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
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.
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