Affixing the third solar panel, and installing the 12V electrics

This Saturday a major step was achieved: I added the 3rd solar panel, revised the wiring, and hooked them all up together.

First I taped the panel temporarily with a stripe of black tape, to keep it in place.

Using grommets for the cable meant that I had to cut off the MC4 connectors which were attached to the panel: they were too big for a simple cable hole, and I did not want to create a larger hole for them.

Both cables now are fed inside the Luton box.

Because of the step in the box surface I had to attach a piece of wood, to keep the panel in a straight plain. 

Done. The front solar panel is now connected. Like the other two panels, it is kept by 4 self-taping screws and a large disk. No glue was used; I did not want to spoil the Luton box surface, just in case I would later decide to remove the panels. The two side panels have an additional tape, to prevent wind during driving to go under the panel and lift them off. 

Solar panel on the passenger side.

Solar panel on the driver side. Still with the wire conduit through the bottom of the box.

Driver side solar panel, now with proper grommets as cable conduits. 

Unfortunately I only had grommets for a wall thickness of about 1 mm. But the wall of my Luton box is much thicker: there is an outer metal sheet with approx 2 mm thickness, and then there is another inner metal sheet with approx. 1 mm thickness. This reveals an interesting observation: It appears that at first the builders of this box did construct it from a thin 1mm aluminium sheet. It apparently was decided that this is not sufficient. Maybe it kept bending, making lots of noise. It must have been completed, as that layer is also painted in blue. If that was not used for the outside view, then why would it have to be painted? Therefore I think that this inner thin layer was the first attempt to have this box constructed, and it turned out to be too thin.

Then the outer layer appeared to have been mounted, with a thicker 2mm sheet metal. Affixed on many places to the lower layer with rivets.

And my grommets now cannot cope with this 3mm thick wall... when I push them through, some of them broke off. Here are a few pictures from the inside:  

Later I added some SikaFlex from the inside, to make the opening tight. From the outside, the grommets seem to be undamaged.

I used my thick wires for my home solar installation setup to guide all the solar power to one terminal. This allows me at this central location to modify the connection of how these panels are configured. I opted for putting them all in series.

The first terminal connector set was too small for some of the very thick cables, so I had to replace it with a larger one for 16 sq mm cable conductor cross section.

The technical data of the solar panels:

Interestingly, each of the 3 panels produced an idle voltage of 21.5 V or more, even though only one of them was facing directly the sun, whereas the others were pointing to other directions.

Adding them up leads to a voltage of 66.8V:

When the battery was connected through the controller, the voltage dropped to 29.7 V:

This picture shows how power is produced by the panels: a total voltage in sum of about 30 V creates a current of 1A, producing about 30W of electric power.

Interestingly, this power then could increase even when the battery was connected. This is because once the battery has a consumer attached, its voltage goes down, and then the controller puts its voltage up to re-charge the battery. That is when the controller uses more power from the solar panels. 

So even though my panels are mounted in 3 different directions of the sky, they still produce a total of over 60 V and almost 1V current, resulting in more than 60 W. Some time later this even went up to 70 W.

The voltage at the battery then was 14V.

Current is unfortunately currently not measurable, because of a faulty measurement device. Here it shows 0 A, which is nonsense because the battery is actually being charged. I have already ordered a new measurement unit.

 

I also am now able to produce 230V from the battery with an inverter. This allows me to feed the 230V directly into all my regular power circuits, also using the existing safety infrastructure like fuses etc. 

And now I can run a 12V compressor refrigerator for 24 hours. So I will always have cool drinks in the camper. A very important step!

The temperature in the 2 refrigerator compartments is 7deg and 3 deg. 

Here is the expanded electricity setup, now in addition to the 230 V circuitry the 12V circuits were added. This is all mounted on one single board, which can easily be removed and attached somewhere else. I will eventually re-do this board, with a tighter mounting. There will be a cover door, showing only all the displays and meters.