Anyone measured real world wattage for cheap 12v compressor fridges?

[Spaceman Spiff]

How many folks have actually measured their usage? As many responses as there are variables are definitely welcome.

When I got my new refrigerator last winter I measured energy usage using a Kill-A-Watt meter.
Refrigerator: SPT 2.4 cu.ft mini refrigerator from Home Depot, 120V.

Result: 547.2 watts used in 24 hours.
- Refrigerator was in 70º environment, out of sun,
- test made after fridge was cooled down for 48 hours,
- opened 8 times throughout day to check inside temperature (~34º).

My system:
- refrigerator is in a cabinet with forced air cooling on back, sides, top (when air temp is over 80ºF).
- Inverter is Victron 500VA PSW.
- 208AH GC2, 200W solar, PWM controller.
Batteries didn't dip below 85% in AM when they started night at 100%.

For the record I do intend to build a box around the fridge that's well insulated with residential foam board, and adequately vented via the factory vent holes.

If you go cheap dorm type fridge with skin heat exchange you cannot cover the sides, or back; must have air circulation. I didn't find that to be a problem. I have 3" of clearance on sides, back, and top in cabinet.

 

[gizmotron]

The actual science is kind of boring, but I fixed it by only using regulated power for my stuff.

It's a ground loop caused by the potential voltage between units on the chain. One unit might be 2 volts and another might be 3 volts. So between them you get a +1 volt current flow across the two units. That becomes line noise. I'm talking about the cases of the units and the circuit boards inside each effect. This tends to apply to grounded units that use internal power supplies. I'm going to give up on the idea by just getting more power, (solar) and sticking with isolated external power supplies. Once I saw all these custom values and polarities I decided to forget it. But it sure would be interesting to see what results you get.

 

[Calaverasgrande]

I dont think I have voltage potentials between geare, so much as older gear that dumps noise on the power rails.
There does seem to be a couple pedals that do have minor voltage offsets on their audio outs.

 

[Catalyst1]

I did some tests on my joytutu 26L when I first got it last summer. But I only measure by amp hours, since its easier for me track. As soon as I got the fridge I was trying to get it down to 8f but it was taking too long and after about 40ah over 24 hours I decided to raise the temperature to 12 f, it held that over 24 hours with 38ah. I noticed the exterior of the fridge was cold, so the cold was cooling the exterior of the fridge.
I decided to hotglue 3 x 1/2" layers of foam around the exterior of the fridge and it actually worked, at 12f it was using between 26ah and 30ah depending on the temperature inside the van which was getting into high 90s/low 100's. At 12f I could keep fishsticks and frozen taters cold enough, and water would freeze after a day. If you put frozen gallon of water in there it would stay frozen.
When winter arrived, 12f was using too much power and the limited sun was not charging my batteries back up, I raise the temp to 26f, the insulation was so good that the frozen gallon of water I had in there took 3 days to thaw out, compressor didnt run for 3 days as temp went up to 26f.
At 26f the fridge uses 18ah per 24 hours. On my fridge 26f is cold enough to keep all my sodas,water,milk cold without freezing it.
So your idea of adding foam will work, I tested it first hand but if possible I would hotglue it without leaving any gaps. The only place not to put foam is in the vents.
And definitely vent the fridge, I wouldn't run a fridge in my van unless I could vent it. On a hot day when the compressor runs, the air out of the vents is in the 100's (measured with IR thermometer) . I made a enclosure that fits around the vent and put a small 120mm fan that sucks the hot air and sends it out the side door through some 4" flexible ducting. I almost got rid of the fridge because of the hot air but now its a non issue even on the hottest days.

The joytutu is not too small or too big. As far as reliability its been running nonstop 24/7 for the past year. Who knows how long it will last but price less then 300 was good. Even though its a 26L it does get full quickly, so I wouldn't recommend getting one of the real small fridges, I know in the real world I wouldn't be happy with anything smaller then 26L. Especially if you want to put a 1/2 gallon jug of milk or juice in the fridge upright. I did alot of research on fridges before I bought one, I was also considering a smaller shorter one. Any fridge you get is going to take up space.

View attachment 28159

"And definitely vent the fridge, I wouldn't run a fridge in my van unless I could vent it. On a hot day when the compressor runs, the air out of the vents is in the 100's (measured with IR thermometer) "
Maybe in the cooler months, it would be good to be able to put the heat back into your living space. Free heat source.

 

[afblangley]

In real world use, fridge power consumption is a function of the ambient temperature in the vehicle. Everything else (thermostat settings, food contents, lid kept closed) being the same, this alone can make it vary dramatically. My fridge has consumed as little as 10% and as much as 25% of my power station overnight.

 

[PeterPiper]

1.7cu Ft Galanz Walmart dorm fridge purchased in 2019 for $79.00
Going through a Renogy 1000watt inverter.
As you can see - 227 Watt hours over 10 hours. Ambient room temp 80F.

Probably would have cut it down to 125-150watt hours if the room had been 70F

 

[rruff]

I have tested 3 different Setpower tc20 12 volt refrigerators. Completely empty, set at 25 degrees Fahrenheit, and in a house that's about 70 degrees, they ran for 48 hours on a 300 watt, 500 watt hour Bluetti battery. The Bluetti started on a full charge and ran out until it died.

I tested 2 Joytutus 12 volt refrigerators in the same conditions and the compressors ran almost continually and killed the battery in 16 hours or less. I tested those full and empty and it didn't matter. They both killed the battery in 16 hours.

Two people also said the Setpower refrigerators are insulated well enough that they can turn them off at night, to save battery power, and the temperature inside the refrigerator only increase 5 to 10 degrees by morning. I haven't tested that out though.

Lots of good info in this thread!

Your experience shows that not all cheap 12v refrigerators are are created equal. The Setpower's average power consumption was only ~10W while the Joytutus was ~31W ... which is worse than a lot of dorm fridges + inverter setups! In the 70F conditions you measured the Setpower would use ~250W-hr/day, and you'd need ~50W of solar (on average!) to replenish that, and 100W should give you a decent buffer.

As someone mentioned, the heat loss will be proportional to the difference in temperature between the air outside the fridge vs inside. You said it was set at 25F, but if nothing was freezing inside, it would have actually been 32 or greater. So a temperature differential of 38F or less. I'll rarely be camping where the average temperature during the day is 70F or more. In winter ~55F is more like it.

It sounds like these fridges might not operate efficiently at below-freezing temperatures. I had a bright idea to get a small one just to freeze ice when there was excess sun, then use the ice in a good cooler. This would eliminate the need for added battery capacity and give you a good buffer for cloudy conditions... but it might not work very well if they are inefficient at below-freezing temperatures.

 

[PeterPiper]

I just realized that my Galanz 50QT dorm fridge used about the same energy as the DC fridges tested by scaredycat. Maybe a bit less since the Galanz fridge was much larger and operated in a warmer environment.

That is to say....

A dorm fridge "could be" twice as energy efficient as a DC fridge....even counting and including the Inverter losses.

 

[rruff]

I just realized that my Galanz 50QT dorm fridge used about the same energy as the DC fridges tested by scaredycat. Maybe a bit less since the Galanz fridge was much larger and operated in a warmer environment.

The Setpower used ~10W in 70F ambient with a 32F? internal. You used 22.7W average, above. On the previous page you said a little over 500W-hrs for 24 hrs, which is the same (22W+). Is your inside the van temperature really 80F average this time of year? And what was the temperature in your refrigerator?

 

[PeterPiper]

Right...she said "48" hours.....I missed that thinking it was 24.

I have tested 3 different Setpower tc20 12 volt refrigerators. Completely empty, set at 25 degrees Fahrenheit, and in a house that's about 70 degrees, they ran for 48 hours on a 300 watt, 500 watt hour Bluetti battery. The Bluetti started on a full charge and ran out until it died.

I tested 2 Joytutus 12 volt refrigerators in the same conditions and the compressors ran almost continually and killed the battery in 16 hours or less. I tested those full and empty and it didn't matter. They both killed the battery in 16 hours.

Two people also said the Setpower refrigerators are insulated well enough that they can turn them off at night, to save battery power, and the temperature inside the refrigerator only increase 5 to 10 degrees by morning. I haven't tested that out though.

Thanks

I need to do a re-test with ambient set at 70F.
Internal on the Galanaz was 20F (freezer) and 32F for the fridge....

 

[user 16179]

Lots of good info in this thread!

Your experience shows that not all cheap 12v refrigerators are are created equal. The Setpower's average power consumption was only ~10W while the Joytutus was ~31W ... which is worse than a lot of dorm fridges + inverter setups! In the 70F conditions you measured the Setpower would use ~250W-hr/day, and you'd need ~50W of solar (on average!) to replenish that, and 100W should give you a decent buffer.

As someone mentioned, the heat loss will be proportional to the difference in temperature between the air outside the fridge vs inside. You said it was set at 25F, but if nothing was freezing inside, it would have actually been 32 or greater. So a temperature differential of 38F or less. I'll rarely be camping where the average temperature during the day is 70F or more. In winter ~55F is more like it.

It sounds like these fridges might not operate efficiently at below-freezing temperatures. I had a bright idea to get a small one just to freeze ice when there was excess sun, then use the ice in a good cooler. This would eliminate the need for added battery capacity and give you a good buffer for cloudy conditions... but it might not work very well if they are inefficient at below-freezing temperatures.

I thought about the two fridge set up. I had a 20 something (qt/ltr) Alpicool that I played with freezing bottled water. It took forever, I think maybe because it doesn't have a fan to circulate the air like a home freezer. And, the coolant runs inside the walls and bottles against the wall froze much faster than the ones in the middle.

 

[rruff]

Fans are nice for keeping the temperature uniform, but I think if it's taking forever that means it's running very inefficiently. Was the compressor on all the time?

 

[scaredycat72]

Lots of good info in this thread!

Your experience shows that not all cheap 12v refrigerators are are created equal. The Setpower's average power consumption was only ~10W while the Joytutus was ~31W ... which is worse than a lot of dorm fridges + inverter setups! In the 70F conditions you measured the Setpower would use ~250W-hr/day, and you'd need ~50W of solar (on average!) to replenish that, and 100W should give you a decent buffer.

As someone mentioned, the heat loss will be proportional to the difference in temperature between the air outside the fridge vs inside. You said it was set at 25F, but if nothing was freezing inside, it would have actually been 32 or greater. So a temperature differential of 38F or less. I'll rarely be camping where the average temperature during the day is 70F or more. In winter ~55F is more like it.

It sounds like these fridges might not operate efficiently at below-freezing temperatures. I had a bright idea to get a small one just to freeze ice when there was excess sun, then use the ice in a good cooler. This would eliminate the need for added battery capacity and give you a good buffer for cloudy conditions... but it might not work very well if they are inefficient at below-freezing temperatures.

The temperature inside my Setpower varied from 17 degrees to 32 degrees. I don't think it would have had a problem freezing anything.

 

[rruff]

The temperature inside my Setpower varied from 17 degrees to 32 degrees. I don't think it would have had a problem freezing anything.

Did you measure it with a separate thermometer? I looked at the reviews on those, and many people mentioned that the temperature read out was optimistic. Seems to be common for the cheaper fridges. At any rate the performance was quite good... thanks for the info!

 

[scaredycat72]

Did you measure it with a separate thermometer? I looked at the reviews on those, and many people mentioned that the temperature read out was optimistic. Seems to be common for the cheaper fridges. At any rate the performance was quite good... thanks for the info!

Yes, I did. The 17 to 32 degrees is what the thermometer I placed inside read when I set the temp to 25. I ignored the refrigerator's display temperature because it was consistently inaccurate. All of the 12 volt refrigerators I've looked at - Setpower, Joytutus, Bodega, and Iceco - are capable of making ice and freezing foods.

 

[rruff]

It's even more efficient than I thought, then.

 

[technerd88]

These don't really use much. I don't even notice it on my huge lifepo4 bank. Mine uses 20ah a 24 hour period and it's set for 24f. It's a 60 quart one. I have 1200ah so I don't even notice the thing. My laptop alone uses 200ah a day so 20 is really nothing. I measured it using my victron bmv712

 

[rruff]

My laptop alone uses 200ah a day

Are you mining on it?

 

[StarryNights]

I have a large 130 liter Truckfridge (TF130) that uses about 55W when running. Overnight, with no solar charging, my 100 amp 24V LiFeP04 battery (same as 200 amps @ 12V) drops about 0.9% per hour with just the fridge and some light draw electronics (0.30 amp) connected. Amps and percent measurement from Aili current meter shunt. Example: battery at 91% at 11PM was 82.5% at 8am next morning.

 

[bpdchief]

I've run an Edgestar FP430 fridge on a 200 watts solar / 200 Ah battery system since Feb 2017 with no problems. Now I realize it's got to be near the end of it's lifespan, but, paid $459 for it and am on it's 5th year - got my use out of it. It has stayed cold all this time, I never worried over how much power it or two LED lights and a Caframo 12v fan used... I'm not techy enough to be concerned beyond "It works and I'm happy".