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Electric generator->battery->electric motor drive train should be fairly efficient. I'd be surprised if it was lower than 80%. Traditional dynamos are fairly s

by nimos 1y ago

Electric generator->battery->electric motor drive train should be fairly efficient. I'd be surprised if it was lower than 80%. Traditional dynamos are fairly small parasitic loads and not really comparable.

buenzlikoder 1y ago
Normal bicycle drivetrains have efficiencies around 95%...
- mark-r 11mo ago
  Haven't there been studies showing that a bicycle is the most efficient form of movement available?
phkahler 11mo ago
Thats called a series hybrid and it kinda sucks. Motors only reach high efficiency at high loads, and you have 2 of them between the feet and wheel. That configuration is bad when the battery dies because you will feel that inefficiency.
IshKebab 11mo ago
> I'd be surprised if it was lower than 80%. 80% is really bad for a bicycle. A well-maintained bicycle drive chain is basically 100% efficient.
charles_f 11mo ago
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 11mo ago
  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.

by nimos 1y ago

buenzlikoder 1y ago

Normal bicycle drivetrains have efficiencies around 95%...

mark-r 11mo ago
Haven't there been studies showing that a bicycle is the most efficient form of movement available?

phkahler 11mo ago

Thats called a series hybrid and it kinda sucks. Motors only reach high efficiency at high loads, and you have 2 of them between the feet and wheel. That configuration is bad when the battery dies because you will feel that inefficiency.

IshKebab 11mo ago

> I'd be surprised if it was lower than 80%. 80% is really bad for a bicycle. A well-maintained bicycle drive chain is basically 100% efficient.

charles_f 11mo ago

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 11mo ago
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.