Daniel in SD
(supervised)
Power is not consumed, energy is. You are using more power but for a shorter period of time. It takes the same amount of energy to accelerate to 60mph whether you do it in 3.5 seconds or 1ms.
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P3D+ 250 mile range with non-aggressive driving
- Thread starter khraiv
- Start date
Definitely not. But is 10% throttle better than 5% or 15%, who knows.
Daniel in SD
(supervised)
I think you're right that the internal resistance of the battery pack may make fast acceleration less efficient.
I'm not an electric motor expert but a quick search of electric motor efficiency vs. load seems to say that the motor efficiency doesn't decrease significantly with load.
You're absolutely right, but the part you're missing is that if you accelerate from 0-60 in 3.5 sec vs accelerating from 0-60 in 7 sec., you use twice the power in the first case, but accelerate for 1/2 the time.
So the *energy* you expend is the same. Wh is a unit of energy, not power, and energy is what matters when we talk about efficiency over distance.
(Note that if you accelerate more quickly, your average speed will be higher for the entire trip, which will hit efficiency because of energy losses due to aerodynamic drag, which scale with the square of the speed.)
Daniel is not exactly right about the acceleration, either - Electric motors *are* less efficient at high torques, particularly at low speeds. (Interestingly enough they are also less efficient at very low torques).
See, for example, this presentation which includes efficiency contours for a Nissan Leaf motor + inverter (https://www.energy.gov/sites/prod/files/2014/03/f13/ape006_burress_2013_o.pdf)
Note that this efficiency loss is not huge (e.g., at 2000rpm, the Leaf motor/inverter combination shows a 90% efficiency at 100Nm vs an 86% efficiency at 250 Nm), so the biggest effects are likely due to the speed, not the acceleration.
Ok granted, in an ideal situation with no resistive friction and no electrical resistance it would be the same amount of power. However I found this other thread that discusses among other things that the faster you accelerate the more losses are sustained in the battery and motor. Doubling the acceleration quadruples the loses due to electrical resistance.
Why does accelerating fast use more energy than accelerating slowly?
Why does accelerating fast use more energy than accelerating slowly?
Daniel in SD
(supervised)
Ok. You're correct about resistive losses. That's why battery capacity does drop at higher loads. Found this thread where someone measured a bunch of different 18650s (Talk about dedication!). 18650 battery test with capacity curves for many cells
The data from the Nissan Leaf posted above shows that the motor and inverter are maximally efficient at full power at highway speeds.
Anyway, none of this is going to stop me from accelerating quickly
Look at the first post here, especially the graph:
Car’s energy consumption (lack of) accuracy
It's presented in terms of "dashboard error", but it's really just about increasing losses (apparently internal to the battery, so not measured by the car) as the driver uses more power. At low power (low speeds/slow acceleration), the energy you get out of the battery comes pretty close to the energy you put into it. At high power some of that energy is lost to resistance in the battery and you get much less out of the battery than you put into it.
More power = more losses, and this is just one source of those losses.
Car’s energy consumption (lack of) accuracy
It's presented in terms of "dashboard error", but it's really just about increasing losses (apparently internal to the battery, so not measured by the car) as the driver uses more power. At low power (low speeds/slow acceleration), the energy you get out of the battery comes pretty close to the energy you put into it. At high power some of that energy is lost to resistance in the battery and you get much less out of the battery than you put into it.
More power = more losses, and this is just one source of those losses.
UltralightBeam
Member
So... the thing that worries me as stated by the OP was that the onboard maps navigate you to a supercharger with like 10% battery left... if the car detects you can’t make it there, will it adjust dynamically and day go to this other supercharger that’s 50 miles sooner instead?
Will the data collected from P3D+ cars be used to improve the AI calculation for routes?
Hmm I wonder if there are even potential software tweaks they could make for P3 cars / awd to improve this. Maybe a “road trip” mode.
Bit first, proper navigation if it already doesn’t navigate you to a closer supercharger.
Will the data collected from P3D+ cars be used to improve the AI calculation for routes?
Hmm I wonder if there are even potential software tweaks they could make for P3 cars / awd to improve this. Maybe a “road trip” mode.
Bit first, proper navigation if it already doesn’t navigate you to a closer supercharger.
SageBrush
REJECT Fascism
Nor was my average anywhere close to that. I said limit+5 (plenty of 35s etc), which is super typical real-world driving. Anyway, my post was only to educate and show there are still improvements to be made in the estimations. I fully expect that I will never hit 310 mile range under any real-world circumstance, I just want Tesla to be honest and favor proper estimates over inflating marketing numbers.
Edit: regardless of speed, I have never seen any lower than 240watt/mile, and it was not sustainable. Even conservative city driving is generally around 280watt/mile. This car does not get anywhere near the mileage of rwd stock aeros, nor should it. I just want accurate estimates instead of fictional data.
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SageBrush
REJECT Fascism
That is your problem, due to your driving habits.
I rarely see EPA results either. Routinely 10% less than EPA, sometimes 20% less. Real World.
insaneoctane
Well-Known Member
This is why some people put their car into chill mode with AP/TACC. it helps reduce the acceleration thereby increasing efficiency.
You get the best efficiency when you drive around 40mph. As you go up from there, efficiency goes down. So if you were indeed driving 70-80 on the highway, then that's what killed your efficiency. Very simply to get better efficiency, you got to reduce your speed.
For local driving at around 45mph I consistently get 240-250wh/mi. And that's with my aggressive, launch at stoplight driving. You can be non-aggressive as the OP states. But it won't matter once you start going above 60mph, that's when efficiency really goes down.
For local driving at around 45mph I consistently get 240-250wh/mi. And that's with my aggressive, launch at stoplight driving. You can be non-aggressive as the OP states. But it won't matter once you start going above 60mph, that's when efficiency really goes down.
I look forwards to doing a range comparison between the 70D Model S that I have now versus the P3D+ that I'm taking delivery of next week.
I don't really care for getting a precise estimate of range. But, just what I can reasonably assume given mild conditions. With the 70D the REAL world range that one generally wanted to stay within was 180 miles. This is under the assumption of a 90% charge along with having around 10% left when arriving at the supercharger.
So that resulted in having to charge the car 2-3 times every round trip to Portland since it's about 200 miles away where the supercharger is around the halfway mark. Basically it came down to deciding whether to drive fast and to charge 3 times or to slow it down a bit, and charge 2 times where one of those times might be a bit more than 90%. It really was dependent on weather, and cold rain I didn't even bother trying to charge only twice.
With the P3D+ I'm expecting to only charge it once at my destination or in Vancouver which is fairly close the destination. Part of my rationality in getting the car was I didn't really feel like supercharging anymore on that trip. I figured I could just use destination charging, and not worry about it.
I don't really care for getting a precise estimate of range. But, just what I can reasonably assume given mild conditions. With the 70D the REAL world range that one generally wanted to stay within was 180 miles. This is under the assumption of a 90% charge along with having around 10% left when arriving at the supercharger.
So that resulted in having to charge the car 2-3 times every round trip to Portland since it's about 200 miles away where the supercharger is around the halfway mark. Basically it came down to deciding whether to drive fast and to charge 3 times or to slow it down a bit, and charge 2 times where one of those times might be a bit more than 90%. It really was dependent on weather, and cold rain I didn't even bother trying to charge only twice.
With the P3D+ I'm expecting to only charge it once at my destination or in Vancouver which is fairly close the destination. Part of my rationality in getting the car was I didn't really feel like supercharging anymore on that trip. I figured I could just use destination charging, and not worry about it.
SageBrush
REJECT Fascism
You misapply average speed as it effects fuel consumption.
E.g.,
Consider a case of driving at 60 mph all the time vs 80 mph half the distance and 40 mph the other half:
The 80/40 pattern has ~ 10% higher Aero losses.
SageBrush
REJECT Fascism
I should clarify, I mean my REAL WORLD (tm) Wh/mile is 213 Wh/mile lifetime with a range of 190 - 250. EPA is 250 Wh/mile
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