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Date:         Sat, 8 Jul 2006 15:38:08 -0700
Reply-To:     Larry Chase <roadguy@ROADHAUS.COM>
Sender:       Vanagon Mailing List <>
From:         Larry Chase <roadguy@ROADHAUS.COM>
Subject:      Re: Norcold refrigerator + modest solar rig, a report [LVC]
Comments: cc: camping.elliott@GMAIL.COM
In-Reply-To:  <>
Content-Type: text/plain; charset="us-ascii"


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 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 again.

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 it.

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

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