Installing a starting battery would be a bad idea - they are not meant to be
used infrequently.  They will become unable to hold a charge fairly quickly.

I installed a couple of wheelchair batteries which cost me about $70 total,
IIRC.   Here is one of my posts from the Vanagon List about it:
http://gerry.vanagon.com/cgi-bin/wa.exe?A2=ind9907A&L=vanagon&P=R7340

Brent Christensen

----- Original Message -----
From: "Royston, Jerry" <gmr@OBPA.USDA.GOV>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, June 13, 2002 10:27 AM
Subject: Simple auxillary battery question

> Here's my dilemma.  I will be installing a 2nd battery next week in my
> camper and still can't get myself to spend $160 on an Optima.  All I want
to
> do is wire my power converter to it and be able to watch a 2 hour movie in
> the middle of nowhere on my 13" TV/VCR combo (rated at about 65 watts) and
> maybe run a small light or fan for a while.  And I don't plan to live in
the
> van for extended periods so this would be only a once in a while need.
What
> I need to know is whether a regular starting battery would suffice and how
> long would it last.  Are there cheaper deep cycle batteries that would fit
> under the driver's seat?  If a regular battery is all I need, is there one
> particular kind/model/power rating that I should look for.  Thanks.
>
> Gerry Royston
> '87 Westy
>