Maximizing Range for the Stark Varg

Emmeffe said:
Ho fatto qualche ricerca e effettivamente ad alti giri il rendimento dei motori elettrici a magneti permanenti è più basso. Proverò anche io un rapporto 15/42
Click to expand...
translated: "I did some research and indeed at high RPMs the efficiency of permanent magnet electric motors is lower. I'll also try a 15/42 ratio".
 
I did a bunch of research on this when I was exploring the inverter/motor parameters the VCU exports. I am very much a novice in this area, but the points that stuck with me are:
  • Electric motors have a much wider range of performance properties than you might assume. Even small changes in the make-up of an electric motor can drastically change its efficiency band, performance, etc.
  • Most people that talk about this stuff are looking at motor performance in isolation. The inverter (or controller) performance and losses are also important when considering overall efficiency and power use.
  • On my EX swapping to 15/44 was a significant enough change in range performance (for my pure street use, on supermotos, etc disclaimers) that I noticed it for a few days after. My rough estimates based on Svag telemetry recordings was 5% more range from that change. I cruise a lot in 40+ so this makes sense given the next point.
  • I think field weakening is indeed the larger factor to range when considering gearing. I'm not sure if the Stark controller is inefficient, if it's just the way the "tune" works, or what, but my EX loves to dump field weakening in even at lower RPMs. Based on the ratio between ID/IQ my guess was the Stark motor efficiency band is somewhere around 6-9k RPM, and likely a 200-500 RPM range sweet spot.
Indeed as others mentioned the best cure to range is a light throttle hand and cruising under 30 (probably more about wind resistance than motor performance, but still), I'm always amazed at how far I can stretch 1-2%, and conversely how quickly I can burn 80% 😅
 
brongle said:
I did a bunch of research on this when I was exploring the inverter/motor parameters the VCU exports. I am very much a novice in this area, but the points that stuck with me are:
  • Electric motors have a much wider range of performance properties than you might assume. Even small changes in the make-up of an electric motor can drastically change its efficiency band, performance, etc.
  • Most people that talk about this stuff are looking at motor performance in isolation. The inverter (or controller) performance and losses are also important when considering overall efficiency and power use.
  • On my EX swapping to 15/44 was a significant enough change in range performance (for my pure street use, on supermotos, etc disclaimers) that I noticed it for a few days after. My rough estimates based on Svag telemetry recordings was 5% more range from that change. I cruise a lot in 40+ so this makes sense given the next point.
  • I think field weakening is indeed the larger factor to range when considering gearing. I'm not sure if the Stark controller is inefficient, if it's just the way the "tune" works, or what, but my EX loves to dump field weakening in even at lower RPMs. Based on the ratio between ID/IQ my guess was the Stark motor efficiency band is somewhere around 6-9k RPM, and likely a 200-500 RPM range sweet spot.
Indeed as others mentioned the best cure to range is a light throttle hand and cruising under 30 (probably more about wind resistance than motor performance, but still), I'm always amazed at how far I can stretch 1-2%, and conversely how quickly I can burn 80% 😅
Click to expand...

Personally, I have chosen not to use the Svag app, although let me take this opportunity to tell you that I wish I had half of your knowledge in the software field.
That said, measuring how much current is used for the d and q axes surely is a reliable method, but I think that a more empirical, albeit less accurate way of estimating the motor speed at which flux weakening occurs is to use a dyno chart, or, more conveniently, the max power line of an Alpha Varg in the advanced modes screens of the Arkenstone.
Not that I want to school you, @brongle, but I just want to explain the reasoning:
A simplified way of looking at the situation is to think that power = torque • rpm • ku where ku is a constant that depends on the units chosen.
Now, if you look at a typical dyno chart of an ideal permanent magnet synchronous AC motor, like this:
• in the first part, from 0 rpm to half the max rpm, torque is constant and the above equation becomes like
y = x • constant
which is a straight line with some positive slope, as you can see in that chart
since
y = x • k • ku
where
y = power
x = rpm
k = torque, which is constant
ku = constant that depends on the units chosen
• in the second half, power is constant because torque is progressively reduced accordingly due to field weakening, so that the equation gets the form of
y • x = constant
since
y • x = k • ku
where
y = torque this time
x = rpm
k is the constant power
ku = constant that depends on the units chosen
that's why power becomes a straight line with 0 slope, it's constant. The torque curve is a section of an hyperbola instead, since y • x = constant.
Well, the point/band in which power starts becoming constant is when the field weakening is starting to engage.
 
brongle said:
I did a bunch of research on this when I was exploring the inverter/motor parameters the VCU exports. I am very much a novice in this area, but the points that stuck with me are:
  • Electric motors have a much wider range of performance properties than you might assume. Even small changes in the make-up of an electric motor can drastically change its efficiency band, performance, etc.
  • Most people that talk about this stuff are looking at motor performance in isolation. The inverter (or controller) performance and losses are also important when considering overall efficiency and power use.
  • On my EX swapping to 15/44 was a significant enough change in range performance (for my pure street use, on supermotos, etc disclaimers) that I noticed it for a few days after. My rough estimates based on Svag telemetry recordings was 5% more range from that change. I cruise a lot in 40+ so this makes sense given the next point.
  • I think field weakening is indeed the larger factor to range when considering gearing. I'm not sure if the Stark controller is inefficient, if it's just the way the "tune" works, or what, but my EX loves to dump field weakening in even at lower RPMs. Based on the ratio between ID/IQ my guess was the Stark motor efficiency band is somewhere around 6-9k RPM, and likely a 200-500 RPM range sweet spot.
Indeed as others mentioned the best cure to range is a light throttle hand and cruising under 30 (probably more about wind resistance than motor performance, but still), I'm always amazed at how far I can stretch 1-2%, and conversely how quickly I can burn 80% 😅
Click to expand...
You lost me on the field weakening? IMO high revs and wheelspin are the biggest culprits of excess battery drain, taller gearing eliminates those to some degree. It's not something that will show on paper.
 
Theo said:
Personally, I have chosen not to use the Svag app, although let me take this opportunity to tell you that I wish I had half of your knowledge in the software field.
That said, measuring how much current is used for the d and q axes surely is a reliable method, but I think that a more empirical, albeit less accurate way of estimating the motor speed at which flux weakening occurs is to use a dyno chart, or, more conveniently, the max power line of an Alpha Varg in the advanced modes screens of the Arkenstone.
Not that I want to school you, @brongle, but I just want to explain the reasoning:
A simplified way of looking at the situation is to think that power = torque • rpm • ku where ku is a constant that depends on the units chosen.
Now, if you look at a typical dyno chart of an ideal permanent magnet synchronous AC motor, like this:
• in the first part, from 0 rpm to half the max rpm, torque is constant and the above equation becomes like
y = x • constant
which is a straight line with some positive slope, as you can see in that chart
since
y = x • k • ku
where
y = power
x = rpm
k = torque, which is constant
ku = constant that depends on the units chosen
• in the second half, power is constant because torque is progressively reduced accordingly due to field weakening, so that the equation gets the form of
y • x = constant
since
y • x = k • ku
where
y = torque this time
x = rpm
k is the constant power
ku = constant that depends on the units chosen
that's why power becomes a straight line with 0 slope, it's constant. The torque curve is a section of an hyperbola instead, since y • x = constant.
Well, the point/band in which power starts becoming constant is when the field weakening is starting to engage.
Click to expand...
I'm completely confused by all this. Is their a summary that applies to the Stark in real life, not theory?
 
Johnny Depp said:
I'm completely confused by all this. Is their a summary that applies to the Stark in real life, not theory?
Click to expand...

The best way in which I can answer is this: if you look at the max power line of an Alpha Varg in the advanced modes screens of the Arkenstone, you will notice that the max available power keeps rising until roughly 7k - 7.5k rpm and then it stops rising. Not exceeding that thereshold should improve efficiency.
 
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