One thing to consider with multi-stage chargers is that they usually only
work with no load on the battery circuit during the charge process. There
are exceptions but the finish and de-sulphation voltages can wreak havoc on
light bulbs and anything sensitive downstream. 12 volt light bulbs don�t
last long at 15.5 to 16 volts. 

Dennis 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Rocket J Squirrel
Sent: Saturday, September 05, 2009 6:54 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Run time to charge Aux battery

Or, put this 4-stage charger between your starter battery and your aux
battery:

http://www.sterling-power.com/products-battbatt.htm
http://www.sterling-power.com/products-battbatt-install.htm

The 50A version is �256.83 at
http://www.the12voltshop.co.uk/Shop/battery-to-battery-charger-12v-to-12v-50
a.html

--
Mike "Rocket J Squirrel" Elliott
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
Bend, OR
KG6RCR

On 9/5/2009 2:03 AM Malcolm Stebbins wrote:

> I know very little about electricity!  I checked the archives  and I found
this article, but it did not exactly answer my question:
>
http://gerry.vanagon.com/files/motorhome/Motorhome-Alternator-Charging-Syste
ms.txt
>
> I have 2, 6 volt deep cycle batteries hooked up and I have about 200-ish
amps (I think) in the aux batteries.  This is used to run my Waeco fridge,
which takes about 7 amps when it runs, but only runs about every 10 minutes
for 2 minutes-ish.
>
> Usually I only park for a day or 2 max, so  all is OK with the aux
battery, but  this last trip I stayed parked for 4 or 5 days in a row, and
the fridge's 'low battery' light came on.
>
>  My question is:  APPROXIMATELY what is the charge rate IN AMPS for a nice
good working system.  I say good system as I have a new Zetec engine with a
100+ amp alternator and the wires are all new and the batteries are
relatively new.
>
> I use a SUREPOWER 1315 isolator for the 2 battery sets.
>
> When the battery got low, I took to idling the van for about 15 minutes in
the morning, and again 15 minutes in the evening, to help the battery a bit
and this seemed to help.  Is this folly?
>
> Thanks   Malcolm
>