Model 3 high speed range

[Yggdrasill]

I've been playing around with a spreadsheet with the range for the Model 3. Particularly I was interested in how the range would be at higher speeds, due to the low aerodynamic drag, and I thought you guys would be interested in it as well.

First constant speed cruising in 20C (68F), with no cooling or heating:

And also in -10C (14F), with 2 kW of heating:

I didn't put that much effort into getting the figures for the comparison cars exactly right, but they should be in the ballpark.

I think I can live with this.

 

[FlatSix911]

I think you are in the ballpark with your estimates ... here are the Tesla numbers for the Model S

Model S Efficiency and Range
Driving Range for the Model S Family

 

[tsla007]

according to this chart- at 63 degrees or whatever-the 75d will get about 300 miles at 70mph. that's about 4m/kw.
Seems a little high to me. Maybe 3.75 max in reality. Still that comes out to 281m. I can live with that.

 

[Haxster]

This spreadsheet is incomplete! It only goes up to 217 mph.

What if I'm running late to a meeting and I need to go faster, but worry that I'll run out of electrons?

Seriously, nice work. Thanks!

 

[tsla007]

At haxster use hyperloop.

 

[McRat]

As you go faster and faster, the force against the front region of the car in front of the CG has two effects:

1) The pressure tries to rotate the car about it's CG, this is called spinning when you exceed the front tire traction and the tires slide.
2) When the frontal pressure exceeds the available traction, and the drive wheels just slip. Sometimes you just fishtail, other times you spin depending on the vehicles shape. As soon as you fishtail put it in neutral (to avoid more tire slip), and/or pop the chute.
3) Cars are shaped similar to airfoils, they tend to lift. It takes either serious weight or downforce to keep the tires on the ground. Normally, when lift occurs, the drive wheels spin first, and you spin. As the car goes broadside, it lifts completely into the air.
4) Lift can increase your drag past what your aero charts show. You are best off putting spoilers and splitters on an burning up the power as downforce rather than risk lift. Lift is an inherently unstable situation, like balancing a pencil vertically on your finger. Lift makes lift which make more lift.

 

[jsmay311]

Don't you also get higher rolling resistance in cold temps?

And lower mechanical efficiencies from more-viscous lubricants?

And also increased battery internal resistance / lower usable battery capacity, and/or greater battery heating power demands?

 

[LargeHamCollider]

I think your mass is a bit high and your rr is a bit low but your results look about right.

 

[alseTrick]

A 55kWh 3 could go 200 miles at 78mph?

 

[jsmay311]

A 55kWh 3 could go 200 miles at 78mph?

Apart from Tesla insiders, no one can possibly know. TBD.

But I would still venture a guess that it's unlikely.

 

[Yggdrasill]

A 55kWh 3 could go 200 miles at 78mph?

It is *very* aerodynamic, and at high speeds, that's the most important factor by far. As you can see from the spreadsheet, the aerodynamic drag accounts for about 75% of the total drag at 78 mph.

But are these relatively optimistic numbers? Yes. This is on a level road, with tires rated as class A for rolling resistance. You also aren't running the A/C at 68F, which you very likely would be if the sun were out. Windows are closed, there's no head wind, tire pressure is ideal, etc.

 

[Yggdrasill]

I have some thoughs on how to improve the spead sheet, but we'll see if I have time today. I have plans with my wife.

 

[Yggdrasill]

Don't you also get higher rolling resistance in cold temps?

I don't think so, not significantly. And if you're using winter tires, they actually have *less* rolling resistance. (They're often narrower, intended to get higher ground pressure. Higher ground pressure allows the tires to push snow and sleet more effectively out of the way.) But if there's sleet or snow in the road, that will impact range significantly.

If it's snowing or raining, that also affects range.

And lower mechanical efficiencies from more-viscous lubricants?

Seems likely, but only for the first few minutes of the drive. Once the lubricant gets warmer the effect will pass.

And also increased battery internal resistance / lower usable battery capacity, and/or greater battery heating power demands?

The battery supplies less energy when it is cold, but the energy doesn't disappear. It goes into heat, which means the battery gets warmer, and the consumption drops back to a lower level again. I have added the field for heating/cooling. At the start of a drive the power may be higher, ~5 kW, but then it drops once the car gets warmer. The 2 kW I added for heating is an *average*.

 

[widodh]

The 195Wh/km seems low for 125km/h, but that's me being used to a Model S all year round.

Lower consumption means 'faster' charging, so that's very nice to have.

I am happy if I get a true 350km out of my battery any day. More is always welcome though!

 

[Yggdrasill]

I think your mass is a bit high and your rr is a bit low but your results look about right.

I assumed 1850 kg for the car plus 150 kg for two people (or one person pluss luggage), and for the other cars I also added 150 kg. The 55 kWh version will weigh less, but I don't think I adjusted for that.

I used the roling resistance value for class A rolling resistance tires. They must have less than 0.0065, at least here in Europe.

 

[arnis]

250km/h will be the limit for AWD models with bigger capacity battery (70kWh for example).
Someone somewhere said that Model 3 drive unit will be slightly more efficient than Model S/X rear motor.
That should translate to better efficiencies, especially at higher speeds.

 

[jsmay311]

Don't you also get higher rolling resistance in cold temps?

I don't think so, not significantly.

Well, it was really intended as a rhetorical question. The answer is "yes". Colder rubber = stiffer rubber = higher rolling resistance.

 

[Yggdrasill]

Well, it was really intended as a rhetorical question. The answer is "yes". Colder rubber = stiffer rubber = higher rolling resistance.

Tried looking for good data, and I couldn't find any. There does seem to be a correlation between temperature and Crr, but my impression from the information I could find is that it's related to tire pressure. Lower temperature = lower tire pressure = higher Crr

If you have tire pressure sensors and pay attention to them, that isn't an issue. And also, like I said, with winter tires, rolling resistance is usually lower. In really cold temperatures, you should use winter tires.

 

[alseTrick]

It is *very* aerodynamic, and at high speeds, that's the most important factor by far. As you can see from the spreadsheet, the aerodynamic drag accounts for about 75% of the total drag at 78 mph.

But are these relatively optimistic numbers? Yes. This is on a level road, with tires rated as class A for rolling resistance. You also aren't running the A/C at 68F, which you very likely would be if the sun were out. Windows are closed, there's no head wind, tire pressure is ideal, etc.

I don't know much about the equations or inputs used to determine that range at that speed. But it's more than I was reasonably expecting. Hopefully you're right, but I'm still not going to expect it.

What would the approximate EPA range be on that vehicle?

 

[Yggdrasill]

I don't know much about the equations or inputs used to determine that range at that speed. But it's more than I was reasonably expecting. Hopefully you're right, but I'm still not going to expect it.

What would the approximate EPA range be on that vehicle?

Probably around 240-250 miles.

I've been working a bit on the spreadsheet, and while it's not quite ready yet, one thing that surprised me is how big the impact can be from a head wind. Even a little head wind has a meaningful impact, and if you're talking about gale force winds or above, it absolutely obliterates range at high speeds!

I'll likely post some scenarios later.