Range at sustained high speeds

[Dangerous Fish]

I've had a look through a few threads on range. There isn't much data I can find regarding what happens to range on journeys where one can sustain high speeds (above 80mph).

Does anyone have any practical experience or a way to calculate what happens when you do sustained speeds of 90-100mph?

 

[John1969]

The drag coefficient of the car at high speeds is velocity squared so the air is pushing back harder on the car at higher speeds. At those speeds you will eat your range. Gas cars are the same way.

Force of drag=coefficient X (density X Velocity squared )/2 X reference area

 

[Dangerous Fish]

Indeed. That's why I'm asking if anyone has actually done it so I can get an idea of the real world numbers.

 

[roblab]

I've had a look through a few threads on range. There isn't much data I can find regarding what happens to range on journeys where one can sustain high speeds (above 80mph).

Does anyone have any practical experience or a way to calculate what happens when you do sustained speeds of 90-100mph?

You've probably seen the graphs. I don't find any on the X, but several on the S and Roadster, which are similar:
The cars get best mileage at around 30 (I recommend cruise control). At near 60 they get their EPA rated range. At 100 or so, range is about half of EPA.

Here where I live, Freeway speeds are 70 and people do 80 all the time. Range drops rapidly from EPA values. I usually charge an extra 100 miles for buffer and then drive a little slower than I might until I see my range is settling down on the trip meter and then go faster if I dare.

The car has no problem sustaining 80+. I would think there might come a point where the battery cooling would have to kick in, which takes battery power. Depending on weather and terrain and temperature, you can easily drop to one third of what you expect. You save time cruising near the lower end of traffic flow and then spending less time charging when you stop.

 

[BerTX]

If you are traveling between superchargers, going faster than 80 mph is actually slower due to the increased time required at the next supercharger.

 

[J1mbo]

Suggest you have a play with EV Trip Planner.

 

[widodh]

I took a 210km trip through 4C weather last weekend. Averaged 260Wh/km driving 140km/h

To miles: 131 miles, 88mph, 416Wh/m.

The whole trip consumed roughly 55kWh

 

[Dangerous Fish]

Suggest you have a play with EV Trip Planner.

Thanks, that's just the job. How accurate do people find it?

 

[Zooomer]

My 100 uses ~475 watts going 80 in 10F. So just over 200 mile range roughly.

 

[oktane]

My 100 uses ~475 watts going 80 in 10F. So just over 200 mile range roughly.

This is my experience as well. For planning purposes I use 500 Wh/mi per mile if you drive fast. This leaves a sufficient buffer.

 

[Rocky_H]

Thanks, that's just the job. How accurate do people find it?

Most reports, including my own experience is that it is extremely accurate if they do have your specific vehicle to choose to have really good energy modeling data for it. If it's a new car version that they don't have a listing for, and you're having to approximate by picking something else similar, I don't know how far off those get. I had made a gutsy call leaving my garage charged up full when the car said I would arrive with -2% remaining and charge was needed to reach my destination. But I knew EVTripplanner had said it would work, so I went for it, and it was fine--238 miles. EVTripplanner had correctly realized that the route was taking a smaller highway with the lower 55mph speed limits, which helps efficiency a lot.

 

[David99]

Does anyone have any practical experience or a way to calculate what happens when you do sustained speeds of 90-100mph?

I just drove through South Dakota where the speed limit is 80 and most people drive 95. I used about 420 Wh/mile. It was cold so I had to run the heater as well.

 

[randvegeta]

I've only just bought my 2014 S 60, and at 100% I get 285km | 177Miles of rated range. It's cold here in Lithuania, but the range is just about achievable driving around 90km/h | 56mph.

I'm hoping that in the summer, my rated range, and driving efficiency will improve!

Lithuanian summers are around 20-25c | 68-77f, and it's mostly flat (very small gently sloping hills). No super chargers, and for the trips I'm planning, not really any fast DC (Chademo) chargers either.

There is a particular stretch of highway that I am trying to figure out how fast I could drive but still reach my destination. There is a 230km journey of which about 220 is on the highway. At the end of the highway is a Chademo charger. I KNOW I can easily make the trip at 90-100km/h (even with the A/C on) but can I drive at 110, 120 or even 130? The speed limit on the road is 130 and everyone drives at 140+.

Main concern is driving comfort, so 1 must assume modest A/C usage, or windows down (which increases drag, reducing efficiency). But I don't want to drive slower than lorries if I don't have to.

Given even -20c temperatures, if I shut off climate control, drive at 80-90km/h, EVEN WITH wind, ice and snow, I am confident I could make that journey (I have not tried). But I can justify driving slower in the winter simply for safety reasons.

Will the 40 degree increase in temperature afford me significantly greater efficiency that I could have a relatively uncompromising drive in the summer? Being 20-25c, it won't be so hot that the A/C will need to work very hard. I will also change to summer tires with a higher PSI to reduce rolling resistance, and of course with no ice/snow and lower air density, and hopefully no rain, I am really hoping to see marked improvements.

Anyone have any REAL data on wh/km (or wh/m) for summer driving at speeds ABOVE 100km/h (60mph)?

 

[Naonak]

If you are traveling between superchargers, going faster than 80 mph is actually slower due to the increased time required at the next supercharger.

How do you figure this? The SuperCharger charges your car faster than you can drive - so as long as you can make it to the next Supercharger, drive as fast as you want.

If you charge at a rate of 374 miles an hour to start and taper off to even 100 miles an hour, as long as you are driving 100 mph or less (actually more, if you average it out), then you have a net gain at the supercharger.

 

[David99]

How do you figure this? The SuperCharger charges your car faster than you can drive - so as long as you can make it to the next Supercharger, drive as fast as you want.

It depends. If the distance between two Superchargers is longer and you have a smaller battery, you end up having to charge to a high level which adds time to the overall charge time.
The energy usage goes up dramatically with speed so there is a point where going faster uses so much energy that charging will slow you down overall.
I can't find it right now, but someone did an example of about 115 miles between two Superchargers and a Model S 85. Around 80 mph was the ideal speed. But with a larger battery and a shorter distance between Superchargers and especially with the new batteries that sustain higher charge speed longer to higher levels, you can go a lot faster.

 

[David99]

Anyone have any REAL data on wh/km (or wh/m) for summer driving at speeds ABOVE 100km/h (60mph)?

EVTripping.com is pretty accurate.

 

[Naonak]

It depends. If the distance between two Superchargers is longer and you have a smaller battery, you end up having to charge to a high level which adds time to the overall charge time.
The energy usage goes up dramatically with speed so there is a point where going faster uses so much energy that charging will slow you down overall.
I can't find it right now, but someone did an example of about 115 miles between two Superchargers and a Model S 85. Around 80 mph was the ideal speed. But with a larger battery and a shorter distance between Superchargers and especially with the new batteries that sustain higher charge speed longer to higher levels, you can go a lot faster.

The only scenario where I can imagine this is true is if you have to charge to > about 92% to get to your next stop, but even then it's questionable. You can figure this out yourself fairly easily though ... if you look at your overall average charge rate at the end of a charge, if it reads faster than you can/will drive, then it's better to drive fast and charge longer. If, just before you unplug, it says your charge rate is 120 mph, then you come out ahead charging longer and driving faster. If it says 70 mph at the end, then drive slower.

I've never seen my charge rate go below 100 mph, even when topping up to 100%, though, so as long as I drive slower than 100mph, it's a net gain.

 

[Rocky_H]

I've never seen my charge rate go below 100 mph, even when topping up to 100%, though, so as long as I drive slower than 100mph, it's a net gain.

You may also be forgetting:
Getting off the highway, turning onto the other street, waiting at the stop light, going down this other street, waiting at another stop light, finding the Supercharger in the parking lot, etc. etc. It's frequently a 5-10 minute thing each way to get to and from the Supercharger, so each stop does have some extra overhead.

 

[Moonwick]

You may also be forgetting:
Getting off the highway, turning onto the other street, waiting at the stop light, going down this other street, waiting at another stop light, finding the Supercharger in the parking lot, etc. etc. It's frequently a 5-10 minute thing each way to get to and from the Supercharger, so each stop does have some extra overhead.

For real. I can't wait until Superchargers (or an equivalent alternate-DCFC option) are located at rest areas right along the highway.

 

[brianman]

I'm hoping that in the summer, my rated range, and driving efficiency will improve!

Random observation...

I highly recommend people buy their Tesla vehicles in the winter. The benefit is that you calibrate yourself to winter driving, which makes summer driving quite relaxing. Doing the reverse (learning/calibrating to summer and then driving in winter) can be unsettling.