Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[Rocky_H]

There is almost a decade of evidence to back me up.

The far more than a decade of evidence of studies on lithium ion batteries says the opposite of what you are saying.

people would be bricking their batteries all the time.

The very fact that you use this kind of term "bricking" shows that you are viewing degradation as an ON/OFF kind of thing, which is not how degradation works. It is a gradual little-by-little thing, where small bits of damage can accumulate. And the extensive data on lithium ion batteries shows that the least amounts of degradation are when it is near a middle state of charge, and then there is increasingly a little more, the farther away from the middle you get in your usage--both higher or lower. It is not perfectly fine with no degradation at all through some very broad range, and then suddently, over some threshold degradation punches it in the face and severely damages it. It doesn't work that way.

There absolutely is a buffer at the top and the bottom.

Buffer at the bottom: yes, of course. That has been seen and measured pretty extensively. Top: no, usually not. Many other EV makers have done that, because of not giving very fine control of a charging limit. They try to simplify it with "full" that people get to use a lot, but they need that to not be truly 100%, so people aren't frequently causing a lot of damage. Tesla handles this in the other way, where they have 90%-100% marked off for "Trips" and recommend people to not use that constantly. So they do not need to have a hidden upper end buffer and they do not.

This can be seen evidentially by charging slowing down to extremely slow levels, down to 2 and 1 amp when charging to what Tesla shows as full on the state of charge meter. It would not need to slow down that much at the very end if there was an unused upper buffer available. This was seen in some of the batteries that Tesla did offer for some time with software-locked upper capacity, like the "60" and "70" batteries, which were really 75 ones. They charged significantly fast up to their designated fake 100% points and then stopped suddenly because of the unused upper portion.

Hey Rocky_H, if you are just going to disagree with everything, why don't you back it up with some actual info?

If you would be patient while I am composing my reply instead of argumentative, you would get it.
Here are some examples:
This study was showing much greater energy retention using a cycling range within 40%-60% state of charge level than the greater depth of discharge amounts, going higher and lower.

ShieldSquare Captcha

iopscience.iop.org

Here is another study on degradation. In the section about lithium plating, it mentions these things as exacerbating factors:
"Low temperatures, high SoC, high (charge) current, high cell voltage and insufficient NE mass or electrochemically active surface area can all cause lithium plating."

Lithium ion battery degradation: what you need to know

The expansion of lithium-ion batteries from consumer electronics to larger-scale transport and energy storage applications has made understanding the many mechanisms responsible for battery degradation increasingly important. The literature in this complex topic has grown considerably; this...

pubs.rsc.org

And this study is showing retained capacity based on where in the state of charge cycles are done. Running cycles of half of the battery capacity, but some at 50% to 100% versus centered around the midpoint by doing 25% to 75% showed that there was less degradation by using that middle state of charge than by doing it at the higher state of charge.

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

And again, this is not instantly "bricking" batteries, as you mentioned, but is causing some gradual loss of possible capacity over time, based on accumulated small bits of damage based on approximately what state of charge is used frequently.

 

[Earl]

There is zero proof of what you are saying. There absolutely is a buffer at the top and the bottom.

There actually is proof of what I'm saying but I'll leave it to others to dig it up (hint: Jeff Dahn, BatteryMD, owner manual, . . . ). My info comes from talking directly with Tesla and other battery experts. It's also what the car tells you both in the manual and cautions that pop up when you get to a low or high SoC.
I have seen a bricked Tesla Roadster where the owner left it unplugged for a while after returning with it at low SoC. Given the loud litigious threats from his lawyer afterward, it was apparent that there may have been more involved than just lazy stupidity.
As far as buffer on top, bottom, or not at all, this is irrelevant. If only affects what the battery gauge says not what the battery SoC actually is. If the real 10% at the top and bottom are hidden (ie. in the buffer), then there won't be much of a problem leaving the car when it says zero or full. If not, then you'll do more damage to your car.
My guess would be that, if there is a buffer, it is probably set so that your car battery will last for the warranty period. Therefore, if you keep the battery between with the gauge reporting between 10% and 90% during all long time periods, it will be in even better shape after its warranty expires.
There will be little harm in fully charging before a long leg of a trip or letting it dip low on your way to charge it. Just drive away soon after it reaches 100% and charge soon after it reaches zero and you'll be fine. Doing this for over 12 years with a Tesla Roadster has worked just fine for me.
If I'm wrong, and you follow my guidance you'll have suffered the inconvenience of having to plug it in a bit more often. If I'm right and you go against my guidance, your car's value to you or others may be worth less.
Its kind of like if we are looking for a place to camp and come to a cleared area by a railroad track. I say "I don't recommend camping on the tracks since a train may come". Someone else on the internet may say "its ok, there aren't any trains coming tonight". You could heed my suggestion and pitch your tent away from the tracks and sleep fine. Or you can pitch your tent on the tracks. Following the other advice: you may be ok . . . .
Your choice, I don't care. My advice is free and others are free to listen or not.

 

[AAKEE]

This is wrong. There is no threshold.
Its a continuum from minimum damage at about 50% SoC with more damage occurring as the SoC moves beyond 50% either high or low.
Between about 10% and 90%, the 'badness' isn't too bad but there is a 'knee' in the curve below 10% and above 90% where the damage becomes more pronounced. At or beyond the cutoff point, you're really hurting your battery.

There is zero proof of what you are saying. There absolutely is a buffer at the top and the bottom. If there was not, people would be bricking their batteries all the time. The only thing that causes wear on the batteries is the actual usage of it. How you charge it, especially on L1 & L2 charging equipment, has no effect at all. Short of leaving your battery a 0% for months, there is nothing you can actively do to damage the battery. There is almost a decade of evidence to back me up.

Earl: suggest you read my post, earlier in this thread: Degradation from SOC/time and themp
Short version: for storage reasons( = when not driving or charging your car), the lower SOC the lower aging(= lower degradation) of the battery.
Theres numneorus tests/open research on this, all claiming the same result: If you like to minimize the degradation, keep SOC as low as practicable possible, specially during the hot season.

jelloslug: Top buffer would be seen as 100% charge not reaching 4.200V/cell. There in no top buffer in most of the cars, early or very early teslas did only charge to 4.15V I think, but now most charge to 4.20V. Some european LR AWD have a smaller LG battery(74.5kWh) , and to cope with this Tesla did set the 100% charging level of the cars that do get the ”old” 2170 to a lower value, somewhere around 4.15V to also only reach the 74.5kWh capacity. The reason is not top buffer for longelivety but to make the LR’s comparable between LG and Panna batteries.

There is a buffer at the bottom, yes.

 

[jelloslug]

There actually is proof of what I'm saying but I'll leave it to others to dig it up (hint: Jeff Dahn, BatteryMD, owner manual, . . . ). My info comes from talking directly with Tesla and other battery experts. It's also what the car tells you both in the manual and cautions that pop up when you get to a low or high SoC.
I have seen a bricked Tesla Roadster where the owner left it unplugged for a while after returning with it at low SoC. Given the loud litigious threats from his lawyer afterward, it was apparent that there may have been more involved than just lazy stupidity.
As far as buffer on top, bottom, or not at all, this is irrelevant. If only affects what the battery gauge says not what the battery SoC actually is. If the real 10% at the top and bottom are hidden (ie. in the buffer), then there won't be much of a problem leaving the car when it says zero or full. If not, then you'll do more damage to your car.
My guess would be that, if there is a buffer, it is probably set so that your car battery will last for the warranty period. Therefore, if you keep the battery between with the gauge reporting between 10% and 90% during all long time periods, it will be in even better shape after its warranty expires.
There will be little harm in fully charging before a long leg of a trip or letting it dip low on your way to charge it. Just drive away soon after it reaches 100% and charge soon after it reaches zero and you'll be fine. Doing this for over 12 years with a Tesla Roadster has worked just fine for me.
If I'm wrong, and you follow my guidance you'll have suffered the inconvenience of having to plug it in a bit more often. If I'm right and you go against my guidance, your car's value to you or others may be worth less.
Its kind of like if we are looking for a place to camp and come to a cleared area by a railroad track. I say "I don't recommend camping on the tracks since a train may come". Someone else on the internet may say "its ok, there aren't any trains coming tonight". You could heed my suggestion and pitch your tent away from the tracks and sleep fine. Or you can pitch your tent on the tracks. Following the other advice: you may be ok . . . .
Your choice, I don't care. My advice is free and others are free to listen or not.

So all you are going to say is 1) I'm not going to offer proof of what I'm saying and 2) What I said about leaving your car at 0% is right.

 

[jelloslug]

The far more than a decade of evidence of studies on lithium ion batteries says the opposite of what you are saying.

The very fact that you use this kind of term "bricking" shows that you are viewing degradation as an ON/OFF kind of thing, which is not how degradation works. It is a gradual little-by-little thing, where small bits of damage can accumulate. And the extensive data on lithium ion batteries shows that the least amounts of degradation are when it is near a middle state of charge, and then there is increasingly a little more, the farther away from the middle you get in your usage--both higher or lower. It is not perfectly fine with no degradation at all through some very broad range, and then suddently, over some threshold degradation punches it in the face and severely damages it. It doesn't work that way.

Buffer at the bottom: yes, of course. That has been seen and measured pretty extensively. Top: no, usually not. Many other EV makers have done that, because of not giving very fine control of a charging limit. They try to simplify it with "full" that people get to use a lot, but they need that to not be truly 100%, so people aren't frequently causing a lot of damage. Tesla handles this in the other way, where they have 90%-100% marked off for "Trips" and recommend people to not use that constantly. So they do not need to have a hidden upper end buffer and they do not.

This can be seen evidentially by charging slowing down to extremely slow levels, down to 2 and 1 amp when charging to what Tesla shows as full on the state of charge meter. It would not need to slow down that much at the very end if there was an unused upper buffer available. This was seen in some of the batteries that Tesla did offer for some time with software-locked upper capacity, like the "60" and "70" batteries, which were really 75 ones. They charged significantly fast up to their designated fake 100% points and then stopped suddenly because of the unused upper portion.


If you would be patient while I am composing my reply instead of argumentative, you would get it.
Here are some examples:
This study was showing much greater energy retention using a cycling range within 40%-60% state of charge level than the greater depth of discharge amounts, going higher and lower.

ShieldSquare Captcha

iopscience.iop.org

Here is another study on degradation. In the section about lithium plating, it mentions these things as exacerbating factors:
"Low temperatures, high SoC, high (charge) current, high cell voltage and insufficient NE mass or electrochemically active surface area can all cause lithium plating."

Lithium ion battery degradation: what you need to know

The expansion of lithium-ion batteries from consumer electronics to larger-scale transport and energy storage applications has made understanding the many mechanisms responsible for battery degradation increasingly important. The literature in this complex topic has grown considerably; this...

pubs.rsc.org

And this study is showing retained capacity based on where in the state of charge cycles are done. Running cycles of half of the battery capacity, but some at 50% to 100% versus centered around the midpoint by doing 25% to 75% showed that there was less degradation by using that middle state of charge than by doing it at the higher state of charge.

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

And again, this is not instantly "bricking" batteries, as you mentioned, but is causing some gradual loss of possible capacity over time, based on accumulated small bits of damage based on approximately what state of charge is used frequently.

So tons of theoretical studies with extrapolated results and very little real world evidence. When you actually look at what people are seeing in degradation after 100k or more miles, these studies in their laboratory environments don't follow the actual evidence. Posting lab tests as the final word, especially without taking any consideration on actual battery chemical formulations, is just guessing at best. Trying to increase your battery life by following those rules is just a waste of time.

 

[AAKEE]

You cannot hurt your battery when the indicator on the screen says that your SOC is low. The threshold where battery damage can occur is far below where the car will turn off to protect itself.

Depends what you mean with ”hur the battery” ?

Every single action ”hurt” the battery more or less. Keeping the battery at low temperature and low SOC hurt the least, you could make it last 30 years, if kept at low SOC and low temp...and not used.

I know from some 15 years experience with other applications with lithium batterys that low SOC together with high power demands hurt those lithium batterys bad. Continuing the fast discharge below 20% SOC( would be around some 15% if we inlcudew the buffer Tesla use). Not exactly the same battery type, and I havent seen any battery tests of NCA li ions showing the same thing, but on the other hand these tests always stay at moderate loads(2-3C). We know that the higher the current/ C-load the shorter the life. Full power on a M3P is around 5C, and thats about double the load compared to the tests I seen.

Until I can read a quality research report showing me the opposite I will use power below 20% SOC (on the screen) carefully. I know it wont break on the day, but I will use my lithium battery experience + what I read in research/tests to keep my battery with as low degradation as possible, but still within reason to be able to use my car as casual as possible. I wont leave it with 15% and then need to charge if I find out I need to go to the store for some milk. But I need less charge at summer so I will use a lower charge level at summer/warmer days than at winter.

 

[AlanSubie4Life]

So tons of theoretical studies with extrapolated results and very little real world evidence. When you actually look at what people are seeing in degradation after 100k or more miles, these studies in their laboratory environments don't follow the actual evidence. Posting lab tests as the final word, especially without taking any consideration on actual battery chemical formulations, is just guessing at best. Trying to increase your battery life by following those rules is just a waste of time.

I mostly agree with your final conclusion - it appears that capacity loss is driven mostly by use (total cycle count) and battery age and probably environmental factors, with a good dose of randomness (manufacture date?) thrown in. But suggesting that somehow extremes of SoC simply don't matter seems a bit too binary/ black & white. Tesla actively tries to stop you from charging above 90% routinely, so there must be something to this...

Anyway, I think that mostly following reasonable and normal charging practices recommended by Tesla, and not worrying about briefly pulling down to 0-5% SoC or up to 100% SoC when you need to is just fine. I doubt it will appreciably impact capacity loss over time, if it's not something you're doing all the time.

But, note I am not saying these extremes don't impact capacity loss.

Tesla's system and following their recommendations results in generally shallow cycles, from a charge limit of 50%-90% SoC. So I suspect there's something to be said for doing that (obviously there are usability compromises that must be taken into account by Tesla as well - my main point here is the shallow cycles). It just may not make a huge difference overall. My impression is that capacity loss is dominated by random chance, but we have essentially zero public data (just crude plots from Excel & TeslaFi at the fleet level combining many types of vehicles with similar batteries, which is not particularly elucidating) on all the factors - only Tesla has this information - they likely know exactly which of the many variables matters most.

I'm curious how people who track their cars frequently are doing on battery health. That's something that doesn't apply to most users but would be an interesting data point (if we could actually get enough data points, which is doubtful - again, only Tesla has this information).

 

[AAKEE]

Therefore, if you keep the battery between with the gauge reporting between 10% and 90% during all long time periods, it will be in even better shape after its warranty expires.

Of course: Tesla is not lying. If you follow the simple rules, you battery will be fine( = it will still be less than 30% degradation the day the warranty expires). Thats fine For Tesla, and that maybe fine for you.

But if you like to keep the degradation small, to keep the range you caould use another approach to keep the degradation to a minimum.
It is probably not worth going all in and always leave the car with 15% SOC or less, because the life gets to cumbersome to live if you always have to plan ahead.

The battery degrades from different reasons. Degradation from time increases with SOC and temp.
If you would keep the car at 15% SOC when resting instead of 90% the degradation from time will be half. Check this picture, the essence is the same in many other tests. The data fit nice between the tests.

We probably wouldnt like to have it at 10 or 15%, so if we adopt the theory of this in a more practical manner, we use as low SOC as it is reasonable, for me it was to charge to 70% during the coldest days and 60% in the current ambient temps( about 0C average) and during the hot period I porobably will charge to 50%. I could go lower on all three, but then I might have to wait for charge to go on a unplanned trip on the evening after work.

High currents shortens the battery life. Only SuC when needed. For me, when traveling of course, but not daily.

Shallow cycles is causing less degradation than big cycles, and the same DOD but in a lower SOC intervall causes less degradation.
Its better to charge one extra time and go from 60 to 40% two times, than 60 to 20% one time. Its even better to go lower, if you anyway will charge, you could do two 40 to 20% cycles. Compare the 10-20% with the 60-70% down below.

 

[Dave EV]

The far more than a decade of evidence of studies on lithium ion batteries says the opposite of what you are saying.

The very fact that you use this kind of term "bricking" shows that you are viewing degradation as an ON/OFF kind of thing, which is not how degradation works. It is a gradual little-by-little thing, where small bits of damage can accumulate. And the extensive data on lithium ion batteries shows that the least amounts of degradation are when it is near a middle state of charge, and then there is increasingly a little more, the farther away from the middle you get in your usage--both higher or lower. It is not perfectly fine with no degradation at all through some very broad range, and then suddently, over some threshold degradation punches it in the face and severely damages it. It doesn't work that way.

Buffer at the bottom: yes, of course. That has been seen and measured pretty extensively. Top: no, usually not. Many other EV makers have done that, because of not giving very fine control of a charging limit. They try to simplify it with "full" that people get to use a lot, but they need that to not be truly 100%, so people aren't frequently causing a lot of damage. Tesla handles this in the other way, where they have 90%-100% marked off for "Trips" and recommend people to not use that constantly. So they do not need to have a hidden upper end buffer and they do not.

This can be seen evidentially by charging slowing down to extremely slow levels, down to 2 and 1 amp when charging to what Tesla shows as full on the state of charge meter. It would not need to slow down that much at the very end if there was an unused upper buffer available. This was seen in some of the batteries that Tesla did offer for some time with software-locked upper capacity, like the "60" and "70" batteries, which were really 75 ones. They charged significantly fast up to their designated fake 100% points and then stopped suddenly because of the unused upper portion.


If you would be patient while I am composing my reply instead of argumentative, you would get it.
Here are some examples:
This study was showing much greater energy retention using a cycling range within 40%-60% state of charge level than the greater depth of discharge amounts, going higher and lower.

ShieldSquare Captcha

iopscience.iop.org

Here is another study on degradation. In the section about lithium plating, it mentions these things as exacerbating factors:
"Low temperatures, high SoC, high (charge) current, high cell voltage and insufficient NE mass or electrochemically active surface area can all cause lithium plating."

Lithium ion battery degradation: what you need to know

The expansion of lithium-ion batteries from consumer electronics to larger-scale transport and energy storage applications has made understanding the many mechanisms responsible for battery degradation increasingly important. The literature in this complex topic has grown considerably; this...

pubs.rsc.org

And this study is showing retained capacity based on where in the state of charge cycles are done. Running cycles of half of the battery capacity, but some at 50% to 100% versus centered around the midpoint by doing 25% to 75% showed that there was less degradation by using that middle state of charge than by doing it at the higher state of charge.

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

And again, this is not instantly "bricking" batteries, as you mentioned, but is causing some gradual loss of possible capacity over time, based on accumulated small bits of damage based on approximately what state of charge is used frequently.

None of the studies that you link to refute that jelloslug was saying which is:

Lower states of charge (basically above 3.0V which is where Tesla will let you discharge to and is considered 0%) aren't any more harmful than say 50% SoC. jelloslug went a bit further in claiming not to worry about driving hard at low states of charge, again saying that the BMS will protect the cells, and for the most part, I think he's correct here as well, again because the BMS won't let you pull the same amount of current at low states of charge as it will at higher states of charge.

I might argue that you might not want to go below 10% SoC for maximum life, mainly because the voltage drops rapidly around there from ~3.5-3.0V which usually also indicates that other physical changes might be occurring rapidly there, too which might contribute to capacity loss, but I don't have the data to back it up.

The studies were interesting, but didn't do anything to dispute the claim that say cycling the battery from 20-40% will result in less capacity less than cycling the battery from 40-60%, for example. In real life, I would fully expect a battery that is cycled between 20-40% to last longer than a battery that is cycled between 40-60%.

Most guidelines that suggest 40-50% SoC for storage (sometimes higher!) only really do so because they are concerned about any parasitic loads that may be attached to the pack, which could fully discharge the pack - not because they are looking for the absolute maximum battery life.

Edit: And of course, as I was posting this AAKEE goes and posts a lot of great data showing how low SOC (all the way to 0%) is good for long term storage. Thanks!

 

[Candleflame]

Hey Rocky_H, if you are just going to disagree with everything, why don't you back it up with some actual info?

i have posted a paper here which suggested that cycling the battery at very low SOC is more healthy than in the higher midrange i.e .70%.

 

[AlanSubie4Life]

Of course: Tesla is not lying. If you follow the simple rules, you battery will be fine( = it will still be less than 30% degradation the day the warranty expires). Thats fine For Tesla, and that maybe fine for you.

But if you like to keep the degradation small, to keep the range you caould use another approach to keep the degradation to a minimum.
It is probably not worth going all in and always leave the car with 15% SOC or less, because the life gets to cumbersome to live if you always have to plan ahead.

The battery degrades from different reasons. Degradation from time increases with SOC and temp.
If you would keep the car at 15% SOC when resting instead of 90% the degradation from time will be half. Check this picture, the essence is the same in many other tests. The data fit nice between the tests.

We probably wouldnt like to have it at 10 or 15%, so if we adopt the theory of this in a more practical manner, we use as low SOC as it is reasonable, for me it was to charge to 70% during the coldest days and 60% in the current ambient temps( about 0C average) and during the hot period I porobably will charge to 50%. I could go lower on all three, but then I might have to wait for charge to go on a unplanned trip on the evening after work.
View attachment 655487

High currents shortens the battery life. Only SuC when needed. For me, when traveling of course, but not daily.

View attachment 655493

Shallow cycles is causing less degradation than big cycles, and the same DOD but in a lower SOC intervall causes less degradation.
Its better to charge one extra time and go from 60 to 40% two times, than 60 to 20% one time. Its even better to go lower, if you anyway will charge, you could do two 40 to 20% cycles. Compare the 10-20% with the 60-70% down below.
View attachment 655494

Someone should really do all this testing with a bunch of brand-new 2170 cells. Only $15k cost to get the study started with brand-new cells. Just tell Tesla that someone stole your battery, and have them drop a new one in. Who will be the first?

 

[AAKEE]

Someone should really do all this testing with a bunch of brand new 2170 cells. Only $15k cost to get the study started with brand new cells. Just tell Tesla that someone stole your battery, and have them drop a new one in. Who will be the first?

Its possible to find the panasonic 2170 used in the M3 if one like to do tests. But, both the old model S ncr18650 and hte 2170 is NCA, so its the same base chemistry whichs sets some of the basics. There might be small differences but hte goods and the bads with NCA should still be valid so if you read the tests and reserach the basics most probalbe still is valid if the tests was performed on a 18650 NCA battery. Theres a lot of good tests/research and as I did write before, one should read a handfull of tests and compare them, as not all researchers draw the correct conclusions.

If you use the data from some ten or so of the reports, you could put up a formula that will predict the battery degradation(in some of the tests, they already have made a prediction formula and then use the test to see if the prediction is correct. These predictions is found very precise in most of the tests). Im quite positive that we could make an easy formula that say that you will have 5, 10 or 15% degradation after one year or two. I also guess the outliers would be detected, both the one with very low and very high degradation. The cases where the BMS is off track and have a not correct number will not be in line with the calculation but the calculation would then point to this as an probable issue.

 

[jelloslug]

i have posted a paper here which suggested that cycling the battery at very low SOC is more healthy than in the higher midrange i.e .70%.

How many times? How old were the batteries? What chemistry? What temperature? What charging rate?

 

[AlanSubie4Life]

But, both the old model S ncr18650 and hte 2170 is NCA, so its the same base chemistry whichs sets some of the basics. There might be small differences but hte goods and the bads with NCA should still be valid so if you read the tests and reserach the basics most probalbe still is valid if the tests was performed on a 18650 NCA battery

That's the question, of course. Anecdotally there appear to be differences, and we have no idea whether there are or how much, or why. I don't think there's any reason with the same fundamental chemistry to necessarily expect identical degradation characteristics. The super fine details probably matter. Certainly I would expect the trends and general behavior to be the same, but drawing conclusions about the specific magnitudes and rates of capacity loss is harder.

 

[Candleflame]

How many times? How old were the batteries? What chemistry? What temperature? What charging rate?

1 to 4c. I have posted this paper a few times on tmc, have a look at my old posts... And 4c at low soc was better than 1c at 70%

 

[vapor trail]

Most reports I have read suggest if you follow the 20-80 charging cycle rule, you should see 5% degradation in the 1st 50k miles and another 5% over the next 100k miles for a total of 10% degradation after 150k miles.

Below is a link to an August 2018 article from Clean Technica that I have found to be fairly accurate and the info in it applies across all EV's.

I currently have 4% degradation after 66,000 km with 305 km range at 80% and having 79km remaining at 20%
That gives me 226km range on Flat land for my MX in summer.

Interpolating the table in the article I did the math and at 6,000 of the 80-20 cycles x 226km per charge I should see 1,3million km before my MX battery has degraded to 85 % of the 414km OEM. Have a read, do the math. Oh and I supercharge All the time as I have Free SC for life.

The Secret Life Of An EV Battery - CleanTechnica

I've heard detractors gleefully declaring that anyone buying an EV will find that their EV battery will be defunct within a couple of years.

cleantechnica.com

Hope this helps you out.

Cheers, Hugh-SG

That's a very informative read in link you provided regarding EV batteries and management. Thanks!

 

[AAKEE]

That's a very informative read in link you provided regarding EV batteries and management. Thanks!

It is, but it also contains some real errors, and also some parts thats not valid to Teslas. The errors are so many and so big in some cases that wouldnt recommend friends to read it to learn about batterys.

The part about the virtual battery 0-100% and the top buffer isnt used like that On a Tesla.

The article seems to state that the BMS limits the current to some 0.25C For longelivety which of course isnt true. 400kW battery power on a M3 battery is some 5C when the battery is fully charged and between more than 6C at lower SOCs.
0.25C would limit the maximum power to about 20kW.
The BMS can limit the max charge, regen and discharge current for reasons like low battery temp etc, and this is done for battery life reasons. But it doesnt hinder me from flooring the car and emtying the batteri at a 5C rate, which in the long run will shorten the battery life.

Tesla do not limit the charge voltage to 4.15V (they did, initially on the first Tesla Roadster) but they do not limit it anymore except for some battery size limiting that is done to make different battery brands use the same capacity despite they actually differ in capacity.

The text above isnt really true. Tesla use the full capacity up to 100% state of charge(4.2V), and all of the capacity is used. Fore the battery meter there about 5% left as a bottom buffer. Unless from that buffer, the maximum capacity of the battery is used and there really is no other batterys that provide more capacity when related to weight or volyme mounted on the car( theres exceptions like using LFP batteries on some Standard range cars but it has been rarely used by Tesla so far. Tesla have been using the batteries with the highest energy density.


There is a misscalculation about 50 liters of fuel, 50liter gas contains 450kwh, not 600.
P100D, 100kwh battery weighs 625kg, but the article claims that a 50kwh battery weighs haft a ton, thats quite far away from the truth.
These two fault multiple the error in the article. 50L of fuel doesnt equal 6000kg of lithium batterys, its equal to 2800kg Tesla packs.

 

[opetro]

I think I have a battery degradation problem. Please help me with the math. I have a 2018 M3 LR AWD (I guess 75 KWH) with 23k miles.
I recently did a test, here are the numbers:
I started with 100% charge and it showed 285 Miles range (I understand this range does not mean too much as it depends on driving, temperature, etc)
I drove until I had 5% left with an average of 269 Wh/mi, used 56KWH in total and managed to go 208 miles (photo attached).

My calculation of degradation:
Estimated total capacity of the battery: 56KWH + 5% = 57KWH
Degradation: 57KWH/75KWH= 76% so I lost 24%

I made an appointment with Tesla to discuss this but does my estimate seem correct?
One thing I am not sure about: I did this test when it was rather cold with temperatures in the 40-50s. Does this affect the KWH of your battery or only your consumption Wh/mi?
Thanks!!!

 

[AlanSubie4Life]

with 100% charge and it showed 285 Miles

You are fine. Your battery has ~69.8kWh. Call it 70kWh. You started around 76kWh to 77.8kWh. You can use the methods posted elsewhere here to calculate it.

this range does not mean too much as it depends on driving, temperature, etc)

Means a lot as it does not depend much on these things, actually. This is the key number indicating your estimated capacity, and it is a generally good estimate. It’s not dependent on driving.

drove until I had 5% left with an average of 269 Wh/mi, used 56KWH in total and managed to go 208 miles (photo attached).

This method only works if you drive continuously without stopping (it does not count use while you are in Park which is substantial). If you do that on your car from 100% to 5% you will get 69.8kWh*0.955*0.95*.99 = 62.7kWh.

All is well. I would cancel your appointment unless you find something inconsistent or weird not matching the above; you are wasting your time.

It’s entirely possible that cold temperatures could alter the results somewhat, yes. I don’t know exactly how much. But the above are good guidelines for more moderate temps. For the most part these results are not going to change much though. Primarily temperature affects your Wh/mi (due to accessory use and to a lesser extent denser atmosphere, etc.) not total capacity.

 

[Rocky_H]

I started with 100% charge [...] I drove until I had 5% left

You did this with many short trips over several days, didn't you? You can't do it that way. Because...

This method only works if you drive continuously without stopping (it does not count use while you are in Park which is substantial).

We see on this forum new owners making that mistake very frequently. You could look at the mistake as one of two assumptions. It's either people thinking the car has zero losses while it's parked, or assuming that the meter in the car continuously tracks it and will show that cumulative energy consumption next time you start driving (which it doesn't).