Mass market regen
Posted by NickelSmartPoundFool@reddit | ebikes | View on Reddit | 44 comments
iFor a long time, it seems we’ve come to accept that regen on a bike is not practical. The reasons range from:
- “bikes aren’t heavy like cars so not enough energy is generated,” which is pretty nonsensical at face value. On high speed downhills, bikes are much less aerodynamic so it makes sense to smooth out the ride by charging the battery instead of losing it to wind resistance
- direct drive motors don’t have enough torque, which is a reasonable enough claim since my understanding is that a direct drive motor generally sacrifices torque for top speed.
however, there are multiple e-bikes coming out now that have regen braking with a variety of techniques. The aventon level 4 simply runs a 750W motor at 36V and has incredible torque. The segway muxi offers regen at 48V with 20” wheels. the t-mb offers regen but a horribly inefficient drivetrain that makes it dead in the water imo
Is there anyone left on this sub that’s interested in e-bikes beyond class2/class3/emoto distinctions that can explain this sudden shift in the market? Any early adopters of these ebikes that can explain their tradeoffs, or any regen capable bikes that I’ve missed?
Pixelplanet5@reddit
this is not how it works though, you are either going a high speed downhill and lose a ton of energy to wind resistance or you go slow downhill and have a little bit of regeneration and still have wind resistance.
in order for wind resistance to be not relevant you would basically need to ride down the hill at walking speed which would require high gearing towards the motor to get enough RPM to regenerate anything and would also add inefficiencies.
NickelSmartPoundFool@reddit (OP)
Yes, air resistance always exists unless you’re in a vacuum, but my point still is relevant since it’s proportional to the square of speed lol
DoggoNamedDisgrace@reddit
I admittedly have really low experience with e-bices, but even my 4ah bosch charging thing takes a good few hours to recharge my battery.
I guess those few minutes of recharging while breaking or going downhill wouldn't noticeably improve your range, and would introduce more complexity and weight. All gains would cancel out.
I'm sure the engineers at Bosch, Yamaha and DJI researched this and seemingly all have abandoned this as a dead end.
iSellNuds4RedditGold@reddit
bcj is leaking once again
DoggoNamedDisgrace@reddit
The term "bice" will probably never cease to be funny to me. That and æro. Too hilariously pretentious.
iSellNuds4RedditGold@reddit
How are you supposed to KOM the b̷r̵v̷t̵a̶l̵ ̴g̵r̴æ̷v̵e̶l̵ if your bice isn't æro enough tho?
VegaGT-VZ@reddit
Upsides dont outweigh the downsides. What are the upsides? More efficiency? E-bikes can already do 50+ miles per kWh. They are like 10-20x more efficient than cars. And cars generate orders of magnitude more kinetic energy per lb of vehicle from their higher speeds, so they can get way more back from regen. Braking from 40 MPH vs 20 MPH yields 4x more energy. More braking power? Bigger rotors & more aggressive pads do the same way more simply.
And how would they go about adding it? I have an EV. I hate driving it in OPD mode. On a bike it would be even worse as you'd need to constantly pedal to not slow down, which kind of defeats the purpose of an e bike. If it's just linked to the brakes, you will need new brake levers with electronics to initiate regen, and some kind of programming to dial in the appropriate amount for the conditions, which would significantly hamper the amount of regen you get. It's a lot of complexity for very small/marginal benefit. Basically a solution in search of a problem.
stormdelta@reddit
The point of regen and direct drive in general is lower maintenance and reliability, not efficiency.
I would argue all ebikes should already have sensors on the brake levers as a safety feature to force motor cutoff when braking. Variable regen though is ideal and does require some additional logic or system, but not that much more, you just need either a variable sensor on the brake levers, or link it to some other control, e.g. on Grin's CAv3 it inverts the throttle.
Nobody would build an ebike with regen on by default, that'd be silly. There is the added drag inherent to all direct drive motors, but that's separate from regen. On nicer setups with better controllers even that can be offset with virtual freewheeling.
VegaGT-VZ@reddit
This all comes back to my original point though. The gains are so marginal that even a small additional cost for an optimal control sequence might not be worth it.
stormdelta@reddit
It's more about what someone's priorities are.
For me, minimal maintenance and reliability are paramount as my bike is my primary transportation, especially as I also have executive dysfunction issues.
It's not just about cost, it was about simplicity and ease of ownership, plus regen functions separately from the normal brakes which helps in conditions that weaken brakes like a broken/stretched cable, brake fade from heat or icy conditions, or damaged hydraulics. And most of the prereqs for regen are things I already wanted such as direct drive motor and sensors in brake levers.
NickelSmartPoundFool@reddit (OP)
Regen braking is implemented in every single EV except pedal bikes. Lots of solutions for the non existent problem it seems.
Saying bikes are slow is the exact same as saying they’re not heavy. It is irrelevant. The issue is that PEVs have an extremely poor CdA/kg of a bike vs a car, so every other PEV on earth has regen
VegaGT-VZ@reddit
EVs and hybrids already have the hardware and programming in place to utilize and optimize regen, bikes don't.
It's actually extremely relevant. The poor CdA/kg of PEVs means a lot of the deceleration cars get from regen is already eaten up by drag. And that's on top of the already high efficiency & low available kinetic energy to harvest.
Why should it get push back? I think everyone besides you realizes this is not worth pursuing. Can you even quantify how much more efficient this would make the average e-bike? And with e-bikes costing less than $0.01/mile to operate, is there really huge demand for more efficiency, especially if it comes with more cost/complexity? I think you have latched onto this tech as a rallying cry w/o actually determining if or why anyone else wants it.
NickelSmartPoundFool@reddit (OP)
Hybrids and cars of course have regen, but so do scooters, so do surrons, mopeds, one wheels, and electric unicycles. The only reason the American consumer fights regen for some reason is because they are misinformed in the same way they were told the Prius was a car for gey men. They want more torque and have ended up with a MORE complex system with MORE cost because geared hub motors and brake pads wear out much faster.
NickelSmartPoundFool@reddit (OP)
Hybrids and cars of course have regen, but so do scooters, so do surrons, mopeds, one wheels, and electric unicycles. The only reason the American consumer fights regen for some reason is because they are misinformed in the same way they were told the Prius was for homosexuals. They want more torque and have ended up with a MORE complex system with MORE cost because geared hub motors and brake pads wear out much faster.
DWolvin@reddit
Counterpoint, Wife and I have a pair of electrics and I helped her learn OPD, and we have not had to ever replace brakepads on a heavy SUV. I do agree it's going to be difficult to get it working on a bike because you freewheel often while coasting, but engineering may come up with something elegant that surprises (probably linked brakes on one lever, E brake on the other.
VegaGT-VZ@reddit
EVs use regen regardless of whether or not you use OPD so they're gonna save brake pads no matter what.
And for me personally, I need to see the cost/benefit analysis in raw numbers to see if it's actually worth it. Global average electric rate is $0.17/kWh. Average e-bike is 50mi/kWh. So we are talking $0.003/mile or nearly 300 miles per dollar of electricity. Is another 30-50 miles per dollar worth an extra $50/bike? I don't think so. I feel like e-bikes need to be cheaper + more reliable, not more efficient & expensive. This is deep into the territory of marginal gains/diminishing returns IMO.
DWolvin@reddit
Fair enough, I just spend enough time on long downhills that I'd love it on my ebike. But I agree cheap and simple is good. I have a torque sensor and would have rather not even had a throttle (Have is physically blocked).
NickelSmartPoundFool@reddit (OP)
Wow you have some strong opinions! Can you think of any other implementations besides 0 or 100% regen based on pedaling or not? Because as far as I know, what you’re describing doesn’t even exist
Hopeful-Driver-3945@reddit
I have a Stromer ST3 bike with regen. The regen itself is practically useless to save energy. However it does save my brake pads a lot of wear. About 80% of braking on my way to work is regen.
redpillsrule@reddit
After having Regen I am a believer, my brake pads might last 50,000 miles.
NickelSmartPoundFool@reddit (OP)
Self built? Do you suffer from poor torque on uphills?
redpillsrule@reddit
Diy mid drive and direct drive hub combined, climbs most hills at 30 mph.
Iddra_@reddit
How many miles does that bike have?
redpillsrule@reddit
6000
StrikeouTX@reddit
Your front hub is missing out. Need a motor there too!
DWolvin@reddit
Now that's a Frankenbike! Nice!
FuzzyBucks@reddit
Sounds like it makes sense in some cases.
Cargo ebikes would be a good fit since they're heavy and already trade speed for torque
NickelSmartPoundFool@reddit (OP)
What extra cost/complexity does a direct drive bike entail? There are a few benefits beyond range like reduced brake pad wear, more powerful and quieter braking that i would consider solved problems
Gold_Area5109@reddit
There really isn't much extra complexity or cost.
Eskates use regen as brakes, they just don't add much back to the battery. It's basically assumed to be 0 and having a 60-80 lbs bike vs a 10-20 lbs board doesn't do much to change that.
So there isn't alot of point to add regen - it's inexpensive to add and how to add it to an ESC is a solved since eskates and other PEVs do it at much the same voltages.
Most braking is accomplished by your front wheel due to a persons natural weight transfer forward (onto the front wheel) while braking. While having a rear hub motor does counter act this to some extent you are still the heaviest part of your bike.
So why isn't it on ebikes? Pennies saved is pennies earned as you would still need a front brake, unless you drastically change braking styles and are fine with an increased braking distance and that's not even taking into account emergency stops.
On an eskate an increased braking distance is preferred as a sudden stop can literally kill you... Look up "Evolve Boards and accident" if you want to know more.
FuzzyBucks@reddit
I think in many cases, range is already good enough with battery though so maybe it just doesn't make sense to add more cost/complexity of it isn't really solving a problem
stormdelta@reddit
Can't speak to mass market, but I love having variable regen on my DIY setup.
Massive reduction in brake maintenance + adds redundant braking that isn't subject to brake fade
Regen braking is very smooth and fun to use
It doesn't return much energy in normal riding, but on round-trip hilly commutes it can actually help to offset the lower efficiency of a direct drive motor. I get around 5-7% return in city riding, but upwards of 20% for hilly routes
LastNightOsiris@reddit
I don't know the answers but I'm interested in this concept as it's something I have wondered about as well.
One concern would be whether this system would require constant pedaling in order to avoid slowing down, or if it could be switched on/off to only activate on downhills, for example.
And then of course there is tradeoff in terms of both cost and weight. If it adds a couple hundred dollars to the bike cost this may be ok for higher end models but prohibitive for budget bikes. And if it adds 5-10 pounds of weight, that's significant and may be the difference between being able to lift the bike easily or not.
I think the major advantage would be less wear and tear on brakes and pads, with the energy savings being nice but of marginal value except maybe on very long rides.
BarkleEngine@reddit
If you lived in the mountains, it would make sense. But really in that case, the best thing would a dedicated front regenerative braking hub, and a mid drive for propulsion. I don't know that a braking hub even exists, or any control/BMS which handles dynamic charging.
Informal_Arachnid_84@reddit
Forgive my ignorance, but how does regenerative braking work in relation to electrical/electronic components? I assume any EMF produced while braking has to come back to the controller using the same phase wires, (looking at the way they're connected to the board) back through the same MOSFET(s). MOSFET(s) that are specifically designed to prevent reverse voltage. Then what? High-side MOSFET(s) blown? Hopefully just a blown shunt. That's assuming the motor (acting as generator) can produce sufficient power to charge the battery. Surely it would need to be rectified? I've never seen a rectifier on a motor controller. Do controller require additional circuitry to actually use regenerative rather than just electronic braking and dumping any reverse EMF as heat?
DWolvin@reddit
(I'm not an electrical engineer) Really basically regen is just using the motor temporarily as a generator. Yes, there are efficiency losses but it's a way of reducing speed using the electrical system instead of mechanical friction. But as I type that I think you are just worried about the surge back into the controller and I'd just say that it's the same circuits that handle launch torque. They can handle it.
NickelSmartPoundFool@reddit (OP)
This is a bit out of my wheelhouse, but I know it is discussed here by the godfather of ebike regen https://endless-sphere.com/sphere/threads/analysis-of-regen-on-an-ebike.7891/
chrispark70@reddit
Some Israeli guy invented a brake rotor modulated regen system that I think works with any hub motor. Some company bought the idea and I think they may be making them. It is a very good system and allows you to perfectly modulate regen based on how hard you are braking.
But, bikes aren't cars. I don't use my brakes nearly as often as I use brakes in a car. I roll through stop signs and I coast slowly to red lights in the hope it turns green before I have to dismount. My bike has a very small battery at 252wh. Even with such a small battery, I don't regen would do much of anything to increase range even though I use my bike exclusively in a city.
NickelSmartPoundFool@reddit (OP)
And he is no longer partnered with grin, only receiving press from his fellow countryman on electrek. I suspect we will never see freegen in reality, but am interested to hear more about why the grin has gone silent on it
chrispark70@reddit
I haven't heard about any updates in quite a while. Makes you wonder why it has gone nowhere.
_KeepOnTrucking_@reddit
Added a front direct-drive w/regen kit to an existing ebike with geared hub in rear.
AWD is amazing in itself, but the regen braking is a literal life saver on the steep hills
around here.
The geared hub is frisky on the hills (with the assistance of the front direct-drive).
The two drives play extremely well with each other, despite completely independent controls.
Controllers and drives run cooler sharing the load, a big plus for hilly terrain.
redpillsrule@reddit
I don't think the Aventon has Regen and my 250 watt hyper mid -drive does 85 nm of torque so 100 nm is nothing unusual.
NickelSmartPoundFool@reddit (OP)
This new model claims to have it. It’s far from transparent about how they’ve achieved this though, and I suspect the power draw is only something like ~200W based on short testing. I don’t own my own bike to actually test it properly https://www.aventon.com/products/level-4-rec-ebike
redpillsrule@reddit
It's a hub drive, thought it was a mid drive. There's a way of doing regen using the disk brake to activate it. I have only seen a video of this rigged up totally custom but thought they would eventually show up on commercially available bikes. Maybe that's what is on this.
Bobby_Strong556@reddit
The regen on my onewheel is significant. I can gain around %10 charge on a downhill trip.