Regen Braking for e-bikes ?

Mike's E-Bikes

Well-Known Member
A nice little video from Evelo, putting in layman's terms why it is simply not practical.

https://www.evelo.com/blog/why-dont-more-bikes-use-regenerative-braking/?utm_source=klaviyo&utm_medium=email&utm_campaign=newsletter

(when you have a 5000 lb vehicle, and all sorts of space to work with, the physics of it can make sense on hybrid vehicles. I have it on my Toyota HighLander Hybrid. On 50 lb ebikes, not so much.)

Thanks Evelo. I get asked this question by new to the ebike world customers, more frequently than I ever imagined.
 

Trail Cruiser

Well-Known Member
Now to put more fuel into the fire of confusion, a new geared hub motor loses it's free wheel advantage in favor of a clutchless (more durable) design for regenerative braking and with advanced programmable steady state when coasting (simulating a freewheel).

https://electrek.co/2019/07/10/grin-tech-unveils-gmac-clutchless-geared-hub-motor/

Here's also a video on the tunable freewheel (virtual electronic freewheeling) of the GMAC.

 
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J.R.

Well-Known Member
I remember several years ago reading an article about a simulated test where a guy recharged an ebike battery (something around 8.8 amp hour). It took the equivalent of 200 miles at 15 mph, non stop. I'm sure technology has moved on a bit since then. I'll never forget those conclusions though. Some people seem to like the braking effect though.
 

Trail Cruiser

Well-Known Member
GMAC's argument focuses on longevity of the brakes and safer stopping especially when going downhills on cargo ebikes. Of course, who wouldn't want a free battery recharge while doing all those things?
 

Feliz

Well-Known Member
My BionX powered Elby has regen and I don't remember ever turning it on. Nice feature if you only ride downhill.
 

Trail Cruiser

Well-Known Member
Good to know, it can also be set on the display can't it?
I don't know if Elby has carried over the Bionx's manual regen mode function but I'm pretty sure that the regen is intergrated with the brake lever.

Edit/addendum;

Elby also has manual regen setting. Check the 13:00 min mark of the video below.

 
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AHicks

Well-Known Member
From what little I've managed to learn about the GMAC, it's not just regen they're talking about, it's variable regen. acting as an aux brake. You can control how much braking/regen. at any given time and literally stop your bike with it. This vs. the regen I know, available with some direct drive hubs. That's something you can feel holding your speed in check on a long hill, but nothing you would dream of being able to use to stop for a stop sign. The difference I'm sure is due to the fact that the MAC's 5:1 gear reduction has the armature spinning 5 times as fast as the typical direct drive. They're putting that extra rpm to work, harnessing it as braking power.

But to the point, typical "regen" is not something a flat lander is going to be paying much attention to. In an area with long rolling hills though, it's pretty handy, helping to hold your speed in check. I doubt most of us could measure what it's putting back into the battery though!
 

harryS

Well-Known Member
Full time regen on a geared motor? Might be good for a bike used as a tomato cart, or maybe a pedicab in San Francisco or any town with big hills. Good for the working rider, but not for someone out riding for exercise/fun. Gotta fly down those hills.
 

Timpo

Well-Known Member
lol so regen is NOT worth it at all. It's a gimmick.
5% increment? That's nothing.

If you have a 14ah battery, now you have equivalent of 14.7ah because regen can charge 0.7ah.

For the added cost, weight and mechanical complexity of regen, might as well just get a higher capacity battery.
It will cheaper, lighter and more simple.
 

AHicks

Well-Known Member
Though I start getting nervous around 25mph, I'm all for a nice sprint. BUT some hills are just too much when coming down them while free wheeling, especially the ones with stop signs at the bottom.....

Higher capacity battery can't slow/stop you or help control speed. I wouldn't call regen a gimmick at all - unless you are strictly thinking about the charge it's putting back into the battery. Selling that as a feature IS a gimmick!
 

Captain Slow

Active Member
With my Juiced I am replacing brake pads far more than any other bike I have ever owned. I think it's primarily because of the motor my average speed is higher and the bike weighs far more than my other bikes. I only get about 1,500 km's out of a set of front brake pads and about 4,000 km's out of a set of rear brake pads. The only reason I'm not replacing brake pads constantly is that I'm riding my road bike more often than the Juiced during the summer months.

If I had the GMAC type regen on my Juiced I think it would be appreciated for the reduction in brake pad wear more than the regen it provides to the battery. It's a neat thought, but that alone wouldn't get me to buy the kit.

What I like about that motor the most is the round drop outs and integrated torque arm. I hate having to deal with the flattened sides of the axle and getting it to sit properly back into the frame after I've taken the wheel off.

To me that's the reason the GMAC motor is attractive and the regen feature is something secondary and the reduced brake wear is a bigger factor than the additional battery charging.

I did have a Bionx system before and I recall experimenting with the regen. One time on the way home I put it in level 1 regen while I rode flat ground. I remember being surprised at how much charge I got back. But I probably was expecting virtually nothing and I got something.
 

Timpo

Well-Known Member
Though I start getting nervous around 25mph, I'm all for a nice sprint. BUT some hills are just too much when coming down them while free wheeling, especially the ones with stop signs at the bottom.....

Higher capacity battery can't slow/stop you or help control speed. I wouldn't call regen a gimmick at all - unless you are strictly thinking about the charge it's putting back into the battery. Selling that as a feature IS a gimmick!
What do you mean? Isn't that what brakes are for?
 

Timpo

Well-Known Member
With my Juiced I am replacing brake pads far more than any other bike I have ever owned. I think it's primarily because of the motor my average speed is higher and the bike weighs far more than my other bikes. I only get about 1,500 km's out of a set of front brake pads and about 4,000 km's out of a set of rear brake pads. The only reason I'm not replacing brake pads constantly is that I'm riding my road bike more often than the Juiced during the summer months.

If I had the GMAC type regen on my Juiced I think it would be appreciated for the reduction in brake pad wear more than the regen it provides to the battery. It's a neat thought, but that alone wouldn't get me to buy the kit.

What I like about that motor the most is the round drop outs and integrated torque arm. I hate having to deal with the flattened sides of the axle and getting it to sit properly back into the frame after I've taken the wheel off.

To me that's the reason the GMAC motor is attractive and the regen feature is something secondary and the reduced brake wear is a bigger factor than the additional battery charging.

I did have a Bionx system before and I recall experimenting with the regen. One time on the way home I put it in level 1 regen while I rode flat ground. I remember being surprised at how much charge I got back. But I probably was expecting virtually nothing and I got something.
Yeah I replace my brake pads about the same frequency, that's why I bought them in bulk from AliExpress.
https://www.aliexpress.com/item/32999981754.html?spm=a2g0o.productlist.0.0.6982dcd39DIhyh&algo_pvid=fdc3c352-43dd-4a01-b970-5463354edd7c&algo_expid=fdc3c352-43dd-4a01-b970-5463354edd7c-5&btsid=94307d30-53b8-41fd-89d8-ca8ec94780a2&ws_ab_test=searchweb0_0,searchweb201602_2,searchweb201603_52

Also if primary benefit of regen is to conserve brake pads, I don't think it's worth the added cost.
In addition, regen can conserve rear brake only, which has a lot less effect anyways.
 

Captain Slow

Active Member
Wow, those brake pads are cheap. I'll have to consider that when I run out. I am using the sintered ones right now and I've been paying about $10 to $15 a set. They do last longer, but not that much longer.

I think the point of the GMAC motor is that the braking is so strong that you could brake primarily with the rear and not use the front much so I think it does save wear on the front brake quite significantly. Of course it 's not as safe to brake primarily with the rear so you still need to use the front, but I would think it's less.
 

AHicks

Well-Known Member
What do you mean? Isn't that what brakes are for?
Have a truck driver explain to you the reason he uses his engine to slow his vehicle, or to control his speed going through down hill sections of the mountains - using the rear wheels only.

Obviously bikes are much smaller and lighter, but the reasons to justify regen, or the GMAC, are very similar.

If you don't think it's worth the time/trouble/money, that's your opinion, but it doesn't change the fact other might not agree with you. The developer of the GMAC for instance, obviously doesn't agree with you. Betting the concept would make more sense to you if you lived in an area where you could use something like this more frequently.
 

Timpo

Well-Known Member
Have a truck driver explain to you the reason he uses his engine to slow his vehicle, or to control his speed going through down hill sections of the mountains - using the rear wheels only.

Obviously bikes are much smaller and lighter, but the reasons to justify regen, or the GMAC, are very similar.

If you don't think it's worth the time/trouble/money, that's your opinion, but it doesn't change the fact other might not agree with you. The developer of the GMAC for instance, obviously doesn't agree with you. Betting the concept would make more sense to you if you lived in an area where you could use something like this more frequently.
Okay I ride motorcycles, obviously I do downshift for really long downhill.

The reason why some people say engine braking is better is because so that you don't cause heat fade, which happened frequently with drum brakes back in 1970s or 80s.

However, I have never felt like engine brake was needed on my ebike. And yes I do go down lengthy downhill all the time.

I can just lightly hold the brakes and coast slow if I need to, adding engine brake? Well no thanks, especially for added price and weight.
 

Timpo

Well-Known Member
Wow, those brake pads are cheap. I'll have to consider that when I run out. I am using the sintered ones right now and I've been paying about $10 to $15 a set. They do last longer, but not that much longer.

I think the point of the GMAC motor is that the braking is so strong that you could brake primarily with the rear and not use the front much so I think it does save wear on the front brake quite significantly. Of course it 's not as safe to brake primarily with the rear so you still need to use the front, but I would think it's less.
Yeah those brake bads are a lot more expensive if you buy them at store individually. Usually about 3 to 4 times more.

Honestly, I don't think you would save front pads by adding regen. The majority of braking power comes from front anyways. Adding more braking power to the rear to save the front pads? I dont think that would work, although somebody might prove me wrong.