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Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

neroden

Model S Owner and Frustrated Tesla Fan
Apr 25, 2011
14,676
63,885
Ithaca, NY, USA
There we go. 70% capacity retained after 8 years was the number being thrown around at the time, in 2013. And the number in the Model 3 warranty. Although there's no explicit guarantee of capacity in the Model S warranty, if I went to court, this is the number I'd use; if you're below 70% of original nominal capacity, that's when I'd demand a replacement.

Back in 2013, I actually purchased my car *expecting* a drop to 70% of original capacity after 8 years; I planned for being able to get everywhere using only that much capacity (and accounting, additionally, for the known drop in range in winter). If you have a smaller capacity drop than that you are not going to have an easy case.

----

Tesla seems to be trying not to admit that a recent software update is in fact a safety recall; the BMS was previously not properly detecting and dealing with a pretty common type of degradation, and was therefore allowing overcharging, which is dangerous. They could have been much more transparent about this.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,518
1,721
Pennsylvania, USA
This past weekend, I charged to a full 100%. 250 indicated miles of range which should be at 310 Wh/mi for a P85D. Drove until nearly “empty” and here are my results:

41947219-6046-44C9-AD32-157019BAB8FF.jpeg
F9652F89-D57D-4425-B174-316203B91953.jpeg
ADA77D9C-313A-471C-BDF5-DB209D458DC0.jpeg


I drove it down to 1 mile remaining, but had only used 70.7 kWh on an “85” battery.
Averaging only 293 Wh/mi over a mix of local and highway for a total of 241.6 miles.

Something isn’t quite right with the numbers here. Are there losses not included in that 70.7 kWh number? Is the vampire drain that high? The car was charged to 100% on Saturday around noon and I pulled into the Supercharger at just before 2 PM on Sunday.
 

bkp_duke

Well-Known Member
May 15, 2016
5,914
22,747
San Diego, CA
There is a 5% reserve the car will never let you touch, to prevent battery damage.

So 70.7 + 3.85 kWh (reserve) = 74.55 out of an original "real" 77 kWh.

Am I missing something, or isn't this about expected? If anything, your degradation seems to be very good at only 2.45 kWh out of 77 (3.2%) in 4 years.
 
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wdolson

Well-Known Member
Supporting Member
Jul 24, 2015
7,974
11,293
Clark Co, WA
This past weekend, I charged to a full 100%. 250 indicated miles of range which should be at 310 Wh/mi for a P85D. Drove until nearly “empty” and here are my results:

View attachment 426118 View attachment 426108 View attachment 426109

I drove it down to 1 mile remaining, but had only used 70.7 kWh on an “85” battery.
Averaging only 293 Wh/mi over a mix of local and highway for a total of 241.6 miles.

Something isn’t quite right with the numbers here. Are there losses not included in that 70.7 kWh number? Is the vampire drain that high? The car was charged to 100% on Saturday around noon and I pulled into the Supercharger at just before 2 PM on Sunday.

Another question, was this one drive? If the car had been sitting parked and not plugged in, you would have vampire drain which doesn't show up in the energy used numbers. But the 85 KWH battery was never 85 KWH. They have gone with the Long Range and Short Range nomenclature to get away from battery sizes which can be less than advertised.

There is a 5% reserve the car will never let you touch, to prevent battery damage.

So 70.7 + 3.85 kWh (reserve) = 74.55 out of an original "real" 77 kWh.

Am I missing something, or isn't this about expected? If anything, your degradation seems to be very good at only 2.45 kWh out of 77 (3.2%) in 4 years.

The 85 KWH battery was actually 81KWH with 4 KWH anti-brick protection, 77 usable. If the actual usable is now 70.7, that is on the high end, but within the range of normal. Most people see 5-10%.

The information is in this thread near the beginning, but summed up here:
Tear down of 85 kWh Tesla battery pack shows it could actually only be a 81 kWh pack [Updated] - Electrek
 
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BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,518
1,721
Pennsylvania, USA
Multiple drives over a roughly 26-hour period.
I will re-do the test in a single drive in the near future to avoid the overnight vampire drain affecting the numbers.
I know the usable energy in a new “85” pack is about 77.5kWh because of the 5%/4kWh buffer.
I am trying to get a handle on the true amount of battery degradation in the first 4 years since I bought used and now know the # of miles displayed at 100% SOC is a fabrication and can’t be used to measure the real capacity.
 

sorka

Well-Known Member
Feb 28, 2015
8,555
6,396
Merced, CA
Another source of discrepancy is regen braking. When you regen brake, your used kwh unwinds as it puts energy back into the battery. Then you use it again, and then put more back in, etc ,etc. The problem is regen is not 100% efficient. The more regen braking you do, the larger the difference will be between what it said you used vs what you started with.
 

wdolson

Well-Known Member
Supporting Member
Jul 24, 2015
7,974
11,293
Clark Co, WA
Multiple drives over a roughly 26-hour period.
I will re-do the test in a single drive in the near future to avoid the overnight vampire drain affecting the numbers.
I know the usable energy in a new “85” pack is about 77.5kWh because of the 5%/4kWh buffer.
I am trying to get a handle on the true amount of battery degradation in the first 4 years since I bought used and now know the # of miles displayed at 100% SOC is a fabrication and can’t be used to measure the real capacity.

I've seen the car lose up to three miles of range when sitting in a parking lot for 1-2 hours. The car will go to sleep eventually and have less vampire range, but the drain the first hour or so after parking is pretty bad.

Another source of discrepancy is regen braking. When you regen brake, your used kwh unwinds as it puts energy back into the battery. Then you use it again, and then put more back in, etc ,etc. The problem is regen is not 100% efficient. The more regen braking you do, the larger the difference will be between what it said you used vs what you started with.

The bigger loss is if you're using the actual brakes instead of regen. You also lose energy when the regen is limited because the battery is cold (though not a problem in most of the northern hemisphere this time of year). With regen on max you're recovering as much of the energy as you can.

The car doesn't keep track of vampire drain beyond the %battery remaining or estimated miles remaining. It only keeps track of energy used while the car is being driven. So it keeps track of regen going back into the battery. However it isn't very accurate with low levels of regen or low levels of energy usage. So the total can get skewed either way if you do a drive where you are doing a lot of low regen (such as going down a shallow hill) or just using a bit of energy to propel the car. I think what happens is the numbers get small enough that the MCU is having to calculate without using enough significant digits and numbers get rounded off too much.
 

sorka

Well-Known Member
Feb 28, 2015
8,555
6,396
Merced, CA
The bigger loss is if you're using the actual brakes instead of regen. You also lose energy when the regen is limited because the battery is cold (though not a problem in most of the northern hemisphere this time of year). With regen on max you're recovering as much of the energy as you can.
.

Of course, but using the brakes in instead of regen doesn't contribute to the discrepancy between odometer kwh used vs what you're actually left with which was my only point.

The car doesn't keep track of vampire drain beyond the %battery remaining or estimated miles remaining. It only keeps track of energy used while the car is being driven. So it keeps track of regen going back into the battery. However it isn't very accurate with low levels of regen or low levels of energy usage. So the total can get skewed either way if you do a drive where you are doing a lot of low regen (such as going down a shallow hill) or just using a bit of energy to propel the car. I think what happens is the numbers get small enough that the MCU is having to calculate without using enough significant digits and numbers get rounded off too much.

It's actually very accurate but not 100% efficient so the more cycles out and then back in with regen, the more you lose resulting in a larger discrepancy.
 

FlatSix911

Porsche 918 Hybrid
Jun 15, 2015
7,194
7,307
Silicon Valley
Multiple drives over a roughly 26-hour period.
I will re-do the test in a single drive in the near future to avoid the overnight vampire drain affecting the numbers.
I know the usable energy in a new “85” pack is about 77.5kWh because of the 5%/4kWh buffer.
I am trying to get a handle on the true amount of battery degradation in the first 4 years since I bought used and now know the # of miles displayed at 100% SOC is a fabrication and can’t be used to measure the real capacity.

You may want to try an app that will record battery degradation over time and measure other data points... https://www.maadotaa.com/

upload_2019-7-4_17-48-34.png
 

AmpedRealtor

Well-Known Member
Jun 30, 2013
6,414
4,111
Phoenix, AZ
Riddle me this...

If Tesla advertised 85 kWh batteries, which they did, yet delivered to us vehicles containing less than 82 kWh in cells, how is it that there has been no class action lawsuit against Tesla for this? We presumably paid for what Tesla advertised, how is Tesla not responsible for delivering to us what we paid for?
 
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JRP3

Hyperactive Member
Aug 20, 2007
21,173
52,392
Central New York
I think it would be a difficult case to prove. My guess is Tesla would argue that exact capacity is affected by different parameters, it's calculated using cell ratings from the cell producer, and that if you don't measure a pack under the same conditions as the original cell rating test on a brand new car you'd get different results. I'm not saying that's correct but I think it might be enough to muddy the waters to prevent a judgement against them. INAL of course.
 
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wdolson

Well-Known Member
Supporting Member
Jul 24, 2015
7,974
11,293
Clark Co, WA
Because there were over 7100 cells in the original 85 KWH pack, a small variation in the capacity of each cell would swing the final number quite a bit. If they used a cell capacity that was the theoretical best for the chemistry rather than the average and then multiplied it up to the number of cells in a pack, they could get a number closer to 85 KWH, even though virtually nobody would ever see that because it would require getting every cell at the maximum possible capacity.

The variability in cells can be seen in how much degradation different people see. How you treat the pack and how you drive affects how the cells age, but two people who do the exact same behaviors could see one car barely degrade and another drop 5% in the first year. Different cars report different capacities when new too.

Another factor is that I don't know of any precise standard for measuring the capacity of a cell. In the US there is the EPA standard for fuel mileage and Europe has their own standard measure (the EPA measure is considered more accurate in the real world). And there are standardized ways to measure the horsepower and torque of a motor or car.

The capacity of a cell looks simple, but there are a lot of "it depends" factors. The capacity is obtained by multiplying the voltage by the AH capacity. However, the voltage can vary quite a bit over the discharge range of the cell and it varies a bit from one chemistry to another. Most Li-ion cells have a voltage at 100% around 4V and that drops off to 3.7 or 3.8V fairly quickly when discharging drops slower over the discharge cycle then drops quickly to about 1V near the end. Exactly what you claim the max voltage is can make a big difference when scaled up to the entire pack.

The AH rating is how much current it can provide for how long. A 1 AH cell might provide 1A for 1H, or could provide 1/2A for 2H, but in reality the discharge is not a steady supply at one current and then a cliff, it's a curve that can get complex and the AH rating is essentially the area under the curve, which is getting into integral calculus. Individual cells can vary a bit in the capacity. Small variations on the cell level can make a big difference at the pack level.

Here is an article on capacity measures:
BU-904: How to Measure Capacity – Battery University

There are standards, but they are loose enough that they can be fudged. If Tesla were sued about pack capacity they could bring into court their tests of the best cells of a certain chemistry and show that at the pack level 85KWH and 90KWH were technically possible, though only under the ideal condition you got a pack made up of the best of the best cells. They may have made some packs out of cherry picked cells.

Until there is some kind of industry standard that says you run x number of randomly selected cells through these exact tests. There will be enough room to fudge the numbers.

The range number for a car is comparable between different car models because the EPA has a standardized test they put all their cars through. It's possible the manufacturer can supply a test car with a better than average pack, but unless they deliberately selected the best cells, the law of averages will make the range of pack level capacities more tightly packed than the variations in individual cell capacities.

So this is one of those things that Tesla is going to skate on. It does look like they have become somewhat more conservative in their claims. The 100KWH pack is actually around 102 KWH. They have never really advertised the capacity of Model 3 packs, though the information is out there.
 

AmpedRealtor

Well-Known Member
Jun 30, 2013
6,414
4,111
Phoenix, AZ
Because there were over 7100 cells in the original 85 KWH pack, a small variation in the capacity of each cell would swing the final number quite a bit. If they used a cell capacity that was the theoretical best for the chemistry rather than the average and then multiplied it up to the number of cells in a pack, they could get a number closer to 85 KWH, even though virtually nobody would ever see that because it would require getting every cell at the maximum possible capacity.
If that's true, then where are Tesla's disclaimers to this effect on its advertising, its order page, purchase agreement, and the Monroney sticker? Nowhere did Tesla disclaim anything, they very clearly and in a straightforward manner advertised the vehicles as having an 85 kWh battery. It's probably too late now anyway, but it looks like the ownership community let Tesla get away with blatant misrepresentation here.

I hope the community responds differently to the latest range-gate: Sudden Loss Of Range With 2019.16.x Software
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,518
1,721
Pennsylvania, USA
I re-did my test yesterday one one non-stop drive from 100% charge down to zero (excluding the anti-bricking buffer). Actual zero is impossible, but I had to dead-stick it into the Sheetz parking lot and push it into a Supercharger stall. It wouldn’t go into any gear.

This time it showed 71.8 kWh used in the 240.3 mile trip at 299 Wh/mi (slightly more efficient than the 310 rated for a P85D).

If 85 packs originally had 77.5 useable, then I am down 5.7 from new, or 7.3%. Which doesn’t seem all that good for a pack with only 28K miles.

Battery voltages at 100% charged (five minutes after unplugging with charge complete):
86BC1FC0-0778-46A1-BACB-29350D512B0C.jpeg


Battery voltages at empty:
7877FA22-6FCB-4793-972B-72475CF2AF57.jpeg


Dashboard with trip info:
F8879902-B034-4384-B883-AC5AF3ED1569.jpeg


Maximum rate seen during Supercharging:
1CAF2302-67E7-4CF0-B815-14BF7CBB4139.jpeg


It seemed it took about 5 minutes after plugging the Supercharger cable in before the car started charging. Group 57 appeared to be about 55 Mac less than any other cell groups. I hope I didn’t damage anything, but isn’t that what the bottom-end buffer is for?
 
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VT_EE

Active Member
Apr 22, 2017
2,095
2,820
Maryland
If that's true, then where are Tesla's disclaimers to this effect on its advertising, its order page, purchase agreement, and the Monroney sticker? Nowhere did Tesla disclaim anything, they very clearly and in a straightforward manner advertised the vehicles as having an 85 kWh battery. It's probably too late now anyway, but it looks like the ownership community let Tesla get away with blatant misrepresentation here.

I hope the community responds differently to the latest range-gate: Sudden Loss Of Range With 2019.16.x Software
Sadly that is doubtful as most Tesla owners will not experience this problem so their level of interest is minimal. The vast majority of Tesla owners own modern variants and not even a majority of existing 85 owners seem to have the issue (if Tesla is to be believed).
 
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VT_EE

Active Member
Apr 22, 2017
2,095
2,820
Maryland
I re-did my test yesterday one one non-stop drive from 100% charge down to zero (excluding the anti-bricking buffer). Actual zero is impossible, but I had to dead-stick it into the Sheetz parking lot and push it into a Supercharger stall. It wouldn’t go into any gear.

This time it showed 71.8 kWh used in the 240.3 mile trip at 299 Wh/mi (slightly more efficient than the 310 rated for a P85D).

If 85 packs originally had 77.5 useable, then I am down 5.7 from new, or 7.3%. Which doesn’t seem all that good for a pack with only 28K miles.

Battery voltages at 100% charged (five minutes after unplugging with charge complete):
View attachment 427345

Battery voltages at empty:
View attachment 427344

Dashboard with trip info:
View attachment 427342

Maximum rate seen during Supercharging:
View attachment 427343

It seemed it took about 5 minutes after plugging the Supercharger cable in before the car started charging. Group 57 appeared to be about 55 Mac less than any other cell groups. I hope I didn’t damage anything, but isn’t that what the bottom-end buffer is for?
Wow. You are dedicated and brave to do that. 7.8% degradation seems pretty good for a 5-year (?) old vehicle. I assume you are not upset about that given what others are seeing.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,518
1,721
Pennsylvania, USA
Wow. You are dedicated and brave to do that. 7.8% degradation seems pretty good for a 5-year (?) old vehicle. I assume you are not upset about that given what others are seeing.
I didn’t intend to run it out all the way, but I miscalculated and cut it a bit too close.

Don’t try this yourself. :) There is no “reserve”. Zero means Shutdown. And the Distance displayed on the IC is optimistic so “5 miles” left may only be 4.5 or so.

A P85D is a heavy car to push.
 

wdolson

Well-Known Member
Supporting Member
Jul 24, 2015
7,974
11,293
Clark Co, WA
If that's true, then where are Tesla's disclaimers to this effect on its advertising, its order page, purchase agreement, and the Monroney sticker? Nowhere did Tesla disclaim anything, they very clearly and in a straightforward manner advertised the vehicles as having an 85 kWh battery. It's probably too late now anyway, but it looks like the ownership community let Tesla get away with blatant misrepresentation here.

I hope the community responds differently to the latest range-gate: Sudden Loss Of Range With 2019.16.x Software

I saw no drop in range. The car ran the tests over a couple of days, but it didn't find any bad cells.
 

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