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

[XERTYX]

So, I have seen a few videos where people measure their usage on 12v fridges.

The best case scenario I think I have ever seen is slim potatoheads review of the alpicool from a few years back. But I believe he measured it over the course of an hour or 2 compared his readings and then calculated daily draw.

I saw a video from like 3 years ago where a couple of Australian guys were having a fridge "shootout" over 24hrs and then repeated a second 24hrs after putting in a few room temp beers. 

They each were similar fridges, similar sizes, and higher end models. And they were like 10-16ah over a 24hr period. 

Similar to slim potatoheads review.

But I have seen a few fridges lately that say "only uses" ~1kwh per 24hrs. These are compressor fridges not thermoelectric. 

Then I saw Bob's recent review of the C40 whatever no name fridge and he showed a promo pic from their ad. 1kwh in 24hrs it said. 45w.

45w*24hr=1080wh 1080wh=1.08Kwh so are they giving the absolute worst case scenario in freezer mode? I know environment affects wattage. If its 120° its gonna be a power hog. If its 40° its gonna use almost nothing.

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

I'm seriously considering a fridge but I'm gonna go small Initially with my build. I can live without a fridge now as they aren't ridiculously expensive to add later. But I'd love to have one.

Even though we are approaching warm weather I'm planning to prioritize the install of a 12v diesel parking heater over installing a fridge.

I'd rather be warm in cool weather when it gets here than to be well prepared to keep cold cuts in the summer at this point, but if watt hours seem to be reasonable I'll definitely be installing one soon.

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.

 

[jonyjoe303]

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.  

 

[tx2sturgis]

Don't worry about all that...two 100 watt panels will do it.

 

[maki2]

Too much overthinking. Just put in enough solar panels and a big enough battery to keep a fridge running with some power left over for running a fan in summer and a heater in the winter. Dont size your electrical system for the least amount of cheap devices, give yourself some excess power. Remember you can always carry a small generator for backup power to top up your batteries if the weather gets extreme.

 

[XERTYX]

At 26f the fridge uses 18ah per 24 hours. 

Oh heck yeah! And that idea about venting really gives me something to think about. I have "stow-n-go" cubbies. I was thinking of putting the house battery and a fresh water tank under there.. and everything still might fit. 

I'm gonna measure the entire space and this may sound crazy but I was planning to drill a vent in there for a battery box enclosure anyway but if the fridge I'm looking at would fit under there it would be out of the way and I could vent it easily as well.

Don't worry about all that...two 100 watt panels will do it.

Yeah that's pretty well where my calculations based on others' experiences were leading. The only thing is I'd like to have some hard numbers to add some other loads. I'd like to be able to use a 300w rice cooker. They're very versatile. Also I've been eyeing a 32" smart LED tv that pulls 45 watts allegedly. I like big screens.

 

[crofter]

....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... 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....

I am also planning to add an inch and a half of insulation to the outside of my fridge (except the vents). Thanks for the info.
-crofter

 

[tx2sturgis]

My short simple answer pertains to the input power required (200 watts of solar able to catch normal amount of sunlight hours everyday, along with the controller and a couple of 12v batteries) to keep an average mid-size 12v compressor fridge powered up in average conditions. 

As soon as you add extra loads, or change the 'average' conditions (such as maybe camping under a tree canopy in high temperatures in the middle of summer) the answer changes.  

The point is you dont need to re-invent the wheel: we've done all the calculations, experimentation, and real world testing already. If you are just doing math and electrical formulas for the fun of it...well by golly...carry on!

 

[highdesertranger]

jonyjoe how is your water not freezing at 32°? Doesn't make sense. I think your thermometer/thermostat is way off. Highdesertranger

 

[XERTYX]

jonyjoe how is your water not freezing at 32°?  Doesn't make sense.  I think your thermometer/thermostat is way off.  Highdesertranger

HDR what I have read one the cheaper fridges is that you can set them to say 32° and it switches off at 32 (some also measure the temp outside of the interior) and within a few minutes the temp is back up to 42 or so.

Also some of them actually have a built in calibration to adjust the display to the actual temperature.

 

[XERTYX]

Well sadly any hopes of stowing a fridge with or without added foam insulation isnt realistic in my 06 caravan. The stow-n-go dimensions are 
46" across 25" front to back and 9.75 to 9.5 inches high.

I guess I'll still be able to store a fresh water tank and battery under there. With room leftover for other storage.

Under the bed is no option. Its only gonna be 8 inches high so i dont hit my head on the roof sitting at the kitchen table on a 6 inch mattress.

I'll have to keep brainstorming.

 

[jonyjoe303]

jonyjoe how is your water not freezing at 32°? Doesn't make sense.

I decided to check the temp with another thermometer, when the fridge reads 27f, my external thermometer with a probe reads 32f so its off by 5f. That might be why its not freezing.

The joytutu would probably not be good as a freezer, the few times I tried to get it to 8f, I couldn't do it. It was running constantly putting out alot of heat on a hot day, and even though I had a 220ah lifepo4 at the time, I wasn't willing to use 40+ah per day on the fridge.

Right now I have a 220ah lifepo4 batterybank to power my lights,swampcooler,fans, laptop and have a 312ah li-ion batterybank that runs the fridge exclusively. I got 2 batterybanks because last summer was hot, running the swampcooler all day/night plus the fridge was depleting my 220ah lifepo4 and the 240 watt solar panel couldnt keep up. Now I also replaced with a 365 watt panel. No more problems keeping the fridge running.

The fridge is a luxury, I had an edgestar 43L before but got rid of it due to its size and heat issues, I went 7 years without another one. But I do enjoy the cold water and storing cold cuts for sandwiches. Since I solved the power issues, the size issues and the heat issues, I'm keeping this fridge.

 

[PeterPiper]

I'm using a 1.7cu ft Galanz AC fridge from Walmart.  ($79.00)

I measured the power usage over a 10 hour period and it was manageable.  2.5 hours to replace that power with 0ne, 100watt Solar panel.

I'm adding a 2nd panel to bring that down to about an hour and 15 minutes.  Just over 500 watt hours to run it 24/7
Again, I can produce 200Watt hours per hour so around 2.5 hours to replace all that energy daily with 2 100watt panels.
That still leaves plenty to top up the batteries every day and still use some power for other things.
I think I could reduce that by at least 20% if I insulate the fridge better.

 

[scaredycat72]

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.

 

[JDub]

This is a shot of my Whynter 45Q's info sticker. I use a GOLAB solar battery to run it on the road (set at 38F) and have results similar to scaredycat's. I charge the GOLAB going down the road so it never run down, but use a panel to recharge if static and I switch to my much larger Wagan. Haven't a complaint in the world.

Cheers!

 

[Calaverasgrande]

I'd have to wait until I get back to my storage unit and can pull out my multimeter to get an accurate reading.
But my Setpower RV47 pulls only about 3-4 amps IIRC. I know I can go out camping with my 200AH bank on full charge and be good for a week no problem. And that is with a full fridge opened 3-4 times a day.
My inverter charging my laptop pulls more power.

When I get around to putting panels on the roof I'll be good indefinitely.

 

[Camper]

You use an inverter to charge your laptop? I bought a 12v car charger cord for mine and save the inverter power loss. That's like taking 12 volts and changing it to 120 volts and then back down again to 12 or 19 volts. Actually, my Dell laptop is 19 volts, but the car charger cord takes care of that in one step.

 

[Calaverasgrande]

It's an Apple laptop. So car chargers are less common. It's also one of the newest models with MagSafe 3 so there are not many 3rd party products at all yet. I've also had some negative experiences with 3rd party Apple power supplies.
I am working on getting everything else powered directly by regulated DC power adapters.
Going to build 6, 9 and 12V boxes for my music gear that uses DC.

 

[JDelete]

I have a Dometic CFX 35. The specs say it pulls 90 watts of power (when run on 12 volt).
I have a Bluetti power unit that has 1500 watt hours of capacity.
Doing the math on this, it comes out to 16 hours of run time on a full charge on the Bluetti.

It practice, however, I have gone five days and still had over half the charge left in the Bluetti and this was with also charging my cell phone off the Bluetti.

Why?

There are a lot of factors that go into this. For one, the cooler isn't running continuously. It cycles on and off depending on the temperature in the Dometic.

The temperature in the Dometic is highly dependent on the ambient temperature, how often and for how long the lid is opened (letting warm air in), is it sitting in the sun or shade, etc.

It also matters how low you have the temperature set on the cooler. I set mine to 37 degrees. I use mine as a cooler, not a freezer.

My plan is to add 200 watts of solar on the roof of my vehicle.

 

[gizmotron]

Going to build 6, 9 and 12V boxes for my music gear that uses DC.

That's a great idea. Do you know if there is a commercially built setup for those street musicians already? That's a great idea. I checked my junk. It's all different amp level 9vt with + or - center poles and the same at 12vt. I need 12vt DC center + at 1 amp and 15 watt max just to charge my Variax lithium battery. I have a couple of Korg Volca synths at 9vt center - that run fine off of typical stomp effect chargers. There's a 4 pad drum module that runs off of 12vt DC center + at 2 amps. I will also have the Boss-RC505mk2 when it comes out in about a month that runs on 9 volts. I wonder if all these different amp values can be too much? The wall bugs that run off of 110 AC have specific limits for each piece of gear. Then there is my speakers that both run off of 110 AC. This stuff does not draw that much. It's like having a big TV going.

 

[Calaverasgrande]

There are power bricks with regulated outputs, but they are expensive. And none that I have checked out have the specific combination of voltages I need. They also will have an overall amperage limit somewhere around 2.5-5 amps.
I have also always wanted to get into short run printed circuit boards. You can get about a dozen made for a couple bucks each.
All the low voltage through hole voltage regulators I'm looking at are the same footprint. As are the capacitors for each output.
So I just have to make one standardized board for my 6,9 and 12V outputs. The 12V will require a special part that costs a little more. Since the VR has a little bit of loss from doing it's job. A regular 12V regulator wants 14V or more to give you 12v.
So to be on the safe side I'm getting 12V VRs that only lose 3/4ths of a volt or so.

The other problem aside from headroom on power supplies is noise.
When I used cheap power supplies, like those one spot daisy chain things. I got a lot of noise from certain combinations of gear.
After a lot of futzing around I figured out certain pedals, drum machines and keyboards interfere with each other. The actual science is kind of boring, but I fixed it by only using regulated power for my stuff.

Back on topic. I checked my compressor fridge from my bluetooth battery app.
My Renogy 100AH batteries are the cheap ones that don't have data ports, but do have bluetooth.
(which is worse how exactly?)
The fridge draws approx 2.5 amps when cycling.
Volts times Amps = Watts.
12 x 2.5 = 30 watts when it is running, which is not often.
My setpower RV45S quotes as 85watts.
I'm on Eco mode and I have battery protection on medium, temp is set to 32, which in real world means more like 38.