The fischertechnik solar power modules like this one (2V x 200mA = 0.4W) are often too weak under non-ideal conditions to do anything meaningful with them. This is an alternative more powerful 1W module (6V x 166mA). You can easily chain several of them to increase power to the needed level.
It uses a 60x110x2.5 mm solar module which you can get from ebay international shops for small money. You'll need a couple of male and female pin headers in addition to the printed part (see images).
To get more power, you can chain two adjacent modules with a simple two-pin 15mm male header (push the plastic part to a middle position) or a male-male dupont cable. If you use a cable, be sure to watch out for correct polarity.
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Find my other fischertechnik designs here.
PRI-MAT 3D (from ebay) PLA
Yellow Green - RAL 6018