Date: Fri, 3 Aug 2001 10:38:46 -0400
Reply-To: Joe Reed <joe.reed@MINDSPRING.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Joe Reed <joe.reed@MINDSPRING.COM>
Subject: Re: insane AC idea
---- Original Message -----
From: Steve Sandlin
To: vanagon@GERRY.VANAGON.COM
Sent: Friday, August 03, 2001 10:20 AM
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
============================
We're using a second, deep-cycle 72-amp hour battery (dedicated to the
a/c -- we're not using the Vanagon car battery) which at 100 amps provides a
cycle of 7.2 hours of continuous draw before requiring charging.
The a/c doesn't pull 10 amps -- at PEAK compressor activity it draws 6
amps/690 watts. As I said before, the inverter we borrowed for the initial
testing supplies 15 amps and 800 watts, which so far has proved to be more
than adequate. Also, the efficiency on the solid-state inverter was rated at
90% and so far we don't see anything to dispute that. This isn't a low-end
inverter...I can pull the info on it this weekend when they bring it back
over if you like.
The Vanagon alternator, then, should have no trouble providing a recharge on
a long trip when necessary.
We did run the numbers -- and so far it appears to work. Of course, I never
said it was guaranteed!
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