Ravi Kempaiah
Well-Known Member
- Region
- Canada
- City
- Halifax
One of the most common questions that people ask when you ride an E-bike is: "Does it charge when you pedal....? " 
People are curious about this aspect of the motor and intrigues most outsiders.
Let's take a step back:
We should go back to the induction motor invented by the Great Nikola Tesla and there are several millions of these induction motors running even today.
Here is a great video explaining the workings of an induction motor.
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But, what is used in our E-bikes is a DC motor not an AC motor.
DC , brush-less and gear-less direct drive motors are one of the most widely used E-bike motors.
In simple terms:
Motor = uses electric input to produce mechanical rotational output.
Generator = motor but uses mechanical rotational input to produce electrical output (just the reverse)
Regenerative braking is essential for hybrid and electric cars and improves the fuel efficiency and reduces brake wear. On a Tesla Semi truck, you never have to change brakes/brakepads. How cool is that?
Is it really practical for an E-bike?
Why not use the extra 5% energy that is freely available and save some brake pad wear, right?
Yes and it really doesn't take much to implement simple regenerative braking. It may cost more to implement variable regen braking (Stromer, BionX, Stealth etc. motors have this feature).
Here is a fantastic thread explaining the workings of E-bike regenerative braking by Justin Lemire-Elmore of GRIN Technologies, a pioneering engineer who has been in the field and has designed some great E-bike motors and chargers.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=7891
Does it add extra complexity? NO
As he explains above, there are no differences when it comes to electrical circuitry between an e-bike with regenerative capability and those that use Direct Drive hub motor but do not have this feature.
But it does require different firmware and it doesn't add a ton of cost.
" With brushless motors, the basic circuitry behind a regen and a non-regen motor controller are identical. The power components like capacitors, mosfets, mosfet drivers and such are exactly the same, and these are the items that determine the cost of and complexity of the controller. The only thing that makes a regen controller different is the manner in which the mosfets are driven. In a non-regen motor controller, the current during the PWM off cycle typically flows through the diode of the low side mofet bridge doing PWM, while in a regen motor controller this current flows through the low side mosfet which is turned ON for the OFF portion of the PWM cycle. "
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Is it possible to regain energy from braking or regenerative braking in precise? YES
How much energy can be recouped depends on your terrain.
Justin writes in his report:
" There is also endless debate about how much you actually get back with regen, some poopooing it at just 1-2%, and other regen proponents touting the 10-20% claims. The fact is both these extremes and everything in between are true. It depends entirely on your riding environment; how hilly is your terrain and how much stop and go you have to endure. "
It can vary from 1% to 15%. Here is an example from his daily riding.
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Another myth is that it creates too much extra drag. Not really.
Yes, direct drive motors have slight extra drag for coasting. In practical usage, on an E-bike, it is really not pronounced.
From my practical experience, the efficiency of a Stromer is better than Bosch mid-drives because I tend to commute at 20-25mph speed and at those speeds, direct drive motors are very efficient.
Here is a nice article about E-bike Regenerative braking on Electricbike.com which goes into lot more specific details.
https://www.electricbike.com/regenerative-brakes/
Does it add extra weight? NO
No. Negligible weight addition and by very nature, direct drive hub motors are heavy and robust. They are capable high power/speed without stressing the drivetrain components.
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So, why did companies like Pedego and Evelo that employed direct drive motors did not use this feature?
Most of these companies do not have extensive R&D and they just get bikes made in China and use drastic cost-cutting measures. It would cost less than$10 to implement at the factory level.
As Electricbike.com noted above...
Also, Pedego has switched to geared hub motors made by DAPU and geared motors by their very nature do not have regenerative braking feature as they free wheel.
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Lots of practical examples are noted in this video. There are examples of mid-drives with regen feature.
Did you know the Zero electric motorcycles have this feature?
Majority of the premium direct drive hub motors still use regeneration. This is very handy for scooters, pedicabs, cargo bikes, which have much more momentum compared to 60lbs electric bikes.
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Bosch also makes one of the most widely used scooter motors and it is a direct drive motor as they provide long service life.
--------------------------------------------------------------------------------------------------------------------------------------------------------------
If you use a motor like GMAC, you not only get excellent low-end torque but also full regenerative braking ability.
People are curious about this aspect of the motor and intrigues most outsiders.
Let's take a step back:
We should go back to the induction motor invented by the Great Nikola Tesla and there are several millions of these induction motors running even today.
Here is a great video explaining the workings of an induction motor.
But, what is used in our E-bikes is a DC motor not an AC motor.
DC , brush-less and gear-less direct drive motors are one of the most widely used E-bike motors.
In simple terms:
Motor = uses electric input to produce mechanical rotational output.
Generator = motor but uses mechanical rotational input to produce electrical output (just the reverse)
Regenerative braking is essential for hybrid and electric cars and improves the fuel efficiency and reduces brake wear. On a Tesla Semi truck, you never have to change brakes/brakepads. How cool is that?
Is it really practical for an E-bike?
Why not use the extra 5% energy that is freely available and save some brake pad wear, right?
Yes and it really doesn't take much to implement simple regenerative braking. It may cost more to implement variable regen braking (Stromer, BionX, Stealth etc. motors have this feature).
Here is a fantastic thread explaining the workings of E-bike regenerative braking by Justin Lemire-Elmore of GRIN Technologies, a pioneering engineer who has been in the field and has designed some great E-bike motors and chargers.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=7891
Does it add extra complexity? NO
As he explains above, there are no differences when it comes to electrical circuitry between an e-bike with regenerative capability and those that use Direct Drive hub motor but do not have this feature.
But it does require different firmware and it doesn't add a ton of cost.
" With brushless motors, the basic circuitry behind a regen and a non-regen motor controller are identical. The power components like capacitors, mosfets, mosfet drivers and such are exactly the same, and these are the items that determine the cost of and complexity of the controller. The only thing that makes a regen controller different is the manner in which the mosfets are driven. In a non-regen motor controller, the current during the PWM off cycle typically flows through the diode of the low side mofet bridge doing PWM, while in a regen motor controller this current flows through the low side mosfet which is turned ON for the OFF portion of the PWM cycle. "
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Is it possible to regain energy from braking or regenerative braking in precise? YES
How much energy can be recouped depends on your terrain.
Justin writes in his report:
" There is also endless debate about how much you actually get back with regen, some poopooing it at just 1-2%, and other regen proponents touting the 10-20% claims. The fact is both these extremes and everything in between are true. It depends entirely on your riding environment; how hilly is your terrain and how much stop and go you have to endure. "
It can vary from 1% to 15%. Here is an example from his daily riding.
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Another myth is that it creates too much extra drag. Not really.
Yes, direct drive motors have slight extra drag for coasting. In practical usage, on an E-bike, it is really not pronounced.
From my practical experience, the efficiency of a Stromer is better than Bosch mid-drives because I tend to commute at 20-25mph speed and at those speeds, direct drive motors are very efficient.
Here is a nice article about E-bike Regenerative braking on Electricbike.com which goes into lot more specific details.
https://www.electricbike.com/regenerative-brakes/
Does it add extra weight? NO
No. Negligible weight addition and by very nature, direct drive hub motors are heavy and robust. They are capable high power/speed without stressing the drivetrain components.
--------------------------------------------------------------------------------------------------------------------------------------------------------------
So, why did companies like Pedego and Evelo that employed direct drive motors did not use this feature?
Most of these companies do not have extensive R&D and they just get bikes made in China and use drastic cost-cutting measures. It would cost less than$10 to implement at the factory level.
As Electricbike.com noted above...
Also, Pedego has switched to geared hub motors made by DAPU and geared motors by their very nature do not have regenerative braking feature as they free wheel.
----------------------------------------------------------------------------------------------------------------------------------------------------------------
Lots of practical examples are noted in this video. There are examples of mid-drives with regen feature.
Did you know the Zero electric motorcycles have this feature?
Majority of the premium direct drive hub motors still use regeneration. This is very handy for scooters, pedicabs, cargo bikes, which have much more momentum compared to 60lbs electric bikes.
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Bosch also makes one of the most widely used scooter motors and it is a direct drive motor as they provide long service life.
If you use a motor like GMAC, you not only get excellent low-end torque but also full regenerative braking ability.
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