How Is Range Calculated ?

How Is Range Calculated ?

I just took delivery of S100D and the energy display shows a HUGE spike at about 1 or 2 miles (before I took delivery) so that the average over the first 15 miles is 560 whrs/mile - what if any is the effect of this on the battery range display ?

Bighorn | 03. November 2019

None, if I’m following. Range depends on what’s stored in the battery, not what’s happened before that.

bishoppeak | 03. November 2019

Vampire drain while the car sat made calculated mileage unrealistically bad. Once you drive 30 or 40 miles it should readjust

marcustcohn | 03. November 2019

OK - let me try this another way - if a battery is charged to 90 percent how does that reflect in miles - and are these rated miles or what ?

Bighorn | 03. November 2019

90% is a fixed proportion, obviously and one can toggle that to a distance in rated miles on the display screen

tes-s | 03. November 2019

The following in my opinion based on 6 years of experience with my MS, 1 year of experience with my MX, and reading thousands of posts on the topic. It is just an opinion - I have no information about the algorithm used by Tesla.

When you charge to 90%, 90% of the total usable capacity of the battery (measured in kWh) is available for your use. Over time the battery will degrade, so that 90% will be a lower number of kWh and your rated miles at 90% charge will decrease. I have about a 9% reduction in my 6-year-old MS after 172,000 miles.

Rated miles is a calculation based on a constant.

Rated miles = (kWh available) * (rate miles per kWh constant)

The contant is based on your model car, and the firmware version. When Tesla releases a firmware version that makes the car more efficient (extends the rated range), the constant changes. Tesla could also release a firmware version that makes more (or less) kWh available from the battery. This would also affect the rated miles when you charge to 90% since more (or less) kWh would be available.

Darthamerica | 03. November 2019

@Tes-s it does seem like the constant changes. But the energy graph dotted line in the energy graph stays the same. I also think they changed it for Performance cars as well. When I originally got the latest car, it had ~265 @100%. But on the website there used to be fine print saying 21” tires accounted for ~5 or 6%(I forgot the exact number) less range. So if they aren’t changing the constant the numbers would be off. Anyway efficiency was originally quoted at 310Wh/mi and lifetime on this car after 90,000 miles is 319Wh/mi.

marcustcohn | 04. November 2019

@tes-s That makes sense --- but my brand new long range Model S100 shows 320 miles at 90 percent - that would be 355 miles at 100 percent. So why is it short by 15 rated miles from the advertised 370 ? When I took delivery the energy graph showed a HUGE spike at about 1 mile so much so that at 11 miles by whrs / mile is 560. Could that be influencing the calculation ?

jordanrichard | 04. November 2019

marcustcohn, there are other factors at play. You say "brand new", but that doesn't tell us how long you have had it and how many miles. First, what plays a part, though it doesn't account for the "missing 15", is ambient temperature. When it gets cold, the number of Rated miles displayed for a given SOC will go down a mile or two.

Also the algorithms used to calculate and thus display available miles is based on your usage. If one constantly keeps the battery between 75-90%, then the algorithms are only seeing a 15% "window" to then guess what the projected miles will be. In other words, over time the algorithms can get wonky. One needs to periodically exercise the battery by running it down to about 10% and then go back to 90, to kind of reset the clock, if you will.

tes-s | 04. November 2019

I do not believe that influences the calculation. Charge to 100% and see what you get before concluding anything about range loss.

My experience is the first 5% of range loss often occurs pretty quickly, then the next 5% is gradual. I expect I'll be around 210k miles at 8 years, and have about 10% battery capacity loss.

Battery chemistries are different, as is usage, so it is hard to make comparisons and generalizaitons. But I think the general expectation that you will lose about 10% over 8 years, with about half being pretty early on, is reasonable.

Bighorn | 04. November 2019

Like I said, usage will not influence your rated mile figure. That would be projected range on the energy screen. Not sure I’ve heard of a 370 figure IRL and extrapolation is not precise.

jordanrichard | 04. November 2019

I am currently 2,000 miles behind tes-s with 170,000 on my MS (March 2014) and I have only lost 6%

It is not uncommon for there to be a "break in" period for the battery that affects the rated range. This is purely anecdotal, so there is no set number. It is very much like oil usage in an ICE. Depending on how the engine was used during it's first few thousand miles, the oil consumption will vary.

Tesla certainly can't publish an expected value change because every car is different.

marcustcohn | 04. November 2019

@jordanrichard et al - ---- the car was picked up 11/2 at 2PM - drove about 10 miles to my house and it has been in the garage since. Temperature there is about 50 degrees. Here is from the Tesla Website for long distance option:
373mi Range (EPA) 155mph Top Speed 3.7s 0-60

I have the car plugged into a circuit that is delivering 40 amps as needed. So will this show a different range (rated miles) going forward and if so, what are the factors that might influence this ?

Bighorn | 04. November 2019

Rated range will vary mostly by virtue of the impossibility of accurately measuring battery capacity. Spending any mental capital on this is futile.

tes-s | 04. November 2019

"the car was picked up 11/2 at 2PM - drove about 10 miles to my house and it has been in the garage since."

Drive more; worry less. ;)
Set your display to %, not miles.

marcustcohn | 04. November 2019

@bighorn et al - Underlying my futile angst is the question - 'How far can I plan to drive between SC stations' - is 200 miles ok or even 220 and if so what charge should I have to attain. I know when I get to point A and set NAV for point B it will calculate the trip but I am trying map out the route with the fewest SC stops rather than play as I go.

Bighorn | 04. November 2019

Probably between 250 and 300. Depends a lot on circumstances. Under normal circumstances, I feel pretty comfortable that I can make 80% of rated range, which for you would be 296 for a 370 rated mile model. Very few people end up traveling this way as superchargers dictate the route. You’d be in good shape to hit every other charger with that range. Personally, I dislike skipping because it’s good to take frequent breaks. Not only that, you’d be spending a bunch of time topping off. Ideally, you want to move on when you hit 80% or less. Rule of thumb was that charging from 80 to 100% takes as long as from 0 to 80%. Not a problem if you’re eating, plus charging is getting much faster, but in older vehicles, you’re talking 90 minute charges.

NJ90d | 04. November 2019

Everyone stresses out when they first get the car trying to figure out how far they can really drive. You just have to drive it and see based on your driving style, road and weather conditions etc how far you can go. The rated numbers are pretty much irrelevant to the real world but good for comparing two cars.

Temperature dropped to 28 degrees here last night, I still have my 21" wheels on and my commute is about 140 miles round trip. All the sudden I started worrying about having only charged to 85%. But reality is I will get back home with 50 or 60 miles to spare....but the 19's go back on tomorrow for the winter!

marcustcohn | 04. November 2019

Thanks to all for the comments - this is actually Model S number 5 and I hoped to generally hit every other SC in an effort to cut out another night in a motel - I know that weather and temperature will have a major impact but not much to do about that but be prepared for the worst case. Lastly, what watt hours per mile do you see over the long haul trips (yes, I know that speed and weather affect that).

Bighorn | 04. November 2019

My old 85 is at around 315. The new Ravens are more efficient and charge almost twice as fast

Bighorn | 04. November 2019

Your progress skipping chargers may be slower than hitting every one. Splash and dash for the win You should be able to average 60 mph and more if your days are short i .e. <500 miles.

bishoppeak | 04. November 2019

Bighorn is the man who knows of what he speaks! My bladder only is good for stopping at every supercharger anyway.

RAR | 04. November 2019

I've gone about 220 miles in an S90D on the first leg after fully charging before leaving home (in early fall). My lifetime average (just under 3 years and 28,000 mi) is 296 Wh/mi. Bighorn is absolutely correct. The time for the last few % to skip an SC is painful unless you are enjoying a meal or something else that requires the time.

NKYTA | 04. November 2019

I honestly haven’t looked recently, but probably slightly over 330. I don’t baby it around my commute, but it slowly comes down every time I take an SC road trip. Nearing 111k on a 2012P.