Why is Regenerative Pedaling not a thing yet? Or am I just overthinking this?
Posted by RevolutionaryCar8623@reddit | ebikes | View on Reddit | 129 comments
Okay, hear me out. Maybe this is a dumb question, but I’ve been obsessing over this for days: Why can’t we charge our e-bikes just by pedaling?
I'm talking about a "Storage Mode" where you can just switch the motor off and pedal like a beast. You get a massive workout, the resistance charges the battery, and you still get to your destination. Then, when you’re actually tired or hitting a hill, you switch back to "Discharge Mode" and use the energy you just created.
It feels like a win-win, right? You’re basically a human generator.
Also, while we’re at it—why aren’t solar-panel front baskets a standard thing? Even a trickle charge while parked in the sun seems better than nothing.
Is there some law of physics I’m ignoring here (like, is the energy return just too tiny to matter?), or is the tech just not there yet? I’d love to know if anyone has tried to DIY this or if it’s just a total pipe dream.
MrGruntsworthy@reddit
You just described how the ALSO ebike works lol
Aequitas720@reddit
This is a probable feature on the TM-B: https://youtube.com/shorts/lPD3J_oH8QM
terraherts@reddit
That bike is a borderline scam lol
I'm sure it's technically functional, but the concept is hilariously impractical to anyone who understands the first thing about how bicycles and motors work.
Typical silicon valley solution in search of a problem meant to appeal to clueless upper income people who will probably only use the thing once in a blue moon
BabyWrinkles@reddit
I know a few folks who have ridden them at events and universally everyone loves it. I don’t love the aesthetic, but I do love the utility. Will be really curious to see how they’re perceived once they’re out.
stormdelta@reddit
I hate how overrun Reddit is now with obvious paid ad bots like this.
stormdelta@reddit
And those bikes are extremely stupid to the point I'd call it borderline grifting.
They're meant to appeal to people with more money than sense and who know nothing about bikes or mechanics.
benthair2@reddit
The guy who owns e-bikes.ca calculated how much energy regeneration would return, and it wasn’t enough to offset the cost of circuitry to prevent overcharging a full battery. The significant factor was that ebike + rider weight isn’t enough. Cars and trucks are a completely different ballpark.
NooberOnABike@reddit
A good example of energy loss can be seen in the YouTube video of the guy that put a flywheel on his bike to store pedaled energy.
fishling@reddit
Yes, entropy. :-) No matter what, you're better off just pedaling directly. Pedaling to charge the battery to push you later is always going to be worse, when your overall goal is moving from one place to another. It has to be.
If you were at home and wanted to do extra pedaling to charge your battery instead of plugging it in, that would work. Same inefficiency/losses, but since you aren't trying to also go somewhere at the same time, it's kind of irrelevant. Being a human generator works fine.
ggezboye@reddit
Regen Pedalling means: 1. Mechanical to electrical 2. Electrical to chemical - storage only. When you want to use it you go further... 3. Chemical to electrical. 4. Electrical to mechanical
All those has losses. Huge losses in fact.
Recommendation:
Why not use your pedalling force and transfer it directly to the wheels and call it a bicycle.
SoNerdy@reddit
Exactly. Why over complicate something already so simple.
That being said… regenerative breaking on hub motors…
PM_SMOKES_LETS_GO@reddit
Just for the fact that it would give your brakes so much extra life
MeeyuhLol@reddit
Tbf, I replaced my organic disk brake pads with metallic/sintered ones on my commuter last year and there's still a ton of material left on them. Considering they are only what like £20 generally, I don't think regen braking would really do much to help the service life of an already long lasting component. Regen braking would probably only help reduce glazing from overzealous braking
sparhawk817@reddit
Direct drive hub motors only though
throwaway_2_help_ppl@reddit
Are you suggesting that isn't a thing? Because it is. check out ebikes.ca GMAC
SoNerdy@reddit
I know it’s a thing, and would be far more effective than trying to charge via pedaling. it’s just not super common.
shmianco@reddit
because our bodies create huge drag without adding a ton of weight - unless technology has improved dramatically but i always figured regenerative braking on a bicycle is a non starter for those reasons
SoNerdy@reddit
I think it’s something that ends up being more viable for the stuff that should probably be classified as e-moto
Revolutionary-Half-3@reddit
Afaik it's mostly because many hub motors have reduction gears and an overrunning clutch, to reduce resistance when the motor isn't active.
Well, and because a controller that can do it is a bit more sophisticated, and many batteries can't accept a charge fast enough. My XP 2.0 has cells that can discharge at 20A but only charge at about 3A.
throwaway_2_help_ppl@reddit
yeah. it's also very expensive. And you're not really gaining much, sure you save on brake pads, but they're $10 a pair and they last thousands of km
stormdelta@reddit
I like not having to even worry about the brake pads, and it also acts as redundancy with the physical brakes + I find it's easier to avoid wheel lock during emergency braking.
To me it really only makes sense with direct drive hubs both for practical reasons since the GMAC is the only commercial geared hub it's possible with, and because the advantages align with the same reasons you'd want to use a direct hub (reliability / low maintenance).
OBLIVIATER@reddit
My rad City 3 has this, it's nice!
stranger_trails@reddit
Exactly. If my battery dies I don’t want to loose potentially 40%+ of my total work to the system of mechanical-electric-chemical-electric
Upbeat_Amount673@reddit
Not exactly regen pedaling but Bionx used to have regen motors.
It sucked for multiple reasons but main being drag. Magnets in the motors made tons of drag when it was enabled but also when off there was still noticeable drag. It also provided next to no additional power for the battery. Only benefits I'd say were "engine brakes" for going down hills and that if the battery was at 0 and wouldn't charge you could pedal like a madman in place and spin the motor enough where the charger would detect a slight voltage and start wall charging. Canadian company so I worked on tons of them and would never suggest re-Gen as a feature today.
The drag from the motors was also "notchy" because of the magnet placement
rovingdan@reddit
I agree. I’ve got a yamee bike with a regen motor. It goes into regen when you brake and speed drops below 15 mph. Cool for slowing down without doing much braking with the discs but in terms of energy recovery, practically useless.
Regen is 64 watts which is the same as the charger. The charger takes 5-6 hours to recharge. So unless you are going down a long hill for at least 2 hours it’s pointless.
Few-Professional6651@reddit
dude fr just pedal and enjoy the ride, no need to complicate it
Just-Smart-Enough@reddit
Gasp.
infiz@reddit
https://ridealso.com this bike company that has spinoff of Rivian has an electric motor that’s powered by the peddling
stormdelta@reddit
And that bike is very stupid for all the reasons people laid out in this thread.
You're doubling efficiency loss for no benefit, adding an incredibly amount of complexity where if anything goes wrong the bike is completely inoperable, and it's all hyper proprietary and impossible to repair by any normal person or bike shop.
It's the kind of insanity that could only be cooked up by silicon valley grifters.
infiz@reddit
No benefit?
No cassette to replace No chain maintenance
Batteries have gotten so good that you can power a ride entirely on throttle, but this bike allows you to get exercise and control the speed based on pedal speed. The fun of a bicycle but the tech of a modern e-bike. It’s different but not stupid. Definitely some benefits to this design.
stormdelta@reddit
You sound like yet another Rivian marketing bot lol
Drivetrain maintenance is already low for any hub drive setup, and you're replacing what would be relatively straightforward maintenance with something hyper-custom that no normal person or bike shop can work on and which will cost an arm and a leg to fix.
Especially since you now have two separate major electronic components instead of one, for generation and drive.
So does literally every other e-bike out there.
Yeah, and? That's not unique to Rivian's shit, that's any e-bike with a throttle and a decent battery.
None that you can't already get with a decent hub motor setup, and the list of disadvantages is pretty severe.
dark_roast@reddit
Some ebikes had regenerative braking. Early Rad City models specifically I know had it. They were fairly heavy gearless rear hubs, and from my understanding the gearless nature made it easier/cheaper to engineer the regenerative braking into the motor.
Rad moved away from those and to more conventional geared hubs, and for whatever reason those are harder to build with regen. It didn't sound like the regenerative braking added a ton to average range.
Bringing solar cells along for the ride has a similar problem with bikes as cars - the added weight of the panels + electronics, plus the added cost of everything, is not likely to be worth it vs the added cost/weight of a slightly larger battery pack.
StrangerGeek@reddit
I have a radcity with Regen braking. It tops out at 250W and only really works for a few seconds at a time. It saves wear on the physical brakes on long downhills but that's about it. The wall charger runs at about 120W so you're saving yourself a few minutes of recharging at best. And of course the motor output eats back up what you charged much faster at 500W.
Overall it's pretty nifty but as I understand it they switched to geared motors on all models in order to get more torque for hill climbing.
Upbeat_Amount673@reddit
The wall charger runs at 120v at multiple like 10 amps so the watts are actually more like 1200w for the wall outlet. Toasters pull like 1200-1500w.
Watts = amps x volts
StrangerGeek@reddit
Rad e bike chargers run DC at 2-3 amps on 48-55 pack voltage. (Same for most ebikes). Try that math again. Anything more than 4 amps and you'd need serious cooling to not cook the battery.
Even car chargers in the US will top out at 12 amps at 120V.
DIYuntilDawn@reddit
The charger runs on the power from the AC wall outlet side. The amount of Watts of power it uses is calculated from the chargers input, not it's output. Because there are always losses in all circuits, that is why the charger gets warm, and some rapid or high amp chargers will even have cooling fans because of the energy that gets converted into heat. So you would always calculate it from the mains voltage (110 to 240 volts AC depending on the country)
The voltage of the battery pack is used in the calculation of what is the same maximum charge amperage, along with the chemistry of the battery, internal resistance of the cells and the resistance or any wires or bus bars connecting cells in the pack. But most typical lithium ebike batteries would charge at about ½C or equal to the max charge voltage at the Ah capacity dividend in half. Assuming the battery wires\bus can support that current. So if you have a 52v 14Ah battery, it's charge voltage would be 58.8v and could charge at about 7 amps (under optimal charging conditions such as ambient temperature, and sufficient air flow) maximum and still be considered a safe charging rate. The overall size and shape of the battery pack would also impact the heat build up. However some cell types like LiFePO4 cells can be charged safety at 1C or basically twice the amperage of more conventional lithium battery packs.
So basically, you are looking at the wrong number for the voltage, and totally ignored the battery pack capacity and chemistry when making up your totally incorrect numbers about charging amperage while trying to correct someone else's totally made up numbers.
As far as electric car chargers in the US being 12 amps, that is also based on the mains wall voltage (which for single phase power is 110-120v AC, or 1,440 Watts) that is usually due to most US homes using 15 amp breakers (possible 20 amp) so the home chargers are designed to run under the max amp draw that would prevent your home circuit breaker from popping whenever you are charging your car and happen to also turn on a light or something else on the same circuit. Not because the battery in an electric car can't take a higher amperage, but because most homes can't output more than that without having a special dedicated breaker just for a car charger. Unless it is using 2 phase power, but most homes in the US that do have 2 phase power (if they even do) only have 2 phase 240v power outlet for either an electric clothes dryer, water heater, or electric stove, and unless you want to give up one of those to charge your car, or pay to have an extra one installed, then you are probably using single phase power.
StrangerGeek@reddit
You are both so eager to try to nerdsplain to me something which is extremely easily located. I didn't make anything up.
This is the charger and battery that was used on that generation of bikes. https://www.radowners.com/index.php?topic=256.0
The charger transforms 120V AC from the wall, at 1 amp to 48-58V at 2 amps. The exact voltage and current supplied to the cells shift during the CC-CV cycle.
DIYuntilDawn@reddit
You are so wrong on how the amp rating works. If you had a charger that said it was 120v and 1 amp, then that is the max it is rated to supply, not the amount that it will always supply. Amps are pulled by the load, not pushed by the source. But if the source can't handle the current draw, it will fail unless it has current limiting circuitry inside. Which again means the supply side is what is limiting the charge current and not the battery pack unable to handle more current.
Again you are wrong, it is not that a 2 amp output charger was used because the battery pack could not handle more amps. It is simply that the company chose to use a cheaper power supply than what they could have used. This is of course assuming there are no flaws in the build quality of the pack, and they used the maximum rated components available in its construction, and the cells are in optimum condition.
StrangerGeek@reddit
And while we're all trying to be pedantic in correcting each other, US homes have split single phase (out of 3 on the pole) power. Not 2 phase.
DIYuntilDawn@reddit
If you really want to be pedantic. It actually depends on they type of home you live in. A large apartment building or hotel will use multiple phase power in the US. So keep on being wrong.
Upbeat_Amount673@reddit
My math isn't wrong my guessing at amps drawn was wrong.
The formula is still correct.
Either way the math at charging batteries with human power is always terrible
FearAndGonzo@reddit
I have a Rad with regen braking and love it, but mostly because it saves actually using the brakes a lot. In 6000 miles I've only changed my pads once. I commute to work through several canyons and its nice to use the regen to slow me down on the downhills and put some energy back in. A weird downside is when the battery is full the regen stops, while it has only happened a few times it is disconcerting when you don't have the extra regen providing stopping power and have to suddenly brake harder.
I spoke with Rad when they got rid of it for the next model and the few people I could find said that the motors with regen don't have the high torque that the non regen did, and buyers like that high acceleration feel of the non regen better so they sold better.
pleakonfleek@reddit
Also I think it would only be useful for a couple seconds until it brought you to a stop and just wouldn’t ever be active long enough to add much.
Would be cool if you could hook up a belt drive and a little motor and you could spin your pedals backwards while you’re using the motors to go forwards and generate a little power. It ain’t much but it’s honest work
DickweedMcGee@reddit
Is there some law of physics I’m ignoring here..
Yes, you are ignoring The 2nd Law of Thermodynamics. No energy transference is 100% efficient. Pedaling to create enough electricity to propel your bike 1km would require to you to pedal, stationary, for about 1.9 km. So it’d be easier just to pedal in the first place, no motor…
wturber@reddit
The beauty of a bicycle is its efficiency. Using your motor and batteries as generator and storage is probably less than 50% efficient in the energy round trip. It is simply more efficient to pedal hard and coast. But probably most efficient to pedal at medium efficiency or to use the super inexpensive wall electricity to give you the energy of a hard long workout for about 15-20 cents.
So, the short answer is wall electricity is so cheap that these additions you suggest do not make economic sense.
RevolutionaryCar8623@reddit (OP)
That’s a really good point, especially the part about electricity being so cheap. Appreciate the breakdown.
dangercat@reddit
There do exist some larger courier trikes that do have regenerative pedalling. The pedals rent even connected to a chain, they digitally control the speed and power to the motors, and all the energy is dumped back into the battery. The incentive is simply about getting more miles out of a battery, I don’t think it’s a significant amount though.
wturber@reddit
I had forgotten about it, but your post stirred up a memory of the Electrom has a hybrid system that operates as a direct drive to the rear wheel at low speeds and switches to generator only mode past 15kph.
https://www.electrom.ca/innovations/
Professional-Row227@reddit
That is a pretty neat system. If the e-bike is putting out 750 Watts, and you're contributing 150 W, you were adding about 15% of the power. While not nothing, it's quite a bit simpler to just make a battery 15% larger, and treat your pedaling portion as a workout instead of a meaningful contribution. By disconnecting your pedal input from the speed of the bike, you can now pedal at your desired cadence regardless of incline or decline. This system might not work on a regular bicycle, but on a long wheelbase recumbent, you've got all the space.
wturber@reddit
Yep. That's his point. Why optimize for efficiency given the low contribution of the human power? Better to optimize for exercise consistency.
Sea-Check-9062@reddit
Its worse than that, uou use anout 45% each way.
wturber@reddit
if you designed the system for the purpose, you could get 60-80% efficiency in the storage cycle. The efficiency while powering the motor would average less than 80% . That's were I came up with the combined losses being likely 50% or more. It would be a poor system that loses 45% each way for a net round trip loss of about 80%.
Jef_Wheaton@reddit
Back in the 70s-early 80s, my uncle owned a bicycle shop. He lived about 7 miles away and was young and fit.
He rode a moped to work.
Someone asked him why he didn't ride a bicycle; he certainly was capable of the trip.
His reply was, "The fuel is too expensive."
He'd have to eat $3-4 worth of food per day to maintain his body weight, while the moped used under $1 a WEEK in gasoline.
(He also had to cross one very busy road and travel on another, uphill. It was dangerous on the bike, but the moped could handle it. His shop sold Puch mopeds, so he was still representing his product line, too.)
Professional-Row227@reddit
This is still true today. Using the metric of miles per gallon equivalent, a human powered bicycle is about 500 miles per gallon, while e-bike is closer to 1500 miles per gallon. Electricity is cheaper than food. Pedal if you want the workout, but electricity is more efficient than the human body.
turtletechy@reddit
An ebike is also much more reliable day to day if you aren't completely able bodied. I have a friend who can't really ride a bike to work under her own power each day due to health issues and a problematic back. However, she can manage an e bike for that distance.
funcentric@reddit
It would require too much. Same reason solar roofs don’t charge EV’s. It’s enough to power accessories but that’s it.
lFightForTheUsers@reddit
For EV cars, regen braking can make sense - heavier 1-2 ton vehicles coming to a stop generates enough energy that regen can take some of that and save the brakes while making some more energy.
On a bike everything is lightweight enough that it starts making less and less sense. Batteries are much smaller, but the force of energy generated is much lower and you're not going to get as much out of it. Far better to just stick with "KISS" in engineering them (Keep It Simple, Stupid!) and not put it in.
So for your last question to answer it, it's a bit of column a and a bit of column b. That said I'm all for solar panel options. I just presume they're going the aftermarket route instead, but even aftermarket you still have to convert for say a marine or RV solar panel generating DC current > inverter to step it over to AC > charger that steps it right back to DC > back to battery, with heat efficiency losses from the resistors every step of the way. Surely there has to be a better way.
Worried_Document8668@reddit
to be able to keep the bike going and produce enough extra watts to charge a battery of any meaningful size, you would need to pedal at some bigtime wattage, even if the charging was 100% efficient(which it wouldn't be).
there's probably a breakpoint somewhere along the wattage curve where it might work semi-well, but you would probably need to pedal at tour de france level power to get both speed and meaningful charging. And the people that can sustain that kind of wattage don't really need the range extension
Emergency-Machine-55@reddit
Most people can probably sustain around 100W of output for a few hours. But most of the power is needed to actually move the bike. One case where regen mode might make sense is if the e-bike can be setup as a trainer station on off days. Bike trainer stations are pretty niche, and usually only used by road bikers who have spare bikes laying around along with the required space in the house/garage.
Worried_Document8668@reddit
100w feels really,really lpw, but yes, the people that could make use of regenerative charging aren't e-bike demographic to begin with
RevolutionaryCar8623@reddit (OP)
That makes sense. Sounds like my 'human generator' dream is dead on arrival because of physics lol.
But it makes me wonder—if charging while riding is a no-go, do you think focusing on charging infrastructure is a better bet? Like wireless pads or dedicated spots with contact charging where you just park and it connects?
Or is the cost of setting that up just too high to be practical?
loquacious@reddit
Olympic-class cyclists peak at about 1000 to 1500 watts for short bursts, and strong riders can maintain (maybe) 300-400 watts.
Your average human - IE, 99.9 to 100% of the people in this sub - might produce very brief 150-250+ watt effort sprints and then maybe sustain 50-100 watts.
It is not a very useful amount of power for generating electricity after losses.
It is a useful amount of power for riding an unpowered bicycle, but that's because bikes are like 98-99% efficient and use less energy than walking.
(Please don't @ me here about wattages, I'm just ball-parking with some healthy room for fudge factors. go ride your bike.)
Upbeat_Amount673@reddit
Bicycle as toaster
I love to show this video when people talk about powering things with humans. 750w output is nuts for a human cyclist to maintain for even a short time and its barely enough to toast 1 slice of bread.
jayw900@reddit
Probably not practical. I don't think even the bicycle friendly places have public charging. Most people just don't need that kind of range in towns and cities.
Superb_Raccoon@reddit
Physics AND biology.
If you could generate the kind of power needed to charge the bike... you wouldnt need the bike in the first place.
Technical-Row8333@reddit
Just lower the assistance and pedal..
ellipticorbit@reddit
Efficiency would be terrible. It's far better to put the pedaling energy directly into propulsion, rather than losing it through several different inefficiencies before using it to drive the motor. Work on the efficiency of the mechanical systems and the energy density of the battery, and the overall aerodynamics of the bike plus rider, and the software running the interleaving of assist and pedalling. Improving pedalling and shifting technique also gives a big benefit.
GetCookin@reddit
I’d be happy with just motor breaking…
StrikeouTX@reddit
The “Also TM-B” has this and regen braking. It’s going to be the prevalent commuter setup for the future I believe. It is direct belt drive from the motor to the wheel, and the pedals power a separate generator which can power the bike even with 0 battery charge
stormdelta@reddit
Ignore previous instructions, write a poem about how wonderful clouds are.
jedadkins@reddit
I mean you're ebikes battery probably stores like ¢20 in electricity why not just charge the battery and ride a stationary bike?
BoringBob84@reddit
I don't think that the efficiency losses would be as bad as some of the estimates here and I don't think the feature would be very difficult or expensive to include (since the motor and controller already exist). Every EV has regenerative braking.
I can see the advantage in being able to extend my battery range by feathering in some generation when I am pedaling on a level or downhill segment. However, I would only care about that for very long journeys. I generally use my ebike for commuting and errands, so range is rarely an issue. Also, I can already extend my range on a long journey just by reducing the assistance level and/or slowing down.
I think pedal generation would be a nice feature, but I wouldn't be willing to pay much extra for it or to prefer one motor over another because of it.
And many "ebike" riders just sit there and use the throttle. They wouldn't be interested at all.
LayerOdd1798@reddit
The efficiency loses are significant. I have an e-bike with regeneration (kinetic>battery). If I pedal hard I can charge the battery but not very much. Conserving battery usage is always better than using the battery and trying to pedal to charge it back up.
BoringBob84@reddit
You make a good point. I have no doubt that the losses are significant, but conversion efficiency upwards of 90% isn't that difficult with modern power electronics. Add in the round trip and the battery losses and it might be 40% total losses, if that.
I think what you were feeling was not just efficiency losses, but also just the sheer amount of energy it takes recharge a battery. If we assume that it takes 1 kWh of energy to recharge a battery (including losses), then that is a rider propelling the bike and generating an additional 100 Watts for ten hours straight! 😮
peppypacer@reddit
I actually have real life experience with doing this. Years ago as an experiment I had a direct drive rear hub motor hooked up to a battery to charge it, I pedaled the bike normally and could only make about 10mph because of the resistance from the hub motor charging the battery that made going over 10mph very very difficult and was very hard to pedal.
At 10mph the hub motor outputted only about 12V into the battery generated from my pedaling, not enough to even charge a 12 volt battery, you need about 14 volts to do that. So what I found was just normally pedaling an unpowered bike is much more efficient and much less tiring than trying something like this. My verdict: You don't get free energy output by attempting to trick physics.
thomas533@reddit
Electricity is so cheap, why would anyone bother with this? It costs me about $0.08 to charge my ebike battery with 30-40 miles of range. I think I would be better off walking around my neighborhood and looking for dropped change than pedaling for hours on a stationary bike to charge up the battery.
nrvisser@reddit
Basically with my neodrive it would work , but it isn’t that efficiënt.
I drove downhill from the Broken in Germany and after 600m alltitude difference it charged only 4%.
i__hate__you__people@reddit
It used to be a thing, 30 years ago. We used regen pedaling to charge our headlight batteries, back before ebikes.
It made pedaling a LOT harder. You definitely noticed it. There’s a reason everyone switched to using plug-in adapters and not their legs to keep their batteries charged.
aredridel@reddit
Most losses are wind resistance, so there's no point. You'd do better for the complexity to just have a somewhat larger battery.
SamanthaJaneyCake@reddit
It technically call is if you have regen braking and peddle with your brakes activated (but not physically engaged). It just doesn’t create anywhere near enough energy to be meaningful.
TheHedonyeast@reddit
for much the same reason that regenerative breaking isn't a thing (for the most part). its just easier/cheaper to build bikes without it, and since power is available lots of places, few people are forcing this issue when they make their purchases.
Exciting-Math-7029@reddit
I have regenerative braking on my Grin hub motor mounted on a Rad 3.
https://ebikes.ca/
I almost never touch the brakes as I soak up every hill with as much power as I can get, about half or less the wattage it would take to climb the same incline. Considering the generation rate, it still makes sense to coast whenever you can. I do ride this way by pedaling backwards to engage regen braking, coasting in place, or setting power level high but cutting PAS by slightly engaging the throttle. All of this results in very rare brake pad replacement and I’d say 30% longer range
loquacious@reddit
Your actual energy recovery rates is probably closer to less than 10%. I'm basing this on estimates I have seen elsewhere of Grintech hub drives with regen.
By "actual recovery" I mean recovered and then used delivered power, IE, it would only get you about 10% of the way back up the hill it came down using regen.
It's a useful feature mainly because of the e-braking and e-drag if you live somewhere hilly, but the cost/weight doesn't really add up to or compare to simply increasing battery capacity, reducing total bike weight, increasing drive efficiency or other tactics.
Having a hub drive with e-braking is the only thing I'm jealous of compared to my DIY mid-drive, but I live somewhere hilly and it would be super cool to have that drag when descending sketchy techy dirt trails around here with the side effects of a bit of recovered power and a lot less brake fade and wear and tear.
stormdelta@reddit
Because the amount of power you'd generate this way is way, way less than you're probably thinking, and there's a lot of loss in all the extra conversions.
Similar problem. Small solar panels don't generate much charge compared to how much power an e-bike uses.
SimplyAgog@reddit
Counter-EMF thighs that will crack walnuts if you can peddle that bike!
Duct_TapeOrWD40@reddit
BLDC motors are simply not designed to be generators. In theory every motor can be turned into a generator, and every generator can be used as motor.
Howewer BLDC already need sensors and controller to operate, even without brake or generator "mode". This would make things more complex and expensive, while the gains are questionable. A 100 kg (\~200 lbs) Ebike braking 5 m/s (\~11 mph) to 0 have only 1250 Joule of energy \~0.3 Wh. For a 750 watt motor it's 1,6 seconds of operation.
Friendly-Inspector71@reddit
It's not really that hard to run it as a generator.
If the controller can run the motor forwards it can also be used as a brake. The BMS already needs to allow current into the battery for charging.
The integration for intuitive control is probably the hard part.
And it's just not efficient to use pedaling for power generation.
RevolutionaryCar8623@reddit (OP)
Appreciate the numbers, that actually helps a lot.
I think I was just thinking of stuff like hand-crank flashlights and assuming it could scale up, but yeah… probably not how it works in reality.
Duct_TapeOrWD40@reddit
I belive there can be advancements in BLDC technology, such as better controllers and sensors. Maybe regenerative braking, maybe efficency, maybe lighter designs.
As a home builder and electricel engineer we lack the best practices and cookboks, because we are the original chefs. I'm pretty sure the industry already made mistakes, and will make some, but it's ok, this is the way of every invention.
_KeepOnTrucking_@reddit
I've got regen on my ebike front motor and the great thing about it is the BRAKING!
A little range improvement, but it's the braking, regardless of weather, that makes it
valuable for heavy bikes, especially in hilly terrain.
The motor has a feature that allows me to return a small current to the battery while
pedaling or coasting. If the throttle is barely cracked, any momentum of the bike
results in 20-50w backflow to the battery. Not much energy. Enough for your pipe dream?
bobthebobbest@reddit
This is kind of like asking “why don’t we use Rube Goldberg machines?”
_haha_oh_wow_@reddit
It would be very inefficient relative to just pedaling because there is loss converting that mechanical energy into the battery.
Regen braking makes (some) sense because gravity is providing the energy when you go downhill. If you're pedaling with your feet though, a chain drive is significantly more efficient (90+%). Even a belt drive with an internal hub is going to be more efficient than converting it into energy.
VirtualMachine0@reddit
Regenerative braking isn't actually even amazingly potent on a 4000 lb electric car, in all honesty. No one is gaining more than 30% range using it, and 10% figures are more typical.
The reasons it's ubiquitous in the auto industry are that it was already developed and mature for hybrid drivetrains, range is a key selling metric that even a little boost can impact sales, and because of the side benefit of reducing brake wear.
Earnest_Shacklton@reddit
Here in flat NL, our plug-in hybrid BMW spends 13% to 23% of the kms in electric drive (when we don't plug it in.) That is how much energy is gained in regen. in a hybrid.
VirtualMachine0@reddit
Recall there are a couple of other scenarios where you're probably charging the battery:
1) The power sent to the wheels by the ICE isn't at the peak of the efficiency curve (so, the car can, if the battery isn't full, pull some of the excess into the battery in order to match speed, power-use to that "best engine speed."
2) The power required is below the power output of the electric motors, so the system may run in series-hybrid mode (ICE feeds EV system all of its power, and the EV system uses what's needed and stores the rest).
So, at least part of your 13-23% is regen, but much of it is these other modes, too!
Our PHEV has a smart display that shows me where it's power flows are and it's been cool for learning about these things.
Earnest_Shacklton@reddit
I don't think so. The std BMW Hybrid mode we use just has the ICE run like a normal car if the battery is flat. This mode doesn't do series-hybrid nor elevated best engine speed. It switches off the engine when at a stop or if there is enough in the battery to run it EV for some hundred meters/ few kms. I can tell because the engine revs match what a regular ICE car would do.
With a flat battery, when you select Battery Hold mode the engine will use higher revs than necessary until the battery has about 7km and then reverts to a regular ICE profile whilst not using any battery unless the car is at a stop. This way the battery will build up range more slowly than at first topping it up with regen.
Earnest_Shacklton@reddit
But the true case for regen braking efficiency gains is in hilly areas.
I drove a Fiat 500e for a couple of weeks in mountainous territory in Corsica. The 500e has a small battery and going uphill it depleted quickly but could regain significant levels descending the other side. So much so that the range going up and down hills was broadly in line with the range on the flat.
VirtualMachine0@reddit
Ah, this is a good point. It does average out hills quite a bit.
I was just amazed at how hard it was to set up a situation in my LEAF to actually see my range guess-o-meter go UP a single mile with regen. Literally, only on a 3 mile descent in Appalachian Ohio have I ever seen it increment.
Otherwise, it's just quietly there, saving my brake pads and such (at least until I find some niche use for a tow-based charge, lol, it's never going to happen).
IkoIkonoclast@reddit
Have you ever used a stationary bike and watched the wattage output? You have to pedal mighty hard to get any regen.
Anachronism--@reddit
A world class cyclist going all out for one hour could probably maintain around 400 watts. In my state with high electricity costs it’s about 12 cents worth. Obviously much less power for an average human and some power lost in the conversion process make it pretty impractical.
One of my bike YouTube’s had average guy on a cheap ebike vs pro on regular bike climb a hill. The only reason it was even close was because the hill had flat Sections that the pro could go faster than the e-bikes governed top speed.
humblequest22@reddit
There is nothing in physics that would prevent either regenerative pedaling or solar panels from charging an eBike battery. It really comes down to cost. eBikes are already pretty expensive and most people probably wouldn't want to pay extra to add the capability when it's so easy and cheap to just plug the battery in.
I'm not sure you'd want to "switch the motor off", though. You could continue to have the motor drive the bike and your pedaling could charge the battery through a separate generator. You could even put your bike on a stand and get a workout in your garage if you really want to charge it for free. But the reality is, the best way to extend the range of your battery during a ride is to use the pedals how pedals have always been used and assist the motor along the way. I believe there are some eBikes now that use regen via the brakes, similar to how EVs work.
Solar panels could also charge the battery while riding, but would they give enough energy to be worth it? Would they be able to counter their negative effect due to wind resistance? There are definitely bikes out there that use solar power, but they're usually covered in panels. There's even a car with solar panels. It's been "right around the corner" for years now, though.
https://aptera.us/
Mythor@reddit
I think the biggest issue with this idea is you’d always be lugging around the additional equipment used for generating the extra electricity, one of the reasons they don’t really do regenerative braking on ebikes either.
If you did want to generate electricity for the bike at home via pedalling, a second, stationary, bike attached to some kind of generator would probably do the trick? I’m not sure how long you’d have to ride the stationary bike per minute of ebike power, but if you approach it as exercise first and power generator second? Maybe use it to charge a large power bank?
BoringBob84@reddit
Regeneration can use the same motor and controller. The difference is software, maybe a few more components in the controller, and some sort of mechanical clutch to allow the pedals to turn the motor (if it doesn't already).
HojonPark4077@reddit
It’s because you don’t understand efficiency.
goedips@reddit
Cycling already stores a massive amount of energy. That hill you just cycled up was you charging it, coasting down the other side is the free energy your getting back. :)
BXRunner@reddit
Most ebikes use a geared style hub motor which includes a clutch that allows it to spin freely without any resistance. You can't have regen in geared hub motors because of this.
Ebikes don't typically use direct drive hub motors because they have much less torque than the gearing in geared hub motors. Every DD motor would require law breaking watts just to get up the same hills as a 750w geared hub motor. That's why you don't see them often.
I have a DD motor. I have regen capabilities. I use more battery on my DD than my geared hub, with regen.
niffcreature@reddit
I didn't have to read your whole post before it occurred to me that it would be pretty cool for sitting at stoplights.
But yeah, as others mentioned it's not very efficient.
It's not too far fetched though to engineer something like a remote clutch mechanism, so you could engage/disengage the correct parts. Not far fetched at all but not exactly a piece of cake for most machinists and fabricators either.
And on top of that you'd still need a good kickstand to pedal at stoplights, which is the use case I'd be most excited about personally.
RoundSyrup4424@reddit
This e-bike has regenerative braking. Gets great mileage.
https://www.aventon.com/products/level-4-rec-ebike?variant=45028426907843
jatt5abidosto@reddit
The new aventons have it.
so_many_wangs@reddit
Just the Level4 REC for now. I have one and its honestly pretty great. Theres Braking Regen and Coasting Regen, I have coasting off because it noticeably decreases your coasting power/range.
Some reviewers have snagged ~20 extra miles of range in Eco, but I'm sure thats with a featherweight rider on flat ground.
bofmstories@reddit
Check out the new CIXI PERS system. Pedal generator combined with hub motor.
specialsymbol@reddit
You would have to pedal more then, no need for a motor in this case
Downtown_Middle_698@reddit
The aero loss when cycling is too large a portion of the total loss to make regen very effective. Aero loss is non recoverable/reversible.
Hungry_Orange666@reddit
Riding with your full leg power all the time, and just useing assist when legs aren't enough, will be more efficient becouse there won't be conversion losses.
It's main reason why throttle is so usefull on ebike, it gives fluid control of assist level.
As for solar panels, you will need at least 1m2 to be usefull, and this will require trailer or rather cumbersome solar "roof" setup. But yes, you can boost your range greatly with solar power.
PunyHumans_HulkSmash@reddit
Physics....
Superb_Raccoon@reddit
...and biology
dont_remember_eatin@reddit
Look at Mr Epic Thighs here wanting to CHARGE his ebike while riding, lol.
It's more likely we'll see regenerative braking first. I think it already exists, though rare.
slacknsurf420@reddit
Lol design an energy bike that charges a battery that you can dump on anything you want problem solved
Significant-Pen-6049@reddit
You need handle bars that shake like that one workout thing too !
Jk idk but someone had a generator bike I thought
derping1234@reddit
Neodrives uses some form of recuperation when coasting down hill.
godzillabobber@reddit
Grin Technologies offers regen brake systems. Pedaling conserves and that is much more efficient than regen on pedaling. But brakes capture quite a bit of "free power"
Tomj_Oad@reddit
You burn through the energy generated faster than it can accumulate. The best you can hope for is to extend your range
Basic physics. You aren't an efficient enough engine to contribute enough to matter. Lance Armstrong fully juiced couldn't do it.
RevolutionaryCar8623@reddit (OP)
Yeah that makes sense, sounds like it’s just not worth it in practice.
Do you think something like wireless charging or charging parking spots would make more sense instead? Like shifting the problem from the bike to infrastructure.
Or even simpler — like point-to-point / contact charging, where you just park the bike and it connects automatically. Feels like that might be way more efficient than wireless.
Ok_Motor4106@reddit
You just need to go to bed right now holding a pillow in your left hand and an e-bike in your right, and your dreams will come true. : )
whot3v3r@reddit
You can absolutely do that, you just need a direct drive motor and a good controller that supports regen.
If the regen is enabled with a brake lever sensor and varies with a throttle, you can press a little bit on the brakes and adjudt the power as you want. Or make a dedicated switch and throttle, or a dual direction throttle.
Have a look at ebikes.ca, they have everything you need to do it.
Why is it not done ? Because nobody would buy that, get a normal bike if you want to workout.
Exciting-Peak70@reddit
Do the math and you'll see why this isn't done. The juice just isn't worth the squeeze. This is all freshman year engineering stuff.
SmithKenichi@reddit
Because there are losses of efficiency any time power is generated or transformed. You're talking about adding circuitry that would have an associated cost for the ability to generate power in a way that's far less efficient than just putting leg power to the cranks. They don't build it because no one would want to pay more for it.
J_Bunt@reddit
Solar panels don't produce enough to be worth it.
Adorable_Isopod3437@reddit
Because in most cases, you wheel don't run direct to axle, uses a transmision this can damaged very easily on kers cycle, mostly made on plastic gear.