Whether you’re heading out for the weekend or spending months in an RV, you need a way to keep your food cold. Unfortunately, getting a fridge to run off of 12V is a little challenging. Researching the topic tends to bring up more question than it answers.
For now, let’s forget about all the small details. If you want to keep your food cold on the road, you’ve got three basic options.
Option 1: 12V Coolers
- Plug directly into your cigarette lighter
- Can run off car battery
Most cheap 12V coolers aren’t worth your time. They work well in theory, but just don’t hold out in the real world. The improvements over a standard cooler was barely measurable.
That being said, there are still a few models that are worth considering. The Koolatron P75 is well reviewed, and reasonably priced. In the short term, it can work really well. This would be the ideal choice for a weekend camping trip, or a few days out at the lake. You do have to treat it like a cooler. It needs ice, and it needs to be plugged in. Check out buyer read the reviews on amazon to see how people made it work for their situation.
This is what they call a thermoelectric cooler. It operates on the “peltier effect.” When current runs through two dissimilar metals, the heat is removed from one and then pulled into the other. This cooler is packed with tiny little cubes that wrap around the inside of the cooler, behind the insulation. Only a very small amount of current is needed, and an impenetrable wall of chilly metal keeps your cooler from warming up. To put it simply, this is basically a bunch if tiny metal cubes inside of a cooler. When you plug it in, they get chilly.
This cooler is suitable for anyone who’s needs to keep their food cold for about 12 to 24 hours. Basically, it doubles the life of your ice. Plus, since it uses very little electricity, you can run it directly off your cigarette lighter. This makes it great for days down at the beach, or a quick fishing trip.
Option 2: 12V Compression Fridge
If you want your food to stay cold for 24 hours or more, you’ll want to spend the money on something that works. When properly set up, ARB fridges perform just as well as the one in your home.
The main advantage is the efficiency. They’ll typically consumer around 10 amp hours per day, on a 12V system. This means that a standard deep cycle battery can keep this running for five days, even without any sunlight.
What’s unique about these solutions is that they use special compressors that are designed from the ground up to be run on 12V DC electricity. The current king of 12V refrigerators is the ARB 50 Quart RM series. It’s not cheap, but when you want to keep food cold for a long time it’s your best option. To understand what makes it so great, let’s compare it to a standard mini-fridge.
Your typical mini fridge draws about 20 amps at 12V, more or less continually. To start the compressor, it briefly draws a very large amount of power, usually 1500 watts. Your typical RV deep cycle battery can hold about 100 amp hours. This means that you can only run a mini fridge for an hour or two.
The ARB 12V refrigerator has a low turnover compressor. It doesn’t require any high current surges to start, and the total current draw is only 0.87 amps per hour.
You can run it for five days on a single deep cycle battery without charging it. If you want to make it last longer, you can pop up a single 50W solar panel or drive your vehicle for 10 minutes to get enough charge to run the fridge for the entire day.
In terms of functionality, the ARB fridge is the ideal solution. The issue, for most people, is the price. It’s not easy to find locally, and most vendors charge a pretty high markup. If you’ve got cash to burn, check out a boating store. Sail boaters often use these fridges. If you’re willing to ship it, Amazon usually has it in stock. If you’re lucky, you can catch them on sale from time to time.
Although expensive, the design makes it clear that you’re getting your money’s worth. No other fridge on the market is anywhere near this effecient. This is a chest style fridge, it opens from the top. When you open the door of a standard front facing fridge, all the cold air falls out and the compressor has to start. When you open this one, it remains cold.
It’s 50-quart capacity means that it can hold 72 beers, or a heck of a lot of food. For longer storage of frozen goods, you can drop the temperature down to -1 degree Celsius for a true RV freezer.
These units are designed to take a beating. Did you know that you can damage a regular fridge by laying it down? The same is true for portable models. But the ARB 12v refrigerator is designed to be bounced around, making it the perfect companion to any RV.
Option 3: Diy 12V refrigerator
The ARB fridge is world class, and it’s certainly the easiest way to get a fridge set up in your RV. But if you’re reading shedheads, you’re likely the type of guy who likes to get things done himself. This project will allow you to make your own ARB style fridge for only 200 bucks. And the best part of all? You can get it done in an hour.
Remember, what made the ARB fridge great was the fact that it was well insulted, the compressor required very little load, and it had a light duty cycle so the compressor was off most of the time. And of course, it was top loaded.
An apartment freezer is very similar to the ARB 12V refrigerator. Since it’s designed to be kept below 0 degrees, the walls are generally very well insulated. Compressing coolant to the point of reaching subzero temperatures is very challenging. If you ran these compressors all the time, they’d very quickly burn out. To correct this, manufacturers run them on a 25% duty cycle. Every hour, it’s only supposed to work for 15 minutes.
The first step was to find a freezer that used very little current. This wasn’t easy. Most manufacturers don’t publish the true power use, only their useless energy star ratings. After digging through a few that were drawing upwards of 3 amps (yikes!) we finally came across the Midea WHS-129C1. It was almost perfect. 3.5 cubic feet of space, a low foot print, and it only draws 1.1A while running! Plus, there is a two-year warranty on the compressor. These are the most common points of failure, and the fact that there was a warranty indicated to us that it was a reliable unit.
After ordering it, we opened the package and checked it out. It was nice and spacious, very well insulated for the price, and the compressor was rated for at least twice the duty cycle. After plugging it in, we ran it on a kill-a-watt meter for a few days. 1.5 kilowatts per day, not too shabby!
The next step is to turn it into a fridge. Basically, these freezers have little controllers in them. When the temperature is around -4, they shut off the compressor. It slowly warms up to 0, and the compressor kicks on again. Obviously, this won’t work for us. For a couple of bucks, we picked up the Inkbird Dual Stage Digital Temperature Controller.
This handy little controller lets us control the temperature ourselves. You can buy dedicated fridge controllers, but these are usually sold at 10x the price. This is a more advanced device, and will let us do the exact same thing.
The first step is to wire it up. We removed the end from an extension cord to reveal the three wires. You’ve got a hot (red wire), and neutral (black wire), and a ground (green wire). Follow the diagram above to wire it up.
The first thing you’ll connect is your hot lead. Take the red wire and connect it to pin 1, and connect the black wire to pin 2. You are now going to take a small length of wire and shove that into the connector for pin 1 along with your hot lead, then connect the other side to pin 7. Your next jumper will connect from pin 2 to the neutral lead on your freezer. The next jumper goes from pin 8 to the hot lead on your fridge. Finally, you’ll want to connect the ground from the freezer to the ground on your extension cord.
Power on the controller and press the S button. Next to the “cool” value select the number 4, and next to the heat select 0. Finally, turn the setting knob on the freezer to the highest value.
This might seem complicated at first, but it’s very simple. The controller stands between your freezer and the power source. When the freezer is on, it wants to get as cold as possible as fast as possible. The temperature controller has a long cord with a thermometer inside of it. You drop that in the freezer and close the lid. If the temperature inside is four degrees or above, the power is turned on. Once the temperature hit’s 0, the 12V refrigerator is turned off. Now you’ve got a fridge.
Remember, the duty cycle of the compressor was 15 minutes. But that was to freeze it. With our controller in line, it only runs for about 6 minutes per hour. At 12V DC, the compressor draws 10 amps. Since it only runs for 1/10th of an hour, we’re using 24 amp hours per day. Your 100 AH deep cycle battery can run this fridge for almost 4 days without a single recharge, comparable to the ARB.
Overall, this is a very affordable way to get a 12V refrigerator. But if you’re willing to spend a little extra, you can get a very professional finish that performs a little better than the DIY option.