Steve,
A relay from a set of driving lights rated at 40 amps is sufficient for this job
(under $15). An isolator is not necessary and wastes energy (hence the cooling
fins). To be on the safe side, add your own wire (6 gauge) for the charging
circuit. Leave the existing fridge wire and relay because you do not want to
discharge either battery with the power hungry fridge. Change over all the rest of
the camping wires to the aux battery (fusing each of course). An easy way to put
the cabin lights and radio and cig lighter on to the aux battery is to remove fuse
number 3 and run a wire from the aux battery to the fuse connector.
Larry
'86 Syncro Westfalia
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Steven X. Schwenk wrote:

> <snip>What I do not understand....and I am not addressing this question to you
> since
> you have already written so much....is i thought you could accomplish all of
> this by using the relay under the seat.  Everyone seems to say that if you
> connect the #30 post to the + aux battery terminal and to the refridgerator,
> you get the same result, including the charging of both batteries without over
> charging of either.  I understand that you believe the camper relay was not
> intended for this purpose, but was intended only to isolate the
> refridgerator. <snip>