Date: Sat, 8 Jul 2006 17:43:47 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <email@example.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Norcold refrigerator + modest solar rig, a report [LVC]
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Sorry about the confusion. The Norcold does not run continuously, else
that would be 2.5A x 24 = 36 amp-hours. On this trip, when it was in the
mid-80's in the day it ran between 40% to 60% of the time in the day.
Since it draws 2.5 amps while running, this comes to 1 to 1.5 amp-hours
per hour during the warm part of the day. Looking at the overall usage
during this last trip, I would average out the daylight running at 50%,
the nighttime at 20%, so that comes to (stops to count on fingers) uh .
. . 19.5 amp-hours in a 24-hour period.
Yes, I agree that the Optima should be able to keep up. But during the
trip three weeks prior to this one, when I was running off a yellow-top,
the Optima ran down to 10.7 volts by around 3am and the alarm went off.
Very discouraging to shut off the reefer in the middle of the night.
The deep-cycle Group 31 (www.westmarine.com, one of their Sea Volt
batteries made by East-Penn) went from 12.8 volts when the sun went down
to 12.4 volts in the morning, after running the Norcold all night and a
notebook for watching a DVD.
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
Larry Chase wrote:
> Great report.
> Can you give us a link and/or details on the Group 31 100 amp-hour battery.
> Nice set up.
> On thing confuses me a bit.
> You stated,
> "When running, the Norcold draws 2.5A, so that comes to 1 to 1.5 amp-hours
> per hour during my warm daylight hours. Fewer at night when it's colder
> outside and inside."
> So if I take an extreme worse case example and say the fridge uses 1.5 amps
> per hr over 24 hrs that equals = 36 amp hrs of usage per day.
> Although cutting it close, it seems that the 55 amp hr optima would handle
> things for one day without problems.
> When you then factor in the solar panels at 6-7 amps per hr while charging
> in full Sun ... It seems you could run the fridge and recharge the optima in
> a good full sun day.
> The only problem would be if you didn't have sun for the solar?
> And of course that wouldn't give you any room to run additional appliances
> like the laptop and such.
> good road,
> good adventure,
> good life,
> larry chase
> - - -
> Date: Fri, 7 Jul 2006 16:14:32 -0700
> From: "Mike \"Rocket J Squirrel\" Elliott" <camping.elliott@GMAIL.COM>
> Subject: Norcold refrigerator + modest solar rig, a report [LVC]
> Hi all,
> Three weeks ago I reported here how my newly-installed Norcold DC0040
> refrigerator drained my under-seat Optima battery before dawn.
> In brief: I was mistaken to think that the Norcold would run only 5 to 10
> minutes an hour. I don't know where I got that impression. A more accurate
> value is between four to six minutes out of every ten minutes in my
> conditions of 85F ambient temp (same inside the van), or a duty cycle of
> between 40 to 60%. When running, the Norcold draws 2.5A, so that comes to 1
> to 1.5 amp-hours per hour during my warm daylight hours. Fewer at night when
> it's colder outside and inside.
> I received numerous helpful suggestions from several Vanagon.com folks,
> including, some tech-heavy, battery fundamentals and energy management
> responses from Dennis Haynes and David Beierl. To summarize from all the
> helpful folks:
> 1. The run time I got from my Norcold is about what should be expected from
> this unit. So if I want to use it, I better have sufficient power.
> 2. The Optima battery is simply too small to count on for overnight running,
> despite my careful nighttime energy managment.
> 3. Something beefier, like a Group 27 or 31 deep-cycle would kick the
> Optima's butt. This is what I was told.
> The only remaining problem would be whether my modest solar rig could keep
> up with the demand.
> So, I pulled the Optima and moved a bunch of my tools under the seat, and
> installed a deep-cycle Group 31 100 amp-hour house battery under the bench
> seat, with 4 gauge wire run to it from the charging relay. Then Mrs Squirrel
> and I went on a three-night camping trip in the Cleveland National Forest. I
> was deeply concerned that unless I ran the engine to add amps back into the
> house battery, I would be running out of refrigeration before dawn. "Great,"
> said Mrs Squirrel, "nothing like running the engine for an hour or so on an
> already hot day." Yeah, I know.
> Here's what happened: On the first day, we set up camp at 2 pm. Mellow
> Yellow's alternator is set to 14.0 volts, so I knew that I had not fully
> charged the house battery, but was close.
> I set up the solar panels and within two hours the controller dropped into
> its low-current absorption voltage mode of 14.8 volts, indicating the
> battery was fully-charged. When we went to bed, I noted that the battery
> voltage was 12.7 volts, unloaded (no current being drawn from the battery).
> Overnight, the temps dropped to the mid-50's, so the Norcold was only
> operating for a couple minutes out of every ten.
> (I still marvel that the reefer [means "refrigerator" in parlance] reliably
> comes on every 10 minutes, regardless of the setting on the dial. The more
> you turn the knob clockwise, the colder the reefer will get inside, and once
> it has reached that point, the compressor will turn off. Wait 10 minutes and
> it will turn on again, and run as long as needed to keep the temp where you
> set it, then shut off . . . until another 10 minutes has passed. Have to get
> a service manual to see if there is clock in the thing).
> Anyways, in the morning, the unloaded voltage of the house battery was 12.5
> volts. I set up the solar panels to point toward where the sun would strike
> them once it cleared the trees, and left camp at 8:30 on a bicycle ride to
> the general store to buy some soft drinks (2.5 miles steady 7% climb up to
> the store, 2.5 miles steady "Look ma -- no hands!" downhill back from the
> store). When I returned, at 10:30, the voltage was 14.8 and the controller
> has switched into low-current absorption mode. The two 45-watt BP solar
> panels had brought the battery back to fully-charged in about 2 hours.
> The panels are wired to a Blue Sky 2000E MPPT solar controller, which
> handles battery charging, as well as squeezing every available amp out of
> the panels. It works brilliantly. Under good conditions, the controller can
> eke 6 to 7 amps out of the pair of panels. The output of the controller is
> high enough to easily power the Norcold while continuing to dump current
> into the battery. I watched the battery ammeter switch from a charging
> current of 6 amps to 3.5 amps when the reefer kicked in. Around noon, it
> became overcast as moist air from the Sea of Cortez was hoisted over the
> Laguna Mountains by a southeasterly wind, and turned into thunderheads.
> Lightning, thunder, wind, hail, and rain ensued, a good time was had by all.
> During this time, the output from the panels dropped to nothing and the
> Norcold, running a 50% duty cycle in the 80F temperatures, ran off the
> battery. At 5pm, the clouds dissipated, and by 6:30pm, the battery was full
> That's pretty much how it went: a couple hours of full sun in the morning is
> all it took to bring the battery back to full charge, and during the day,
> the panels mainly loafed in absorption mode, increasing power as needed to
> power the reefer or other loads. At no time during the day did the battery
> do anything more than provide ballast duty and help hold Mellow Yellow to
> the ground.
> On our final night, we watched a movie on my notebook computers, which draws
> about 4 amps per hour, so call it 8 amp-hours. Add in, say, a 25% duty cycle
> on the reefer over a 12-hour 7p to 7a period of time, which amounts to 7.5
> amp-hours, for a total of around 16 amp-hours. In the morning, with panels
> cranking out 7 amps AND operating the reefer at
> (say) a 40% duty-cycle as the day warms up (1 amp-hour load), that leaves 6
> amps for battery charging, or about 3 hours (18 amp-hours) to fully recharge
> The bottom line is that this modest solar rig is more than capable of
> keeping up with my electric load -- as long as there is sunlight. If the sun
> goes away . . . well, we don't camp much if it stays gloomy for too long. So
> we're very pleased.
> 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