The question doesn't relate to my personal use - just looking for info.
My only experience of bike dynamos is as a kid - which is quite a few years ago now - where they used a heavily sprung knurled drivewheel squeezed onto (into) the side of your tyre. They were horrible draggy bastards, and you had to physically stop to pull the unit off the tyre, as trying to do so on the move either removed the skin from your fingertips, or you found your fingers in the (moving) spokes. This was a right PITA when you really wanted to retain any momentum you had built up.
I see modern versions instead run off the wheel rim (using a rubber o-ring for grip). I understand they are far more efficient (thank fook), but assume
1. You still need to physically lever them off the rim to fully remove the drag (ie no handlebar mounted actuation of unit in contact / in free air).
2. They can slip if the rim is dirty/wet
I see you also now get wheel-hub dynos - which look like a cool concept. My understanding is (compared to current rim-dynos)
1. More expensive
2. Unaffected by dirty/wet conditions.
3. Less power output than rim dynamos (?)
4. Drag is proportional to electrical load. So you could have a handlebar mounted switch to cut off the electrical load completely for climbing gradients - reducing drag to "almost zero"? (Possibly also true for modern rim-mounted?)
Any help much appreciated!
This was not really ideal IRL when you need to stop at traffic lights etc. Modern light systems will have a small battery to cover that, and the hub will both power the lights & keep the battery topped up. IIRC you can even get USB dongles to (slowly) charge your phone or whatever while you're riding.
