There is an adjustable voltage regulator available for the Bosch
alternator.  Unfortunately, the page with the specifics is no longer on
line....

On Thu, Jun 12, 2008 at 9:54 PM, Stuart MacMillan <macgroup@comcast.net>
wrote:

> Yes, it's a problem due to higher internal resistance of the AGM and Gel
> design.  Marine alternators are set to the proper 14.4 volts needed for AGM
> charging, and are much more robust compared to car alternators.  I'll have
> to do more research on car alternators to see if there is any way to get
> the
> 14.4 needed.  But maybe just another specific charger is the simplest way
> to
> deal with this.
>
> Stuart
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Philip Zimmerman
> Sent: Thursday, June 12, 2008 9:15 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Why AGM batts don't last as long as they should
>
> Good to hear your report of this confirmation Stuart!
> Anytime I hear of a Vanagon with a dead AGM or two, I'm curious to know
> what is the charging voltage at the battery terminals? If anything less
> than the "magic" number of 14.2 or so, an AGM is going to perform
> poorly or less than optimal.
>
> I further concur with your suggestion for utilizing a Charger
> specifically designed for AGM's on a routine basis. Any battery (let
> alone an AGM) will perform better following a good full three-stage
> charge from a 110VAC Charger. Gotta keep those electrons stirred-up....
>
> Phil Z.
> Campbell River, BC
> -----------------------
>
>
> Date:    Thu, 12 Jun 2008 11:37:31 -0700
> From:    Stuart MacMillan <macgroup@COMCAST.NET>
>
> After talking to a few marine electrical experts, it seems the problem
> with
> AGM's in cars is the alternator voltage is too low.  You need 14.2
> volts to
> fully charge a discharged AGM, and most alternators put out about 13 to
> 13.7
> volts, depending on load, which is fine for flooded standard and deep
> cycle
> batteries, but never fully charges an AGM.  So, either find someone who
> can
> tweak the alternator output, or buy a charger specifically designed for
> AGM
> & Gel and use it at least once a week.
>

--
Jake
1984 Vanagon GL
1986 Westy Weekender "Dixie"
Crescent Beach, BC
www.crescentbeachguitar.com
http://subyjake.googlepages.com/mydixiedarlin%27