Regen braking is how you can tell this was designed by a moron. The energy balance simply does not favor regenerative braking on a bicycle, especially a bicycle that flippantly ignores aerodynamics like this one does. A bicyclist loses roughly all of their energy to air resistance. It's not a truck. There is not substantial potential energy to be recaptured going down hills.
What do you mean? The regenerative braking only kicks in when you engage the brake lever. It's not going to add much range but it's free, I don't see any downside to including regenerative braking.
You're going to have a difficult time pulling a lot of energy out of the back wheel as you're slowing down. The more you decelerate the less weight you've got on your back wheel. Eventually you reach the maximum energy transfer from back wheel contact patch into the motor and lock up the back wheel, and even then you may not have considerably slowed the bike.
Regen on the front wheel would be most effective - but then you've got two motors or a less-than-ideal front motor that adds unsprung weight and has similar traction issues during acceleration as the front unloads.
It's a shame - I think a lot of people want ebikes to work, but they're not as convenient as a pedal bike (especially not in small apartments) and usually they're too heavy to really use in blended pedaling/e-assist mode.
As other commenters noted, rear wheel regenerative braking doesn’t work very well. But there are more problems: most mid-drive e-bikes fundamentally can’t regeneratively brake at all: the rear hub freewheels and cannot drive the motor. Even ignoring that, the chain/belt frequently also can’t drive the motor because that would cause the pedals to drive the motor, and a lot of e-bikes are designed to be pleasant to ride with the motor off, and the rotor has rotational inertia and often has drag as well.
It's not free in a bicycle - it requires significant design compromises in the drivetrain because normally the rear hub has a freewheel to keep it from being back-driven (this may be part of the reason they went for "pedal-by-wire").
On a vehicle like this, which resembles a bicycle but is not one, it's free to implement regenerative braking. It already has all of the necessary components.
3-phase motors are controlled by torque commands into the driver. Give it a value and it generates requisite voltages to fill the gap between current state and desired state. Give it a positive value and the driver spins up the motor, give it a negative and it artificially spins down the motor progressively by commanded amounts. So especially off-throttle regen is completely free. IIUC.
It's the same control system that operates the motor. The motor is just being used as a generator.
I'm not sure which pressure sensor you mean, like in the brake lever? E-bikes with hydraulic brakes already have sensors for power cutoff (and in this case for brake lights).
If you engineer it properly, it doesn't add _any_ weight or complexity. All you need is a bit different arrangement of power transistors and some software.
Why existing bikes don't use it? Because you need software or a more complicated controller, and the amount of regenerated energy is indeed not that large.
Think of regen braking as a way to save an expendable part (brake pads). Instead of dumping your kinetic energy into heating up some brake pads, you can dump your kinetic energy back into the battery. That it happens to recharge (likely only a few small percent) is just a bonus.
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.
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?
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.
it has nothing to do with the hills; it's the mass and the power output of the system. Bicycles are light and humans (even with electric pedal assist) are weak.
Boosted Boards have regen, and in typical use, it extends range by about 10%. It was an incredibly intuitive system; instead of brakes, you regen your way to a stop.
I don't see how this would be any different. Or, it's certainly not "moronic"
The Boosted board imbued the word "moronic" with layers of meaning that it previously lacked. In particular its regenerative brake, with its penchant for sudden disengagement, literally killed riders.
I find regen exciting for it's ability to slow down my brake pads getting shredded every month. The fact that I get some energy back from it is mostly a bonus.
My town is on the side of a volcano, a 30% grade is like the average hill here.
That combines with the heavy weight of an ebike, another 50lb+ of cargo in the saddlebags, plus my exceptionally fat ass means I burn through a pair of front brake pads about once a month if I'm running errands most days.
Ya sorry I always get it mixed up with the % grade thing.
When I'm in my car the dash reads on the hills here between 12° all the way up to 16° on the switchback into the valley. The new market is up a 14° hill.
So closer to ~24% grade average maybe? It's damn steep is the point regardless.
It wasn't quite monthly but on my radwagon 4 I would change the pads every other month at least. Hauling two kids around SF on a heavy bike plus a little bit of poor design on Rad's part.
