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How to Charge RV Battery From Vehicle? (Fastest Way)

Written by Philip Lopez / Fact checked by Paul Lemaire

When your RV battery needs a full recharge, you can hook the battery to your tow vehicle. It’s important that we know how to charge rv battery from vehicle so that we have sufficient power for our 12-volt systems.

how to charge rv battery from vehicle

The RV battery needs 14.8 volts to charge completely. Your vehicle alternator can’t charge your RV battery fully, so it needs additional accessories to do the task more properly. Not charging the RV battery fully may also damage it.

Here’s a helpful guide to keep your RV batteries charged at full capacity using your tow vehicle.

Table of Contents

What You’ll Need


  • 7-Pin Connector

We’ll be using a 7-pin connector to wire your RV battery to your tow vehicle. This setup will help minimize voltage drop and optimize current carrying capacity.

In this plug, you can find a group of wires and a tab that usually goes in any direction to lock into the cap. The upper left one is going to be your 12-volt power, which is usually a black wire. Meanwhile, the opposite lower end is your ground, and it should be a white wire.

The 7-pin connector is about two-inch in diameter and allows an extra pin for supplemental 12-volt power. This trailer plug is typically used for trailers and car haulers to connect to the tow vehicle.

  • DC-Input Battery Charger

If you want your RV battery to charge fast, you might need to install a DC-input battery charger. This type of charger can boost the voltage up to 14.9 volts, which is helpful, as your tow vehicle alternator alone can’t charge your RV battery fully.

Opt for a 3-stage charger for lead-acid batteries because it’s specifically built to work for deep cycle batteries.

DC-input battery chargers are compact in size and simple to install. They’re perfect for 12 or 24-volt vehicle systems.

  • Circuit Breaker

The circuit breaker can help protect the circuits from short circuits and sudden overloads. It’s an excellent way to shut down a circuit if the wiring gets so hot that it would smolder or cause a fire. This electrical switch also helps in protecting any circuit accessories from damage.

The number of amps depends on your trailer’s model. Usually, 20-30 amps are enough to operate normally. A circuit breaker can be reset manually or automatically to operate in a normal condition compared to a fuse.

  • Multimeter

A multimeter is an instrument used to measure various electrical properties, including voltage and current. This device will be used to check for continuity. It will verify whether the black wire is the power one and the white one is for the ground before you connect anything up.

There are many variants of multimeter to choose, ranging from manual to digital. Regardless of the type, look for one that contains a continuity test function. Continuity simply tests whether the circuit is complete or not.

  • Ring Terminal

A ring terminal comes in handy if you don’t have a box but a nut on the framing or something with just a ground wire on it. These accessories help to screw terminals and join multiple wires with a bolt and nut. They’re often sold by the bolt size that the rings will accommodate and by wire gauge size.

Make sure that the ring terminal you choose attaches securely. Look for a funneled design to allow natural entry of the wire. Check the crimp to see whether it can capture all wire strands when terminating.

  • 10-Gauge Wire

You’ll need some sort of wiring to connect the battery from the vehicle’s nut on the framing. A 10-gauge wire is perfect for this task. A 10-gauge wire can handle 30 amps of electric current.

There are two types of wires: solid and stranded. A solid wire contains a solid metal core, while the stranded ones consist of a bundle of thinner wires twisted together in an organized manner. Between these two wires, the stranded wires seem to be more flexible but less durable.

Step-By-Step Instructions


Step 1: Install The DC-Input Battery Charger

First, install the battery charger to your camper trailer next to the RV battery. Then, link the negative wires to the chassis to minimize weight, wire length, and installation cost. In addition, the chassis provides a lower resistance in comparison to a large wire, which enhances the circuit’s charging capability.

Look for the blue wire and connect it to the vehicle’s IGN. If you want to skip with the IGB cable, connect the RV’s tail light circuit to the battery charger’s sense wire and the input change-over relay.

Step 2: Wire The Trailer To The Tow Vehicle (Junction Box)

Run your 10G wire to the 7-pin connector in both your tow vehicle and trailer.

How you connect your trailer to the tow vehicle depends on how your RV is wired up. If it has a seven gang junction box, find out which stud holds the black and white wires. Use a multimeter to test for continuity, whether the white wire is for ground and the black one is for power, before hooking anything up.

Step 3: Wire The Trailer To The Tow Vehicle (Nut On The Framing)

If your trailer uses a nut on the framing instead of a junction box, use a ring terminal and a 10-gauge wire. Run your 10-gauge wire to the battery’s negative and positive sides. Hook it up in your circuit breaker to let the power flow to the rear connector.

Step 4: Charge

When charging, turn the tail lights on to get the alternator to operate. Some newer vehicles with ECU-controlled alternators might require you to turn on the headlights. Without the lights on, the vehicle’s bus voltage might go down below the battery charger’s start threshold.

Charging time may vary, but usually, it takes around a few hours to charge to 100%.


Now that you know how to charge RV battery from vehicle, you’ll surely have an option to pump your RV battery when it dies out in the middle of your road trip. The secret to charging RV batteries quickly is to use a DC-input battery charger. Install this charger in a watertight area with good airflow, and you can enjoy endless power down the road.

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