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Which is the right solar panel for my RV

Solar modules are exposed to higher loads on RV than on a roof-mounted at an angle. On the RV, solar modules come into contact with trees, and snow loads pile up on the module because they cannot slide off.

In order not to overload the glass surface, it is important that such a 400 watt solar panel is not too large. So it is better to install a more compact solar module on the camper, and a solidly built one. Our solar modules are built with a 40mm thick aluminum frame – this gives them a special rigidity.

We rely on solar modules from Renogy. A solar manufacturer from Reutlingen manufactures particularly robust modules for mobile use in RV and especially for long-distance RV.

How much does a solar system for my RV cost?

Use solar panels on the RV space

Quality comes at a price – but don’t blindly buy the most expensive one on the market just because it’s black and has something “camping” written on it. My experience is: that if you don’t want to worry about it anymore, you should pay attention to healthy quality when buying.

Renogy solar modules are among the most reliable in this sector. We have also had the best experiences with MPPT charge controller from Renogy over the years. They are just devices that also have to work in industry and on off-grid systems – and not just when camping with an RV.

Incidentally, we also use what we sell ourselves: for years we have been self-sufficient in our RV, thanks to off grid solar system kit from Renogy, charge controllers, and batteries from Renogy.

How big does the charge controller have to be?

There is a formula for this:

Peak performance of the solar module: average charging voltage (13.5V or 27.5V) = solar controller performance.

So e.g. 150Wp : 13.5V = 11.11A

That would mean that we select a 75/15 MPPT charge controller for a 150Wp module and a 12V on-board voltage.

In practice, however, it will be the case that we only reach the peak power of 150Wp in rare cases: when the air is clear and cold and the sun is very high. That’s not very often the case, so you can count on 75% of the peak power. The optimized and practical formula is therefore:

Peak power : charging voltage x 0.75 = solar controller power.

So e.g. 150Wp: 13.5V x 0.75 = 8.33A

According to this calculation, the smaller and cheaper Renogy 75/10 MPPT charge controller would be perfectly adequate.

A solar charge controller must therefore always be large enough to be able to supply at least solar power under normal conditions over a long period of time. That means: that 75% of the peak power of a module is the realistic continuous charging current over midday.

Heat, humidity, and air pollution naturally lower this value, but clear and cold days can also increase it. MPPT solar charge controllers from Renogy can also be operated with excess power, the solar controller reliably limits the charging current to the maximum value. You may need to know about batteries in series vs parallel.

What kind of charge controller do I need for my solar system?

The solar charge controller depends on the power (A) and open-circuit voltage (V) of the solar system. We prefer to connect the modules in series to minimize the disadvantages of partial shading and to have a much easier connection of the modules. This series connection increases the module voltage. The charge controller must be able to handle this added voltage of the modules.

When determining the right solar charge controller, it should be noted that the no-load voltage of the modules is specified at 25°C. Each degree Celsius less increases the voltage by about 0.3 volts. To determine the right solar controller, you should plan a good 10% upwards. So if four modules in series give 98V open-circuit voltage, a Renogy controller with 150V solar input voltage is required. The controller with 100V would be too tight.

Basically, the MPPT charge controllers from Renogy have a high input voltage range of 75V and 100V. Special models can even be 150V or 250V. Renogy wouldn’t build such controllers if it didn’t make sense to connect solar panels in series!

After the voltage, the solar controller must also be able to process the power. You can easily calculate this by dividing the system output Watt peak (Wp) by the charging voltage of 13.5 volts or 27 volts for the 24V vehicle electrical system. The result is the maximum charging current that the solar controller has to process.

How much solar should it be?

You can never have enough watts in solar. True to the motto a lot helps a lot! When the weather is bad, only the sheer mass of solar power helps to cover the electricity demand. Unfortunately, solar modules only work with sunlight, and if this is only weakly available, the solar system will no longer supply anything. You may need to use a solar calculator.

In my buying guide for solar systems and battery capacity, I described how many watts really make sense for the RV.

But let’s not fool ourselves: space and budget limit the size of the solar system in RVs in most cases. That’s why many of my customers put whatever fits on the roof, especially when it comes to “off-the-shelf RV”, and also installed portable solar panels for home. Roof hatches, satellite systems, and fan modules do not make it easy – but precisely because of these “space robbers” on the RV we have solar panels in so many different sizes on offer.

And if it doesn’t fit and you just want a little more solar, then there’s always the folding module. The foldable solar module, also produced in Germany, is very popular as a primary or secondary solar system for the camper. Especially for the campers, who like to be out and about when the sun is low. Like wintering in the south.

Mobile or fixed solar system for the RV

Many of our customers are toying with the idea of not installing an ordinary solar power system on their RV, but relying entirely on a mobile solution. Actually, our foldable solar panels are very good and can meet the daily electricity needs.

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