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Understanding Range

Mike MY

Member
Apr 28, 2020
31
28
Louisville, KY
I've read quite a few threads on this message board related to the Battery Management System (BMS) and range degradation. A lot of people seem to think their battery has deteriorated quickly or they think the BMS is affected by their charging habits. I think I've come to an understanding of the situation and I don't believe it involves battery deterioration or charging habits.

Let me explain:

When my model Y was new, it showed 316 miles at full charge.

It now has 6,500 miles on it. Today I upgraded from version 40.3 to version 40.8. Knowing that this involved an efficiency improvement, I looked at some numbers before and after.

Prior to ver. 40.8: car showed 79% charge or 229 miles.
Extrapolating this out: 229 / 79 x 100 = 290 miles at full charge.

After ver. 40.8: car showed 79% charge or 235 miles
Extrapolating this out: 235 / 79 x 100 = 297 miles at full charge.

The car has a 75Kw battery, but people on this board have said only 73Kw is usable.

When the car is new, it does not have a history to know how may Wh/mile you use since this is different for all drivers and configurations. They derive 316 miles rated range by assuming a certain speed (probably 50 mph) on level ground with no A/C, no lights, and no wind. If you do the math, 73,000 W / 316 miles = 231 Wh/mile. I don't know anyone who averages that low consumption.

As you drive your car, it keeps track of your consumption. At 6,500 miles, my lifetime average is 252 Wh/mile.

Let's do some more math:

73,000 W battery / 252 Wh/mile (my historical average) = 290 miles at full charge (same as my calculation prior to installing version 40.8.

75,000 W battery / 252 Wh/mile (my historical average) = 297 miles at full charge (same as my calculation after installing version 40.8.

It seems likely to me that version 40.8 software unlocks the extra 2Kw of your battery to allow full use of the 75Kw battery pack.

As an experiment, I charged to 100% after installing version 40.8 and the car showed a range of 297 miles. This seems to confirm my logic above.

Conclusion #1: It appears the full 75Kw of the battery is now usable.
Conclusion #2: The decreased range we experience at 100% charge is due to our average Wh/mile (configuration, weather, terrain, driving habits), not battery degradation or charging habits.
 

mswlogo

Well-Known Member
Aug 27, 2018
6,069
4,699
MA, NH
I've read quite a few threads on this message board related to the Battery Management System (BMS) and range degradation. A lot of people seem to think their battery has deteriorated quickly or they think the BMS is affected by their charging habits. I think I've come to an understanding of the situation and I don't believe it involves battery deterioration or charging habits.

Let me explain:

When my model Y was new, it showed 316 miles at full charge.

It now has 6,500 miles on it. Today I upgraded from version 40.3 to version 40.8. Knowing that this involved an efficiency improvement, I looked at some numbers before and after.

Prior to ver. 40.8: car showed 79% charge or 229 miles.
Extrapolating this out: 229 / 79 x 100 = 290 miles at full charge.

After ver. 40.8: car showed 79% charge or 235 miles
Extrapolating this out: 235 / 79 x 100 = 297 miles at full charge.

The car has a 75Kw battery, but people on this board have said only 73Kw is usable.

When the car is new, it does not have a history to know how may Wh/mile you use since this is different for all drivers and configurations. They derive 316 miles rated range by assuming a certain speed (probably 50 mph) on level ground with no A/C, no lights, and no wind. If you do the math, 73,000 W / 316 miles = 231 Wh/mile. I don't know anyone who averages that low consumption.

As you drive your car, it keeps track of your consumption. At 6,500 miles, my lifetime average is 252 Wh/mile.

Let's do some more math:

73,000 W battery / 252 Wh/mile (my historical average) = 290 miles at full charge (same as my calculation prior to installing version 40.8.

75,000 W battery / 252 Wh/mile (my historical average) = 297 miles at full charge (same as my calculation after installing version 40.8.

It seems likely to me that version 40.8 software unlocks the extra 2Kw of your battery to allow full use of the 75Kw battery pack.

As an experiment, I charged to 100% after installing version 40.8 and the car showed a range of 297 miles. This seems to confirm my logic above.

Conclusion #1: It appears the full 75Kw of the battery is now usable.
Conclusion #2: The decreased range we experience at 100% charge is due to our average Wh/mile (configuration, weather, terrain, driving habits), not battery degradation or charging habits.

Both conclusions are wrong.

The car can be more efficeintly using 73Kwh. I don't know where you got that number but probably from someone using a CanBus app and sounds typical. My X isn't 100Kwh usable.

The displayed rated range is calibrated more on charging patterns than driving efficiency patterns. You can drive however you want it won't change the capacity estimate. It is based on the EPA estimate of how far you could go on full charge if you drove like EPA does during testing. You might average better you might average worse.

How you drive and your charging habits might impact battery degradation. And the luck of the draw you have on the cells in your battery.

Assuming your Model Y has the same hardware as currently listed (it may not) has a rating of 327 you would have a 10% loss after 6500 miles, that would be a bit high. My guess is you don't have the same hardware. But you have some of it. Otherwise I think you would have seen a bigger jump in range after installing 40.8. Since it only went up 2% (lets say 3% because the install might have eaten 1% of the battery charge you had). You have about a 7% degradation. Still a little on the high side. But Range calibration could be off. You have to have pretty weird charging practices for it to be off much. Again it is NOT based on driving efficiency. Folks confuse that ALL the time. It's just like an ICE fuel gauge and tells you how full the tank is (in "EPA" mile units). And the tank shrinks over time (battery degradation).
 
Last edited:

Tam

Well-Known Member
Nov 25, 2012
8,935
7,721
Visalia, CA
...Conclusion #1: It appears the full 75Kw of the battery is now usable...

When comparing, you should compare 100% at the same temperature at one time which was 316 miles displayed on the dashboard battery icon and another 100% at the same temperature at another time and I assume your dashboard battery icon displays 297 miles?

Do not extrapolate from a partially charged number like 79%.

The miles displayed on the dashboard battery icon when the propulsion is "off" is based on EPA fixed formula.

That means, if you have a perfect BMS, when your car is parked at 100% charge, it should always be 316 miles on the battery gauge.

That 316 miles EPA is not dependent on your numerous factors of driving habits and road conditions (because the car is parked and not moving at 100% charge just yet).

What concerns owers is: at 100%, it used to display 316 miles, and now, the same 100% displays 297 miles on the battery gauge. That's a loss of 64 miles or 20% even before rolling the car!

Your answer to the issue that the reason owners got a lesser number is because Tesla has allows an increase energy to the full 75kWh (which does not make sense: We should get more than 316 miles and not less at 297 miles!)

...Conclusion #2: The decreased range we experience at 100% charge is due to our average Wh/mile (configuration, weather, terrain, driving habits), not battery degradation or charging habits.

Again, when talking about degradation, the first thing to worry about is the battery gauge when the car is at 100% and before running the car.

Because even if the car displays 100% and 265 miles, some hypermilers can drive slowly to 500 actual miles before the car shuts down.

316 EPA miles is a fixed number but whether you can actually get that EPA number or not depends on whether you are a hypermiler or not.

But again, that is not what people are talking about but it's about: Why it used to display 316 miles at 100% at rest but now it displays 297 miles at 100% or a loss of 64 miles or 20% with the same parking condition!
 
Last edited:
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Mike MY

Member
Apr 28, 2020
31
28
Louisville, KY
Thanks for feedback, guys. I’m not an expert so I’m not arguing I’m right. The numbers certainly support my theory though (perhaps a coincidence). I agree with Mr. X, “ Percentage and forget it.” It’s just the geek in me trying to understand what’s going on. I’m going to keep an eye on it as the years go by to see if my theory holds up.
 

captanzuelo

Member
May 28, 2020
499
693
los angeles
Thanks for feedback, guys. I’m not an expert so I’m not arguing I’m right. The numbers certainly support my theory though (perhaps a coincidence).

Using your theory, I did the math on my range increase. Its off by just two miles, which I think, supports your theory.

Pre 40.8 I had degraded to 294 miles on a full charge. Your theory says I should have 302 miles after the update.
Post 40.8 I now have 304 miles on a full charge.

73,000/294 = 248 Wh/mi
75,000/248 = 302 Miles
 

Mike MY

Member
Apr 28, 2020
31
28
Louisville, KY
Using your theory, I did the math on my range increase. Its off by just two miles, which I think, supports your theory.

Pre 40.8 I had degraded to 294 miles on a full charge. Your theory says I should have 302 miles after the update.
Post 40.8 I now have 304 miles on a full charge.

73,000/294 = 248 Wh/mi
75,000/248 = 302 Miles

Captanzuelo, your math is not quite the same as mine. Do you know your lifetime average Wh/mile? Most people track it with Trip B on their odometer. I’d be interested in seeing if my math pans out on your car.
 

phil4791eng

Member
Aug 17, 2020
124
87
Oklahoma City, OK
The green bar has nothing to do with your driving habits. The green bar is a basis of the EPA rating of 316 miles. As the battery degrades, the mileage displayed decreases. The mileage in the energy tab takes into account the useable energy in the battery and your driving habits.

You have 72.5 kWh of useable battery.
 

captanzuelo

Member
May 28, 2020
499
693
los angeles
Captanzuelo, your math is not quite the same as mine. Do you know your lifetime average Wh/mile? Most people track it with Trip B on their odometer. I’d be interested in seeing if my math pans out on your car.

Last time I checked lifetime average, it was about 275Wh/mi. I use this to calculate my "realistic" range.
 
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Mike MY

Member
Apr 28, 2020
31
28
Louisville, KY
Last time I checked lifetime average, it was about 275Wh/mi. I use this to calculate my "realistic" range.

Thanks for responding, captanzuelo. Unfortunately my theory does not hold true with your numbers. Based on my theory your 100% charge would equate to a displayed miles of: 75000 W / 275 Wh/mile = 273 miles At full charge.

I think this proves me wrong.

thanks everyone for your input.
 

Robocheme

Member
Feb 3, 2017
216
209
Northern California
When comparing, you should compare 100% at the same temperature at one time which was 316 miles displayed on the dashboard battery icon and another 100% at the same temperature at another time and I assume your dashboard battery icon displays 297 miles?

Do not extrapolate from a partially charged number like 79%.

The miles displayed on the dashboard battery icon when the propulsion is "off" is based on EPA fixed formula.

That means, if you have a perfect BMS, when your car is parked at 100% charge, it should always be 316 miles on the battery gauge.

That 316 miles EPA is not dependent on your numerous factors of driving habits and road conditions (because the car is parked and not moving at 100% charge just yet).

What concerns owers is: at 100%, it used to display 316 miles, and now, the same 100% displays 297 miles on the battery gauge. That's a loss of 64 miles or 20% even before rolling the car!

Your answer to the issue that the reason owners got a lesser number is because Tesla has allows an increase energy to the full 75kWh (which does not make sense: We should get more than 316 miles and not less at 297 miles!)



Again, when talking about degradation, the first thing to worry about is the battery gauge when the car is at 100% and before running the car.

Because even if the car displays 100% and 265 miles, some hypermilers can drive slowly to 500 actual miles before the car shuts down.

316 EPA miles is a fixed number but whether you can actually get that EPA number or not depends on whether you are a hypermiler or not.

But again, that is not what people are talking about but it's about: Why it used to display 316 miles at 100% at rest but now it displays 297 miles at 100% or a loss of 64 miles or 20% with the same parking condition!

I don't follow your math. It seems like the loss is 19 miles (316-297). How did you get 64 miles?
 
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Xtek

Member
Sep 13, 2017
605
430
Seattle, WA
The car does not adjust your range based on how you drive. There is an "estimated range" but this isn't surfaced anywhere and is just based on your last driving session. You're likely seeing a combination of BMS imbalance and degredation.
 
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Robocheme

Member
Feb 3, 2017
216
209
Northern California
I've read quite a few threads on this message board related to the Battery Management System (BMS) and range degradation. A lot of people seem to think their battery has deteriorated quickly or they think the BMS is affected by their charging habits. I think I've come to an understanding of the situation and I don't believe it involves battery deterioration or charging habits.

Let me explain:

When my model Y was new, it showed 316 miles at full charge.

It now has 6,500 miles on it. Today I upgraded from version 40.3 to version 40.8. Knowing that this involved an efficiency improvement, I looked at some numbers before and after.

Prior to ver. 40.8: car showed 79% charge or 229 miles.
Extrapolating this out: 229 / 79 x 100 = 290 miles at full charge.

After ver. 40.8: car showed 79% charge or 235 miles
Extrapolating this out: 235 / 79 x 100 = 297 miles at full charge.

The car has a 75Kw battery, but people on this board have said only 73Kw is usable.

When the car is new, it does not have a history to know how may Wh/mile you use since this is different for all drivers and configurations. They derive 316 miles rated range by assuming a certain speed (probably 50 mph) on level ground with no A/C, no lights, and no wind. If you do the math, 73,000 W / 316 miles = 231 Wh/mile. I don't know anyone who averages that low consumption.

As you drive your car, it keeps track of your consumption. At 6,500 miles, my lifetime average is 252 Wh/mile.

Let's do some more math:

73,000 W battery / 252 Wh/mile (my historical average) = 290 miles at full charge (same as my calculation prior to installing version 40.8.

75,000 W battery / 252 Wh/mile (my historical average) = 297 miles at full charge (same as my calculation after installing version 40.8.

It seems likely to me that version 40.8 software unlocks the extra 2Kw of your battery to allow full use of the 75Kw battery pack.

As an experiment, I charged to 100% after installing version 40.8 and the car showed a range of 297 miles. This seems to confirm my logic above.

Conclusion #1: It appears the full 75Kw of the battery is now usable.
Conclusion #2: The decreased range we experience at 100% charge is due to our average Wh/mile (configuration, weather, terrain, driving habits), not battery degradation or charging habits.

After installing 40.8, my range increased from 256 to 262. At 87%, that converts to a max range change from 294 to 301.

BTW, after about 2786 lifetime miles, my overall/lifetime efficiency is 278 wh/mi. That doesn't seem to support your theory.

My theory is that my particular battery pack has degraded quicker than expected and I can't do anything about it. I saw this same behavior in my Model 3. Just unlucky, I guess
 
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GeezerSquid

Still a Geezer & Still A Squid
Jun 17, 2020
162
191
Baton Rouge, LA
I've only charged my battery to 100% twice. Once was about a week ago after I heard what 2020.40.8 was supposed to do and I got 309 miles of estimated range. I received that update yesterday and I charged up to 100% last night and got 321 miles of estimated range. Very happy old guy here!!
 

imola.zhp

Member
Jul 13, 2020
462
282
Memphis
It funny, people get so hung up over total range. I thought this would be less common with vehicles that have YUGE batteries as opposed to the short-range cars we've owned for the past 5 years.

My understanding is the total estimated 100% range is... wait for it... estimated. Based on your driving history. If you want a larger number, no more 0-60 sprints, always take off and come to a stop as smoothly and slowly as possible and try not go go above 45mph. Do this for as long as you can if you really want to see that 326 displayed.
 

captanzuelo

Member
May 28, 2020
499
693
los angeles
Yea I really don't understand people's obsession over losing a few miles of range. Drive 45mph if you want to maximize your range.

I didn’t understand it either, until I drove a Model S for a week. The “estimated” range was spot on, even with my 80mph freeway driving. If the navigation showed a 5 mile trip, then the “estimated” range would only go down correspondingly. Now the MY on the other hand, lies. The same 5 mile trip would take 8-10 “estimated” miles of range.

Bottom line is, I need to knock 30% off the estimated range to get an accurate figure on this car whereas MS owners don’t.
 

DaveORD

Member
Mar 12, 2020
727
628
Chicagoland
I didn’t understand it either, until I drove a Model S for a week. The “estimated” range was spot on, even with my 80mph freeway driving. If the navigation showed a 5 mile trip, then the “estimated” range would only go down correspondingly. Now the MY on the other hand, lies. The same 5 mile trip would take 8-10 “estimated” miles of range.

Bottom line is, I need to knock 30% off the estimated range to get an accurate figure on this car whereas MS owners don’t.

But how old, how many miles did the MS have on it? Are we comparing apples to apples here? The MS may have a lot more miles and charge cycles on its battery and is better trained/tuned to its battery level and actual mileage. The MY on the other hand is very new and I assume a lot less miles and cycles on its battery than the MS you drove, so less in tune. Just a guess...
 

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