It would be much easier to install the 2nd battery under the driver's
seat, running the cables under the carpet between the seats.  I connected
mine in parallel with the other one, but Bentley describes a diagram with
a relay, so the second runs only the camping equipment.  With the two
batteries working together, I can forget to turn the fridge off from 12v
and still start the engine the next morning.

Mark
'85 retrowesty "Duckmobile"