Originally Posted by unterhausen

The slip ring idea is mostly about cleaning up the bike and an homage to the past, at least for me. For reliability, running a wire externally is the most repairable, but there is some potential for snags. I have never had that kind of problem though, and I run dynos on all my off-road and all-road bikes. I have thought about adding mounting loops for the wire, but never done it. A slip ring is just unfamiliar. I take it that there are examples that have been in service for many decades without issue, so that gives me some confidence. There is a lot to be said for wires completely concealed inside a frame. rhm and I and 50 of our closest friends did a ride at the end of summer where our bikes were transported and moved around by other people. Nothing happened to my bike, but it wasn't without stress.

If you ever look at the circuits inside dyno lights, most of the good ones are ridiculously complicated. Input protection is key. I had a supernova that disassembled itself, so I looked at the circuitry. It scared me so much I just put it back together and shipped it off to Peter White. Crummy light anyway. I took apart a BuM taillight to remove the fixed ground connection, and it was more complicated than I thought it should be. And that taillight isn't rated to be used by itself without a headlight. I'm still interested in taillight design, but I gave up on headlight design once I became a convert to the joys of shaped beams.