Do I need dedicated Road bikelight with StVZO-approval?

That depends entirely on what purpose you are pursuing. In the field, the luminous image of the Piko / Wilma / Betty is clearly at an advantage, since you see, for example, even hanging at head height, branches perfectly. On the road, the safety concept prevails: After all, you do not want to blind other road users and at the same time benefit from good illumination on the road. Here, the advantages of the SL(Nano / F / X) outweigh the disadvantages.

Can I also use my SL X (SL F/ SL Nano) on an external battery?

No, the SL AX (AF/ Nano AF) was designed for this purpose.

What is it about voltage and light output?

E-bikes have different light outputs, each with different voltages and amperages. Depending on power and voltage of you light output, the SL X shines for example with 1600 lumens or 1800 lumens.

Can I reverse the polarity of the SL X/SL F/ SL Nano if I mount it incorrectly?

Yes, but don't worry. Each SL has reverse polarity protection and will simply shut off if mounted incorrectly.

My SL (X/F/Nano) is mounted on an e-bike and does not light up?

Most likely, + and - were reversed: see above. In addition, the light output of your e-bike must be enabled. To do this, you should contact your regional e-bike dealer. They will activate the light output of your e-bike.

What is the difference between the German and the international SL F?

The international version is largely the same as the StVZO version, with some additional features: The international version has an additional RVLR mode, in which the headlight flashes to be seen even better. The daytime running light of the international version shines individually with 0.4W or optionally together with the main headlight and thus provides better illumination at close range. Glare-free, however, is every SL.

The lens of my SL(X/F) fogs up. Is this normal?

Yes, the SL(X/F) can fog up slightly in the center of the lens. This disappears after a few minutes of use.