Basically has the same build as a homemade wind generator, with a disk with magnets on them, and coils inside the spinning magnet hubs to charge everything. Its an interesting build, not so sure I would do it (need to widen out your fork on the bike for example). Also this will introduce a “drag” to your bike so it will reduce your speed. Still a nice idea. …me, I think I will stick with the old magneto chargers you can still get for bikes for under $20.
https://hackaday.io/project/163674-contactless-5-watt-bike-dynamo-generator