Some new data from research on Tesla model 3 cells

There has recently been released a series of new research reports containing tests on Tesla Model 3 Cells (Panasonic 2170 NCA).
This is the calendar aging test from one of them (25C, 15, 50 and 85% SOC. Checkup once a month):
Using the datapoints from these and putting them in the old charts I ususally post, these match the olds ones quite good. As there is only three points, it do not show the real form of the curve, but all three points match the usual graphs.

For the cyclic tests, they did use rather high currents, not really respresentative to normal EV use. (To the researchers defense, the currents used is sort of the most EV-battery manufacturers current in the specifications but still not close to the regulkar EV usage).
Charged with 0.33C which would match about a 25kW DC charger, or double to four times the usual rate EV owners use mostly. Probably not offsetting the result much, but to be clear this is how it was done.

Discharged with 1C, which would be 78kW, about enough to drive constant at 200kph. This is way above the average power used from a regular EV. Driving at higway speeds at 120kph/80mph or so, we normally use like 1/4 of that power.
The average car often has a average speed longterm of about 50-60kph, meaning we often use 1/8-1/4 of the power in these cyclic tests.
From other tests we can se that lower power reduce the wear, the degradation often reduces to somewhere down to 0.5-0.7C.

In this report the author was a bit surprised over the increased wear at 5-15% SOC and 15-25% SOC. I would say that it it a very high probability of that this is induced by the 1C discharge rate, and that our normal power rates used IRL would make this look different. This is nothing I can promise but from several other research tests we can see that there ususally is a tendency to slightly increase the cyclic degradation at the lowest SOC ranges.

According to this chart, the best cycling range is 55 % down to 35%( see note below about true SOC).

Note: These are “True SOC”. 0% in this chart is where the car already has stopped, and 5% in-chart is about 0% displayed and 55% in-chart is is about 57% displayed.

As I said above, there is a high probability that the low SOC range wear much less with a lower C-rate. Anyway, due to the high impact of calendar aging we most certainly benefit from staying low in SOC.

For the first two years, we would loose about 9-9.5% from calendar aging if staying at high SOC.
During these two years, if we drive 15-20K km annually (10-15Kmiles), and stay in the very low regime cycling (5-25% true SOC, thats 0-20% displayed SOC) we would loose about 1% from ~ 75-100 FCE cycles during these two years/30-40K km.

IRL its not possible to stay that low in SOC without actively stopping the charging, as 50% is the lowest setting (but for reference to low /high SOC).

To reach the same level of cyclic degradation from low SOC cycling according to the chart we would need about 700FCE, or about 280K km, but that is not really possible to do and at the same time stay at 5-25% SOC.

So, a car charged to 80-90%, and used as most EV’s is used, will mostly be above 55% SOC and have a calendar aging close to the 85% graph.
After two years, it will be around 10% degradation if the average cell temp is about 25C.

If the car was charged to 50-55% it would have a calendar aging around 6%, and the cyclic aging would be half the high SOC car, so more or less negligeble.

Link to one report

[Edit]For what its worth, if someone is worried about the low SOC below 20% (I am not, but I’m aware of the classic forum rumors), charging to 50-55% and charging for the daily drives at or above 20% (not talking longer traveling here) all aspect of this report if ticked-in-the-box.

I will not change any of my charging behavior because of this report. There is from time to time small differences in the reports and usually the reason for that can be found by thorougly comparing with other tests. We need much more than one report to state a “fact”.

 

[yesimon]

Going back to LFP for a second, if charging to 100% allows for cell balancing and other calibration, my question would be, is there any theoretical or empirical NEED to charge to 100%? Does it in any way HELP the LFP battery? Or should I just wait for my summer road trip to charge to 100% and calibrate once or twice a year before a big road trip? Based on the advice on this thread, I have been waiting until I get to 40% and then I charge to 60%. I don't ever drive below 10% where having a precisely calibrated battery could make or break my drive.

For LFP batteries, there is some evidence that shallow-cycling in narrow SOC ranges can cause reversible degradation. See Capacity Recovery Effect in Commercial LiFePO4 / Graphite Cells

The cycling behavior that caused the most short-term/reversible degradation was the 40-60% cycling behavior. Also in part d of the figure, the worst degradation was cycling within a voltage plateau, such as being in region 4 exclusively. The authors speculate that "continued shallow cycling around medium states of charge (SOCs) leads to non-uniform lithium distribution in the electrodes of a commercial LiFePO4/Graphite (LFP/C) cell, which results in a reversible loss of capacity."

This is a lot to say that with LFP, cycling 0-100% like a gas car avoids many weird issues and is the simplest so you don't need need to overthink it.

 

[Eric33432]

We have a little Model 3 RWD Tessie that does not get driven a lot. It stays parked at about 75% for sometimes weeks.

Does anyone know if that is bad for the LFP battery and if so what would be the best practice for it?

 

[dakhlkt22]

For LFP batteries, there is some evidence that shallow-cycling in narrow SOC ranges can cause reversible degradation. See Capacity Recovery Effect in Commercial LiFePO4 / Graphite Cells

View attachment 1013982

The cycling behavior that caused the most short-term/reversible degradation was the 40-60% cycling behavior. Also in part d of the figure, the worst degradation was cycling within a voltage plateau, such as being in region 4 exclusively. The authors speculate that "continued shallow cycling around medium states of charge (SOCs) leads to non-uniform lithium distribution in the electrodes of a commercial LiFePO4/Graphite (LFP/C) cell, which results in a reversible loss of capacity."

This is a lot to say that with LFP, cycling 0-100% like a gas car avoids many weird issues and is the simplest so you don't need need to overthink it.

Although might be hard to get any of us to do it the simplest way. Most of us are in this thread because we are very much interested in overthinking it

I'm not drawing the entirely same conclusion from this study that you are. Here it says charging to 100% allows recovery of most of the capacity loss noticed.

The experimental results can be summarized as follows:

• –
  Cycling cylindrical LFP/C cells anywhere between 30% SOC and 70% SOC, i.e. where the equilibrium voltage curve's gradient is low, produces significantly higher capacity losses than full cycles.
• –
  Keeping the cells at 0% SOC or 100% SOC, i.e. where the equilibrium voltage curve's gradients are high, recovers most of the lost capacity within a couple of days.

Then at the end of the article it says

After recuperation, the relative capacity of low cycle depth cells was higher than that of full cycle cells.

Can't we infer from this latter statement that we can optimize by shallow discharge cycles combined with charging to 100% sometimes? That's a little bit different than "cycling 0-100% like a gas car". Both charts 2a and 2c seem to show 0-100% cycles as resulting in the lowest capacity retention.

 

[yesimon]

I'm not drawing the entirely same conclusion from this study that you are. Here it says charging to 100% allows recovery of most of the capacity loss noticed.

Based on figure 5, the recuperation by holding at 100% SOC (3.6V hold) was only able to recover <50% of the lost capacity after 35 days of continuous holding. The recuperation of 0% SOC was much more effective but is difficult to do in the real world. Unfortunately the authors glossed over the nuances here and just said "recuperation can recover lost capacity in a couple days", but that's only true for the 0% hold at elevated temperatures 45C.

The reversible degradation crossover b/w 40-60% and 0-100% cycling was at 7000 FEC which is greater than 1.5 million real world miles, which you will never reach.

It seems better to avoid the "reversible degradation" in the first place by having wide charging windows or taken to the max - cycling 0-100%. Yes you can recuperate but it doesn't seem as trivial as the authors suggest.

 

[AAKEE]

Yeah. We know your pack has 73.7kWh and a full pack has about 236 miles. Maybe 239 max.
Anyway that gives 308Wh/mi to 312Wh/mi and so 310Wh/mi is probably correct.

However I’d expect the line to cross at 315Wh/mi but maybe that is just a Model 3 thing.

Seems slightly contradictory though. Your pictures of energy screen above (if taken concurrently) really don’t work out quite the way I would expect. The calculation does not work - it gives 74.5kWh minimum. Seems slightly too far off the 73.7kWh. Maybe it does not work quite right on older vehicles. Not a huge error though. Just seems like slightly more than can be explained by rounding.

Anyway no big deal. Glad you have the info now.

As the buffer is fixed and the true SOC number do not work like 3/Y.
Almost looks like the true soc is [buffer size] higher than displayed and would show 105% at 100%.
We need to see and understand that relation to be able to find it out. I’s surecwe can figure it out together

I looked at the abstract and found this part interesting.


Later on:


and in the conclusion:

So it sounds like he developed a way to measure the activity of the silicon in the anode using hysteresis measurements and it was the primary culprit for the low SOC cycle degradation.

The batteries he focused on were mixed material anodes (Graphite/SiOx ). Older Tesla NCA batteries where graphite only.

• How much of the degradation we're seeing is due to the silicon in the anode?
• Should we expect to see rapid flattening of the degradation curve when most of the silicon becomes inactive?
• Might this mean that graphite only anode NCA cells truly exhibit less degradation due to aging?

This report (or these as it is a couple of reports) did not go very deep into it.
I know specifically NCA sometimes show a bit strange results with regard to the current rate.

I also know that at low SOC (~20% ish and lower) the batteries often is sensitive to high current.
They did all tests with 1C, which is = 80kW which would equal about driving at 200 kph.
The average driving we have, is like 70kph and 170 Wh/km or so. So like 10kW in average and ~120 Wh/km and 200Wh/km = 24 kW power.
This means we probably average about 0.12-0.3C current rate. I guess the chart would look slightly different for the lowest SOC’s if they had tested at lower current rates.

I recommend reading this research report.
Peter keil has done a lot on NCA cells.
Good work.
This report covers many aspects and use different load/current and different C-rates for charging.
Panasonic NCA so more close to model S from before. But tge main characteristics is about the same so.
Test report

Here 18650 NCA cycled down to 0% from different SOC, 4.25V is overcharged by ~2%.
Each 0.1V from 4.20V / 100% is about 10% change in SOC, so 3.7V about 50%.

Reducing the charging level reduces the degradation, as the cycles get smaller and the SOC gets lower. At 50-60% that reduction is dimished. We have a sign of the 2170 research test finding here.

Heres a charge cycle test; the cells are 2.9Ah, so 1A = about 0.3C
0.3C and lower do not forter reduce the degradation from charging current, but theres a big difference in degradation between 0.3C and 1C charging.

Anyway, the cyclic part causes a small annual degradation. If you look at the 5-15% cycles, which loose ~ 15% for the first 1000 FCE, 1000 FCE equals ~ 400K km or 250K mi. This is somewhere around 20 years driving for the average car, so it still is an average of 0.75% per year.
After 20 years that battery would have about 9% calendar aging. ( square root(20) x 2)
Total degradation 15+9= 24%.
If you instead cycle 65-75% you would have 8% cyclic degradation and 22% calendar aging, so 30% total degradation.

The cyclic part might seem bad at the lower SOC in that picture but it will reduce the calendar aging more than it would increase the cyclic aging.

 

[AAKEE]

Although might be hard to get any of us to do it the simplest way. Most of us are in this thread because we are very much interested in overthinking it

I'm not drawing the entirely same conclusion from this study that you are. Here it says charging to 100% allows recovery of most of the capacity loss noticed.


Then at the end of the article it says

Can't we infer from this latter statement that we can optimize by shallow discharge cycles combined with charging to 100% sometimes? That's a little bit different than "cycling 0-100% like a gas car". Both charts 2a and 2c seem to show 0-100% cycles as resulting in the lowest capacity retention.

Yes, these losses was recoverable.
Reversible degradation is not an issue for us. Irreversible is.

One of my takeaways from the recuperation was made at having the cells rest for periods of low or high SOC (2V or 3.6V) and this showed that the recuperation at 2V was much better to help restoring the capacity.

Also, the lowest degradation in the whole test was the cells cycled at the lowest SOC, like 15-35% or so.

The thing Tesla need LFP owners to do is to charge full to reset the BMS counter.

It is actually not even the steper voltage in top that makes the day for the BMS (as it can not read the real cell voltage when supplying charge voltage), but holding the charging voltage at the max charge voltage until the decreasing carging current is low enough ascertains the battery is at 100%.

 

[randall_s]

As the buffer is fixed and the true SOC number do not work like 3/Y.
Almost looks like the true soc is [buffer size] higher than displayed and would show 105% at 100%.
We need to see and understand that relation to be able to find it out. I’s surecwe can figure it out together

This report (or these as it is a couple of reports) did not go very deep into it.
I know specifically NCA sometimes show a bit strange results with regard to the current rate.

I also know that at low SOC (~20% ish and lower) the batteries often is sensitive to high current.
They did all tests with 1C, which is = 80kW which would equal about driving at 200 kph.
The average driving we have, is like 70kph and 170 Wh/km or so. So like 10kW in average and ~120 Wh/km and 200Wh/km = 24 kW power.
This means we probably average about 0.12-0.3C current rate. I guess the chart would look slightly different for the lowest SOC’s if they had tested at lower current rates.

I recommend reading this research report.
Peter keil has done a lot on NCA cells.
Good work.
This report covers many aspects and use different load/current and different C-rates for charging.
Panasonic NCA so more close to model S from before. But tge main characteristics is about the same so.
Test report

Here 18650 NCA cycled down to 0% from different SOC, 4.25V is overcharged by ~2%.
Each 0.1V from 4.20V / 100% is about 10% change in SOC, so 3.7V about 50%.

Reducing the charging level reduces the degradation, as the cycles get smaller and the SOC gets lower. At 50-60% that reduction is dimished. We have a sign of the 2170 research test finding here.
View attachment 1014116

Heres a charge cycle test; the cells are 2.9Ah, so 1A = about 0.3C
0.3C and lower do not forter reduce the degradation from charging current, but theres a big difference in degradation between 0.3C and 1C charging.

View attachment 1014118



Anyway, the cyclic part causes a small annual degradation. If you look at the 5-15% cycles, which loose ~ 15% for the first 1000 FCE, 1000 FCE equals ~ 400K km or 250K mi. This is somewhere around 20 years driving for the average car, so it still is an average of 0.75% per year.
After 20 years that battery would have about 9% calendar aging. ( square root(20) x 2)
Total degradation 15+9= 24%.
If you instead cycle 65-75% you would have 8% cyclic degradation and 22% calendar aging, so 30% total degradation.

The cyclic part might seem bad at the lower SOC in that picture but it will reduce the calendar aging more than it would increase the cyclic aging.

This is very useful for EVs sold today with this chemistry. The obvious next question is what's primary cause of the degradation over time? I would be surprised if this hasn't already been identified and addressed at the lab stage. Here's one article about a "million mile battery".

Battery Power Online | Long-life and High-energy Batteries from Dahn and Meng

www.batterypoweronline.com

It's impressive what EVs can do today, but mind boggling to think of their potential. We could very well have affordable batteries that last as long as we do.

 

[AAKEE]

The obvious next question is what's primary cause of the degradation over time? I would be surprised if this hasn't already been identified and addressed at the lab stage.

Yes, the main thing is Solid Electrolythe build up.

 

[ran349]

As the buffer is fixed and the true SOC number do not work like 3/Y.
Almost looks like the true soc is [buffer size] higher than displayed and would show 105% at 100%.
We need to see and understand that relation to be able to find it out. I’s surecwe can figure it out together

Other than the fixed buffer size (4.0 kWh), the old MS cars calculate the SOC % and full pack value the same as the M3 does.
Unless they did something different for the performance models, which I don't think so but I guess it's possible.

 

[AAKEE]

Other than the fixed buffer size (4.0 kWh), the old MS cars calculate the SOC % and full pack value the same as the M3 does.

I do not seem like everything match. Maybe they used one of the other SOC numbers (SOC UI?) for the true SOC number?

The true SOC is 53.8/73.7 = 73.0%
A 3/Y would have SOC min at 73.0%

The displayed SOC (SOC in SMT) would be [ 73 - (5.4 - 0.054 x 73) = 71.5, which matches (probably small rounding error)

Unless they did something different for the performance models, which I don't think so but I guess it's possible.

 

[ran349]

I do not seem like everything match. Maybe they used one of the other SOC numbers (SOC UI?) for the true SOC number?

The true SOC is 53.8/73.7 = 73.0%
A 3/Y would have SOC min at 73.0%

The displayed SOC (SOC in SMT) would be [ 73 - (5.4 - 0.054 x 73) = 71.5, which matches (probably small rounding error)



View attachment 1014247

For the MS cars, SMT calculates SOC as (Nominal Remain - Buffer)/(Nominal Full - Buffer).
For this case that would be (53.8 -4.0)/(73.7 - 4.0). This equals 71.449 or 71.4, which matches the SMT readout.

However, for SMT SOC to match the car's display, the proper equation should be:
(Ideal Remain - Buffer)/(Nominal Full - Buffer).
I know this is true for my MS 70D. I use TM-Spy, which does the calculation correctly, and I have verified it many times.

But Ideal remain is not shown on the SMT readout here, so it can't be calculated to see what the car display was actually showing.
The car display is just the rounded version (no decimal places), of this value.

 

[Max Spaghetti]

It is actually not even the steper voltage in top that makes the day for the BMS (as it can not read the real cell voltage when supplying charge voltage), but holding the charging voltage at the max charge voltage until the decreasing carging current is low enough ascertains the battery is at 100%.

This is true, but I suspect is only part of the story.

The other would be that you can't balance cells effectively in LFP except at a high SOC, because it is only at that part of the charge curve that unbalanced cells show up with a significant voltage differential. I don't have a link for this - it's just my experience with building DIY LFP batteries.

When charging to 100% in my LFP M3 it sits at 99% for a while (e.g. 30 mins) saying "calibrating" before reaching 100%. It is my guess that it is finalising cell balancing during that time, which takes time as Tesla uses passive not active balancing (i.e. it discharges the high cells through a resistor rather than moving the charge from the high cells to the low cells).

 

[Bouba]

This is true, but I suspect is only part of the story.

The other would be that you can't balance cells effectively in LFP except at a high SOC, because it is only at that part of the charge curve that unbalanced cells show up with a significant voltage differential. I don't have a link for this - it's just my experience with building DIY LFP batteries.

When charging to 100% in my LFP M3 it sits at 99% for a while (e.g. 30 mins) saying "calibrating" before reaching 100%. It is my guess that it is finalising cell balancing during that time, which takes time as Tesla uses passive not active balancing (i.e. it discharges the high cells through a resistor rather than moving the charge from the high cells to the low cells).

That’s interesting and makes sense....if through degradation the battery is no longer able to charge to 100%...does that mean that it will never balance, or do it at a lower figure, or will it always show 100% ?

 

[AAKEE]

When charging to 100% in my LFP M3 it sits at 99% for a while (e.g. 30 mins) saying "calibrating" before reaching 100%. It is my guess that it is finalising cell balancing during that time, which takes time as Tesla uses passive not active balancing (i.e. it discharges the high cells through a resistor rather than moving the charge from the high cells to the low cells).

It is the same for non LFP cars.

A complete balancing takes much more time (of course depending on how much imbalanca there is, normally it takes several hours).

When a non LFP car says “calibrating” its normally in the end of the charging process where the cells are hold at the 100% cell voltage and the final charging is done (car waiting for the charging current to go below the threshold of decreasing current where the charging is considered finished.
(Just like any lithium battery charging process).

Of course there might be a slight balancing done by burning of voltage on the hogh cells at the same time as the others are continued to be charged but in 30 minutes we probably will not change the balance more than ~ 1 mV

I do not know why Tesla calls it “calibrating” in the end of the process.


Here's from a recent supercharging of my Plaid. (-35C outside when I started the short drive to the Supercharger, had been -41C during the night, car outside, preconditioned via the Plaid dragstrip mode, not a complete preconditioning).

The green line to the right is the "charge finished" message and I started driving asap).

You can see the imbalance ramping up to about 16mV and was about constant at 16mV for the last 15minutes of the charge, I charged to 100% and I think that calibrating text was visible for a while.
Amber = SoC
Yellow = Charge power
Red = Imbalance

 

[dakhlkt22]

This is true, but I suspect is only part of the story.

The other would be that you can't balance cells effectively in LFP except at a high SOC, because it is only at that part of the charge curve that unbalanced cells show up with a significant voltage differential. I don't have a link for this - it's just my experience with building DIY LFP batteries.

When charging to 100% in my LFP M3 it sits at 99% for a while (e.g. 30 mins) saying "calibrating" before reaching 100%. It is my guess that it is finalising cell balancing during that time, which takes time as Tesla uses passive not active balancing (i.e. it discharges the high cells through a resistor rather than moving the charge from the high cells to the low cells).

My 2023 M3 does the same when I am watching in TeslaFi. It reaches 100% but continues to be doing something for maybe 30 extra minutes before the Tesla app notifies me that the charge is completed.

 

[dakhlkt22]

View attachment 1014030
Based on figure 5, the recuperation by holding at 100% SOC (3.6V hold) was only able to recover <50% of the lost capacity after 35 days of continuous holding. The recuperation of 0% SOC was much more effective but is difficult to do in the real world. Unfortunately the authors glossed over the nuances here and just said "recuperation can recover lost capacity in a couple days", but that's only true for the 0% hold at elevated temperatures 45C.

The reversible degradation crossover b/w 40-60% and 0-100% cycling was at 7000 FEC which is greater than 1.5 million real world miles, which you will never reach.

It seems better to avoid the "reversible degradation" in the first place by having wide charging windows or taken to the max - cycling 0-100%. Yes you can recuperate but it doesn't seem as trivial as the authors suggest.

Maybe I missed it, or maybe the writing is a bit unclear, but I am assuming the capacity retention charts in Figure 2 are without any attempt at capacity recovery. It seems like the procedure to recuperate usable capacity involved taking certain cells and then performing recuperation experiments on them separately. There are many mentions of the recuperation experiments taking place on cells that were around 700 FEC. But I don't see any indication that this was done to all cells and that the charts in Figure 2 reflect cells that were recuperated.

So your point is well taken, recuperation would require experimental conditions that we have no way to replicate in the real world and therefore this recuperation strategy does not apply to us. So then it seems to me that what applies to us in the real world are the charts in Figure 2 which show the capacity retention for non-recuperated cells. If Figure 2 is for non-recuperated cells, then shallow cycling produces faster capacity loss initially, but over the long run (10,000 full equivalent cycles), it results in higher capacity retention.

 

[dakhlkt22]

View attachment 1014030
Based on figure 5, the recuperation by holding at 100% SOC (3.6V hold) was only able to recover <50% of the lost capacity after 35 days of continuous holding. The recuperation of 0% SOC was much more effective but is difficult to do in the real world. Unfortunately the authors glossed over the nuances here and just said "recuperation can recover lost capacity in a couple days", but that's only true for the 0% hold at elevated temperatures 45C.

The reversible degradation crossover b/w 40-60% and 0-100% cycling was at 7000 FEC which is greater than 1.5 million real world miles, which you will never reach.

It seems better to avoid the "reversible degradation" in the first place by having wide charging windows or taken to the max - cycling 0-100%. Yes you can recuperate but it doesn't seem as trivial as the authors suggest.

Someone just pointed out in another thread that we're not looking at 10,000 full equivalent cycles for a Tesla. A LFP M3 has nominal starting range of 272 miles. So 100,000 miles, 300,000 miles, and 500,000 miles are represented by 368 FEC, 1103 FEC, and 1838 FEC. So I think the reasoning of my previous post was correct but the conclusion is actually wrong. In the 300-1800 FEC range (which is relatively "young" compared to battery cells of 10,000 FEC), Figure 2a and 2c show that the 0-100% deep cycle strategy seems to be better for capacity retention.

This research gives a bit of a suggestion that someone could refurbish old Tesla LFP batteries simply by keeping them 100% charged at room temperature or higher for a month.

 

[randall_s]

Are you sure about that 310Wh/mi constant? It seems like it is more like 318Wh/mi. (176mi*307Wh/mi / 170mi).

You could try “driving to the line” (overlap the rated line exactly) and see what recent efficiency is when the two lines merge. Ideally with a smaller y-axis range, too, though it does not matter much. I’d expect it to overlap at 323Wh/mi not 318Wh/mi, but could be wrong.

Minor issue but good to get rid of unknowns.

Anyway, so you have about 74kWh-75kWh of pack (including the buffer).

This makes sense since you have around 236 rated miles at 100%, which is around 87% of your original 270 miles, which was something slightly north of 85.8kWh as covered in the articles above. (Not sure how to square the EPA results with the 90D of 84kWh which were slightly lower, but small difference.)

So something around 13% loss give or take a percent or so. Quite good.

Usable is around 70kWh.

Are you sure about that 310Wh/mi constant? It seems like it is more like 318Wh/mi. (176mi*307Wh/mi / 170mi).

You could try “driving to the line” (overlap the rated line exactly) and see what recent efficiency is when the two lines merge. Ideally with a smaller y-axis range, too, though it does not matter much. I’d expect it to overlap at 323Wh/mi not 318Wh/mi, but could be wrong.

Minor issue but good to get rid of unknowns.

Anyway, so you have about 74kWh-75kWh of pack (including the buffer).

This makes sense since you have around 236 rated miles at 100%, which is around 87% of your original 270 miles, which was something slightly north of 85.8kWh as covered in the articles above. (Not sure how to square the EPA results with the 90D of 84kWh which were slightly lower, but small difference.)

So something around 13% loss give or take a percent or so. Quite good.

Usable is around 70kWh.

I owe you an apology. It's 318 wh/mi. I took a trip today and caught it dead on.

 

[Max Spaghetti]

That’s interesting and makes sense....if through degradation the battery is no longer able to charge to 100%...does that mean that it will never balance, or do it at a lower figure, or will it always show 100% ?

100% represents the voltage of a nominally fully charged battery, so when the battery gets charged to full, the charging circuitry will apply a constant voltage (e.g. for LFP it might be 3.6V/cell - not sure what specific voltage Tesla uses), and it will apply that voltage until the cells absorb enough charge that the charging current drops off to a nominally small value. It then shuts off charging and the BMS declares the battery "full" i.e. 100%. Once the battery sits for a few hours, the cells will actually settle at around 3.4V/cell, but that's just the resting voltage. The cells are still 100% "full".

It doesn't matter if the battery has degraded, the cells will still charge to the same voltage (e.g. 3.6V) at full charge, and this voltage will always be represented by 100%. It's just 100% of a smaller capacity.

The simplified way to think about it is that a degraded cell functions the same as a new cell, it just has fewer useful (cooperative) lithium ions in it to store energy. Some of the lithium has gone on strike and won't work for you any more - so you don't have as many kWh in your battery - it's just become a smaller battery, so will drop from 100% to 0% more quickly than a new battery.

 

[AlanSubie4Life]

I owe you an apology. It's 318 wh/mi. I took a trip today and caught it dead on.

I’ve kind of lost track on this thread, but it may be that unlike on Model 3, for Model S that line is exactly where the calculations would predict it to be (for Model 3 the line is always 5Wh/mi higher than the constant and no idea why). Anyway 318Wh/mi *270mi = 85.8kWh which does align with the earlier linked article for the degradation threshold. 270 miles is EPA. So that 318Wh/mi IS what I would expect for the correct position (in Model 3 that would end up at 323Wh/mi (+5Wh/mi) for “reasons” but that is a distraction here…but we are in a Model 3 forum so for clarity - obviously no Model 3 has anything near that high ), and aligns with the earlier photos you posted.

Thanks for confirming. Everything always works out perfectly!