How to Hook Up Solar Panels to RV Batteries

Connecting solar panels to your RV’s batteries might seem straightforward, but it’s important to follow correct procedures when dealing with electricity. An improper connection can be dangerous or damage the equipment you’re working with.

This article helps you understand how the process works and the precautions necessary to ensure a safe, long-lasting RV solar power setup.

Note: If you don’t have experience working with electricity, it’s recommended that you ask for help from a qualified electrician. We are dealing with high voltage here, and one wrong move can be dangerous.

Required Components

  • Solar Panels
  • Solar Inverter
  • Charge Controller
  • Combiner Box
  • Transfer Switch (Optional)
  • Fuse or Circuit Breaker
  • 12v Deep Cycle Solar Battery
  • MC4 Cables

Installation Steps

We will discuss the most straightforward way to hook up your solar panels directly to the RV batteries. This is done by connecting the negative wire from the solar panel (black) to the negative terminal on the battery (black) and then connecting the positive wire from the panel (red) to the positive terminal on the battery (red). 

However, connecting a battery directly to your solar panels may lead to two issues:

  1. Battery Discharge
    Battery discharge occurs when the battery is fully charged, and no more solar energy reaches the solar panel. Electricity may slowly leak back into the solar panel, causing the battery to discharge gradually. If this happens regularly, it will shorten the battery’s lifespan. 

    Although the amount of current leakage is minor, installing a blocking diode between the panels and the battery can help you avoid it. The diode acts as a one-way valve, allowing electricity to flow only from the solar panel to the battery, and preventing leakage.Most solar panels have a built-in blocking diode, but it’s essential to check beforehand.

  2. Battery Overcharge
    The solar panels can overcharge the battery, causing it to overheat. This can harm the battery and RV appliances and carries a fire hazard. This can happen if you’re not using a charge controller to prevent solar energy from flowing into the battery once it’s full.

Follow these steps to connect your solar panels to RV batteries:

Step 1: Mount the Solar Panels on the Roof of the RV and Wire Them Together

Mount the Solar Panels on the Roof of the RV
Mount the Solar Panels on the Roof of the RV by Adventurous Way

Start by installing the mounting brackets that come with your solar panels. Make sure to choose a location where they will be exposed to as much sunlight as possible for maximum power output.

If you don’t want to drill holes in your RV’s roof, you can run your wiring through a refrigerator vent or use the ones where the plumbing enters. 

Make sure to caulk any drilled holes to avoid leakage when it’s raining.

Step 2: Connect your Batteries to the Charge Controller

Connect your Batteries to the Charge Controller
Connect your Batteries to the Charge Controller by Wind of Keltia

A charge controller bridges the RV solar kits/panels and batteries.

To connect your RV battery to the controller, slide the wire ends of both the positive and negative cables of the battery into the input battery terminals specified on the solar charge controller. Then, screw the terminal with a screwdriver to ensure the wires are safely in place.

It’s best to install a fuse between the battery and charge controller on the positive battery cable to protect against excessive current passing through it and avoid any sudden surge of electricity.

Step 3: Wire your RV Solar Panels to the Charge Controller

Wire your RV Solar Panels to the Charge Controller
Wire your RV Solar Panels to the Charge Controller by Footprint Hero

To wire your RV solar panels to the controller, you need MC4 cables.

These cables have a male and female connector on one end and bare wire on the other.

Each solar panel has two wires, one with a female MC4 connector (negative) and the other with an MC4 male connector (positive).

We’ll combine the solar panels we got for the setup in a combiner box by plugging each panel’s male and female connector ends with the female and male connectors located in the combiner box inputs. 

The combiner box acts as “combiners” for several solar panel inputs to facilitate the connection while providing electrical protection through fuses and breakers.

Coming out of the combiner box, we will have two wires for the whole solar system—one for positive current (red) and one for negative current (black).

Finally, connect both positive and negative combiner box cables to the controller by sliding the wire end of each of them into the input ports on the controller specified for a solar panel. Tighten the screws using a screwdriver. (Your charge controller should have the solar panels terminals labeled with something like “PV.”)

Note: it’s a good idea to install a circuit breaker on the wires connecting the combiner box to the charge controller. This will help safeguard your electrical system in the event of a fault. 

Step 4: Double-Check All Wiring and Ensure Everything is Working

Double-Check All Wiring and Ensure Everything is Working
Double-Check All Wiring and Ensure Everything is Working by Clean Energy Reviews

After wiring all your equipment, double-check that everything is in order. For example, most charge controllers have digital displays showing the current flow into the battery.

Check the display to ensure that all connections seem okay. If so, leave the RV battery connected until it is fully charged.

The size of the battery, solar panel wattage, energy usage, and sunlight all play a role in determining how long it will take to charge the battery.

Your RV solar system is now ready to run the RV appliances that operate on DC voltage.

Note: An inverter must be connected between the battery and the desired AC appliance to utilize AC-powered devices. Most modern RVs already come with built-in inverters.

  • Nichole Hutt

    Hi, I'm Nichole! 👋
    I always felt close to nature during my childhood. Preferring to spend my time alone playing with backyard animals at my family farm. 🐷
    In 1997, I attained my electrical engineering degree at the Oregon Institute Of Technology, graduating top of my class. Several years later, I qualified for my M.S. in Renewable Energy Engineering, also at OIT. 🎓

    Combining my love for nature and passion for engineering, I have worked for solar panel manufacturer's in my state, most notably as a PV solar engineer for Zamp Solar.

    I founded RenewableSystems to share my knowledge and expertise in the renewable energy field and help save this beautiful little planet of ours. ☀️🌎

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