I second what Frank has to say. I had the Hella relay installed, but the
wire gauge was not up to par for my installation - if I ran the radio
and a 150 watt load on the inverter at the same time the second battery
actually drained with the relay closed, and even with the inverter off
the second battery(an optima yellowtop) never really got a full charge
it seemed. Many times I had to "help it along" by connecting them with
jumper cables.

I recently replace it with a common RV style battery solenoid
(essentially the same concept) with 10 ga. Wire and a 30 amp circuit
breaker. I'm hoping this will be better.

Cheers,
 Jeff

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
Of Frank Condelli

Sorry but here goes the  rebuttal.  This system will not work properly
with
the OPTIMA yellow top  battery choice.  The 14 gauge wire charging the
OPTIMA
does not allow  for sufficient charging on short duration trips and
eventually
you will  drain your Optima.