Is regenerative braking really worth anything?

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trackebike   1 mW

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Is regenerative braking really worth anything?

Post by trackebike » Sep 13 2020 1:03pm

I'm having trouble seeing any advantage to regenerative braking on an ebike.

As a seasoned cyclist, I hardly ever apply braking for any extended period of time. It seems to me that you would have to live in a very hilly area for regen braking to have any effect and even then it would be marginal.

Also, I'm excluding the "very heavy ebike" cases, trikes and cargo ebikes, etc.. They might see some benefit.
But I think for most normal e-bikes it is meaningless.

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Re: Is regenerative braking really worth anything?

Post by Tommm » Sep 13 2020 1:46pm

trackebike wrote:
Sep 13 2020 1:03pm
I'm having trouble seeing any advantage to regenerative braking on an ebike.

As a seasoned cyclist, I hardly ever apply braking for any extended period of time. It seems to me that you would have to live in a very hilly area for regen braking to have any effect and even then it would be marginal.

Also, I'm excluding the "very heavy ebike" cases, trikes and cargo ebikes, etc.. They might see some benefit.
But I think for most normal e-bikes it is meaningless.
Basically

Pros:
3% or so power recouped from braking (yes, that little)
Almost never need to change brake rotors pads ($2 a pad $8 a rotor)

Cons:
Both forwards and backward torque on dropouts

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spinningmagnets   100 GW

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Re: Is regenerative braking really worth anything?

Post by spinningmagnets » Sep 13 2020 1:50pm

If you live where your commute takes you across a big and long downhill, regen will make your brake pads last much longer, and also it will keep the pads cool so that if you ever need them, they are not in an overheated condition where they would fail just when you need them most.

As far as how many watts you will harvest, I think it is not worth the trouble.

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Re: Is regenerative braking really worth anything?

Post by 999zip999 » Sep 13 2020 2:32pm

About 8 percent. With a strong torque arm.

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Re: Is regenerative braking really worth anything?

Post by Bigwheel » Sep 13 2020 4:05pm

I use front hub motors on my drop bar bikes and find the regen feature to be only be outclassed by the cruise control feature. The red button on the left hood is a momentary switch and when I want to slow down it is the first thing I go to. I can fully utilize the front lever while holding it also for full stops. Also works well as a drag brake when I don't want to go too fast downhill and will keep me at around 30 or so nicely while modulating it. As mentioned this is great for saving on pad wear.
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John in CR   100 GW

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Re: Is regenerative braking really worth anything?

Post by John in CR » Sep 13 2020 5:24pm

Also, in poor traction conditions regen braking by its nature is anti-lock brakes. Upgrade to a controller that gives you variable force regen and you'll never go back. Plus variable force regen engages as smoothly as you like so no less potential for rocking back and forth of the axle compared to the annoying full on or off regen by means of a switch.

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Re: Is regenerative braking really worth anything?

Post by John in CR » Sep 13 2020 5:27pm

Bigwheel wrote:
Sep 13 2020 4:05pm
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Bigwheel,
What's with that mounting position of your CA...doesn't that get in the way for using your drops?

Balmorhea   100 kW

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Re: Is regenerative braking really worth anything?

Post by Balmorhea » Sep 13 2020 5:45pm

John in CR wrote:
Sep 13 2020 5:24pm
Also, in poor traction conditions regen braking by its nature is anti-lock brakes. Upgrade to a controller that gives you variable force regen and you'll never go back.
A typical hub motor sized for legal operation in most of our countries, laced to a full sized wheel for best traction/ride quality/rolling resistance, likely won’t have enough braking torque to substitute for a real brake. It can only serve as a drag brake, and you have to be in pretty hilly country before a drag brake makes sense.

It should go without saying that any brake used at drag-brake force levels won’t lock up on ridable surfaces.
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trackebike   1 mW

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Re: Is regenerative braking really worth anything?

Post by trackebike » Sep 13 2020 6:18pm

Ok, so I'm hearing "drag brake" and "saves on pad wear"...and I don't believe "8%"

I was never sold on discs and I have rim brakes on all my bikes. I might change the pads on my rim brakes every 2-3 years. The road bike with carbon rims seems to eat them faster because of the special pads needed.

Granted my kitted e-bike weighs a bit more and will probably eat pads quicker, but there is no way the energy to whittle them down accounts to much of anything regarding regenerative power back into the battery.

I do about a 29 mile ride on Tuesday evenings. I'm just doing a rough calculation in my head where I stop during that ride.
I'll be generous in my calculation I'll say 40 ft stopping distance. I think there are about 20 times where I might stop during that ride. 29miles = 153120ft 20 stops * 40ft = 800ft 800/153120 = 0.00522 - That is a tiny number.

I just think folks should be aware that regen is not such a big deal.
Last edited by trackebike on Sep 13 2020 6:39pm, edited 1 time in total.

John in CR   100 GW

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Re: Is regenerative braking really worth anything?

Post by John in CR » Sep 13 2020 6:24pm

Balmorhea wrote:
Sep 13 2020 5:45pm
John in CR wrote:
Sep 13 2020 5:24pm
Also, in poor traction conditions regen braking by its nature is anti-lock brakes. Upgrade to a controller that gives you variable force regen and you'll never go back.
A typical hub motor sized for legal operation in most of our countries, laced to a full sized wheel for best traction/ride quality/rolling resistance, likely won’t have enough braking torque to substitute for a real brake. It can only serve as a drag brake, and you have to be in pretty hilly country before a drag brake makes sense.

It should go without saying that any brake used at drag-brake force levels won’t lock up on ridable surfaces.
Worry more about getting your police funded, so the police department doesn't need to put up billboard saying enter our city at your own risk, and less about making incorrect statements about ebike stuff. There's no legal limit anywhere in the world limiting how strong regen braking can be and with a quality controller and good enough batteries you could tune the controller to make far more perfectly controllable stopping torque than the legal power limit of motor torque for forward motion. Some of my ebikes are stopping an all up load of over 400lbs and other than a very low speed coming to a full stop (where the motor/controller makes some noise I don't like) or holding the bike in place at a full stop, I do all of my braking by regen other than the very rare emergency braking where I engage the fresh and cool mechanical brakes for extra braking force since I don't have regen current limits and current ramp up times turned up all the way. Even on a low power rig regen is so much more than just a drag brake useful down hills.

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Re: Is regenerative braking really worth anything?

Post by Balmorhea » Sep 13 2020 7:02pm

John in CR wrote:
Sep 13 2020 6:24pm
There's no legal limit anywhere in the world limiting how strong regen braking can be and with a quality controller and good enough batteries you could tune the controller to make far more perfectly controllable stopping torque than the legal power limit of motor torque for forward motion.
That’s not what I’m saying. What I’m saying is that a typical hub motor, controller, and battery optimized for 750W or less at 20 mph maximum (let alone 250W at 25 km/h maximum), won’t pack enough braking torque to function as a real full-power brake. If it did, you’d probably lay waste to your axle anyway. You’re applying whatever braking force you get, a little or a lot, through a 350mm lever (again, assuming a real bicycle) to a 5mm radius at the axle. It’s a bunk idea, and lots of folks have trashed equipment to show for it.

Yes, you can use too much motor, too much controller, and too much battery, and get more powerful regen braking. But then you’re paying for, and carrying around, too much motor/controller/battery for the job. In the meantime, a good strong rim brake weighs about a pound, including cable and lever, and costs about $30 including cable and lever. And you won’t tear out your hub motor cables when you use it.
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John in CR   100 GW

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Re: Is regenerative braking really worth anything?

Post by John in CR » Sep 13 2020 8:30pm

Balmorhea wrote:
Sep 13 2020 7:02pm
John in CR wrote:
Sep 13 2020 6:24pm
There's no legal limit anywhere in the world limiting how strong regen braking can be and with a quality controller and good enough batteries you could tune the controller to make far more perfectly controllable stopping torque than the legal power limit of motor torque for forward motion.
That’s not what I’m saying. What I’m saying is that a typical hub motor, controller, and battery optimized for 750W or less at 20 mph maximum (let alone 250W at 25 km/h maximum), won’t pack enough braking torque to function as a real full-power brake. If it did, you’d probably lay waste to your axle anyway. You’re applying whatever braking force you get, a little or a lot, through a 350mm lever (again, assuming a real bicycle) to a 5mm radius at the axle. It’s a bunk idea, and lots of folks have trashed equipment to show for it.

Yes, you can use too much motor, too much controller, and too much battery, and get more powerful regen braking. But then you’re paying for, and carrying around, too much motor/controller/battery for the job. In the meantime, a good strong rim brake weighs about a pound, including cable and lever, and costs about $30 including cable and lever. And you won’t tear out your hub motor cables when you use it.
Just like the OP you're stating things like they're facts that are incorrect because you've obviously never used a properly set up ebike with quality variable regen braking that you can adjust. Does the motor power tear up the axle and dropouts when properly set up? No of course not, and neither does regen.

When your rim brakes aren't working well because it's raining, do you ride in a manner where you need the same braking force as when it's dry? No, of course not. If regen worked like you two think is necessary for regen to be worthwhile, then we wouldn't even need mechanical brakes at all. Justin says regen averages about a 5% recovery, so that's like that much free battery, plus there are other benefits from regen as previously mentioned that to me make the extra capacity like just an added bonus. I'd use regen even if it didn't give me any extra range, since they dramatically reduce brake maintenance and increase safety in both good weather and bad regardless of the wheel diameter or ebike weight or power.

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Re: Is regenerative braking really worth anything?

Post by ZeroEm » Sep 13 2020 9:10pm

It's really easy not to use Regen, disable it. I get 3-5% but anyone that is trying to make watts with regen is wasting watts. It's takes more power to get speed up to recover a few watts stopping. People who like regen the most do long down hills that heat up the brakes and if you keep your speed down then you can recover a few free watts. every time I even slow down I use regen and I am not counting watts. I know if I use about 1000w+ on my trip I might get back 50w or less, don't even bother tracking it. If you use regen for all your stopping and % is high then your efficiency is poor and need to slow down. Don't try to use regen to charge your battery just grab a few free watts while stopping.
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Re: Is regenerative braking really worth anything?

Post by E-HP » Sep 13 2020 9:21pm

I love my regen. But it's obviously not for everyone, especially if you buy a kit that doesn't support it. It's nice to have after a long ascent, knowing that I'l gain a volt or two on my pack on the way down. It's also nice where you have a lot of starts and stops. Mine slows to about 4mph, which is slow enough to check the intersection for cars before hitting the throttle.

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Re: Is regenerative braking really worth anything?

Post by Balmorhea » Sep 13 2020 9:28pm

John in CR wrote:
Sep 13 2020 8:30pm
Does the motor power tear up the axle and dropouts when properly set up? No of course not, and neither does regen.
Motor power doesn't reverse over and over, and back off your axle nuts. Motor torque is limited to what your battery and controller allow (which in the case of legal e-bikes with normal wheels, would make a pretty sorry brake).
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ZeroEm   100 kW

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Re: Is regenerative braking really worth anything?

Post by ZeroEm » Sep 13 2020 9:31pm

I'm just fat and need the extra braking.
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Re: Is regenerative braking really worth anything?

Post by john61ct » Sep 13 2020 10:00pm

Yes if the main point OP wants to make, is that public perception of the range increase is greatly exaggerated.

Yes personally I think that factor is basically pointless, regen is not worth doing **for that reason**

But for myself - big guy, heavy bike, terrain with very steep and/or long hills, the extra braking capabilities are well worth the trouble.

Other people with different use cases are free to decide as they like.

And that's about all I got, to say 'bout that.

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Re: Is regenerative braking really worth anything?

Post by trackebike » Sep 13 2020 10:17pm

Right.. I would happily accept a controller or kit that had regen, but i would not dismiss one that did not have it..and I would not pay extra to get it.

The simple fact of the matter is that on a bike (or ebike) you are either applying power or you are coasting. Long sessions of braking hardly ever happens.

When I am out biking and I am approaching a stop light I start coasting well ahead of the light (or I'm trying to time the light so I don't have to stop). I coast right up to the light and then I gently tap the brakes to come to a stop.

For me, there is no braking on the downhills either, unless there are hairpin turns (like a Tour De France decent, which hardly ever happens) or there is a stop at the bottom of the hill. Hopefully my struggle on the climb is rewarded by a long and fast decent. The same goes for the ebike. I'm not going to apply power on the decent if I can hit 40mph just coasting.

Pad wear never bothered me on the normal bike and I don't believe it to be an issue on my ebike. So claiming regen braking is some great braking assist system "that keeps your normal brakes fresh" and "makes your pads last longer" is also a silly justification.

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Re: Is regenerative braking really worth anything?

Post by E-HP » Sep 13 2020 10:28pm

trackebike wrote:
Sep 13 2020 10:17pm
Pad wear never bothered me on the normal bike and I don't believe it to be an issue on my ebike. So claiming regen braking is some great braking assist system "that keeps your normal brakes fresh" and "makes your pads last longer" is also a silly justification.
I assume you mean silly for your riding style.

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Re: Is regenerative braking really worth anything?

Post by 2old » Sep 13 2020 11:12pm

Pretty obvious; there are two groups. For one, regen is a panacea, for the other an unnecessary PITA. I'm in the second; not worth having for my systems which are relatively low-powered bicycles for errands or off road. Not worried about saving a few watts or extending the life of brake pads, and need to make few emergency stops.

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Re: Is regenerative braking really worth anything?

Post by john61ct » Sep 13 2020 11:40pm

No one saying anything about a panacea, your use of that term shows bad faith.

And the question is not one of belief nor opinion, easily tested for any given scenario.

As stated, it can be a very valuable feature for those with those certain factors & use cases that make it so.

In fact as OP made clear, there are example use cases where it becomes an essential feature.

Those without a need for regen are better off leaving it out.

And of course, many people have drunk the koolaid and overestimate its benefits.

The "green" and "free energy" tropes are certainly not valid reasons IMO.

But not reason to throw the baby out with the bathwater.

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Re: Is regenerative braking really worth anything?

Post by E-HP » Sep 14 2020 12:05am

This is not usually a controversial topic, unless it's turned into one.

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Re: Is regenerative braking really worth anything?

Post by wineboyrider » Sep 14 2020 12:26am

I used regen on a front wheel cruiser bike for about a year until my wheel flew off and laid me on my ass.. LOL That was my fault for being lazy and not tightening the torque arms (there wasn't one). However, I would love to integrate it into my next build again someday down the road, because it was like having three brakes and not two..
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Re: Is regenerative braking really worth anything?

Post by John in CR » Sep 14 2020 2:01am

john61ct wrote:
Sep 13 2020 11:40pm
And of course, many people have drunk the koolaid and overestimate its benefits.
There's no koolaid. I can ride in a manner to maximize regen recovery on level urban streets where I've recovered over 20% on multiple setups (fixed regen and variable) or I can ride like usual, more relaxed and with more coasting and get 4-7% recovery depending on the route. Naysayers of regen on ebikes can only be in 2 camps:
1. They enjoy fiddling with brake maintenance and have no interest in maximum safety, efficiency, and convenience.
and/or
2. They never experienced good quality smooth engaging regen.

While I can understand some not wanting to pay extra for regen, but many of those same people have no issue paying thousands of $ or euros for unassisted pedal bicycles, which seems a bit twisted like there's a deep-seated prejudice against ebikes that they can't let go. I can also understand some who've had a bad experience with regen like jerky hard engagement that isn't comfortable and causes problems with ebikes not adequately built to withstand regen, so they don't like regen. What I can't understand though is how anyone with no experience whatsoever with good quality regen braking would go out of their way to attempt dissuade others from it's use and be so closed-minded about its potential benefits, especially the better way it works on more advanced modern controllers.

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Re: Is regenerative braking really worth anything?

Post by Hardergamer » Sep 14 2020 5:18am

According to my CA I'm getting 14-16% back from regen, but it's very steep here, next to no flat ground.

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