The (New) 4WD Solar Fridge Project: V. 2 (2001 posting from old site – Page 5)

Got a new (used) 1991 isuzu Trooper in 2000. Finally, in late November 2006, bought a a new UNI-SOLAR panel (Model US-64 64W PV M) from Affordable Solar Group in Albuquerque, NM. Cost at that time was $319. (This was a higher than I expected to pay: the story was there was a shortage of panels in the market because the Japanese and Europeans were buying them up). They still show the panels on their site, but as of this writing (3/17/10) they’ve been discontinued:

Solar Panel Specs:
Model: UNI-SOLAR US-64
Rated power: 64 Watts
Operating Voltage: 16.5 Volts
Operating Current: 3.88 Amps
Open Circuit Voltage: 23.8 Volts
Short Circuit Current: 4.80 Amps
Bypass Diode Included: Yes
Blocking Diode Included: No
Minimum Blocking Diode: 8.0 Amp
Length x Width: 53.8″ x 29.2″ (1367 x 742 mm)
Weight: 20.2 lbs. (9.18kg)
Warranty on Power Output: 20 yr

Model: Interstate SRM-29
Ah: 125
12 Volts – Deep Cycle/ Cranking
BCI#: 29M/10
CCA: 675 MCA: 845
RC: 210 minutes
Warranty: 30 months
Dimensions (in): 13 x 6.75 x 10
Weight: 61 lbs. Terminal: Auto/Stud posts
Hours @ Ampere Load: 21@5; 6.4@15; 3.4@25

Refrigerator (Old): Norcold 330, 3.5 Amps at 12 Volts.

This panel has some advantages over the old system. These glass-free panels are extremely durable. You could shoot a bullet through them and they would still work. Or be hit by a rock (a more likely scenario). They are good in high temperatures (like the desert), and are extremely shadow tolerant. They supposedly work well under various lighting conditions such as cloudy days, because of having different layers that absorb different frequencies. And they came pre-framed.

You can just make out the fridge in the photo below (same old Norcold 330D – takes a licking and keeps on ticking). I covered it with silver insulated mylar from a windshield shade to keep it cooler.

Took it for a “shakedown” cruise in the Anza Borrego desert starting March 5, 2007. Camped out in a little wash. Used the same Norcold fridge, which is amazingly sturdy and reliable. Replaced the old RV battery with a larger, higher capacity model.

Below is a closer view, showing the mounting brackets. I decided not to use a hinged mounting system this time, because I ended up keeping the old system flat, and it’s vastly simpler. These are also very secure brakets: they mount underneath the panel, in a slot int he aluminum where you can’t get to them, and on the roof of the vehicle, four bolts and silicone hold them down. You can also see the windbreak I put on the front. Without it, the panels make a curious low wooshing noise above about 20 mph speeds while driving. The windbreak is made from a piece of wood, but was later replaced with aluminum bar, bent around the sides.

In June Wash, in the Anza Borrego Desert:

Solar Fridge Updates:
Took apart the back where the condenser is. Vacuumed and cleaned out, including coils.
Checked functioning with A/C at 5, 4, 3 settings using thermometer. Got down to around 20 degrees F.
Replaced rubber bumpers (they’d pretty much dissolved) on top that stop the lid when opened.

Replaced Norcold fridge (which was getting loud) with Dometic CF-25 , which is narrower, higher, and more advanced electronics with some useful features.

SPECIFICATIONS: Dometic CF-25 CF-25 “COOLFREEZE” Portable Fridge
CAPACITY: .9 Cu. Ft.
WEIGHT: 26.5 lbs.
TI = 41° F, TA = 68° F: 11%
TI = 41° F, TA = 89° F: 16%
MATERIALS: Injection molded housing with integrated rollbond evaporator; blow molded lid; PU foam insulation
COMPRESSOR: Fully hermetical Danfoss BD35F compressor with control electronics and integrated low voltage protection for 12V and 24V DC. Dynamic ventilated condenser, aluminum rollbond evaporator, electronics reverse polarity protection, adjustable electronic thermostat
BATTERY CONTROLLER: The coolbox is equipped with a battery controller cutting the compressor in or out in order to protect the battery and the compressor.
CUT OUT VOLTAGE: low 10.4 med 11.0 high 12.0
CUT IN VOLTAGE: low 11.2 med 12.0 high 12.9

Replaced the old old charging system with a SunSaver 6 (series instead of shunt, PWM), installed a wiring block, replaced battery.


Did some work on the fridge. Replaced the fan a few months ago (some of the blades broke off and it was generating an error). Found a replacement fan by matching model numbers, on a website from a company in Singapore. Turns out to be a server fan. Installed it and seemed to be working but was fairly loud – I did not transfer the thermistor from the old fan over since I couldn’t see a way to do it. Starting getting errors and the fridge just not keeping cold –seemed to be when the air was warm and/or when the sun was hitting it. So it may need that thermistor. Unfortunately the elctronics were re-designed, and I could not find an equivalent connection on the new fan’s circuit board for the thermistor.

So yesterday I made a Frankenstein fan by taking the old fan housing & electronic and sticking in the new fan blades/axle with it (plus a little spring from the new that pushes it out – without which it made scraping noises).

Also accidentally blew 20amp inline fuse on the positive lead that goes from the battery to the wiring block, but that wire was warm to the touch I noticed. Pulled out old fuse and saw the contacts were corroded. So put in a 10 amp fuse since that’s what I had (other than a 30 amp one). Better too small than too large: dont want to start a fire!

GO TO PAGE 6: Solar Fridge Project: V. 3

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