Stop and go does have negative effects, especially if driven aggressively, but they are much less severe than on an ICE car. Generally, efficiency in 25-45 stop and go should still be substantially better than 65 on the highway in a modern EV.
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Mid range battery available now?
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Stop and go does have negative effects, especially if driven aggressively, but they are much less severe than on an ICE car. Generally, efficiency in 25-45 stop and go should still be substantially better than 65 on the highway in a modern EV.
Swampgator
Active Member
omgwtfbyobbq
Active Member
I gotcha. I should say a 1-5% difference in efficiency between the two. In the first pdf, the "Artemis Jam" driving cycle efficiency is 89.7% for IGBTs and 95.1% for SiCs. If the range with an ideal inverter is 276 miles, the range over the "Artemis Cycle" would be 262.5 with the SiC inverter and 247.6 with the IGBT inverter, so a ~15 mile difference in range over a driving cycle based on the inverter used. Course that would be only be a ~3 mile difference if the efficiency difference between the two was a percent.
The difference in efficiency being largest at low loads is I think pertinent for the S/3/X because Tesla builds cars with more powerful motors than traditional automakers use, so the difference between normal driving and the EPA drive cycles is greater for Teslas than for other cars with smaller/less powerful motors.
SageBrush
REJECT Fascism
I don't think so. The range with the less efficient inverter would be 276/1.0025 = 275.3 miles
Think of it this way: Say the cycle with the best, 95% inverter is 250 Wh/mile. 2.5% of the losses are from the inverter, equal to 250*0.025 = 6.25 Wh/mile.
If we now use the inverter that has 5% greater losses the overall contribution to the car Wh/mile from the inverter increases to 6.25/0.95 = 6.6 Wh/mile and the losses per mile increase to 250.35 Wh/mile
I think you're getting numbers mixed up a couple places here. The first calculation is currently 0.25% change - from the above, I'm assuming it should be 2.5% - so 276/1.025 = 269.3
The other one bothers me more - you're talking about an inverter with 5% higher losses, and doing math correctly for that - but the math before was for an inverter with more than twice the losses - 89.7% effiency vs 95.1%, meaning 10.3% losses vs 4.9%. Accordingly, the math to match that inverter change will show a much larger deviation. (An inverter with 5% higher losses than a 95.1% efficient inverter would be a 94.85% efficient inverter.)
If a car is achieving 250 Wh/mile through a 95.1% efficient inverter/motor, that means it's using 237.75 Wh/mile to cover the ground with another 12.25 lost to heat in the inverter/motor. If that same car had an 89.1% efficient drivetrain, it'd need 266.8 Wh/mile to get the same 237.75 out the other end to cover the ground with, losing 29 Wh/mile to heat in the motor/inverter.
SageBrush
REJECT Fascism
@Saghost,
You are right ... the inverter losses are about 2x in the less efficient inverter.
It was stated earlier that losses in the inverter range from 1 - 5% of the car total so I took the middle -- 2.5%.
If total car losses are 250 Wh/mile then the best inverter has 250*0.025 = 6.25 Wh/mile
The worse inverter is 2x losses, so an additional 6.25 Wh/mile.
Our numbers differ because you are thinking of the drivetrain and I am thinking of the car.
You are right ... the inverter losses are about 2x in the less efficient inverter.
It was stated earlier that losses in the inverter range from 1 - 5% of the car total so I took the middle -- 2.5%.
If total car losses are 250 Wh/mile then the best inverter has 250*0.025 = 6.25 Wh/mile
The worse inverter is 2x losses, so an additional 6.25 Wh/mile.
Our numbers differ because you are thinking of the drivetrain and I am thinking of the car.
Knightshade
Well-Known Member
that's interesting. If so, maybe they'd just allow an "uncorking" for the normal Model 3 LR AWD (which is available with 18 inch aeros currently) and thereby one would have a Model 3 LR AWD Performance with 18 inch aero wheels again.
omgwtfbyobbq
Active Member
What I was referring to in my earlier posts was an absolute difference, not a relative or shared difference. The efficiencies in the pdf I linked aren't relative to each other, they're static. In that pdf, the left-most IGBT based inverter was around 89% efficiency and the right-most SiC MOSFET based inverter was around 95% efficiency for the first drive cycle.
I'm comparing one inverter with 95% efficiency to another inverter with 5% greater losses, and that's not the same as having 5% lower absolute efficiency. If a 95% inverter corresponds to 250 miles of range, a 100% inverter would correspond to ~263 miles. An inverter with 5% lower efficiency, so 90% efficient, would correspond to ~237 miles. An inverter with 5% greater losses, so 5%*1.05 or 5.25% losses/94.75% efficiency, would correspond to ~249 miles of range.
Edit - Ugh, used Wh/mile instead of miles of range, fixed.
TLDR - A difference in absolute efficiency is much larger than a difference in absolute losses when something's very efficient.
Edit2 - The pdfs I linked reference absolute efficiency over some drive cycle, so a 95% efficient inverter would be .95*$IdealRange and a 90% efficient inverter would be .9*IdealRange.
SageBrush
REJECT Fascism
The 250 Wh/mile losses is the entire car: drive-train, tyres, road and Aero. I've presumed that your quote of 1-5% losses from the inverter is in relation to the total car losses.
If that is incorrect then my result is way off.
omgwtfbyobbq
Active Member
The thing is - everything you quoted suffers a drivetrain/inverter penalty. (Not everything in the car does - HVAC, for instance, is independent of drive inverter efficiency.)
You need a certain amount of energy just to turn the wheels, and you pay an inverter penalty as the motor has to push the wheels.
You need a certain amount of energy to roll the tires down the road, and you pay an inverter penalty for the motor to push them.
You need a certain amount of energy to push the air out of the way - and the car does that by spinning the motor and tires, so you pay an inverter penalty on it.
If you go up a hill, you pay an inverter penalty on top of that, too. You also pay one on the regen coming back down, at least for any energy that comes back to the battery.
250 Wh/mile is the energy used to move the entire car. And almost all of it flows through the drive inverters and has inverter losses attached.
Without HVAC I think pretty much the only thing that won't have inverter losses is the energy spent keeping the computers awake and lighting lights (we established a Volt idles at about 400W with the power train active but no motion or HVAC. I'm not sure I've ever seen a Tesla number like this.)
ℬête Noire
Active Member
For some unknown reason the hub of the Performance wheels was machined in such a way that you have to have a corresponding ring machined out of the inside of the wheel rims. You physically can't mount stock 18" and 19" rims on them, even if they did fit over the larger brake calipers (or at least not with some fancy little spacer rings to have it sit proper).
The motors are physically the same, but the P flavor gets more burn in testing to ensure it can handle the higher output. So I doubt they'll let you upgrade from regular AWD to P- in the future, as in theory the motor may have failed out of P testing in the first place (assuming the testing is non-destructive to failures).
Swampgator
Active Member
oh yeah? Then if you have bad rear P motor, how does TSLA know what part to order, as there is only 1 listed in the parts catalog?
Wait a minute, yet they offered aero 18s with the performance model (allthough without the upgrade package). Probably smth to do with calipers in the end?
I know it's the case with the model S/model X, though Model 3 seems to be one piece/part only
ℬête Noire
Active Member
Here we go.
Now can we suggest Elon and his peers to offer that uncorking afterwards....for like 5,000 USD
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