Analysis of regen on an ebike

[justin_le]

Any motor will have drag regen or not when powered, but here you get to a 4 X advantage by pretending that there is no drag in the regen but there is drag in the non-regen.

I'm not totally sure I follow your line of thinking here, is it possible to try rephrasing the objection? When you have a system that freewheels, then there is no motor core loss when the motor isn't being run, while a direct drive system will have motor core loss during the entire trip regardless of how much the motor is being used. My point was that the amount of energy you get back into the pack from regen is typically more than the energy you need to overcome the core losses for the entire trip. So that in principle, you can have a motor controller that powers the direct drive hub with just enough watts to to make it have zero drag, and the extra watt-hours consumed by doing this is generally less than watt-hours you recoup back into the battery via using regen whenever you come to a stop.

With the numbers from this earlier study it worked out to being twice as many watt-hours returned from regen than are needed to overcome the motor drag. So based on this, if you are comparing two systems that are otherwise identical, one of which has a freewheel (so can't do regen) and the other has no freewheel and does regen, and on average you are using the motor 50% of the time, then the energy recovered by regen in the first setup is four times higher than the energy saved by the freewheeling setup.

I wouldn't say 4X advantage, but if you are talking watt-hours, then the guy on the freewheeling bike would say "Hey, because my ebike freewheels, for the times I wasn't using the motor I was able to save 10 watt-hours of energy compared to you by having no motor drag", while the guy on the regen system doing the same trip would say "Sure, I had an extra 10 watt-hours of drag energy that I needed to put into my system because it doesn't freewheel, but I got 40 watt-hours of energy back into the pack from regen every time I stopped. So on the whole my total energy consumption (human + battery) was 30 watt-hours less than yours, take that!"

So here is how I see it. A regen bike will be ridden differently from a non-regen bike, a regen bike will be ridden like a motorcycle where you power most of the way to a red light and then release the throttle and let the engine drag bring you nearly to a stop before you brake, a non-regen bike as soon as you see the light turn red you release the throttle and coast all the way to the light. This means that the non-regen bike coasts almost always twice are far as the regen bike when approaching a red light, sometimes 3 times as far.

This point is of course totally true. There's no doubt that riding habits change when you have regen vs. when you are trying to preserve every ounce of momentum because your brakes just convert it into heat, and that would definitely play into actual Wh/km numbers. Similarly on steep downhills people with a freewheeling setup will just fly as fast as they can for the thrill of it, while those with regen will get a thrill seeing how many watts they can charge their batteries at while their speed is more tempered as a result. That means in stop and go riding, the regen system will have a faster speed on average, while in up/down hilly terrain the freewheeling rider would average a faster clip.

Thus, I believe based on the above revised analysis you have not proven which one wins. I believe the ONLY way to really get to the bottom of things is to build to nearly identical bikes one with regen the other with freewheels and run these bikes on the same path at the same time riding together in the way most efficient for either bike and see what wins.

I wasn't trying to say one system "wins" over the other, just that the oft used argument against regen enabled systems is that you waste a ton of energy overcoming motor drag and that makes them less efficient than freewheeling rigs. This is psychologically true for a lot of people, but it doesn't really stand up to energy scrutiny.

Since doing this original talk 6 years ago I've had a chance to think about it a lot and also gather a lot more empirical data too. In the original analysis I was using 0.5 N-m as the average drag torque from core losses in the motor, but more typically the larger DD motors used these days like the Crysatlyte 'H' series are about 1Nm of drag, and the results are less optimistic in this scenario with the regen just breaking even over the core losses.

As for the amount of energy recovered during riding with regen, we have 3 staff here on regen equipped ebikes and the recovery rate seems to hover pretty steady at about 0.7-1 Wh-km returned to the pack. So when we do trips that really milk regen for like a 20% regen rate, it's usually while drawing only 5Wh/km for consumption, and the net return is ~20% of 5Wh/km = 1 Wh/km. While higher power usage trips that see lower 4-5% regen rate are usually consuming on the order of 15-20 wh/km, which results in a similar 0.75-1 wh/km for recovered energy.

At that rate, the motor drag needs to put an average drag on the bike of about 3 newtons or less in order for it to be fully offset by the regen capture.

I may get a chance to do this in the next couple years, we will see.

If you do that, it would be great. There is far too little empirical data being shared in this space, and a little too much armchair analysis!

-Justin

 

[Punx0r]

My point was that the amount of energy you get back into the pack from regen is typically more than the energy you need to overcome the core losses for the entire trip.

What a great observation

 

[diggler]

Great stuff here. Helped a noob like me understand regen a hole lot better.

My new takes on regen are that variable regen (if it were possible) only makes drivability better and it wouldn't increase the amount of regen. Also there is no point in less then 6a or more than 12a of regen current, except for drivability.

I do have a noob question though. Is the torque(fine windings?) motor more efficient at making regen or the speed(course windings?) motor? Do I have the fine and course backwards? Also do you get more regen from a front and rear motor than just one?

And just a spit ball Idea here...I'm currently in the process of building a gas electric hybrid fat tire, (I know you guy's hate the gas :wink: ) and I was wondering what you thought about the idea of using regen to charge the batteries while putting along with the gas engine?

 

[amberwolf]

I do have a noob question though. Is the torque(fine windings?) motor more efficient at making regen or the speed(course windings?) motor? Do I have the fine and course backwards?

Fine or coarse windings don't make any difference to anything (speed, torque, regen, etc) other than how easy it was to wind the motor in teh first place, all other things about the motor being equal.

Also do you get more regen from a front and rear motor than just one?

If both are identical, and you use just one, you'll get half the regen you would from both, as long as teh battery/BMS are capable of handling it at that moment's state of charge.

If the battery/BMS arent' capable of more than what the one motor can put out then it won't change a thing to use both.

If you have a single motor and controller that's twice as capable of regen as the pair would be, all other conditions being equal, then you would get more out of that single motor than either single motor.

So, like most things, "it depends".

YOu can look thru my CrazyBike2 thread for the last several months, and there is some logged data on regen with one vs two hubmotors (of different types, but same controller capabilities). Sorry I don't remember the dates I posted it.

I was wondering what you thought about the idea of using regen to charge the batteries while putting along with the gas engine?

Depends on whether you like wasting gas you could be using to move forward in order to recharge batteries you could just plug in somewhere to recharge. And the heat the regen process will create in the motor and controller, as they try to slow down the bike that's being pushed forward (kind of like braking constnatly on a long dowhnill).

 

[diggler]

windings, a high turn-count and a low turn-count


https://d10kui8makj4zw.cloudfront.net/wp-content/uploads/2012/06/wireWindings.jpg

The pic above shows two stators from the same model of RC motor. There is only so much room for “copper fill”, so the stator teeth can be wound with either many turns of small diameter wire, or fewer turns of fatter wire. A low turn count is a “fast” motor, and…many turns would make the motor spin slower when they both have the same volts applied. If you buy a MAC geared hub, they are listed by turn-count. A 6T is the fastest, and they also stock a 7T, 8T, 10T, and a 12T motor.

I got that from electricbike .com

So if fine meaning many windings doesn't make a torque motor and course meaning less windings to take up the same amount of space for the windings making a speed motor what does make a motor a torque or a speed motor? And I'm not talking about geared motors.

I would think that a torque motor would be more efficient at regen because it wouldn't get as hot as fast. Right?

If both are identical, and you use just one, you'll get half the regen you would from both, as long as teh battery/BMS are capable of handling it at that moment's state of charge.

If the battery/BMS arent' capable of more than what the one motor can put out then it won't change a thing to use both.

If you have a single motor and controller that's twice as capable of regen as the pair would be, all other conditions being equal, then you would get more out of that single motor than either single motor.

So, like most things, "it depends".

Yes there are so many variables.

Okay so lets just say one 3000w motor & controller vs two 1500w motor & controller. Your saying the one would be more efficient correct? This I'm assuming is because of the extra heat loss using two.

Also with the idea of using gas to regen... what if one dialed in the regen so he could barely feel the drag. would it still not be worth the wasted gas?

 

[amberwolf]

The pic above shows two stators from the same model of RC motor. There is only so much room for “copper fill”, so the stator teeth can be wound with either many turns of small diameter wire, or fewer turns of fatter wire. A low turn count is a “fast” motor, and…many turns would make the motor spin slower when they both have the same volts applied. If you buy a MAC geared hub, they are listed by turn-count. A 6T is the fastest, and they also stock a 7T, 8T, 10T, and a 12T motor.

Different turn counts is (or can be) a totally separate thing from whether you use fine or coarse wire to wind with. I was only answering the latter question, which is why I said "all else being equal". If you wind two motors the same but use coarse wire on one and fine on another, they're going to have essentially identical performance, with only the difference in copper fill (if any) because of the different air gap sizes between wires causing any performance differences.

As for the differences between different turn count motors, then they will perform differently as generators exactly as they will perform differently as motors. If you want to know the details of that difference, and if ti will make any practical difference to your setup, you can check out simulators that have mulitple winds of the same motor and compare them (like on http://ebikes.ca/simulator ).

So if fine meaning many windings doesn't make a torque motor and course meaning less windings to take up the same amount of space for the windings making a speed motor what does make a motor a torque or a speed motor? And I'm not talking about geared motors.

As far as I can figure out, based on the discussion in the Science, Math, and Myth thread, there is no such thing as a "torque" motor vs a "speed" motor, if they are just wound differently but otherwise identical. You will want to read that thread yourself to see if you get the same thing I do out of it--there is some empirical data in some posts, and what there is appears to point that way to me.

I would think that a torque motor would be more efficient at regen because it wouldn't get as hot as fast. Right?

I don't know. But I would guess that the main thing about being efficient at regen is having a motor that is wound to produce a higher voltage as a generator (vs a different winding of the same motor), because then it will produce more volts per RPM, and so produce more voltage at a slower speed, and keep producing regen voltage closer to zero without the help of the controller doing as much fancy switching (whcih causes losses in the FETs as heat) The more voltage it produces, the more current that can then be forced back into the batteries, and the more drag there is on the motor, creating more braking force.

Okay so lets just say one 3000w motor & controller vs two 1500w motor & controller. Your saying the one would be more efficient correct? This I'm assuming is because of the extra heat loss using two.

Maybe.

But I'm not sure it's so simple as the actual wattage of the motor and controller, but rather how many amps of regen current it can push back into the battery, and thus how high a voltage it can produce relative to your then-present battery voltage.

How good a controller is at creating motive power may be very different from how good it is at creating regen power. Depends on how much they cared about making it good at that, cuz there's several ways to do it and I don't know how many of them do it the best way(s).

And of course with two wheels you'll get more contact patch to lessen skidding if you actually could brake harder, assuming your regen braking force could exceed the contact patch friction force.

Also with the idea of using gas to regen... what if one dialed in the regen so he could barely feel the drag. would it still not be worth the wasted gas?

If you can barely feel the drag, you're not generating much power. So it doesn't make much, if any difference how you set the regen: Either you use a lot of gas for a short time to generate power to recharge until full, or you use a little gas for a long time to generate the same power to recharge until full.

The difference in efficiency would depend on a bunch of things, which you woudl have to test experimentally to find out what was best for your specific equipment:

Battery voltage vs regen voltage controller can create at teh speed you'd be going (this will be different depending on the SoC of your battery at that time)

Efficiency of your gas engine at that speed under each amount of loading

Efficiency of charging at each different rate, for your battery and BMS (if any)

efficiency of motor/controller at each level of regen,

Etc.


To me it would never be "worth doing", because any way you do it, you'd be reducing your gas range by more than you would be recovering in your electric range.

It is exactly like any of hte other "charge while driving" schemes that take forward momentum of the vehicle (or energy from any of the motive power sources before or after it gets to the drivetrain) and convert it into stored power.

Any energy you recover will be done so in a less than 100% efficient manner, so the only thing it does is waste some of the range you'd've otherwise had in recharging the battery with some smaller percentage of that range.


The only case I can imagine it's usefulness is if the quietness of the electric motor is required for some parts of a very long journey that you
A) can't carry more battery for
B) can't carry any other form of charging for
C) can't plug in to charge for
D) can't just carry a generator for
and thus must use this method to ensure you have enough charge to get thru the quiet-required sections. But those sections would also have to be far enough apart that you'd have time to do the recharging at whatever rate you chose, or else you'd actually have to ride back along the path and waste time recharging via that method just so you could ride forward along the path again to get to and thru the quiet-required section.

I don't know of any actual scenario like that, but its' all I can imagine for one I'd ever want to do that.

 

[diggler]

As far as I can figure out, based on the discussion in the Science, Math, and Myth thread, there is no such thing as a "torque" motor vs a "speed" motor, if they are just wound differently but otherwise identical.

Really There must be some other difference between the HT3525 and the HS3540 then. All I have ever seen is just that there wound differently. I will definitely read up on that thread.

I would guess that the main thing about being efficient at regen is having a motor that is wound to produce a higher voltage as a generator (vs a different winding of the same motor)

hmmm... I'm definitely going to have to check that simulator out also. And look at generators as well..

How good a controller is at creating motive power may be very different from how good it is at creating regen power. Depends on how much they cared about making it good at that, cuz there's several ways to do it and I don't know how many of them do it the best way(s).

True true but what if all three were made by lyen the exact same way but just varied in power respectively?

Sorry I hope I'm not annoying you too much by going back and forth like this, and I hope I'm not veering this thread off topic too much.
And thank you for all the good links and threads to check out. I still need to look at the crazybike2 thread.
And I'd like to hear what others have to say! Especially Justin

To me it would never be "worth doing", because any way you do it, you'd be reducing your gas range by more than you would be recovering in your electric range.

It is exactly like any of hte other "charge while driving" schemes that take forward momentum of the vehicle (or energy from any of the motive power sources before or after it gets to the drivetrain) and convert it into stored power.

Any energy you recover will be done so in a less than 100% efficient manner, so the only thing it does is waste some of the range you'd've otherwise had in recharging the battery with some smaller percentage of that range.

I know I'm a dreamer That dam 100% efficiency will never be overcome...but what about trying to get as close as possible

I was thinking I would have two 72v 10ah-15ah batteries that I could switch back and forth to the motor so when one wore down I'd switch to the other but wait it gets way crazier. Before I'd switch I'd fast charge the battery with regen for a bit. Then switch and charge the dead one with a separate 12V battery. Wait it gets crazier. That 12V battery would be constantly getting charged via an array of devices. Which are two generators from the bullet head light generator kits (you know the ones that provide power for lights while moving with no battery, they do make 12V 6w, with just peddle power, but I'd have to run them through a rectifier) and some solar panels (nothing too crazy ie the solar bike) and last but not least some tinny wind turbines. The 12V battery would also power all the lights and other accessories. (I know it's going to be a beast! )

With any luck by the time I depleted the second battery I'd have half the original one charged back up.

But wait it gets crazier. After I switched the batteries back and forth a couple of times and drained them to a safe level as to not be too low to damage them. I'll pull the cord on the gas engine and Ill still be able to use the electric for regen and for momentary burst of fun! Until I got to some place where I could charge up/fill up again. I plan on taking a cross country trip two winters from now and I want something that will gooooo as far as possible just incase and so I don't have to stop every hundred miles or so.

Now I know I really got off topic, sorry O well I had to get it out. Is there a better place I can move this discussion to? I haven't been able to find it.

 

[John in CR]

While differently wound motors can perform identically when making torque, when reversing their role to produce regen braking the results are different. This is because the current limit of regen braking is the same between for two of the same model controllers. The end result since current is the same, is that the speed wind will have a lighter regen braking force. It's similar to the effect of using the motors at the same current, the speed wind will have less torque.

 

[amberwolf]

I was thinking I would have two 72v 10ah-15ah batteries that I could switch back and forth to the motor so when one wore down I'd switch to the other but wait it gets way crazier. Before I'd switch I'd fast charge the battery with regen for a bit. Then switch and charge the dead one with a separate 12V battery. Wait it gets crazier. That 12V battery would be constantly getting charged via an array of devices. Which are two generators from the bullet head light generator kits (you know the ones that provide power for lights while moving with no battery, they do make 12V 6w, with just peddle power, but I'd have to run them through a rectifier) and some solar panels (nothing too crazy ie the solar bike) and last but not least some tinny wind turbines. The 12V battery would also power all the lights and other accessories. (I know it's going to be a beast! )

With any luck by the time I depleted the second battery I'd have half the original one charged back up.

But wait it gets crazier. After I switched the batteries back and forth a couple of times and drained them to a safe level as to not be too low to damage them. I'll pull the cord on the gas engine and Ill still be able to use the electric for regen and for momentary burst of fun! Until I got to some place where I could charge up/fill up again. I plan on taking a cross country trip two winters from now and I want something that will gooooo as far as possible just incase and so I don't have to stop every hundred miles or so.

Basically all you are doing is finding more ways to waste yet more power.

Every stage you use to convert power wastes more of it.

Everything you do to pull motive power off the bike slows it down, and requires more power than you got out of that to speed it back up again, wasting either electricity or gas.

If you are using battery power to mvoe a bike and recharge a battery at the same time, you're wasting power.

You might as well just hook a big heater to your battery pack instead, and skip all the other steps.

 

[diggler]

While differently wound motors can perform identically when making torque, when reversing their role to produce regen braking the results are different. This is because the current limit of regen braking is the same between for two of the same model controllers. The end result since current is the same, is that the speed wind will have a lighter regen braking force. It's similar to the effect of using the motors at the same current, the speed wind will have less torque

Okay so they'd both be pretty much the same as far as efficiency go's but it would just take longer to come to a stop with the speed wound motor. Thus getting the same amount back in one full stop. But just at a longer distance and less of a breaking force then the torque wound motor.

Thanks for the input

Basically all you are doing is finding more ways to waste yet more power.

Every stage you use to convert power wastes more of it.

Everything you do to pull motive power off the bike slows it down, and requires more power than you got out of that to speed it back up again, wasting either electricity or gas.

If you are using battery power to mvoe a bike and recharge a battery at the same time, you're wasting power.

You might as well just hook a big heater to your battery pack instead, and skip all the other steps.

:lol: I have a feeling your right. But what's it going to hurt to try it out except the $30 a piece they cost. at least I wont be wasting power going down hill. When I do this if I do this I'll make sure to post the results. although without a controlled environment, like an indoor track r something, how could one know if the results were accurate? At least someone might let me use one for just the electric part of the test.

 

[Alan B]

While differently wound motors can perform identically when making torque, when reversing their role to produce regen braking the results are different. This is because the current limit of regen braking is the same between for two of the same model controllers. The end result since current is the same, is that the speed wind will have a lighter regen braking force. It's similar to the effect of using the motors at the same current, the speed wind will have less torque.

Hi John. This seems to be a variant of the same thing. Different wind but otherwise identical motors will make the same regen power, just at different voltage/current combinations. Variations in the controller are required to convert this regen power to the battery. Simple buck/boost voltage conversions are slightly less efficient as the voltage difference increases.

 

[justin_le]

As far as I can figure out, based on the discussion in the Science, Math, and Myth thread, there is no such thing as a "torque" motor vs a "speed" motor, if they are just wound differently but otherwise identical.

Really There must be some other difference between the HT3525 and the HS3540 then. All I have ever seen is just that there wound differently. I will definitely read up on that thread.

You'll notice that (ableit after some lobbying) Crystalyte is no longer referring to the motors as HT3525 and HS3540, but just H3525 and H3540? The original scheme with HT supposedly meaning "High Torque" and HS supposedly meaning "High Speed" was only propagating this same misinformation that the different windings result in different motor torque capabilities, and that there is a tradeoff between speed and torque. The H3540 and H3525 motors are wound differently, yes, and they are both fundamentally capable of exactly the same speeds and torques, it's just that the 3540 winding does it at a lower voltage and higher current than the 3525.

Back on the regen subject a bit:

While differently wound motors can perform identically when making torque, when reversing their role to produce regen braking the results are different. This is because the current limit of regen braking is the same between for two of the same model controllers. The end result since current is the same, is that the speed wind will have a lighter regen braking force.

This is a fairly valid point with real-world systems using existing motor controllers. When using the motor under power, people are very rarely running it at the phase current limit, they are generally only hitting the battery current limit, and so in practice there is very little difference in acceleration torque with a fast or a slow winding motor, as both motors are experiencing the same net power input as determined by the controller's battery current limit. However, the regen controllers generally operate regen as a fixed phase current, rather than a fixed battery current, and so a faster wind motor will have less braking torque (and also less amps going into the battery).

If you can set the controller's regen braking current make it proportionally higher when running the fast wind motor, then the performances become identical again. Same braking torque with the same amps going back into the battery pack, even though the amps through the motor wind itself is higher.

 

[diggler]

Right its because with more turns the motor makes more current/inductance in proportion to distance the motor turns. Right?
So since the motor coils are actually having to create higher amps in a less turn count motor to produce the same amount of current into the battery. Does that mean that the less turn count motor is slightly less efficient and regenerating power back to the battery because the windings would get slightly hotter?
Would the controller get hotter in more or less turns, or would it be the same in both? (I think it would be the same)

 

[nechaus]

I used a nanotech pack that was capable of a 5c charge rate.. 72volt 20ah, Used this pack for about 12 months with no issues of cells dying, it's behaviour was normal.. I have also used 72 volt 16ah regular 20c , 1-2 c charge rate max...

I never shorted the life of my packs and i was getting some pretty hefty regen currents, I had the attitude if it die's, I don't care..

Both packs are now about 2 years old, could not tell you how many cycles but they are still good today, Both packs were used off road and being abused.


The only issue I ever got with regen was additional motor heat...

I do remember seeing just under 20% regen on the CA. Running an external shunt....
I love regen and I will always use it on my ebike's... I cannot stand consistently wearing out my mechanical ones... only on one bike I used motor bike brakes.


Seems like adding a super cap bank is pointless unless they fit in the size of your hand, id rather carry a higher capacity battery

 

[nechaus]

im guessing you probably could get a small super cap bank to fit in you're hand with all the additional circuitry

 

[Punx0r]

Sorry, noob question: when performing regen does the controller operate as a boost converter?

 

[Alan B]

Effectively it must since battery voltage is higher than back EMF (unless field weakening was in use).

 

[Punx0r]

Thanks, that was what I was thinking

 

[DasDouble]

Sorry maybe someone wrote alredy the question but I don´t want to read so much stuff:

What brakes do you recomment? Maybe the Magura MT5e ? Or maybe the Tektro E-Brakes???

-Cheers, Elias

 

[amberwolf]

Sorry maybe someone wrote alredy the question but I don´t want to read so much stuff:

That's what the search function is for.

 

[John in CR]

Sorry maybe someone wrote alredy the question but I don´t want to read so much stuff:

That's what the search function is for.

Since that still requires reading, I wish him luck learning about ebikes on YouTube and Twitter.

 

[DasDouble]

Sorry maybe someone wrote alredy the question but I don´t want to read so much stuff:

That's what the search function is for.

Since that still requires reading, I wish him luck learning about ebikes on YouTube and Twitter.

Haha^^ I nearly know everything I need alredy. I just don´t know which brakes are the best If no one wants to answer my question, Im going for the Magura e-brake

-Elias

 

[justin_le]

Haha^^ I nearly know everything I need alredy. I just don´t know which brakes are the best If no one wants to answer my question, Im going for the Magura e-brake

Hi Elias to get an answer that, you should simply start a new thread in an appropriate forum section called "Ebrake lever recommendation, Magura or Tektro?" or something along those lines and then people would be inclined to help you and perhaps carry on a discussion on that topic. The point of this thread is the technical analysis of regen on ebike systems so it's quite out of place for what you're asking.

On the original topic, it was interesting to reread the initial test results and conclusions from 7 years ago when I did this little investigation and see it all holds pretty much exactly the same today. Running the field oriented motor controllers nowadays I'm typically seeing 6-7% regen values riding around town, and about 12 wh/km for my usage. That results in 0.8 Wh/km of recaptured energy, while the cogging drag of my hub motor consumes ~0.6 wh/km. I use the motor power about 70% of the time, so if my hub could freewheel then I'd only stand to gain ~0.18 wh/km from eliminating that motor drag, while at the same time loosing the 0.8 wh/km that regen gets me.

Has anyone else been doing any data logging and studies of their regen statistics? One thing that I would like to try and work out is the ratio of regen coming from changes in elevation versus the amount from stop and go. This would be depend hugely on the riding scenario, regen from a flat city ride will be all stop and go, and regen from a rolling country side road would be all elevation change, and typical trips in Vancouver must be something in between.

 

[DasDouble]

Haha^^ I nearly know everything I need alredy. I just don´t know which brakes are the best If no one wants to answer my question, Im going for the Magura e-brake

Hi Elias to get an answer that, you should simply start a new thread in an appropriate forum section called "Ebrake lever recommendation, Magura or Tektro?" or something along those lines and then people would be inclined to help you and perhaps carry on a discussion on that topic. The point of this thread is the technical analysis of regen on ebike systems so it's quite out of place for what you're asking.

On the original topic, it was interesting to reread the initial test results and conclusions from 7 years ago when I did this little investigation and see it all holds pretty much exactly the same today. Running the field oriented motor controllers nowadays I'm typically seeing 6-7% regen values riding around town, and about 12 wh/km for my usage. That results in 0.8 Wh/km of recaptured energy, while the cogging drag of my hub motor consumes ~0.6 wh/km. I use the motor power about 70% of the time, so if my hub could freewheel then I'd only stand to gain ~0.18 wh/km from eliminating that motor drag, while at the same time loosing the 0.8 wh/km that regen gets me.

Has anyone else been doing any data logging and studies of their regen statistics? One thing that I would like to try and work out is the ratio of regen coming from changes in elevation versus the amount from stop and go. This would be depend hugely on the riding scenario, regen from a flat city ride will be all stop and go, and regen from a rolling country side road would be all elevation change, and typical trips in Vancouver must be something in between.

Ok thank you for your answer. I will do that

-Have a nice day, Elias

 

[rowbiker]

Has anyone else been doing any data logging and studies of their regen statistics? One thing that I would like to try and work out is the ratio of regen coming from changes in elevation versus the amount from stop and go. This would be depend hugely on the riding scenario, regen from a flat city ride will be all stop and go, and regen from a rolling country side road would be all elevation change, and typical trips in Vancouver must be something in between.

While not formally accumulating regen data as you have been, I keep coming back to a single conclusion: I really love regen as a way of slowing down an electric vehicle, vs. using a mechanical "brake". Lately I've been splitting my miles between ebikes and a Tesla Model S, and in both cases I'm convinced that I would keep the regen in the engineering mix *even if* there was no current going back into the battery pack at all. In the Model S, I *rarely* touch the brake pedal -- typically only just prior to pressing the "Park" button and getting out of the car. On the two ebikes I'm currently riding, I've installed separate pushbuttons on the handlebars that are the equivalent of electric braking, without having to touch the bike's actual brakes.

So far I've only encountered one annoying wrinkle on the ebike regen function -- it doesn't work when the battery pack is fully charged. So, if starting out with a topped-off pack, I try to run the pack down a bit before I think I'll need to be using the brakes... dumb, but there you have it. Might just have to figure out some "load shedding" device that kicks in to accept the charging current if the battery has no room for it -- or just not charge the pack fully to begin with.

Riding around the Twin Cities (also relatively flat), I rarely get much more than 3% regen, as measured by a CA-v3, but I do get a way to slow down that doesn't annoy me.