Regenerative pedalling.

[123Taff]

I have a Carrera Crossfuse pedal assist bike which I use to supplement my attempts to maintain a reasonable level of "retirement" fitness. I sometimes ride an old colliery railway track up a local valley. It is a very steep climb, climbing some 1200 feet over 10 miles. This means that traveling back down is a fast unassisted run at around 20 mph, which got me thinking. Cannot pedalling at that rate be turned into a recharging power for the battery whilst not being used to pedal assist. Surely, all pedalling without assistance has the potential to recharge the battery, so why don't electric bike manufacturers think of and develop this aspect. It would save a lot of home charging and contribute to less carbon use?

 

[Wicky]

Some bikes have it - my KTM P eRace hub does - it's not very efficient but helps as a brake.

 

[sjpt]

There have been attempts. It is quite complex to get regeneration when wanted without drag in many situations you don't want it, and the amount of energy regained is less than you would expect. The different speeds and tradeoffs mean it is more worthwhile in cars (several of which do use it I believe). As mentioned above the breaking benefit is stronger than the saved energy benefit.

It's relatively easy on a direct drive motor; but they generate lots of drag and other inefficiencies anyway.

 

[Andy-Mat]

Many do not understand this fully, but it is simply not worth the extra possible electrical/electronic/mechanical complications it might possibly cause, (as clearly pointed out by Wicky above!) basically only providing further sources where problems can arise, until someone is willing to design and build a completely problem free e-bike.
Let me just say, I am not going to hold my breath until that day dawns!
We see enough problems here on e-bikes without regeneration......seemingly especially on e-bikes owned by people, who are for some reason, unable to do their own maintenance, faultfinding and repairs.
Think about this, as particularly on mid motor bikes (as I believe your own bike is), with regeneration, you are simply adding even more stress (possibly almost doubling it!) to the poor single drive chain, the relevant gears and sprockets also in the drive chain, making it all wear out even sooner than usual, or even possibly break sooner, miles from home.......and it wears out already soon enough on mid motor bikes, as many here can testify. Its simply physics!!
That possible extra stress is something that Hub bikes do not do to their chains, sprockets and gears, which if the truth be known, definitely wear out even slower than on a standard pushbike, as the motor takes the strain whether driving (or slowing down regeneratively on some), directly onto the wheel, not via the drive chain.
This is made even more obvious on e-bikes with a front hub motor, even for the most amateur rider amongst us all!
The drive chain on all hub bikes, which basically only transfers the muscle power of the rider to the rear wheel, therefore especially low in stress factor, particularly if he is being lazy!
I do not think that there are many of us here who wish ourselves anymore problems of any sort or complication, when riding our e-bikes.
But at the end of the day, its an individual's right to choose either way!
regards
Andy

 

[123Taff]

I appreciate that it is fraught with technical problems, but I cannot help but think that an awful lot of energy is wasted when peddling hard without the "pedal assist" in operation. Does the motor still revolve without power when peddling? This was what I thought happened, The rotating part of the motor was constantly turning whilst the bike crank was moving and being powered by the stator, in which case I thought there would be no more strain on the drive chain (and in fact less when the motor is engaged) and it was just a matter of reversing the role of the motor from that to a "generator" which surely would be just a mater of electronics and wiring? I realise that it might be a tad more expensive in the short term, but surely, this the way that development should go?

 

[vfr400]

To get regen, you can't have a freewheel clutch in the motor. With a clutch, the motor doesn’t turn when you pedal without power, so it offers no resistance. Without a clutch, the motor always turns, so there is some resistance due to the magnets cogging.

Anecdotally, most people who had regen, didn’t like the extra resistance. Of course it's no problem if you never pedal without power.

Also, there’s nothing better than the feeling you get, when, after climing a steep hill, you get the freedom of gliding down the other side. With regen, it's like you have your brakes on when going down-hill.

 

[Artstu]

The most asked question I get asked, Does it charge as you pedal? To which I answer yes I have a dynamo in the front wheel that recharges the battery as I go so I never run out of electric.

 

[vfr400]

The most asked question I get asked, Does it charge as you pedal? To which I answer yes I have a dynamo in the front wheel that recharges the battery as I go so I never run out of electric.

What a brilliant idea. Never run out of battery again.

I was thinking about a similar idea, where I'd have a shaft running along the crossbar held by two bearings. I'd put a small propeller on the front and a big one on the rear. I'd use the motor to get up to speed, which would cause the front propeller to turn in the wind. That would drive the bigger propeller behind me to provide enough thrust to push me along. The faster I go, the more thrust I'd get. At some point, I wouldn't need to use the hub-motor anymore.

 

[Woosh]

What a brilliant idea. Never run out of battery again.

I was thinking about a similar idea, where I'd have a shaft running along the crossbar held by two bearings. I'd put a small propeller on the front and a big one on the rear. I'd use the motor to get up to speed, which would cause the front propeller to turn in the wind. That would drive the bigger propeller behind me to provide enough thrust to push me along. The faster I go, the more thrust I'd get. At some point, I wouldn't need to use the hub-motor anymore.

that may work. A popup omni-directional wind turbine for your bike to charge your battery while you are not riding?

 

[mike killay]

 

[vfr400]

that may work. A popup omni-directional wind turbine for your bike to charge your battery while you are not riding?

There was a guy that put webs across his spokes so that the wheel would work like a windmill so that he could generate in the wind when he stopped.

Then there's this:

 

[Wicky]

I appreciate that it is fraught with technical problems, but I cannot help but think that an awful lot of energy is wasted when peddling hard without the "pedal assist" in operation. Does the motor still revolve without power when peddling? This was what I thought happened, The rotating part of the motor was constantly turning whilst the bike crank was moving and being powered by the stator, in which case I thought there would be no more strain on the drive chain (and in fact less when the motor is engaged) and it was just a matter of reversing the role of the motor from that to a "generator" which surely would be just a mater of electronics and wiring? I realise that it might be a tad more expensive in the short term, but surely, this the way that development should go?

Again buy a second-hand KTM eRace P (now sadly discontinued) and try its regen function - it's not as wonderful or efficient apart from certain circumtances as you seem to want to believe.

KTM eRace P 29 - Review

In all honesty, really we are fans of E-MTBs with centre-motors. With their low and central centre of gravity, they can be ridden on demanding trails as easily as their motor-free siblings. However, rear hub drives do have certain advantages. They work directly via the rear wheel, so have great...

ebike-mtb.com

" The somewhat clumsily-named recuperation function offers a type of engine braking which is very pleasant on long descents. So overall, there really are good arguments for a rear-hub-driven E-MTB, which is why we decided to take a closer look at the KTM eRace P 29."

"As soon as you even slightly pull the brake levers, the drive is immediately interrupted and the cut-off delay is gone. At the same time, part of the braking energy is automatically used to charge the battery."