How to Charge an RV Battery From the Tow Vehicle While Driving (Fast)

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Those comforts of home we take with us when RVing – lights, TV, phone chargers, some appliances, etc. – require electrical power to operate.

So, it’s important to keep your RV batteries charged and ready to go when needed.

Luckily, there are several ways to do this, with one charging source being your vehicle, whether your tow vehicle or the recreational vehicle itself.

Let’s quickly learn how to charge an RV battery from your vehicle. Plus, how to drastically increase the charging speed!

How Do I Charge My RV Battery While Driving?

You can charge your RV battery with your truck (or any tow vehicle) while driving by way of your vehicle’s alternator as long as you have a 7-pin travel trailer plug. And if you have a motorhome, your RV’s alternator should automatically charge your house and vehicle battery when the engine is running (in most models).

This comes in handy when you boondock without electrical hook-ups for a short period of time.

Tip:  If the house batteries need to be recharged while the vehicle is parked, use your onboard or portable generator instead of the vehicle’s engine. It’s not recommended to start your vehicle and use the alternator for the sole purpose of charging the house batteries.

Now, with that said, don’t expect your engine’s alternator to quickly charge up your house batteries while driving down the road. At best, it will charge the house batteries at a slow trickle. Let’s learn why that is and how to speed it up!

How Long Does It Take to Charge an RV Battery With a Truck?

As we just mentioned, charging your RV house batteries with your alternator while your engine is running is a slow process, and here’s why.

Let’s first understand the two different types of batteries in your RV:

• The starting battery (often referred to as the chassis battery) is used to start the vehicle’s engine and power all electronics – headlights, turn signals, car radio, etc. The alternator continually charges the starting battery while the engine is running.
• When you aren’t hooked up to shore power, the RV’s 12v house battery (usually a lead-acid, deep cycle battery, though lithium batteries are used, as well) or bank of batteries runs all things electrical in your living area.

Now, your RV’s starting battery also powers the electric brakes, running lights, turn signals, and brake lights if you have a 7-way connector plug between your tow vehicle and your travel trailer.

So, between continuously charging the starting battery and operating the RV’s essential lights, there’s only a little bit of power left over to charge up the house/trailer battery.

In other words, there’s not enough juice to do the job adequately.

How to Charge Your RV Battery From a Vehicle Faster

Luckily, with a DC to DC charger, you can turn that slow trickle charge into a fast, powerful charge! It’s like comparing a garden hose to an eyedropper to charge your house battery with this gadget as part of the system.

Renogy DC to DC Battery Charger (20, 40, or 60 amp)

Price:

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A DC-to-DC battery charger integrated into your charging system acts as an electronic pump to boost the voltage and amps coming from the vehicle’s alternator, providing a more powerful charge and reducing charging time to the house batteries.

The maximum amperage with a DC to DC battery charger is closer to 20 amps, as opposed to just 5 amps without one.

Installing one does require a little electrical system knowledge and a few tools, but it’s a fairly straightforward process. Remember, there is a risk of electrical shock when working on your vehicle’s electrical system, so be sure to take safety precautions seriously and read the owner’s manual for important safety information.

We included a complete DIY installation video tutorial below for the popular and highly recommended Renogy DC to DC Charger to make the installation process as easy as possible.

Renogy DC to DC Battery Charger (20, 40, or 60 amp)

Price:

Buy Now on Amazon

Clicking this link to make a purchase may earn us a commission at no additional cost to you.

Important: If you don’t feel comfortable installing a DC to DC charger in your vehicle, it’s better to hire a technician to perform the job for you.

Follow these general instructions to wire your truck to charge your camper battery faster with a DC to DC charger. Always read and follow the manufacturer’s instructions for product-specific and up-to-date information.

Tip: Download the Renogy DC to DC charger user manual for installation instructions, safety precautions, and more.

Is Your RV Battery Not Charging While Driving?

If your RV battery is not charging while driving, it usually comes down to loose wiring or a bad solenoid (of many potential possibilities).

First, check all the wiring connections from the alternator back to the batteries. Downloading the wiring diagram for your make/model of RV will help you locate all of the connections.

If all connections check out, test for a faulty solenoid by starting your rig and testing the volts at the terminals, which should be around 14 volts.

If both the wiring and solenoids check out, there could be several things still wrong, including a blown fuse, bad house batteries, bird relay or battery isolator issues, bad battery control center (BCC) box, bad alternator, etc. Check to make sure any fuses are good and the relays and batteries are fully functional. If the problem persists, take your recreational vehicle to a certified technician for inspection.

Related: Camper Battery Not Charging When Plugged Into Shore Power?

Other Ways to Charge RV Batteries

While charging your RV batteries while driving is a great way to top them off, there are other ways to charge your house (and, in many cases, even the chassis) batteries and power your electrical devices.

Check out our guides on all the other ways to keep your RV batteries charged:

• How to Charge RV Batteries 4 Different Ways
• Does an RV Battery Charge When Plugged Into Shore Power?
• How to Charge an RV Battery With a Generator
• How to Hook up Solar Panels to RV Batteries

And remember, charging is just one part of the equation. You will need a high-quality battery to keep your devices and appliances running. Check out our guide to the best RV battery for boondocking to find the perfect battery (or batteries) for your vehicle.