use a switch to switch the gauge between batteries.

when running, if they are joined so they both are getting  charged ...
then you couldn't read just one, unless you cleverly use diodes in the
circuitry.

Scott

----- Original Message -----
From: "Michael Sullivan" <sandwichhead@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, April 14, 2010 3:42 PM
Subject: VoltMinder-Is it a good thing?

> Since I am putting in the aux battery, a VoltMinder was suggested.  any
> reviews on this?  How can I hook it up to monitor both batteries?  Thnaks
> to
> all.
> Michael in San Antonio
> 91GL Weekender AT 2.1L 'Gringo'
> 73 Beetle