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How to Charge RV Battery from Vehicle?

Writen by Tom Hank

Fact checked by Joseph Varney

How to Charge RV Battery from Vehicle

If you are a new RVer, then you probably do not know how to charge RV battery from a vehicle. Of course, you might already know that your car’s battery is constantly recharged by the engine’s alternator but the question is, is there a way for your home batteries to charge while you are driving?

However, before you learn how to charge your RV trailer’s batteries while you are on the road, you need to know how to take care of them. If your batteries are pretty well taken care of then they will take care of you as well.

Not taking good care of your RV’s batteries might cause them to become too damaged to even take a charge even if you constantly make it so that they can be charged while you are driving. Here are some tips and tricks on how to keep your RV batteries functioning like new:

Table of Contents

Storing the Batteries


RVs are not supposed to be used all year round, at least for most people. If the camping season has ended, you need to keep the RV in storage for a couple of months. This also means that you will need to store the batteries properly so that you can still use them during the next camping season.

First of all, do not place your batteries directly on the ground. If you do this, the battery will quickly discharge. Make sure to place it on top of something, like a block of wood, to prevent it from directly getting in contact with the ground.

Check the batteries for any damage or corrosion on the terminals. If you find that there is a bit of corrosion, use equal parts of baking soda and water and a wire brush to get rid of the rust and grime. This will ensure that the batteries will still work properly on the next camping season.

Check the water levels of each battery. If they seem low, refill them with automotive-grade distilled water. Fill only up to the battery vent and no more. Store the batteries somewhere that is cool and away from direct sunlight. However, the temperature should not be so low than the water inside the batteries

The ideal place will be inside your garage cabinet. Also, make sure to store it where it is not too humid. These are only a couple of pointers on how to properly store your RV batteries pending the next camping trip. Follow them correctly and you will have batteries that are ready to go on your next camping trip.

Proper Upkeep and Maintenance


Unless you get maintenance-free batteries (which still need a bit of maintenance), you need to do a couple of maintenance procedures on your RV batteries to make sure that they can last for more than a year.

Check the water levels every month, twice a month if you use your RV regularly. Only use distilled water, not the type used for drinking, but the ones that are sold in automotive supply stores. If the water in the batteries is getting low, top it up. Take care not to exceed the maximum mark on the battery casing.

If possible, do not let the charge of your RV batteries go below 50% of its capacity. At the very least, do not let it get past 20%. This will help prolong the lifespan of the batteries.

Also, if possible, do not use your RV batteries when it is blazing hot outside. If you need to use your appliances, move your RV to a cooler, shaded area. The added heat load will put unnecessary stress on the batteries, cutting short its lifespan.

Proper Recharging (Using a Charger)


To recharge the batteries with the help of a charger, follow these tips and guidelines:

Invest in a good charger – The absolute best way to ensure that your RV batteries will last for many more camping trips is to charge it the right way. Invest in a quality charger, one that is specifically designed for the size and capacity of your RV batteries. This might mean you have to spend a bit of money but it will be worth it because you will save on batteries.

Do keep in mind that flooded and sealed automotive batteries will require different chargers. You should do enough research on your RV batteries and their proper needs before you go shopping for a charger.

Do not overcharge and overheat the batteries – You will need to constantly monitor your batteries while they are charging. Treat it like a baby that you have to keep watch over so that you can do something before anything goes wrong.

One of the things that you need to watch out for is overcharging. If you have a sophisticated battery charger, then it will automatically cut off the moment the batteries are full. If you have an old-school charger, you need to monitor the voltage coming out of the batteries and unplug it the moment that it reaches 12.7 volts and above.

When the charge is at 75% or if you get a 12.4-volt battery reading, unplug the charger and let the battery cool down before you plug it back in again to finish charging. This will lessen the strain placed on the batteries. Also, let the batteries cool down after you fully charge them before you use them again.

Consider trickle charging your batteries – Trickle charging will allow your batteries to always perform at their best and lengthen their usability at the same time. Trickle chargers are the same as traditional battery chargers but they are low-current so they slowly feed electricity into your batteries, thereby helping in making RV batteries last longer.

How to Charge your RV Trailer Batteries from Vehicle?

Other than using a separate battery charger for your RV batteries, you can also wire your towing vehicle and trailer so that you can recharge or maintain the charge of your RV batteries while you drive.

Do take note that you will not be able to fully charge the batteries unless you plan on going on a very long drive. Also, this method is not recommended if you want to recharge completely depleted batteries.

Step 1 – Turn on the ignition of your towing vehicle.

Step 2 – Measure the current coming from the black wire in the 7-pin outlet at the back of your towing vehicle using a voltmeter. Use the white-wire connector as the ground. If there aren’t any problems, you should get a reading of around 12 volts.

Step 3 – Turn off the ignition.

Step 4 – If you could not get current from the black wire, install the correct size of fuse in both the vehicle cab and engine compartment fuse boxes. Check the manual of your vehicle to find out what kinds of fuses you need to use for the charging feature of the towing connector.

Step 5 – Remove the trailer’s electrical plug from the tow vehicle’s outlet (the one with seven pins).

Step 6 – From the trailer end, run two wires connected to the trailer batteries. Use red and black wires so you can easily identify which is connected to the positive and negative terminals. It is recommended to use thicker gauge wires so that they can carry more current to charge the batteries much faster.

Step 7 – Attach one end of one wire to the black outlet of the 7-pin connector of the trailer. You can either open up the connector and solder the wire inside or use a crimping tool to crimp the wires together.

Step 8 – Connect the other wire to the white outlet using the same method you used for the black outlet.

Step 9 – Remove around half an inch of insulation from the battery ends of the wires. Attach the exposed wires to large alligator clips.

Step 10 – Attach the alligator clips to the right battery terminals. The wire connected to the black outlet goes to the positive battery terminal and the other coming from the white outlet attaches to the negative terminal.

Plug the trailer into the 7-pin connector in your tow vehicle and then start your vehicle to begin charging the batteries. When you are driving and towing the RV trailer, the current will be greater than when the engine is idling.


It is a great convenience if you can recharge the RV trailer batteries while you drive, pretty much like how your tow vehicle recharges its own batteries using the alternator. You are in luck because it is possible.

With a bit of electrical know-how, especially on how to charge RV battery from a vehicle, and a couple of basic tools, you can wire your RV trailer so that its batteries will be recharged by the towing vehicle while you are driving it. However, the results that you will get are far from the results that come from using a regular battery charger.

You can only use it to maintain the current charge level of the batteries or charge them up a bit. With this method, you can still have plenty of usable electric energy in your batteries so you can still use your regular appliances until you get to a charging station.

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