And if the mounting point is starting to get out to say around 1.5m (cable length), I am guessing thicker cable even things out? My 2nd battery is actually mounted beneath the vehicle up under the passengers side, about mid-way back. I was thinking of mounting a dc-dc charger down low on the cargo barrier behind the rear seats in the wagon to avoid water related problems.

Also, if you run 6 B&S cable through to a camper trailer with two further batteries, is there then a need for a second one of these units on the camper?