I am not an
Electrical Engineer but I see nobody has answered you yet. So the best way to get you some information is to post something and then somebody else will come along to correct me!
. One way of looking at it is there is not much sense wiring it larger than is already running to the original battery. That is all the juice that will flow anyway. I like to size a little large not only for the calculated amperage but for mechanical purposes. Larger wires might hold up better in a harsh (mobile) environment and their connections might be more sturdy as well. If your goal is to in effect make one large battery out of two smaller ones then the wire should be sized according to the maximum available amperage, probably something on the order of 4 gauge. Think jumper cable type size or what goes to the starter in your car. This is overkill, but that is usually where I land. In any event I would protect (fuse) these wires at the appropriate rating for their size just to prevent any unintended pyrotechnics.
Good luck.
Bigfoot
Casita
Linear Mode
