Date:         Fri, 3 Aug 2001 10:33:08 -0400
Reply-To:     Wade Shen <swade@UMIACS.UMD.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Wade Shen <swade@UMIACS.UMD.EDU>
Subject:      Re: insane AC idea
In-Reply-To:  <F165FkuutSgcOrBLSAQ0000eccf@hotmail.com>
Content-Type: multipart/alternative;

Steve is right. Even if you are able to run it for a couple of minutes, you
won't be able to continue charging the battery with that kind of current
draw.  Of course, you could consider a second alternator (not!).

wade

PS, there's a company called dongfar that makes a 12v 1300btu AC system.
They claim something like 300 watts of power usage.  This may be more
doable, but I haven't ground through the math.
  -----Original Message-----
  From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf Of
Steve Sandlin
  Sent: Friday, August 03, 2001 10:20 AM
  To: vanagon@GERRY.VANAGON.COM
  Subject: Re: insane AC idea


  I also use a small window AC in my westy, but only while camping.  It
mounts in the drivers window.  I think you have overlooked a major problem
in trying to use the unit while operating...power.  Though the inverter is
heavy enough to handle the A/C, you can't supply enough 12 volts to the
battery/inverter to keep the battery charged, not to speak of running the
van itself, plus lights, radio, etc.  If the A/C pulls 10 Amps at 120V,
that's 1200 Watts.  Assume 75% effeciency on the inverter (that's
optimistic) and you'll find energy useage of 1500W.  A 70 Amp Vanagon
alternator at 12 volts supplies a maximum of 840W, barely half of what you
need just for the A/C.  Where is the rest of the power coming from?  If you
are depending on the battery to supply it, you'll be in a dead battery state
very shortly, not to speak of decreased altermator life while running it
full tilt for extended lengths of ! time.  The power just isn't there...run
the numbers.
  Steve Sandlin
  '84 Wolfsburg Westy
  '79 Bus
  '00 New Beetle


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