Porformance drop off with lower battery %age.?

[Zlatan]

..but lower torque doesn't get you up that hill even if it lasts for much longer!

Think about the average torque help over the course of a full rotation of pedals. With the higher torque / voltage figure you ate not being helped " as long"
If you averaged out the torque given over a full revolution it must be the same ( your rpm has not altered, power is simply torque multiplied by rpm...the power used ( produced) is almost constant ( on max help)
If this were not case the help on a newly charged battery would be way higher ( around 25%) to that of one at inly 50% charge...yet the difference in usage is negligible.
ie..average torque ( 1 full rev) equals power / rpm...( therefore torque help over a full revolution of crank is the same)

 

[chris_n]

The overall torque would be the same...in that higher voltage would provide higher torque but for very short time...lower voltage...lower torque but for longer...net result equal.power..

And I have noticed my first 25% of battery power gets me further than 50 down to 25%...which again makes sense...I,m extracting constant power from a diminishing power source...but I,m fairly convinced my Haibike climbs just as well under 10% remaining to the first 10%...but it would not climb as far...( if that makes sense???)
But some extra control comes in under 2% remaining...it definitely starts rationing what is available...I suppose in an effort to fend off no power...( or it might simply be at point where lower voltage can not be compensated for with longer pulses...ie pulses at max duration by 3% remaining ???

You still haven't said what size your battery is. The behaviour you describe is how I felt a 500wh battery working but my (and others that I know of) do this rationing what is available thing much higher. I guess at 10% it could be no longer able to give enough voltage that no matter how wide the pulses the energy available is not sufficient.

 

[Zlatan]

You still haven't said what size your battery is. The behaviour you describe is how I felt a 500wh battery working but my (and others that I know of) do this rationing what is available thing much higher. I guess at 10% it could be no longer able to give enough voltage that no matter how wide the pulses the energy available is not sufficient.

The size of the battery is irrelevant. The voltages at various %ages are identical. Yes a larger battery will extend your range but would not cure the problem you encounter, merely delay it. I don't get the problem and 30 miles off road is sufficient.

 

[chris_n]

In this discussion it is relevant to me as I have seen distinctly different behaviour between the two different sizes. If you are running a Yamaha with a 500Wh battery you will not have the same experience at 10%.
The whole control system for what a Yamaha battery does is contained within the battery itself unlike most others. This is why you can use the self test features to determine number of cycles, capacity reduction etc. It is this that I suspect makes the feeling different.

 

[GLJoe]

The whole control system for what a Yamaha battery does is contained within the battery itself unlike most others. This is why you can use the self test features to determine number of cycles, capacity reduction etc.

Are these 'self test' features something that a user can access/view via a sequence of special keypad presses etc? I'd be interested in how to do this if so!

 

[chris_n]

Are these 'self test' features something that a user can access/view via a sequence of special keypad presses etc? I'd be interested in how to do this if so!

First hit on google though I do have full manual saved somewhere.
https://electricbikereview.com/forum/threads/tip-yamaha-pw-how-to-check-the-number-of-cycles-absolute-battery-capacity.13057/

 

[GLJoe]

First hit on google though I do have full manual saved somewhere.
https://electricbikereview.com/forum/threads/tip-yamaha-pw-how-to-check-the-number-of-cycles-absolute-battery-capacity.13057/

Awesome! just tried it and it seems to work. Thanks for that.

Now.... I wonder if there is something similar for Bosch?

 

[Danidl]

I would say it's more accurate to say the controller regulates the ENERGY into the motor in terms of amps x time.

Using an extreme example, if you considered two rectangular pulse waveforms. Waveform A has a very high peak current and a very narrow mark. Waveform B has a very low peak current and a very wide mark. The area of both (and hence energy delivered) is the same but which one gives you the most torque?

For the posh controllers to maintain everything perfectly as the battery volts drop they would probably need some kind of DC-DC converter in there which is fairly unlikely given the size / efficiency constraints.

The controller is exactly that it is a class of a DC to DC convertor.. it pumps pulses of charge through each of the coils It could be classed as either a single polarity voltage input to 3 Voltage output regulated voltage outputs bipolar. Or a DC to 3 phase AC convertor or anything else you wish.. . Each charge pulse provides impulses of mechanical force.
.. The inductance of the coil in each winding, limits the rise in current as a function of time. It might be better to think of it as quantity of charge ( coulomb's ) deposited during each pulse. The current in any winding never reaches the steady state value that ohm's law would predict. It gets switched off long before.
A larger driving voltage will assist in pumping more charge down the coil, for a fixed fixed on period. The designer of the controller can vary both the pulse rate , the PWM pattern, and the duty cycle. Even with a scope, and viewing the voltage waveforms to discern the actual patterns would be extremely difficult. , As it needs the motor windings to integrate the pulses into a current waveform.

 

[Danidl]

Awesome! just tried it and it seems to work. Thanks for that.

Now.... I wonder if there is something similar for Bosch?

... I think you have to put it on a usb diagnostic rig at the dealers...

 

[dgncsk]

The battery voltage is always applied to the motor. The controller has a series of gates that open and close very quickly in short pulses of battery voltage. All it can do is control the time that the gates are open. That's why the power diminishes as the battery voltage runs down. the energy in each pulse is basically the voltage times the time of the pulse.

so will a 11S battery instead of 10S work without making any damage?

 

[Danidl]

so will a 11S battery instead of 10S work without making any damage?

Putting an additional 4v in series will increase your overall voltage up from a nominal 36 to 40 v or about 10% . Whether it will damage , will depend on the safety margin in the controller
, d8veh, will say no bother, and I am inclined reluctantly to agree with him, but it is bringing the electronics closer to their margins. The components inside the controller all have maximum voltage ratings, overwhich they will flashover and be destroyed instantly. Typically these might be 48v or 63v . Running components close to their max ratings will reduce their lifetimes.When the components getting warmer, the flashover point decreases. My training would be to be very conservative
But the extra voltage will improve top speed , and give the bike more pep

 

[Deleted member 4366]

so will a 11S battery instead of 10S work without making any damage?

Yes, it should. All the timings will be the same, so for each pulse, you'll get 10% more energy. That means 10% more torque and power, and the motor will be able to spin 10% faster because it will have more voltage to overcome the back emf.