Dahon joule II dynamo hub
 

Bought this, my first dynamo hub. Feels like having a lot of resistance, as if breaks sitting on rims. Is that normal?

Martin

It is just the magnets in the dyno hub stopping the wheel because of their magnet attraction. At riding speed you will never feel or notice it. Almost all if not all dyno hubs do the. Roger

what he said

You should feel a notchiness when you spin the wheel by hand. There is some drag on the wheel from the dyno hub, but it is typically not noticeable when riding.

Aaron :)

At the risk of irritating some others by resurrecting this old thread, there is a report on renovation of a Joule hub on "Hubstripping" here: https://hubstripping.wordpress.com/2...le-dynamo-hub/
This was a Joule I hub, and the process may not apply to Joule II hubs. Joule III hubs are made by Shutter Precision, and apparently can be overhauled by the factory. I haven't had the opportunity (read "need") to service my Joule III.
Note that all these hubs have a "notchy" feel to them when you spin the axle off the bike. This is from the strong attraction between the rotor (magnets with many "poles") and the stator (coils). Once the wheel is on the bike, it spins much more freely, though it spins down faster than a non-dyno hub. When you ride, you will not notice the resistance, even with the light on.
I recently found a SP hub on sale and picked it up for future building into a wheel for my road bike. This brand-new hub feels like a pepper mill when the axle is turned!
Steve