How to Charge RV Batteries

On the list of Things That Can Go Wrong in an RV, a dead house battery is definitely somewhere near the top. For one thing, dead house batteries are terribly inconvenient. For another, letting your battery's charge drop too low can cause permanent (and expensive) damage!

Fortunately, there are a lot of ways to charge up batteries in your RV, camper, or trailer. We'll go over each method below so you can find the method that will work best for your RV situation, whether you're heading into the unknown landscape of boondocking, you're preparing to store your RV for winter hibernation, or you're brand new to RVing and just want to know how this whole battery thing works.

A note on battery health before we begin—always monitor your trailer battery's charge to ensure it doesn't drop below 50%. Dropping below a 50% charge will shorten the lifespan of the battery.

If you don't have a built-in indicator, consider purchasing a battery monitoring system to provide the status of your charge. Note that a half-charged 12V battery will put out somewhere between 12.2 to 12.6 volts (NOT 6 volts). A volts or more.

Do RV Batteries Charge when Plugged in to Shore Power?

Shore power (the 30-amp or 50-amp connections you'll find at campgrounds) will indeed charge your RV. This kind of connection will allow you to charge your battery and run your RV's appliances without fear of draining your battery. If you're camping somewhere in which shore power is an option, this is hands down the easiest way to keep your battery charged.

You can also plug into a 15-amp or 20-amp electrical outlet at home, as long as you have an adapter. (To learn more about shore power and when to use an adapter, check out our article here.)

Your 15- or 20-amp connection won't be quite sufficient to run all your appliances like you could at a campground, but you can at least keep a charged battery topped off for your next outing. To efficiently charge a depleted battery, you can use an AC to DC charger. If you go this route, we highly recommend using a "smart" charger that won't overcharge and damage your batteries, such as REDARC's BCDC.

Who Can Use Shore Power?

Anyone with access to an electrical hookup! If you've got it, use it. Shore power is one of the main perks of staying at a campground.

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Can You Charge an RV Battery from Your Vehicle?

One question we receive a lot about towable, trailer-style RVs is whether you can charge them using the powerhouse that is your tow vehicle (particularly whether or not you can charge your trailer while driving). The answer is yes—you can certainly use your vehicle alternator to charge your trailer, but the effectiveness of your charge depends on which method you use.

Option 1: Maintaining a Charge

If you just need to maintain an already charged battery while you're on the road, you can use the 7-way connection between your truck and trailer. Just run a 10-gauge power wire from the 12V terminal on the trailer 7-way to the trailer's positive battery terminal. However, keep in mind that 7-way connectors do NOT have an automatic shutoff, so you'll have to monitor your battery to make sure you don't overcharge and damage it.

You can use the 7-way connection while driving or while stationary, but if your 12V terminal stays live while your truck ignition is off, you'll need to either disconnect your 7-way while your truck is off, or use an isolator to prevent your trailer battery from sucking the life out of your truck battery. (You can use a circuit tester to check whether your 12V accessory terminal has power when your truck is off. Most factory 7-ways have a built-in isolator function, but most aftermarket 7-ways do not.)

Who Should Use a 7-Way Connection?

If you're going to be driving a lot and just need to keep your battery topped off between stops (but NOT charge it from a depleted state), this is the easiest solution. This probably means you have a more efficient method of charging your battery when you're not driving (such as a generator or shore power), which is why you only need to top it off while driving.

7-Way Connector Charging Trailer Battery

Option 2: Charging Battery from Depleted State

If you want to use your tow vehicle to actually charge up a depleted battery, you're going to need more than a 7-way connector. A true battery charger will provide the most efficient charge possible while putting minimal strain on your tow vehicle.

We highly recommend using a "smart" battery charger with:

An automatic shutoff feature to prevent overcharging
A built-in isolator to protect your tow vehicle battery from being drained

Our personal favorites are REDARC's BCDC and the Manager30, both of which use a multi-stage charging process to fully charge your battery without overcharging or draining your vehicle. Both also work with solar, but we'll talk more about this handy feature in the solar section below.

Who Should Use a Battery Charger?

If you plan on being on the road often and want to make sure your rig is charged up and ready to use by the time you reach your destination, using your tow vehicle with a battery charger is a great way to go.

Just keep in mind that using your tow vehicle to charge your battery isn't really a viable option if you spend most of your time in one spot.

NOTE: This is a visual overview of a potential battery charger setup and does not reflect the full wiring requirements of an individual setup. To install a battery charger, follow all manufacturer instructions.

Also needed for BCDC installation:

Winch wiring kit
Fuse kit #331-FK40 (for 25-amp BCDC) OR #331-FK60 (for 40-amp BCDC)

How to Charge an RV Battery with a Generator

Your generator isn't limited to providing power to your RV's appliances—you can also charge up your house battery. Most motorhomes have an onboard generator, while most tow-behind trailers require a portable generator. This is because onboard generators use the fuel supply from the motorhome itself, whereas tow-behind trailers don't have a fuel tank, so the generator isn't built in.

It's pretty easy to charge your RV battery with a generator; all you really have to do is plug your RV power cord into the generator, just like you would plug in for shore power. Your generator will supply 120V AC power to your RV; your RV's built-in converter will then convert some of that power into 12V DC energy to run 12V appliances light your lights and water pump. Some of this 12V power will also be used to charge your house batteries.

Keep in mind that your RV's converter will make a big difference in how efficiently your generator charges the batteries. Traditional "dumb" converter-chargers will provide a 1-stage trickle charge to your batteries, so the charging process will be slow.

A better option is upgrading to a "smart" converter charger if you don't have one already (many newer RVs have these built in). These chargers use a multi-stage process to efficiently charge and maintain your house batteries. This means the charging process will be much faster, and since it also will keep your batteries charged and in good health, you'll end up prolonging your batteries' lives in the long run.

Who Should Use a Generator?

You'll typically need to rely on a generator at least some of the time if you're boondocking (camping away from electrical hookups). Generators can handle heavier loads than solar power and are therefore more capable of running power-sucking appliances like air conditioners. Plus, they don't rely on sunny weather to work efficiently. So chances are you'll want to pick up a generator if you plan on camping without hookups, whether or not you supplement your system with solar.

Can you run a generator while driving?

Although you can run an onboard generator while you drive your motorhome, it's not a good idea to try the same thing with a portable generator. Portable generators must be kept outside for ventilation purposes, which makes them more susceptible to being jarred around. The movement can damage the generator or cause a low-oil shutoff, and some locales prohibit propane generator use while driving.

How to Charge an RV Battery with Solar

Solar power is a great way to go green and power your RV, especially if you boondock off-grid and don't have access to shore power.

It's important to recognize that solar panels do not directly charge your appliances—this is a common misconception! They actually charge your house battery by passing power through a solar charge controller and into the batteries directly (most solar kits come with the charge controller included). The power is then distributed to the rest of your RV.

Since your RV batteries supply DC power, you'll also need an inverter if you want to use your AC appliances (like the microwave, television, etc). Read more about what's involved in installing a solar setup in our how-to guide.

So how much solar do you need to charge your RV? It depends a lot on how much power you use on a daily basis. Use our overview here to find out what kind of camper you are and estimate your solar needs, or for a more precise calculation, dive into the nitty gritty of solar power estimation in our guide. Just know that running on solar power means making some concessions in regard to power use; solar panels are not as powerful as generators, so you most likely won't be able to run power-hungry appliances like your AC.

Who Should Use Solar Power?

If you plan on spending a lot of time boondocking, prefer a quieter/greener power option than a generator, and camp mostly in mild and sunny climates, you're the perfect candidate for solar.

With a large enough setup and a conservative mindset when it comes to your electricity, you can rely primarily on solar power when you boondock. Most campers combine solar energy with other power methods, like a generator, to supplement their RV's battery in order to extend their stay and use appliances with higher power draws.

If you're new to solar and want to begin with the basics, we recommend starting here for a complete list of our solar power guides.

What Size Generator Do You Need to Run an RV Air Conditioner?

How Long Can You Boondock in an RV?

How Much Solar Power Do I Need for My RV?

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