DIY: How to make your own 12V Fridge

[BradKW]

That was a nice tour...video definitely give a different perspective over just photos. The Sharpie'd ceiling fooled me

Didn't you do a nice stenciled compass table too, or maybe I'm confusing people..?

 

[ViaVacavi]

That was a nice tour...video definitely give a different perspective over just photos. The Sharpie'd ceiling fooled me  

Didn't you do a nice stenciled compass table too, or maybe I'm confusing people..?

Yeah, this tour was a 2nd build I took on this year.

The tour of the Dodge you're referring to with the nautical compass stencil is coming soon, I think he said he's going to release it in a week or so

Tomorrow he's posting a video we made detailing the foam construction techniques a little better

 

[Kraken8r]

Ingenious! Love it!
Would I be correct in thinking this would work for a 12-240v conversion too?
Australian power is 240 volts...seems the only difference would possibly be using a 12-240v inverter of 1000w, instead of the 12-120v listed here.

 

[Trebor English]

I would expect the 50 - 60 cycle difference to not matter either. The compressor motor rpm will be different from 60 a cycle compressor but the 50 cycle appliance should work as well on 50 cycle that came from DC as it does on 50 cycle that came from a grid.

 

[Michael4104]

Thank you ViaVacavi for sharing your frig mod. I have almost completed the mod on my frig, but before finishing I would like to do the "make a simple inexpensive automatic transfer switch" you mention. Did you post it in another thread or is it coming here soon?

 

[pearll]

Why not just get an inverter, and run your 120 volt fridge off of it from your battery bank?

This certainly will work, and many people have done it.  However, it is the least efficient option.
Inverters are not 100% efficient, so power will be lost during the conversion from 12 volts DC to 120 volts AC.  This power loss is present whether the compressor in the fridge is running or not.  On most fridges, the compressor only has to run roughly 25% of the time (or even less), so it makes no sense to suffer this power loss 24 hours a day.  On a positive note, no special skills are needed and you just plug the refrigerator into the inverter at one end, and plug the inverter to a 12 volt socket at the other end.

Here is an example of the power needs for such a setup. 
This example will assume a fridge that uses 60 watts while running, where the compressor runs 25% of the time.  This will also assume that the inverter consumes 0.5 amps just being plugged in. (Of course in the real world, there are many factors that will influence efficiency)

• Running 6 hours per day, the compressor will consume 30 amp-hours from your battery bank (60 watts divided by 12 volts = 5 amps, multiplied by 6 hours equals 30 amp-hours)
• Running 24 hours per day, the inverter will consume 12 amp-hours from your battery bank (0.5 amps multiplied by 24 hours equals 12 amp-hours)
• This adds up to 42 amp-hours per day to run the fridge

A recent van conversion used a Midea  2.4 c ft fridge. Averaged 2.5 amps/hr + 1 amp for the inverter. Quite a bit more than a 12 v fridge but only costs $90.

 

[Carv]

ViaVacavi can you please update your account?

The photo bucket pics are not linking and I can not see how to wire this up.

I have a converted mini freezer that I'm running off an inverter and this set up would be perfect as my inverter uses 400watts a day and my fridge uses 360 Watts. This would cut down the inverter draw significantly since it wouldn't be running when the fridge isn't running.

Thanks

 

[ViaVacavi]

ViaVacavi can you please update your account?

The photo bucket pics are not linking and I can not see how to wire this up.  

I have a converted mini freezer that I'm running off an inverter and this set up would be perfect as my inverter uses 400watts a day and my fridge uses 360 Watts.  This would cut down the inverter draw significantly since it wouldn't be running when the fridge isn't running.

Thanks

Photobucket broke the Internet.. I certainly can't pay the $400/year they want to share photos (which has always to this point been free)!

Over the next several weeks I'll be moving my pictures to my own server as to not have them held hostage again by another company, then updating my posts.  Give me a few weeks!

On another note, the fridge continues to operate flawlessly and has seen some pretty harsh service on the road!

 

[Carv]

I was able to download your wiring set up pictures so I have a little better understanding of what I think you did here but I'm still little lost with my own set up, maybe you can help?

I by passed the freezer temp controller using a inkbrid 10A AC digital temp controller, I currently have it wired in to the fridge 120 circuit replacing the OEM thermostat so I can control the temp manually and it just acts as an AC switch.

My inverter I'm running the fridge off has sleep mode on it already and is woken out of sleep mode when there is a draw on AC system above a certain amount which I can set.  

My issue is; the inverter isn't supplying AC to the fridge since it is in sleep mode, so there is no power to run the digital temp controller to tell the fridge to kick on AND even if I could run the temp controller I'm not sure if the inverter would wake up since there is no AC to kick on the compressor to tell the inverter to wake up???  I believe I'm stick in some kind of no power loop?

I have thought about running the temp controller off DC but I'm not sure if 1) it can handle DC to power the unit (or if I'd have to get a DC rated controller) or 2) if my current temp controller unit's power circuit is separate from the switch/ relay circuit?  So I could run DC to power it and it would still switch AC?  But again, even if the power circuit is separate from the switch circuit I'm not sure if it'll "wake" the inverter since there is no AC being supplied until the inverter wakes up???  - chicken or egg here.

I don't want to switch/relay the DC power to the inverter as it needs to be fused with at least 200A (1.5k constant/3k surge inverter) so I'm not comfortable going that route.

Any idea how to get me out of my no power loop so I can use the inverters sleep mode to shut down  the inverter when fridge reaches lower temp limit but wake it back up when it reaches upper temp limit?

Thanks

 

[Carv]

Here are some pictures of my current set up

 

[Carv]

I found Your electrical diagram and the relay diagram this helped sort out how you structured it.

 

[Carv]

After looking this over, I have 2 questions:
1) what is red 87a connected to? Anything or is it just covered/ terminated at the relay?

2) what is BT battery that is connected to the fridge bundle black and white? Is this a 12v DC battery?

Thanks

 

[AquaticsLive]

Cool thread. Wanted to share my setup maybe someone may want to try this system. My inverter has a switch to turn it on and off I ran two wires to the back of the switch so I can control it remotely then I hooked them up to a 12V thermostat relay that I got from Amazon. So really simple process of having wires hooked up to the battery for 12V to power the controller and the two relay wires ran to the switch on the inverter. I have the temperature probe piece inside the fridge. The dorm fridge draws 428Watts for about 5 seconds then switches to 70 Watts. Cycles ever 28 minutes and runs 2 minutes.

Here is a link to the part I bought from amazon.
Wangdd22 W1209 -50-110°C 12V DC Digital Thermostat

 

[Trebor English]

Which fridge did you use?  Which inverter did you use?  How did you set the thermostat, what temperature and hysterisis?

 

[AquaticsLive]

I have:
Whynter CUF-210SS Freezer, 2.1 Cubic Feet
Mighty Max 1000w Pure Sine Wave Inverter.

The thermostat I just set it to 38 degrees (actually 3 degrees Celsius) it has a little relay on the board that energizes when it warms up to that temp. It stays on until it hits 32 degrees (actually 0 degrees Celsius) then turns off. It then takes about 28 minutes to warm up to 38 again and repeat. I didn't set the hysteresis but it has a 3 degree Celsius range; I had the thermostat from another electronics project and that is just how it worked already so just used what I had. I used a mini dorm freezer just because it has more insulation but think a regular mini fridge would work just as well with some extra insulation.

I have a hard start capacitor that I want to try adding to reduce the startup current I just put this together recently so just hopeful experiment that it works as good in the summer.

 

[bonvanroulez]

I have:
Whynter CUF-210SS Freezer, 2.1 Cubic Feet

What a coincidence, I have that very freezer! Mine has a different brand name but I believe it is the identical unit. Purchased from Amazon in early 2014 for $228 shipped.

I used this controller:
STC-1000 Digital Temperature Controller

I used a 120 volt controller so it runs from the inverter turned on 24/7. The inverter gets used for other things so I don't mind the little bit of extra draw. I also have the 12 volt version of that controller; last year I purchased another inverter to do a switched version but I wasn't happy with the new inverter and returned it. I may revisit that sometime, but I'm not at all unhappy with how it has performed.

My converted freezer is very efficient, I have recorded power consumption over an extended period and it is equally if not more efficient than a comparably sized 12 volt refrigerator. It is going on 4 years of full-time use in my van, over approximately 50,000 miles, a lot of really rugged backroads, and many, many, many miles of rough washboard roads and it performs perfectly.

 

[Trebor English]

My converted freezer is very efficient, I have recorded power consumption over an extended period 

Would you please share some use data?

 

[bonvanroulez]

Would you please share some use data?

I would be happy to. The data I collected was in 2015 so I need to review it to refresh my memory, also I have pictures of the Kill-a-watt numbers to verify, I will have to find them in my archives. So, I'll be back with that later.

 

[bonvanroulez]

Would you please share some use data?

Here it is…

As mentioned earlier, this is a 2.1 cubic foot, front opening freezer, converted for refrigerator duty with a digital temperature controller. The unit has very thick insulated walls. at least 2 1/2”, and a very heavy magnetic door gasket. The controller is set to turn the compressor on at 38 degrees, and shuts off just above 32 degrees, trying to maximize the cycle time. The compressor is a standard 120 volt, and the unit is powered by a 1500 watt sine wave inverter that's on 24/7.

I think worth mentioning, I don’t baby my fridge. I don’t worry about minimizing door openings. And in very hot weather I am frequently cycling liter bottles of ambient temp water into the fridge so I always have a cold drink available.

This information is based on data from a Kill-a-watt over a 2+ month period, 1,550 hours, or 64 1/2 days. The exif data on the original Kill-a-watt photos shows they were taken 08-12-15, subtracting from that shows the test started on 06-08-15.

The data began June 08, in middle Nebraska, with travel through Wyoming and Montana, and ending in eastern Washington on August 12. I mention the states to illustrate the climate. I recall that was a hot summer, and my van with roof mounted solar panels must be parked in full sun. During the days I may be away with the van closed up, side windows cracked and roof vent open, but 100+ degree temps inside the van would have been routine. So, I believe the temperature conditions for the test are higher than average.

The Kill-a-watt recorded usage of 18.16 kwh, or 18,160 watt/hours. divided by the 1550 hour period gives an hourly usage of 11.72 watt/hour. Obviously this doesn’t include the overhead of powering by inverter. I have verified many times that my inverter’s overhead is 12% to 15%, so using the higher number for worst case, adding 15% or 1.76 w/h to the 11.72 gives a total of 13.48 w/h. My batteries voltage runs from over 14 while charging during the day to slightly under 12.6 overnight, so using 12.6 volts as a very conservative average, the refrigerators net power consumption = 1.07 amp/hour.

I frequently see 1 amp/hour as something of a benchmark for good performance of a 12 volt refrigerator, but they are typically 45 quart chest-type coolers, where mine is equivalent 62 quart with a front door. And the 1 amp/hour benchmark is likely under much less extreme temperature conditions than I tested above.

I have done shorter term tests over 24-48 hours with the Kill-a-watt and have seen 10-11 w/h and even under 10 in more ideal cooler conditions. At 10 w/h, add inverter overhead and I get a figure of .91 amp/hour, or 21.9 amps over 24 hours. 

This is real no BS data, the numbers from the Kill-a-watt back it up and the exif data from the photos proves it was tested in hot summer ambient temperatures. I would like to repeat the long-term test in winter months in Arizona to get data in a best-case scenario.

 

[John61CT]

Total AH per day @ 12V would be ideal for comparison, using a shunt-based meter.