Date:         Sat, 1 Apr 2006 00:58:07 -0500
Reply-To:     "Daniel L. Katz" <katzd54@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Daniel L. Katz" <katzd54@YAHOO.COM>
Subject:      Re: electrical experts: voltage drop and the fridge theory.

11.4 V across fridge terminals with 12.4 across battery terminals, but
only 2 x 3 ft = 6 ft of wire between, implies significant contact
resistance(s) because 12 awg is only 1 - 2 ohm per 1000 ft. roughly,
voltage to drive 10 A through 6 ft of 12 awg is 10 amp x 6 ft x 1.5
ohm/1000 ft = .09 V.

On Thu, 30 Mar 2006 21:01:34 -0500, robert shawn feller
<feller@CARBONCOW.COM> wrote:

>I am amusing myself since I've been fixing and testing the fridge on the
>bench. It's staying cool to 30 degrees on 110v for me. I just bought a new
>1000amp hour deep cycle for the new wiring I'm doing in my westy related
to
>other needs then the fridge.
>
>I figured I would hook it up to the fridge to just see how horrible a job
it
>does (we all know 12v and the fridge are not the best friends). I should
get
>a good day out of it based on calculations.
>
>Here is my question:
>
>The voltage at the battery (under load) reads 12.4 volts but at the
terminal
>it reads 11.5 volts, only 3 feet of wire between the battery and this
>terminal! Is the inefficiency of the battery cooling the system do to
>improper low gauge wiring?
>
>Seems to me that if there is 7% voltage drop in such a short run the
wiring
>gauge for the heating element and the wires to the battery could be
>improperly rated. This would then affect amperage and thus the final
wattage
>(which is supposed to be the same as the 110v) is never achieved. I would
>assume those of you keeping the battery under the seat and running more
>length of wire then I would have slightly more drop.
>
> If I recall from my boat wiring days a 3% drop is the recommended goal
for
>any length of run from the governing body for boat builders but as high as
>9% for least acceptable.
>
>Any thoughts.or do  I not know what I'm talking about!
>
>Shawn