Legality of power ratings

[flecc]

I may be quite wrong, but I get the impression that it is in fact the controller, not the motor that is important.
A controller set to deliver no more than 7 amps at 36 volts will allow the motor to develop 252 watts.
Up the amps and the wattage goes up.
There is no such thing as a 250 watt motor, simply a motor that will not burn out if run at 250 watts indefinitely.

Which is why the EN15194 specified power tests are only for complete pedelecs, not just motors.
.

 

[anotherkiwi]

And the only real problem with controllers is that they are not user tamper proof as per EN 15194.

When it comes to kits the only ones not playing the game are the people selling the kits. It is so damned easy to spec a kit for the European market - set the controller for one rim size and remove all posibility for the user to access the setup screens. Remove the throttle from the box and don't change the kit price would cover the cost of the above.

 

[Deleted member 4366]

I may be quite wrong, but I get the impression that it is in fact the controller, not the motor that is important.
A controller set to deliver no more than 7 amps at 36 volts will allow the motor to develop 252 watts.
Up the amps and the wattage goes up.
There is no such thing as a 250 watt motor, simply a motor that will not burn out if run at 250 watts indefinitely.

You have the right idea, but it's much more complicated than that. You should be considering output power, which will be a lot less than what the controller allows.

Consider a typical 20 mph hub-motor with a 15A controller. The motor generates a back voltage as soon as it starts turning. At maximum rpm (20 mph), the back voltage is equal to the battery voltage, so no current can flow, even though the controller would allow 15 amps. You'd have to slow the motor down to something like 10 mph before you can get enough voltage difference to get 15A from the controller, but at that speed, efficiency is only about 60% is only giving about 320w of output power. Any slower and the efficiency goes right down, so you'll struggle to get 250w out of your motor when hill-climbing.

Once you get over 10mph, your efficiency starts to rise, but your current is ramping down because the net voltage is decreasing. You might only get 8 amps at 15 mph where the efficiency would be at its 80% maximum, so that's 36mx 8 x 0.8 = 230w output power.

If you were to measure continuous power, at what speed would you measure it? The power output is zero at zero speed. It ramps up to a macimum at about 50% to 70% of maximum rpm, then it ramps back down to zero at maximum speed. If you averaged it over the whole rpm range, it would be about half the maximum.

There's no test for maximum continuous rated power output because of all these factors. All the tests are to prove that the motor hasn't been over-rated, so they run it at the rated power continuously and check that it doesn't overheat.

These calculations are even more complicated with a crank-drive motor. It behaves the same as a hub-motor, but instead of the current and efficiency being related to bike speed, they're related to cadence.

 

[jonathan75]

The law isn't being flouted. People are trying to interpret in in the way they think it's written, not the way it's actually written. It allows any motor that's rated at 250w continuous output. The three key words are "rated", "continuous" and "output".

If a Bafang engineer or any other person authorised and qualified to give a motor a rating decides to rate a motor at 250w continuous output for whatever reason, then it's allowed. Noone has to flout the law.

I defer to you in all matters to do with engineering but everything you've said just doesn't hold, without reference to the precise wording of the legislation.
All I'm getting on this page is hearsay.

If you're right that rated, continuous, and output are the words used, then you're correct - but only partly.

Only as a matter of practice, seemingly, does 'rated' for pedelecs mean in law 'rated by any method', and for pragmatic reasons: if 'rated' were to mean, as flecc implies, 'rated by a justifiable method', then the consequence would be the destruction of the ebike industry, because people wouldn't want the puny bikes which would be all that were permitted. But the meaning of the word 'rated' will not be tested in court because all the bureaucratic parties are too sensible for that.

 

[shemozzle999]

I'm in the process of considering an e-bike conversion & have been reading up as much as I can. I came across the thread from 2012 discussing the UK law & power ratings of motors.
I'm no expert but I think some are confusing the power rating of the motor with power consumption. Someone said that their 250 watt rated motor was reading 620 watts on the 'Cycle Analyst' display when they were going up hill using maximum power setting. As I understand it (40 years after leaving school where I should have learnt it!) the 620 on the readout was the consumption rate of the available power. A 36 volt X 10Ah battery = 360 watt hours of available energy so a reading of 620 indicates that that level of power consumption could be available for just 35 minutes. Remember there is a huge difference between maintaining a steady slow speed on the level, and climbing a hill quickly - try doing it without a bike! As a sufferer of ME / post viral fatigue I'm very aware that the weaker you are, the more noticeable the difference in energy requirement is between say, level walking & uphill running. The same applies to motors; a low voltage motor may not be able to drive up more than a gentle gradient but be capable of sustaining some distance on the level - think mobility scooters and vintage cars. A powerful modern car might be capable of spectacular acceleration and pulling power but it will not go further because it uses up more of its stored energy in the fuel tank.

As of 1st January 2016 REGULATION (EU) No 168/2013 states an EAPC as being exempt if under article 2 :

(h)

pedal cycles with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of less than or equal to 250 W, where the output of the motor is cut off when the cyclist stops pedaling and is otherwise progressively reduced and finally cut off before the vehicle speed reaches 25 km/h;

and defines maximum continuous rated power under article 3 as:

(35)

‘maximum continuous rated power’ means the maximum thirty minutes power at the output shaft of an electric engine as set out in UNECE regulation No 85;

UNECE regulation No 85 states:

5.3. Description of tests for measuring the net power and the maximum 30
minutes power of electric drive trains
The electric drive train shall be equipped as specified in Annex 6 to this
Regulation. The electric drive train shall be supplied from a DC voltage
source with a maximum voltage drop of 5 per cent depending on time and
current (periods of less than 10 seconds excluded). The supply voltage of the
test shall be given by the vehicle manufacturer.
Note: If the battery limits the maximum 30 minutes power, the maximum
30 minutes power of an electric vehicle can be less than the maximum
30 minutes power of the drive train of the vehicle according to this test.

5.3.1. Determination of the net power
5.3.1.1. The motor and its entire equipment assembly must be conditioned at a temperature of 25 °C ± 5 °C for a minimum of two hours.
5.3.1.2. The net power test shall consist of a run at full setting of the power controller.
5.3.1.3. Just before beginning the test, the motor shall be run on the bench for three
minutes delivering a power equal to 80 per cent of the maximum power at the
speed recommended by the manufacturer.
5.3.1.4. Measurements shall be taken at a sufficient number of motor speeds to define
correctly the power curve between zero and the highest motor speed
recommended by the manufacturer. The whole test shall be completed within
5 minutes.

5.3.2. Determination of the maximum 30 minutes power EN L 323/58 Official Journal of the European Union 7.11.2014
5.3.2.1. The motor and its entire equipment assembly must be conditioned at a temperature of 25 °C ± 5 °C for a minimum of four hours.
5.3.2.2. The electric drive train shall run at the bench at a power which is the best estimate of the manufacturer for the maximum 30 minutes power. The speed must be in a speed range, which the net power is greater than 90 per cent of the maximum power as measured in paragraph 5.3.1. This speed shall be recommended by the manufacturer.
5.3.2.3. Speed and power shall be recorded. The power must be in a range of ± 5 per cent of the power value at the start of the test. The maximum 30 minutes power is the average of the power within the 30 minutes period.


Edit: additional text for net power added

 

[Deleted member 4366]

We need 5.3.1, which is maximum power measurement.

 

[shemozzle999]

We need 5.3.1, which is maximum power measurement.

post #25 edited

 

[Deleted member 4366]

OK, I think I have it now. I'll try and put it in English.

5.3.1 The test is to determine the power curve by turning everything up to maximum and recording the power at different motor speeds.

The important thing from this test is the speed at which the power is within 90% of the maximum because the 30 minute test must be done in that speed range. This is to make sure that the next test isn't done in an inefficient range, which would cause it to fail the next test.

5.3.2 The 30 minute test is done at the power that is the best estimate of the 30 minute power from the manufacturer. "Best estimate" means rated power, so, if the manufacturer rates his motor at 250w, which is their best estimate of 30 minute power, that's the power to use for the test. The motor then has to be run at that power (250w) for 30 minutes. It is therefore a test to prevent over-rating, not under-rating.

 

[oldtom]

5.3.1 The test is to determine the power curve by turning everything up to maximum and recording the power at different motor speeds.

The important thing from this test is the speed at which the power is within 90% of the maximum because the 30 minute test must be done in that speed range. This is to make sure that the next test isn't done in an inefficient range, which would cause it to fail the next test.

5.3.2 The 30 minute test is done at the power that is the best estimate of the 30 minute power from the manufacturer. "Best estimate" means rated power, so, if the manufacturer rates his motor at 250w, which is their best estimate of 30 minute power, that's the power to use for the test. The motor then has to be run at that power (250w) for 30 minutes. It is therefore a test to prevent over-rating, not under-rating.

I haven't quite grasped the point of this, (these) procedure(s), I'm afraid.

At which point or points, could a motor (or the whole electrical system) fail the test procedure? Would a 180w rated motor be just as ok as a 250w example? If so, how does a higher-rated motor, such as 350w or 500w, fail the test?.....or does it?

If a rating plate states 250w but performs exactly as a 500w motor, what is the point of the test? Sorry but my understanding of electrical engineering is pretty rudimentary though I'm pretty good with hammers and big spanners.

Tom

 

[mike killay]

I haven't quite grasped the point of this, (these) procedure(s), I'm afraid.

At which point or points, could a motor (or the whole electrical system) fail the test procedure? Would a 180w rated motor be just as ok as a 250w example? If so, how does a higher-rated motor, such as 350w or 500w, fail the test?.....or does it?

If a rating plate states 250w but performs exactly as a 500w motor, what is the point of the test? Sorry but my understanding of electrical engineering is pretty rudimentary though I'm pretty good with hammers and big spanners.

Tom

From what I can see of those tests, then yes you are right.
All systems need a safe working load and it would be daft to fit a motor that performed at 250 watts but burned out at 251 watts.
We know that the motors supplied by the Chinese have different markings to satisfy the various legislative demands of different countries.
We know that many bikes have to be fitted with some sort of speed sensor to cut the motor at 15 mph.
So, it must be all down to the controller.
For instance, there is an Australian outfit offering a 48 volt conversion for the 36 volt Tonaro, just a new battery and controller.(They do offer a bigger chain ring etc. if you want to go faster)

 

[shemozzle999]

I haven't quite grasped the point of this, (these) procedure(s), I'm afraid.

At which point or points, could a motor (or the whole electrical system) fail the test procedure? Would a 180w rated motor be just as ok as a 250w example? If so, how does a higher-rated motor, such as 350w or 500w, fail the test?.....or does it?

If a rating plate states 250w but performs exactly as a 500w motor, what is the point of the test? Sorry but my understanding of electrical engineering is pretty rudimentary though I'm pretty good with hammers and big spanners.

Tom

For a full understanding click the link below for a list of the regulations, it will open up a pdf - scroll down to no.85 then select the English translation by clicking on "EN" this will open another pdf of the complete regulation:

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0CCEQFjAA&url=http://ec.europa.eu/enterprise/sectors/automotive/files/unece/status-table_en.pdf&ei=YX6KVcWPHcqXsgHs5bP4BA&usg=AFQjCNE8fKwNfbNcU7fQaaooynNTMN2Lnw&bvm=bv.96440147,bs.1,d.ZGU

 

[Deleted member 4366]

To pass the test, the motor must be able to run at the rated power (estimate of 30 minute test) without going over temperature or failing in some other way, so yes, a 350w. 500w or 1000w motor rated by the manufacturer at 250w would pass.

The fail criterea are not detailed in the previous posts. I'm assuming that they're the same as in the EN standard for motor testing, which is referred to in my copy of EN15194.

 

[anotherkiwi]

EN 15194 is there to protect industrial interests, the day that the EU decides they want no more Chinese kits on the road they will pull the trigger. OK that is a little harsh we know it is there to protect the consumer, the EU loves you!

"Pedelec manufacturers can issue of Declaration of Conformity (DoC) attesting to their products’ compliance with the applicable requirements. Actual proof of compliance is usually determined by testing conducted by an independent testing laboratory. However, self-testing is also permitted if a manufacturer is equipped to conduct the required testing. In either case, a formal test report is required to document compliance in support of the DoC."

1. the frame must be visibly and permanently marked with a serial number at a readily visible location;
2. the frame must be visibly and durably marked, with the name of the manufacturer or the manufacturer’s representative and the number of European Standard, i.e. EN 14764
3. the vehicle must be durably marked with the following words: EPAC standard according to EN 15194
4. xx km/h, i.e. cut off speed
5. xx W, i.e. electric motor maximum continuous rated power

Declare yourself as the manufacturer of the EPAC, the bike manufacturer has done his bit for your host bike. Write a DoC for your kit equipped bike. Do a formal test (ride it to the shops and see if it is too warm when you get back). Print a sticker. You will be held responsible for your declaration of conformity to EN 15194 if something goes wrong i.e. running over little old ladies or children on pedestrian crossings is probably not a good idea...

Don't mount the throttle, use hydraulic brakes, buy good tyres, set top speed to 27 kph in the controller, don't break too many road code rules and live happy.

 

[oldtom]

To pass the test, the motor must be able to run at the rated power (estimate of 30 minute test) without going over temperature or failing in some other way, so yes, a 350w. 500w or 1000w motor rated by the manufacturer at 250w would pass.

The fail criterea are not detailed in the previous posts. I'm assuming that they're the same as in the EN standard for motor testing, which is referred to in my copy of EN15194.

Cheers for that Dave!

I have to ask then, what may be a very stupid question: What is it therefore that makes some bikes illegal? Is it only if an attached plate describes the motor as 350w or indeed any number bigger than 250w that it becomes non-compliant?

I understand about maximum permitted road speed but this system of testing motor power output doesn't seem to answer the question most people probably ask? If we consider, just by way of one example of a description of motor output, the well-known kitchen blender from the USA sold in some of our expensive stores for a lot of money, is described as having a 1hp motor. In some ads, I have seen various models described as being 1hp, 1.5hp and even 2hp.

A number of our well-know EAPCs have felt to me on test-riding them, that they have so much more grunt than some of the competition that they are probably non-compliant, only legal in as far as the fixed plate or other marking describes them as 250w and the fact that they are electronically limited to 25kph....ish.

In my ignorance, it all seems a bit pointless to me, especially as plod would be unable to make any determination as to legality without the assistance of techies in a lab with the requisite measuring equipment. That being the case, wouldn't a straightforward absolute maximum of 'X' power produced by a motor be much more easily understood? It would seem to me that maximum output would be an easier thing to test.

Tom

 

[Deleted member 4366]

You're right about everything except the bit about motors having more grunt as being non-compliant, which contradicts what you said at the beginning. If the manufacturer rates the motor at 250w, it's compliant, regardless of how much grunt it has.

 

[flecc]

In my ignorance, it all seems a bit pointless to me, especially as plod would be unable to make any determination as to legality without the assistance of techies in a lab with the requisite measuring equipment. That being the case, wouldn't a straightforward absolute maximum of 'X' power produced by a motor be much more easily understood? It would seem to me that maximum output would be an easier thing to test.

Tom

The best bit of commonsense on this issue came from the EU parliament early last year. Having considered the issue, they proposed a removal of all power limits, leaving legal control as being just the maximum assist speed while leaving the power required to designers.

Sadly the EU Commission rejected that.
.

 

[Deleted member 4366]

At the moment, nobody needs to do anything. I can't see why anybody shouldn't be happy with what we've got. It means that everybody can get a bike with the torque that they need or want.

It seems to me that some people got in their heads from somewhere that 250w was a maximum power output, and that any motor that produces more power than that is somehow cheating. There has never been a limit on maximum power output. Even when it was 200w, it was still continuous rated power, which does not mean and never has meant maximum power.
If the legislators had really wanted to tie down maximum power, they could easily have done so by limiting maximum current from the battery at certain voltages, but they didn't. Instead, they said "nominal maximum continuous rated power", which is what we have to comply with. We don't have to worry about how the motor was rated. A label, certificate or test report from the manufacturer is sufficient.

BTW, the word "nominal" is another key word. It doesn't mean "actual".

 

[1boris]

You have the right idea, but it's much more complicated than that. You should be considering output power, which will be a lot less than what the controller allows.

Consider a typical 20 mph hub-motor with a 15A controller. The motor generates a back voltage as soon as it starts turning. At maximum rpm (20 mph), the back voltage is equal to the battery voltage, so no current can flow, even though the controller would allow 15 amps. You'd have to slow the motor down to something like 10 mph before you can get enough voltage difference to get 15A from the controller, but at that speed, efficiency is only about 60% is only giving about 320w of output power. Any slower and the efficiency goes right down, so you'll struggle to get 250w out of your motor when hill-climbing.

Once you get over 10mph, your efficiency starts to rise, but your current is ramping down because the net voltage is decreasing. You might only get 8 amps at 15 mph where the efficiency would be at its 80% maximum, so that's 36mx 8 x 0.8 = 230w output power.

If you were to measure continuous power, at what speed would you measure it? The power output is zero at zero speed. It ramps up to a macimum at about 50% to 70% of maximum rpm, then it ramps back down to zero at maximum speed. If you averaged it over the whole rpm range, it would be about half the maximum.

There's no test for maximum continuous rated power output because of all these factors. All the tests are to prove that the motor hasn't been over-rated, so they run it at the rated power continuously and check that it doesn't overheat.

These calculations are even more complicated with a crank-drive motor. It behaves the same as a hub-motor, but instead of the current and efficiency being related to bike speed, they're related to cadence.

Thanks,Very nice explaination

 

[shemozzle999]

OK, I think I have it now. I'll try and put it in English.

5.3.1 The test is to determine the power curve by turning everything up to maximum and recording the power at different motor speeds.

The important thing from this test is the speed at which the power is within 90% of the maximum because the 30 minute test must be done in that speed range. This is to make sure that the next test isn't done in an inefficient range, which would cause it to fail the next test.

5.3.2 The 30 minute test is done at the power that is the best estimate of the 30 minute power from the manufacturer. "Best estimate" means rated power, so, if the manufacturer rates his motor at 250w, which is their best estimate of 30 minute power, that's the power to use for the test. The motor then has to be run at that power (250w) for 30 minutes. It is therefore a test to prevent over-rating, not under-rating.

ANNEX 7
CHECKS ON CONFORMITY OF PRODUCTION
1. GENERAL
These requirements are consistent with tests to be held to check conformity of production, according to paragraph 6 and its subparagraphs.

2. TEST PROCEDURES
The methods of testing and measuring instruments shall be those described in Annexes 5 or 6 to this Regulation.

3. COLLECTION OF SAMPLES
One drive train has to be chosen. If after the test of paragraph 5.1 below, the drive train is not considered as conforming to the requirements of this Regulation, two more drive trains have to be tested.

4. MEASUREMENT CRITERIA

4.1. Net power of internal combustion engine
During the tests to verify conformity of production, the power shall be measured at two engine speeds S1 and S2, corresponding respectively to the measurement points of maximum power and maximum torque accepted for type approval. At these two engine speeds, which are subject to a tolerance of ± 5 per cent, the net power measured at least one point within the ranges S1 ± 5 per cent and S2 ± 5 per cent shall not differ by more than ± 5 per cent from the approval figure.

4.2. Net power and maximum 30 minutes power of electric drive trains
During the tests to verify conformity of production the power shall be measured at motor speed S1 corresponding to the measurement point of maximum power accepted for type approval. At this speed, the net power shall not differ by more than ± 5 per cent from the approval figure.

5. EVALUATION OF RESULTS

5.1. If the net power and the maximum 30 minutes power of the drive train tested pursuant to paragraph 2 above fulfils the requirement of paragraph 4 above, the production is considered to conform to the type approval.

5.2. If the requirements of paragraph 4 above are not fulfilled, two more drive trains are tested in the same way.

5.3. If the net power figure or the maximum 30 minutes power of the second and/or third drive train of paragraph 5.2 above does not fulfil the requirements of paragraph 4 above, the production shall be considered not to conform to the requirements of this Regulation and the provisions of paragraph 7.1 of this Regulation shall be put into effect.

 

[shemozzle999]

As explained by flecc, the testing is carried out on the whole drive chain i.e. the entire electric system not just the motor if it passes then the system is type approved, any modifications to the system after testing would render it as non-compliant. As seen above random testing of production units can be required at any time to confirm that the type approval testing is being maintained through production cycles