noglider 

I'm with Russell @52telecaster. Modern LED dynamo lights are great. I also use battery powered lights. I tried bottle dynamos (aka sidewall generators), and they are very draggy and noisy. I tried the BB dynamo and ended up putting it on my spouse's bike. It's not quite as noisy or draggy, but it is still annoyingly draggy. The BB unit also can slip under wet conditions. It's perfect for her, though, as it is for riding unexpectedly in the dark, and she doesn't need to keep anything charged. The drag from dynamo hubs is imperceptible though it does add up a bit. It doesn't ever add up enough for me to disengage, though.

I have a hub with a mechanical clutch, so when it is disengaged, there is no dynamo drag. It's an interesting experiment which proves that the kinetic energy cost of the dynamo is always affordable for me.

tcs

BTW, classic and vintage fans: those old Sturmey-Archer GH6s will energize modern LED headlamps. The only test I ever saw including them showed fine efficiency and, as a bonus, you don't have to send one back to Germany for overhaul. You can redo the bearings on your kitchen table (follow the directions!)

Remember: if it's not a Sturmey-Archer, it's not a Dynohub™️!

tractopelle

I just bought a cheap lamp (like the ones that were on the Herse front racks decades ago in the hope of converting it to LED with a Cree kit.
I have no idea if this will work, and I would only use it as a complementary light on the front rack (if I ever find one with the right attachment).