Pedelec Law - The Details

flecc

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Oct 25, 2006
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Thank you for a very full and interesting post. I know that the UK legal motor size limit is 250W but am puzzled how Bosch manage to make a whole range of motors at prices that go up with torque from 40Nm up to 85Nm, are these all 250W, just that the more expensive ones have more powerful watts?
The 250 watts is a rating, little more then a legal nicety. In practice the actual power obtainable usually ranges from about 400 to 600 watts and can even be higher. The ways of measuring it set out in technical document EN15194 allow considerable flexibility both of measurement and interpretation for entirely practical reasons, since a fixed limit of actual 250 watts would make pedelecs virtually useless for many.

I can illustrate how extreme this can become with the example of the Lynch motor for pedicabs (powered bicycle rickshaws) used to carry two or three passengers by the cyclist pedalling. That motor is also nominally 250 watts and in it's upper speed ranges to about 8 to 10 mph it does only produce a few hundred watts.

But when hitting a hill with passengers on board, as it slows right down the power outputted rises with reducing speed and can reach almost 5 kilowatts with immense torque at a very slow crawl. With the rider having a suitably low gear to also pedal assist efficiently at a crawl, it can climb any reasonable hill with an all up weight of over 400 kilogrammes, albeit very slowly.

So in a nutshell, the regulations allow pedelecs to be practical for every use with turning them into speed machines. Cycles Maximus, one of the producers of such a pedicab also made a 5 cwt (250 kilo) payload van version.
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Tony1951

Pedelecer
Mar 27, 2016
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Good question, maybe they are pulling the wool and labelling them as 250w so not to be illegal. How one gets some twice the stated NM without the motor being rated higher I don't know.
Needs someone better to explain, is it down to programming wizardry, gearing or stronger build components ? Are these bikes actually 350 /500w rated motors as double the torque in NM doesn't appear out of thin air.
Gearing down would change the output torque, I think, but you would lose top speed, unless the motor speed also increases. I suppose the measurement of motor power is based on input power. My mid drive Bafang in pedal assist draws a pretty constant 250 watts under load, though it will occasionally go a little higher, but this is temporary. If I am in my bottom gear the torque at the wheel must be much higher than when in a higher gear. The bike also has a throttle which when pressed and climbing, will increase input power to 500 watts while it is held. I try to avoid this to protect the controller. I used it yesterday when climbing a steep hill on an off road track. At times it was so steep I juts got off and pushed. I didn't want to start labouring the motor with the throttle on and heat things up too much.
 
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vfr400

Esteemed Pedelecer
Jun 12, 2011
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Thank you for a very full and interesting post. I know that the UK legal motor size limit is 250W but am puzzled how Bosch manage to make a whole range of motors at prices that go up with torque from 40Nm up to 85Nm, are these all 250W, just that the more expensive ones have more powerful watts?
It's not a size limit, neither is it a power limit. The rule is that the motor must be "rated" at no more than 250w. There is no rule about how the rating should be applied. Normally, manufacturers would rate their motors as high as possible because it's a selling point. The motors would then be tested that they don't burn when run at the rated power. Ebikes motors can be under-rated. If the manufacturers rated a motor at 250w, which is capable of running at 500w without burning, it will always pass the 250w rating test. In other words, the law actually has no limit on power output.. The only requirement is that the manufacturer of the bike or motor must make sure that the motor can run at 250w without burning while running in its most efficient zone and then declare it as rated at 250w. You can't use a motor rated at more than 250w even if you run it with 10w maximum power.

Manufacturers tend to use torque rather than power when they specify motors, obviously for political reasons.
 
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vfr400

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Gearing down would change the output torque, I think, but you would lose top speed, unless the motor speed also increases. I suppose the measurement of motor power is based on input power. My mid drive Bafang in pedal assist draws a pretty constant 250 watts under load, though it will occasionally go a little higher, but this is temporary. If I am in my bottom gear the torque at the wheel must be much higher than when in a higher gear. The bike also has a throttle which when pressed and climbing, will increase input power to 500 watts while it is held. I try to avoid this to protect the controller. I used it yesterday when climbing a steep hill on an off road track. At times it was so steep I juts got off and pushed. I didn't want to start labouring the motor with the throttle on and heat things up too much.
At full throttle or on max assist, a BBS01 allows 15 amps into the motor unless you reprogrammed it for up to 18A. The spinning motor generates a back emf in direct proportion to its speed. The back emf has the effect of reducing the voltage to the motor, which means not so much current can get through the motor as it speeds up.

To translate that into what happens during usage, at zero rpm, the maximum current would go into the motor and burn it out, but the controller regulates it to 15A, so at low speed, you'll be taking 15 amps from the battery and you'd see about 600w on the meter, but at higher speed the current reduces in proportion to the speed until it becomes zero at around 83 rpm. The power you take from the battery (when demanding max) therefore varies with your crank speed - anything between 600w and zero. The faster your cadence, the less power the motor can take from the battery.

Output power depends on efficiency, which also depends on speed. You get max efficiency at about 75% max rpm, which would be around 60 rpm. At that speed, efficiency would be around 70%, so output power at the back wheel would be about 175w when you see 250w on the meter. When you draw maximum current, efficiency would be below 50%, so less than 300w when pedalling slowly. Anything faster than 60 rpm, the current will be reducing, so you'll see less power on the meter, though efficiency will still be high.

In summary, you get about 300w output power when pedalling slowly up a steep hill, around 175w pedalling at a comfortable 60 rpm and about 50w if you have a high cadance of say 80 rpm. On the plus side, the faster you pedal, the more power you can make to add to the bike.
 
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Tony1951

Pedelecer
Mar 27, 2016
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In summary, you get about 300w output power when pedalling slowly up a steep hill, around 175w pedalling at a comfortable 60 rpm and about 50w if you have a high cadance of say 80 rpm. On the plus side, the faster you pedal, the more power you can make to add to the bike.
Yes that corresponds with my experience with the motor, albeit that until I got my new varicfocals yesterday, I was finding it impossible to read the actual watts being consumed on the display and only had a rough idea. Thanks for the details on the performance of the controller and its outputs. The back emf discussion takes me right back to physics lessons in the 1960s, and the time I started my windscreen wipers when there was six inches of solid snow on the screen and the stalled motor blew the wiper fuse in about two seconds. I am always careful never to stall an electric motor now. That's why I baled out yesterday on 30 degree slopes on a rough and rocky track. It might have managed in bottom gear, but it wasn't worth the risk.



43798
 
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soundwave

Esteemed Pedelecer
May 23, 2015
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the standard 250w motors and the sclass ones are the same inside it is the factory programming that is different like the ones that go to the usa that have a 20mph limit but in some states the walk button is classed as a throttle so must be turned off at the factory.

under 15mph the motor can use its full power otherwise it would be useless for going up hills ect so the motor can use around 800w under 15mph.

so with a dongle you can turn them in to sclass motors but this only removes the speed limit.
 
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flecc

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Oct 25, 2006
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I suppose the measurement of motor power is based on input power.
There is no official measurement of power for separate pedelec motors, as vfr400 has posted above, it's what the manufacturer says it is.

The power tests in the official technical document EN15194 are only for complete pedelec bicycles and the most realistic one for a manufacturer to carry out is a test of acceleration capability:

Test procedure

a) Pre-condition the EPAC by running it for 5 min at 80% of the maximum assistance speed as declared by the manufacturer.

b) Stop the bicycle.

c) Note the time between the action start and the EPAC to travel 20 metres (T)

d) Verify the speed value is equal to or less than the maximum speed declared by the manufacturer after 20 metres (D).

Then the power is derived from this formula:

Power equals M times 2D squared over T cubed

where P= power in watts, D= 20 metres, M= mass of rider plus bike in Kg, T = time in seconds to cover distance D.
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vfr400

Esteemed Pedelecer
Jun 12, 2011
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There is no official measurement of power for separate pedelec motors, as vfr400 has posted above, it's what the manufacturer says it is.

The power tests in the official technical document EN15194 are only for complete pedelec bicycles and the most realistic one for a manufacturer to carry out is a test of acceleration capability:

Test procedure

a) Pre-condition the EPAC by running it for 5 min at 80% of the maximum assistance speed as declared by the manufacturer.

b) Stop the bicycle.

c) Note the time between the action start and the EPAC to travel 20 metres (T)

d) Verify the speed value is equal to or less than the maximum speed declared by the manufacturer after 20 metres (D).

Then the power is derived from this formula:

Power equals M times 2D squared over T cubed

where P= power in watts, D= 20 metres, M= mass of rider plus bike in Kg, T = time in seconds to cover distance D.
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Didn't they remove the acceleration test from the standard, Flecc? Anyway, it's impossible to do when the motor only works with pedalling, especially if you have a torque multiplication system like most bikes have.
 

flecc

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Oct 25, 2006
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Didn't they remove the acceleration test from the standard, Flecc? Anyway, it's impossible to do when the motor only works with pedalling, especially if you have a torque multiplication system like most bikes have.
It's still an option in Annex D of the regulation last I saw it. But as you say in practical terms its a bit of a nonsense with many of today's pedelecs. As is the test of power at the motor "shaft" which isn't accessible without altering the pedelec to the degree that a test outcome is meaningless in relation to the product on sale.

The present laissez-faire is best, allowing whatever motor power is necessary for an application, even 5kW if needed as I posted above. It makes even more sense now that all pedelec weight limits have been removed.
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GSV3MiaC

Pedelecer
Jun 6, 2020
185
119
Torque and power are not directly related. That's how you can get a torque wrench delivering a wide range of torques from one standard wimpy human being on the input end. 'Give me a long enough lever and a place to stand' etc .. NM = Newton Meters, you can just fiddle the meters part (or in the case of a motor, the gearing).
 

flecc

Member
Oct 25, 2006
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How tough the Pedelec law could be:

France does not look kindly upon e-bike owners that hot rod their wheels. The country has introduced a law that could see offenders slapped with a maximum fine of €30,000 (US$34,000), and up to a year in jail. And they could have their driving licence suspended for up to three years.

There are no caveats or loopholes, either -- do anything to tune your e-bike for more speed or power and you could feel the wrath of the new law, known as French statutory provision L317-1. The rules also apply to importers, distributors and dealers.

Information Link
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guerney

Esteemed Pedelecer
Sep 7, 2021
876
354
If I installed a 250w mid drive kit onto a bike made in 2006, can I legally use the throttle exclusively to propel the bike to 15.5mph?
 

soundwave

Esteemed Pedelecer
May 23, 2015
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no because it is a diy bike so age of the frame does not matter in that case but if you want a throttle then fit it and forget about it.

the other week my m8 decided to get pissed and crashed in to a steal barrier going 40mph and snapped it in half and he had a throttle plod took the bike but as yet no charges.

i have also seen a fair amount of 1000w hub motors being used for Deliveroo ect for take away meals and they dont get stopped.

so if it is ok for them then it is ok for you ;)
 

guerney

Esteemed Pedelecer
Sep 7, 2021
876
354
no because it is a diy bike so age of the frame does not matter in that case but if you want a throttle then fit it and forget about it.

the other week my m8 decided to get pissed and crashed in to a steal barrier going 40mph and snapped it in half and he had a throttle plod took the bike but as yet no charges.

i have also seen a fair amount of 1000w hub motors being used for Deliveroo ect for take away meals and they dont get stopped.

so if it is ok for them then it is ok for you ;)
Yes I thought so, DIY needn't apply.

I read about your friend on another thread, I forget which. I hope he recovers well... Breakages can lead to lifelong arthritis, depending on which bones were broken and how well they healed... so a set of injuries that sever could well be the start of the pain.
 

flecc

Member
Oct 25, 2006
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If I installed a 250w mid drive kit onto a bike made in 2006, can I legally use the throttle exclusively to propel the bike to 15.5mph?
It's double no. Any conversion to an e-bike after 1st January 2016 cannot legally have an independently acting full throttle.

And in any case all kit bikes are technically illegal, the permissive law for pedelecs only applies to complete manufactured pedelecs.

For clarification go the first post in this thread and scroll down to Kit Motors within that long opening post.

There's further explanation in this link
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vfr400

Esteemed Pedelecer
Jun 12, 2011
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If I installed a 250w mid drive kit onto a bike made in 2006, can I legally use the throttle exclusively to propel the bike to 15.5mph?
Contrary to what the others have said, the answer could be actually yes, depending on what you mean by exclusively and what you mean by propel. One could argue that the answer is no on the basis that a throttle can't propel anything. All the throttle does is regulate the speed. It's an input device to tell the controller how fast you want to go. It doesn't provide any power. There are no rules about which input devices you can or can't use. Many bikes have control panels that give a stepped throttle signal for the speed control. Nobody questions their legality.

When you say "exclusively", you have to be more precise in what you mean. You could argue that it isn't being used exclusively if the pedals must rotate too. I made a bike where the motor rotated the pedals as well as the back wheel so that the pedals always rotated when the motor was driving the bike and the motor was stopped when the pedals stopped rotating. In that case the throttle was an exclusive input device.

The requirement for a pedelec type bike is that the power must stop when the pedals stop rotating. It doesn't in any way say what sort of speed or power regulation device you must use, neither does it say how hard or fast the pedals have to rotate. Also, the bike must be able to be propelled by the pedals at a safe speed without the motor power, so the pedals must be functional.

The Wisper Wayfarers are certified compliant and they have throttles that work up to 15.5mph.

Thinking about functionality of the pedals, I'm now wondering whether those chainless electric bikes, like the Mando Footloose are actually legal since the drive only comes from the motor. They can't be propelled with the motor switched off.
 
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flecc

Member
Oct 25, 2006
49,038
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Contrary to what the others have said, the answer could be actually yes, depending on what you mean by exclusively and what you mean by propel. One could argue that the answer is no on the basis that a throttle can't propel anything. All the throttle does is regulate the speed. It's an input device to tell the controller how fast you want to go. It doesn't provide any power. There are no rules about which input devices you can or can't use. Many bikes have control panels that give a stepped throttle signal for the speed control. Nobody questions their legality.

When you say "exclusively", you have to be more precise in what you mean. You could argue that it isn't being used exclusively if the pedals must rotate too. I made a bike where the motor rotated the pedals as well as the back wheel so that the pedals always rotated when the motor was driving the bike and the motor was stopped when the pedals stopped rotating. In that case the throttle was an exclusive input device.

The requirement for a pedelec type bike is that the power must stop when the pedals stop rotating. It doesn't in any way say what sort of speed or power regulation device you must use, neither does it say how hard or fast the pedals have to rotate. Also, the bike must be able to be propelled by the pedals at a safe speed without the motor power, so the pedals must be functional.
All these more complex arguments will come to nought once a case is referred to a senior court such as the high court, appeal court or supreme court. There one or more senior judges, often with the assistance and advice of a master at the high court, will decide what the spirit of the law is. i.e. What parliament intended.

That can only have one outcome since the spirit of the law is contained within its title:

Electric Assist Pedal Cycles

i.e. The electrical element is only there to help the rider propel the bicycle, so merely spinning the pedals does not constitute the rider propelling the bicycle with the motor assisting.
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vidtek

Esteemed Pedelecer
Mar 29, 2015
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I suppose it will eventually get to the high court to decide finally. The spirit of the legislation should not preclude the use of a throttle to start off and assist the rider to proceed safely, up an incline for instance instead of them wobbling all over the road until they can get going properly. That surely is not the intention of the legislation, to make cycling more dangerous especially for our more senior or disabled riders. Surely common sense will eventually prevail and the intention of keeping the speed down to a reasonable 15mph via throttle is where the emphasis should be?
 
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guerney

Esteemed Pedelecer
Sep 7, 2021
876
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Contrary to what the others have said, the answer could be actually yes, depending on what you mean by exclusively and what you mean by propel. One could argue that the answer is no on the basis that a throttle can't propel anything. All the throttle does is regulate the speed. It's an input device to tell the controller how fast you want to go. It doesn't provide any power. There are no rules about which input devices you can or can't use. Many bikes have control panels that give a stepped throttle signal for the speed control. Nobody questions their legality.

When you say "exclusively", you have to be more precise in what you mean. You could argue that it isn't being used exclusively if the pedals must rotate too. I made a bike where the motor rotated the pedals as well as the back wheel so that the pedals always rotated when the motor was driving the bike and the motor was stopped when the pedals stopped rotating. In that case the throttle was an exclusive input device.

The requirement for a pedelec type bike is that the power must stop when the pedals stop rotating. It doesn't in any way say what sort of speed or power regulation device you must use, neither does it say how hard or fast the pedals have to rotate. Also, the bike must be able to be propelled by the pedals at a safe speed without the motor power, so the pedals must be functional.

The Wisper Wayfarers are certified compliant and they have throttles that work up to 15.5mph.

Thinking about functionality of the pedals, I'm now wondering whether those chainless electric bikes, like the Mando Footloose are actually legal since the drive only comes from the motor. They can't be propelled with the motor switched off.

Was that with a KT controller? My next ebike may well have to be with a KT and a rear hub, seems more adaptable to comply with UK law than bafang.
 

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