Robert, I just did this two times for customer although we put the
battery under the driver's seat.  I would recommend doing that, using
the Go Westy 2nd battery kit, and some of these wheel chair batteries
that I get off of amazon.com.  The part number is UB12220 and they are
22 amp hour batteries.  I usually connect 3 of them in parallel to get
66 amp hours for around $150 worth of batteries and shipping.  Much
better deal than buying the Go Westy battery for around the same price
(not including shipping) and only 44 amp hours.  The Go Westy kit tells
you step by step how to hook up the wiring with pictures.  Super easy.

I actually did a video of my last install, I just have to edit it and
upload it to youtube.  If you want to subscribe to my channel there you
will get an email when it is ready to go.

--
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: 856-327-4936
Fax: 856-327-2242

On 4/19/2012 11:29 AM, Robert Clemmer wrote:
> I'm going to install an auxiliary battery under my rear seat in my 91
> Vanagon to power my refrigerator and other appliances without killing the
> service battery.  Any suggestions on where I can tap into for a trigger wire
> that will power the solenoid that will connect the aux. battery to the
> charging circuit only when the engine is running.
>
>
>
> Bob C
>