[charles_f]

Dynamo is the general term for electric generators from mechanical displacement. I'm not talking about the small contraptions that power lights on a bike, these are traditionally even worse in efficiency.

Lets be charitable and call it 90%, it's still going to charge the battery (which is described as a buffer), and that will have a max of 95%, discharge the battery, same, and power the motor, which has likely the same efficiency. You're at. 9.95.95*.9 = 73% efficiency at motor output. You're giving 27% to the gods of thermodynamics, unless you like the extra complex cardio you're getting, I don't really see the point. Regular bike transmissions are not free either, but they're closer to 95%.

Thinking about all that, I don't get why they didn't use a hub motor. Why adding a belt when you could have transmitted the power directly to the wheel?

[nimos]

Your original post says 70% loss, i.e. 30% efficiency. In the context of an e-bike, to me, 70% efficiency is fine. It's a large bike and the majority of the power for the majority of users is likely going to be coming from the battery anyways.

Also presumably we should be comparing the efficiency to other ebikes not traditional bikes. I'm not sure how effective traditional ebikes are at integrating motor + human power together but I'd imagine there are some additional losses.