Ideal Speed for Efficiency

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slasher016

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#1
We've seen lots of numbers for highway speeds (i.e. the slower the better) for efficiency. But has anyone done any calculations (or real world tests) for the "ideal" speed overall? At which speed does the Model 3 have the most efficiency? This is of course assuming a flat road, minimal wind, etc.

I'd love to see a chart (and maybe it's out there) overlaying speed to wh/mile efficiency.
 

garsh

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#2
I don't believe that anybody has run an experiment yet. You'll ideally want an empty oval track, and lots of time. But people have posted some anecdotes in other threads.

I would expect the ideal speed for a Model 3 to be in the 12-20mph range.
 

Audrey

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#3
The slower the better; think like 25 MPH. This shouldn't be an issue unless you're eeking out on the bottom edge. If you put in your destination, the navigation will tell you to stay below speeds (like 65 or 55 MPH) to make it to the destination.

The model 3's estimated range was calculated in optimal weather (70-degrees Fahrenheit) with no wind, on a flat surface at 55 MPH.
 

Dogwhistle

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#7
Max range speed for the Model S is 22mph, probably similar for the 3, but haven’t seen a chart yet.
 

jsmay311

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#9
check out Sean Mitchell on you tube. He's starting a hyperbole trip today!
LOL! Dude brought along a foldable solar panel with a USB output to put on the dash and power his phone. :D:D:D

upload_2018-5-14_15-40-50-png.8741


I hope he doesn't get run over by a semi or cause any accidents while going 30mph on the highway for 600+ miles.
 

Joaquin

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#10
What about efficiency in time?

I mean, if going 85mph instead of 75mph to the next SC makes you arrive at, let's say, 5% battery instead of 20%, is the time saved more or less than the time spent in the SC charging that extra power?

Example, start a 200 miles leg with full 100% charged Model 3. The driving times at different average speeds are:
65mph -> 3:05
75mph -> 2:40
85mph -> 2:21

(I'm assuming a fully charged Model 3 can make 200 miles at 85mph)

So, how much is the energy consumption delta in these cases, and how long will be that extra time to charge the car at a SC?
 

slasher016

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#12
What about efficiency in time?

I mean, if going 85mph instead of 75mph to the next SC makes you arrive at, let's say, 5% battery instead of 20%, is the time saved more or less than the time spent in the SC charging that extra power?

Example, start a 200 miles leg with full 100% charged Model 3. The driving times at different average speeds are:
65mph -> 3:05
75mph -> 2:40
85mph -> 2:21

(I'm assuming a fully charged Model 3 can make 200 miles at 85mph)

So, how much is the energy consumption delta in these cases, and how long will be that extra time to charge the car at a SC?
This would be interesting to know.
 

PNWmisty

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#14
I'd love to see a chart (and maybe it's out there) overlaying speed to wh/mile efficiency.
The optimal speed for travelling a given distance is dependent upon how much current being used for ancillary functions like heating/cooling, headlights, radio, wipers, etc. If ancillary usage is very low, then the optimum speed for efficiency is also very low, probably around 15 mph. On the other hand, if ancillary usage is high, then the optimum speed for efficiency rises because faster speeds result in shorter travel time and less ancillary electrical usage. In this case, the optimum speed for efficiency is likely closer to 25 mph.
 

MelindaV

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#15
The optimal speed for travelling a given distance is dependent upon how much current being used for ancillary functions like heating/cooling, headlights, radio, wipers, etc. If ancillary usage is very low, then the optimum speed for efficiency is also very low, probably around 15 mph. On the other hand, if ancillary usage is high, then the optimum speed for efficiency rises because faster speeds result in shorter travel time and less ancillary electrical usage. In this case, the optimum speed for efficiency is likely closer to 25 mph.
heating/cooling is the only thing that takes any measurable power. the lights/radio/wipers/etc use such a small amount vs the power needed to move the car it shouldn't be a consideration.
 

PNWmisty

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#16
heating/cooling is the only thing that takes any measurable power. the lights/radio/wipers/etc use such a small amount vs the power needed to move the car it shouldn't be a consideration.
That's true from a practical, everyday perspective. On the other hand, when hypermiling at very low speeds like 15 mph, those ancillary functions add up to be not only measurable but considerable. Even turning up the stereo to a high level has a measurable impact.
 

garsh

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#17
heating/cooling is the only thing that takes any measurable power.
I'll take that one-step further. Cooling is pretty efficient nowadays. I have no problems running the air conditioning in my Leaf - it affects my range by less than a mile. But I've actually disabled the heater so that it never runs.

But I agree with @PNWmisty - these don't make much of a difference in day-to-day use, but can become important when hypermiling. When I hit turtle mode in my Leaf, you can bet that I'm turning off the radio, fan, and lights in order to eek out several more yards to make it to a charging station. :)
 

JoeP

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#18
I calculated this for my Toyota Rav4EV at one point (the optimimum speed to drive for least speed over distance).
So for instance, for 486 miles to LA last week, i *averaged* 60mph, driving 75mph on the freeway and supercharging for about 45 minutes in the M3. I dont know if thats optimum or not, but it was the fastest i felt responsible driving on I-5. There were a *few* cars faster.

However, i'm driving a 1900 mile trip to Houston soon, and would love to know this. (in Texas you have the option of driving up to 80 on their interstates, maybe faster). IS it better to do that, or stay with 75mph? (ie. do you waste more time charging than you save going faster)?
Since the range on my car has decreased from ~300 to ~275miles now (indicated, i dont know what the "real" range is) since v10 arrived, i'm not sure if i can make all legs while driving 80 or more.
(although this car certainly feels *safe* driving at those speeds.)

I will be doing 5000 miles in the car roughly between late October/Early November so i'll be experimenting. (II'm going to visit a bunch of friends with my Tesla...)
-jcp-
 

Dr. J

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#19
I calculated this for my Toyota Rav4EV at one point (the optimimum speed to drive for least speed over distance).
So for instance, for 486 miles to LA last week, i *averaged* 60mph, driving 75mph on the freeway and supercharging for about 45 minutes in the M3. I dont know if thats optimum or not, but it was the fastest i felt responsible driving on I-5. There were a *few* cars faster.

However, i'm driving a 1900 mile trip to Houston soon, and would love to know this. (in Texas you have the option of driving up to 80 on their interstates, maybe faster). IS it better to do that, or stay with 75mph? (ie. do you waste more time charging than you save going faster)?
Since the range on my car has decreased from ~300 to ~275miles now (indicated, i dont know what the "real" range is) since v10 arrived, i'm not sure if i can make all legs while driving 80 or more.
(although this car certainly feels *safe* driving at those speeds.)

I will be doing 5000 miles in the car roughly between late October/Early November so i'll be experimenting. (II'm going to visit a bunch of friends with my Tesla...)
-jcp-
Air resistance is proportional to the cube of speed, so going 80 MPH is not going to be optimal from an efficiency perspective. To answer your question, you have to consider charging time, charging opportunities, ideal SoC, etc. I would game it out with abetterrouteplanner.

Edit: website address corrected.
 
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