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PV in a RV running a refrigerator with some SLA batteries - sanity check

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james_s:
Propane powered refrigerators are neat, but efficient they are not. I remember my grandparents had a 1968 motorhome that had a propane refrigerator and the exhaust on that thing got ferociously hot. As a kid it was a complete mystery to me how a gas burner could be used to make something cold.

soldar:

--- Quote from: jmelson on January 10, 2019, 11:02:27 pm --- I'd never heard of compressor refrigerators with only a 72 W power draw!
Great stuff is being made.
--- End quote ---

My ancient mid -sized draws 100 W when running. I just bought a new full size and it also draws 100W and with lower duty cycle so it is more efficient and I am using less energy than before.

75 W or less for a smaller fridge sounds about right.

station240:

--- Quote from: Zero999 on January 10, 2019, 05:10:16 pm ---It uses a Danfoss BD35F compressor, which is very efficient and has a built-in VFD, which probably has a regulated output voltage.
http://files.danfoss.com/TechnicalInfo/Dila/06/bd_compressors_04-2007_pk100c802.pdf

--- End quote ---

Yes, internally it boosts the input voltage to ~48VDC, the compressor is BLDC without hall effect sensors.

Word of warning, don't get the compressor wet, the controller electronics have conformal coating, but no protection from short circuits.
The pins on the compressor itself can allow water in, which fries the BLDC drive mosfets and something in the supply.

DTJ:
The follow up post:

I tried the system with  the PWM charge controller below.

https://www.ebay.com.au/itm/30A-12V-24V-Solar-Panel-Battery-Regulator-Charge-Controller-LCD-USB-30AMP-PWM/322520750752?epid=676327152&hash=item4b17bc1aa0:g:U3wAAOSwfRdZHXsV:rk:6:pf:0

It worked but would sometimes kick out and disconnect the solar panel. Cycling the power reset it. It turned out the maximum PV input voltage was 24V.

I replaced it with a simpler regulator with a higher voltage spec for the PV input.
https://www.jaycar.com.au/12-24v-10a-solar-charge-controller-with-usb/p/MP3750


Its now been running a full 24 hours with the single 195W panel and a single 20Ah SLA. I think I'll add an additional 20Ahr SLA anyway to cover for poor solar days.

The Waeco 31 litre fridge only draws 4.1A when running. I have not measured the duty cycle but it sounds like the manufacturers spec of around 20% is reasonable.




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