Method to calculate/extrapolate battery capacity from trip consumption

[willow_hiller]

This is what I was wondering too, but it’d need to be pretty far off to drop it from 240 to 192.

But it seems like in all Model 3 there’s definitely some weirdness going on with the screen indication of what’s usable verses what the EPA application says. No one is seeing 55kWh nor 78kWh.

Is it possible there's a large bottom buffer? Elon tweeted this in May 2018: Elon Musk on Twitter

"A Tesla has a usable reserve of 5 to 15 miles range even after the battery reads “empty”. This will not hurt the pack."

 

[AlanSubie4Life]

Is it possible there's a large bottom buffer? Elon tweeted this in March: Elon Musk on Twitter

"A Tesla has a usable reserve of 5 to 15 miles range even after the battery reads “empty”. This will not hurt the pack."

Yes. He had another Twitter post (for some reason I've been quoting 6 miles but I guess it's 5, I was misremembering):

Elon Musk on Twitter

Still, it doesn't explain the atrocious results. He should try someone else's car.

 

[Zoomit]

Is it possible there's a large bottom buffer?

I theorized the Model 3 has a large bottom usable buffer, probably a year ago now. But in this SR+ example it’d need to be 48 mi to bring the test result back up to the EPA range. That’s ~10kWh and just doesn’t make sense.

Edit: Found it, I was thinking a 5.6kWh reserve, but that still seems exorbitant. This was Feb ‘18 and we don’t seem to have learned much since then. Supercharger speed: 116kW

 

[Zoomit]

@AlanSubie4Life Not sure if you realize it or not but 78,269 Wh / 333.8 mi = 234.5 Wh/mi. Those numbers are from the first published 3 LR RWD EPA test. Calculating a ~234 Wh/mi constant from the car would make me infer that’s the source.

 

[AlanSubie4Life]

@AlanSubie4Life Not sure if you realize it or not but 78,269 Wh / 333.8 mi = 234.5 Wh/mi. Those numbers are from the first published 3 LR RWD EPA test. Calculating a ~234 Wh/mi constant from the car would make me infer that’s the source.

That would make some sense, as for why Tesla chose this constant. I can't really say it's exactly 232Wh/rmi due to rounding errors; it could be closer to this 235Wh/rmi. And that's just the way it behaves on my car; I don't know whether other variants behave the same way.

I noticed there is a massive thread on what is the "actual capacity" of the Tesla batteries. It is quite contentious. Fortunately I don't really care about that. (There's a big debate whether you can get the since last charge meter to show 78kWh used with zero net elevation loss.) Anyway, I just want to know what Wh/mi (indicated) I need to get to achieve the rated range, and the constant makes that possible. The constant may or may not be "real" Wh/rmi, but I don't care.

 

[AlanSubie4Life]

In the video Alex states that he routinely goes over a 2000’ pass for his commute. I wouldn’t read anything into the 267 Wh/mi number.

I did not bother to watch the video, just read his article. How many miles does he have with that 267Wh/mi number?

It has not really been that cold, so I would not expect it to be pushed up that much by heating use, but maybe he runs the car warm.

I have a lifetime of 285Wh/mi and 265Wh/mi over the last 300 miles in a P3D+ and I am not really trying that hard to be efficient, and I have ~800’ of hills every day.

Tires cost me about 30Wh/mi. I figure the AWD costs me another 20Wh/mi. And then the SR+ is lighter. So I’d expect it would be possible to routinely get 220Wh/mi with a little bit of care, even with those hills. Without the hills I doubt that 200Wh/mi would be that difficult.

So to me 267Wh/mi seems very high unless of course it includes a lot of winter use...but it is an SR+ so it is brand new.

Surprised there isn’t a whole thread about this somewhere here...maybe there is...?

 

[willow_hiller]

I did not bother to watch the video, just read his article. How many miles does he have with that 267Wh/mi number?

It has not really been that cold, so I would not expect it to be pushed up that much by heating use, but maybe he runs the car warm.

I have a lifetime of 285Wh/mi and 265Wh/mi over the last 300 miles in a P3D+ and I am not really trying that hard to be efficient, and I have ~800’ of hills every day.

Tires cost me about 30Wh/mi. I figure the AWD costs me another 20Wh/mi. And then the SR+ is lighter. So I’d expect it would be possible to routinely get 220Wh/mi with a little bit of care, even with those hills. Without the hills I doubt that 200Wh/mi would be that difficult.

So to me 267Wh/mi seems very high unless of course it includes a lot of winter use...but it is an SR+ so it is brand new.

Surprised there isn’t a whole thread about this somewhere here...maybe there is...?

Just under 1000 miles. He also states that he keeps regen on low for his commute, so that may be a contributing factor. But for his range test he said the regen was on standard.

 

[AlanSubie4Life]

He also states that he keeps regen on low for his commute, so that may be a contributing factor.

With a 2000 foot hill on his commute, I would think that would be a contributing factor... I am sure he explains why, but it seems completely nonsensical. And I can’t think of a good reason.

 

[willow_hiller]

Just noticed his lifetime wh/mi matches up pretty well with the test. Lifetime of 263 wh/mi, and in real-life range test his table shows 3.85 mi/kWh which translates to 259.7 wh/mi.

So somehow his commute with a mountain pass has the same efficiency as a flat range test?

 

[willow_hiller]

And now Inside EVs is running with the story: Perhaps The EPA Is Way Off On Tesla Model 3 Range Estimates?

This is a mess.

 

[willow_hiller]

Dug up this old thread to post an additional "real world" range test as reported by InsideEVs: Tesla Model 3 Standard Range Plus Real-World Highway Range Test

272 miles from the SR+ on 78 mph cruise control with the AC set to 68. Alex on Autos really has some explaining to do...

Edit: Just watched through the video, he used 125% of the battery to go 272 miles. So for 100% he got 217 miles.

 

[AlanSubie4Life]

For the first leg he averaged 70mph (most freeway done at 78mph), did 140.3mi @ 248Wh/mi, went from 95% to 28% battery (67%). Trinidad & Colorado Springs are the same elevation. Looks like he had minimal traffic so no significant drafting. Really quite an excellent result - that's as fast as you really would ever need to go without getting a ticket. (Obviously you can go slightly faster in some parts of Nevada where speed limits are 80mph...)

I didn't bother to watch the rest because it was too confusing; he wasn't trying to show what the range was as far as I could tell.

From the first leg, without entering the reserve, it looks like you could do:

140.3/0.67 => 209 miles on a 100% to 0% discharge, without entering the reserve.

Alex DEFINITELY has some explaining to do. I think if you drop the freeway speed to below 70mph you'll hit 240miles without the reserve. Just a rough estimate. To get only 192miles...I have no idea.

An additional conclusion: 140.3mi*248Wh/mi / ( 0.67 * 240rmi) = 216Wh/rmi

This is the constant I will use for the SR+ from now on. The constant in the P3D & AWD is 230Wh/rmi.

So, if you can get to 216Wh/rmi on the display, you'll get 240 miles of range...and to do that I would guess you'd need to drop your speed to below 70mph.