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Old 07-13-2014, 05:53 PM   #21
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Okay, I read the specs and saw the same thing: current at 24 volts is half that at 12 volts. That means that the appliance uses the same amount of power at either voltage, so there is no point in going to any effort to operate at 24V instead of 12V. It's 62 watts either way (5.2 x 12 or 2.6 x 24).

To illustrate this, let's say you are using two 12V batteries that can store 100 amp-hours of charge, and two solar panels which can produce 8 amps at 12 volts, each. You also have a refrigerator that uses 2.6 amps at 24V, or 5.2 amps at 12V.
You can connect both batteries and both panels in parallel, and have 200 amp-hours of storage and 16 amps of charging, all at 12 volts. The batteries could run the refrigerator for 38 hours (that's 200/5.2), and it would take 12 hours of full sun to recharge them (that's 200/16).
You could also connect both batteries and both panels in series, and have 100 amp-hours of storage and 8 amps of charging, all at 24 volts. The batteries could run the refrigerator for 38 hours (that's 100/2.6), and it would take 12 hours of full sun to recharge them (that's 100/8 ).

24 volt operation doesn't take any less power, so it doesn't have any advantage.
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Old 07-13-2014, 05:59 PM   #22
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As an aside...
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Originally Posted by wayne_m View Post
Are there 24 volt solar panels?
Yes, panels are sets of cells, and they are available with more cells in series to produce higher voltages. Also, 12 volt panels can be arranged in series just like batteries, and this is often done in large systems (not RVs) so that the power can be sent from panels to batteries with less current, and therefore lighter and cheaper wiring. Up to several hundred volts is practical.

However, it is pointless in an RV, where distances are short and the desired operating voltage is about 12V. It doesn't make the panels produce any more power.
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Old 07-13-2014, 06:15 PM   #23
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I would think there is no real advantage to go with 24V in a small trailer. You need more battery or solar power to run and charge at 24V, and battery space and weight comes at a premium. 2 12V deep cycle batts run in series will give you 24V, but at the cost of Amp hours. Strictly speaking 24V might be better if you were going to invert all the power to AC, because the inverter has less work to do. Other than that, 12V makes more sense.

I'm not at all convinced that a compressor fridge is a viable option in the Escape, mainly because nobody has tested just how much current you could create with dual 6V batts, solar, etc, vs how much draw the compressor fridge actually has in the real world. I know they work on Motor homes, but their entire roof can be made a solar panel, and battery space is not an issue.

But, if some brave soul wants to take the plunge, I'd be waiting eagerly to see if it really works. It could be the true fix for refrigeration.
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Old 07-13-2014, 06:38 PM   #24
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Quite a few owners of small moulded fiberglass travel trailers use compressor-type refrigerators. A search for a suitable keyword such as "NovaKool", "Engel" or "Danfoss" (a brand of compressor used in some refrigerators of this type) in the FiberglassRV forum will produce various real-world user reports. Other than the blatantly incorrect installations in the Outback model of trailer, and perhaps in TrillumRV models as well, I don't recall difficulty with the refrigerators working as claimed, and there seems to be enough roof space on a small trailer for adequate solar panels.
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Old 07-13-2014, 06:42 PM   #25
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Quote:
Originally Posted by rbryan4 View Post
You need more battery or solar power to run and charge at 24V...
Twice the voltage and half the current is the same power and doesn't take any more space for batteries or panels (although if comparing to a single-battery and single-panel 12V installation, 24V would mean two half-sized batteries and two half-sized panels). I agree that it's pointless, and it certainly makes problems for all the 12V stuff in the trailer (which is everything else battery-powered),
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Old 07-13-2014, 06:43 PM   #26
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Quote:
Originally Posted by Brian B-P View Post
Twice the voltage and half the current is the same power and doesn't take any more space for batteries or panels (although if comparing to a single-battery and single-panel 12V installation, 24V would mean two half-sized batteries and two half-sized panels). I agree that it's pointless, and it certainly makes problems for all the 12V stuff in the trailer (which is everything else battery-powered),
Right. I was comparing it to the single batt/single panel. Good to know it works on smaller trailers, provided they are equipped to make enough power.
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Old 07-13-2014, 06:59 PM   #27
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This posting is all new to me but our 19 coming in late November will have a 3 rear receivers. The intent is if required the outer ones will be used to mount an aluminum Box that will hold ARB Fridge- Freezer. The 63 Qt unit draws .07- 2.3 amp hr at 90 Degrees. Can be use with either12,24 or 120 volts. The 50 Qt draws 1.35 amps at 90 degrees. The have been in use in the Australian out back for years. Will have a dedicated 12 vole drop installed into the rear so it can be hardwire in. Still trying to get a handle on their solar system, looking for more that 160 watts and may add a 120w portable. The idea of a generator is not going to happen for me.
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Old 07-13-2014, 07:13 PM   #28
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I use a small 12V/120V Norcold marine fridge in my fiberglass trailer. We love it. I installed it myself and it has worked well in the desert and in the North. We would do it again.
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Old 07-13-2014, 07:18 PM   #29
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It appears that Dometic also makes refrigerators with Danfoss compressors. You have to go the marine section of their web site.

Interesting discussions- thanks all.
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Old 07-13-2014, 09:18 PM   #30
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Check out Thetford as well. They make several ac/dc fridges for RV. It's quite surprising that with the new compressor technology, the ac/dc fridges are far more power efficient than the 3-way fridges when running on DC.

Norcold Inc. Refrigerators
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