How to Install RV Solar Panels

We would like to increase our self-sufficiency with a solar panel for the RV. So far we have been very satisfied with our DIY solar power system. But because of our planned trips from 2020, where we will also work remotely, we feared that we would reach our limits. With a solar panel we can also flexibly increase our solar power when camping. We present the considerations for this and our chosen solar panel in this article.

Why do we suddenly need more electricity?

So far we have had 5-6 weeks of vacation a year, 99% of which we have spent in the RV. Hopefully we will start our big trip to Europe soon. As already explained, this will not be a holiday, but a “journey”. What’s the difference? Well, for us it’s not being as passive as possible for three weeks to enjoy each day before we have to go back to work. Because we now have time, there is no reason to lean back and say “it’s vacation”. We will work on the go, serve the blog, shoot YouTube videos, build independence and handle existing customer projects. That means cameras, laptops and tablets will be in constant use.

Is our permanently installed solar system no longer sufficient?

Already in hot Lefkada in 2019 we noticed that we had reached the limit of the performance of our solar system. We are all the more concerned about this result, even in cold weather. When we bought our new panel van, we didn’t know that our travel behavior would change significantly just two years later.

As explained in the article about our solar installation, we are limited in terms of space on the roof due to our roof box and the surfing material.

Unfortunately, there is no more space on the roof to expand the existing system. That’s why we now also rely on a 400 watt solar panel for the RV.

Warning: electricity is dangerous

Before any conversion work, please read our warnings about electrical systems in the RV and get help from a specialist if necessary.

What is a solar panel?

A solar panel is a foldable solar panel. It consists of one or more solar modules that are integrated into a fabric bag.

The solar panel can then be set up flexibly in the sun if required. It is then connected to a MPPT solar charge controller by means of a cable, which then charges the battery.

The connection cable is usually integrated in the bag and can also be stowed away there.

What is the advantage of a solar panel for the motorhome?

A solar panel for the RV offers many advantages over a fixed installation of a solar system on the roof of the RV.

• The construction of a solar panel is only necessary if necessary
• The solar panel does not require any space on the motorhome roof
• A solar panel for the RV can be folded compactly and can therefore be easily transported in the RV
• In principle, a solar panel can provide more power than a fixed installation on the roof, since it can be aligned to the sun independently of the parking space and the parking position of the RV. Solar modules on the roof, on the other hand, often have an unfavorable angle to the sun.
• A solar panel enables solar yield even if you park in the shade, because you can still put the solar panel in the sun

The disadvantages of a solar panel on the motorhome

A solar panel also has some disadvantages. In particular, it is less convenient to use than a permanently installed solar system.

• Risk of theft – solar panels are popular and are often stolen
• More effort compared to a roof installation, since you have to set up the solar panel separately after each change of pitch
• Setting up and attaching the solar panel for the motorhome is difficult in strong winds
• It is not always possible to set up the solar panel. There may not be enough space in parking lots – but a solar installation on the roof will still work.

Advantage of a combination of fixed solar system and solar panel

We continue to rely on our permanently installed solar system on the roof of the camper. This saves us from having to set up the solar panel immediately at every stop to cover normal electricity requirements.

On the other hand, thanks to the solar panel for the RV, we don’t have to be restricted by the roof surface with portable solar panels for home. If necessary, we can simply set up the solar panel additionally.

But the solar panel does not only show its advantages in bad weather or when there is an increased need for electricity: thanks to the bag we can now park in the shade and put the solar panel in the sun. On our long-term trip in 2021, we really learned to appreciate the solar panel: In October and November, the yield from the roof system was sometimes too low in Spain too. By aligning it with the sun, the solar panel was able to really increase the solar yield here.

What is the difference between a solar panel and a solar case?

Basically, the concept of the solar panel and the solar case is the same. However, solar cases often use rigid solar modules, heavy and stable metal frames and are therefore more voluminous and heavier than solar panels. From our point of view, the disadvantages of the solar suitcase clearly outweigh the disadvantages for the RV and we would recommend the solar panel.

solar panels for the RV

You can find solar panels for motorhomes for less than a hundred dollar. However, these solar panels then have little power and use dubious components. The mixed reviews show that you have to be lucky to get a product that will last for years without any problems.

We had excluded these cheap solar panels from the start. Our experiences with our permanently installed solar system were so positive that we wanted to go back to branded components.

What does a solar panel for the camper contain?

The usual market offers for solar panels for the RV usually include

the solar panel itself

a solar charge controller

connection cable.

But there are also solar panels that are supplied without a solar charge controller. You may need to buy off grid solar kit. This can be useful if you want to select this separately, or if a solar charge controller is already available.

Battery cables and small parts usually have to be ordered separately.

Do I need a solar charge controller in the RV?

In a nutshell: yes.

You cannot connect the solar panel to your batteries without a solar charge controller.

• The solar charge controller not only converts the (higher) voltage of the solar modules to the appropriate voltage of your body batteries in the RV.
• The charge controller also controls the charging current according to the charging curve that suits your battery type.

It is not possible to connect a solar panel directly to the electric block (EBL) of a RV. With some EBL models, however, the solar trickle charger can be connected to an input of the EBL.

Some solar panels for motorhomes already have a solar charge controller integrated. From our point of view, it is better if you can choose the solar charge controller freely and if the worst comes to the worst, you can easily replace it.

Fast connection of a solar panel to the motorhome with an Renogy connector

An Renogy plug is often installed for a convenient connection of a solar panel to the RV.

• One end of the connection cable is permanently installed on the charge controller installed in the RV.
• The other end hangs on the solar panel.
• With the Renogy connector, you can connect the two cable ends quickly and without tools. If you no longer want to use the solar panel, simply disconnect it again and put the solar panel away.

Connect the solar panel to the existing solar charge controller?

In particular, if you want to connect the solar panel for the motorhome to an existing solar charge controller in the motorhome, you must ensure that it still has sufficient free power capacity.

First, he must be able to handle the total of the Wp specifications. Our roof installation has 220Wp, the selected solar panel has 180Wp. So we need a regulator for 400W.

In addition, the voltage and current must be supported by the regulator. This depends on the planned connection (serial or in series). Some detailed considerations are necessary here, and it is easier to simply install a second charge controller.

Several solar charge controllers on the ancillary batteries?

But what if an existing solar charge controller does not have sufficient capacity for the planned solar panel?

No problem: Then you can simply install another solar charge controller. The charge controllers then work independently of each other and charge the body batteries.

We decided to go this route because it has a decisive advantage: If you only have one (larger) charge controller, you suddenly have no more electricity in the event of a defect/failure. With two (smaller) charge controllers you have a backup available. When traveling to Morocco and other remote regions, this is not an advantage that should be underestimated!

A closer selection of our solar panel options

After a few days of research, two products were still in the final selection. According to the paper data, both solar panels use the same Renogy solar modules that we are already using on the roof. In addition, you can choose the solar charge controller freely in both cases.

In the end, we just wanted to maximize performance, so we looked at which dimensions best suited our intended application.

Our solar panel for the RV

We finally decided on the solar panel “Renogy solar panel”. It consists of three flexible solar modules in a well thought-out fabric bag. We ordered them in combination with a solar charge controller and battery cable.

The ultimate reason for this choice was that the 180W Renogy solar pack fits right behind the Ducato windscreen. This makes it an ideal solar panel for the RV.

Renogy’s modules are not as tall, so they need more width for the same output. This isn’t a problem if you set it up outdoors, but 180W wouldn’t have fit behind the windscreen. We should have gone for a smaller model.

The other components would not have differed too much. As far as can be judged, the same solar cells would have been installed and we would have ordered the same solar controller for both. Either way, you’ll probably get a high-performance RV solar panels and won’t make a wrong decision.

Connection of the charge controller to the battery

Well, and then the battery is finally accessible and we can connect the charge controller.

It is important to keep the distance between the charge controller and the battery as short as possible. On the other hand, it must also be possible to connect the solar panel as easily as possible.

We’ll start with the easy part, and connect the plus and minus of the cable with the Renogy connector at the same time. According to the Renogy instructions, the charge controller must first be connected to the battery, since the controller can then first adjust to the battery voltage. But nothing can happen here yet, because the cable is not connected to the solar panel.

Then we connect the connection cables to the battery. In our case, the minus cable does not go directly to the battery, but to the shunt of the battery computer.

In the meantime, we have to drive to the car electrician to have the battery cable professionally shortened and have a wider eyelet soldered to the negative cable. The supplied one does not fit the shunt of the battery computer.

Also charge the starter battery with the solar charge controller in the RV

With the solution described, we only charge the RV battery. Normally we don’t stand in one place for so long that draining the starter battery is an issue for us.

However, if you also want to charge the starter battery via the solar charge controller, you have several options:

• There are Electroblock (EBL) variants that have a solar input. You could connect the solar charge controller there. That would probably be the simplest variant, because the EBL normally carry out a trickle charge of the starter battery.
• Without a suitable EBL, you can think of a circuit that is similar to what is normally used for charging the batteries from the alternator. This requires an isolating relay that only connects the batteries together during the charging process and disconnects them again when they are not being charged. This can also be done manually with a battery disconnect switch. It’s beyond my skills and if you’re not sure, consult an auto electrician!
• You can use a solar charge controller that has two battery outputs. You connect the auxiliary battery to one output and the starter battery to the other output. The company Renogy is often recommended in this context, and the matching MPPT 250 can also be ordered in a package with the watt-hour solar panel. It’s a convenient solution without tinkering.

Set up the solar panel flexibly with an extension cable

If we could find one point of criticism for the solar panel, then it is the short connection cable. That’s just enough to set up the solar panel in front of the RV or to the left of it. Behind the camper or even further away is not an option as the cable is not long enough for that.

The short cable length is understandable, because the cable is very voluminous. A longer length would have bloated the pack size noticeably. Nevertheless, we had to order the extension cable right away, because otherwise the advantages mentioned (parking in the shade and still enjoying solar power) are only theoretical.

Conclusion on the solar panel for the RV

In principle, with our combination of a permanently installed solar system on the motorhome roof and an additional solar panel, we get the best of two worlds: On the one hand, we have half the capacity permanently available on the roof, which simply always produces electricity when the sun is shining, without any effort on our part. On the other hand, we can cover increased needs with the solar panel next to the camper and get other advantages: We can park the camper in the shade while the solar panel is in the sun.

We chose the size so that we can also operate the solar panel behind the windshield in regions where there is a risk of theft. The performance data speaks for itself and we are now very happy with our solar panel for the motorhome. We only want to use a 12 volt lithium battery later to ensure extended buffer capacities.