Charging Trailer Battery from Tow Vehicle

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Power considerations are often on your mind when towing a camper or trailer. Using a tow vehicle to charge a trailer battery is one way to ensure that the 12-volt batteries in your towable don’t run too low when driving to your destination.

Can I recharge my RV battery with my truck? Sure! Charging camper or trailer batteries from a tow vehicle is no problem. However, you either need special equipment to do it or it’ll already be present and you’ll need to understand how to use it.

Understanding Your Camper Trailer Battery Charging System

With the camper trailer battery charging system, it’s possible to hook it directly up to the electricity at home or in an RV campground too.

A home system uses either a 15- or 20-amp system and the RV park uses either 30 or 50 amps, respectively. Hooking up your camper or trailer to charge the batteries when at home or in a campground is an excellent idea. This is because, with deep cycle batteries, they can suffer when their retained charge declines below 70% or so, with a significant chance of battery damage below 50%. Therefore, every opportunity needs to be taken to keep all batteries topped up.

However, when that’s not enough, then you’ll need to keep charging the house batteries while driving too. This won’t happen automatically unless you’re equipped to do so.

Read Also: How to Watch TV with a Generator

Charging Camper Battery from Tow Vehicle

Charging your camper battery with a tow vehicle isn’t that difficult. However, you will need the proper equipment to do so. If you’re charging a camper trailer battery from a car or truck, then it may already have a universal mount or switch insert added near the hitch at the rear. Otherwise, this will need to be fitted for you.

The idea with towing a camper is that it’s supplied power and enables various systems like the brakes, lights, brakes, etc. This way, when the camper is blocking the view from the back of the tow vehicle, the same reversing, braking, indicators, and other lights function correctly on the camper too.

Read Also: Towing a Travel Trailer in High Winds

Charging Trailer Battery from Tow Vehicle: Is it Any Different?

With trailer battery charging, it shouldn’t be any different from charging a teardrop camper (or another type). It’s the same systems, same equipment too. So, that makes things simpler for RVers.

A trailer battery charger is required to ensure power that’s sent and received can charge the house batteries while on the road too.

How to Charge a Trailer Battery While Driving

The trailer (or camper) needs a 7-pin plug (sometimes referred to as a 7-way). The plug connects your tow vehicle to the trailer or camper.

Either you’ll need to purchase the equipment necessary to charge via a 7-pin plug using your truck or car as a towing vehicle, or have a specialist fit the equipment for you.

Charging Trailer Battery from 7 Pin Plug

The 7 pin plug is designed to provide and pass-through for systems from the tow vehicle to your towable. Not only does it supply power for charging the house batteries in the camper or trailer, but it also does other things too.

Each of the 7 pins inside the plug provides a different facility that’s distinct from each other. Here is a breakdown list:

  • Tail and running lights
  • 12V power
  • Reverse lights
  • Right turn and stop
  • Left turn and stop
  • Brake controller output
  • Ground

Through the 7-pin system, various lights on the rear of the towable are managed to ensure that when you brake, the brake light illuminates at the back of the trailer or camper for other drivers to see. Similarly, the brakes are activated via the brake controller output system too.


On the power side, 12-volt power is also fed through from the tow vehicle to the trailer or camper. This then charges the house batteries to ensure that they won’t lose their charge.

Read Also: How to Tell If a Deep Cycle Battery is Bad

What is the Difference Between 7 pin and 13 pin Electrics?

You may have seen mention of a 13-pin electric connection too. Then there are 7-pin electrics too.

7 pin Electrics

There are several different 7-pin systems to supply power, light signals, and more to the towable. Some are used for commercial or haulage purposes, whereas another relates only to RVs and towing your camper or trailer behind you. We’re only concerned with the RV type.

13 pin Electrics

With 13-pin electric connections, these are far less commonplace. However, for completeness, know that these are similar but provide an extended list of facilities to the camper to a trailer to use.

Just like the 7-pin includes brakes, lights, 12-volt power, etc., the 13-pin goes beyond that. There are even 13-pin to 7-pin conversion kits if you need 7-pin and your current system is 13-pin.

Fortunately, most RVers can easily access the 7-pin RV systems which are fairly universal now.

A truck towing a camper/trailer behind on sand

DC to DC Chargers to Charge the Camper or Trailer

While charging from the towing vehicle to the camper or trailer while driving works fine, it will usually only trickle charge the battery. Also, it mostly works when driving unless planning to run your engine while immobile which isn’t the best idea.

Charge Faster and Be Ready for Dispersed Camping

Once you’ve arrived at your destination, to boost your battery up to a satisfactory level, it’s beneficial to use a DC to DC charger for that purpose. These are designed to supply a charge either from solar panels directly or from the tow vehicle’s battery. Using this system works faster than relying on the alternator and has other advantages too.

If you’re at a campground and have selected a pitch with electrical hookups, then you can simply plug into 30-amp or 50-amp power and charge your camper or trailer’s batteries that way. However, you may have a camping spot that isn’t supported by hook-ups or be dry camping on BLM land. In which case, you’ll need to ensure your camper or trailer batteries are fully powered, and if not, charge them up pronto! This is where DC to DC chargers comes in.

Using the Correct DC to DC Charger Type

With a DC-to-DC charger, ensure it’s compatible with your battery type. Depending on whether you’ve got gel, lead-acid, AGM, lithium, or another type, pick appropriately and bear this in mind when replacing the batteries later too.

Redarc BCDC Battery chargers come with dual inputs and handle 12-volt power. They’re a strong solution and have products supporting charging from solar panels or the vehicle’s battery. These products may support 12-volt and 24-volt for a towable with greater power requirements, as well as provide support for different amperage levels (12, 20, 25, 40, or 50 amps) depending on your needs. Therefore, it’s necessary to choose these types of products carefully to ensure they’ll deliver the service you need once at a campground or dry camping.

Redarc Dual Input 50A in-Vehicle DC Battery Charger

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Closing Thoughts

Keeping your house batteries topped up is essential. Otherwise, you risk arriving at your destination and discovering that the systems inside your camper don’t work. Also, once most battery types (except lithium) fall below a 50% charge, their failing performance will be evident. They’ll then all need to be replaced at considerable expense.

Charging your house batteries while towing the trailer or camper is a great way to accomplish this. Adding a DC to DC charging capability also ensures any shortfall in battery levels can have a quick fix shortly after arriving. That way, you’re covered in either situation.

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