Date:         Fri, 12 May 2000 10:28:16 -0400
Reply-To:     David Beierl <dbeierl@IBM.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@IBM.NET>
Subject:      Re: What is the simplest way to get 12V in a 24V VW electrical
              system?
Comments: To: David Marshall <vanagon@VOLKSWAGEN.ORG>
In-Reply-To:  <3.0.3.32.20000511224501.00e53cf0@mail.abccom.bc.ca>
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At 01:45 5/12/2000, David Marshall wrote:
>would be 12V.  I guess the flaw in my logic might be that if they were two
>IDENTICAL 12V lights then they would take 12V each... if one light, or one
>light and the 12V accessory attached to it take more current than the
>other, the voltage will be different... am I right or am I wrong?

That's it exactly.  And it would work for a light load, although if the
wrong light burnt out you would probably smoke the load.

I think you have three choices, really: 1) run off the bottom battery, and
maybe it dies a bit early, so what.  If you mostly run with the motor on, I
wouldn't think it'd make the slightest difference anyway.  If not, might
maybe have a problem with the *other* battery overcharging, as all the
charging current has to go through both batts.
2) buy the converter for whatever they want for it.
3) build your own voltage regulators -- I'd be very surprised if the ARRL
book didn't have some circuits to get you started.  Several little ones
might be easier and cheaper than one big one, I don't know.  A real
quick-and-dirty would be just stick big diodes in series until you get the
drop you want -- just remember you'll be dissipating the same amount as
waste heat that your device actually uses.
4) Find a mil-surplus dynamotor (motor-generator set) that goes from 24v to
12v -- that would be the authentic way to do it. <g>  I dunno if they built
that combination, though.

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