5 ms·

I would hope they designed it where you can keep riding. It seems possible. Pick some charge level (say 20%) and provide less and less power assist as you appro

I would hope they designed it where you can keep riding. It seems possible. Pick some charge level (say 20%) and provide less and less power assist as you approach that. Once you hit 20%, a control system tries to keep it about 20% charged. Basically you enter a mode where the battery becomes a buffer (between the pedal and wheels) rather than a power source. The bike would feel sluggish, but it wouldn't stop working.

mrtesthah 1y ago
You'd have to pedal rather hard (equivalent of riding 21.7 mph) to provide 250W of power[1], which is the minimum for most ebike motors. 1. https://a2zcalculators.com/science-and-engineering-calculators/stationary-bike-watts-calculator https://a2zcalculators.com/science-and-engineering-calculato...
- chabons 1y ago
  "rather hard" is really underselling things. Without considering generator->motor losses, 250W is a lot of power, even for a larger (>80kg/176lbs) rider. For basically anyone who doesn't train on the bike, this is an unsustainable effort. Even a floor of 100W would rule out smaller/less athletic riders.
  - esseph 1y ago
    176lb is below the average male weight in the US by around 25lbs :(
- Retric 1y ago
  Constant 250+W would force you to always travel at high speeds. That’s just not how E-Bikes operate. Even 50W is a fairly significant boost for casual riding.
- actionfromafar 1y ago
  And once you are up to speed, you coast. Even on a normal bike. With the battery as a buffer, the ebike could easily bump you up to speed and use 250W or more for just a little while and then 0W for stretches. You don't need to sustain 250W pedalling.
- adrianmonk 1y ago
  My reasoning that it's probably doable was based on efficiency. What is the end-to-end efficiency of the generator, electronics, and motor combination? If it's 75% efficient, then you need to pedal 33% harder than normal[1]. If it's 66% efficient, then you pedal 50% harder. Unfortunately, I can't find real data, so those efficiency numbers are guesstimates. Electric motors and generators can be very efficient, and I would hope that they'd use efficient ones for an application like an ebike. As a point of reference, pumped hydro can be 70-80% efficient[2], and that involves a motor, a generator, and mechanical losses. That's not an apples to apples comparison, though. --- [1] Where normal means a 100%-efficient link between pedals and wheel. Actual bike chains aren't, but they appear to be 95% or more. [2] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...

mrtesthah 1y ago

You'd have to pedal rather hard (equivalent of riding 21.7 mph) to provide 250W of power[1], which is the minimum for most ebike motors. 1. https://a2zcalculators.com/science-and-engineering-calculators/stationary-bike-watts-calculator https://a2zcalculators.com/science-and-engineering-calculato...

chabons 1y ago
"rather hard" is really underselling things. Without considering generator->motor losses, 250W is a lot of power, even for a larger (>80kg/176lbs) rider. For basically anyone who doesn't train on the bike, this is an unsustainable effort. Even a floor of 100W would rule out smaller/less athletic riders.
- esseph 1y ago
  176lb is below the average male weight in the US by around 25lbs :(
Retric 1y ago
Constant 250+W would force you to always travel at high speeds. That’s just not how E-Bikes operate. Even 50W is a fairly significant boost for casual riding.
actionfromafar 1y ago
And once you are up to speed, you coast. Even on a normal bike. With the battery as a buffer, the ebike could easily bump you up to speed and use 250W or more for just a little while and then 0W for stretches. You don't need to sustain 250W pedalling.
adrianmonk 1y ago
My reasoning that it's probably doable was based on efficiency. What is the end-to-end efficiency of the generator, electronics, and motor combination? If it's 75% efficient, then you need to pedal 33% harder than normal[1]. If it's 66% efficient, then you pedal 50% harder. Unfortunately, I can't find real data, so those efficiency numbers are guesstimates. Electric motors and generators can be very efficient, and I would hope that they'd use efficient ones for an application like an ebike. As a point of reference, pumped hydro can be 70-80% efficient[2], and that involves a motor, a generator, and mechanical losses. That's not an apples to apples comparison, though. --- [1] Where normal means a 100%-efficient link between pedals and wheel. Actual bike chains aren't, but they appear to be 95% or more. [2] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...