12 Volt Guru's

If you don't want it to have a voltage drop or have the fridge cut out you should run at least 5mm wire and don't forget to fuse it seperately.

Cheers
Dave

Hi Bruce

You don't need thick cables (8mm sq) to go from battery to fridge as well because fridge only draws a few amps (Typical 3amps).
My Waeco using its high speed mode is still only 6amps.

Up to half a volt total drop is ok , if extension is 8m or less then standard size
4mm sq copper cable is fine and will drop only 1/4 volt thru the entire 16m loop of cable.

If your running this extension from an existing fused socket then I would not use a fuse in it as fuses can cause more voltage drop than some cables.

You will probably have an Anderson plug connection at the tow bar/rear bumper area, I would use the thickest cable that will fit the Anderson plug to go from the Cranking battery via the isolator to the rear storage batteries.

The (FUSED) cable from the rear batteries to the fridge in the tent, will be as you say an "extension cable" because it joins the existing fridge cable connector to the battery. Maybe replace the existing fridge cable connector with a smaller Anderson plug each end of the 'extension cable' so the fridge can be used closer to the battery without the extension cable, if required.

I would use much thicker cable than recommended above because I believe you will get some voltage drop at distance, I would look at some of the voltage loss graphs to see what length cable gives zero (or close to zero) Voltage drop in the distance you are using for the extension cable (plus the original cable)

Maîneÿ . . .