Date:         Wed, 10 Jan 2007 23:17:45 -0500
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Westy battery indicator light below sink
Comments: To: Loren Busch <starwagen@GMAIL.COM>
In-Reply-To:  <86476e250611281135g692e5c5aued02b3ae2774e8d3@mail.gmail.co m>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 11:35 AM 11/28/2006 -0800, Loren Busch wrote:
>The Westfalia manual says that green is greater than 12.5v, yellow is less
>than 12.5 v, and red is for less than 12 v.  This means that it takes very
>little draw down to go to yellow, just disipation of the surface charge in a
>short time after the engine is turned off may pull it down to yellow.

There's a tweak on the back to adjust the green/yellow transition to
whatever voltage you like.  Whatever you set it to, the yellow/red
transition will be 0.5 volts less than that, e.g. you set
green/yellow for 12.3 then yellow/red will be 11.8.  If you want to
alter that relationship you have to change resistors on the board.

VW show a consistent philosophy in the operation of the water and
battery lights -- green means practically full, red means practically
empty, yellow is everything else.  The battery light is only crudely
useful because in order to get an accurate measure of battery state
with a voltmeter, you have to let it rest 12-24 hours with no load,
then measure the unloaded voltage.  Perfectly practical -- if you
have two house banks and can let one rest while you use the
other.  Given that, I think the voltages they chose for the lights
are appropriate.  When a good-size load starts dipping into the red,
time to run the engine for a bit.  When the light is red with no
recent loads, mebbe time to push-start it while you still can.  The
better you understand batteries in general and your battery in
particular, the more useful the lights are, I think.  And a good
hydrometer will give good answers at the cost of waving acid around
inside the cabin.


--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"