Willy,

Have to chime in on this.  I think Doug is correct; 2 batteries connected in
parallel through a very low resistance is not a good thing - hard to predict
what will happen, long term.  You can't guarantee identical conditions, much
less identical batteries.   For a temporary connection, ok.  But much better
through an isolator or some other impedance.  Do remember that sparks around
a charging battery are potentially a *very* bad thing (hydrogen as in
Hindenberg).  //Jack

Date sent:              Mon, 7 Jun 2004 17:43:56 -0700
Send reply to:          Doug in Calif <vanagon@ASTOUND.NET>
From:                   Doug in Calif <vanagon@ASTOUND.NET>
Subject:                Re: Dual-Battery Question
To:                     vanagon@GERRY.VANAGON.COM

> Fin,
> I have found the two batteries will fight on another and deteriorate.
>
> Any un equal difference will constantly pull on one and push the other to
> hold more which eventually made them both go bad prematurely..
>
> Doug
>
>
>   ----- Original Message -----
>   From: Fin Beven
>   To: vanagon@GERRY.VANAGON.COM
>   Sent: Monday, June 07, 2004 5:14 PM
>   Subject: Re: Dual-Battery Question
>
>
>   For years I have linked my two (identical) batteries with a solid run of 4
>   ga. wire, with crimped-on terminals at both ends.  This effectively turns
>   the two batteries into one LARGE battery.  What's critically important is
>   to use VERY high quality wire and terminals.  If you have access to marine
>   grade (West Marine on the Internet) I think that it's worth the price, as
>   they assume that their equipment will be used in a very harsh electronic
>   environment (salt air).
>
>   This is not a recommendation, but no problems have resulted.  However, I do
>   have a good quality volt-meter that can be left on when the batteries are
>   being used but the engine charging system is not (as when camped
>   overnight).  I'm just cautious not to let the voltage drop below 11.8 in
>   moderate weather.
>
>   Fin Beven
>   '90 Carat, Custom Camper Conversion
>   Pasadena, CA
>     ----- Original Message -----
>     From: Joe Federici
>     To: vanagon@GERRY.VANAGON.COM
>     Sent: Monday, June 07, 2004 11:10 AM
>     Subject: Re: Dual-Battery Question
>
>
>     I wouldn't consider it safe but to each his own. That said if your
>     going to do it I would use as large around 6 gauge or better and fuse it
>     for sure it won't take much to over charge the battery and really BAD
>     stuff can happen one you reach that point.
>
>       The isolator or relay setup isn't that had to do maybe you could take
>     it with you and hook it up on vacation?
>
>     JFF
>
>
>     On Jun 7, 2004, at 1:38 PM, Russell, William wrote:
>
>     Well, after a weekend of work, I've managed to get my Optima Yellow top
>     installed and the stereo switched over to it.  However, I have not yet
>     installed a relay or isolator yet.  What I would like to do, for this
>     trip (I leave tomorrow), is employ a manual system.  It would seem to me
>     that hooking a wire from the + of the starter batter to the + of the
>     Optima while the car is running would work.  I would like to use
>     something a little more graceful than a jumper cable as I will be living
>     in the van for the next week.  If I were to route a wire between the two
>     batter compartments and use alligator clips to connect it, would this be
>     safe?  What gauge of wire should I use?  Should it be fused?
>
>
>
>     Any help is much appreciated.
>
>
>
>     \/\/i!!y
>
>     1980 Westfalia "Jazzy"