How To Charge RV Battery From Vehicle

How To Charge RV Battery From Vehicle

Published Date: October 17, 2020

Last Updated on June 22, 2023 by Camper Front

A dead battery can be more than an inconvenience when living in an RV. When it comes to your trailer, letting your battery charge drop too low can permanently affect its ability to hold a charge.

Not to mention, dealing with a dead trailer, tow vehicle, or accessory battery is a huge pain that can put a damper on your trip.

So for a hassle-free trip, you have to know how to charge the RV battery from the vehicle. This also eliminates the stress of having to look for areas to charge your battery when they go down.

How To Charge RV Battery From Vehicle

Before we get into explicit details about how to charge the RV battery from the vehicle, let’s talk about the battery itself.

Your RV batteries are basically the powerhouse of your RV; every appliance in your RV depends on the 12-volt system for power.

There are basically two types of batteries found in an RV; the source of the most power is the deep cycle battery, which store enough power, so it powers most of the appliances in the RV, while the other type of battery is the SLI (Starting, Lighting, & Ignition) known as the “starting battery.

Both of these batteries are both lead-acid batteries; the only significant difference among them is that the deep cycle battery is meant for constant use while the SLI battery is meant to produce small bursts of energy.

With proper management, your deep cycle battery can last you up to ten hours. However, recharging these batteries requires a lot of patience as it takes less time for the battery to drain than for them to reach a full charge.

In order to fully stretch the lifespan of your battery to the fullest, you should take good care of the battery and never allow it to drain more than 50%, as it can cause irreversible damage to the battery.

You can tell if your battery has started to drain by paying attention to the voltage given off by the battery as 12-volt RV batteries offer slightly more voltage when it is fully charged.

If the RV is equipped with a solar panel or an inverter, you can monitor the state of charge by making use of the battery monitor, which displays the charge state. You can also determine the voltage with a voltmeter.

The process of charging your battery with the RV can be applied to different battery types like marine, automotive, and deep cycle. And you will need a couple of tools like;

  • Voltage Controlled Relay (VCR)
  • high-quality amperage cables
  • Anderson plugs


The first device you will need is the voltage-controlled relay. It serves as an automatic on/off switcher, and it automatically disconnects as well as parallels the auxiliary and starts batteries.

When your relay is closed, the truck and the trailer batteries get paralleled to the preset level. So that when your RV is turned off, the device stays off too. It also disconnects the starter battery from the auxiliary battery.

Also, once you turn on your RV, the voltage-controlled relay will bridge the starter with the battery; all of this process is completely automatic, so you don’t have to worry when the truck is off.

This voltage-controlled relay resets the voltage level after use.

Next, you will need some high-quality cables in order to combine the batteries and minimize the voltage drop. It is recommended to make use of Anderson plugs as they offer better connections, they lose minimal voltage while transferring energy, and they carry large amperage too.

You want to make sure the cable can easily be attached or detached from the tow bar. You may experience the battery becoming heated up but do not fret!

As most of these batteries are equipped with an anti-hazard system, this circuit protection comes into play when the connection goes above 50 amperes; it shuts everything off to prevent any fire hazard.

Also, if you are making use of Anderson plugs, it takes your safety to an extra level as they can carry a vast amount of amperes during the transmitting process making it an excellent carrier.

With this, you get a fully charged battery, ready to serve you and your family for the next couple of hours.

How long you should let it charge is totally dependent on the battery’s initial status because it will take more time to charge a battery from 20%-80% than from 30%-80%. So battery’s capacity also plays a major role in determining how long your battery will charge for.

How to Maintain Your RV Batteries

How to Maintain Your RV Batteries

The importance of properly maintaining your RV batteries cannot be overemphasized; it helps to keep your battery in good health for the longest time possible. Here are some useful tips to properly maintain your RV battery.

Storage Temperature

When storing your battery, you want to make sure The temperature of the storage place is between 32 and 80 degrees Fahrenheit. It should also be a cool and dry place.

And even while the battery is in storage, you want to keep an eye on the battery, checking it constantly and recharging it when necessary.

Exposure To High Temperatures And Overcharging

While overcharging your battery might feel like a logical thing to do, it does more damage than good to your batteries.

How? Well, the battery, even though it’s fully charged, still receives what is known as trickle charges. These aren’t full bursts of charging power because the battery no longer needs it, however, the battery is still getting power.

When the battery receives trickle charges too many times, its internal chemistry begins to change for the worst. So letting your battery continue charging even when it has reached its full capacity is something you don’t want to indulge in.

Also, during hot weather or when the battery has been in constant use, you need to keep an eye on the battery’s electrolyte level and top it off with distilled water when needed.

Prevent Salfation

Salfation is caused when you Allow your battery to go lower than 50%; this will cause the buildup of lead sulfate between the plates, and this further leads to the inhibition of current flow.

This is because your lead acid battery is filled with an electrolyte solution of sulfuric acid and water, and the sulfur is what aids the movement of current through the battery plates.

Also, Allowing your battery to get below 80% frequently will cause the acid to be pushed to the bottom of the battery while the water floats at the top, and this can lead to salfation in the long run.

To prevent this, it is recommended that you never let your battery get depleted lower than 80% charge.

Turning Off The Battery Disconnect Switch When The Rv Is Not In Use

When you store your RV, you may think that after disconnecting all the appliances, there shouldn’t be any drain on the battery. However, there are small or “parasitic” loads like LP gas detectors, clocks, or appliance circuit board that keeps discharging the battery over time.

So before putting your RV into storage, you want to make sure that the battery disconnect switch has been turned off; you can also try trickle charging your batteries while they are in storage; it is a great way to make sure that your batteries’ “juice” is constantly replenished.

Cleaning The Connections

If the battery has any sign of corrosion or grime on any of the connections, you want to get rid of it as soon as possible to prevent the corrosion from setting in and expanding.

You can make use of a mixture of baking soap and water with a firm bristle brush to gently remove every sign of corrosion from the battery.

Before doing this cleanup, you want to make sure you put on safety gloves for protection against the corrosive acid.


Knowing how to charge your RV battery from the vehicle will save you from all the hassle of frantically looking for where to charge your battery when they suddenly run down in the middle of the night.

You also want to follow a proper maintenance routine with your batteries in order to maximize their lifespan.

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