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Discussion Starter · #1 · (Edited)
Hi there,

during my studies about 10 years ago I designed a software to perform preliminary design of electric vehicles.

It is quite accurate (within 5% or so for range) and validated against Zoe, Tesla model S, eNV200, etc...
It can compute range (with or without regen), 0-100kmh time, etc, depending on physical parameters such as test drive sequence (fully editable), vehicle characteristics Scx/weight/tires rolling resistance, battery characteristics etc...

You can find the standalone SW here (it is for windows 64bit), just run the interface.exe application (no virus, I designed it myself!)
Help manual is here, only french, but SW is english based:

some screenshots herebelow:
138615

138616


Hope this will help !

Vianney
 

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When you say "geared motor" do you mean single fixed speed or a multiple speed gearbox? I'm interested in the plot C=f(N) blue plot.
 

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what are your thoughts on potential performance benefits vs drawbacks of bldc motors with variable rpm per volt constants like shown:


i did a writeup of my thoughts on it in this post:

we get more low end torque than before, and more high end top speed, without taking more current from the battery or putting more current through the motor
 

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Discussion Starter · #7 ·
When you say "geared motor" do you mean single fixed speed or a multiple speed gearbox? I'm interested in the plot C=f(N) blue plot.
you can define multiple speed gearbox by defining the gearbox ratio as a function of the vehicle speed.
 

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Discussion Starter · #8 ·
what are your thoughts on potential performance benefits vs drawbacks of bldc motors with variable rpm per volt constants like shown:


i did a writeup of my thoughts on it in this post:
Hi, it is not something I have studied so I can't tell you :).
 

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Does the green line, bottom left chart look correct to you? Only the rpm per volt no load (kv) is changing...

400v bat, 0.045ohm 2 phase resistance, kv variable 10kv-35k, 700mm tire, 8.66:1 gearing, 100% throttle, 735a motor current limit, 207.5a battery current limit, 0.32 drag coefficient, 2.28m frontal area, 1.225kg/m^3 air density, 4000 pound mass, bldc - 126mph top speed w/ ~81kW motor output.

 

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Discussion Starter · #10 ·
Does the green line, bottom left chart look correct to you? Only the rpm per volt no load (kv) is changing...

(400v bat, 0.045ohm 2 phase resistance, kv variable 10kv-35k, 700mm tire, 8.66:1 gearing, 100% throttle, 735a motor current limit, 207.5a battery current limit, 0.32 drag coefficient, 2.28m frontal area, 1.225kg/m^3 air density, 4000 pound mass, bldc.


Well I don't understand the plots ;) ..
 

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Well the green line in the top right chart is the same as the red line in your chart (Newton meters motor torque) but instead of rpm at the bottom we have ground speed after the motor output is run through an 8.66:1 gear reduction and a 700mm diameter wheel.
 

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Discussion Starter · #12 ·
Well the green line in the top right chart is the same as the red line in your chart (Newton meters motor torque) but instead of rpm at the bottom we have ground speed after the motor output is run through an 8.66:1 gear reduction and a 700mm diameter wheel.
bottom left green chart is not torque, it is labelled thrust in pounds. Thrust is then related to torque by the mean of wheel radius.
So for 10kv 0pmh 4000pounds = 18kN, looks definitely too high, because 18Kn with 0.35m wheel radius would be 6300Nm, while top left green line indicates 700Nm of torque maximum... So yes there is something weird !
 

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Discussion Starter · #16 ·
So would you agree a variable KV (no load rpm per volt) is in effect equivalent to a variable gear ratio?
yes. I am not expert in electric motor control, but what would be the benefits of this type of motor ? BLDC motors can also be controlled in speed by PWM on the voltage, aren't they ?
 

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yes. I am not expert in electric motor control, but what would be the benefits of this type of motor ? BLDC motors can also be controlled in speed by PWM on the voltage, aren't they ?
This one for my skateboard shows it better...

I have 70kv motors giving me 240lbs thrust (more than 1 to 1 thrust to weight - max 30mph top speed), but if I can pull out the stators while I’m accelerating, I can keep the peak of the purple horsepower line in the top right chart at the same speed I’m going while I accelerate to a much higher top speed, giving an acceleration advantage compared to a fixed higher or lower KV motor.
 

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Discussion Starter · #18 ·
This one for my skateboard shows it better...

I have 70kv motors giving me 240lbs thrust (more than 1 to 1 thrust to weight - max 30mph top speed), but if I can pull out the stators while I’m accelerating, I can keep the peak of the purple horsepower line in the top right chart at the same speed I’m going while I accelerate to a much higher top speed, giving an acceleration advantage compared to a fixed higher or lower KV motor.
ah yes looks interesting indeed !
 
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