I’ve had “12V Refrigerators” for 30 years in various forms. I’ve had thermo-electric coolers (also called a Peltier device) that can cool and heat by switching the polarity. These units are as ineffective as they are power-hungry. You can buy these for under $100, if you have a constant source of power and don’t mind the heavy amperage draw (while driving, your alternator will handle the load), they will “eventually” cool your drinks, but the maximum temperature drop is about 40 degrees below the surrounding temperature. I’ve never seen one that worked like a true 12 volt refrigerator.
I think I still have an old one in my attic that has gone unused for years (For good reason). If you put cold drinks/food into one, they will struggle to keep them cold, but if you put warm drinks in, you’ll likely get to your destination before they get comfortably cold enough to be satisfying.
3 Way 12V Portable Refrigerator
Then there’s the “3-way” fridge. These units are typically called “absorption” units that have no moving parts at all. They use a heat source (120VAC/12VDC/Propane flame) to heat a boiler that converts the contents to “absorb heat” usually in the freezer compartment. They work on the theory that absorbing heat makes the chill pate cold. These fridges are only efficient in the propane flame mode, but they still require a good amount of propane and a long time to “absorb” heat from the fridge’s contents. Propane, being heavier than air, is a poor option for enclosed spaces such as boats, tents or the inside of trailers/small spaces.
RVs with built-in 3-way fridges are vented to the outside to prevent carbon monoxide build-up. Some manufactures use only 120VAC and Propane (effectively a 2-way fridge), because the power draw on 12VDC will kill a battery in no time. I still have one of these in a travel trailer. It usually takes 24 hours to get cold, so best not to put certain perishable foods into that fridge until it is below 40 degrees “F”. I only run this fridge on propane, as I tested the unit’s power draw on A/C.
Recall that when using electricity, the boiler is heated by an electrical element rather than the propane flame. Using electricity is a very inefficient form of heating, but it works. I was astonished to see that the unit was using 305 watts for every hour of operation. No wonder this unit didn’t offer a 12vdc option; at 305 watts, the draw would be ~25 AMPS per hour!
The “Freon” Compressor is still the king. That’s why your household fridge is compressor-driven. No surprise here. My first true compressor-driven fridge on my boat was 12vdc. I was a happy guy. Worked just like my fridge at home. It could make ice and keep the temperatures out of the danger zone. Although it worked on 12vdc, it used a converter to run the compressor on 120VAC. I kept an “8D” 225 AMP battery on board to run that fridge. Even though this 150 lb battery was designed for deep cycling, it would only run that fridge for less than 2 days.
These have been the options, UNTIL NOW. These new Bilt-Tuff 12V Refrigerators are a true 12-24vdc compressor made efficient through the application of the latest technology. Like comparing a standard light-bulb to a LED, the difference in power consumption is incredible. Putting this fridge to the test, I ran a power consumption test over a three-week period. The fridge was filled with room temperature water bottles and started like any frige, it takes an internal sensor to trigger the compressor.
I was amazed at how fast the unit dropped the internal temperature, and once it reached 36 degrees, it held it there during the duration of the test. Wanting to control as many potential variables as I could, I placed the unit in my office that was holding a consistent 72 degrees. It was placed away from air ducts that might have also influenced the result. Drum roll please…how about 11 watts per hour over the entire three-week period! That is less than 1 AMP used per hour. Wow!!!
So what does that data plate on the unit say about consumption: On the 45 liter Bilt-Tuff 12 Volt Refrigerator, the consumption is listed as 45 watts and this makes sense as verified by my personal test result in real-world conditions. This is the running wattage, not the consumption per hour. Most fridges operate on a 30% duty cycle, so one could logically expect 15 watts per hour consumption. I’ll take either. I would assume that the fridge standing out in the full sun would cycle on and off a lot more frequently.
Additionally, I would expect that constantly removing and replacing items would introduce changing interior temperatures that would drive the consumption higher, or dialing down the temperature to below freezing would do the same thing, but the real important test is the comparison to the other modes of keeping your stuff cool. This unit is not only efficient, but very effective; a true winner in the world of keeping stuff cold.
HAPPY TRAILS!