3 ms·
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
by jeffbee 1y ago
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.
- big_toast 1y agoNot 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.
- jeffbee 1y agoYes, 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.
- emil-lp 1y agoLet's say 130kg (80kg driver + 50kg bike) going 30km/h (e-bike limit) is ~1.25Wh.
- big_toast 1y agoDoes 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?
- adgjlsfhk1 1y agoThe difference is that humans (unlike motors) have pretty low max power limits.
- big_toast 1y agoI 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.
- edaemon 1y agoWhat 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.
- jeffbee 1y agoIt isn't free. How could it be free? It requires at least an electronic control system and a pressure sensor.
- LoganDark 1y agoIt was already going to have some sensor for, say, the brake light.
- 01HNNWZ0MV43FF 1y agoAre there popular e-bikes without electronic motor control?
- edaemon 1y agoIt'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).
- numpad0 1y ago3-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.
- cyberax 1y agoIf 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.
- CorrectHorseBat 1y agoMy e-bike has regen braking and it's definitely noticable, but I don't know how much it helps
- mvkel 1y agoBoosted 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"
- jeffbee 1y agoThe 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.
- Spunkie 1y agoI 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.
- nradov 1y agoHow are you shredding brake pads every month?
- Spunkie 1y agoMy 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.
- skeeter2020 1y ago>> a 30% grade is like the average hill here. So the steepest roads in the world have small sections where the grade exceeds 30%; none maintain it or "average" 30%.
- nradov 1y agoSeriously. Even the Mauna Kea volcano climb doesn't have 30% grades. https://www.strava.com/segments/1504789 https://www.strava.com/segments/1504789
- Spunkie 1y agoYa 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.
- jeffbee 1y agoDo you sell many trombones?
- Izikiel43 1y ago> The energy balance simply does not favor regenerative braking on a bicycle Here in Seattle with all the hills it might
- skeeter2020 1y agoit 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.
- doctoboggan 1y agoThink 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.
- gnarcoregrizz 1y agoagreed. regen does nothing on my e-moto. i'll drop 5000 feet in elevation and the battery percentage doesn't go up.