wire up a third battery in the rear of my wagon, needed for the second fridge.

Here is what I have already;

second battery (under the bonnet) is a 105ah AGM connected to the main through a "smart" isolator, I run the fridge and HF radio and inverter from this battery.

What I want to do;

run second fridge (as a freezer) off another 105 ah AGM (same model as the second battery)

From my research I think I need to run 6B&S, both + & -, cable from the second battery, with 50 amp circuit breaker at both ends, to the third battery (in a battery box in the back of the wagon).

Is this right?

Will the alternator cope? (GU IV 4.2 tdi engine)

Thanks in advance.

[the evil twin]

Wiring sounds OK in general but there are a few things to keep in mind. If you have considered them then my apols don't mean to tell you to suck eggs

-Unless you throw a CB both batteries will be sharing all the load IE the third battery won't just run the freezer
-If the 2nd and 3rd Batteries are down a fair way they will "steal" a hell of a lot of the Alternator charging capacity from the cranker
-If the 2nd and 3rd Batteries are down and the vehicle load is high (night and/or A/C fan etc) then the Alt will be right up there on it's capacity limits
-Not sure on your Fridges, Inverter size and HF useage but if they are low then shouldn't be a problem unless you camp up for extended periods IE minimal engine hours
-Everytime you come home from a trip and every month or so disconnect and charge the two Aux's seperately with a good multi-stage charger (Ctek or whatever)
-I would be tempted to run the Aux load (both fridges, Inverter, HF and anything else) via a dual battery Mini Cole Hersey switch (the ones with Off, Batt #1, Both, Batt #2) purely as a mangement measure but no biggee

[TimE]

Wiring sounds OK in general but there are a few things to keep in mind. If you have considered them then my apols don't mean to tell you to suck eggs

Mate, no need to apologise for providing good advice.

The inverter isn't used when not driving, and then only occasionally, and the HF is also only used occasionally, usually around 5 mins ever other day or so, with the motor running. As my truck isn't used as a daily driver I usually top up the batteries twice a month using a Ctek 7000, and as you suggest they are also topped up before and after every trip.

I hadn't thought about isolating the batteries with a switch, makes sense, thanks for that idea.