Date: Thu, 22 Jun 2006 15:59:15 -0700
Reply-To: Mike Elliott <j.michael.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike Elliott <j.michael.elliott@GMAIL.COM>
Subject: Re: Norcold results (long)
In-Reply-To: <cf4df96f0606221449g2e4873dexd5c9fb64de5bed68@mail.gmail.com>
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On 6/22/2006 2:49 PM robert shawn feller wrote:
> The dometics on average are junk after 20 years of age. Just went through
> the same thing as mine was great on the bench under 110v or propane
> but just
> will not get cold installed and on the road. Most likly due to heat
> dissipation in the rear from the coils, even with a new fan inside and
> out.
>
> Yes many of you have ones that work "ok" but most are a hassle in far to
> many ways. That Norcold should run fine for days on 12v. Use the same
> common
> sense everyone speak of when dealing with the temperamental Dometics.
> Prechill things, keep door closed. Keep your beers in a cooler and you
> meat
> in the fridge!
>
> You may want to look up Karl Mullendore (karl@westyventures.com) as he
> raves
> about the success and staying power of his DC0040.
It was Karl's writeup that inspired me to install a DC0040. Maybe he
camps in cooler weather than I do. I don't see any way for the Norcold
to run fine on 12v for days . . . I made my earlier results post with
precooled stuff in the Norcold and without any door openings. To keep
things at 40F when the outside temp is in the upper 80's it ran for 60%
of the time -- that's setting "3" on the dial, which is exactly where
the Norcold manual says to set it when temps are 70 to 90F.
With a 2.5A compressor, that's 1.5 amp-hours. If it has to run at that
rate from, say, 8 in the morning to, say 8 at night, it comes to 18
amp-hours. Add in some nighttime cooling and some windage and I'm
thinking that a battery that can produce 36 amp-hours before its voltage
gets too low is the minimum needed.
But what is "too low"? Probably more than the 10.5 volts that we
normally quote when calculating the amp-hour capacity of a flooded
lead-acid battery. The installation manual for the Norcold does not
discuss minimum operating voltage. The Norcold slows down as battery
voltage drops. At 12.8 volts it sounds real peppy. At 12.3v it sounds a
bit lazy. I'm not sure how "cooling power" (there is a technical term
for this, I am sure) relates to battery voltage for a Norcold, but I bet
that at 10.5v it might not be real efficient.
So I'm going to change from the little Optima under-seat battery that I
installed last year, and may have damaged with my cheap-o Harbor Freight
trickle charger, and go to a heftier Group 27 deep-cycle battery under
the bench seat as you recommended last week. 90 to 110 ampere-hours
seems to be what a fellow can expect from a deep-cycle Group 27 battery,
but that's measured to 10.5 volts, and not the unknown minimum operating
voltage of the Norcold, which is probably higher.
I'll find out on the next camping trip how well it works in practice. If
that ain't enough, then a couple of 6V golf-cart batteries hooked in
series, as a list member suggested to me earlier today, will provide a
doubling of capacity (225 amp-hour to 10.5v).
According to my calculations, my solar rig, which outputs 6.5A in full
sun could, if it has sun for 10 hours (not impossible where I live)
generate 65 amp-hours a day if I keep an eye on the panels and move them
so they are in sun all day long. That seems like it's enough to support
the Norcold's needs handily. I don't want to load Mellow Yellow down
with too much refrigerator-support equipment (panels, batteries) and I
don't want to go back to the Dometic, which could not pull more than
about 40 degrees differential between outside temp and reefer inside
temp despite all the cooling fans and other tricks I did to it. When
cheddar cheese gets sweat drops on the outside, I lose interest in it.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
