Item — HN Reader

Not a big cyclist but is that still true for lower speed city riding (typical to flat european cycling prone countries), hillier SF, or mountain biking?

It seems obviously true to typical racing or distance scenarios. And i notice the wind even at lower speeds on e-bikes in SF.

But between their quad scenario and what I imagine as the urban car replacement scenario it doesn't seem as obvious.

1 comments

Yes, it is true at all speed and under all conditions. The system simply does not have the mass that would give it a great deal of gravitational potential energy, and it reaches a power equilibrium with the air at low speeds. Example:

100kg rider at 15 kph = .24W-h kinetic energy. At this speed there is probably roughly 11N of air and rolling resistance, so the steady state power is about 3W-h per km. If you go 1km between stops, or more, the amount you can expect to gain by regeneration is extremely small. It could perhaps extend your range by 5%, generously.

Does that assume no pedaling though? In my experience the pain of starts and stops dominates the joy of steady state pedaling. Presumably the 3Wh/km is free/"exercise" or some portion. Whereas the .24Wh (re-gainable w/ some loss) is all sweat and pain imo.

If I'm understanding the math, maybe that scales the regenerative range extension % by your tolerance for pedaling?

The difference is that humans (unlike motors) have pretty low max power limits.

I assume this comment in relation to the starting from a stop being unpleasant?

If it's w.r.t. effect of low max power on low cumulative generation, I agree it does seem like a little silly to arbitrage your power generation this way. But maybe the tradeoff is worth it in some circumstances in their view?

Or maybe it's just a low cost addition as other commenters say.

Let's say 130kg (80kg driver + 50kg bike) going 30km/h (e-bike limit) is ~1.25Wh.