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. Fortunately, there are a number of options out there.
12 Volt Refrigerator Buyers Guide
Sadly, keeping food chilly in your car or camper isn’t as easy as plugging a bar fridge into an inverter. Instead, you have three different options to choose from.
The cheapest option is to get an electrically assisted cooler. These work much like normal coolers, but a small trickle of electricity helps to keep your ice frozen for a much longer period of time. This is great for the odd weekend out, but it’s a suitable full-time solution.
In many cases, a proper 12 volt compression refrigerator is the best option. These come with a hefty price tag, although it is still cheaper than the fridge you have in your kitchen. What your money buys you is a surefire way to keep food cold (or frozen) while using very little power. These devices can easily be run off of your cars starter battery, or even off a very modest solar system. Additionally, they’re designed to take the bumps and scrapes that come along with life on the road.
Even if you don’t have the scratch for a commercially available 12 volt fridge, with a little elbow grease you can get something just as good. We’ll show you how to build your own by modifying a 120 volt unit. The project is easy enough to be completed by anyone with a little basic hand tool experience, and from a functionality perspective it works just as well. It’s a little bulkier, and not quite as sleek. But it’s 80% cheaper than commercial options, making it a great option for your rural cabin or RV.
A Primer on Refrigeration
Before we get into the nitty gritty details, it’s important to have a basic understanding of how fridges work. At the heart of the fridge is something called refrigerant.
If you want to skip the wall of text, this video does a pretty good job of explaining the basics:
Imagine a boiling kettle. A kettle adds heat energy to water, eventually turning the liquid water into a gas: steam. The refrigerant is another chemical (historically, freon was used) that is liquid at very cold temperatures and a gas at room temperature.
All of this refrigerant is stored in a system of pipes and tubes. At the core of this loop is something called a compressor. The compressor pressurizes the gas until it becomes liquid. The liquid refrigerant then leaves the compressor into the evaporator tube. This evaporator is located inside the walls of your fridge. Just as water absorbs heat from the kettle when it boils, as the refrigerant turns back into a gas it sucks out all of the heat from your fridge. Warmed up coolant then flows down the evaporator tubes into the condenser, where it waits to be recompressed by the compressor.
This is the basic premise behind the fridge if your home. But all of these fridges run off 120V alternating current. Compressors require a LOT of energy to run. If you tried to run this directly off of your car battery with a little inverter, your battery would die in a matter of minutes. For this very reason, manufacturers had to get really creative when designing a cooler that could run off low voltage DC energy.
When it comes to keeping your food cool while on the go, you have three different options. Each of these options has their own sets of pros and cons. We’ll go through each type of cooler one by one and help you find the type that’s right for you. Afterward, we’ll show you our favorite models in every category.
Option 1: Thermoelectric 12V Cooler
These types of coolers are cheap enough that they could be considered a reasonable impulse buy. Generally priced in the low three figures (with some even cheaper models!) many consumers just decide to try it out before investing hundreds in a high-end model. They look a lot more like your standard cooler, and are often sold as an upgrade to standard ice-fueled coolers.
They Plug Directly Into Your Cigarette Lighter
You don’t have to do any fancy wiring, and you don’t have to spend any time installing them. Just throw them into your vehicle of choice, slap the plug into a standard 12V outlet, and drive away.
They Can Run Off a Standard Car Battery
Even though your standard car battery is 12 volts, not every 12V appliance will run off of it. Car batteries hold a lot of power, but something as simple as leaving your dome light on overnight can kill them. This is because starter batteries are designed for short bursts of high current output – exactly what’s required to start your car. Drawing small amounts of current over a long periods of time can leave your battery drained very quickly. This is why most 12 volt appliances require something called a “deep cycle” battery that is designed to be discharged for long periods of time. While this is generally a rule, with thermoelectric coolers you don’t need any special battery to run.
The downside of these coolers is that you can’t expect them to work like a fridge. Refridgerators run off of compressors, but 12-volt coolers use something called Peltier cubes.
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.
In the real world, most cheap 12 volt coolers aren’t worth their weight in salt. Models skimp out on peltiers (which can be expensive!) and you’re left with something that doesn’t work any better than a standard ice-filled cooler. However, there are still a few models that make suitable refrigerators for cars.
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. The power simply helps the ice last longer. A standard cooler that might only keep your food cool for 6 hours could get 12 hours of a peltier cooler. Check out buyer read the reviews on amazon to see how people made it work for their situation.
This cooler is suitable for anyone who 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.
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Option 2: 12V Car Refrigerator
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. If you have an RV with a solar system, you can keep it running indefinately.
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.
ARB fridges are the best option for anyone who needs a long term food-storage solution. It’s a popular choice among overlanders, vandwellers, or RV enthusiasts. ARB fridges are also found in off-grid applications with solar installations. If your needs are a little more simple, it still makes a great camping fridge!
If you need a cheaper option, consider a Whynter fridge. These units have dual compartments so you get both a fridge and a freezer. They’re quite durable, although they take a little more space than an ARB model. Some consumers have found that they aren’t quite as power efficient, although the difference is really negligible when you consider the amazing cost-savings.
One of the things we really liked about the Whynter option is just how well the freezer works. It’s even cold enough to make ice cubes! Whether you’re looking for a way to store your catches on a fishing expedition, or just want to have some meat on hand for your next camping trip, this unit is well worth the investment for any serious outdoorsman.
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Option 3: Diy 12 volt 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.
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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.
The last thing you’ll need is an inverter. Both the temperature controller and the fridge itself sit on the 120V side of the circuit. What an inverter does is convert your 12V DC electrical source into a 120V AC source. There is, however, one big catch with the inverter. If the fridge only draws 10 amps, then in theory you’ll only need a 120 watt inverter. But there is a very brief moment where the inverter pulls a very high amperage when the compressor first starts to turn over, for that reason, we recommend getting a 500 watt inverter minimum, or 1000 watt if you want to run other things on the circuit.
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.