Date:         Mon, 19 Feb 2007 13:18:27 -0500
Reply-To:     Troy Delnicki <colorworks@GCI.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Troy Delnicki <colorworks@GCI.NET>
Subject:      Re: your favorite 12 V accessory

>
>Hi Troy,
>
>The aux battery will not draw on the starter relay if your Vanagon is
>wired so that the two battery automatically disconnect from each other
>when charging current is not available (relay or other method). On the
>other hand, if the batteries are always connected together, their two
>voltages will be identical unless the wire connecting them is a very
>poor wire. In that case, a switch will be unnecessary.
>

Michael:

While it is true that the batteries would be isolated from one another via
a relay or solenoid, the batteries tend to equalize once the relay is
closed or power is going to both batteries. If one battery will not take a
charge because of dead cells or other reasons, it will draw power from the
good battery. The only true way for this to not happen is to get one of
the more expenses battery isolators, which are far more sophisticated
devices than the average relay or solenoid that most of us are usiing.

The term isolator is probably incorrectly used most of the time when it
comes to the relays we are using. Relays are nothing more than switches,
which are activated by a trigger wire (the blue one behind the driver seat
in this case) that then close the circuit. Again, once the circuit is
closed the batteries will act as one. The bad battery will then take the
good one with it in short order.

Troy