How Tesla Calculates Range (hidden buffer)

[AdamMacDon]

No, I'm not suggesting an option that would include choosing which of the various distance measurement estimates to display - just a 3rd option under the percentage/miles remaining interface. It's one addition virtual button - that's it.

Yes, this would make the car similar to most other vehicles on the road. In this instance, I'd suggest that would be a good thing, as everyone already knows how those estimates work, and that the estimate will change based on recent energy usage.

Yes, this exactly! I'm baffled how this basic option that even my 2007 Crown Victoria had is missing.

I think I now understand what you are saying and I have seen this a lot from people coming from ICE cars or other EVs.

Other EVs have exactly what you are saying - they have an imaginary boundary at X km back from the calculation point, take the consumption and capacity and divide it to reprsent some remaining miles/km. That is called a GOM or guess-o-meter, because it is exactly that - a guesstimation.

I don't see how this will be helpful to you though - on your way to your work it will show you double the amount of range since it will take your last trip which was down - not useful.
On your way down it will show you half of the range you have since it will use the way to your work as a reference (uphil), but you will be driving downhil...

Tesla has it better with factoring elevation and weather and speed.

I think most people are just too familiar with how the ICE cars worked, but the thing is that ICE cars are more linear than EVs - they do not regen and the HVAC is more or less coming from the motor heat. And they are very dumb.
EVs have regen and some of the secondery consumptions like HVAC could hurt the range. I think what Tesla does is pretty good, especially the trip meter estimation.

As a UI/UX designer, how will you design the screen so that you still can have the energy graph in direct sight and still maintain some sort of range estimator?
If I were to design it, I would have the energy graph accessible with one click and not 2-3 clicks and have it overlay somewhere at the bottom, maybe where the trip meter is. That's it. But I will still want to keep the way the calculation is done now.

You'd be correct if it was a dumb system that only based the information on your last drive. If it based the information off your last 400km driven, it's a completely different story and leagues more accurate than EPA ratings. My commute to work is 7km, so even if it was only a 50km timespan for the average to be drawn from, that still covers at least 8 trips to and from work. Ideally I'd say the average should be calculated on several hundred kilometers for the best results. Like Zcd1 said, the data for this is already there, you can create a trip odometer and it tracks your average Wh per km. Some math and you can get your actual range for your rated SoC. Sure one can do the math to keep the mind sharp, but when driving it's probably better you focus on the road and let the giant computer on wheels do it for you (if only it was an option)!

 

[lnsh]

I find this thread super-interesting. I think most of us really never concerned ourselves with this level of detail w/ICE vehicles... as the density of 'refueling' opportunities lends itself to less worry. I recall days of my youth were I'd drive days/weeks with the gas gauge at or below the E line. Over the years, you sort of learned how much 'reserve' a particular gas gauge really had... as a battery degrades a bit over time -- the mental math gets a little more complex and challenging.

 

[ran349]

The calculation of typical range you see next to the battery icon is based on a specific EPA constant (or Tesla constant) which is different for each model - 153Wh/km for Model 3 LR AWD or 245Wh/mile

Based on your SMT data, it looks like your constant can not be 153 exactly, but something a little lower, based on the following:
SMT NominalFullPack = 75 kWh, and assuming 153 constant, then,
75/.153 = 490.196 rated km at 100% SOC.
Your car SOC reported 99%, so since that is a rounded number, the highest it could be is 99.5% (or it would display 100% on the car).
It would be more accurate to use the SMT calculated value, but that information is not available in your readout.

Given the above, the maximum rated miles the car would display based on a 153 constant, is then,
490.196 x 99.5 % = 487.75 rated km, which rounds to a display value of 488 km.
However, your display was reading 489 km, which doesn't match up.
This would imply a constant somewhat less than 153. And if 245 is the correct constant value for miles, the direct conversion would give
152.23565 for km.

Not that any of this really matters.

 

[AdamMacDon]

I find this thread super-interesting. I think most of us really never concerned ourselves with this level of detail w/ICE vehicles... as the density of 'refueling' opportunities lends itself to less worry. I recall days of my youth were I'd drive days/weeks with the gas gauge at or below the E line. Over the years, you sort of learned how much 'reserve' a particular gas gauge really had... as a battery degrades a bit over time -- the mental math gets a little more complex and challenging.

One of those guys, eh? I had a friend that did that and cooked his fuel pump really good haha. But for sure the difference of infrastructure makes a world of difference how much attention people pay to something. Whether ICE or EV, I find EPA ratings consistently useless however. I drive with a lead foot so I am to blame. People who measure ratings for the EPA must drive like saints, in a flat area, in a straight line, on a mild day with no climate control on, I swear, haha.

 

[TimothyHW3]

Based on your SMT data, it looks like your constant can not be 153 exactly, but something a little lower, based on the following:
SMT NominalFullPack = 75 kWh, and assuming 153 constant, then,
75/.153 = 490.196 rated km at 100% SOC.
Your car SOC reported 99%, so since that is a rounded number, the highest it could be is 99.5% (or it would display 100% on the car).
It would be more accurate to use the SMT calculated value, but that information is not available in your readout.

Given the above, the maximum rated miles the car would display based on a 153 constant, is then,
490.196 x 99.5 % = 487.75 rated km, which rounds to a display value of 488 km.
However, your display was reading 489 km, which doesn't match up.

You are nitpicking here. If you see my video there is some discrepancy between the displayed 489km on the battery and the 487 calculated by the energy graph screen. 487 was indeed displayed at 74.9kWh before I started. There is obviously some rounding errors both in the calculation of rated vs the energy graph. Furthermore the energy graph and the battery indicator are not updating simultaniously. Especially when the car is not moving. I found that the energy graph is updating faster than the battery indicator, a couple of seconds faster, let's sat 10 vs every 30 seconds.

And the 75 dropped to about 74.9 (there is 5 minutes difference where I was sitting in the car)

Plus there is something not 100% correct with my BMS, I think it reports 0.5kWh more than I could get out of it in the test. Also there was a difference of 0.2kWh between ideal and nominal, which happens when the battery is not quite up to temperature (it was a cold morning)

All in all, wether it is 153 or 152.5 it doesn't really matter for this test...

No, I'm not suggesting an option that would include choosing which of the various distance measurement estimates to display - just a 3rd option under the percentage/miles remaining interface. It's one addition virtual button - that's it.

I am not quite sure how this will work really, from UI standpoint. Another "virtual button" is the energy graph.
If you mean to be displayed underneath it that will look strange to see 500km on top and 350km on the bottom. This will confuse people even more than what we have now.
You know the old saying - never go with two compasses at sea - either one or three...

I think you guys are just too used to the way things were, but as I said, EVs work differently and have regen etc. so it can't be as straight forward as it was with ICE. Especially when you have all these different places the EVs are being driven.

 

[TimothyHW3]

Yes, this exactly!

You'd be correct if it was a dumb system that only based the information on your last drive. If it based the information off your last 400km driven, it's a completely different story and leagues more accurate than EPA ratings. !

Sorry, but it might work for you, but how would that be accurate or more accurate than even EPA if I just did a highway speed run of 150mph (which I do now and again) and then want to commute the next day at 50mph?! I guess to each their own, but this will be especially dumb system and I really hope Tesla never implements it (not that I think they will...)

Actually the EPA rating thing works perfectly fine for most of the use cases where the car is mostly used - California and mainland Europe, Holland for example (outside of Germany)
If you live anywehre there, the EPA rated range will be accurate 98% of the cases.

It will obviously not work in hilly sections and cold conditions, but that is to be expected.

 

[AdamMacDon]

Sorry, but it might work for you, but how would that be accurate or more accurate than even EPA if I just did a highway speed run of 150mph (which I do now and again) and then want to commute the next day at 50mph?! I guess to each their own, but this will be especially dumb system and I really hope Tesla never implements it (not that I think they will...)

Actually the EPA rating thing works perfectly fine for most of the use cases where the car is mostly used - California and mainland Europe, Holland for example (outside of Germany)
If you live anywehre there, the EPA rated range will be accurate 98% of the cases.

It will obviously not work in hilly sections and cold conditions, but that is to be expected.

I think you have to be realistic that most drivers do not vary their driving speed from 150mph (+250kmph?!) to 50 mph on the same commute often (also I'll point out the EPA rated distance gauge is completely irrelevant at consistent speeds of 250kmph, you'd be lucky to get 280km on a charge at that speed). Sure I do occasional pulls to around 130 KMPH, but usually I let off pretty quick. You may have the privilege of living near a section of autobahn that is speed unrestricted (I saw the sign in your video, jealous), however most drivers do not. Germany is a small country and most countries have highway speed limits around 120kmph (only about 100kmph here in Canada, lucky me). Obviously there are fringe cases, which is why I simply stated I'd like the OPTION of average consumption over the last 400kms. People can still use EPA if they want, but it'd be nice for those of us who prefer a more accurate number and have the misfortune to live in mountainous areas that get snow (and also have no speed unrestricted areas). As it stands, EPA rating is useful for me about 3 months of the year, and only if I drive like a saint, no 250kmph pulls for me.

 

[Zcd1]

I am not quite sure how this will work really, from UI standpoint. .

The small percentage/mileage display to the upper right of the speedometer - include a new button on the screen that chooses what's displayed there to display the remaining range based on the most recent 30 miles - similar to what many ICE vehicles have offered for at least 20 years.

 

[TimothyHW3]

I think we are going off-topic here. The topic is the hidden buffer and how Tesla dispays 100% and then hides part of it below 0%.

I have thought about it and it makes perfect sense for Tesla and even from UI standpoint.
If they show you the rated range at true 100%, when you are at 0% (a lot of people do) you are closer to true 0% than you are now (5%)

And if they just show you just 96% of your range, ie 475km or 298miles, you will not know that you have another 25km buffer and they have to communicate this to you somehow.

Plus it is bad marketing.

So anyways, we know how they calculate and we now know how they display the range.

And for some people that is not even interesting as they never drive it down below 20% before charging and hardly make road trips.

 

[Zcd1]

I think we are going off-topic here.

I don't think we're off topic at all. You're suggesting mental gymnastics to estimate out how much range is actually left.

I'm suggesting that the car display, front and center, and at all times, how much range it estimates is left (since it knows this anyway - the display is just buried 2 layers deep and obscures the NAV map whenever it's active).

Two approaches to the same goal.