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Should I Disconnect My RV Battery When Plugged In to Shore Power?

Should I Disconnect My RV Battery When Plugged In to Shore Power?

Because most RVs have two electrical systems – a 12V DC system as well as a 120V AC system – there can be some confusion about some matters related to the two systems and how they function, both together and separately. For example, we’ve often heard the question “Should I disconnect my RV battery when plugged in?” And that’s a great question. So, we thought we’d dedicate a post to the topic in hopes of clarifying a few important points.

Many rigs have an RV battery disconnect switch, and that’s a useful thing. But should you disconnect your RV’s battery when you plug your RV into shore power?

Let’s dig in and find out!

What is an RV Battery?

An RV battery – sometimes referred to as a “house battery” – runs the 12V systems in your RV, providing DC power to your rig’s electronics and devices.

Your RV’s 12V system (your rig’s house battery or battery bank) is capable of providing power to your RV’s lights, 12V outlets, vent fans, slideouts, water pump, and some appliances. That’s true even when you’re parked in the middle of the desert or forest, or on a beach with no way of plugging into a separate power source.

Your RV’s battery bank is one of the greatest things about your rig because it frees you to camp anywhere you want, while still having many modern conveniences that require electricity to function.

What is Shore Power?

The term “shore power” refers to any external power outlet that allows you to access the 120V AC portion of your RV’s electrical system. (AC power is what you typically find in the wall outlets of a house.)

When you have access to shore power, typically via a power pedestal at an RV park or campground, you can run a number of appliances that are more power-hungry, such as your microwave, air conditioner(2), and 120V power outlets.

Photo of a man plugging his RV into shore power at a campground

When your RV is plugged in to shore power, you’re able to power all of the appliances and outlets in your rig.

The same 120V AC power can also be available from an onboard or portable generator. While a “genny” isn’t normally referred to as “shore” power, it does provide the same 120V AC power as you get from plugging into a power pedestal.

Even though shore power is 120V AC, it can also power all of the things your 12V DC system can run. But how can 120V AC electricity power 12V DC accessories?

That’s where your RV converter comes in!

What is the Function of an RV Converter?

As the name implies, the function of an RV converter is to “convert” power. In the case of an RV, that’s converting 120V AC power to 12V DC power. This allows something very important to happen in addition to allowing you to power 12V appliances and devices using 120V AC power.

Your RV converter allows your 12V RV batteries to be charged when plugged into shore power. Those charged batteries are the reason why you’re able to use your RV’s 12V electrical system to power your RV when you’re NOT connected to shore power.

So, this is how you’re able to boondock. It’s why you can run the water pump when you’re parked on the beach, run your vent fans when you’re in a parking lot, and even turn on the lights late at night when you’re camping in the middle of the forest.

So, your RV converter is needed to recharge your batteries when you’re plugged into shore power, and also to power all of the DC components of your RV.

For more in-depth information, see our post on RV power converters.

Is My RV Battery Required to Run the 12V System When My RV is Plugged In?

Thanks to the job your converter is doing, you may not need to have a battery connected to run the 12V system when your RV is plugged into electricity. Some converters can work without one in the system (the separately supply 12V DC to the RV’s electrical system).

However, if you want your RV battery/batteries to charge while you’re plugged into shore power, your battery system does need to be connected.

But it’s also possible for a camper to have a converter in it (or that’s wired in a way) that doesn’t allow the system to work without a battery connected. In these situations, the RV’s 12V electrical loads are wired directly to the battery, and the converter/charger simply provides the power to maintain and/or charge the battery as needed. Your RV converter’s (and/or your RV’s) manual should note whether or not it will continue to supply 12-volt power to the RV’s 12V systems even when the battery is disconnected.

Should I Disconnect My RV Battery When Plugged into Shore Power?

So here we are – back at our original question: “Should I disconnect my RV battery when plugged into shore power?”

And generally, the answer is “No” for short periods of time, (say a month or less). However, for long-term storage, it may be a good idea, or even necessary, to disconnect your RV battery. That’s particularly true if your RV has an old converter/charger (or one that’s cheap/inefficient) that could overcharge the batteries while the rig is stored. In this case, you’d want to prevent overcharging by completely disconnecting (and, ideally, properly storing) the battery.

A stored RV covered in snow... should you disconnect the batteries?

If you store your RV for a long period of time (over the winter, for example), you may want to completely disconnect your house batteries. In very cold temps, you may even want to store them in a warmer location for the winter.

Even if you have a battery disconnect switch, you’d also want to disconnect your RV battery (at the terminals) under two other circumstances:

  1. If you don’t have access to shore power to maintain the battery’s charge while the RV is stored. Disconnecting the battery completely
  2. Your battery disconnect switch doesn’t stop ALL parasitic drains.

Many of your RV’s electronics will continue to draw a small amount of power (known as “parasitic drain”) even when they’re turned off. Disconnecting your battery/batteries will prevent this power draw. Your batteries will still discharge, though more slowly.

You may also have the option to keep your battery charged with the use of a separate smart charger.

But in most situations, your batteries should remain connected when your RV is connected to shore power, so that the battery remains fully charged. That’s how we handle it, since our RV is equipped with a charging system that we can depend on to safely trickle charge our batteries, even over long periods of time… we almost never turn our batteries off or disconnect them.

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Don Curton

Wednesday 8th of June 2022

On my travel trailer, I used to store it plugged into a 120v 15 amp circuit just to charge the batteries (with all appliances off). I would use a regular extension cord with various adaptors to get to the 50 amp RV plug. Unfortunately, the RV converter in my RV is either cheap or defective. It over-charged the batteries, boiled all the fluid out and ruined them. I've since replaced the batteries and installed an aftermarket disconnect switch that completely eliminates parasitic drain. I also use a separately (quality) battery charger hooked directly to the batteries when in storage. I'm very careful to never have both batteries and shore power going at the same time. I also check battery fluid and charge level before and after each trip. If you rely on the stock RV converter to charge your batteries, I'd suggest verifying the amp draw and charge level first because replacing batteries is very expensive.

Pat Parker

Sunday 5th of June 2022

Thanks for the clarification on this issue

Ben Hill

Sunday 5th of June 2022

Do Extended Warranty policies cover DIY repairs or do I have to go to a mechanic.

TheRVgeeks

Sunday 5th of June 2022

Good question, Ben. Unfortunately, it varies A LOT by policy. Some will. Some won't. If they do, they will likely have some fairly strict requirements for documenting the repair (since, otherwise, they wouldn't know if you just bought parts so you'd get the receipt, submitted it for the claim, and then returned the parts). Many handy RVers who prefer to DIY will either "self insure" (i.e. not have an extended warranty at all), or get a lower-level plan to cover catastrophic repairs (engine or transmission failure, for instance) that they don't use for claims for the stuff they can handle themselves. Reduces the cost of the extended warranty plan, but protects you from having to foot the bill for the big stuff.

Barbara Bailey

Sunday 5th of June 2022

Sorry for the dumb question, is 12 volt and 120 volt outlets the same thing?

TheRVgeeks

Sunday 5th of June 2022

No apology needed, Barbara (we're devout believers that the ONLY dumb question is the one not asked)!! No... 12V and 120V outlets are not the same thing. 120V outlets are for AC (alternating current) power like what you have in your house. They have the two narrow, vertical slots and (often/usually) a third rounded one centered beneath them. 12V outlets are for DC (direct current) power coming from your RV's batteries and/or converter. Your RV's lights, water pump, vent fans, and any other 12V DC systems are typically wired directly to the 12V DC power coming from the battery(ies). But you'll also find 12V outlets in random (seldom convenient) locations throughout your RV. They are the approximately 1" round hole that looks like the old cigarette lighter outlet in a car. Hope this helps!

Don M.

Sunday 5th of June 2022

Another item to note when talking batteries is dirty or noisy power. Just like having dirty (noisy) 120vac at power poles,, older converters may pass some of that to your 12v electronics. Batteries being large capacitors help to filter (and regulate) that 12v.

Steve at M4

Monday 6th of June 2022

@TheRVgeeks, I find the battery essential for a healthy system for this reason. Lesser LEDs will burn up do to this dirty power, think of it as almost a very fast power vibration in the DC power which causes electronic components to heat up. The reason lesser ones fail faster is the capacitor works as a little battery, but is overwhelmed. We use a larger capacitor which helps older systems (with a battery in place, you will still have some dirty power regardless). This is definitely not a problem solely with LEDs, but anything in the RV 12 volt electronics such as radios, electronically controlled fans (I lot of controller failures out there), or anything else with small caps. Even with our larger circuits though, with no battery in place, it can cause premature failures (which we still warranty, but try to educate the customer).

Just last week I had a customer where his adhesive on the back of plate lights was failing, but the LED was still working. This is abnormal because the adhesive tape is super strong. Long story short, he had no battery in place, the array was running very hot, and the heat was going after the adhesive. He installed a battery, replaced the adhesive, luckily the LEDs survived the abuse, and everything is working perfectly now.

I had another customer about 6 months ago with a newer 5th wheel and -converter- have his batteries stolen while in storage. He stores his 5th in the back of the same park he usually camps at, so he plugged in and figured he never is on battery power so he did not replace the batteries. He had 2 of 10 LEDs fail before he contacted me for tech help and we diagnosed the problem together. I instructed him to have one 12 volt battery, just big enough for the system to look at. He did this, we warranted the 2 LEDs, and he has had no problems since.

Not to make this post longer :-) but the same is true for dead batteries. If you are always on shore, remove all the dead batteries and install one smaller 12 volt to keep the system happy. A charger will throw a bunch of power trying to charge a dead battery which is not good for the rest of the 12 volt system. Also, if you every use a stand alone external automotive battery charger, turn off all of the electronics when you are using it, they are super destructive. I actually use one of those in house to torture test products.

I hope this clarifies my perspective.

TheRVgeeks

Sunday 5th of June 2022

Very true, Don. We may have to do a separate post about that (maybe a guest post with Steve from M4 LEDs, he's talked about that with us a lot over the years). MANY 12V RV converters/chargers seem to have "noisy" power output... so having that "filtered" through a battery is definitely a HUGE help in reducing/eliminating it.

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