Same Motor, Different Power Rating

[Benjahmin]

The power rating, continuous or maximum of our cars is however unlike our e-bikes not currently embedded in its usage legality.

Exactly so.
They are also capable of going far faster than the national speed limit, but non has ever been confiscated because of the ability to do so.
My Ezee conversion in level 5 and on the stand, wil register 19mph. But that's on a cycle computer who's speed registration is dependant on wheel size setting and this is not precise. Also, if roadside tested, this would be without any resistance, so what would the actual road speed be?
As there's no legal requirement to have one, maybe we should all just remove speedo's.
'Was I speeding officer? The only way I can tell is by how much the wind is making my eyes run, it's very windy today isn't it?'

 

[Sturmey]

How is continuous rated power tested? Can it be done outside of an engineering lab?

By the way, there was a way proposed that could test and rate the output power without a lab or any special equipment. I dont think it will work with a torque sensor but will certainly work with a hub motor.
You need to take the chain off the bike and fit a pannier rack as you need to add ballast (e.g. drums of water) to bring the overall weight of bike + rider+ ballast = 150Kg.
A calm day, a marked level piece of ground and an assistant with a stop watch is all else that is needed.
The calculation/formulae is based on applying good old Newton's physics to a short standing start. It averages the power over a range of speeds.
Take note that the instantaneous peak power is never measured in all these tests. This is because the power output curve of a motor is considered as 'parabolic' shaped ((EN15194) and some means has to be used to apply a 'mean' or average value.
This is common with electrical measurements. For example, the UK main voltage has a maximum instantaneous peak value of about 320V. However, this higher peak value is found not to be useful so they came up with the idea of using the notional Root Mean Square value which comes to 230V, which give the mains AC voltage the equivalent DC heating value (or something like that). i.e actual 320V peak = notional 230V rms.

 

[Benjahmin]

Brilliant ! Not many unquantafiable variables in there !
For every day use, the power of the motor is what the sticker says it is.
Buy a resonably sized geared hub and put on a label that says ' 250w' and 'Hoofrungdung Motor Corp' on it and enjoy it, 'cos the only thing practically measureable is the speed.
If mid drives are your thing then who knows? Where is the power measured. At the crank, at the wheel? What gear's it in? How much is attributable to the rider? What's the frontal surface area of the rider? Where does half the moon go twice a month?
Think I'm goin' out on my bike now

 

[Sturmey]

...... How much is attributable to the rider? ......

I specifically said above that 'You need to take the chain off the bike'. This solves that problem.

 

[Benjahmin]

Sturmey, mate, take the chain off a mid drive and the level piece of ground and stop watch aren't gonna be much use .
Buy a believable motor and sticker it accordingly.
Here's one I did earlier. Take out the bleedin obvious, put in the 'yeh, I can believe that'

https://www.pedelecs.co.uk/forum/attachments/dscf3353-jpg.53861/

 

[saneagle]

I dont think it will work with a torque sensor but will certainly work with a hub motor.

How will the hub-motor give power without a control system? Which control system are you going to use for that test?

that test you linked to was dropped because it's ridiculous - probably written by a student with an O-level in physics, but never rode an electric bike nor figured out how they work, or had a go on Seago at a caravan show and thought they were all like that.

 

[flecc]

To me, the most sensible solution would be to make it more simple: just a 15 mph powered speed limit, everything else allowed.

When the whole European Parliament debated this only a few years ago, that is exactly the conclusion they reached and recommended to the EU Commission.

But the 28 member commission, one from each country, and all retired politicians from those countries put out to pasture, rejected it. So much for democracy.

In France, you can drive a 45 km/hr quadricycle without a licence at 14 years old! They don't care.

Not with those. But they do seem to have a downer on two wheels:

A driving licence, minimum AM group, is needed for up to 50cc Mopeds.

To ride a 125cc scooter, you have to have an “A1” license. To get this license, you need to have passed your theory and practical test, and have a minimum of 20 hours’ driving, or seven hours if you’ve held a B license for at least two years.

Paris have totally banned e-scooters.

And the new penalties for infringing the pedelec (EPAC) regulations are savage. Fines up to 30,000 euros and imprisonment.

Their one bit of relief for powered two wheelers is that anyone born before 1988 can ride any moped without a licence.
.

 

[Sturmey]

How will the hub-motor give power without a control system? Which control system are you going to use for that test?

that test you linked to was dropped because it's ridiculous - probably written by a student with an O-level in physics, but never rode an electric bike nor figured out how they work, or had a go on Seago at a caravan show and thought they were all like that.

The second alternative test proposed is different than the first test. The first test only rates the bare motor at the shaft and is a thermal test. The second test is not a thermal test and tests the whole bike along with its controller, battery etc. It estimates the power by calculating the kinetic energy/momentum gained by the total 150KG mass (the energy must come via the motor) and dividing this by the time. (power = energy/time). Its not an unreasonable test and the results allows the use of high peak powers which surely favour the user. I presume either test will do as long as the manufacturer succeeds in passing it and gets the bike approved. Do we want tougher tests and more restrictions? More expensive bikes?
But I can only say the position as it was. I am unable to get up to date documents because they are too expensive. There may be newer tests. I dont know.
But my overall point is to defend the position that its not unreasonable for a 250W continuous rated motors to have much higher peak powers when all factors, (including how tests were done, efficiency, difference between electrical and mechanical watts, allowance for errors etc) are taking into account. I do not think there is any conspiracy so to speak.

 

[Ocsid]

Are we not all stymied in any attempt to measure the power here by that additional word "continuous" ?

Only the maker can laydown what they deem "continuous" for their product, its a way different thing to peak power, which can readily be checked as long as its point of measurement is laid down.

Many things determine how as designers we might determine what we credit to be our products "continuous" rating. In engineering it can be used having far from the same meaning as "continuous", it could be limited as continuous for "X" hours in 24. It could vary with differing product "life" values", "mean time between failure" offers, and certainly varies with such things as ambient temperature.

As a "legal" definition, unless way more specified than has so far been aired here, it is about as dumb a definitive definition as legislators could dream up, but must be viewed as a dream come true to the motor makers. Much as we see.

 

[saneagle]

Are we not all stymied in any attempt to measure the power here by that additional word "continuous" ?

Only the maker can laydown what they deem "continuous" for their product, its a way different thing to peak power, which can readily be checked as long as its point of measurement is laid down.

Many things determine how as designers we might determine what we credit to be our products "continuous" rating. In engineering it can be used having far from the same meaning as "continuous", it could be limited as continuous for "X" hours in 24. It could vary with differing product "life" values", "mean time between failure" offers, and certainly varies with such things as ambient temperature.

As a "legal" definition, unless way more specified than has so far been aired here, it is about as dumb a definitive definition as legislators could dream up, but must be viewed as a dream come true to the motor makers. Much as we see.

It's the word "rated" that people are getting confused about. They don't seem to be able to read it, like it disappears of the page. It has an exact meaning and is easy to understand. Even our government missed it when they wrote the rules on their website. It must be some sort of mystical word that only the "seers" can see. I feel special.

 

[Ocsid]

"Rating!, I have no trouble understanding what rating means, I though am unaware what the specification details, the motors here are rated against.
Can we know all these parameters and conditions, please?

 

[saneagle]

"Rating!, I have no trouble understanding what rating means, I though am unaware what the specification details, the motors here are rated against.
Can we know all these parameters and conditions, please?

The rated power is the power that the engineer decides it can do without breaking.

 

[Sturmey]

I found a copy of a recent ebike 50 page EN15194 test report. The relevant section of the report on power is as below. The engineer/tester just fills in the letter 'P' (for pass).

 

[saneagle]

That's right. The test for rated power is written in EN600034. The result would be pass or fail - overheats or doesn't.

 

[Benjahmin]

So, EN600034 is a pass or fail. Ergo a motor that does not overheat at 800w will certainly not overheat at 250w and, therefore it would seem, can quite legitimately be labelled as 250w (if that's what the duristriction demands). As it's the label that the authorities will look at, that's the important bit - ain't it?
What power is supplied by the controller/battery combo is a seperate issue, not regulated at all.

So 250w label. Speed limited to 15.5mph. Yer good to go.

 

[Woosh]

You can see why I don't want to sell components on their own due to their potential misuse. I am often asked: can you sell me a 48v 10ah bag battery for my BBSHD or for my 1000W front hub kit? can you sell me an Aikema 85SX for my 48V KT system? or a TSDZ2B to run at 52V. The 13S2P bag battery may overheat, the 85SX may have its plastic wheels melted, the TSDZ2B would demagnetise after a few hours.

 

[Sturmey]

So, EN600034 is a pass or fail. Ergo a motor that does not overheat at 800w will certainly not overheat at 250w and, therefore it would seem, can quite legitimately be labelled as 250w (if that's what the duristriction demands). As it's the label that the authorities will look at, that's the important bit - ain't it?
What power is supplied by the controller/battery combo is a seperate issue, not regulated at all.

So 250w label. Speed limited to 15.5mph. Yer good to go.

I'm not sure if that's the case. If you read the report, what the examiner has passed is that 'The maximum continuous rated power: 250W'
It is possible that the same motor would pass say a separate 350W (or possibly more) test for a different market/juristriction/speed limit under a different set of conditions (e.g voltage/rpm/load etc) and I think that could be the case. After all, different countries have different rules/speeds/power limits and many kit motors such as the TSDZ2 are designed to be universal and are sold worldwide into different countries with different power limits.
Bye the way. I hope I am not being annoying here. I am trying to look for answers that can be verified on paper/documents rather than completely accepting hearsay opinion. I would like to see a paper trail so to speak. Am I unreasonable?

 

[Az.]

I hope I am not being annoying here.

Not at all. You are most welcome.

After all your comments are far more appropriate on this forum than discussion about... cats.

 

[Benjahmin]

I'm not sure if that's the case. If you read the report, what the examiner has passed is that 'The maximum continuous rated power: 250W'
It is possible that the same motor would pass say a separate 350W (or possibly more) test for a different market/juristriction/speed limit under a different set of conditions (e.g voltage/rpm/load etc) and I think that could be the case. After all, different countries have different rules/speeds/power limits and many kit motors such as the TSDZ2 are designed to be universal and are sold worldwide into different countries with different power limits.
Bye the way. I hope I am not being annoying here. I am trying to look for answers that can be verified on paper/documents rather than completely accepting hearsay opinion. I would like to see a paper trail so to speak. Am I unreasonable?

I'm not sure your average copper, at a roadside stop, is going to be looking for a paper trail. What I'm interested in is not getting my bike taken away by some pedantic jobsworth and it seems some judiscious labelling will achieve that.
As to maximum continuous rated power, if the motor does not overheat with a maximum of 250w supplied to it - then it's passed. All engineering has safety tolerances built into it. (As an example I used to be a lift engineer. Each passenger lift has 4 suspension cables and each single cable is capable of taking 4 times the safe working load of the car.) So a motor will have 'headroom' in it. So what should be done? Maybe test it, with increasing wattage, until it does overheat then take off 10% from the wattage and call that the maximum?
What I'm driving at is that this test is merely looking for the absence of overheating. If I apply a maximum of 250w to that motor and it stays cool, it's passed. Even if it warms up abit, at 250, it will still take more to make it overheat - so what's the maximum?
So a motor does not have a wattage rating as such, I suppose it has a wattage tolerance. Increase the cooling efficiency and that tolerance increases. So again, what's the maximum?
This regulation would have more definition if controller maximum current was controlled. However those that wanted to bypass the reg would just change the label on the controller making it necesary for police to carry ampmeters as well as tazers.
Perhaps we're better off just muddling along

 

[Sturmey]

........As to maximum continuous rated power, if the motor does not overheat with a maximum of 250w supplied to it - then it's passed. ......... If I apply a maximum of 250w to that motor and it stays cool, it's passed.

I think its the other way around. A motor running at its rated value of 250W will be close to its specified maximum temperature or for the temperature class it falls into( if this is applicable). If its running cool at 250W its over rated capable of more. Ideally for the test, it should run close to its specified maximum temperature because its the safe maximum continuous power figure we are looking for.
I think where the leeway is in the selection of the safe temperature e.g. The motor might be capable of a higher temperature than the manufacturer specifies. These things are not exact.
This for me is all by the way of a technical discussion. I will let someone else discuss with your legal questions as regard been stopped by the police etc. As you say, just muddle along

PS Mistake corrected.