THE NEW PERFORMANCE CX RACE, FOR EBIKE RACING

[Bonzo Banana]

From what I've read Bosch 250W controllers are 20A (or @soundwave 's is), therefore I wonder if Bosch are using some sort of buffer to increase and sustain higher power for longer periods of time? Some electric and hybrid supercars boost performance for short bursts using supercapacitors. Otherwise the power of Bosch ebike motors stated on this thread make no sense.

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Calculate amps, hp and kVA for electrical motors.

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20A at 36V is 720W, but from what I've read on other forums some Bosch motors have been measured at 22A current draw despite being 250W nominal rated power, that is likely peak power for short periods. When you look around at nominal vs maximum rated power its normally approximately a double difference for most motors i.e. 250W would allow for a peak of 500W for short periods perhaps 600W for a few seconds just as a momentary surge. However for a Bosch motor used off-road climbing a steep incline or hill the motor is operating perhaps at 800W for quite some time. I'd be interested to see how Bosch calculate their 250W rating, their mathematics and why can't other manufacturers use the same formula?

As I said before a direct drive hub motor has no internal gearing and a larger surface area so heats more slowly so even if rated to 250W nominal maybe able to maintain 500W for longer as the heat build up is slower before it would have to thermally throttle itself.

Looking at that standard posted elsewhere they show a power curve diagram with 250W shown and the curve only peaks at around 300-325W looking at that diagram. That standard is incredibly vague though with regard power rating of motors it refers to another standard on how motors are rated 60034-1:2022.

 

[Bonzo Banana]

Power (Watts) = Torque (N.m) x Speed (RPM) / 9.5488

If you read, for example EN15194, its the mechanical output power that measured under certain conditions. (Its rather complicated).

Looking at that standard there are test procedures about how the motor functions with regard pedalling and applying power but that is not the electrical characteristics as far as I can see. Elsewhere they state maximum 48V system and refer to 60034-1 for how motor ratings are calculated which is purely focused on electrical motor ratings. That standard I guess would give clear indication of how the nominal power of a motor should be rated. The formula you give above looks like a watt rating for a human rider and how its calculated.

 

[Zlatan]

Here we go down the rabbit hole of definitions.
As I understand it the 250w rating of motors is what that motor can take continuously without overheating.
So, a motor that can run at 800w that doesn't hot complies with this 250w rating. Then, if stamped by the manufacturer as 250w, it is legal.
This is what makes the nominal power definition bonkers - as far as i can see, it's meaningless.

It is power that does the work. Would a more precise way be to limit the power output of contollers? Not current as a 10A controller at 36v outputs less power than a 10A at 48v.
However, if controllers were limited to an output of 250w, given inefficiencies in the system, I certainly would no longer be cycling the hills of west Wales.

I do agree about Bosch though. I wouldn't go near their locked in products.

I don't think it would at all. (if Ltd to 250w be useless on your hills)
I have a power meter built into my Giant Fathom and agreed it does occasionally see well above 250 w (most I, ve see n is 607 w) but that is when I, m going almost bonkers, spinning crank at 110 rpm on steep prolonged hills. (in Derbyshire) If I take it steady and keep cadence around 70,I can easily (steadily) climb any hill and power reading stays below 250.
And, I, d guess I, m amongst heavier riders at 105kg and certainly not fit taking my AF into account.
Look at it from your battery's point of view. I get over 2 hours hard riding even on my 400 wh battery. That's well under 250 w average. I, ll up load some power /cadence graphs... It actually amazes me how much help even 200w actually gives.
I think current rules /legislation is fine. My pedelec legal mtbs do fantastic job. All of them.


That 283 w max corresponded to a cadence of 103..You can see from graph nearly all climbing is done well under the 250 w threshold.

 

[Sturmey]

Looking at that standard there are test procedures about how the motor functions with regard pedalling and applying power but that is not the electrical characteristics as far as I can see. Elsewhere they state maximum 48V system and refer to 60034-1 for how motor ratings are calculated which is purely focused on electrical motor ratings. That standard I guess would give clear indication of how the nominal power of a motor should be rated. The formula you give above looks like a watt rating for a human rider and how its calculated.

The German forum has more info on same. The 48v max is to reduce electrocution risk. Its always mechanic power thats measured. There is no actual direct limit on maximum power. I have translated for your convenience. This I presume is the European standard. I'm not sure how much of it is applicable to England.

e-motor:nenndauerleistung [Wiki Pedelec-Forum]

www.pedelecforum.de

1. Maximum rated continuous power
1.1. definition
The "maximum rated continuous power" relevant for pedelecs is defined as follows in Article 3 No. 35 of European Regulation No. 168/2013 on the approval and market surveillance of two-wheel, three-wheel and four-wheel vehicles of January 15 , 2013, valid from January 1, 2016:

• For the purposes of this Regulation […] the expression […] “maximum rated continuous power” means the maximum power over 30 minutes at the output shaft of an electric motor as defined in UN-ECE Regulation No 85; ...

1.2. Measurement
UN-ECE regulation no. 85 as far as relevant for pedelecs: PDF version
- Clause 2.3. (to be measured is the mechanical power):

• "Useful power" is the power that is determined on a test stand on the crankshaft or a corresponding component at a corresponding engine speed

- Clause 2.4. (the rated continuous power is defined):

• "Maximum 30-minute power" is the maximum useful power of an electric propulsion system at DC voltage, as defined in paragraph 5.3.1., that a propulsion system can deliver over a period of 30 minutes on average.

- Clause 5.3. Description of tests to measure net power and maximum 30-minute power of electric propulsion systems

• The electrical drive system must be equipped in accordance with Annex 6. ...

- Clause 5.3.2. Determination of the highest 30-minute effort

• 5.3.2.1. The engine and all its equipment shall be conditioned for at least four hours at a temperature of 25 ± 5 °C.
• 5.3.2.2. The electric propulsion system must be operated on the test bench at a power level which, according to the manufacturer's specifications, most closely corresponds to the maximum 30-minute power level. The speed shall be in a range where the net power is more than 90% of the maximum power measured in accordance with paragraph 5.3.1. This speed must have been recommended by the manufacturer.
• 5.3.2.3. Power and speed are to be recorded. The power shall be within ± 5% of the power value at the start of the test. The 30-minute peak performance is the average performance over the 30-minute period.

- APPENDIX 6 METHODS OF MEASUREMENT OF NETWORK POWER AND PEAK 30 MINUTE POWER OF ELECTRIC PROPULSION SYSTEMS (here the critical thermal component is now defined):

• 2.5.4. … For air-cooled drive systems, the temperature must be maintained at a point specified by the manufacturer to within + 0/- 20 K of the maximum value specified by the manufacturer. ...
• 2.5.6. If necessary, an auxiliary cooling system may be used to maintain the temperature within the limits given in paragraphs 2.5.4 and 2.5.5.

Explanation:
The decisive (limiting) parameter for the maximum rated continuous power defined here is the thermal component.
Starting from the 25°C of the 4-hour pre-tempering, the temperature may rise by a maximum of 20 K (1K = 1°C) during the measurement. At the start of the measurement (without the auxiliary cooling system), the engine has a temperature of 25°C, so the manufacturer can only specify 45° as the maximum value for exhausting the range. At the start of the measurement it is -20 below the 45, ie at 25°, in the following 30 minutes the motor may then reach a maximum of 45°. With the auxiliary cooling system according to 2.5.6 (this must then probably be started at the beginning of the measurement), the engine temperature may first drop, but then must not rise above 20K from the lowest point reached.
Put simply, the engine, operated with 250 W, may only produce enough waste heat that the engine temperature does not rise more than 20°C within 30 minutes. In addition to the waste heat produced, the decisive factor is the "cooling capacity" of the housing.
With additional cooling ribs on the housing of a "250 W continuous power motor" you could, for example, significantly increase the heat dissipation, operate it with more than 250 W and still keep to the 20K → more than 250 W nominal continuous power → no more pedelecs.
This method according to UN/ECE No. 85 roughly corresponds to the previously applicable "S1 continuous operation", see Section 2.2 below
(Manfred, 04/23/2017)
1.3. Conclusion
The maximum peak power is legally unlimited for EU pedelecs. Since the legally only relevant maximum continuous power is determined under laboratory conditions at 25 °C ± 5 °C, when driving at lower temperatures and with stronger airflow, significantly higher maximum continuous power than the maximum continuous power can be achieved.
When determining the maximum rated continuous power of 250W, the manufacturers are given a great deal of discretion. According to UN-ECE regulation no. 85 number 5.3.1.3. immediately before the start of the test, run the engine on the dynamometer for three minutes with the power output being 80 per cent of the maximum power at the manufacturer's recommended speed . When determining the highest 30-minute power according to clause 5.3.2.2. the electric propulsion system must be operated on the test bench at a power which, according to the manufacturer's specifications , most closely corresponds to the maximum 30-minute power. The speed shall be in a range where the net power is more than 90% of the maximum power measured in accordance with paragraph 5.3.1.This speed must have been recommended by the manufacturer. Incidentally, an alternative determination of the maximum rated continuous power according to DIN EN 15194:2009-06 Appendix D is possible outdated version, newer version unfortunately not publicly accessible .
This practice-oriented European legal situation enables current pedelec drives with a rated continuous power of 250 W as specified by the manufacturer to have a maximum power that in practice is around four times the rated continuous power, depending on the drive system: subject of motor characteristics and maximum power ; Forum post on the BionX ; another forum post on the BionX ; https://www.velomotion.de/magazin/2022/04/e-mtb-antriebe-2022-test/
Thread on the topic: 250 W rated continuous power of the pedelec - legal basis and measurement
2. Operating modes in general

2.1 Basics
The international regulation IEC 60034-1 (corresponds to the European EN 60034-1) was applied to the determination of the maximum rated continuous power until the introduction of the above-mentioned special regulations.
There are specific operating modes for each motor, ie alternation between load and rest periods. When determining the load limits, an ambient temperature of 40 degrees without additional active cooling is assumed. Also see https://de.wikipedia.org/wiki/Nennbetriebsart
2.2. S1 continuous operation
Operation with a constant load condition, the duration of which is sufficient to reach thermal equilibrium. See also IEC 60034-1 clause 4.2.1 and: forum post
2.3. S2 short-term operation
Operation with a constant load condition, but which does not last long enough to reach thermal equilibrium and a subsequent pause, which lasts until the engine temperature differs by no more than 2K from the temperature of the coolant.
2.4. S3 intermittent operation
Operation made up of a sequence of similar operating times, each of which includes a period of constant load and a pause, where the starting current

does not appreciably affect heating.

 

[Bonzo Banana]

The German forum has more info on same. The 48v max is to reduce electrocution risk. Its always mechanic power thats measured. There is no actual direct limit on maximum power. I have translated for your convenience. This I presume is the European standard. I'm not sure how much of it is applicable to England.

e-motor:nenndauerleistung [Wiki Pedelec-Forum]

www.pedelecforum.de

does not appreciably affect heating.

That reads like overly complex and manipulative legislation but I guess direct drive hub motors are more limited because they dissipate more heat according to that standard because of their greater surface area. I've seen other legislation not pedelec based ebikes and seemed much easier to navigate. The sooner the UK moves away from such awful EU legislation the better. However that reads as 1000W peak power allowed under very careful conditions of the motor which perhaps are not viable to manufacture currently perhaps a motor and components that generates less heat, less friction etc. So its like legislation designed to make manufacturing more complicated and expensive and make ebikes less accessible to consumers because of higher pricing. Simple logical legislation is consumer friendly and this is a long way from it. Overly complex designs have poor reliability, high maintenance costs and are scrapped sooner. They also lead to more proprietary and anti-competitive components. This legislation seems to give an unfair competitive advantage to premium high end ebikes and how much power they can deliver.

Perhaps this is why so many institutions around Europe have given up on ebike legislation enforcement. The UK there is little enforcement and you see people in Europe who have built ebike kits that are throttle only and have no issues where they are. It's like a wholesale rejection and lack of understanding of this abysmal legislation. The power characteristics are now ignored except for excessively powerful ebikes and the maximum 15.5mph check is purely focused on.

 

[Bonzo Banana]

I don't think it would at all. (if Ltd to 250w be useless on your hills)
I have a power meter built into my Giant Fathom and agreed it does occasionally see well above 250 w (most I, ve see n is 607 w) but that is when I, m going almost bonkers, spinning crank at 110 rpm on steep prolonged hills. (in Derbyshire) If I take it steady and keep cadence around 70,I can easily (steadily) climb any hill and power reading stays below 250.
And, I, d guess I, m amongst heavier riders at 105kg and certainly not fit taking my AF into account.
Look at it from your battery's point of view. I get over 2 hours hard riding even on my 400 wh battery. That's well under 250 w average. I, ll up load some power /cadence graphs... It actually amazes me how much help even 200w actually gives.
I think current rules /legislation is fine. My pedelec legal mtbs do fantastic job. All of them.
View attachment 49029

That 283 w max corresponded to a cadence of 103..You can see from graph nearly all climbing is done well under the 250 w threshold.

Lots of ebikes are well below 200Wh use per hour in fact some ebikes only come with 200Wh batteries or close to it and could be used beyond 2 hours. Other ebikes may have regen so they effectively pull less from the battery over time as they are topping the battery up on rides. I think a simple 250W rating should allow perhaps for 500W peak and that's it, a fair level applied to all manufacturers. Perhaps up to 1 minute of 500W peak power and perhaps a second or two up to 600W. Nice simple legislation easy to understand which all motor systems can adhere to. For those who only use ebike power for the hills and ride conventionally on flats and downhill use very little power and many of those ebike are very lightweight sub 20kg models. You would expect a motor rated to 250W to use less than 250Wh over an hour because on a ebike its not used all the time. Looking at the chart below taken from Grin if you were climbing on a direct drive hub motor ebike for a whole hour going up a hill of 15km in length at 15km/h you would use 210Wh or be averaging 210W (28Wh x 7.5 ). I've used the right column as the energy consumption x7.5 as the hill is 2km long. You could literally climb a hill for 2 hours (30km) with a 420Wh battery. Ok maybe 440Wh battery allowing for the reserve capacity that batteries hold. If you only use the motor for hills and regen downhills you could be riding that direct drive hub motor practically all day with an average Wh consumption that is well below 100Wh.

 

[matthewslack]

In defence of the EU's rules... well, a little bit at least:

In @Sturmey 's link, there is an onward link from the pedelec standard to a pre-existing motor test standard. They are not going to write another motor test standard when something already exists, so its use is understandable.

But it is used in a way its writers would not have anticipated. The 'maximum 20K temperature rise' criterion is there so that a motor sold for continuous operation (use class S1) is guaranteed to have at least its claimed power, i.e. 'not less than claimed'.

In pedelecs we are interested in 'not more than claimed'.

 

[Sturmey]

By the way, there is an argument thats its better to leave things as they are. These complicated rules can be said to work in favour of the user who wants a bit of extra power.. Any revision could result in a further restriction of power and make it easier for law enforcement. From a road safety/enforcement point of view, the 25 km/hr limit in practice (in non hilly areas) limits the useful power anyhow and many people living in hilly areas need any additional power they can get.

 

[guerney]

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[soundwave]

there cheap enough to try them but at least there in the uk and not in Germany with there rip off postage prices.

 

[Bonzo Banana]

By the way, there is an argument thats its better to leave things as they are. These complicated rules can be said to work in favour of the user who wants a bit of extra power.. Any revision could result in a further restriction of power and make it easier for law enforcement. From a road safety/enforcement point of view, the 25 km/hr limit in practice (in non hilly areas) limits the useful power anyhow and many people living in hilly areas need any additional power they can get.

I can't agree with that, I really don't like the ebike laws in the UK that are from EU legislation. I feel we need to do our own legislation which is much fairer and the plain english campaign would approve of. We need to get more people out of cars and this means reliable low cost ebikes with good functionality. I totally agree with the 15.5mph speed limit but need more power for hills and easy throttle control but I do believe ebikes should be weight limited that share paths with normal bicycles and pedestrians. I personally think we need to move away from proprietary technology too that create restrictions in component supply and repairs so at the very least clear warnings of future costs and likelihood of being uneconomic to repair and sent to landfill.