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How to Charge Trailer Battery From Truck?

How to Charge Trailer Battery From Truck?

When you’re on the road with your trailer, it can be frustrating to see your battery levels low. After all, power is important for everything from your refrigerator to air conditioning. Fortunately, there’s an easy solution – charging your trailer battery from your truck’s battery. In this guide, we’ll walk you through the steps on how to charge your trailer battery from your truck, so you can feel confident and prepared on your next adventure.

Trailer Battery: What It Is And How It Works

The battery is an essential component for many things, including providing the energy to operate the trailer’s brakes, lights, and powering appliances on board. So, what is a trailer battery, and how does it work?

A trailer battery is a deep cycle battery that is used specifically in trailers, RVs, and campers. Compared to a standard automotive battery, a deep cycle battery has the ability to discharge up to 80 percent of its rated capacity without damage, unlike an automotive battery, which should only discharge about 50 percent of its rated capacity to prolong its life. A deep cycle battery is built to provide extended periods of power while driving, camping, or when the trailer is parked.

There are several factors to consider when selecting a trailer battery. The most important factor is determining the battery’s Ampere-Hour (AH) capacity. An ampere-hour is defined as the amount of charge in ampere hours that a battery can bring up to a set voltage. The AH rating indicates how long the battery can supply its rated current before it needs to be charged. It is crucial to consider your trailer’s battery needs, such as the number of appliances such as refrigerators and lights, the length of time on the road, and the extent of the available charging capacity.

When it comes to using a trailer battery, managing the power supply is crucial. It is possible to use an inverter to convert the battery’s DC (direct current) power into AC (alternating current) that can power appliances in your trailer. It is important to note that the trailer battery is not like a car battery that will recharge automatically. The trailer battery needs to be manually charged, preferably using a multi-stage smart charger.

Trailer batteries are an essential component of travel trailers, RVs, and campers. They provide the energy to operate the trailer’s brakes, lights, and power appliances in the trailer. With proper maintenance and care, a trailer battery can last for years.

Trailer Battery

Different Types of Trailer Batteries

The right type of battery can fulfill your power needs, ensuring that you can stay comfortable and enjoy the outdoors without worrying about power shortages. While browsing through different options in the market, you might have come across various types of trailer batteries. Let’s explore the different types of trailer batteries and help you understand which one is right for your trailer.

  1. Lithium-ion Batteries

One of the most popular types of trailer batteries is lithium-ion batteries. These batteries are widely appreciated for their longer life cycle, higher power output, and lightweight design. Moreover, they offer fast charging, which means that you can recharge your batteries quickly, even while on the go. Despite their higher cost, they’re an excellent choice for anyone who wants dependable and long-lasting power for their trailer. [1]

  1. Lead-Acid Batteries

They are another common battery type for travel trailers. These batteries are heavy and not as expensive as lithium-ion, but they have a shorter lifespan. Additionally, these batteries require more maintenance and are more prone to getting discharged if not used regularly. While they’re a decent option for anyone looking for a budget-friendly battery option, they might not be the most suitable choice for regular travelers.

  1. Gel Batteries

These ones use a thick gel electrolyte instead of a liquid-based solution in some other kinds of batteries. They’re a kind of deep-cycle battery that provides power for longer periods, making them an excellent choice for trailer batteries. Due to their extra-sturdy design, they’re highly resistant to vibrations and impacts, making them ideal for rough terrains. They’re a bit pricier than lead-acid batteries, but their longer lifespan and overall reliability make them worth the investment. [1]

Gel Batteries

  1. Flooded Batteries

Flooded batteries are the original designs used in the automotive industry. They have a liquid electrolyte and tend to be lower capacity. As a result, they’re less expensive and easier to find than other battery types. They require topping up with distilled water periodically, and they come with ventilation requirements that need to be met. If you’re a weekend camper who doesn’t have much gear or doesn’t travel too often, this battery might be the right choice for you. [1]

As you can see, each type of trailer battery has its pros and cons, and the right choice will depend on your specific needs and preferences. If you’re unsure which battery to choose or have any questions, consult with an RV service professional to make the best decision for your trailer.

TOP Ways of Battery Charging

Whether you are a seasoned camper or are about to embark on your first trip, it is important that you understand how to charge your trailer battery. The last thing you’d want is to run out of power, especially if you’re planning on spending a few days in a remote location. Here we’ll explore the top ways of trailer battery charging that you can use to make sure your battery is always ready to go.

Using a Vehicle’s Charging System

One way to charge your trailer battery is by using your vehicle’s charging system. Most modern cars and trucks have a charging system that sends power to the battery while the engine is running. To use this method, you’ll need to connect your trailer’s wiring harness to your vehicle’s electrical system. This is usually done by using a seven-pin plug that connects to the vehicle’s hitch. Once connected, the vehicle will send power to the trailer battery while it’s running. [2]

Solar Power

Solar power is another excellent way to charge your trailer battery, and it’s becoming increasingly popular among campers. By installing a solar panel on your trailer’s roof, you can harness the power of the sun to keep your battery charged. This method is ideal for those who spend a lot of time off the grid and want a sustainable way to keep their battery charged. While it may require an initial investment, solar power can save you money in the long run and reduce your dependence on generators. [2]

Using a Generator

Generators are a tried and tested way of keeping your trailer battery charged. Most campers carry a generator with them to ensure they have access to power when they need it. Generators come in different sizes and are typically powered by gasoline or propane. They can be noisy, but they’re a reliable way of keeping your battery charged. Make sure you follow proper safety procedures when handling a generator and never operate it in an enclosed space.

Using a Generator

Using a Battery Charger

Battery chargers come in different sizes and can be used to keep your trailer battery charged at home or campsite. They work by plugging them into a power outlet and connecting them to your battery. Most chargers have a display that shows the battery’s charge level and will shut off automatically when the battery is fully charged. While this method takes longer than other options, it’s a convenient way to keep your battery charged while you’re not camping.

Wind Power

While not as common as solar power, wind power can also be used to keep your trailer battery charged. This method is ideal for those who camp in windy locations. A wind turbine can be installed on your trailer’s roof or nearby and will harness the power of the wind to generate electricity. While this method may not be practical for everyone, it’s an excellent way of using renewable energy to keep your battery charged.

There are many different ways to keep your trailer battery charged, and each comes with its own benefits and drawbacks. Choosing the right method will depend on your camping style, location, and budget. Whether you decide to use a vehicle’s charging system, solar power, a generator, a battery charger, or wind power, make sure you always follow proper safety procedures and keep your battery charged to avoid any unexpected power outages. With the right method, you can enjoy a hassle-free camping experience and have all the power you need at your fingertips.

Charging The Trailer Battery From Truck: A Step-By-Step Guide

Here you have a comprehensive guide on how to charge your trailer battery from your truck.

Step 1: Check The Battery

Before you begin this process, it’s essential to check the battery in your trailer to ensure that it is in good condition. To do this, you will need a multimeter. Connect the multimeter to the battery terminals and check the voltage. In case the voltage is lower than 12.2V, it means your battery is low, and you need to charge it.

Step 2: Connect The Truck To The Trailer

The next step is to connect the truck to the trailer. First, you need to ensure that your truck battery is fully charged. Turn off your truck and connect the positive cable from the truck to the positive terminal of the trailer battery. Then connect the negative cable from the truck to the trailer’s frame. Ensure that the cables are secure and not loose.

Step 3: Start The Truck

Once the cables are secure, start your truck, and let it run for approximately 20 minutes. This time is enough to charge your trailer battery. You can also start the truck and connect the trailer to the charging circuits and use a smart charger to charge the battery.

Step 4: Check The Battery Voltage

When 20 minutes pass, turn off your truck and check the voltage of the battery with your multimeter. The voltage should now be around 13+ volts, indicating that your trailer battery is fully charged.

Step 5: Disconnect The Cables

Finally, disconnect the positive cable from the truck and the trailer battery. Do the same for the negative cable. Ensure that you disconnect the negative side first, followed by the positive side. This will prevent any electrical shock or sparks from occurring.

Charging your trailer battery from your truck is an easy process that anyone can do. All you need is a multimeter, jump cables, and a fully charged truck battery. If you follow the steps mentioned above, you can ensure that your trailer battery is fully charged, and you’re ready to hit the road.

Disconnect The Cables

The Risks Of Charging RV Battery From Truck

An important aspect to maintain the comfort and convenience of your RV is to have a reliable power source, primarily the battery. During a road trip, it’s natural to wonder about the battery life and how you can charge it when it runs low. One option is to charge it from your truck’s battery, but there are potential risks to consider.

Here are the risks of charging your RV battery from your truck:

  1. Overcharging:

Overcharging can happen when the power output from the truck’s alternator exceeds the RV battery’s maximum capacity. This can trigger irreversible damage to the battery by causing excessive heating and premature cell failure. As a result, it significantly reduces the battery’s lifespan, and you will have to replace it at a much earlier period than expected.

  1. Voltage Drops:

One of the most common issues that can occur when you charge your RV battery with a truck is voltage drops. When there’s a voltage drop, the battery receives lower voltage than it needs. Such a drop can damage the battery, affecting its performance, longevity, and overall reliability. Moreover, it may not charge the battery fully, leading to frustration later on.

  1. Compatibility Issues:

Not all trucks are compatible with RV battery charging installation. Some trucks may not have the correct wiring or charge controller that can provide the proper charging voltage and amperage required to charge a battery. It can not only damage the battery but also create a safety hazard, such as short circuits or even worse.

  1. Fire Risk:

Charging your RV battery using your truck could result in a fire hazard. The charging process generates heat, but if it gets too high, it can ignite the batteries and cause a fire. This risk is higher if you use incorrect wiring or faulty components that are not suitable or not in good working condition.

  1. Limited Charging Time:

If you want to charge your RV battery while driving, it’s essential to remember that there’s limited charging time. If you don’t drive far enough or continuously enough to generate enough power to charge the battery, you might not achieve the desired charging level before the battery runs out. This can lead to unexpected situations, especially in remote locations where there’s no charging station present.


How many amps does it take to charge a trailer battery?

The number of amps needed to charge a trailer battery depends on the size of the battery and how depleted it is. As a general rule, it takes about 30 amps to charge a fully depleted 100-amp-hour battery in just over 2 hours.

What is the voltage of a trailer battery?

The voltage of a trailer battery can vary depending on its state of charge. A fully charged battery will have a voltage of around 12.7 volts, while an almost depleted battery will have around 11.5 volts.

Is the trailer wiring AC or DC?

Trailer wiring is typically DC which means that the wiring system carries and distributes electrical power in a single direction. However, it is important to ensure that your trailer’s wiring system is properly grounded to prevent electrical shocks and other mishaps. It is also important to note that trailer wiring can be 12 or 24 volts depending on the electrical system of the trailer.

Useful Video: How to charge your battery in your trailer off your seven pin


As you can see, it is relatively simple to charge your trailer battery from your truck’s battery. With the right knowledge and a few simple steps, you’ll be able to keep your trailer powered up on long journeys. Always remember to prioritize safety, locate the battery, connect the positive and negative connections and charge the battery. Regular maintenance of the battery should help to make the power last longer and keep you connected to modern conveniences on your camping trips.

  1. https://koa.com/blog/what-you-need-to-know-about-your-rv-batteries/
  2. https://rvlife.com/how-to-charge-rv-batteries/