12 volt Refrigerator

I got a great deal on a used RV. Sadly there was an issue. It came with a 7 cuft compressor refrigerator that chewed way too much power to be useable. If you want to learn the details, here is an example of the issues:
https://www.exploroz.com/members/145028.75/1/2009/queensland_adventures_winter_2008.aspx?p=%2fblogs%2fdefault.aspx

I could not easily convert to propane because there was no back access and no roof vent. Instead I got a much smaller (4 cuft) Nova Kool compressor refrigerator. It pulls 2.3 amps. The duty cycle time is HIGHLY dependent on ambient temperatures. Around 60 degrees it runs maybe 1/4 of the time. By 70 degrees, the duty cycle increases to between 1/3 and 1/2. At 80 degrees it runs full time. Beyond that it struggles to maintain frozen food and a 40 degree refrigerator temp. I super insulated the compartment, increased the ventilation and even use a couple of computer fans on the coils in hot weather.

1. DUTY CYCLE!!!!!!!!!!!!!! They don't run continuously.
2. You are looking at the specs for the LARGE 12 volt, THAT THEY JUST CAME OUT WITH. They sell the smaller 8 and 10/12 CF refers which draw less power. AND that large you read about will not fit most RV's. The smaller ones will.
3. MY POINT was missed. I was trying to show where the RV market was going by introducing the 12 volt compressor models that ARE battery efficient. Doug

Starting with only two 100a/h batteries (assuming wet cells), only gives you 100a/h usable for all your needs…Solar might augment, but with only two 64w panels, even the best harvest might only result in about 6.5 amps, then add to that the refer door seemed to be opening occasionally (ugg!!), and I think you were hitting the ‘sweet spot’ for failure… In this case I would have definitely gone with LPG, and I believe your trusty vendors were chock full of optimistic advice…This is why (per my previous…) having a substantial battery and solar set-up is critical, particularly the battery - this is why I said 400a/h Lithium, due to Li’s deeper depth of discharge, and the vagaries of solar to carry you over to the ‘next productive’ harvest cycle…And with a decent amount of solar, a few amps of harvest is often possible even with full cloud cover…While on the Oregon coast (with 660w solar) I was recently able to get about 6-7amps with full cloud cover and even a small amount of drizzle, admittedly not a whole lot but still enough over a time to ‘increase’ my 400a/h Lithium by a welcome 8% SOC…

I have a pal that has a 9 cu/ft (Danfoss comp) double door refer that runs fine with only two 100a/hr of Lithium and 400w MPPT solar (recently upgraded to 800w - fine for Nevada), and know of another fella that has a 7 cu/ft compressor refer (don’t recall the make), 460a/hr lithium and 400w of solar with no issues…So to achieve true LPG liberty, expect the devil is in the details ($$)…

3 tons

For the 4.5cf model it draws up to 72 watts when the compressor runs,very manageable with enough solar...

This unit draws 5-6amps when the compressor runs. A 100amp battery will run it, but the charge back from a 100w panel might not be sufficient to maintain the battery. It will depend on how often the compressor needs to run and how much charge back is achieved during the day.

Thanks,
Way Interglobal see less
By Way Interglobal SELLER on February 18, 2022

jaycocreek wrote:
For the 4.5cf model it draws up to 72 watts when the compressor runs,very manageable with enough solar...

This unit draws 5-6amps when the compressor runs. A 100amp battery will run it, but the charge back from a 100w panel might not be sufficient to maintain the battery. It will depend on how often the compressor needs to run and how much charge back is achieved during the day.

Thanks,
Way Interglobal see less
By Way Interglobal SELLER on February 18, 2022

It is pretty easy to calculate solar, generator and battery needs based on your information. The other missing data is run time which I find is highly dependent on ambient temps. I would plan for at least 80% in order to run the unit in low to moderate Summer temps. Anyway the 100AH battery is going to provide 50AH or a run time of less than 10 hours. I would want at least 4-6 batteries to avoid using the generator every few hours. Solar is a different issue. Right now where I live in NY a roof mounted, 100 watt solar panel is only going to provide about 40 AH/day of power. So under ideal conditions it would take at least 2 panels to break even. With about 50% cloud cover this time of year, that would mean 4 panels and more if you park in any shade or have an extended rainy period.

3 tons wrote:
Starting with only two 100a/h batteries (assuming wet cells), only gives you 100a/h usable for all your needs…Solar might augment, but with only two 64w panels, even the best harvest might only result in about 6.5 amps, then add to that the refer door seemed to be opening occasionally (ugg!!), and I think you were hitting the ‘sweet spot’ for failure… In this case I would have definitely gone with LPG, and I believe your trusty vendors were chock full of optimistic advice…This is why (per my previous…) having a substantial battery and solar set-up is critical, particularly the battery - this is why I said 400a/h Lithium, due to Li’s deeper depth of discharge, and the vagaries of solar to carry you over to the ‘next productive’ harvest cycle…And with a decent amount of solar, a few amps of harvest is often possible even with full cloud cover…While on the Oregon coast (with 660w solar) I was recently able to get about 6-7amps with full cloud cover and even a small amount of drizzle, admittedly not a whole lot but still enough over a time to ‘increase’ my 400a/h Lithium by a welcome 8% SOC…

I have a pal that has a 9 cu/ft (Danfoss comp) double door refer that runs fine with only two 100a/hr of Lithium and 400w MPPT solar (recently upgraded to 800w - fine for Nevada), and know of another fella that has a 7 cu/ft compressor refer (don’t recall the make), 460a/hr lithium and 400w of solar with no issues…So to achieve true LPG liberty, expect the devil is in the details ($$)…

3 tons

200amp-hr @ 12v will result in around 1200w-hr of usable power (2400w-hr total) assuming you start from 100% charge and they are in good shape.

At 50w when the compressor is in operation, that's about 24hr of run time at 100% duty cycle. Assuming a more typical 50% duty cycle, that's around 48hr or about 600w-hr per day.

2 - 64w panels (128w total) will generate about 500w-hr per day.

Assuming no other loads, you are probably OK for a long weekend.
- End of 1st 24hr, you've used 600w-hr and put 500w-hr back in leaving a net of 1100w-hr.
- End of 2nd 24hr, you've used 1200w-hr and put 1000w-hr back in leaving 1000w-hr
- End of 3rd 24hr, you've used 1800w-hr and put 1500w-hr back in leaving 900w-hr

But in reality, the systems aren't 100% efficient and you may use a bit more or generate a bit less, so by the 3rd 24hr period, it's going to be condition dependent.
- If it's a cool sunny weekend, you might be near full on the batteries.
- If it's a hot muggy overcast weekend, you might be running a bit low for the 2nd day.

Always good to have a fall back charging method rather than way overbuild the system so it can handle anything.

PS: This assumes you have no other electrical loads other than the fridge...and why it's good to do a general energy audit rather than look at a single component.

theoldwizard1 wrote:

corvettekent wrote:
You would be much better off with a propane refrigerator.

That is debatable ! You could be in big trouble if you run out of propane and there is no refill station nearby.

With adequate solar and batteries a 12V compressor refrigerator is far superior to any propane evaporative refrigerator, especially when the outside temps are in the 80s or above.

I certainly would have a generator, even a 2000W portable. Also a DC-DC charger.

I think you'd really have to be asleep at the wheel if you run out of propane. With 2-7.5 gallon tanks, I've gone 30 days with no fill ups and using the water heater too. No furnace for that thirty days though. I'd be thinking in a thirty day period one should be able to come across some propane to fill the tanks.

Thanks for the link! Verified my fear of purchasing a soly 12 volt equipt RV. Now I have another thing to put on my bucket list, Australia looks like a great adventure.

Tanks again!

JimK-NY wrote:
I got a great deal on a used RV. Sadly there was an issue. It came with a 7 cuft compressor refrigerator that chewed way too much power to be useable. If you want to learn the details, here is an example of the issues:
https://www.exploroz.com/members/145028.75/1/2009/queensland_adventures_winter_2008.aspx?p=%2fblogs%2fdefault.aspx

I could not easily convert to propane because there was no back access and no roof vent. Instead I got a much smaller (4 cuft) Nova Kool compressor refrigerator. It pulls 2.3 amps. The duty cycle time is HIGHLY dependent on ambient temperatures. Around 60 degrees it runs maybe 1/4 of the time. By 70 degrees, the duty cycle increases to between 1/3 and 1/2. At 80 degrees it runs full time. Beyond that it struggles to maintain frozen food and a 40 degree refrigerator temp. I super insulated the compartment, increased the ventilation and even use a couple of computer fans on the coils in hot weather.

Vintage465 wrote:

theoldwizard1 wrote:

corvettekent wrote:
You would be much better off with a propane refrigerator.

That is debatable ! You could be in big trouble if you run out of propane and there is no refill station nearby.

With adequate solar and batteries a 12V compressor refrigerator is far superior to any propane evaporative refrigerator, especially when the outside temps are in the 80s or above.

I certainly would have a generator, even a 2000W portable. Also a DC-DC charger.

I think you'd really have to be asleep at the wheel if you run out of propane. With 2-7.5 gallon tanks, I've gone 30 days with no fill ups and using the water heater too. No furnace for that thirty days though. I'd be thinking in a thirty day period one should be able to come across some propane to fill the tanks.

More like the typical "sky could fall" post in virtually every thread on here.
And, I man, yeah, like, a DC fridge is totally more reliable, if you forget to refill your propane for like 3 months, as long as you carry 2 generators and a DC-DC charger!

roflmao