Which scenario drains the most battery?

[Deleted member 4366]

Good questions.
1. There are basically two types of system that respond to the PAS setting. Speed control allows full power for accelerating but limits the speed in each level to a different value. Current control limits the power (current) to a different value in each level, but it allows full speed. Oxygen bikes use both. They have three levels of power and 6 of speed, so 18 combinations.

2 Yes it does. Everything becomes more complicated when you reduce PAS or the throttle. Generally, the efficiency curve gets shifted down the RPM range. I haven't yet figured out what happens with current control controllers, but basic logic says to me that efficiency would be lower than a speed control one; however, in practice, there's no noticeable difference. I guess that it gains in some circumstances and loses in others.

 

[OldBob1]

Also another variable is that once the motor starts turning, back emf enters the equation apposing the current from the controller.

 

[GLJoe]

Good questions.
... Current control limits the power (current) to a different value
...
Everything becomes more complicated when you reduce PAS or the throttle. Generally, the efficiency curve gets shifted down the RPM range.

Ok, thanks for that. That's what I imagined would happen (the max efficiency zone seems to be related to the voltage. Some graphs I came across indicate you lower the voltage, and thus lower the zone).

So when you say 'Current control limits the power', what is actually happening here? On a typical ebike with a simpler control setup compared to the Oxygen, when you change assist settings (eco, tour, turbo etc), and I guess also when you introduce a torque sensor into the equation, is it actually varying the voltage (which would determine the current). And if so, how do they typically do this. Is it some kind of PWM setup?

 

[Tabs]

All sounds like it's getting complicated,I usually ride in level 2 (of5) and use the throttle(still can't get used to calling it a throttle)whenever I need it and I need it constantly,sometimes to get up a hill or get me up to speed to keep up with other riders or just to get a wee rest from peddling.

 

[Deleted member 4366]

You can't vary the voltage. The battery is connected directly to the motor, but it's blocked by the mosfets. all the controller does is open and close the mosfets in the right sequence in short pulses. you have to see the power provided to the motor as pulses of energy that have a height (voltage) and time. You could argue that there's an average voltage and/or an average current.

That's it in simple terms, but you have to add in the effects of capacitance and inductance in the coils and the help from any output capacitors.

The torque sensor is only a sensor. The controller reads it and regulates power to whatever algorithms are programmed into it. Basically, the controller is a tap. the CPU reads sensors and opens/closes the tap accordingly.

 

[Deleted member 4366]

I usually ride in level 2 (of5) and use the throttle(still can't get used to calling it a throttle)whenever I need it

On an electric bike, it's not really a throttle because it doesn't throttle anything. Technically, it's a speed controller.

 

[Tabs]

I call it the magic button(I know it's not a button but hay ho)

 

[D C]

I call it the magic button(I know it's not a button but hay ho)

I wonder if it's possible to replace the throttle with a push button?
A lot of folk who have a pedalec system with throttle seem to only use the throttle full on for an extra spurt of power when needed (not a criticism).
Dave.

 

[Woosh]

I wonder if it's possible to replace the throttle with a push button?
A lot of folk who have a pedalec system with throttle seem to only use the throttle full on for an extra spurt of power when needed (not a criticism).
Dave.

it's kind of ironic that the throttle (or 'magic button') would be more useful on a torque sensor bike to give yourself an extra push and yet only available on rotational sensor bikes where you only have to wait a little for the power to ramp up.

 

[Tabs]

I like the (throttle) ability to vary the amount of input of assistance

 

[GLJoe]

You can't vary the voltage. The battery is connected directly to the motor, but it's blocked by the mosfets. all the controller does is open and close the mosfets in the right sequence in short pulses. you have to see the power provided to the motor as pulses of energy that have a height (voltage) and time. You could argue that there's an average voltage and/or an average current.

That's it in simple terms, but you have to add in the effects of capacitance and inductance in the coils and the help from any output capacitors.

Do you happen to have any links to say a waveform/timing diagram depicting these pulses?
I can think of a few ways that the mosfets might be driven, but I'm curious to know how its actually done in practice.

 

[Tabs]

Just push the button (throttle) for instant gratification

 

[Deleted member 4366]

https://www.electricbike.com/sine-wave/

 

[philliptjohnson]

I wonder if it's possible to replace the throttle with a push button?
A lot of folk who have a pedalec system with throttle seem to only use the throttle full on for an extra spurt of power when needed (not a criticism).
Dave.

The Carrera crossfire e has a button 'throttle' but its limited to 6 mph (I believe). Assuming it's normally used if you can't get the bike moving for physical reasons... Get it started with throttle then start moving pedals so pedal assist locks in. Could be corrected on this though from a more knowledgeable pedelecer

 

[GLJoe]

https://www.electricbike.com/sine-wave/

Thanks for that.
I also found this:
http://www.samsung.com/global/business/semiconductor/file/product/s3f84a5_Ebike_apn_rev110-0.pdf
And also a Zilog application note that could have done with more detail, but talked about setting the PWM frequency to 20KHz.

So it seems that at least some (and possibly all) of these controllers are indeed using PWM as the control mechanism. Which given the frequencies and inductances involved, you would probably be ending up with a fairly smoothed power source to the motor and does effectively mean that you are varying the voltage.