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How to Charge an RV Battery From Vehicle While Driving?

Writen by Dane Heldt

Fact checked by Robert Clark

how to charge an rv battery from vehicle while driving

Any amenities in your recreational vehicle, such as refrigerators, TVs, lights, and heaters, need electrical energy to operate. So it’s always essential to make sure your RV battery is fully charged before embarking on any journey.

A dead RV’s battery can cause you a lot of inconvenience and discomfort. In addition, letting the battery charge level get too low can permanently affect its ability to charge. Dealing with a trailer or trailer that has stalled is a huge pain that can put a damper on your trip.

Fortunately, by sticking to a few simple steps, you can charge the RV battery while driving, with a charging source as your vehicle, whether a trailer or the recreational vehicle itself. These include:

  • Step 1: Connect Your RV Battery To The House Battery
  • Step 2: Set The Connection

So, without further ado, let’s find out how to charge an RV battery from vehicle while driving.

Steps to Charge an RV Battery From Vehicle While Driving


Is Charge RV Battery While Driving Possible?

Yes. It is possible to recharge your RV battery with any tow vehicle, such as your truck, while driving by your vehicle’s alternator if you own a 7-pin travel trailer plug.

Plus, if you own a motorhome, your RV’s alternator can automatically charge your house and vehicle battery when your engine is operating (in most models). It will be helpful when you go on a short camping trip in the wild and do not have electricity connections.

If you need to recharge the house battery while your vehicle is parked, you should use the portable or onboard generator instead of your vehicle’s engine. We do not recommend starting your vehicle and using the alternator if charging the house batteries is your sole purpose.

You cannot expect the batteries in your RV to be charged quickly with the engine’s alternator while driving. Instead, your RV’s batteries will be charged at a slow trickle.

Step 1: Connect Your RV Battery To The House Battery

If you want to recharge the RV house battery when driving, it is necessary to connect it to your truck’s battery, which is the only power source you have. But remember that transfer on this connection can not reach 100% because of voltage drop.

So, it is wise to utilize quality cables and plugs, which can form a stable and reliable connection and carry vast amounts of power. Utilizing such plugs and cables will minimize the voltage loss and optimize the charging state of your house battery. You can also use a 50-amp circuit breaker to prevent any fire hazards.

Step 2: Set The Connection

This step indicates configuring the connection where the VCR disconnects and parallels the start and auxiliary batteries.

With this innovative connection, your RV battery will be automatically charged when your vehicle is started. Hence, when these batteries are set to preset, you can start your vehicle to open the relay.

The house battery will be charged automatically when the relay is open. Also, when your vehicle is off, the relay will close to disconnect the battery.

The Charging Phase That Will Undergo

Through this connection, three charging stages will take place, including:

  • Boost (or Bulk) Stage

The boost or bulk phase is the fastest stage of battery charging. This is a stage where the RV battery utilizes almost all amperes, and volts emitted by your charger. The phase is typically initialized when your battery is nearly or entirely empty.

  • The Float Stage

Your battery will enter the floating stage when it is about 95% full. The charge is still active, and the voltage will still be around 13.4 volts. The current continues running into your battery in this state, but your battery will absorb a fraction of that current. This keeps the battery at full capacity while maintaining all the DC loads.

  • Absorption Phase

It is the final phase, and there should be a drop-down on the charge entering your battery. The charge will drop down to almost half of the Boost and then stay for good.

In this phase, the actual storage of energy takes place, and this energy will be distributed by your RV’s battery to the entire rig of the RV.

Why Is Charge Your RV Batteries a Slow Process?


Charging your RV batteries with the engine’s alternator while driving should be at a slow trickle. You will find out the reason behind this here. But first of all, let’s talk about two different types of entertainment vehicle batteries:

  • The starting battery (or chassis battery) is used to power the engine and all electronic equipment in your RV, such as lights and radio. This battery is charged continuously when the engine runs.
  • When your vehicle is not connected to the outside power source, the house battery (lead-acid, deep cycle, or lithium battery) will be responsible for charging everything that runs on electricity in your wheeled living environment.

So if you connect your recreational vehicle to a towing vehicle using a 7-way connector, the energy will mostly go to the vehicle’s electronics, such as all the lights and brakes, that the chassis battery also powers up.

Then, there is only a little bit of power left over to charge up the house battery. In other words, your house battery will not get much of that power, and that is why charging the RV’s batteries by an alternator is a slow procedure.

How to Charge The RV Battery From Your Vehicle Faster

Using a DC to DC charger is probably the most straightforward solution to charge an RV battery while driving. In fact, using this charger will turn a slow trickle charge into a powerful and fast charge!

Installing this charger into your RV is not challenging. You just need a little knowledge of the electrical system inside the vehicle and some tools.

It is essential to study your device’s manual and take all recommended precautions to avoid the risk of electric shock. If you believe you cannot afford to install a DC to DC charger on your vehicle yourself, it is okay to hire a trusted professional.


1. Why Is My RV Battery Not Charging While Driving?

If you realize that you cannot charge a trailer battery while driving, the cause may lie in a bad solenoid or loose wiring.

So, first of all, you should check all the connections between the batteries and the alternator to detect the problem with the help of a wiring diagram for your RV model, which you can download from the internet.

If all the current connections are fine, you need to check if you have a bad solenoid by starting your entertainment and testing the voltage at the terminals. It should be about 14 volts if there is no problem.

If everything is well with solenoid or loose wiring, the cause could be a blown fuse, faulty house batteries, a lousy battery center for the control center, a faulty alternator, etc.

In this case, you need to perform a complex series of checks to ensure that all fuses are fully functional and that the relays and batteries are in good condition. So we recommend taking your RV to a trusted technician for inspection.

2. How long do RV batteries last?

RV batteries can last up to 5 years, depending on usage and overall quality. If you want to prolong its life, it is essential to charge it properly and unplug it when storing it to avoid overheating and overcharging. In addition, eliminating the main cable is the most effective and safest way to save energy during storage.

On the other hand, you should not underestimate the importance of full charging. Delaying the charging while still in the process may damage your battery.

3. How many batteries does a recreational vehicle have?

An RV features 2 separate battery systems, including 120v AC &12v DC systems. It also has an extra automatic 12v system that is responsible for starting the engine and operating basic functions.

The Bottom Line

It is a great convenience if you know how to charge an RV battery from vehicle while driving. It is not a daunting task; just follow the basic steps above, and you can recharge the house battery while driving to your destination or the next charging station.

Do not forget to take advantage of a DC to DC charger as it delivers a more powerful charge and lowers charging time to your house batteries.

With a bit of electrical know-how, especially on charging trailer batteries from a 7 pin plug, and some essential tools, you can wire the RV trailer so that its batteries will be recharged by your towing. But if you don’t have the skills to do it correctly or the time to spend working on it, it’s always wise to get the help of a certified technician.

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