Hi Larry,

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 KG6RCR

Larry Chase wrote: > Mike, > > 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 > www.roadhaus.com > > - - - > > 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 > 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 > > > >