Batteries can be wired together to increase the amp/hour capacity. If un
controlled, they should be matched for type and age. Otherwise the battery
with the higher voltage potential will discharge to the lower state of a
weaker battery. If you really need more A/H capactiy that you may want to
consider the golf cart batteries in series route. This will give both
capacity and durability.

>From: Monsieur <obeechi@RUNBOX.COM>
>Reply-To: Monsieur <obeechi@RUNBOX.COM>
>To: vanagon@GERRY.VANAGON.COM
>Subject: 4 Batteries
>Date: Thu, 15 May 2008 22:46:46 -0700
>
>How would one set up 4 batteries in the Vanagon? I have a battery switch,
>with a type of relay between them, so one is the engine battery and one is
>the house battery. There is also an inverter that is wired only to the
>house battery. The battery switch allows for starting the engine from
>either battery.
>
>The idea of adding two more batteries to this confuses me. Would I need
>three battery switches, one two switch between the two other switches?...
>but I also want batteries three and four to run the inverter as well...