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Ask Dave: Can I run my RV’s refrigerator on 12 volts while driving?

Dear Dave,
Can’t I run my RV’s refrigerator on 12 volts while running down the highway and turn off my propane tanks completely? —Fil Patrick Peterson

Dear Fil,
First, let me state that I think it’s important to shut off the propane container on your RV while driving down the road as you have stated. More on that in a previous article here.  The real question here is can your refrigerator actually run on just 12-volt power?

Running an RV’s refrigerator on 12-volt power

It depends on the type of refrigerator you have and the setup of your rig with house batteries and possibly an inverter. When I first started working at Winnebago in the early 1980s, the RV refrigerators were 3-way powered by 120-volt power with a heating element, LP using a flame, or 12-volt house power with a heating element. The 12-volt operation was very inefficient and did little more for temperature retention than shutting off the refrigerator and keeping the door closed. However, it drained the house battery in about four hours. Both Norcold and Dometic discontinued the 12-volt mode and offered only 120-volt or LP operation. If you have this type of refrigerator, you cannot operate it on 12-volt power running down the road.

What about an inverter?

Early on, I learned to never say “always” or “never” when it comes to the RV industry, as things change drastically every year. The absorption refrigerator that runs on LP or 120-volt power can be supplied with power from an inverter that takes 12-volt house battery power and provides 120-volt power to the outlet for the refrigerator. In this situation, the refrigerator would be running on the 120-volt mode, but powered by the inverter taking 12-volt DC power from the batteries. And, when you are traveling, the engine alternator from the tow vehicle or motorhome engine alternators will provide a charge to the house batteries, which will provide power to the inverter and provide power to the refrigerator.

Residential RV refrigerators

Some of the larger rigs are using a compressor-driven residential refrigerator that only runs on 120-volt power. However, I get questions and comments all the time that state their residential refrigerator runs off the 12-volt house batteries when they are not hooked to shoreline power and when they are running down the road. Technically that is true. However, they are drawing 12-volt power from a large bank of house batteries to the inverter that is providing 120-volt power to the refrigerator.

12-volt compressor refrigerators

There are several 12-volt compressor-driven refrigerators that have become popular such as Everchill that do actually run on 12-volt DC power only and are very popular in smaller units. They draw off the house battery only.

Charging the house batteries while driving

Okay, we’ve covered if and how a refrigerator can run off the 12-volt house batteries. Now let’s talk about how the batteries can be charged while driving. In the case of a motorhome, the system typically has a Battery Isolation Management System (BIM), which is a solenoid that is between the engine battery and the house batteries.

This solenoid provides a charge from the engine alternator to the house batteries typically at approximately 14 volts. It also has a switch on the dash that will provide a jump start from the house batteries if it is dead.

In the case of a truck and trailer, a plug-in with seven pins also provides a charge from the truck alternator to the house battery of the trailer. However, this does not have a switch to provide a jump to the truck from the house battery or batteries.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

Read more from Dave here

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Vanessa Simmons
6 months ago

I like having 1000watts of solar and two lithium batteries on my TT. I zip down the road using no propane to keep my fridge cold…as long as the sun is shining.

Bob Weinfurt
6 months ago

My 1977 MH has a three way Dometic fridge. There is a 20 Amp fuse in the 12 Volt feed wire. I always switch it over to 12 volts when I’m traveling, being sure to shut it off when the engine is not running. I don’t think that it would bring a warm refrigerator down to being cold but it seems to do OK keeping it cold.

Last edited 6 months ago by Bob Weinfurt
Bill
6 months ago

We’ve been using our 2000 Lance/Dometic 6cf since new in the ‘off’ mode while driving 2 to 6 hours per day in the Southwest. It can run on 12v while driving with the factory 10g wiring but we have never used the DC mode and have never been without ice cubes at the end of the drive. We never drive with propane in use.

James
6 months ago
Reply to  Bill

Our Norcold fridge is 2021 and still a 3-way! Runs fine with heavier wire (6 or 8 gauge) to camper plug. I would think that most truck campers have 3-way fridges from both Norcold & Dometic.

Brian
6 months ago

A lot of the efficiency issues with the 12 volt operation was due to the 12 gauge wiring the manufacturer’s used to connect them, often 15-30 feet of undersized wire causing a severe voltage drop and loss of watts which means a loss on cooling. Mine was seeing less than 11 volts with engine running and I was about 35% under the rating of the 12 volt element. Running #6 wire straight from the house batteries fixed it and now I get 13 volts while running and the full rated wattage out of my 12 volt element and improved 12 volt cooling on the road.

tom
6 months ago

WE do not do anything aimed at keeping the frig going while underway. We freeze bottled water and use it to keep things cold. Have never had a problem in 14 years of this method.

Robert Shaw
6 months ago

Two more factors to consider for an RV refrigerator while driving. Can the battery sustain the load from the inverter? And can an absorption refrigerator tolerate typical road tilts?

A 6′ tall Dometic refrigerator is rated at 2.7 A AC, with an 80% efficient inverter, this means about 33 A DC. My F150 limits the 7pin connector to less than 25 A DC, thus it might trip. If the coach battery was isolated it could run for hours. But if one were to run an extension cord from an F150’s small inverter to the refrigerator, it could supply the needed power.

Dave’s previous article implies bumpy and steep roads could be problematic for the flame in an absorption refrigerator while implying the fluid in the coils could withstand operating while in motion.

On the other hand, we move everything from our freezer down to the refrigerator unit while traveling and use time on the road to defrost the freezer. Items that need to stay frozen we put in insulated bags in the refrig.

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