Battery health tracking SS

[AAKEE]

Is that battery than average? If not, does that mean that only charging to 50% most days didn't really do anything to help slow down degradation?

Yes, in a normal average climate you can expect around 5-6% the first year from calendar aging.
Having that battery at or below 55% you cut it in half, so 2.75% is expected the first year instead of 5.5% for calendar aging.

I know Texas/Dallas area and it is quite warm over the year.

The average cell temp in my (cold) place seems to be around 5C above the average ambient, seen from logs of BMS-data.

I have tested having my car out in very sunny weather with the sun as high as it gets at our place ande the cell temp seem to top out 9-10C above ambient. Not big differences between Model 3 and new S.

So to have an estimate of the average cell temp we need the average annual temp for that place and add more than 5C for Texas.

So, I guess you are below half or better by being at 3% loss as @alansubie says.
All of your reduced degradation comes from low SOC, and 0% from luck

Keep on being nice to the battery, and it will be nice back.

 

[Chrushev]

I feel like none of this really matters. You cant keep the battery from degrading. You can slow it down, but with natural slowing of degradation over time you may only help the battery degrade enough to make any difference in the first year, but over the course of 10+ years. Does that little difference even matter? 1 Kwh is 3 to 4 miles. At the end of 10 years having an extra few miles of range wont matter. If you need new battery you need new battery, thats it. You wont be ok with 100 mile range but not ok with 95 mile range. When we talk about range we typically talk in 50 to 100 mile increments, because they are useful. And I am not sure that a battery that has always been kept to 50% vs battery that has always been kept to 80% will have such a high difference in capacity since we are talking fractions of a percent improvement to battery health... which is literally just watts, not even a single kW. So maybe a mile difference per year a few years into the battery's life? 10 years.. maybe 3 to 5 mile difference?

Besides, charging is only one of many variables, which in itself has variables such as speed of charging, lvl 2 or supercharger. But then there is also discharge rate (driving up and down mountains), city driving vs freeways, temperatures, parking in hot sun 9 hours a day or in a garage, randomness of each battery's chemistry, depth of discharge, not all cells degrade at the same rate even within the same pack, etc... I feel like among all the variables keeping your battery to 50% as opposed to 80%, in 10+ years its not something that can be calculated to be beneficial or not in the grand scheme of things.

Honestly a car with a battery that is always charged to 80% but sits in a covered garage may be better off than a car that is always charged to 50% and sits out in the sun for 9 hours a day.

Like someone else made a paint and washing example.. yeah. on paper handwashing is always 100% better than automatic car wash... but is it? Im sure there are automatic car washes that leave the car perfect, never scratch it and wash it perfectly, and there are always people that handwash and scratch/swirl the crap out of their paint. Calculations on paper does not always match reality.

Lastly, as someone else pointed out, none of this will make any impact on resale value of the car, you wont be able to get more for an extra 5 to 10 miles of range, and the car isnt priced just based on the battery, areas with salt on roads in the winter could have way bigger problems than the battery pack in 10+ years. The total mileage will play a bigger role because thats cycles on the battery, quality of those cycles cant be proven and would be way down the list of priorities for a buyer. But I also get the idea of doing it for yourself, so whoever wants to do it, all power to you.

I look at it this way. In 10 years if rest of the car is in good shape, paying $10k for a new battery is nothing if it means like basically buying a brand new $60k car. Thats a steep discount.

 

[dansev]

I feel like none of this really matters. You cant keep the battery from degrading. You can slow it down, but with natural slowing of degradation over time you may only help the battery degrade enough to make any difference in the first year, but over the course of 10+ years. Does that little difference even matter? 1 Kwh is 3 to 4 miles. At the end of 10 years having an extra few miles of range wont matter. If you need new battery you need new battery, thats it. You wont be ok with 100 mile range but not ok with 95 mile range. When we talk about range we typically talk in 50 to 100 mile increments, because they are useful. And I am not sure that a battery that has always been kept to 50% vs battery that has always been kept to 80% will have such a high difference in capacity.

Besides, charging is only one of many variables, which in itself has variables such as speed of charging, lvl 2 or supercharger. But then there is also discharge rate (driving up and down mountains), city driving vs freeways, temperatures, parking in hot sun 9 hours a day or in a garage, randomness of each battery's chemistry, depth of discharge, not all cells degrade at the same rate even within the same pack, etc... I feel like among all the variables keeping your battery to 50% as opposed to 80%, in 10+ years its not something that can be calculated to be beneficial or not in the grand scheme of things.

Like someone else made a paint and washing example.. yeah. on paper handwashing is always 100% better than automatic car wash... but is it? Im sure there are automatic car washes that leave the car perfect, never scratch it and wash it perfectly, and there are always people that handwash and scratch/swirl the crap out of their paint. Calculations on paper does not always match reality.

Lastly, as someone else pointed out, none of this will make any impact on resale value of the car, you wont be able to get more for an extra 5 to 10 miles of range, and the car isnt priced just based on the battery, areas with salt on roads in the winter could have way bigger problems than the battery pack in 10+ years. The total mileage will play a bigger role because thats cycles on the battery, quality of those cycles cant be proven and would be way down the list of priorities for a buyer. But I also get the idea of doing it for yourself, so whoever wants to do it, all power to you.

I look at it this way. In 10 years if rest of the car is in good shape, paying $10k for a new battery is nothing if it means like basically buying a brand new $60k car. Thats a steep discount.

I pretty much agree with all of this. But I will say, as I don’t mind playing the game of charging to 55% normally, and then 70, 80, 90 or above when necessary, mentally that helps me feel better about my investment. And my mental health is important to me! So if it reduces stress then why not do it. But I will say that charging to 50% will almost inevitably cause problems at some point. There will be a time that you will forget to charge higher, and it will bite you. It’s happened to me a few times over the years.

This is almost certainly why Elon has always said to charge to 80% and to plug-in whenever, you’re at home. Ultimately, he knows what you have said in this post above. In the end, the battery is going to degrade to some point, and even though some of us might keep it in better shape, ultimately, it’s all within a few percentages of each other.

If my parents got a Tesla, I would never tell them to charge it to 50%. There’s no way they could handle that game. But for me, I enjoy the game, and enjoy looking at the stats and knowing that my battery is doing as well or better than some other people in the same boat. Even If it is only a small percentage difference!

 

[AAKEE]

I feel like none of this really matters.

It is of course a matter of choice.

You cant keep the battery from degrading. You can slow it down, but with natural slowing of degradation over time you may only help the battery degrade enough to make any difference in the first year, but over the course of 10+ years. Does that little difference even matter? 1 Kwh is 3 to 4 miles. At the end of 10 years having an extra few miles of range wont matter.

The industry standard for considering a lithium ion battery consumed is 20% degradation. The reason for this is that up to around 20% degradation the degradation is predictable.

After passing 20% degradation the degradation is less predictable.
We only need a few cells out of 4-8000 cells that starts to go bad and then we have issues.

During the same conditions (climate etc) a car charged daily which reaches 20% degradation might be good further on or might not be.
At the same time a car charged with low SOC daily will have around 10% degradation. So the battery will be very fresh.

I probably will not drive the Tesla I have today beyond 10 years age, still I would feel bad to having it degrade with double rate during the years I will have it.

Just following Teslas simple/few advices will most probably make the battery hold up for the warranty period so there is absolutely no need to reduce the degradation. But long term, someone will own it at that age and someone will in some cases need a new pack, or not.

 

[Chrushev]

It is of course a matter of choice.


The industry standard for considering a lithium ion battery consumed is 20% degradation. The reason for this is that up to around 20% degradation the degradation is predictable.

After passing 20% degradation the degradation is less predictable.
We only need a few cells out of 4-8000 cells that starts to go bad and then we have issues.

During the same conditions (climate etc) a car charged daily which reaches 20% degradation might be good further on or might not be.
At the same time a car charged with low SOC daily will have around 10% degradation. So the battery will be very fresh.

I probably will not drive the Tesla I have today beyond 10 years age, still I would feel bad to having it degrade with double rate during the years I will have it.

Just following Teslas simple/few advices will most probably make the battery hold up for the warranty period so there is absolutely no need to reduce the degradation. But long term, someone will own it at that age and someone will in some cases need a new pack, or not.

Im not sure that you can say with confidence that charging to 50% will degrade it 10% and charging to 80% will degrade it 20%. The studies are done in an environment where the battery has no other influence. Are they putting the battery through cycles? Or are they charging it to 50% and leaving it there in a controller environment and then seeing degradation? Are they putting the battery through +- 20 Degrees of temperature daily (day/night cycles)? Is there a on/off load on the battery in the lab? Like there is in a car when it wakes up and performs functions?

Are they charging the battery at different rates (home vs supercharger) throughout testing? Are they extrapolating data beyond 1 year? Meaning its educated guessing? All of this means you absolutely cannot compare the studies degradation numbers to real life car's degradation numbers. And this is kind of confirmed with the whole thing about field data from actual cars (including Tesla) does not match exactly lab studies.

A car is a much more complex system than charging up a battery pack and having it sit in a controlled environment. For instance a few things spring to mind.

1. Are you introducing other issues? For example if BMS is programmed to balance at certain SoC? So then a car at higher SoC will have more frequent balancing which may or may not keep battery in better shape?

2. Are you damaging the 12v battery because DC to DC charging of it requires certain SoC?

There are so many variables. We cant say anything for certain. Most of the data is extrapolated and tests performed in environments not compatible with what we are trying to apply to here. I dont think there is any basis to claim half degradation at lower SoC as pertains to a car (as opposed to a cold storage battery).

As seen from the graph below, high mileage has a much higher impact on battery degradation than age. Look at 7 year bucket which has low mileage cars.

I wont believe for a second that a 10 year old Tesla that was charged to 80% has 20% degradation, but another 10 year old tesla that was charged to 50% has 10% degradation. That simply is not possible.

Here is a guy reporting that after 10 years, charging to 90% almost every day for 10 years, and after 100k miles he has 6% degradation on his Model S. What does that tell us? If those numbers are correct that means we can take those battery studies in lab environment and throw them in the trashcan when it comes to our cars. And there are many stories like this (regarding degradation, both for age and for mileage)

Some real life data from nearly 2000 Tesla owners: Tesla Batteries

Important thing to see there is that out of hundreds of people that charge to exact same level daily you have wildly different degradation. Again, not surprising considering how many variables there are with a car battery vs a battery stored in a lab. And when you see someone say they have low degradation and they charged to low SoC.. thats just confirmation bias. Those results are not repeatable.

 

[AAKEE]

Im not sure that you can say with confidence that charging to 50% will degrade it 10% and charging to 80% will degrade it 20%. The studies are done in an environment where the battery has no other influence. Are they putting the battery through cycles?

The research are extensive. It is work of science. You can be sure that the sum of the research is valid.

The cells where calendar aging are tested are tested st many different temperatures and different SOC, even if it will make any difference if the cells are charged to for example 70% or discharged to 70%.

Or are they charging it to 50% and leaving it there in a controller environment and then seeing degradation? Are they putting the battery through +- 20 Degrees of temperature daily (day/night cycles)? Is there a on/off load on the battery in the lab? Like there is in a car when it wakes up and performs functions?

Science split the degradation into calendar aging (”time”) and cyclic aging (charging/discharging).

The mechanisms for degradation from calendar aging is looked into, so knowing these we can safely say that calendar aging works in a certain way.
The same is valid for cyclic aging.

Are they charging the battery at different rates (home vs supercharger) throughout testing?

There are tests for all different charge rates, in different temperatures etc.
So the mechanisms behind degradation from fast charging is found and known (mainly lithium plating).
The possibility for a cell to revert from for example lithium plating is also tested and the mechanisms behind this is known.

Are they extrapolating data beyond 1 year? Meaning its educated guessing?

For cycles they most often cycle the cells more than you ever will be cycling your cells in any EV ever. So the cyclic data is actual test data.
For calendar aging the most tests are 1-2 years. But there are tests for fice years as well.
As the mechanism behind calendar aging is known, 1 year is good enough and two or five years only confirm what we already know.
We do not need a ten tear test as it will only confirm the square root behaviour. The reason for the square root behaviour is known, and matches the basic math from that. Calendar aging and nice cycles build Solid Electrolyte Interphase (SEI), which consumes lithium to build. At the same tine the SEI scts as a protection from furter SEI build up so the rate of SEI build up gets slower and slower.

All of this means you absolutely cannot compare the studies degradation numbers to real life car's degradation numbers.

Nope, thats wrong.

Its exactly the opposite. Despite many many different ways if testing the results are very close.
We can predict how a EV battery will degrade frommthe test data.

And this is kind of confirmed with the whole thing about field data from actual cars (including Tesla) does not match exactly lab studies.

That is also wrong.

The actual cars degradation matches the research very well.

A car is a much more complex system than charging up a battery pack and having it sit in a controlled environment. For instance a few things spring to mind.

1. Are you introducing other issues? For example if BMS is programmed to balance at certain SoC? So then a car at higher SoC will have more frequent balancing which may or may not keep battery in better shape?

2. Are you damaging the 12v battery because DC to DC charging of it requires certain SoC?

There are so many variables. We cant say anything for certain. Most of the data is extrapolated and tests performed in environments not compatible with what we are trying to apply to here. I dont think there is any basis to claim half degradation at lower SoC as pertains to a car (as opposed to a cold storage battery).

A cell will behave the same way in a pack even if there is a BMS looking after it.
Just like your doctor can not stop ypu from aging, the BMS can not.
Calendar aging and cyclic aging will about the same.

I wont believe for a second that a 10 year old Tesla that was charged to 80% has 20% degradation, but another 10 year old tesla that was charged to 50% has 10% degradation. That simply is not possible.

You better start to believe it, or get a hat built from aluminium foil.

It is the real world and it works like that.
I only had my M3P for 2.5 years but the degradation was less than half compared to other cars. With data from the new owner I know that is still is very much better than the other M3Ps with the same battery, now at 3.5 years.

The same is valud for my one year old MSP.
Other MSP’s in the area has much more than the double degradation after the same time.
And we also start to have a descent amount of cars hete at TMC ising this technique and having really low degradation.

Are you thinking these cars suddenly at some point will increase the degradation rate by far to be at the same level on the 10:th anniversary?



The Tesla battery degradation chart you used most probably only show the reduction in displayed range (as more or less all of these use range data and not BMS capacity numbers).
As the car starts with an overhead to the displayed range, the capacity can drop a few percent without the range dropping. This effectively hides the first degradation but still the battery looses capacity so there is a real loss of these percebts in real range.

 

[AAKEE]

Here is a guy reporting that after 10 years, charging to 90% almost every day for 10 years, and after 100k miles he has 6% degradation on his Model S. What does that tell us?

Theres a lot of people in for example Facebook groups that state very low degradation. When “confonting” and asking for real data they all state the same thing. They did not understand what they saw.

For the S85, we do not know which setting the owner use to display the range, and I guess we has not even seen any proof of the number he states.
So until we get pictures from hes energy graph or scan my tesla togheter with a picture of the battery sticker I call 6% after 10 years bullshit, actually.

S85 actual data from teslalogger - it is BMS data via scan my tesla.
Original range 265 miles/426 km.
( source: teslalogger.de)

350km out of 426 is 18% loss, plus the hidden part because of the degradation threshold.

Teslafi data also support the same rates as the research finds.

What car do you have?
I can calculate the degradation/remaining capacity but if I do we need to get the real data confirmed by for example a picture of the energy graph or scan my tesla nomimal full pack.

 

[Chrushev]

I dont think you understood what I was saying. What I was saying is that lab tests charge up a battery and let it sit in a controlled environment in order to test aging degradation. This cant be applied to a car. There probably is even a little sentence or two on the lab study stating how the results cant be directly translated to real world, because in the lab you have 2 variables, SoC and Temp. In the world you have 1000 variables.

Im not disputing lab results in any way. I agree with them. I am just saying that its apples to oranges when comparing that data to how a car's battery will behave. And this is confirmed by same mileage and same age, same charge treshold Teslas having different degradation levels. There are too many variables beyond just how high you charge it to be able to definitively say how much degradation you will have.

I drive a 2020 Model Y LR. Ill provide whatever data you want but I dont pay for Tesla Fi or anything like that. Ive been charging to 70% and have 21k miles on it in 4 years. I cant tell you that I have noticed any significant degradation. A couple of times per year I do ~500 mile one way trips. Outside of this its mostly street driving. When I charge to 100% my estimated range is still over 300 miles (not surprising at all since mileage is what most people drive in 1 year, therefore low charge cycle count). In real life I probably get about 270 miles out of a full pack, and thats how much I got out of it when the car was brand new, no real change in 4 years. Car is parked in a garage at work and at the house, so it rarely is sitting in the sun.

Ill put it this way. On my 500 mile trips I do 1 stop to charge at supercharger, and doing this trip multiple times a year for 4 years, from when the car was brand new to now 4 years old... I still need only 1 charge and me arriving at my destination the charge level remaining is all within the margin of extra usage because it was head-wind vs tail-wind. One year Ill arrive with 5%, another with 10%, even though I charged to same levels at home (100% before leaving) and same level at supercharger. Its a difference a wind direction makes.

Bottom line, I think regardless if you charge to 50% or 80% you will still have between 15% and 20% degradation in 10 years. Because other factors make the charge level pretty much irrelevant. yes they make a difference, but in grand scheme of things other factors dictate the degradation (mainly cycles/mileage, temperatures, supercharger use... etc).

 

[AAKEE]

I dont think you understood what I was saying. What I was saying is that lab tests charge up a battery and let it sit in a controlled environment in order to test aging degradation. This cant be applied to a car. There probably is even a little sentence or two on the lab study stating how the results cant be directly translated to real world, because in the lab you have 2 variables, SoC and Temp. In the world you have 1000 variables.

Calendar aging only have two variables, SOC and Temperature.

There are no other important values really.

The battery in the carwill degrade according to the SOC and temperature of the cells for each secomd regarless of if it is parked for 5 minutes, or 5 days.

The charts are valid. .

I drive a 2020 Model Y LR. Ill provide whatever data you want but I dont pay for Tesla Fi or anything like that.

Good. We do not need teslafi or scan my tesla etc, I only used them as references to data that fully match the research.

You live in California? The climate about at tour place about average for CA? (If you like you can specify the area or city so I can grab the approx average ambient temp.)

When do you charge on the day mostly? Like when arriving from work or in the middle of the night, or morning?

Do you have a garage, where you park? Insulated or not?

I can do a calc with the data above and the daily charge level 70%.
The number of Supercharges would not affect the result noticeable.
If you have the life time consumption I could used that, otherwise I will guesstimate that. Will not affect the calculation much
(it is used to find the approx number of cycles your battery have).

We will find out your batterys actual capacity by using data from the energy screen. But we better do that after I posted the calculations

Ive been charging to 70% and have 21k miles on it in 4 years. I cant tell you that I have noticed any significant degradation. A couple of times per year I do ~500 mile one way trips. Outside of this its mostly street driving. When I charge to 100% my estimated range is still over 300 miles (not surprising at all since mileage is what most people drive in 1 year, therefore low charge cycle count). In real life I probably get about 270 miles out of a full pack, and thats how much I got out of it when the car was brand new, no real change in 4 years. Car is parked in a garage at work and at the house, so it rarely is sitting in the sun.

We will se the actual degradation later.

Bottom line, I think regardless if you charge to 50% or 80% you will still have between 15% and 20% degradation in 10 years. Because other factors make the charge level pretty much irrelevant. yes they make a difference, but in grand scheme of things other factors dictate the degradation (mainly cycles/mileage, temperatures, supercharger use... etc).

There is sufficient data from the research + logged data from cars that tell us that the research is valid and can be applied on actual cars usage.
I would say that we also have enough data on actual cars here on TMC to see the connection between low SOC and low degradation and that it is in perfect line with the research.
You might wanna do a search here.

In the end there is no hesitation that the cars batteries actually follows the research data.
The only thing one meed to make an own reflection about (knowing the difference between degradation with high or low SOC) is if you are happy with the higher degradation comming from *using the usual 80%* or if you like to reduce the degradation.
Both these approaches are OK. We all have different approaches and needs, so basically you need to decide for your self.

As the research community does not scream out the result all over the world most people only see what media writes and very much of the EV mefia is cought by the same myths that most people are.

My goal is to kill the myths, which for example get people to think that 80% is the magic number for low degradation. Which it absolutely is not, as 80% in several cases causes more degradatiom than 100% (this does not mean I recommend using 100% all the time).

This is my MSP ome year after dekivery.
Using the research data I constructed formulas for calendar/cyclic aging and I just put in my data with average cell temp a d average SOC which I have looged.
Except for the initial swing where the BMS clearly was of at delivery, its a perfect match.
At this rTe, I already is at less than half the degradation other similar cars mearby has.

 

[Steve446]

I dont think you understood what I was saying. What I was saying is that lab tests charge up a battery and let it sit in a controlled environment in order to test aging degradation. This cant be applied to a car. There probably is even a little sentence or two on the lab study stating how the results cant be directly translated to real world, because in the lab you have 2 variables, SoC and Temp. In the world you have 1000 variables.

Im not disputing lab results in any way. I agree with them. I am just saying that its apples to oranges when comparing that data to how a car's battery will behave. And this is confirmed by same mileage and same age, same charge treshold Teslas having different degradation levels. There are too many variables beyond just how high you charge it to be able to definitively say how much degradation you will have.

I drive a 2020 Model Y LR. Ill provide whatever data you want but I dont pay for Tesla Fi or anything like that. Ive been charging to 70% and have 21k miles on it in 4 years. I cant tell you that I have noticed any significant degradation. A couple of times per year I do ~500 mile one way trips. Outside of this its mostly street driving. When I charge to 100% my estimated range is still over 300 miles (not surprising at all since mileage is what most people drive in 1 year, therefore low charge cycle count). In real life I probably get about 270 miles out of a full pack, and thats how much I got out of it when the car was brand new, no real change in 4 years. Car is parked in a garage at work and at the house, so it rarely is sitting in the sun.

Ill put it this way. On my 500 mile trips I do 1 stop to charge at supercharger, and doing this trip multiple times a year for 4 years, from when the car was brand new to now 4 years old... I still need only 1 charge and me arriving at my destination the charge level remaining is all within the margin of extra usage because it was head-wind vs tail-wind. One year Ill arrive with 5%, another with 10%, even though I charged to same levels at home (100% before leaving) and same level at supercharger. Its a difference a wind direction makes.

Bottom line, I think regardless if you charge to 50% or 80% you will still have between 15% and 20% degradation in 10 years. Because other factors make the charge level pretty much irrelevant. yes they make a difference, but in grand scheme of things other factors dictate the degradation (mainly cycles/mileage, temperatures, supercharger use... etc). Also, "....Teslas having different degradation levels

Now here's a thing, Your comments are heavy with opinion or causual observation but you are not heavy on facts. An example is your comment above, "I can't tell you that I have noticed any significant degradation". Of course you won't - the OS operates in manner that tends to hide capacity reduction over the first few years of use ( example, "degradation threshold" often referred to in this forum). Your battery though will still have lost capacity in that time. Also, ".....Teslas having different degradation levels". Yes that's sometimes true for same distance driven and age but only because some owners have absolutely hammered their cars and killed their batteries as can be shown from, lab tests.

By all means challenge comments and facts but please do so from a position evoking knowledge rather than opinion!

 

[AAKEE]

I drive a 2020 Model Y LR. Ill provide whatever data you want but I dont pay for Tesla Fi or anything like that. Ive been charging to 70% and have 21k miles on it in 4 years.

Car is parked in a garage at work and at the house, so it rarely is sitting in the sun.

Based on the average ambient temp in CA, taking into account that you park in a garage mostly I used slightly lower average cell temp (20C instead of 25C) than usual, and 70% charging schedule.
I assumed you start to charge in the evening.
Also, with only 21K mi you probably do not average below 60% in the end of the day.

The initial number is taken from the BMS Full Pack When New number. IRL the most of the old Panasonic packs delivered slightly more on the EPA test. 2020 Y LR delivered 78.3kWh, thats ~ 0.5kWh more than the specification so the initial number probably should be about 0.5 kWh higher, rendering the todays capacity 0.5 kWh higher.


Now we need to compare the actual capacity of ypur car with the bottom line in the picture.

You take a picture like this and post it here:
State of charge, average consumption and calculated range visible on the same picture. Selection down right must be normal range. Thats it, then we can calculate your actual capacity and we can compare that with the research data.

 

[KenBlub]

The research are extensive. It is work of science. You can be sure that the sum of the research is valid.

The cells where calendar aging are tested are tested st many different temperatures and different SOC, even if it will make any difference if the cells are charged to for example 70% or discharged to 70%.

Science split the degradation into calendar aging (”time”) and cyclic aging (charging/discharging).

The mechanisms for degradation from calendar aging is looked into, so knowing these we can safely say that calendar aging works in a certain way.
The same is valid for cyclic aging.

There are tests for all different charge rates, in different temperatures etc.
So the mechanisms behind degradation from fast charging is found and known (mainly lithium plating).
The possibility for a cell to revert from for example lithium plating is also tested and the mechanisms behind this is known.


For cycles they most often cycle the cells more than you ever will be cycling your cells in any EV ever. So the cyclic data is actual test data.
For calendar aging the most tests are 1-2 years. But there are tests for fice years as well.
As the mechanism behind calendar aging is known, 1 year is good enough and two or five years only confirm what we already know.
We do not need a ten tear test as it will only confirm the square root behaviour. The reason for the square root behaviour is known, and matches the basic math from that. Calendar aging and nice cycles build Solid Electrolyte Interphase (SEI), which consumes lithium to build. At the same tine the SEI scts as a protection from furter SEI build up so the rate of SEI build up gets slower and slower.

Nope, thats wrong.

Its exactly the opposite. Despite many many different ways if testing the results are very close.
We can predict how a EV battery will degrade frommthe test data.



That is also wrong.

The actual cars degradation matches the research very well.

A cell will behave the same way in a pack even if there is a BMS looking after it.
Just like your doctor can not stop ypu from aging, the BMS can not.
Calendar aging and cyclic aging will about the same.

You better start to believe it, or get a hat built from aluminium foil.

It is the real world and it works like that.
I only had my M3P for 2.5 years but the degradation was less than half compared to other cars. With data from the new owner I know that is still is very much better than the other M3Ps with the same battery, now at 3.5 years.

The same is valud for my one year old MSP.
Other MSP’s in the area has much more than the double degradation after the same time.
And we also start to have a descent amount of cars hete at TMC ising this technique and having really low degradation.

Are you thinking these cars suddenly at some point will increase the degradation rate by far to be at the same level on the 10:th anniversary?



The Tesla battery degradation chart you used most probably only show the reduction in displayed range (as more or less all of these use range data and not BMS capacity numbers).
As the car starts with an overhead to the displayed range, the capacity can drop a few percent without the range dropping. This effectively hides the first degradation but still the battery looses capacity so there is a real loss of these percebts in real range.

I can absolutely confirm this. 11 month old Model 3 LR. Just took a long trip and charged to 100%. My daily charge is 50% with LG battery. Car said I had 331 (of 333) miles but my energy screen calculation was 77.55 out of 78.8. Very happy with 1.6% degradation after almost 1 year. Average daily temperature where I live is 55F

 

[AAKEE]

I can absolutely confirm this. 11 month old Model 3 LR. Just took a long trip and charged to 100%. My daily charge is 50% with LG battery. Car said I had 331 (of 333) miles but my energy screen calculation was 77.55 out of 78.8. Very happy with 1.6% degradation after almost 1 year. Average daily temperature where I live is 55F

Yes, I have a bunch of friends and collegues using low SOC on the LG packs.

They respond very nice to the low SOC technique, even cars driven more miles each year does it.

And the cars using the usual 80% see at least the double rate.

 

[Chrushev]

Calendar aging only have two variables, SOC and Temperature.

There are no other important values really.

The battery in the carwill degrade according to the SOC and temperature of the cells for each secomd regarless of if it is parked for 5 minutes, or 5 days.

Again we are not understanding each other. Of course for aging there are only 2 variables SoC and Temperature. BUT in your car those are not the only variables. Aging is not the only thing that impacts degradation. In a lab, aging IS the only thing that impacts degradation, with a car there are too many variables.

I suspect your graph aligns with your extrapolation only because its been a short period of time (less than 2 years), when degradation is so big that imprecision of your calculation is hidden by impact from other variables. I expect as time goes on your lines to start diverging.

As for your questions. Average winter temp here is 60F, average summer temp is 72F. But garage can heat up in the summer too.

Ill take a picture of that screen when I go to my car later today, in meantime can you explain how you do the calculation? It seems like that screen numbers would be heavily impacted by driving terrain (going up hill for example). For instance driving from California out East you will go ~1000 miles of constant elevation gain, versus driving the other way its ~1000 miles of elevation loss. Also style of driving (Chill mode vs Normal)

 

[Chrushev]

Now here's a thing, Your comments are heavy with opinion or causual observation but you are not heavy on facts. An example is your comment above, "I can't tell you that I have noticed any significant degradation". Of course you won't - the OS operates in manner that tends to hide capacity reduction over the first few years of use ( example, "degradation threshold" often referred to in this forum). Your battery though will still have lost capacity in that time. Also, ".....Teslas having different degradation levels". Yes that's sometimes true for same distance driven and age but only because some owners have absolutely hammered their cars and killed their batteries as can be shown from, lab tests.

By all means challenge comments and facts but please do so from a position evoking knowledge rather than opinion!

Heres the thing, I made it clear that its my opinion and did not try to prove it as anything, just shared my experience while also saying Im willing to provide whatever is needed to calculate the actual thing. So why you are acting as if I am saying I have no degradation based on anecdotal evidence is beyond me. I think it was clear its just an anecdote.

But you completely sweeped under the rug my argument that while in the lab SoC and temp are the only variables, when it comes to your car those are NOT the only variables for degradation. So its comparing apples to oranges. Lab tests give you an idea for aging, but its just one of many pieces of the puzzle. How this is not understood is beyond me.

You are treating the lab results and applying them to Tesla's degradation as if batteries have infinite charge cycles and the only things that affect them is SoC and temp. Thats just simply not true, and thats a fact.

 

[AlanSubie4Life]

Ill take a picture of that screen when I go to my car later today, in meantime can you explain how you do the calculation? It seems like that screen numbers would be heavily impacted by driving terrain (going up hill for example). For instance driving from California out East you will go ~1000 miles of constant elevation gain, versus driving the other way its ~1000 miles of elevation loss. Also style of driving (Chill mode vs Normal)

None of that matters. The energy screen takes a version of remaining available energy (it actually takes remaining rated miles multiplied by the vehicle rating constant, which is not exactly remaining energy, but never mind, that is how it works and it does not matter) and divides by recent efficiency to give the projection.

So you just take that energy at a given SOC and extrapolate to 100% and it gives the correct value.


Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen

You’ll likely find your results are well matched to @AAKEE ’s calculations within a percent or two. We’ll see.

My WAG is 72kWh for your pack. (This could be as much as 9% loss.)

You are treating the lab results and applying them to Tesla's degradation as if batteries have infinite charge cycles and the only things that affect them is SoC and temp. Thats just simply not true, and thats a fact.

There are various sources of capacity loss as you say. It turns out that in typical use cases calendar aging is (by far) the dominant factor over the first few years at least. This would not be the case for someone who drives 150k miles a year, most likely, but that is fairly unusual.

 

[AAKEE]

Again we are not understanding each other. Of course for aging there are only 2 variables SoC and Temperature. BUT in your car those are not the only variables. Aging is not the only thing that impacts degradation. In a lab, aging IS the only thing that impacts degradation, with a car there are too many variables.

You would need to explain what more variables you think affect calendar aging in-car?

I suspect your graph aligns with your extrapolation only because its been a short period of time (less than 2 years), when degradation is so big that imprecision of your calculation is hidden by impact from other variables. I expect as time goes on your lines to start diverging.

I’m on a holiday trip, with the NAS shut down so I will not get my excel for the M3P.
It follower the line very well, and after checking with the new owner, it still does after 3.5 years from new.

I have done calcs on rather old teslas and for the absolute most of these, the match is good. This is because the degradation is predictable. We know this as the research test match very close from test to test.

As for your questions. Average winter temp here is 60F, average summer temp is 72F. But garage can heat up in the summer too.

We have some 5C higher than average from usage (driving and charging). I adjust that number slightly down for a car that has been sparingly used.
Cars out in the sun in general seem to catch 5-10C extra heat on the battery from heating.
In your case I used ~ 5-6C over the ambient annual average in CA.
(The hardest thing is to find the average cell temp, when not having it from teslalogger or something like that).
5C or so wrong doesnt put the calc very much of, so not extremely important.)

Ill take a picture of that screen when I go to my car later today, in meantime can you explain how you do the calculation?

I have used the sum of several research reports for Panasonic NCA cells.
(I also bought 35 Panasonic NCA 2170 cells from two different batches and made a few tests myself. Mostly because I was often met by the argument that the research tests was not made on real Tesla cells. My tests match these extremely well:
(Yes, 100% did wear less for me as well).


From all the tests, I created an average for different SOC’s and temperatures, as good as I could making it match as good as possible.
For the cyclic aging I made the same thing, matching different tests for depth of discharge, C-rates and found an average for this as well.
All this is by matematics put info formulas so I input the average cell temp, the normal charging level, also the end of the day SOC and the time the charging commences (affects the time at high SOC).
I did not separate different charge powers as about 0.3C ( ~25kW on a 3/Y) or lower does’nt make any difference in cyclic aging, its all the same.

For driving cycles, any discharge below 1C (75-80kW on a 3/Y) or so will make about the same degradation.
Shorter bursts like 5-10s with full power might not affect the pack very much.

For chill vs normal/sport mode, it could be worth knowing that many tests show the same degradation for discharge rates up to 2C (~ 150-160kW).
Most people, even I liking high power, might use the power from time to time but in the long run the absolute most part of the cycles would be ”gentle” in a degradation.

It seems like that screen numbers would be heavily impacted by driving terrain (going up hill for example). For instance driving from California out East you will go ~1000 miles of constant elevation gain, versus driving the other way its ~1000 miles of elevation loss. Also style of driving (Chill mode vs Normal)

The screen numbers (we’re talking about the energy screen, right) is using the BMS data for ”nominal remaining energy” as the source.
The nominal remaining is calculated by the BMS by taking the ”nominal full pack” (BMS estimate for battery capacity) times the number for SOC in absolute terms.
Having 100kWh capacity and 50% SOC makes 50kWh nominal remaining.

That number is split by the average consumption and the result is the actual range.

Working this backwards, average times calculated range = energy on board. = nominal remaining.
Again, backwards, nominal remaining divided by SOC = nomimal full pack.

There are a few roundings, but as long as SOC isnt too low the value is going to be close to the BMS estimated capacity.

 

[AAKEE]

@Chrushev

I am finding it interresting, and I take any possibility to use actual data (like from your car) to evaluate and when needed adjust the formulas.

What drives me to discuss degradation rates etc is that I started using lithium batteries about 2006/2007 and I did find already at that point that there was ”facts” that didnt seem correct.
Reading research I started adopting the new knowledge and I soon found my lithium ion cells to not die while my friends needed new at least once a year. I still have four packs (out of four) that performed wuite well last time I used them, like two year back. I bought them 2009. I have many lithium batteries except these, they are just one example.

When I went into the Tesla world I suddenly found the forums talking about things that did not seem right (with the things I learned 10 years earlier from research).

So, I went back to the research to see if something had changed and found that basically, it had not.
This means that the forums talking about 100% beeing very bad, being below 20% beeing bad and that 80% is the sweet spot for longevity etc. is not right. These not correct ”facts” which I call myths (might be more of urban legends as everybody ”knows it” but no one can find any facts supporting it, and from their perspective no supporting facts is needed as ”everybody knows” it is like that it works.

I decided to try to kill the myths. There is sufficient data to be sure that these myths are not correct.
I have absolutely no gain or interrest in trying to sell these facts. I have also no pride in changing view if we find new data that would change the world in a direction that shows me wrong. I would prefer to see more people engaging and reading the research so we could have a wider base of knowledge, possibly adjusting what I state in a way that we comes closer to the real world (I bet we are quite close alteady but…).