Mark, you are absolutely correct. I don't know what I was thinking of.  Larry

> <snip>>The wire size depends upon the continuous current that will be drawn (the
> >bigger the safer). Add up all of your 12v service requirements and select the
> >appropriate wire. Add a fuse to protect your van and family.
> >
> The size of the wire between the aux and main batteries (through the cutoff
> relay) is not based on the load on the aux battery. It's based on the
> maximum charging current that you can expect from the alternator.<snip>