Regenerative braking on e-bikes

[JPB]

I was wondering when the manufacturers are going to start fitting regenerative brakes on e-bikes to extend the range.
On long down hill sections Im sure you would get a good amount of electric back !

 

[118]

what about those riders who hardly ever brake, and prefer to 'let the bike go and flow' ..?

 

[Rusty]

Not sure about regenerative braking as being the answer. Probably better something like a rear hub sensor/dynamo that charges when the wheel is turning but you are not peddling. Would have to be drag-free though to not disrupt momentum.

 

[Beekeeper]

I don’t think you would get much energy back to make it worth the extra weight of extra electrical components and you would be charging an already hot battery.

 

[Pdoz]

what about those riders who hardly ever brake, and prefer to 'let the bike go and flow' ..?

they get regenerative suspension. Now there's a project worthy of the mighty yamaha r+d budget.....

 

[outerlimits]

Shimano have a patent on ABS brakes and this could filter to other applications like regen brakes. Shimano Files Patent for Anti-Lock Brake System for Bikes - Pinkbike

 

[Beekeeper]

The future could be thorium-powered cars and eventually bikes. 8 grams of thorium gives you a range of 1 million miles

 

[apac]

Regen braking only works with motors without reduction gearing and without a clutch. Direct drive hub motors only with no internal moving parts. And as stated above the gains are minimal, and you'd have to be braking from a very high speed to really benefit and even then the amount of amps put back into the battery would have to be limited due to how much charging amps the cells can take. Our puny low charge and low discharge cells would be no good.

 

[MattyB]

...and because of that adding the systems required to do the regen on a mid drive would mean additional weight that would cost more energy to propel than it would ever recover. Ain’t gonna happen!

 

[Zimmerframe]

And as stated above the gains are minimal, and you'd have to be braking feoma very high speed toreally bnefit and even then the amountif amps put back into the battery would have to be limited due to how much charging amps the cells can take.

But if you have a Turbo Turbo Capacitor ....

Anyway, we've covered all this in the "KERS" thread months ago.

 

[wepn]

Direct drive hub motors only

Yes with one exception, the GMAC geared hub. It has a locked clutch which allows regen.

GMAC - Product Info

 

[Arondale]

Makes sense on class 2+ but not class 1 pedelecs / eMTBs. Agree with above comment. Hard to flow with artificial slowdown. In fact, after motor cutout on assist some ebikes don't even free spin wheels well. There should be no resistance from motors, ideally, after assist cutoff, let along regenerative braking.

 

[GrandPaBrogan]

I don’t think you would get much energy back to make it worth the extra weight of extra electrical components and you would be charging an already hot battery.

Yes and further to that, the most feasible generator able to produce a decent output would probably be a hub motor on one of the wheels (or both) functioning in reverse. You wouldn't want those activated to charge on climbs or flats because the rotational drag resistance will be drawing power from the battery it is meant to be charging.

Possibly ok for a commuter bike but the added unsprung weight (generators are heavy) is no good for suspension efficiency for an e-MTB... which is why we have mid-motors in the first place.

 

[outerlimits]

I know if you spin a motor backwards that it will generate power. How about a regen system while back peddling. It could use an electromagnetic clutch that can be switched off or on by the rider. Back pedaling could store the generated power into a capacitor that could provide a boost of power to get up the next hill. ?‍

Specialised would market this as “Super Boost” the power to go further....

 

[GrandPaBrogan]

The only non-lossy chargers I can think of are:

Solar-helmet... for sunny cloudless days

AND

Wind Turbine helmet... for winter and night riding

 

[wepn]

Possibly ok for a commuter bike

I’d say possibly my favourite feature on a commuter bike. So many advantages. I’ll try to keep it brief:
1. A third brake - but really it is the primary brake used to rapidly reduce speed on flat road but probably more importantly a constant downhill coasting deceleration rate.
2. No fade additional brake redundancy - you can stop very quickly using all 3 brakes
3. Massive increase in brake pad longevity
4. Depending on weight, gradients etc, otherwise wasted kinetic energy yields anywhere from zero to 10% or more additional range.

 

[The Flying Dutchman]

Given how little electrical energy can be taken in by the battery at any time and the relatively short amount of time spent on the brakes, a recover system looks unlikely to provide enough juice to even be close to being worth it.

Even a system that creates a charge whilst coasting is going to equal resistance. Anyone remember those bike lights will know what how much steam that sap out of the ride.

 

[wepn]

a system that creates a charge whilst coasting is going to equal resistance

Yes that is the purpose of regen, you freewheel until you push the regen button under your thumb when you want to slow down going downhill.

One major advantage that kinetic energy is captured when desired as opposed to be being lost, mostly as heat through the rotors & callipers which in turn reduces braking capacity.

For off-road bikes, there are obvious & major downsides in comparing direct drive hubs to mid-drives that don't have regen. For a commuter bike with a geared hub and regen it's nothing like what has been described here, in fact a grand total of zero downsides. The only real downside of a locked clutch i.e.no freewheeling has been overcome by Grin Tech by implementing an electronic freewheel feature that will overcome rolling drag and still comes out ahead when compared to an actual freewheel.

I've done many hundreds of thousand of kilometres on commuter bikes with regen and no downsides for me.

It makes even more more sense for heavier riders or cargo carriers on steep & hilly roads.

 

[GrandPaBrogan]

Yes that is the purpose of regen, you freewheel until you push the regen button under your thumb when you want to slow down going downhill.

For Enduro or DH eMTB, that switch could probably be activated by the brake levers - either by a small mechanical connection, or perhaps even better by a pressure switch incorporated into the hydraulic line.

 

[wepn]

For Enduro or DH eMTB, that switch could probably be activated by the brake levers - either by a small mechanical connection, or perhaps even better by a pressure switch incorporated into the hydraulic line.

I have an off-road monster that has regen but it's not as useful or helpful off-road. That would be different if it was progressive or adjustable but it is linear operated by the thumb button.

 

[apac]

I have an off-road monster that has regen but it's not as useful or helpful off-road. That would be different if it was progressive or adjustable but it is linear operated by the thumb button.

You would also want variable refen

For Enduro or DH eMTB, that switch could probably be activated by the brake levers - either by a small mechanical connection, or perhaps even better by a pressure switch incorporated into the hydraulic line.

I have set up variable regen on my off-road diy ebike. I use a tiny magnet glued to the underside of the brake lever and then a hall sensor placed near it. As the magnet passes by the sensor the 5v signal changes strength.... Exactly like the hall sensor in an ebike throttle. It works amazingly well and i can stop from 60mph without too much help from analgue brakes. I can set it to different strengths and even different types of reactions from the motor. Such as motor braking or even motor reversing. I see peak amp returns of around 35amps for a split second.
Regen also can cause motor heat issues.

Btw, the gmac collaboration using the old mac motor looks awesome. Justin from GrinTech is a clever cookie.

 

[Shifty]

I’m going to gaffer tape a solar panel to my helmet and attach a small wind turbine to the front of the bike like a propeller! I’m sure that will help! ... seriously though, range isn’t an issue for me. 500 battery on the Giant is good for 70k.. rode all day at Ashton Court Bristol and still had 2 bars left.

 

[wepn]

You would also want variable

Yes that’s a great setup. I’m considering replacing the controller & Mac motor in my Stealth P-7 with the GMac and Phaserunner. The virtual freewheel looks really interesting.

 

[Zimmerframe]

Excellent .. @Shifty has brought some crazyness to the table !

This was my solution last time this was discussed after it became clear an efficient re-gen wouldn't really work on an MTB with current configurations :

On my bike I've attached a second hand formula 1 Kers flywheel system. It only weighs 24kg's and fits nicely in the frame. At the start of a downhill run I attach a hook to a tree which is connected to a 200m titanium cable which is wound round the kers flywheel. As I descend, the cable unwinds and spins up the flywheel. After about 200 meters the flywheel is normally upto it's maximum 64,000 rpm. When I reach the bottom I engage a mechanism which uses this energy, through a small gearbox, to drive the chain and take me almost back upto the top rather than using the battery. Once the flywheel is upto speed it acts like a massive gyroscope. I'm not sure if you ever played with a gyroscope, but once they're spinning they don't like to move. So this has the positive effect that it's completely impossible to knock the bike over (you can actually get off and it just stays upright, which is great for photos, no need for a stick), but it also has the negative effect that it's impossible to change direction so I can only take the straight "Strava" lines down a run.

 

[apac]

Having regen would add no weight. It’s electronic.

 

[wepn]

Excellent .. @Shifty has brought some crazyness to the table !

This was my solution last time this was discussed after it became clear an efficient re-gen wouldn't really work on an MTB with current configurations :

On my bike I've attached a second hand formula 1 Kers flywheel system. It only weighs 24kg's and bits nicely in the frame. At the start of a downhill run I attach a hook to a tree which is connected to a 200m titanium cable which is wound round the kers flywheel. As I descend, the cable unwinds and spins up the flywheel. After about 200 meters the flywheel is normally upto it's maximum 64,000 rpm. When I reach the bottom I engage a mechanism which uses this energy, through a small gearbox, to drive the chain and take me almost back upto the top rather than using the battery. Once the flywheel is upto speed it acts like a massive gyroscope. I'm not sure if you ever played with a gyroscope, but once they're spinning they don't like to move. So this has the positive effect that it's completely impossible to knock the bike over (you can actually get off and it just stays upright, which is great for photos, no need for a stick), but it also has the negative effect that it's impossible to change direction so I can only take the straight "Strava" lines down a run.

I'm imagining a giant gimbal. I hope it looks something like this.

 

[Beekeeper]

The article below explains why regen on a pedelec is not practical because such modes of transport are lighter and slower and therefore don’t waste so much kinetic energy. They even suggest that in most cases you would lose energy rather than save it.

(Scroll down to the ebike section)

How do regenerative brakes work?

 

[Zimmerframe]

Having regen would add no weight. It’s electronic.

If you had a suitable hub motored bike, then yes. Though there might be some additional changes/parts to make it efficient like a capacitor .

It would be such a great thing to have on a bike if you could make it work effectively.

Either with a "third brake" or more ideally working in conjunction with your existing levers.

With a mid mount motor though you'd either need to scrap the rear freewheel or have an electronic clutch there and then obviously do something similar at the motor end.

You've obviously already done and thought about most of this so I'm not bringing anything useful to the table..... I'm just sitting here with torrential rain rage on a day off ....

 

[Zimmerframe]

I'm imagining a giant gimbal. I hope it looks something like this.

I'm trying to decide if that's a 512bb in the reflection on the gif ...

 

[wepn]

It's not the energy saved or range regained that's the main advantage on a bike for me. It's the considerable extra braking power...far fewer brake pads is pretty good as well.