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We Bought An RV With Solar Installed, But It Was All Done Wrong

Our latest RV purchase came with the RV solar system installed wrong! We have installed the solar panels and other components in two of the three RVs we’ve had solar systems on. However, when we bought our Class A motorhome, it came with 1200W of solar panels and an already installed system. At first glance, this seemed great – one less RV solar installation we had to do!

Unfortunately, we quickly realized that the system on our purchased coach hadn’t been done correctly. It was so wrong that it was a fire hazard!

But what do you need to look for? We will share what was wrong with our motorhome’s RV solar system and a few things you should look for if you are in a similar situation.

How Our RV Solar System Was Installed Wrong

Solar power systems are simple to install. Many DIYers take on installing their own systems, which we highly encourage if you do your research, understand the system completely, and install it correctly. The trouble we see with this is that many do-it-yourself systems have problems due to installation errors or wrong parts.

While our motor home solar system worked, it had some serious issues that we were lucky did not burn it down. Here are the things we found catastrophically wrong with our system and things to remember when purchasing an RV with solar pre-installed.

1. Melting Connections On Roof

Shortly after purchasing our motorhome, the solar system stopped functioning altogether. It wasn’t hard to figure out what went wrong after looking at the panels on the roof. Multiple of the connections had were spliced together, and the crimps were poorly made and not waterproof. This caused corrosion at the connections that resulted in a poor electrical connection overheating and melting of the cables. Luckily, the roof of our motorhome is fiberglass and the charred melting cables did not do much damage or ignite the roof. 

Ideally, all electrical connections should be made in a junction box or with outdoor-rated mc4 solar connectors or waterproof high-strength butt splices. Even though the overall power of most RV Solar Systems is relatively low a bad connection over time can still be a fire hazard. 

melting solar panel wiring
Yikes, this connection melted down because of a poor butt splice and corrosion

3. Improper Wire Type 

While working with the connections on the roof, it was clear that the wrong type of wire was used. Wires exposed on the roof need to be sunlight resistant. UV sun exposure will break down most plastics over time, and the wire insulation will become brittle and even allow water penetration and corrosion of the wires.

Always ensure PV ( photovoltaic)  wiring is used on the roof that is specifically UV resistant and of the correct gauge for the current they will be carrying.

5. Solar Panels Were Wired Wrong

While replacing the wiring and fixing the failed connections, I quickly realized that the solar panels had been wired incorrectly. The panels had been wired three in parallel and one in series. This configuration basically made half the panels not do anything.

Series/parallel configurations for solar panels are a very good way of wiring them to increase voltage and lower current. However, it needs to be done properly so as not to limit the power from part of the panels. Here is a great resource showing why this works.

 I quickly rewired the panels and essentially doubled the wattage the previous owner was using. The diagram below shows how the panels were originally wired and how we reconfigured them to work two times better.

mixed series parallel solar panel wiring diagram wrong solar wiring

Pro Tip: We wrote a detailed guide on how RV solar power systems work when we built our second system on our fifth wheel.

2. The Fuse On The Batteries Failed And Melted

The system did have an installed fuse between the charge controller and the batteries, which is always necessary and correct. However, the fuse holder that was used in this solar system was a very poor quality and overheated once we had corrected the wiring of the panels.  Once again, this could have been a fire hazard as it got so hot it even melted the wires and plastic on the batteries. 

When it comes to safety equipment like breakers and fuses, never get the lowest quality because these are safety items. Ensure that all system components are rated to handle higher currents than you expect. 

Melted solar fuse wrong RV solar type
Yikes! Another fire hazard, we smelled this one.

4. Solar Panel Mounts Not Mounted Correctly With Sealant

One thing I should have changed when I replaced the wiring was the solar panel mounting. I had hoped they were properly installed on the roof, but after a while we started to have leaks. The solar panels had been screwed down with four brackets per solar panel and two screws per bracket. The sealant that was chosen was only used under the brackets and not around the edges. Some of the screw heads were exposed as well, allowing water to flow down through them.

I ended up removing all of the panels, cleaning and reinstalling the brackets with Dicor around the edges, and over the top of all the screws. This stopped all the leaks and is how they should have been installed originally.

6. Improper Charge Controller Programming 

The system had been installed with a Victron MPPT charge controller, my favorite type. This is great because these are fully programmable controllers, allowing you to set the charge profile for the batteries properly. Unfortunately, the charge controller was programmed for something closer to lithium batteries than the lead acid the coach had. This was causing the batteries to be charged too hard for too long and the voltage to rise higher than it should have. 

The problem here is that the batteries were bubbling excess hydrogen gas, causing extra corrosion and significantly shortening their life. This is the wrong thing to do for these batteries. Luckily, we did not intend to keep them because lead acid batteries really are incorrect for any solar system.

7. Batteries Not Upgraded 

While not technically wrong, the lead acid batteries in the coach were not upgraded when the solar system was installed. We only recommend people install a large off-grid solar system on an RV if upgrading to lithium batteries as well.  We have written extensively about the incredible benefits gained from lithium batteries and solar systems and feel that you need to upgrade to them to prevent wasting enormous amounts of your solar’s potential.

In addition, lead acid batteries are a maintenance nightmare that releases corrosive gases and our overall dangerous toxic mess that have an incredibly short lifespan. Within a month of owning our coach, we replaced all eight of the batteries with drop-in lithium replacements.

failing lead acid batteries
The lead acid batteries were being damaged by the solar system and were terribly corroded. We replaced them all with lithium quickly and immediately saw an improvement in the solar performance.

Always Inspect Pre-Installed Solar Systems

From our mishaps and the many solar systems we have seen installed wrong on RVs, we always recommend a detailed inspection of solar systems installed on an RV you are considering purchasing. If you are unfamiliar with electrical systems like this, we recommend hiring a professional to look it over and make sure there are no significant issues or fire hazards. Don’t let them scare you off, however, because once properly installed, RV solar systems provide amazing benefits and open a whole new world of off-grid camping.

About Tom Morton

Tom, a Pacific Northwest native, is our technical genius. Born in Washington and raised in Alaska before settling in Michigan. He's the man who keeps our operation running, both figuratively and literally.

With a background in Electrical Engineering, Tom specializes in RV solar systems and lithium batteries. He made history as the first documented individual to use a Tesla battery module as an RV battery. Tom has personally assisted countless RVers with system installations and has educated thousands more through his videos and articles.

Cinematography is another of Tom's passions, showcased in his work on the Go North series. You can see his camera skills on display in The RVers TV show on Discovery Channel and PBS where he also stars as a co-host.

Tom's mechanical expertise extends beyond RVs to boats, planes, and all things mechanical. He's renowned for taking on maintenance and repair projects single-handedly and is often spotted underneath RVs, making him the technical backbone of our endeavors.

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Tuesday 2nd of January 2024

I’ve run into several very poorly done installations and they were charged exorbitant amounts. The installers were self proclaimed solar experts… Sad.


Tuesday 2nd of January 2024

Thanks for sharing in such details. While our solar is in good shape, I've noticed that RV Dealership Service Centers and even trailer specialty shops don't do things correctly, so I am trying to learn everything myself (with lots of research) to ensure they are done properly.


Tuesday 2nd of January 2024

I learned that you cannot even trust brand new rigs with factory installed solar options. My new 2023 class A "luxury" diesel pusher came with 4 solar panels and 2 lithium batteries. First of all they installed the default solar controller they had been using for years that was not lithium compatible, so the batteries never charged as there was no way to configure the solar controller to charge what it always thought were fully charged batteries. After months of talking with the dealer and the factory the manufacturer finally admitted they'd been using the wrong solar controller and offered to upgrade it to one that was lithium compatible (service bulletin issued for >100 vehicles). Instead of allowing them to use the cheapest option possible I replaced myself with Victron MPPT SmartSolar controller and added the missing DC circuit breakers the failed to install to be able to disconnect the solar panels.

They also kept the battery joiner solenoid vs a BIM or DC to DC charge for alternator charging as part of the factory install. And, at only 400W of solar to 640 Ah of lithium (upgradeable to 960 Ah), the solar panels are on the light side and need replacing.

So, 3rd party or new from the factory, the lesson learned is not to trust and to always verify solar and lithium installations.

Best, -Mark

Joel D

Tuesday 2nd of January 2024

Thank you for another great and helpful article.

The Mortons

Sunday 7th of January 2024

Glad you enjoyed it Joel! Thanks for reading!