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

[AAKEE]

Interesting - I did a deeper dive of the paper, and found the following, though:

• They seemed to be surprised that rate of capacity loss was lower at 90/100% compared to 70/80% as well
• Cells stored at 100% had other failure modes besides capacity loss that would be worrisome - high internal resistance.

I would be careful of drawing any general conclusions based on this paper aside from the specific chemistry (note that they decline to note the manufacturer of the cells) since this behavior is not common.

More or less all reserch show signs if this, but the extent differs. How the tests have been performed can shift the results. Its possible that the actual setup in this research can be traced to the result that looks more spoony than most other research.

There is no reason to start use 90 or 100%.
1) This is a single research report of a single test series.

2) If held at high SOC the SEI(solid electrolyte inteface) tend to develope cracks which is not good in the long run.


If you like high power from your car you should not use high SOC as the internal resistance increase much more at high SOC.
This is really noticable at the lithium batteries I use in a hobby. High SOC for long time really kill the punch from the battery. This is also one of the reasons I keep the SOC low. I plan to keep my Performance for a while and the power limit is often set by the battery delivery capacity.
I will keep the punch ans soon my M3P is faster than most other M3P ’21

Low SOC keeps the increase of the internal resistance low. The lower the internal resistance the lower the heat loss when driving = more kWh out of a battery.

 

[Niroc]

My 2019 Model 3 Standard range plus has 14,000 miles. My battery went from 240 down to 218 mile capacity. I religiously followed the 20-80 % rule. No matter. The type of cells that Tesla put in my Model 3 battery can be summed up in one word; sucky.

The older model 3's claim they have only lost 6% of capacity when they hit a 100,000 miles. Yet at 14,000 miles, I lost 11% and dropping fast. I can think of another word; screwed.

Since losing range and will be dropping to a point where it will be difficult to take on trips, it makes me ponder another word; sell.

 

[AAKEE]

My 2019 Model 3 Standard range plus has 14,000 miles. My battery went from 240 down to 218 mile capacity. I religiously followed the 20-80 % rule. No matter. The type of cells that Tesla put in my Model 3 battery can be summed up in one word; sucky.

The older model 3's claim they have only lost 6% of capacity when they hit a 100,000 miles. Yet at 14,000 miles, I lost 11% and dropping fast. I can think of another word; screwed.

Since losing range and will be dropping to a point where it will be difficult to take on trips, it makes me ponder another word; sell.

The 20-80% rule isnt a rule that Tesla use.
It is not a rule that any expert or battery researcher would recommend.

Rules to keep the degradation low:
- Charge often. Small cycles degrade less.
- Use low SOC. Lower SOC degrade much less.
- Charge ‘just in time’= the charging is finished before the drive.

If the car stands for long time with 80%, there will be a noticable degradation from
time(calendar aging) even if the car is not used.

 

[conv90]

Keeping the SOC low as we say, below the about 57% step will basically cut the degradation in half. That should be quite safe to say.

The abolute main part of the people that see issues with higher degradation than they had expected use high SOC, leave the
car charged for time and also mostly live where the temperature have an negative effect.
There is a very few that use high SOC in warmer climate that see very low degradation.
Do we
Know anyone that use low SOC and have lost a lot?

As the research( a lot of research) show very consistent results, its very hard to see
that the same or very closely related cells should behave different mounted in a car.

you say: "
Do we
Know anyone that use low SOC and have lost a lot?"
Me . and you know that I cosider you a guru.
probably not "a lot".... but 73,8 kWh from theretical 82,1 it's a lot expecially if in 11 months and 22k km.
I asked to Tesla (a guy I Know).
He said I have a AVERAGE SOC of 39% . He said : " a very low average compared to the average user : 73%"
He have NOT said "too low average soc, so you have more average degradation". He simply said my car sat very low on SOC.
I'm conviced that my battery is a bad battery (under average).
This change my way to use it ? no. I have problem with range? no.
I'm happy of my car? YES.
I'm a bit disappionted (expecially if compared to other cars of my friends that don't take care of the battery like me and always charges to 80 or 90 or 100 night and day and let the car sleep at 90% and haves LESS degradation) ? YES.

 

[AAKEE]

you say: "
Do we
Know anyone that use low SOC and have lost a lot?"
Me . and you know that I cosider you a guru.
probably not "a lot".... but 73,8 kWh from theretical 82,1 it's a lot expecially if in 11 months and 22k km.
I asked to Tesla (a guy I Know).
He said I have a AVERAGE SOC of 39% . He said : " a very low average compared to the average user : 73%"
He have NOT said "too low average soc, so you have more average degradation". He simply said my car sat very low on SOC.
I'm conviced that my battery is a bad battery (under average).
This change my way to use it ? no. I have problem with range? no.
I'm happy of my car? YES.
I'm a bit disappionted (expecially if compared to other cars of my friends that don't take care of the battery like me and always charges to 80 or 90 or 100 night and day and let the car sleep at 90% and haves LESS degradation) ? YES.

Do you know at what capacity your battery started ? (Either range at full charge or Nominal full pack.)
It looks like a big degradation at short time but no car have shown 82kWh when new. Most common seem to be about 80 to 81 for M3P. Was it a M3P ‘21 you had?

Did you always use low SOC or did you have higher SOC initially?

There one guy from UK here with a 21 M3P that seem to have started at around 76kWh at least according to the BMS. No action seem to change the “low” value.

The cars that have low capacity despite low SOC since new is interresting.
We can be very sure that the real battery capacity can not be suffering from low SOC. We know from all research that low SOC is good for the battery. So there should not be any doubt about that the low SOC is not responsible for a high degradation.
We could theoretically see a case where the BMS loose track and estimate to low battery capacity but at least for me and a few other the opposite seems true( good track or maybe overestimating the capacity.

The first thing we need to establish is the initial capacity of your battery. Either via full charge range or Nominal full pack very early in the cars life.

The cars showing very little range loss despite high SOC is also interresting.
The research is very clear about how lithium ion in general and NCA in particular behave so the reason is interresting.

 

[conv90]

Do you know at what capacity your battery started ? (Either range at full charge or Nominal full pack.)
It looks like a big degradation at short time but no car have shown 82kWh when new. Most common seem to be about 80 to 81 for M3P. Was it a M3P ‘21 you had?

Did you always use low SOC or did you have higher SOC initially?

There one guy from UK here with a 21 M3P that seem to have started at around 76kWh at least according to the BMS. No action seem to change the “low” value.

The cars that have low capacity despite low SOC since new is interresting.
We can be very sure that the real battery capacity can not be suffering from low SOC. We know from all research that low SOC is good for the battery. So there should not be any doubt about that the low SOC is not responsible for a high degradation.
We could theoretically see a case where the BMS loose track and estimate to low battery capacity but at least for me and a few other the opposite seems true( good track or maybe overestimating the capacity.

The first thing we need to establish is the initial capacity of your battery. Either via full charge range or Nominal full pack very early in the cars life.

The cars showing very little range loss despite high SOC is also interresting.
The research is very clear about how lithium ion in general and NCA in particular behave so the reason is interresting.

Yes, we spoke about my car sometimes. 2021 March M3P .
Yes at the beginning I had 79,6 measured the same day of the delivery with SMT.
Yes i used to charge to 80 or 90 sometimes at the beginning but soon I started to charge less (when neded).
My car lost nothing up to August/september. Always 79,6 kWh
It started to loose (and have some rebound to UP ) starting in end of september when I started to follow your advices. (obviously there is no correlation with the fact i'm experiencing moderate to high degradation).

I have the theory of the "bad battery batch" or "lottery theory" , and another theory:
Probably the batteries are ruined and follow a "destiny/fate" at the really beginning of life.
I noticed when I installed SMT the same day of the delivery, that the car had a DC 57 kWh charge (when just born). probably from the factory.
I had the car in the 30% range when i picked Up.
So probaly the car has been charged 95-100% at the Tesla factory and during Ocean crossing and let it discharge to about 30% for 2 or 3 full months (produced in January and deliverd to me mid march).
This "killed" the battery in a way and marked the destiny of the battery.
Just a Theory.

 

[Niroc]

its ridiculous. They put a faulty cells (NAC) in those battery packs. They tell us that shouldn't charge above 80-90% and drop below 20%. The older cells had no constraints. In other words, we got screwed.

My car lost over 11% capacity with just have 14,000 miles on it. Tesla should get sued for it.

 

[Candleflame]

its ridiculous. They put a faulty cells (NAC) in those battery packs. They tell us that shouldn't charge above 80-90% and drop below 20%. The older cells had no constraints. In other words, we got screwed.

My car lost over 11% capacity with just have 14,000 miles on it. Tesla should get sued for it.

explain?

11% capacity loss at 14k miles is normal & average. Average is 469km on teslafi for that many miles - thats around 10% loss from 499km (520km)

 

[Candleflame]

Yes, we spoke about my car sometimes. 2021 March M3P .
Yes at the beginning I had 79,6 measured the same day of the delivery with SMT.
Yes i used to charge to 80 or 90 sometimes at the beginning but soon I started to charge less (when neded).
My car lost nothing up to August/september. Always 79,6 kWh
It started to loose (and have some rebound to UP ) starting in end of september when I started to follow your advices. (obviously there is no correlation with the fact i'm experiencing moderate to high degradation).

I have the theory of the "bad battery batch" or "lottery theory" , and another theory:
Probably the batteries are ruined and follow a "destiny/fate" at the really beginning of life.
I noticed when I installed SMT the same day of the delivery, that the car had a DC 57 kWh charge (when just born). probably from the factory.
I had the car in the 30% range when i picked Up.
So probaly the car has been charged 95-100% at the Tesla factory and during Ocean crossing and let it discharge to about 30% for 2 or 3 full months (produced in January and deliverd to me mid march).
This "killed" the battery in a way and marked the destiny of the battery.
Just a Theory.

charging you car to 95% and then letting it sit for 3 months discharging to 30% does not kill the battery in any way.

 

[conv90]

charging you car to 95% and then letting it sit for 3 months discharging to 30% does not kill the battery in any way.

It's only a Theory.
I'm just trying to explain to myself , why I have a degradation like this and trying to accomplish the theory of @AAKEE about some batteries that started since beginning under the 80,7 kWh mark*. Probably a battery with some cycles on it will not suffer from a discharge from 100% to 30% in 3 months.
BUT....Will You charge for the very first time your brand new car battery to 100% in DC just to let it drop to 30% in 2 or 3 months?
If I have to choose... I'd not try
* Im speaking of Pana 82,1 kWh batt

 

[Candleflame]

just bad luck. same how i have a crap battery.

you seem to misunderstand how much impact a 100 to 30% cycle has. Over the life of the battery thats hardly anything.
Even if you charge to 100% once a fortnight its just not really significant. Cyclestress from 100% to 0% is around the same as 2x 90% to 0%. But the return diminishes with shallower cycling depth and really most people who need the range probably do a 100% to 10-15% true SOC*. so it really doesnt matter as much as people think. The theory is also prooven by many fleet vehicles charging to 100% having not really more degradation than other cars.

The original Roadsters 100% SOC was like 93% true SOC (not really all that different to the Model 3, the Roadster was top limited and could go to 0% whereas the Model 3 is bottom limited and 0% is really 4.5%) to mainly limit cycling depth.
One of the Tesla engineers made a tesla blog post back when they had one on battery health and they figured that limiting SOC to max 90% to reduce cycling burden had a great effect on battery longevity, but reducing it further by i.e. another 10% to 80% didnt really have any meaningful gains for longevity.

 

[AAKEE]

you seem to misunderstand how much impact a 100 to 30% cycle has. Over the life of the battery thats hardly anything.

I think @conv90 refer to the calendar aging and not the cycle itself.

Leaving the battery at high SOC for long time is not good.
It think for now we can think that all hogh SOC causes high wear.

If didnt check the charge history of my car
but my guess is that Tesla should know better than to ship it overseas with 100% SOC.


We have a swedish M3P at a forum that passed 60.000km in just above 6-7 months. Initial capacity is not
known as he didnt really check for range at full charge etc. then.

The capacity is down about 5-6% from a 80kWh guesstimated starting capacity.
He use 90% to about 7-20% daily.
The car stands diring the middle of the day with 50-55%( at work, I think)

So from that he seem to loose about 1% for each 10.000km or about 30 full cycles (EFC).
The car stands with the about 7-20% over the night until the charging starts to be ready in time to the next trip. = calendar aging should be very small.

 

[Candleflame]

i dont think the car sitting at 90% for 3 weeks makes much of a difference.
and you showed your own research that degradation is pretty equal anyway (especially <20C) apart from the spoonshape around 80% SOC which is slightly worse (but not much).

 

[AAKEE]

i dont think the car sitting at 90% for 3 weeks makes much of a difference.
and you showed your own research that degradation is pretty equal anyway (especially <20C) apart from the spoonshape around 80% SOC which is slightly worse (but not much).

Yes. I agree.

The battery wouldnt break down because of this and also, I think Tesla have good knowledge about batteries so their shipping of cars around the world is most probably done in controlled manner went it comes to the battery etc.
( I did write my last post with a little time pressure so I guess I was not very clear about that).

There also are regulations about the maximum SOC for freight of lithium batteries. 30% is the max allowed SOC for this kind of batteries on Cargo aircrafts. I do not know the rules on sea and for clomplete vehicles on sea. But 100% SOC is most probably not allowed.

A one month worst SOC scenario at temps not above 20C would not cause a degradation for more than about 1 to 1.5% degradation and still a one month with 50% or so still casuses about the half degradation from above so the end result do not differ very much.

 

[conv90]

I think @conv90 refer to the calendar aging and not the cycle itself.

Leaving the battery at high SOC for long time is not good.
It think for now we can think that all hogh SOC causes high wear.

If didnt check the charge history of my car
but my guess is that Tesla should know better than to ship it overseas with 100% SOC.


We have a swedish M3P at a forum that passed 60.000km in just above 6-7 months. Initial capacity is not
known as he didnt really check for range at full charge etc. then.

The capacity is down about 5-6% from a 80kWh guesstimated starting capacity.
He use 90% to about 7-20% daily.
The car stands diring the middle of the day with 50-55%( at work, I think)

So from that he seem to loose about 1% for each 10.000km or about 30 full cycles (EFC).
The car stands with the about 7-20% over the night until the charging starts to be ready in time to the next trip. = calendar aging should be very small.

I was reffering on a battery (NEW, never charged , with 0 cycles on his life) charged to 100% and left discharged to 30% AS FIRST CYCLE of his life in 30 or 40 or 50 days.
I repeat my car never slept OVER 55% SOC. (only 3 or 4 times at 70 or 80% starting in march and before september). PAST september my car really never slept OVER 50-55% SOC.

 

[AAKEE]

I was reffering on a battery (NEW, never charged , with 0 cycles on his life) charged to 100% and left discharged to 30% AS FIRST CYCLE of his life in 30 or 40 or 50 days.
I repeat my car never slept OVER 55% SOC. (only 3 or 4 times at 70 or 80% starting in march and before september). PAST september my car really never slept OVER 50-55% SOC.

Yes.

I ”remember” your car/ issue but not in detail so repeating is good.

Its strange with your degradation, or NFP at least( as there might be cases where the NFP show higher degratatiol thn the ”real” one).

Would be very interresting to find the issue….

 

[Dave EV]

Would be very interresting to find the issue….

One way to verify the actual capacity of the pack would be to measure the amount of energy that is used to recharge the car from dead to 100%.

The EPA test, for example, measures this as part of it's testing to determine efficiency.

So the procedure would be:
1. Discharge battery to empty - verify module voltages using TeslaScan
2. Charge battery to 100% using utility grade energy meter - verify module voltages using TeslaScan

Verifying module voltages is important so you can see what battery balance looks like and you can also ensure that you actually hit a low SOC and 100% SOC.

This won't be as accurate as measuring DC in/out of the battery, but if you repeat it a few times you should be able to get a pretty good idea of how the battery is really doing and not just how the BMS thinks the battery is doing.

 

[DrChaos]

Nice (re) review of data I believe you've already covered in previous posts. I also think that you make your point quite clearly. You (we) are dealing with physical-chemical properties which, generally, behave in a quite predictable way. Having said that, I do realize that there are many contributing or complicating factors which can influence this data, but not the trends as you rightly say. Interpretation of data/misleading data is fundamental there . By training, I'm a biologist (vaccine developer) but the data you show is quite beautiful compared to the complex stuff one has to deal with when developing a manufacturing process and the hurdles of clinical development for a vaccine. We end up having to use DOE (design of experiment) to make sense of the data. Bravo keep going, I certainly will manage my M3 LR battery (M48 E5CD, 75kW) as you suggest. Results fit quite nicely right now

I'm going to be a new M3LR owner in a couple of months. I'm trying to figure out the optimal charging profile. I've been reading this thread for hours and am more confused than ever. I had hoped there would be a consensus recommendation. Otherwise the car suggests '90%' 'daily'. Is this a good idea. Should it be charged back to 90% after each trip, no matter how short, or to let it go down further?

But there is one issue that I think should be addressed: the difference in "percentage of capacity" used in published scientific experiments (which will be true, and presumably with a high and specified upper voltage limit) and the percentage displayed by the Tesla UI. I suspect 100% on Tesla is a bit less than 100% of science charge, but I'm not sure.

Is there any specific evidence on this, e.g. from cell voltage measurements on the car?

 

[AAKEE]

I'm going to be a new M3LR owner in a couple of months. I'm trying to figure out the optimal charging profile. I've been reading this thread for hours and am more confused than ever. I had hoped there would be a consensus recommendation. Otherwise the car suggests '90%' 'daily'. Is this a good idea. Should it be charged back to 90% after each trip, no matter how short, or to let it go down further?

First of all:
Your battery will be fine without any special handling from your side. Thats the way Tesla have managed it. No need to be a battery engineer.
Teslas advice in short: Always connect the charging when possible. Only charge above 90% for longer trips. Thats it.

But this will not be the same thing as minimizing the degradation to a minimum. Teslas advice is aiming to make the EV owning easy.

I have written a lot of posts about this. If you would like to keep the degradation to a minimum, you can do that. No need to, but if you for any reason would like to, its possible.

Lithium ion batteries degrade from calendar aging and cyclic aging. For most, the calendar aging is the dominating degradation early in the cars life. Cyclic aging comes from the cycles.

Low SOC wears less on the battery. Calendar aging is least at low SOC and highest at high SOC.
Cycles wear less at low SOC. Also, smaller cycles wear less than larger cycles.

- Charge often. This will keep your cycles small.
- Dont charge to a higher SOC than you need. If you really need 90% each day, use 90%, or charge one extra time each day and use lower SOC. If you only need 50%, charge to 50%.
- If possible, charge close in time before using the car. This reduce the time the car stands with high SOC.

I have written a lot of posts with detailed description of the fundamentals behind the advice above, taken from a lot of research about lithium ion batteries. Do a search on my posts if you need more info.

But there is one issue that I think should be addressed: the difference in "percentage of capacity" used in published scientific experiments (which will be true, and presumably with a high and specified upper voltage limit) and the percentage displayed by the Tesla UI. I suspect 100% on Tesla is a bit less than 100% of science charge, but I'm not sure.

Is there any specific evidence on this, e.g. from cell voltage measurements on the car?

100% on the screen is 100% real SOC. The bransch standard for this type of lithium ion batteries is 4.20V/ cell = 100% and thats what Tesla also use. When you read 100% the cells will have 4.20V/cell. If you try to measure it, or as most people use Scan My Tesla, you will se 4.19x or something, but this is because the car always is on, using a little power when yo can check the voltage.
The charging stops at 4.20V/cell. I have a lot of ”evidence” for this, but at this point I think we can skip this part. Just trust me and the other ones that say so.
0% on the screen is 4.5% ”true SOC” of the capacity that Tesla calculates, those 4.5% is the buffer below 0% on the screen.

This is a map of my degradation so far, 14 months and close to 35.000km. I follow my advice above, charge to 55% daily and my charge setting charges just in time so most nights my car sit at 20-35%SOC. I havent really lost any range but the other cars of the same type (model 3 performance 2021) have lost 5% in average. My car has lost least of all.

 

[AAKEE]

One way to verify the actual capacity of the pack would be to measure the amount of energy that is used to recharge the car from dead to 100%.

The EPA test, for example, measures this as part of it's testing to determine efficiency.

So the procedure would be:
1. Discharge battery to empty - verify module voltages using TeslaScan
2. Charge battery to 100% using utility grade energy meter - verify module voltages using TeslaScan

Verifying module voltages is important so you can see what battery balance looks like and you can also ensure that you actually hit a low SOC and 100% SOC.

This won't be as accurate as measuring DC in/out of the battery, but if you repeat it a few times you should be able to get a pretty good idea of how the battery is really doing and not just how the BMS thinks the battery is doing.

I think the energy meter in the car should be good enough also. Charge full and drive until the car almost stops and read the consumption details. The SMT cell voltages would help to extrapolate the last few drops of energy.

Charging and reading the consumption outside the car(or even inside) will not show the capacity of the battery. There are losses that will be included in the total.

Well, good thinking Dave! This is anyway one of the first things to consider to make sure that the BMS is right, or to learn its not.
I have a plan to do this with my car to see what the real capacity is. I have 80.5kWh NFP according to my BMS, and did charge full a few days back and did get 80.6 kWh remaining. I had a NFP of 80.6kWh when I first connected the SMT, after one day since I got the car.
I plan to do it to check my batt’s real capacity but it probalby will be a good reference to other doing the same thing.