Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[NoiseBoy]

It always feels to me as though the bike is quite heavily restricted at lower speeds, i assume to make it rider friendly and improve range.  Is the controller purposely limiting current at low rpm or is it a characteristic of the motor itself or just the need to keep it cool?  If not surely performance could be gained with the Sevcon software and removing the need to spend $2000+ on a size 6 upgrade.

[BSDThw]

In my understanding it is caused by the PM-Motor.

The motor type has a dependency between rotation and voltage => you will always start with 0V and reach your top voltage at the nominative rotation. More rotation will need field weakening (it starts at ~3500RPM)
If you start you will have 420A but ~0V(0KW) .. 5V(2.1KW) ... 10V(4.2KW) .. 15V(6.3KW) ... =>  So the 21KW at a 2012 S/DS will only be at ~3500RMP.

Therefore the bike is "weak" at low speed!

I make a simple picture in my head: The motor is also a generator and if propelled it produce a voltage. The voltage raise if propelled faster like your bicycle light becomes brighter as faster you ride!
The regulator has to reach this voltage and raise it (slightly) so the current will not come out of the "generator" instead it will go into the now "Motor". You can not raise the voltage more because it would produce a gigantic current.

I have done some theoretically calculation how the power will be compared to speed.
 

[NoiseBoy]

So with a PMAC motor the most effective way to gain performance would actually be to run lower gearing with a higher voltage to allow a higher maximum rpm, whilst staying within the design limits of the motor.  That way peak power happens earlier/at a lower speed.

Has anyone tried running DS gearing on the S model?  The DS feels significantly nippier at lower speed and i don't need to cruise at high speed so I hope to try it soon.

[BSDThw]

lots have don't a 25 sprocket to a S, Terry, Harlan wrote about... the S wheel perimeter is ~1.5% more so it will feel quite equal. I just plan to do the other way round a 28 to my DS, the power peak is at 72km/h and the normal road speed is 100km/h. So i would like to have a longer gearing.

A two gear system would be interesting, I once mentioned an idea with no power loss at the high gear. But if you have a more powerful motor (2013) it will be more and more unnecessary.