What are the fuses for solar

Install a solar system - this is how it works

You have bought all the components for a solar system and now want to install them. You can find out how to do this and what to look out for here.

Perhaps you have already been to a consultant or have obtained other information and now have all the components you need at home. That's really great. Just how do you start now

Based on the installation of our solar system, we would like to show you how we did it and what you have to pay attention to.


You should know a few electrical basics. If you are completely inexperienced in this area, it is better to have the solar system installed by a specialist or get support from friends or acquaintances who have more experience in the field.

It is important to know that you are de-energizing the solar modules when you connect them, as they immediately generate electricity in sunlight. So either you realize the installation in a hall or you get yourself large boxes or tarpaulins to cover them for this brief moment.

We just picked up the boxes that came with the solar panels. They fit exactly on it and when there is no wind, they stay where you put them.

But now it's down to the nitty-gritty. Make sure that you really have all the components there and that nothing is missing.

With us it was:
5 x 150 watt solar modules (the ones we bought no longer exist)
5 x Bracket set for solar modules *
2 x MPPT 100/30 charge controller
2 x40A vehicle fuse *
1 xBattery monitor
20 m Solar cable(but we didn't use it up completely)
5 m Vehicle line *
3 x Y connector set - compatible with MC4 connector *
4 xSolar connector Weidmüller PV-Stick + and - Crimpless set
1 x Roof duct for cables

In addition, you will of course need the right tools such as cordless screwdrivers, drills, screwdrivers, crimping pliers and side cutters as well as cable lugs and wire end sleeves for cable assembly.

Why 2 x MPPT charge controllers?

Since we are often free and also like to visit countries without a large camping infrastructure, it was important for us to build in redundancy. So we once connected 3 solar modules and once 2 solar modules and each led to the battery via the charge controller.

In the event of a system failure, we still have at least 2 functioning solar modules. Hopefully these will then at least save the electrically operated refrigerator.

The big plan

So that you know how to get started and how to wire everything correctly, you have to know how the individual components have to be connected in the first place.

We have created a small plan for this. In the plan you can also see which cable sizes we used and how all components of our solar system were connected. Such a plan is very practical (can of course also be drawn by hand), because then you can have a specialist check again whether everything has been planned correctly.

Good to know

It doesn't really matter whether you first glue on the solar modules, screw on the charge regulator or lay the cables. It is important to know that the solar modules generate electricity immediately when they are exposed to sunlight. You should therefore only connect the solar modules to the cables at the very end.

Solar modules (and their holders)

First, of course, you have to think about where exactly you position the solar modules. The adhesive surfaces on the roof, like the holders / modules, must of course be clean and free of grease.

First, the exact position of the solar modules must be determined and marked or masked off.

Before cleaning, sand the holders for the solar modules briefly with fine sandpaper so that the surface is a little roughened.

It is generally recommended to lay the modules loosely on the holders on the roof, to mark the exact positions for the holders or to mask them off, to clean the surfaces and to use a Adhesion activator * prepare. The holders are then glued to the previously determined position. Recommended as an adhesive Dekasyl MS-5 *.

The practical set from Dekasyl for preparing the adhesive surfaces

The adhesive activator must flash off briefly before the Dekaseal MS-5 can be applied.

You need a good cartridge gun to apply the adhesive, otherwise you won't have much fun at work.

The Dekasyl MS-5 is ready. Now the holders for the solar modules can be attached.

Press the solar module on. Finished.

To glue the holder you need approx. 1 Dekasyl MS-5 cartridge for 2 solar modules. The Dekasyl MS-5 is also available in practical set * together with the adhesive activator, a pre-soaked cleaning cloth and a sheet of sandpaper. Then you only need additional individual cartridges if you want to glue more than two modules.

When the holders are glued on, the glue has to harden. Depending on the humidity and temperature, it takes about 24 hours for a 4 mm thick adhesive surface.

The solar modules can then be attached to the holder. Depending on which holder and which modules you have, these are attached with screws. This has the charm that at some point, for example, a defective module can be removed and replaced.


We have a completely flat roof without any bumps. That is why, contrary to many recommendations, we screwed the brackets and modules together on the ground in advance. To do this, we pre-drilled small holes in the solar modules and then screwed them to the holder with the screw provided.

We pre-drilled the holes in the solar modules.

The screws for fastening were included.

Then we marked the positions for the modules on the roof. Then we prepared the two adhesive surfaces for one module each with the adhesive activator, let it flash off as described and applied the Dekasyl MS-5. Then we just had to press the pre-assembled solar modules onto the adhesive surface.

Charge controller and fuses for the solar system

In order for your solar system to work properly, a charge controller must be installed between the battery and the solar module. We decided on MPPT charge controllers. These are installed inside the motorhome or caravan.

According to the manufacturer, they should be screwed vertically to a wall so that they are well ventilated. Unfortunately, we do not have a vertical wall in the sub-floor for our technology and have therefore attached it horizontally. This is of course suboptimal and shouldn't be solved that way if possible. The warm air can then get away worse. We still have to test how well this works for us and whether the charge controllers get too hot. Because we weren't sure how warm it would really be under the charge regulator, we screwed the two charge regulators onto an aluminum check plate.

Unfortunately we could not install our MPPT charge controller vertically. We'll test it in a lying position.

The MPPT charge controller with the following 40A fuse

The charge controller is an important link between the solar module and the battery. It should be adequately dimensioned.

A fuse must be attached after each MPPT charge controller. To do this, the fuse is simply placed in the positive cable between the MPPT charge controller and the board battery.

Battery monitor

We have built a battery monitor BMV-712 Smart from Victron Energy into our system, which can show us the charge status of the batteries, among other things.

In order for this to work, it must be correctly wired together with the supplied shunt. The shunt is placed as close as possible to the batteries. How to properly wire the shunt, batteries and co. Can be seen in the plan above. It is important that the appropriate cables and cable lugs are always used. For the large cable lugs, for example on the batteries, it is advisable to use a Hydraulic crimping tool * to work. This means that the cable lugs and the cables are securely and properly connected, and you can do this without great effort.

You install the BMV-712 somewhere in the living room. The scope of delivery includes 10 meter interface cables, which are led from the shunt to the BMV monitor and which transmit the display data. Since you can call up all sorts of information on your mobile phone via Bluetooth, the monitor does not necessarily have to be easily accessible if the cable is too short.

In our case we had thrown out the old speakers and a hole in the wall anyway. At plattenzuschnitt24.de we then had aluminum dibond cut-outs made to measure and with prefabricated cut-outs sent to us and inserted the battery monitor there, thereby covering the old speaker hole.

The roof duct

Of course, the solar cables also have to somehow go from the roof to the living room. To do this, a sufficiently large hole is first drilled in the roof. We ran the cable through one of our cabinets as well as the cladding for a pipe. So it is, so to speak, invisible. In addition, you don't see the unsightly hole in the ceiling and you don't have to cover it up again.

We determined the position of the hole from below and first pre-drilled it with a small drill and then gradually enlarged it with larger drills. Since we set up a redundant system, we had to drill two holes at the same time in order to lead the two double cables through.

The cruelest procedure when installing the solar system is the roof penetration.

A hole in the ceiling. The solar cable is then pushed through here. And because we're building a redundant system, we need the whole thing twice.

If the hole is in the ceiling, the cable must be pushed through and the roof duct installed. To do this, the cable is also inserted through the roof duct and the cable locks.

Then we glued the roof duct over the hole - or the holes. Here you can use the same glue as for the solar panels. But be careful: it is essential to ensure that the adhesive surface is completely closed and therefore tight. This is the only way to ensure that no water can get into the interior. When the adhesive has been applied, the roof duct is glued over the holes and pressed on. Now it must not be moved until it is completely dry according to the data sheet.

The cables are pulled through the roof duct.

Then the glue comes on the underside of the fold.

Then the roof duct is glued on. If the glue oozes out all around it can be seen as positive. Then at least it's tight.

The big moment: clamping the solar system together

Once the roof duct, charge regulator, shunt and battery monitor as well as the corresponding fuses have been set and correctly wired (see plan above), then only the solar modules need to be connected to the system.

The best way to do this is to cover the modules so that they are de-energized (if you are not in a hall anyway). We also triggered the fuses after the charge controllers for this brief moment.

The solar modules each have a pre-assembled plug. In order to connect several solar modules in parallel, they are connected with Y-connectors. Here, the plus cables are brought together once by means of Y-plugs and the minus cables of the solar modules are brought together once and then each led to the charge controllers.

A solar connector must be fitted to the next cable behind the Y connector. The solar plugs from Weidmüller that we used are "crimpless". That means, you just have to strip the cable and insert it into the connector. There they anchor safely and firmly - without any tools.

The Weidmüller solar connectors that we used are "crimpless".

You just have to plug in the stripped cable.


When all cables are connected, the solar modules are released from the boxes and the fuses are reset. Everything should work now. The solar system can now produce electricity and feed it into the batteries.

We will now test our system for some time and then tell you how well the 750 watts with the complete solar system in the motorhome have proven themselves.

Further topics on the subject of solar systems

More information can be found here: Solar system for the mobile home

Have I forgotten something important? Did you do something differently and why? Write me in the comments.