What's the best 250 watt...

[soundwave]

buy a bosh s class bike

 

[(NoLongerRegistered#15675)]

And put a booster battery on it.

 

[danielrlee]

Legal pedelec = motor with a 250W nominal rating.

nominal
adjective

(of a role or status) existing in name only.

....and your speed control lever idea is a throttle.

 

[soundwave]

 

[Deleted member 4366]

If you know the maximum torque of your motor, you can easily calculate its maximum power if you know what they mean by it when they say that maximum torque = 80Nm.

The problem is that the stated torque is absolutely meaningless unless they say at which speed it's measured and where it's measured. Is it at the crank or at the back wheel? If at the back wheel, what gear is it in (presumably bottom) and what is the gearing? A 3v Airfix motor with the right gearing can provide 100Nm whilst only consuming 5 watts.

 

[(NoLongerRegistered#15675)]

A throttle is a term derived from petrol ( and other ICE engines but not incidentally diesel engines) in which air is prevented from entering the engine and so preventing ir from revving higher. Engine is starved of air as in "throttled". Hence term throttle.
A diesel engine strictly speaking isn't throttled either, its speed is governed by a reduction( or increase) in fuel. It is not starved of air, hence it is not throttled. Designers have for years been trying to utilise open throttle control on petrol engines, it would reduce pumping losses and help efficiency at various power requirements. Its one of the reasons diesel engines are more efficient thab petrol. Neither is an electrical motor controlled by a throttle.
The brushless dc motor changes its speed through a change in supply currents frequency and with corresponding increase in current. It is not starved of air , so it ain't a throttle.
And google UK Pedelec Law..It does not mention " nominal"
It says
" maximum rated power 250w"

Learner legal motorbikes are limited to 11kw..I suppose folk on here would stretch that to Hayabusa,s.
Its only same margin of error.( well similar)

 

[(NoLongerRegistered#15675)]

If you know the maximum torque of your motor, you can easily calculate its maximum power if you know what they mean by it when they say that maximum torque = 80Nm.

The problem is that the stated torque is absolutely meaningless unless they say at which speed it's measured and where it's measured. Is it at the crank or at the back wheel? If at the back wheel, what gear is it in (presumably bottom) and what is the gearing? A 3v Airfix motor with the right gearing can provide 100Nm whilst only consuming 5 watts.

Yes I totally agree with that but think you,ll find Yam and Bosch are quoting at crank..and yes you are correct its almost meaningless without an rpm..if its at zero there is no work been done. If it were at a cadence of 80 itsaround 900w ( guesstimate) but not hard to work out..

 

[anotherkiwi]

Kiwi
You quoted a read out of 530w on your bike.
Exactly what were you doing with it at time ? And
a) Could bike remain in that condition long ?
b) Could rider maintain what he/she is doing for situation to continue ?
I suspect answer to both is no.

Climbing the hill between St Jean de Luz and Hendaye - just over 4 km from memory.

If I don't want to pedal hard in assistance level 5 (with my controller that is = to 200% current) it will draw between 380 W and +500 W all the way up depending on the slope.
I am pedalling cadence 70ish in 2nd or 3rd gear all the time without applying much force, just enough to not spin out in such a low gear.

At the top the controller is too hot to touch (it is in a bag on the frame is one of the main reasons) and the motor as cool as a cucumber. My Li-ion battery sags badly when treated like that but the Lipoly battery doesn't blink an eyelash just keeps on giving and giving.

 

[Deleted member 4366]

And google UK Pedelec Law..It does not mention " nominal"
It says
" maximum rated power 250w"

That's true, but whatever official website you look at, there always seems to be mistakes and omissions. The European Standard for electric bikes, which has been adopted in UK law is EN15194. The copy that I have includes the word "nominal", but I saw a draft version, where that word had been dropped. Anybody have the latest version to confirm?

Whether that word is included or not, it doesn't make a lot of difference because, as far as I can see from the standards, there's nothing to stop any company from rating their (would be) 1000w motors at 250w.

 

[anotherkiwi]

"It applies to electrically power assisted cycles of a maximum continuous nominal power of 0,25 kW, whose power is gradually reduced and finally stopped when the vehicle reaches a speed of 25 km/h, or sooner, if the cyclist stops pedalling."

There you go both nominal and maximum in the same sentence. This is the 2009 version.

 

[(NoLongerRegistered#15675)]

That's true, but whatever official website you look at, there always seems to be mistakes and omissions. The European Standard for electric bikes, which has been adopted in UK law is EN15194. The copy that I have includes the word "nominal", but I saw a draft version, where that word had been dropped. Anybody have the latest version to confirm?

Whether that word is included or not, it doesn't make a lot of difference because, as far as I can see from the standards, there's nothing to stop any company from rating their (would be) 1000w motors at 250w.

That's also true but we have no idea how pedal assist system is limiting the power.
You cant look at ab individual item in system and establish power produced. I,m fairly sure with my yam I get loads of assistance at low cadence/ high pedal pressure. As former increases latter must drop and hence so does power from motor. It all depends how pedal torque sensor, controller are configured. The motor actually has little say in matter , as long as it can cope with current thrown into it and convert that to motive power.

I demod a Bosch system and that did feel different. Initially not as helpful ( even after 3/4 cadence) but gave more at higher cadence than yam..but I preferred immediateness of yam so bought that. ( and it was £400 cheaper)

I,d love to know triggering pressures for both systems..its what the bike system revolves (supposed to be a smiley) around..

 

[Deleted member 4366]

Generally, all DC motors make highest torque at low RPM, so in any one gear. You feel the force from the torque as power, though the true power is less than what it would be at higher RPM. That's why crank motors often feel more powerful than hub-motors, even though they're not. When you start off in low gear, you have high torque which makes them feel powerful.

 

[(NoLongerRegistered#15675)]

Generally, all DC motors make highest torque at low RPM, so in any one gear. You feel the force from the torque as power, though the true power is less than what it would be at higher RPM. That's why crank motors often feel more powerful than hub-motors, even though they're not. When you start off in low gear, you have high torque which makes them feel powerful.

Yes you are correct, characteristics of motor can be changed with different windings but both wye (Y) and delta do give more torque at lower speeds...however power produced and used are different. The revs rise faster than torque falls so overall motor is producing more power with increased rpm until motor reaches point where torque is falling off dramatically or it can rev no higher.( totally agreeing with you) The fall off if torque with rising rpm is common to many motors, petrol, electric and diesel, most , if not all petrol engines produce max torque around 2/3 max rpm but have steep torque curves that fade.Diesel on other hand have flat torque curves,that stop abruptly)
Its why they feel so different.

Its a bit different with pedelecs tho. All cyclists produce most torque at zero rpm.( ie if you stand on pedal) but even when peddaling normally cyclists produce falling torque with increased rpm. ( probably tour cyclists are different? Our torque characteristics are along lines of steam engines, max at zero. Its why pushbikes and steam engines don't need clutches) Pedelec torque sensor senses the reduced torque ( its torque sensitive not rpm) and correlates this torque with motor torque ( varying according to which setting) ...so not only does motor produce less torque, the controller is instructed to reduce current in line with riders reduced torque..( for yam system anyways)
I,ve experimented with mine and its almost impossible to get high current indicated ( on graphic) with high cadence ( over 65 ish) for any sustained period.( but would I need electric if I could sustain high torque / high cadence?? Its what tour riders can do)
I get max help at very low cadence, too high gear. Its almost opposite to many other,s findings..
Made us all think tho...( my smiley,s aren't working)

Your comment about feeling torque is spot on tho. Its torque at wheels we feel as acceleration in every vehicle..Its why vehicles accelerate quicker in lower gears, its why they climb hills in lower gears..( gearing down increases torque but leaves power unaffected)



In other words, in engineering terms, the nominal power rating is the mechanical power at the output shaft,the machine might be consuming more in watts because of heat losses and other inefficiencies.

 

[Deleted member 4366]

That's the definition for installed power, not nominal power. They're only using the nominal power of the motor as an example to show the difference between input and output power. They're not defining it.