Can I Connect a Solar Panel Directly to an RV Battery?
Most RVs these days have at least one solar panel either mounted on the roof or as a portable setup. For us dry campers, it’s a game changer for keeping RV batteries charged without hookups.
Those tiny 5-watt panels from back in the day? Yeah, you could wire those straight to your battery like a trickle charger. No big deal. But the panels worth having nowadays pump out serious juice and absolutely need a charge controller between them and your battery.
The charge controller is basically your battery’s bodyguard. It regulates the incoming power, prevents overcharging, and shuts everything down when your battery is topped off.
For weekend warriors running basic stuff like lights, water pump and keeping the fridge cold, a simple panel-controller-battery setup works great. Just remember that more gadgets mean more panels and bigger battery banks.
Charging RV Batteries with a Solar Panel
I recommend having at least one 100-watt solar panel for charging RV batteries. It’s the sweet spot for most weekend warriors. Powerful enough to keep your batteries topped up for all the essential 12-volt stuff, but not overkill.
The beauty of this setup? You can easily slap on another panel later if you find yourself needing more electricity. I’ve added two more to my original setup over the years as my power needs grew.
There are about a hundred ways to wire a solar panel to your RV battery, some folks turn it into a NASA level project. But I like to keep things simple. What I’m sharing is the most straightforward route from a roof mounted panel to your RV batteries.
I first did this on my travel trailer with front-mounted battery boxes. If you’ve got a fifth wheel or motorhome with batteries tucked away in compartments, your routing will look different, but the overall concept is identical.
The trickiest part is figuring out where to mount your charge controller and how to run those wires cleanly.
One non-negotiable: protect that charge controller from the elements! When I had my trailer, we sealed it in a watertight box. Later, with our motorhome, I lucked out, there was already a pre-drilled hole in the floor with cables running straight to the battery compartment.
I was able to install the charge controller inside, so there was no need for weatherproofing.
Your specific setup might vary, but this approach has worked for me across two different rigs. Let me walk you through how I connected my solar panel to my RV batteries without making it complicated.
What You’ll Need
| Model | Link | ||||||
|---|---|---|---|---|---|---|---|
 | Renogy Rigid Solar Panel | 12 volt | 100 watt | Monocrystalline | MC4 Connectors | IP67 All Weather Protection | Amazon |
 | Renogy Voyager Solar Charge Controller | 12/24 volt | 20 amp | 4-STAGE PWM Technology | Flooded, GEL, AGM, SLA, Lithium Compatible | IP67 Waterproof Design | Amazon |
 | Renogy Fuse Block | – | 20 amp | Over-Current Protection | RoHS Compliant | Protective Plastic Housing | Amazon |
 | Renogy Solar Panel Mounting Z Brackets | – | – | Aluminum | M6 Hardware | Self Drilling Cap Screws | Amazon |
 | BougeRV Solar Extension Cable | 10 AWG | 40 foot | Extra Connectors Included | MC4 Connectors | Weatherproof Wiring | Amazon |
 | iGreely Cables | 10 AWG | 5 foot (10 foot available) | Tinned Copper | 3/8 & 5/16 inch Battery Terminals | Weatherproof Wiring | Amazon |
 | Cable Tubing | 1/2 inch | 25 foot | Polyethylene | Abrasion & Corrosion Protection | – | Amazon |
 | EternaBond RV Roof Tape | 4 inch | 25 foot | Aluminum Backing | Waterproof MicroSealant | UV Resistant | Amazon |
 | Dicor Butyl Tape | 3/4 inch | 30 foot | High Tack Adhesive | Waterproofs | – | Amazon |
 | Dicor Self Leveling Lap Sealant | White | 10.3 oz | EPDM, TPO, PVC Roof Compatible | Waterproofs | UV Resistant | Amazon |
 | SASHCO 13043 Lexel | White | 5 oz | Outdoor/Indoor Sealant | USA Made | All Weather Protection | Amazon |
 | Electric Junction Box | 8x8x4 inches | – | Polystyrene Plastic | Indoor/Outdoor Use | IP65 Waterproof | Amazon |
Tools Used
- Drill
- Caulk Gun (if using self leveling lap sealant instead of EternaBond Tape to seal roof screws)
- Philips Screw Driver
- Wire Stripper
- Box Cutter
- Saw (for cutting the handles of the battery boxes so the charge controller box would fit.)
Other Parts Options
We pieced together our system from individual components, but Renogy also makes a solar charger kit (click to view on Amazon).
Their kit comes with most of what you’ll need (not including all the sealants). A solid 100-watt panel, all the mounting hardware for your roof, 30-foot extension cables, 8-foot cables to connect the controller to your batteries, and a beefier 30A MPPT charge controller.
The MPPT controller is actually a step up from my 20-amp model. It’s more efficient at converting solar power, which means more juice making it to your batteries.
Both controller models I’ve mentioned work with any battery type, so whether you’re rolling with traditional lead-acid or fancy lithium batteries, you’re covered.
This kit does not come with a fuse. If you want to use one you will need to purchase one separately.
If you want to be able to angle your solar panels to follow the sun you can get a Renogy roof mounting kit (click to view on Amazon).
If you’re a solar optimization geek like me, Renogy’s adjustable mounting kit with fold-up legs is a fantastic upgrade. You can angle your panel to follow the sun for maximum power, then flatten it back down when you’re ready to hit the road.
When I finally added these to my setup, I saw about a 25% boost in my power generation. It’s especially useful if you boondock down south during the winter months.
Solar Panel RV Roof Installation Guide
Step 1: Find a Good Spot on the RV Roof
First, think about where your batteries and charge controller will go. You want that panel as close as possible to your charge controller and RV batteries to minimize cable runs.
On my travel trailer, this meant the front section since the batteries were on the tongue. Saved me about 15 feet of wiring compared to mounting it at the back.
Also, take a good look at what’s already up there. I initially planned to mount mine right by the AC unit until I realized it would be in the shade half the day. You want a spot that gets maximum sunlight exposure throughout the day.
Finding those roof supports was trickier than I expected. That stud finder that worked perfectly inside the RV was useless on the roof with all those layers of rubber and wood. We had to make educated guesses based on the interior ceiling structure.
Don’t stress too much though, we weren’t 100% sure we hit all the supports, but between those roofing screws and the liberal amount of butyl tape we used, our panel hasn’t budged.
Step 2: Attach the Roof Mount Brackets and Butyl Tape
Once you’ve picked your ideal spot, it’s time to attach the mounting brackets to the panel. This is where I got smart after making mistakes on my first installation.
Put a generous piece of butyl tape on the bottom of every bracket. I can’t stress this enough, this stuff is magic on an RV roof.
It’s not just about keeping water out (though that’s crucial). The sticky butyl tape also acts like industrial-strength adhesive, giving your panel extra holding power against highway winds.
This is one of those RV maintenance shortcuts that’ll come back to haunt you, so do it right the first time.
Step 3: Connect the Solar Extension Cables
You’ll be able to connect the solar extension cables anytime using the MC4 connectors, but take it from me, do it before you secure that panel to the roof! Way easier than trying to squeeze your hands underneath later.
I learned a neat trick after my first installation, zip-tie the cables underneath the panel itself. This keeps everything neat and protected, plus it takes all the strain off that connection box under the panel.
Since I started tucking and zip-tying them underneath, the MC4 connectors stay completely protected from the elements, and I haven’t had to replace a single cable in years.
Step 4: Mount the Panel
Use the included self-drilling cap screws with rubber washers to secure the mounting brackets to the RV roof.
They bite right into the roof material. In the installation photo above, you can see how the butyl tape squishes out around the brackets, that’s exactly what you want. It’s spreading and sealing the screw holes as you tighten everything down.
Even though the butyl tape and rubber washers should create a decent seal, I always add a second layer of protection as an extra precaution since we full-time and use our RV 365 days of the year.
We used self-leveling lap sealant, which works fantastic, but you can also EternaBond tape so long as you have plenty going over the edges to seal everything up.
All this sealant may seem like overkill, and maybe it is. But I’d rather spend 20 extra minutes sealing everything for the long haul than deal with roof leaks later.
At this point, your 100-watt panel should be rock-solid on your RV roof. Now we can move on to setting up the extension cables and the solar charge controller.
Running the Solar Extension Cables
We wanted to make this installation as simple as possible. So instead of getting fancy with hiding cables inside walls, we just ran them down the outside front of our trailer. Sometimes the straightforward approach is best.
On the roof, I used PVC cable hiders to secure the solar cables and shield them from UV damage. Looking back, I would’ve used EternaBond tape instead, that stuff sticks to absolutely everything and has this special outer layer that stands up to sun exposure way better than plastic.
For the vertical run down the front of the trailer, I stuck with more PVC cable hiders. Again, EternaBond would be more durable, but the tradeoff is it’s a permanent solution, nearly impossible to remove if you need to make changes later.
When I reached the bottom half of the camper, I switched to black cable tubing for road protection. This stuff is tougher and handles road debris better than the PVC.
Found a perfect spot where I could access the plywood floor underneath and used simple cable clamps with regular screws to secure everything.
Connecting the Charge Controller
If you’re comfortable drilling a hole in your RV floor, the front storage compartment makes an ideal spot for your charge controller. It’s watertight and lets you easily check on things whenever you want.
Since writing this article I’ve done that type of installation on my parent’s travel trailer. It worked really well and drilling holes under the front storage compartment to run cables wasn’t as scary as I thought it would be.
We took a different approach with our travel trailer since we wanted everything easily removable. Instead, we mounted the charge controller in a waterproof PVC electrical box that fit perfectly between our two batteries. Worked like a charm and made it simple to swap equipment later.
Whether you mount it inside the RV, in a storage compartment, or outside like us, the basic cable setup remains the same. You’ll just need longer cables for indoor installations.
Step 1: Prep Battery Cables
Both the battery and solar panel need to be connected to the charge controller. We used 10 AWG cables with battery lugs on one end and open wires on the other.
Since our controller sat right next to the batteries, we didn’t need much cable length. If your setup has more distance, just get longer cables to bridge the gap.
Some folks skip the fuse, but I strongly recommend installing one between the battery and charge controller. We used a Renogy 20A Fuse Block, but any 20-amp inline fuse will do the job. We chose 20 amps based on what our cables could safely handle.
We installed the fuse inside the electrical box alongside the charge controller to keep everything protected from both water and the sun.
Step 2: Connect the Charge Controller
After you set up the cables that connect the batteries and make sure they can reach, you can connect them to the proper terminals on the solar charge controller.
Make sure you thread the cables through the electrical box first. Learned that one the hard way when I had to disconnect everything and start over.
We drilled two 1/2″ holes in the electrical box that could fit 2 cables each. Using 2 small holes instead of one big one means less space to seal with caulk, little details like this matter for waterproofing.
Step 3: Mount the Charge Controller
Use small screws to mount the charge controller inside the electrical box. Nothing fancy needed here, just make sure it’s secure still watertight.
The finished setup should have both the charge controller and that 20 amp fuse tucked safely inside.
I used liberal amounts of caulk to seal the cable entry holes so no water or dust from the road could get inside the box.
Step 4: Secure the Charge Controller Box.
There was just enough space for our electrical box to fit between the two RV batteries after we sawed off the inside plastic handles on the battery boxes. Bit of a hack, but it worked perfectly.
The battery and solar panel cables come out of the bottom of the box. Connect the cables with the battery lugs to the same battery terminals where your RV cables connect.
This is important, you want to charge the batteries from the same terminals that power is being drawn from.
Our travel trailer runs on two 12-volt deep cycle batteries connected in parallel. This means the positive cable from the charge controller connects to one battery and the negative to the other.
Step 5: Setup the Charge Controller
Most decent charge controllers like the Renogy Voyager can handle different battery types, but they need proper settings for optimal charging.
Follow your controller’s instructions to match the settings to your specific battery type. This makes a huge difference in charging efficiency and battery lifespan. Five minutes spent configuring things properly will add years to your RV batteries and keep you powered when you’re boondocking.
Final Thoughts
If everything was set up correctly and the connections were done right, the solar panel should be able to charge the RV batteries without you needing to do anything else.
But to be safe, I recommend checking the charge controller routinely to make sure it’s set correctly, charging the RV batteries, and still being protected by the electrical box.
Also, check the solar panel now and again to make sure it’s still secured tightly to the RV roof and clean. It’s amazing how much dust and bird droppings can accumulate after just a few weeks of camping.
A quick wipe-down with a soft cloth can boost your charging efficiency by 15-20% if it’s been a while.
I hope you’ve found my little guide helpful. Setting up solar panels on an RV roof doesn’t have to be difficult. I believe most handy RV owners can do an installation like this themselves.
Just make sure you’re using compatible components and everything is secure. Happy solar-powered camping!
hello! I would like to know what you think about the flexible panels that are glued directly to the roof of vans and motorhomes, best regards
Hi,
They are great if you use high-quality panels that can handle extreme temperatures without burning. A lot of the cheaper models aren’t made with materials that can handle the heat while being glued to a surface.
I’ve been told to only use flexible panels with an ETFE layer, so if you’re the one buying the panels make sure it has that.
great, thank you very much, I am deciding whether to put a roof rack with a rigid solar panel or a flexible one and I can’t decide, in Spain it can be very hot at noon, I only have to buy a 200 w solar panel, so it will be the best quality you can find
Excellent article. Very simple. Exactly what I was looking for. My question is, can you use the power directly from the solar panels instead of just batteries? Does the charge controller switch between the batts and panel power? Thanks in advance.
Hi,
Unfortunately, I don’t think there is a solar charge controller that can do that.
Its job is to regulate the voltage from the panel and charge the battery safely. It can’t regulate the voltage and supply a steady 12V to an RV for example, and charge controllers don’t work without a battery.
It is possible to power some 12V electronics directly with a solar panel with the use of a step down converter, but that’s not something that should be connected to an electrical system in an RV.