Featured Model 3 has 310 mile range

Looks like the epa data is out ... and the highway blended combo looks pretty nice ... especially for a single drive motor;

Tesla Model 3's EPA Rating Hits Equivalent of 126 MPG - The Drive

when the all-wheel drive 3 is released, and if history repeats itself, the epa #'s will be even higher. It was discovered that by adding a smaller drive motor in the front - when the power isn't needed, the Tesla will put 'big brother' in the rear into a sleep mode, letting the smaller/more efficient front motor do all the work.
the epa #'s are not too shabby!
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I'm pretty happy with the numbers.
I have been so used to Tesla vehicles being more efficient on the highway then set the street, it was a bit of a surprise to see the model three more efficient in the city.
But considering the smaller size that seems to make sense.

 

I drove my 2004 Prius for 13 years and 150,000 miles using less than 25% of the usable thickness of them OEM brake pads.

 

The thing is, electric motors give people a real thrill when they put their foot into it with all that torque. for many ev drivers, that becomes the achilles heel for decent city driving MPG.
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I don't believe that follows with the Model S/X. First, those cars definitely do not wear out their brake pads.
It isn't a matter of 'figuring out'. It is simply a matter of the weight of the vehicles. Getting such heavy vehicles started from zero takes more energy than maintaining hwy speeds.

I would also suggest, hwy efficiency was more important than city. The Model S and X are designed to be capable of long distance travel. High efficiency on the hwy gives more range than high city efficiency.

 

Yes, but with a heavier vehicle there is also more available energy to return to the battery with regeneration.

Ideally it would just scale up with the size of the vehicle although because mass goes as the cube of scale but frontal area goes as the square of scale there is probably an overall advantage for aerodynamics as vehicle size increases.

I suspect also that the induction motors in the Model S/X are not as efficient at regeneration as the permanent magnet motors in all other vehicles. Induction motors require excitation even when regenerating.

kevin

 

It's a simple matter of physics that it takes more energy to drive the same distance at higher speeds. So why do the Model S and X get better mileage at higher speeds? My guess is the type of motor used - induction. Induction motors have high losses at low power due to the need for excitation current. This makes them lousy at low power and even worse at low power regeneration. As I understand it, the Model 3 uses a permanent magnet motor, thus it needs no excitation current and is much more efficient at lower power levels and especially at regeneration.

 

I get that, and the point about the new motors is likely a part as well.
But doesn't it take more energy to accelerate a car from zero to 30mph than it does to maintain a 65mph speed?

 

That question doesn't makes sense, because it depends on for how long you maintain the 65mph speed.

Energy to accelerate a 5,000 pound car to 30 is 56.7 watt-hours. That's about how much a car like a Model S should consume to go a little less than a quarter mile at a steady 65mph.

 

That's not really a meaningful question it depends how long you are maintaining the 65mph.

At a constant speed there is power continuously required but the total amount of energy depends upon how long you maintain that speed.

For example the Model S has a mass of about 2300kg. 65mph is 29 m/s. Therefore it has almost precisely 1 million Joules of kinetic energy.

If the efficiency is 80% during acceleration this will require 1.2 million Joules from the battery.

If the power to maintain constant 65mph is 20kW (20,000 Joules per sec) the car will travel for about a minute (just over a mile) on the energy required to accelerate to 65 mph.

kevin

 

Absolutely, my apologies.
So to be meaningful, would it be more appropriate to compare identical times, or distance?
I lean towards time, but I know 'gut feelings' are incorrect more often than not.
If time, 5 seconds?

 

No, it's meaningless to compare acceleration/deceleration losses to rolling friction + air drag unless you know exact distances and speeds.

 

I think you misunderstand me.
Do you feel it would be better to compare initial acceleration and highway travel using the same time, or same distance?
One of those variables can be kept the same, but not both.

 

Neither - they don't even have the same units (impulse versus power).

 

Why call it an induction motor - (from the EE discussion board on tesla motors)

automotive - Why does a Tesla car use an AC motor instead of a DC one? - Electrical Engineering Stack Exchange
curious about the opinion that a Tesla is lousy at low power - in stating ;

really? traveling at a speed of ~30mph - the record range in a model S 100D, using 2 dirvers & many many hours - is well over 500 miles ... ie; >5 miles per/kWh - an increase of ~40% efficiency. Certainly one can write off a good amount of the increased efficiency to less wind drag, but blaming the motor as being less efficient doesn't hold water much for blaming the small/remaining efficiency percentage.
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Because the Tesla does.

Induction Versus DC Brushless Motors | Tesla

Tesla's 3-Phase 4-Pole AC Induction Motor -- Why Nikola Tesla’s 19th Century Induction Motor Is The Ideal Choice For The 21st Century Electric Car | CleanTechnica

Video: Primer on Tesla Model S Electric Motor | Inside EVs

 

Haha, now I see why the mistake. You quoted a decade-old blog site relating to pre model X & S, not a discussion among electrical engineers, and then quoted two websites that deal with electric cars, which aren't necessarily authoritative. Call me wacky , but I'll go with the EE's definition.

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