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Build a small solar panel for 32 Euros!

Do It Yourself (DIY): a small solar panel!

I always like to have a small solar panel which I can take everywhere with me (in the car, the cottage, the excursion and elsewhere) for time of need. I have decided to build a small portable solar panel on my own, with a very low cost of solar cells.

In order for the panel to be small in size and resistant to transfer, I have selected solar cells made from amorphous silicon, which are already in a glass and with ready output wires. They are very persistent (cannot break easily) unlike the monocrystalline or polycrystalline cells that are used in larger panels.

Moreover, each one gives about 4.5 volt without load, compared to the 0.5 volt that the crystalline solar cells can give. This means that I can use only three cells connected in series (positive-negative-positive-negative) to accomplish about 12 volts which was my goal for this panel.

This has a result lower cost, less surface area and easy construction.

Since the current that is produced is about 80mA, I used another two sets of three cells in parallel connection with the other three cells (connecting the free negatives and the free positives of the three horizontal lines between them) to accomplish approximately 240mA.

The result is a total of 9 pieces, total cost of 31.5 Euros (3.5 Euros each cell). I asked to put in the package and a metre of connection material, even though I could use a simple cable.

I could have made the casing from plexiglas, but I preferred the easy (but functional) solution of a plastic frame ... 24X20cm! Small size, lightweight and low cost: just 1 to 3 Euros, depending on the frame.

To be able to connect various devices, chargers and rechargeable batteries, I used a cigarette lighter plug adapter as shown in the picture (which cost not even half a Euro from any electronics store).

I also bought and a small car cigarette lighter transformer with 12 volt input and 1,5 - 3,0 - 4,5 - 6,0 - 7,5 - 9,0 - 12,0 volt output. The transformer (see photo) is in the plug that I mentioned just before.

So I can connect all kinds of devices or batteries from 1.5 to 12 volt with no problem.

The first test was during a sunny day in April, at 15:00. The small solar panel, without any load, produced about 12 volt and 230 mA!. After connecting the AC adapter to the small solar panel, the multimeter showed 11.7 volts.

Perfectly! Certainly the summer months, the performance will be slightly better, but it is fine! Besides more than 15 volt, the converter would have had problems.

The first practical use was to charge my phone using the car charger and the second to charge some rechargeable batteries.

Possible improvements of the solar panel:

I could use more lines of three solar cells for more mA by just enlarging the size of the solar panel. For example, with 9 other solar cells, the current would reach 540mA at 12 volts. Or I could make it foldable for even smaller size!

Note: With this panel you can charge batteries up to 9V. The 12V batteries need charging voltage roughly 14.4 V. So they would need a panel with 5 cells in line instead of 3 cells as shown here. It is good to use a silicon diode, so the current would not return from the battery to the solar panel cells when it is not sunny.