Properly use an RV battery disconnect switch

How to Properly Use an RV Battery Disconnect Switch

Do you own an RV but don’t know what a battery disconnect switch is and when you should use it?

You’re not alone, as this lesser-known feature on many RVs can lead to confusion about its proper use to cut off power between your campers 12-volt lights and appliances and the battery bank.

To clear up all the questions you may have about an RV battery disconnect switch, I put all the info right here where I detail:

  • The purpose of a battery disconnect switch
  • The location of the RV battery disconnect switch
  • How and when to use the disconnect switch for best results
  • If your RV needs a battery disconnect switch
  • How to install an RV battery disconnect switch

When you understand all the aspects of what a disconnect switch does for your camper, you’ll be able to use it to extend the lifespan of your RV’s batteries!

How Does a Battery Disconnect Switch Work?

A man working with a battery disconnect switch

Think of the RV battery disconnect switch as a backward fuse in your electrical breaker box.

Flip it “off” to allow power to run to outlets, lights, or appliance power boards through the electrical wiring, or flip it “on” to shut down power flow.

In the instance of a battery disconnection switch, the power isn’t 110-volt like your breaker box but instead is the 12-volt power your RV’s house batteries generate.

The switch is a convenient way to terminate your batteries’ power, reaching power panels and lights inside your RV. When the control is on, it stops any power from the converter from charging your camper’s house battery.

Without the switch, the only way to stop power from going in or out of the RV battery is to disconnect the main battery cable from the posts manually.

Should the Battery Disconnect Be On or Off?

The battery disconnect on-or-off position debate is a hot topic in RV forums, but the answer is straightforward.

The switch for battery disconnect should be in the off position most of the time.

The confusion many new RVers have about the battery disconnect switch is that the “on” position turns off the 12-volt power flow and that when connected to shore power, they don’t think they need to use the battery for power.

This idea is somewhat true, but most RVs require both shore power and 12-volt power to operate certain appliances such as the:

  • Refrigerator
  • Water pump
  • Furnace
  • Some air conditioners

When 120-volt power isn’t available, the current from the 12-volt system is enough to keep appliance module boards working and to spark your propane system to fire up to operate the water heater or furnace.

Some appliances may still not work if your battery disconnect switch is on and you’re onshore power.

RV refrigerators are notorious for the 12-volt display panel that must have power to trigger the 120-volt-powered compressor to run, so your food stays cold.

Being plugged in at a campground only to have your fridge go kaput because you’re having 12-volt battery issues is beyond annoying.

Some recreational vehicles have lights only wired to the 12-volt system. If you switch on your battery disconnect, the lights won’t work even if you plug into 120-volt power.

Do RV Batteries Charge When Plugged Into Shore Power?

An RV batterie charge

Yes, the house battery inside your camper uses shore power to charge.

The converter will take incoming 120-volt power, lower it to a safe level, and then send it over to charge your RV battery.

If you turn on your battery disconnect switch, you’re preventing the battery from charging. A dead or low-power battery will cause issues once you disconnect from shore power and try to use lights or start your furnace.

A quality RV converter with several stages is the best way to keep your house battery at full charge without worry it will boil over during connection to shore power.

When to Use the Battery Disconnect Switch

The only time you need to turn off power to the batteries by switching your disconnect “on” is when you’re storing your RV or not planning to use it for over a week.

You may also need to cut power to the house batteries if working on your RV’s appliances or electrical system.

12-volt batteries slowly drain down over time, even when not actively in use. There’s typically a parasitic load pulling small amounts of 12-volt power, such as from amplifiers for the TV antenna or carbon monoxide detectors.

By switching off the power flow, you can keep your house battery from draining down too quickly during long periods of non-use, as well as preventing battery overcharge if you plug your RV in during times of storage.

Some people prefer to plug in their RV between uses, but be aware that converters can go bad and lead to battery overloads.

A battery that runs down too low or overcharges will fail, resulting in an expensive replacement or possible damage to your camper’s deep-cycle batteries if they boil over.

Using the battery cut-off switch is another tool for proper RV battery maintenance that all owners need to follow.

Should the Disconnect Switch Be on or off While Towing?

Battery power is critical when towing a travel trailer, so you should never have the disconnect switch in the “on” position while traveling.

If an emergency arises and the trailer unhooks from the tow vehicle, the trailer’s electric brakes cannot activate without 12-volt power.

If the disconnect switch is on, the trailer’s batteries will also not gain charging power from the tow vehicle during travel.

Do You Use the Battery Disconnect if Your RV Has Solar Panels?

RV solar panels

RVs with solar panels rely on their batteries more than those who spend most of their time camping while using shore power.

Many people who prefer dry camping often install solar panels to allow longer trips off-grid, so keeping house batteries at full charge is crucial.

If you turn the battery disconnect switch on, no power will flow from your solar panels to your battery bank.

The best solution for RVs with solar panels is to use a battery tender in conjunction with your solar panel system controller to allow batteries to take in as much power as possible without the worry of overload.

Where Is the RV Battery Disconnect Switch?

The RV battery disconnect switch location depends on the type and model of camper you have and whether or not it came standard or was an add-on part.

Inside the Camper:

Look for labels with “battery” or “battery disconnect” inside the RV near a red switch.

The switch is often by your other power panel components or otherwise set in a cabinet or wall in the area near the battery compartment.

Inside the Battery Compartment:

The switch for the battery disconnect is often inside the storage compartment that houses the RV’s batteries. Most often, this compartment has an exterior door that is near the rear of your motorhome or travel trailer.

Sometimes batteries on smaller trailers are on the front of the camper above the hitch. The battery may be inside a metal or thick plastic bin, with the switch on the outside for quick access.

On the battery bank:

On most after-market disconnect switch installation, you’ll find the component directly on one of the batteries in the bank (if you have more than one.)

The switch may have a knob or a lever you twist or pull into the “on” position. Depending on the switch’s design and space on the battery, the controller will be sitting directly on top or next to the battery’s negative or positive terminal.

Depending on the number of house batteries you have in your camper and how they connect may also determine where to find the switch.

As a general rule, look for the disconnect component in the negative cabling line because this is an excellent place to create a grounding break between the battery and RV chassis.

If you don’t spot the controller after a good search, remember that not all recreational vehicles have a battery disconnect switch. The good news is that you can easily install one if you wish and the disconnect kits are very affordable.

Do You Need an RV Battery Disconnect Switch?

An RV battery disconnect switch

A battery disconnect switch isn’t a requirement, but it sure is a handy way to:

  • Prevent accidental battery discharge
  • Avoid battery overload
  • Maintain the integrity of your RV battery
  • Eliminates the hassle of manually detaching battery cables to cut power flow

Access to the batteries in many RVs can be challenging.

Most RVs have the batteries inside a solid container bolted to the floor to prevent it from tipping over. The batteries are often set back into the compartment to allow more room for storage.

Trying to get into the tight compartment space or lift out a heavy battery from the container to access the cables and posts to control battery power is not easy, so having a disconnect switch is a much easier option.

How to Install an RV Battery Disconnect Switch

DIYing an RV battery disconnection switch isn’t complicated, but if you feel uneasy, hire a professional mechanic to handle the task.

Dealing with even 12-volt power can cause sparks, shocks, or burns if you don’t know what you’re doing. Use eye and hand protection for DIY installation to be safe.

Another thing to consider during the switch installation is to spend a few minutes inspecting and cleaning off any debris or corrosion from all your battery terminals to ensure good connections.

Step 1. Buy the Right Switch and Cables for Your RV’s Battery Load

Find the voltage output of your house battery bank and purchase a disconnect switch the matches the rating.

If you don’t buy the right switch, it could fail during use, causing RV electrical problems that you may not immediately blame on a faulty switch.

Depending on the installation location of the new switch, you may need to purchase longer battery cables. Make sure you plan out where your controller is going so you can have everything you need on hand to complete the job.

Step 2. Disconnect the RV Battery

An RV battery

Find the cables on disconnect switch posts, and using a wrench, remove the ones that bring power into the battery bank and the one that will attach to your disconnect switch.

For safety, always remove the negative cable first from the battery and reinstall them last to avoid shorts.

Check out this helpful post on where to attach the disconnect switch in multi-battery RVs.

Step 3. Disconnect the Negative Cable Terminal and Wire the Switch

After you remove the terminal from the negative post, you can install the cable switch between the battery terminal and the line heading into your camper’s converter box.

Follow directions in the specific disconnect switch you purchase to hook it into the cable line. Make sure the control is in the “on” position during the install.

Some disconnect switches are directly installed onto the positive battery post and do not require mounting, as shown in this video on how to install an RV disconnect switch.

Step 4. Mount the Battery Disconnect Switch in the RV

Before you hook the cables back onto the RV battery, mount the battery cut-off switch in a convenient location so you can quickly turn the coach batteries on or off.

Many people attach it to a sidewall inside the battery compartment. In contrast, others prefer to drill a hole and mount it for access inside the camper or outside the large battery housing box on travel trailers.

Step 5. Reattach the Terminal to the RV Battery Negative Post

With the switch in place and mounted, you now need to take the end and reattach the terminal to the negative battery post.

Double-check the switch is still in the “on” position to prevent any power flow until you are ready.

Step 6. Reattach the RV Battery Cables to the Poles and Test Switch

Lastly, reattach the loose cables to the poles (positive and negative that you took off) in the proper positions.

Turn the switch to “off” to allow power to run through the battery and test to ensure it’s working correctly by seeing if 12-volt lights inside your camper work while not plugged into shore power.

How to Install an RV Battery Disconnect (Video)

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Final Thoughts

An RV camping on a beach

The battery disconnect switch is a simple tool to optimize the health and longevity of your camper’s battery.

The RV battery disconnect switch isn’t a complicated feature when you understand how it works and the best time to use it.

I hope this guide clarifies the purpose of the battery cut-off switch and helps you install one if your RV doesn’t have one in place.

Everyone wants to spend more time enjoying camping trips, so keeping your RV’s batteries in top condition by using a disconnect switch correctly is a smart move!

QUOTE:
"Man cannot discover new oceans unless he has the courage to lose sight of the shore."
-- Andre Gide

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