250Watt whats it really

[Linfitter]

The 250Watt Maximum Continuous Power Rating what is it?​

The simple answer to this question is it is a CODE an understanding of which enables Motor Builders/ Manufactures to be able to build a motor within the guidelines laid down by European Government(s)( EU) and other individual buyers.

It is a means by which to find a PRE Motor build AMPACITY wire rating the definition of which is: - the maximum amount of electric current that a wire (the Conductor) can carry continuously without exceeding its temperature rating -(the safety factor) -it is measured in amperes and depends on the size of the wire and ambient temperature. By looking up on a Wire Gauge Chart a particular wires’ current carrying capacity and then multiplying this by the batteries’ mean average power an idea of a useable power rating in Watts can be achieved. Government has used a wire rating that carries 6.944 amps then multiplied this by 36 volts to get a 250Watt rating. A motor built and operated up to this rating can be used all day without overheating. It is safe.

Unfortunately, because we British have lost out when it comes to Wire Gauge Charts we do the same as everybody else and use the American Wire Gauge (AWG) system but because this system is based on two different temperature ranges neither of which, although good enough for general purposes, is accurate enough when put up against the EU’s assisted bicycle motor testing process, which in testing for the legality of such, has set the ‘ambient’ temperature at a lowly and constant 30˚ Centigrade, Consequently, our Government who is aware of all the confusion it is causing refuses to use the term Ampacity - and has stated instead that ‘an Insulated wire has a voltage rating and a maximum conductor temperature rating it doesn’t need to have an Ampacity rating as that depends on the surrounding ambient temperature’ - consequently, when asked to furnish a simple explanation to the question above they cannot come up with an answer and cop out by pointing the enquirer (me) and anybody else that enquires to all the information to be found in such as that that is in the EN15194 and UN/ECE Regulation N0 85 legislation and that information relates to aspects of POST motor build and testing which are expensive to buy and runs into many thousands of words none of which are relevant to a PRE motor build consumer question the answer to which runs into forty four small simple words:-
It is not a reference to a Peak Power Rating.
It is a reference to a Power point (250watts) from which the (AMPACITY) wire rating used in a PRE motor build can be determined in order to conform to OHM’s Law of safe usage.

The EU governments(s) were quite aware of the power limitations of such a low rating so decided to ditch all that bumph about safety and beggar the consequences legal or otherwise and decided to up the ante and set the bar twice as high setting a maximum useable power limit to an unsafe heat generating 540 Watts. (Reference to this was later rescinded as exceeding the limit would bring failure under the 30min rule).
AND THE CONSEQUENCES ARE
The administration of Law is compromised by the hypocritical nature of the present means of rating an EAPC motor build and a EU advisory committees recommendation that future motor builds were based on the Wattage available under the EAPC Bicycle Classification and not on an Ampacity rating was turned down. It is my opinion in view of the statement above that it will not be long (due to the lack of administration of Law) before bicycles presently looked on as being illegal 350-500 Watts will providing they have been manufactured with the proper wire build to conform to OHM’s Law (like house wiring has to) and cannot exceed 25kmp/15½mph in speed will be classed as legal.
Yours Linfitter.

 

[Woosh]

Ohm's law is not relevant for evaluation of motors. On average , 80 to 85% of the power supplied to a motor is converted into mechanical power. When the motor stalls, the controller will cut power to the motor.

 

[saneagle]

The 250Watt Maximum Continuous Power Rating what is it?​

The simple answer to this question is it is a CODE an understanding of which enables Motor Builders/ Manufactures to be able to build a motor within the guidelines laid down by European Government(s)( EU) and other individual buyers.

It is a means by which to find a PRE Motor build AMPACITY wire rating the definition of which is: - the maximum amount of electric current that a wire (the Conductor) can carry continuously without exceeding its temperature rating -(the safety factor) -it is measured in amperes and depends on the size of the wire and ambient temperature. By looking up on a Wire Gauge Chart a particular wires’ current carrying capacity and then multiplying this by the batteries’ mean average power an idea of a useable power rating in Watts can be achieved. Government has used a wire rating that carries 6.944 amps then multiplied this by 36 volts to get a 250Watt rating. A motor built and operated up to this rating can be used all day without overheating. It is safe.

Unfortunately, because we British have lost out when it comes to Wire Gauge Charts we do the same as everybody else and use the American Wire Gauge (AWG) system but because this system is based on two different temperature ranges neither of which, although good enough for general purposes, is accurate enough when put up against the EU’s assisted bicycle motor testing process, which in testing for the legality of such, has set the ‘ambient’ temperature at a lowly and constant 30˚ Centigrade, Consequently, our Government who is aware of all the confusion it is causing refuses to use the term Ampacity - and has stated instead that ‘an Insulated wire has a voltage rating and a maximum conductor temperature rating it doesn’t need to have an Ampacity rating as that depends on the surrounding ambient temperature’ - consequently, when asked to furnish a simple explanation to the question above they cannot come up with an answer and cop out by pointing the enquirer (me) and anybody else that enquires to all the information to be found in such as that that is in the EN15194 and UN/ECE Regulation N0 85 legislation and that information relates to aspects of POST motor build and testing which are expensive to buy and runs into many thousands of words none of which are relevant to a PRE motor build consumer question the answer to which runs into forty four small simple words:-
It is not a reference to a Peak Power Rating.
It is a reference to a Power point (250watts) from which the (AMPACITY) wire rating used in a PRE motor build can be determined in order to conform to OHM’s Law of safe usage.

The EU governments(s) were quite aware of the power limitations of such a low rating so decided to ditch all that bumph about safety and beggar the consequences legal or otherwise and decided to up the ante and set the bar twice as high setting a maximum useable power limit to an unsafe heat generating 540 Watts. (Reference to this was later rescinded as exceeding the limit would bring failure under the 30min rule).
AND THE CONSEQUENCES ARE
The administration of Law is compromised by the hypocritical nature of the present means of rating an EAPC motor build and a EU advisory committees recommendation that future motor builds were based on the Wattage available under the EAPC Bicycle Classification and not on an Ampacity rating was turned down. It is my opinion in view of the statement above that it will not be long (due to the lack of administration of Law) before bicycles presently looked on as being illegal 350-500 Watts will providing they have been manufactured with the proper wire build to conform to OHM’s Law (like house wiring has to) and cannot exceed 25kmp/15½mph in speed will be classed as legal.
Yours Linfitter.

Sorry, great effort, but I have to score it at 2/10. You need to study further before submitting a revised paper.
According to the European standard EN15194, there is no maximum power limit. There are no guidlines, nor test standards that say how the motor should be rated. The only requirement is that it must pass the maximum rating test, where it must not overheat when run at 250w when running in its most efficient zone. Basically a manufacturer can design a motor for whatever power they want, then stamp it 250w to make it legal.

I know of motors that are stamped 250w and can run all day at 3,500w, which have been certified as complying with EN15194.

Where did you get 540w from? I never heard anybody else ever mention that figure.

 

[Linfitter]

Ohm's law is not relevant for evaluation of motors. On average , 80 to 85% of the power supplied to a motor is converted into mechanical power. When the motor stalls, the controller will cut power to the motor.

Mr reference to OHM's Law is in regards to the heat carrying aspect of it. Anything that does't conform to OHM's law must be overheating. Thats why I used this particular Physists Law
regards Linfitter

 

[Woosh]

Mr reference to OHM's Law is in regards to the heat carrying aspect of it. Anything that does't conform to OHM's law must be overheating. Thats why I used this particular Physists Law
regards Linfitter

I may have misunderstood you but in case anyone thinks that the heat is dissipated by the wires. It's only partially true. Most of the heat is generated directly in the magnetic circuit, the flux carrying parts (rotor and stator) of the motor due to the rapid changes in flux density of the iron stack and eddy currents in the permanent magnets, also heat is generated by friction loss in the gearbox and transmission. The winding is responsible for some of the losses, but it is usually less than 20% of the total heat.

 

[Sturmey]

EN 15194:2009 (E)
15
4.2.7 Maximum power measurement
4.2.7.1 Measurement at the engine shaft
The maximum continuous rated power shall be measured according to EN 60034-1 when the motor reaches
its thermal equilibrium as specified by the manufacturer.
NOTE Thermal equilibrium: temperatures of motor parts do not vary more than 2K per hour.
In circumstance where the power is measured directly at the shaft of the electronic motor, the result of the
measurement shall be decreased by 1,10 to consider the measurement uncertainty and then by 1,05 to
include for example the transmission losses, unless the real values of these losses are determined.
EN15194 2009

The 250W rating refers to mechanical output. A motors mechanical output can not be measured by measuring its input, whether this is coal, oil or electricity. (It can only be guessed by assuming a certain efficiency and this is easier to do with an electric motor.) (imo)
If you think about it this make sense. You don't rate the power of a steam or diesel engine by the amount of coal or diesel it burns.

 

[saneagle]

The 250W rating refers to mechanical output. A motors mechanical output can not be measured by measuring its input, whether this is coal, oil or electricity. (It can only be guessed by assuming a certain efficiency and this is easier to do with an electric motor.) (imo)
If you think about it this make sense. You don't rate the power of a steam or diesel engine by the amount of coal or diesel it burns.

EN 60034-1 specifies that before testing, you must find the peak efficiency RPM and do the rating test at that speed. To pass the test, the temperature must stabilise at the rated power, which is 250w in the case of EN15194. Naturally, if you had a motor that could handle 100kW, it would pass that test at 250w. Absurd as it seems, you could take that 100kw motor, stamp it 250w, and it would comply with EN15194, as there are no regulations on under-rating a motor. There's only EN 60034-1, which is about over-rating.

 

[Linfitter]

The 250Watt Maximum Continuous Power Rating what is it?​

The simple answer to this question is it is a CODE an understanding of which enables Motor Builders/ Manufactures to be able to build a motor within the guidelines laid down by European Government(s)( EU) and other individual buyers.

It is a means by which to find a PRE Motor build AMPACITY wire rating the definition of which is: - the maximum amount of electric current that a wire (the Conductor) can carry continuously without exceeding its temperature rating -(the safety factor) -it is measured in amperes and depends on the size of the wire and ambient temperature. By looking up on a Wire Gauge Chart a particular wires’ current carrying capacity and then multiplying this by the batteries’ mean average power an idea of a useable power rating in Watts can be achieved. Government has used a wire rating that carries 6.944 amps then multiplied this by 36 volts to get a 250Watt rating. A motor built and operated up to this rating can be used all day without overheating. It is safe.

Unfortunately, because we British have lost out when it comes to Wire Gauge Charts we do the same as everybody else and use the American Wire Gauge (AWG) system but because this system is based on two different temperature ranges neither of which, although good enough for general purposes, is accurate enough when put up against the EU’s assisted bicycle motor testing process, which in testing for the legality of such, has set the ‘ambient’ temperature at a lowly and constant 30˚ Centigrade, Consequently, our Government who is aware of all the confusion it is causing refuses to use the term Ampacity - and has stated instead that ‘an Insulated wire has a voltage rating and a maximum conductor temperature rating it doesn’t need to have an Ampacity rating as that depends on the surrounding ambient temperature’ - consequently, when asked to furnish a simple explanation to the question above they cannot come up with an answer and cop out by pointing the enquirer (me) and anybody else that enquires to all the information to be found in such as that that is in the EN15194 and UN/ECE Regulation N0 85 legislation and that information relates to aspects of POST motor build and testing which are expensive to buy and runs into many thousands of words none of which are relevant to a PRE motor build consumer question the answer to which runs into forty four small simple words:-
It is not a reference to a Peak Power Rating.
It is a reference to a Power point (250watts) from which the (AMPACITY) wire rating used in a PRE motor build can be determined in order to conform to OHM’s Law of safe usage.

The EU governments(s) were quite aware of the power limitations of such a low rating so decided to ditch all that bumph about safety and beggar the consequences legal or otherwise and decided to up the ante and set the bar twice as high setting a maximum useable power limit to an unsafe heat generating 540 Watts. (Reference to this was later rescinded as exceeding the limit would bring failure under the 30min rule).
AND THE CONSEQUENCES ARE
The administration of Law is compromised by the hypocritical nature of the present means of rating an EAPC motor build and a EU advisory committees recommendation that future motor builds were based on the Wattage available under the EAPC Bicycle Classification and not on an Ampacity rating was turned down. It is my opinion in view of the statement above that it will not be long (due to the lack of administration of Law) before bicycles presently looked on as being illegal 350-500 Watts will providing they have been manufactured with the proper wire build to conform to OHM’s Law (like house wiring has to) and cannot exceed 25kmp/15½mph in speed will be classed as legal.
Yours Linfitter.

Saneagle:-You don’t need to see a reference to the 540watts The definition of which has to be written on every 36volt Controller ever built with a 15amp peak power draw, do the maths volts x amps.

As to the rest of my Post it is concerned wholly with ‘safety’ and its relevance in Law. I have pointed out that a motor running up to its rating of 250Watts is ‘safe’ when it exceeds this point and starts creating heat it is ‘unsafe’. Government well knows that it can create all the Laws it wants but until they have been ‘proven’ and ‘ratified’ and ‘precedents’ set in a Court of Law a Prosecution Office would be on dangerous grounds to bring before a Court a case involving a Motor the definition of which would involve a reference to the ‘unsafe’ factor of its build. No Court of Law could ratify a Law that could leave it open to litigation. Government is fully aware of this and wants to bring the EAPC Motor build within the jurisdiction of Law and Order and to give incentive to motor builders they have removed all reference to a Peak Power rating relying on Manufactures to build Motors within the range available to them under the Bicycle Class. Government is keeping their hopes on this quiet and the MofT site is still promoting the implied legal ‘unsafe’ 250watt rated motors and they are doing this purely on a ‘safety’ basis which they are always harping on about. They do not want ‘novice’ potential EAPC riders to be able to buy bikes with a more highly powered motor and without experience of power assistance be able to take them straight out of the shop and on to the road but that doesn’t mean that higher powered EAPC’s are running fowl of the Law far from it and all those trying various means to get a higher wattage motor to perform like its lower powered relation and stamp them with paper stickers stating the old legal power rating are to put it mildly wasting their time.

As Soundwave has kept iterating the Police are not bothered with what obviously looks like a higher powered machine, and now you know why, they are in fact providing they keep within the controls of the bicycle class of machine, ‘legal’ EAPC’s. There are three Laws that protect the public and they have been fully tested and put on the statute book a long time ago they are:- riding recklessly, riding dangerously and riding without due care and attention and that is why you will see and hear reference to the Police chasing speeding riders who when taken to Court are taken under these ancient laws and apart from what other penalties the Court deems appropriate to give them, will confiscate the offenders tool for offending the ‘offending’ machine.

And that is all that I have to say. I will keep reading people’s posts and hope that I no longer see questions as to why the police aren’t policing – they are.

Yours Sincerely
Linfitter.

 

[saneagle]

I have pointed out that a motor running up to its rating of 250Watts is ‘safe’ when it exceeds this point and starts creating heat it is ‘unsafe’.

That's not true at all. I know of many motors rated at 250w that are happily running at over 1000w that don't overheat in normal use. You can make any motor overheat, regardless of its rating, if you run it outside its efficient zone even at less power than whhat they're rated for, which is why motors are always under-rated.

 

[Linfitter]

That's not true at all. I know of many motors rated at 250w that are happily running at over 1000w that don't overheat in normal use. You can make any motor overheat, regardless of its rating, if you run it outside its efficient zone even at less power than whhat they're rated for, which is why motors are always under-rated.

My Bafang SWX motor windings use 25thou wire rated on the AWG chart as 6.944 amps at 20 gauge
I am replying to your post because I frequently draw on 440Watts to surmount just one of my local hills which has resulted in cooking and weakening my motors rotor magnets to such an extent that when I first got the bike I rode nearly everywhere on level 2- 3 at most where I now find I need to go to level 5 to get the same hill climbing performance. It seems to me that the motors you mention are one of the new breed high wattage motors and because there is still some confusion as to what is legal are being passed off as one of the old type.
Yours sincerely
Linfitter.

 

[saneagle]

My Bafang SWX motor windings use 25thou wire rated on the AWG chart as 6.944 amps at 20 gauge
I am replying to your post because I frequently draw on 440Watts to surmount just one of my local hills which has resulted in cooking and weakening my motors rotor magnets to such an extent that when I first got the bike I rode nearly everywhere on level 2- 3 at most where I now find I need to go to level 5 to get the same hill climbing performance. It seems to me that the motors you mention are one of the new breed high wattage motors and because there is still some confusion as to what is legal are being passed off as one of the old type.
Yours sincerely
Linfitter.

It's your battery that's knackered, not your motor.

 

[Woosh]

It's possible that linfitter has damaged his motor with overheating. What is the exact swx motor do you have linfitter?

 

[saneagle]

It's possible that linfitter has damaged his motor with overheating. What is the exact swx motor do you have linfitter?

Not very likely. The controllers always go first.

 

[soundwave]

Not very likely. The controllers always go first.

needs more power

 

[Bonzo Banana]

Why is there so much debate on how the EU ebike legislation is interpreted when other certification for other electrical items and other non-EU ebike legislation has no such debate? Just seems like no one really understands it and therefore how can it be policed when there is so little understanding. Why is a brushless motor one wattage under power tools certification but would be something completely different under EU ebike legislation if drawing the same approximate current. It's like the ebikes themselves you see some that enter the EU market at 250W restricted to 15.5mph and others that are classed illegal but in another market like the US market they could be sold as the same wattage?

Why is ebike certification so confusing when e-motorcycle certification seems easy. From what I understand the peak wattage is measured over a set period and the certification is correctly focused on the controller not the motor and how it controls power. It all seems so logical with no real debate about it. Yet you look at EU ebike certification and it just seems utter nonsense. If anything designed to be confusing and we now have a huge range of power outputs all claiming to be 250W.

Just seems now that we have left the EU it would be a good time to create much simpler more rational ebike legislation which suits the UK with its imperial MPH ratings. For example assistance to 20mph to suit urban roads and a power rating similar to EU e-motorcycles certification or maybe US ebike certification.

It's obvious there is huge confusion as you only have to look at the recent deaths on illegal e-motorcycles and how they are confused with ebikes. You wonder if good ebike legislation would have prevented these deaths because it would have been clear to everyone what is legal and there would be no grey areas.

 

[saneagle]

Why is there so much debate on how the EU ebike legislation is interpreted when other certification for other electrical items and other non-EU ebike legislation has no such debate? Just seems like no one really understands it and therefore how can it be policed when there is so little understanding. Why is a brushless motor one wattage under power tools certification but would be something completely different under EU ebike legislation if drawing the same approximate current. It's like the ebikes themselves you see some that enter the EU market at 250W restricted to 15.5mph and others that are classed illegal but in another market like the US market they could be sold as the same wattage?

Why is ebike certification so confusing when e-motorcycle certification seems easy. From what I understand the peak wattage is measured over a set period and the certification is correctly focused on the controller not the motor and how it controls power. It all seems so logical with no real debate about it. Yet you look at EU ebike certification and it just seems utter nonsense. If anything designed to be confusing and we now have a huge range of power outputs all claiming to be 250W.

Just seems now that we have left the EU it would be a good time to create much simpler more rational ebike legislation which suits the UK with its imperial MPH ratings. For example assistance to 20mph to suit urban roads and a power rating similar to EU e-motorcycles certification or maybe US ebike certification.

It's obvious there is huge confusion as you only have to look at the recent deaths on illegal e-motorcycles and how they are confused with ebikes. You wonder if good ebike legislation would have prevented these deaths because it would have been clear to everyone what is legal and there would be no grey areas.

Basically, people don't read the documents, which are very clear. Also most people don't understand how electric motors work.

The original EN15194 was written by amateurs. It even had a stupid acceleration test to determine the motor's power, which confused a lot of people. They subsequently removed it, presumably after someone realised how stupid and unrealistic it was, and how it conflicted with other parts of the document.

 

[Benjahmin]

I thought I had some sort of handle on this, but now I'm thoroughly confused. Thanks Linfitter !
My Ezee kit, bought in 2014, has no markings on the front hub. No idea what the controller rating is as there's no markings on the outer case. It'll spin to 19mph on the stand and does not cut out at 15.5mph.
Having ridden around 14k miles on it, I still have, I'm still alive and not in prison.
Seems to me that this all relies on the one thing you can't legislate for - common sense resulting in sensible behaviour.

 

[saneagle]

I thought I had some sort of handle on this, but now I'm thoroughly confused. Thanks Linfitter !
My Ezee kit, bought in 2014, has no markings on the front hub. No idea what the controller rating is as there's no markings on the outer case. It'll spin to 19mph on the stand and does not cut out at 15.5mph.
Having ridden around 14k miles on it, I still have, I'm still alive and not in prison.
Seems to me that this all relies on the one thing you can't legislate for - common sense resulting in sensible behaviour.

Any bike that's limited to 15.5mph is a 250w bike because that's how much power you need to ride that fast on a flat road.

Nobody cares about torque and how much power is used to go up hills, which is why early 250w bikes gave 40nm of torque and now they give 110nm. We all know that's three times the power, but they're still 250w bikes.

When you hit someone on your bike, the energy you impact them with is half your mass times your velocity squared. It doesn't matter how much power your bike uses to go up a hill because you will never impact with more energy than you would on the flat when your speed is restricted.

If I were the supreme ruler of the UK, there would be no power limit, but there would be strict speed limits tiered according to mass so that light bikes could go faster than pedicabs and delivery vehicles and I would allow the use of independent speed controls.

 

[Bonzo Banana]

Basically, people don't read the documents, which are very clear. Also most people don't understand how electric motors work.

The original EN15194 was written by amateurs. It even had a stupid acceleration test to determine the motor's power, which confused a lot of people. They subsequently removed it, presumably after someone realised how stupid and unrealistic it was, and how it conflicted with other parts of the document.

I must admit I don't understand the legislation. I've looked at it numerous times and read other people's interpretations of it many of which are different and I thought I had a handle on how electric motors work. I don't understand how a Bosch mid-drive motor can be pulling close to 800W going up a hill with 95Nm torque or thereabouts and be classed as 250W. I've seen so called ebike experts even that chap at ebikeschool who has written many books on the subject of ebikes and he is scratching his head when it comes to EU ebike legislation. Yet strangely I can understand other certification without issue and was a compliance officer previously for a multi-million importer dealing with EU certification for other products and had no issues with that certification. It all made sense to me. However with EU ebike certification I just don't understand how some of the products are allowed to be certified under it. I look to see how they are allowed in the certification and can't understand it.

 

[saneagle]

I must admit I don't understand the legislation. I've looked at it numerous times and read other people's interpretations of it many of which are different and I thought I had a handle on how electric motors work. I don't understand how a Bosch mid-drive motor can be pulling close to 800W going up a hill with 95Nm torque or thereabouts and be classed as 250W. I've seen so called ebike experts even that chap at ebikeschool who has written many books on the subject of ebikes and he is scratching his head when it comes to EU ebike legislation. Yet strangely I can understand other certification without issue and was a compliance officer previously for a multi-million importer dealing with EU certification for other products and had no issues with that certification. It all made sense to me. However with EU ebike certification I just don't understand how some of the products are allowed to be certified under it. I look to see how they are allowed in the certification and can't understand it.

It's because there is no maximum power specified and no regulation that prevents under-rating the motor. It's what's not in the regulations that count in this case. People make assumptions about intentions, but the law goes by what is and isn't written in the regulations.

As I said, if the drive system cuts off at 15.5 mph, it would be reasonable to rate it at 250w in the absence of specific regulations.