Outer Limits 4x4 Board

I currently have a single battery in my GU and a Waeco Power pack which I use for camping as an external power source for lights etc. It is charged in the back of the car whilst driving via the rear power outlets.

I know have a camping/tradesman trailer which we use as our base for camping. I am going to mount the power pack in here to run a range of lights etc from.

My question is the best way to charge this power pack on the go. I'm guessing running a cable from the battery to an Anderson plug at trailer hitch and then another cable to an outlet on the trailer which I can then plug the power pack into.

What gauge wire do I need?
Do I need to run fuses both sides of the Anderson plug?
Any thing else I need to think about?

The power pack is one of these

I would run 6 b&s to the anderson, with some sort of fuse protection near the battery, near the anderson, and then inside the trailer somewhere prior to the socket.

This is the advice provided by drivesafe for running a 3rd battery in the back of my car, and also as suggested for battery in a trailer. Using the 6 b&s allows for low voltage drop, and also scope to run further accessories aswell if you wished.

Whilst acknowledging drivesafe's superior experience, I would say 6B&S (=6AWG) is the smallest I would use. Personally, I would install the largest cable I can easily find, which also meets the following criteria:

• Flexible (multi-strand, = more vibration resistant & easier to install)
  Fits the connectors I plan to use.
  I have the proper tools to terminate properly.

Remember that each battery is a voltage source, so you need a fuse at each end.

The fuse is there to protect the cable: it must handle expected currents, but blow before the cable insulation melts. Figure out your biggest load, and your most optimistic charge current (it will not be as high as your alternator rating) - this should be your minimum fuse rating. Next, determine your cable current capacity (which can be trickier than it appears) - this is your maximum fuse rating. Then try to pick a fuse value halfway between the two.