A relay provides isolation only when the alternator is not running. In this
setup a drained aux battery will drain charge from the main battery when you
start the engine and the relay closes.

There is a solid state battery isolator that works well with Vanagons--I've
been using one for over a year now.

Mark McCulley

>From: BRENT CHRISTENSEN <bchristensen@INFOGENESIS.COM>
>Reply-To: BRENT CHRISTENSEN <bchristensen@INFOGENESIS.COM>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: Battery Under Back Seat
>Date: Mon, 3 Apr 2000 13:27:33 -0700
>
>Yes - you need to isolate the two batteries from each other, otherwise one
>will drain the other if there is even the slightest difference in voltage.
>(They will try to equalize each other).  This can have catastrophic effect
>due to the amount of current that can suddenly surge through the wiring.
>
>Traditional "battery isolators" don't work well in a Vanagon due to the
>voltage drop.  (Didn't work well in my old Jeep, either - wish I'd thought
>about the relay trick back then).  You need to separate the two batteries
>with a stout relay (I have a 75 amp relay) that is only switched on when
>the
>alternator is kicking out juice.  Then power all your accessories from your
>aux. battery by shunting to the hot side of the #3 fuse terminal.
>
>Takes a bit of crawling around and snaking wires, but well worth it.  I
>wish
>I'd been willing to give up the space under the seat for a pair of golf
>cart
>batteries!
>
>Brent Christensen
>'89 GL Syncro Westy
>Santa Barbara, CA
>
>
> > -----Original Message-----
> > From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> > Of Jay L Snyder
> > Sent: Monday, April 03, 2000 10:08 AM
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Battery Under Back Seat
> >
> >
> > I am thinking about installing a battery under the rear seat by simply
> > running a heavy wire to the starter (which would in turn
> > connect it to the
> > existing battery) and grounding to engine or chassis.  Would
> > I need fusible
> > link/fuse on this wire?  What gauge wire?  I realize this
> > will only give me
> > additional power when cranking or with ignition switch on.  This setup
> > seems too easy--am I missing something?
> >                                                         Jay
> >

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