Is regenerative braking really worth anything?

[Tony01]

My variable regen is my primary brake. Before it skids the tire it will bring in up to about 9500 watts peak. Get about 5% back.

 

[Balmorhea]

My variable regen is my primary brake. Before it skids the tire it will bring in up to about 9500 watts peak. Get about 5% back.

How did you title and register your motorcycle?

 

[tomjasz]

Well my errand bike is not one of the Kool Kidz ride.

My Trek Pure SA 3sp has a coaster brake and a front rim brake. Rim brake was disappointing but with the 1000W MXUS front DD the added regen braking makes the bike more capable at stopping, and panic stopping from max speed is much more reliable.

 

[ZeroEm]

by Balmorhea » Sep 16 2020 2:48pm

ZeroEm wrote: ↑Sep 16 2020 8:14am
I use regen in my leaf then the disc brakes kick in. Don't think I will ever take the disc brakes off and put shoe brakes on and quit using regen.
Coaster brakes were the big thing at one time and Caves were popular homes before houses. We must move on and embrace the future.

Coaster brakes still have some advantages, and several of my bikes have them. Total immunity to ambient conditions and more than enough power to lock the wheel, with none of the vulnerability or maintenance of a cable or hose, are good things. In another hundred years, we'll still have coaster brakes, but the fashion chasers will have abandoned hydraulic discs for something more exotic sounding.

There's nothing wrong with disc brakes. I have some and I like them fine. But they don't stop better than good rim brakes; that's not one of their advantages.

There is a market for coaster brakes, just sold a beach cruiser with coaster brakes. A lot to be admired, I have never had to work on them or have them fail, that I can remember. I love disc brakes, not so much rim brakes but most of the Bikes at my house have rim brakes but they are good enough that spending money to replace them will not happen. I don't look for regen to replace coaster, disc or pad brakes. We have not talked about regen over heating the motors yet! Regen has it's place and any motor that is capable of it I would implement it.

 

[John in CR]

...Until you get caught on a hill in the rain where you've got a vehicle with wholly inadequate braking power.

You have inventive thinking about rim brakes. Yes, like discs they require a couple of wheel rotations to squeeze out excess water when it's present, before they deliver good strong braking. But when using aluminum rims and quality pads like Kool Stop salmon compound, you still get good strong braking. Folks who have ridden decent bikes for a long time already know this.

For most people's wheel and motor combinations, regen starts out with "wholly inadequate" braking power in the best case. And until more motor manufacturers follow Grin's lead in supplying better torque arm interfaces, it's asking for show-stopping trouble anyway.

As usual you don't have a clue what you are talking about when it comes to ebikes. Stop trying to share things about which you have no first hand knowledge.

 

[JackFlorey]

How did you title and register your motorcycle?

None of us do.

 

[Steph]

I do hope so.

My daily commute involves about 100m down in the morning and well... a more tiring evening route.
My ideal scenario is actually having some supercap (probably not going to happen, it costs..) that would charge in the morning to give me the kick I need in the steepest sections of the way back. I don’t even need an assist all the way up because this cycling commute is my only physical activity and I want to hold on to it.
The way down is interrupted by some junctions that do require braking and I do feel changing my pads too often; I’m also interested in reducing the wear there.
I read a few comments here about axle nuts getting loose with regen, or torque arm being too weak... in my case, I am rather considering a friction drive with a kind of disengaging mechanism: light, minimalist and only involved in the train when relevant.

So I’m not talking from experience (yet), but I’ll put a vote on yes they do ... hopefully.

Lastly, it’s more a philosophical consideration, but I’m more interested in the pursuit of efficiency than raw power and dissipating energy into heat as braking method feels so sub-optimal...

Cheers

 

[John in CR]

I do hope so.

My daily commute involves about 100m down in the morning and well... a more tiring evening route.
My ideal scenario is actually having some supercap (probably not going to happen, it costs..) that would charge in the morning to give me the kick I need in the steepest sections of the way back. I don’t even need an assist all the way up because this cycling commute is my only physical activity and I want to hold on to it.
The way down is interrupted by some junctions that do require braking and I do feel changing my pads too often; I’m also interested in reducing the wear there.
I read a few comments here about axle nuts getting loose with regen, or torque arm being too weak... in my case, I am rather considering a friction drive with a kind of disengaging mechanism: light, minimalist and only involved in the train when relevant.

So I’m not talking from experience (yet), but I’ll put a vote on yes they do ... hopefully.

Lastly, it’s more a philosophical consideration, but I’m more interested in the pursuit of efficiency than raw power and dissipating energy into heat as braking method feels so sub-optimal...

Cheers

Steph, you won't be able to do regen with a typical friction drive, because they're set up to bite into the tire more when the motor engages with the tire, and with regen the forces are in the other direction. Since you only want electric assist for that last hill climb getting home, the best solution is probably a little geared hubmotor that freewheels the rest of the time, so your bike is just a regular pedal bike except for the last hill. That would mean a tiny battery too.

 

[ZeroEm]

Regen: when the Axle moves back and forth, that backs off the nuts. If your nuts loosen you have a problem that needs to be fixed not ignored. Most use clamping on their axle or if you are using cut out torque arms they have play. Need two torque arms adjust them as to remove the play then tighten the axle nut.

 

[Steph]

Hi John,

I’m not aiming for the self-engaging friction drive design commonly seen here. The design is smart but indeed not compatible with regen.
I’m also not aiming for the always engaged approach some members use for regen because I will mostly use the bike without assist or regen.
I saw some designs on the forum using small rc servo to engage the motor; I’ll rather go along this line, or add lever like for the fork lock.

Hub motor is not possible for me. There’s already a rohloff at the back, and the front is too likely to loose traction going uphill.

 

[Balmorhea]

Hub motor is not possible for me. There’s already a rohloff at the back, and the front is too likely to loose traction going uphill.

You should try a front drive bike before you decide that. Most of the opinions I hear against front hub motors come from folks who seem to never have used one.

 

[2old]

My first conversion was a geared 350w, 36V front conversion which was extremely enjoyable until my daughter "stole" it. Tried a 1200w, 52V DD and (for me) it wasn't fun since it seemed to overwhelm the front end and handling characteristics were affected adversely. Could have been me though.

 

[Jil]

My answer : yes it worths it.
I have GMAC, with 14S6P battery (52V), I have set up my regen to 15A (ie. 800 watts), it is now my main brake in current use. I use the hydraulic brakes only in case of emergency, or to "finish" the stop. I think it worths it becasue it is smooth and you are going to use a lot less your hydraulic/mechanical brakes. Just be careful to the set up, and the design of the battery that has to be able to whistand the charging power.

Another point : the regen does not replace the rear brake (mechanical/hydraulic) in case of emergency, for safety reasons I strongly adivse to keep both front and rear brakes.

 

[John in CR]

Wait till you guys get to try an advanced controller with variable and programmable regen. 1st regen comes on as smooth as you like...add in true torque throttle and silky smooth in both directions greatly reduces axle issue, though I always recommend wide clamping type torque arms. Let's say you want to run a 100% legal low power ebike, but that doesn't impact the current limit you set for regen. That means as long as you have good batteries and wiring you can tune braking force much higher than motor thrust at the max force position of your brake though you may rarely use it.

 

[donn]

I saw some designs on the forum using small rc servo to engage the motor; I’ll rather go along this line, or add lever like for the fork lock.

Interesting. I sometimes wonder why this isn't a feature with hub motors. The "have your cake and eat it, too" lever that you could push to turn a MAC into a GMAC and start earning regen watts.

 

[trackebike]

1. Those speeds are so ridiculous I have to wonder if you've ever ridden a bicycle. You might be able to hit 40 on less than a 10% grade, in a full tuck, but long hills that steep aren't a common feature in my "very mountainous" area, as in nonexistent. A much heavier quasi-motorcycle ride might be able to get to 50 under some relatively conceivable circumstances, but ... you're the guy who speaks for "95% of us"?
   
2. If you're so new to bicycling that you aren't sure what brakes are for, here's one example: there's an intersection at the bottom of the hill, and you will have to stop. Or, you're going to have to turn. Inspired by these examples, you may be able think of other reasons why you might use your brakes. Each one is an opportunity to recover some watts via regenerative braking.

I'm in the city, where I will have to stop every few blocks. That's most of my regen braking. I don't normally brake to bring the battery level up, I brake when I have to slow down or stop, on grades rarely over 4%, which gets me in the range of 10-12% recovery, 12-14% in CA math. I don't think it's meaningless.

I've been seriously road biking for a long time - 20 years. I don't feel that I live in a very hilly area but there are several descents that I ride regularly where I can attain over 40mph easily. I would say for the sporting aspect, that I and those I ride with seek out such hills (and we climb them). But even encountering these hills on a 30 mile ride, I still don't feel I would brake enough with the ebike to recover 5%. But I will admit these hills either descend into a flat or they go into another roller.

Such hills that end in a crossroad or stop sign do exist but they are rare. Around me they are typically the roads that lead down the side of a valley and run perpendicular into road that goes along a river. Again, I've been on some club rides where we hit several of these on the ride but I still don't see them contributing significantly to regeneration energy.

I know what brakes are for, but the whole mantra with traditional cycling is conserving energy. You are typically climbing hills and coasting on the descents and stops. Hard braking is rare. Even in a city going block to block you can see the traffic light ahead. You know naturally to coast up to the light and gently stop or apply power and make the light. You naturally avoid heavy braking. It's not like you are gunning it as you approach the light.

It is hard for me to think of a time in recent memory where I was laying on the brakes for an extended period of time (like longer than 20 seconds). I've rode around Lake Wallenpaupack in the Poconos several times and there is a descent along the back side of the lake where there is some amount of braking. That is a ride that I considered very hilly, but again, even with that big descent there was hardly any braking over the course of the whole ride, it is just a bunch of climbing up a hills and coasting down the other sides of them.

But I am now confused. I consider that I don't live in a very hilly area although I have a few >40mph descents.

You, on the other hand, state that you live in a "very mountainous" region but claim such descents are rare to non-existent. Which makes me wonder how you could ever recover 5%, let alone 10%.

 

[99t4]

trackebike, your description of your local topography is a utopia of non-braking cycling bliss. Not everyone is as fortunate. My own local area is urban steep hilly everywhere, almost always with poorly maintained broken up asphalt or concrete, and tricky obstacles or dangerous traffic patterns at short intervals. Throw in plenty of railroad tracks often running at narrow angles and unavoidable concentrated areas of heavy semi-truck freight traffic. And to top it off, 9 months of rain combined with several months of darkness.

I would love to share your 40 MPH unimpeded descents and general no-brake everyday cycling experience but must make do with a different reality. Regen braking is very useful to me. I like the idea that it helps brake pad life, and helps recharge (however minimal) the battery. Therefore, I use it whenever possible, when braking is needed (in my case often).

 

[trackebike]

trackebike, your description of your local topography is a utopia of non-braking cycling bliss. Not everyone is as fortunate.

I don't think so. I think it is more about riding style/technique. You're going to have to explain to me these long descents you make where you are able to re-coup significant energy. I can't see any significant energy being re-cooped in block to block riding in the city either, unless you are an idiot and are gunning it as you approach the stop lights.

I'll tell you a little more about myself. I live in Montgomery County, PA. About 15-20 miles north of Philadelphia. However, I mostly ride in Bucks county and into New Jersey, crossing the Delaware River at Washington's crossing or New Hope (or other places further north on the river). But I have ridden in other places, Poconos, South Carolina etc.. I am a very seasoned rider involved with a local bicycle club. I am a club ride leader for a weekly ride.

I do not commute on my road bike or my e-bike (although this could change in the future). However, lately, I have been riding my e-bike to the local post office three times a week. This is a 4 mile round trip. Two to three times a week I do 20-35 mile rides on my carbon road bike.

I am reluctant to take my e-bike on a club ride for fear of scorn from the other riders. In fact, the subject of how to accommodate e-bike riders on group rides is in much dispute within our bike club (as I am sure it is in many other traditional bike clubs).

This Tuesday I was planning to take my e-bike out as a demonstrator on my group ride. We are close to end of the season so it seems like a good time to do it. I was just going to tell the riders that for this ride, I would lead from behind, but I would do little blips hear and there to show them what the bike was capable of.

It is pretty crazy, I believe because most traditional cyclist are misinformed. I was speaking to one senior club member and he felt that e-bike riders can do group rides so long as they used pedal assist only and not use the thumb/twist throttle. To me this just didn't make any sense. I disabled the pedal assist on my e-bike because I thought it was wasteful! I know better than the controller when I need a boost. The utility of pedal assist is the subject of another thread. I think it is useless even if it is torque sensing.

I think totally different, I think e-bikes are great, especially for those who are elderly or otherwise challenged by other issues such as weight, or bad knees, etc.. The mean age of our bike club is increasing (in fact I find that somehow my age is increasing!). I don't care what it takes to get someone out on a club ride. But I think e-bike riders need to stay towards the back of the group. It is very discouraging for a normal bike rider who is "going all in" physically to be surpassed by an e-bike rider. I am sure there are those who find disagreement to this, but I have heard enough complaints from conventional riders that I feel this is the best approach in the near term. This is a subject best discussed in another thread, in fact. it is the subject of a bike club newsletter article that I intend to write!

Anyway, my point is distilled down to this. Heavy braking and long sessions of braking are very rare in cycling, not just for me but for most people.

Poster ZeroEm points out in a earlier post in this thread Mrbill's ride as a testament as to how effective regen can be.
Here is the Strava data on this ride https://www.strava.com/activities/3924449644

55 miles of descent? Are you kidding me? This is not typical. There are very few places in this world where you can do this. It is not even a descent that you would see in the Tour de France! Its not even a round trip ride! So, I call "No fairsies" you can't use that as a justification for regen and you are purposefully being misleading. I am correct in this assertion? Right?

I can buy that someone out there might get 5% regen. I don't believe 10% unless very extreme circumstances.

Regen is a wash for cycling. Coasting beats regen..and coasting is the norm.

 

[Balmorhea]

55 miles of descent? Are you kidding me? This is not typical. There are very few places in this world where you can do this. It is not even a descent that you would see in the Tour de France! Its not even a round trip ride! So, I call "No fairsies" you can't use that as a justification for regen and you are purposefully being misleading.

Purposeful or not, it's anomalous. Same with the Vancouver BC data from Justin Elmire. It's just not results that most of us can expect to get, ever.

 

[AHicks]

trackebike-
I don't think anyone is claiming regen (as most know it) is going to work out well for everyone. As mentioned earlier it's a big yawn for those that some might call flat landers. And then, even for those that are riding in hilly areas, regen is way more about holding your speed in check. MOST are not going to like the idea of controlling or trying to stop a bike going 35 mph down a hill. Regen is a way of holding those run away speeds in check.

With something like the GMAC, things change big time, with the unit able to replace the rear brake much of the time. These function well at MUCH lower speeds - to the point it must be controllable (variable). Just switching it on an off could be scary, potentially causing a loss of control - especially at higher speeds. The GMAC equipped bike COULD put something meaningful back into the battery during the course of a ride.

 

[E-HP]

Coasting beats regen..and coasting is the norm.

Just to be clear, just because a bike has regen doesn't mean that it can't coast. Regen is something you activate, so you can coast to your hearts content.

 

[Balmorhea]

Coasting beats regen..and coasting is the norm.

Just to be clear, just because a bike has regen doesn't mean that it can't coast. Regen is something you activate, so you can coast to your hearts content.

Most DD motors don't coast worth a damn. Proper bicycle-style coasting requires a one-way clutch.

 

[E-HP]

Coasting beats regen..and coasting is the norm.

Just to be clear, just because a bike has regen doesn't mean that it can't coast. Regen is something you activate, so you can coast to your hearts content.

Most DD motors don't coast worth a damn. Proper bicycle-style coasting requires a one-way clutch.

So the discussion shifted? I like my DD motor, but I've never tried gearless. I'll probably try mid drive before gearless though.

 

[Balmorhea]

Just to be clear, just because a bike has regen doesn't mean that it can't coast. Regen is something you activate, so you can coast to your hearts content.

Most DD motors don't coast worth a damn. Proper bicycle-style coasting requires a one-way clutch.

So the discussion shifted? I like my DD motor, but I've never tried gearless. I'll probably try mid drive before gearless though.

I'm just sayin'. Both my e-bikes have DD hubs, but they don't coast like regular bikes at all.

So until someone makes a declutching DD hub, you either get regen or a bike that coasts freely, but not both.

 

[goatman]

if you get a phaserunner and put in about 1 amp of electronic freewheeling or a about 1rpm/sec with tire elevated it coasts like a bicycle then put 1500 watts of regen into the settings with about a 400m/s torque ramp up rate, the braking is awesome with no jarring. get the right controller and regen is priceless. i like rswannabe thread

https://endless-sphere.com/forums/viewtopic.php?f=6&t=103634&p=1526300&hilit=rswannabe#p1525987