Long Term Battery Costs, Fears, and Serviceability

[Geir]

Definitely do not worry. I live where temperatures in summer regularly exceeds +40C in the summer and I've parked my Model 3 with NMC batteries outside nearly every day for the past 6 years and there is no unexpected loss of range (still charges to ~287 miles). The key point is to keep the car charged. It will take care of the battery by running the A/C if necessary.

"The key point is to keep the car charged. It will take care of the battery by running the A/C if necessary"

Is'nt it better to keep the SOC low? Don't plug in when you have high SOC, let the car sit with a low SOC as much as possible.. The car won't cool the battery under 40 degrees. Or?

 

[AAKEE]

Is'nt it better to keep the SOC low?

Well, yes. I guess he means keep it connected?

Low SOC cutvthe calendar aging in half, which makes extra sense hot days.

The car won't cool the battery under 40 degrees. Or?

When deiving, these apply:
(My MSP but from memory it was the same values for my 2021 M3P)

Target for passive cooling of the batt is 40C.
(Most certainly means using ambient temp and the airflow from driving to cool the heat exchanger which cools the cooling fluid).
So, the target is 40C = will not cool when the cell temp is below 40C.

Target for active cooling is 45C, the active cooling (AC?) will not runt when cell temp is below 45C.

As I live too cold I will never see for myself if the car actually cools the battery when it is parked. But I suspect it does not.
My guess is that these values are for driving only.
Passive cooling won’t work when parked.
The battery will be close to the ambient when parked for a while, a little warmer when the sun heats.
But active cooling would be needed, draining the battery quite fast.

 

[Geir]

Well, yes. I guess he means keep it connected?

Low SOC cutvthe calendar aging in half, which makes extra sense hot days.


When deiving, these apply:
(My MSP but from memory it was the same values for my 2021 M3P)
View attachment 1052006

Target for passive cooling of the batt is 40C.
(Most certainly means using ambient temp and the airflow from driving to cool the heat exchanger which cools the cooling fluid).
So, the target is 40C = will not cool when the cell temp is below 40C.

Target for active cooling is 45C, the active cooling (AC?) will not runt when cell temp is below 45C.

As I live too cold I will never see for myself if the car actually cools the battery when it is parked. But I suspect it does not.
My guess is that these values are for driving only.
Passive cooling won’t work when parked.
The battery will be close to the ambient when parked for a while, a little warmer when the sun heats.
But active cooling would be needed, draining the battery quite fast.

 

[Geir]

Yes, but when you connect, the car will raise the battery SOC to 50% as minimum. Better to stay lower if you don’t need more for your nex trip. Espesially under warm conditions.

 

[FLRifleman]

Yes, but when you connect, the car will raise the battery SOC to 50% as minimum. Better to stay lower if you don’t need more for your nex trip. Espesially under warm conditions.

A 50% SOC is already on the very low end for battery longevity. I don't expect you'll gain much if anything by having a lower target. You're better off plugging it in whenever you can, so the system can actively manage the battery thermals on hot (90F or more) or cold days. Practically speaking, setting the maximum charge level to 80% is conservative enough for battery longevity.

 

[AAKEE]

A 50% SOC is already on the very low end for battery longevity.

Nope, its not.

This is how calendar aging is affected by SOC and temperature.

For NCA cells (Panasonic) stay at 55% displayed SOC or lower.
For NMC/NMC(A) (LG) stay at 60% displayed or lower.

50% is on the good side and causes about 50% of the calendar aging above 60%.

The calendar aging between 60-100% is avout the same.
In some cases, 80% is the worst SOC with higher being better than 80%.

I don't expect you'll gain much if anything by having a lower target. You're better off plugging it in whenever you can, so the system can actively manage the battery thermals on hot (90F or more) or cold days. Practically speaking, setting the maximum charge level to 80% is conservative enough for battery longevity.

Cold is good, and the modern Teslas do not heat the pack when parked. Nor my M3P 2021 or my MSP 2023 heats the battery when parked. (At low ambient with low cell temps the calendar aging is really low anyway so using high SOC doesnt increase the calendar aging much. (Still will be lower at 55% and below though)

Using 80% as the charge level and keeping it there will cause around the highest rate of calendar aging.

 

[LostVector]

"The key point is to keep the car charged. It will take care of the battery by running the A/C if necessary"

Is'nt it better to keep the SOC low? Don't plug in when you have high SOC, let the car sit with a low SOC as much as possible.. The car won't cool the battery under 40 degrees. Or?

Draining the battery to a low SoC makes sense if the car is going to sit for a while. For a car that is driven regularly, avoiding charging in order to drain to a low SoC when you could charge back up a bit does not make sense.

 

[AAKEE]

Draining the battery to a low SoC makes sense if the car is going to sit for a while. For a car that is driven regularly, avoiding charging in order to drain to a low SoC when you could charge back up a bit does not make sense.

[Sense] is subjective in this case.

If longevity and to reduce degradation is the goal, low SOC is preferable both for calendar- and cyclic aging.

You can not reduce degradation by charging past 55-60%.

As long as the energy from 55-60% or less is enough for daily driving (chemistry dependant) this charging to 55-60% will lead to the lowest degradation.

To minimize degradation:
-Do not charge to a higher SOC than needed.
-Charge often (reduces the need per above and reduces the Depth of discharge)
-Charge late, having the charge just finishing before the next drive so the car will stand less time at higher SOC.

Actual Model S cells calendar aging:
(Only calendar aging, as the text refer to other cells that was cycled)

80% was worse than 100% in this case, this is seen in several other tests as well.
But for our purpose we can think that it works like the chart I posted in post #146 above).
Another test on Panasonic NCANCR18650, not taken from a Tesla bit closely related)

Actual model 3 cells tested:
Only thre SOC- points but they match the other charts very good, pointing to the fact that model 3 cells also behave looe other Panasonic NCA cells.

Calendar aging is the process taking the absolute largest part of the battery for the 8-10 first years.

For cycles, low SOC is good as well.
Actual Model 3 cells cycled in 10% Depth of Discharge steps:
Teslas use a 4.5% buffer so the displayed SOC differs slightly in the low regime:
5-15% will be displayed as 0-10% on the display in the car.
15-25 will be shown as about 10-20%

All these charts show very low degradation, much lower than the calendar aging.
With the ”worst line” (5-15%) you loose 17% after 3000 FCE ( = 30.000 actual 10% cycles). This is equal to 1.2 million km or 750K miles, so driving ~20K km / 12K mi annually will give ~ 0.28% degradation.

This chart shows larger cycles but we can see that lower SOC cycles is better than in high SOC:

 

[Bouba]

Why does NMC fall off a cliff at high temperatures/high SOC compared to other battery technologies ?

 

[AAKEE]

Why does NMC fall off a cliff at high temperatures/high SOC compared to other battery technologies ?

I often use that picture to show both how similar the three chemistries behave and show a good average for Calendar aging for NCA. That picture is very good for these two things, but it is not the conclusion in all aspects.

The very high droop is not present in all NMC test, in many cases it is more like NCA so rather flat and also usually shows that 100% is not the worst SOC.

Even within a specific chemistry like NMC there’s differences between brands due to small differences in added substances etc.

Look at the chart in my post #136 for LG M50, NMC. Even that might not be the exact cell in Teslas LG Packs but it probably is as close as we get until anyone take a couple of cells from a 3/Y and test it.
They stopped testing 100%, 95%, 90%, and 85% around 30-40 weeks in the test, at that point the calendar aging has been similar (but we can se a slight thrend of diverting downwards).

I would think that no one leave the car at 100% for so long time. Looking at the shorter term, up to 30 weeks we see no big difference so some hours or overnight is not [that] bad. Compared to using 80% all other nights, it does’nt make a noticable difference.

A lot of good data but hard to see which line is which SOC. 85-90% seems worst, 75 and 95% next and 100% better than all those.

 

[Geir]

[Sense] is subjective in this case.

If longevity and to reduce degradation is the goal, low SOC is preferable both for calendar- and cyclic aging.

You can not reduce degradation by charging past 55-60%.

As long as the energy from 55-60% or less is enough for daily driving (chemistry dependant) this charging to 55-60% will lead to the lowest degradation.

To minimize degradation:
-Do not charge to a higher SOC than needed.
-Charge often (reduces the need per above and reduces the Depth of discharge)
-Charge late, having the charge just finishing before the next drive so the car will stand less time at higher SOC.

Actual Model S cells calendar aging:
(Only calendar aging, as the text refer to other cells that was cycled)
View attachment 1052150

80% was worse than 100% in this case, this is seen in several other tests as well.
But for our purpose we can think that it works like the chart I posted in post #146 above).
Another test on Panasonic NCANCR18650, not taken from a Tesla bit closely related)
View attachment 1052152


Actual model 3 cells tested:
Only thre SOC- points but they match the other charts very good, pointing to the fact that model 3 cells also behave looe other Panasonic NCA cells.
View attachment 1052153

Calendar aging is the process taking the absolute largest part of the battery for the 8-10 first years.

For cycles, low SOC is good as well.
Actual Model 3 cells cycled in 10% Depth of Discharge steps:
Teslas use a 4.5% buffer so the displayed SOC differs slightly in the low regime:
5-15% will be displayed as 0-10% on the display in the car.
15-25 will be shown as about 10-20%
View attachment 1052154
All these charts show very low degradation, much lower than the calendar aging.
With the ”worst line” (5-15%) you loose 17% after 3000 FCE ( = 30.000 actual 10% cycles). This is equal to 1.2 million km or 750K miles, so driving ~20K km / 12K mi annually will give ~ 0.28% degradation.

This chart shows larger cycles but we can see that lower SOC cycles is better than in high SOC:
View attachment 1052156

So the lower SOC, the better.
Sitting at 30%, do this have any negatives? Not plugged in.

 

[AAKEE]

So the lower SOC, the better.
Sitting at 30%, do this have any negatives? Not plugged in.

Except from short range, no,

I work far away from home and aim to arrive with low SOC. I still have a little to be able to cirmumnavigate any accident etc, as I go live into readinnes when I arrive at work (not good to be late).

So I aim to arrive with ~ 10-20% and I have the car parked not connected during the work week. Sometime I drive a little during the week so it can end up below 10%.
I charge up so the charge is ready shortly before I finish the shift and drive home.

At home I always have the charging set to be performed early in the morning begimning like 3-4 or 5 aclock depending on the energy needed.

I use 55% as the daily, even if 50% would be more than enough as 55% is the sweet spot between range and degradation.

My first Tesla, M3P 2021 had very low degradation after 2.5 years and 66K km.

My 23 MSP is a bit over one year from manufacturing / 11 months since delivery and still shows full range.
97.0kWh nomimal remaining according to the BMS - full pack when new is 99.4, but these packs usually tops slightly above 97kWh. My pack topped 98.4 nominal full pack and 99.0 nominal remaining at a full charge. Still had 97.9kWh nominal remaining around three weeks back.

Other Swedish Plaids seem to be at around 94-95 kWh after one year.
Basically my car has lost almost nothing during the first year which most often costs ~ 5% battery capacity.

Not many cars, and the MSP shows two different ranges depending on the wheel selection. Still full range on both.

I also use Teslalogger. I do not know why the data from my car is not present, same thing with the M3P.
I sid draw my still full range at 20K km plus into the chart:

It is not ”the battery lottery” that made me get two cars with low degradation.
It is the low SOC preserving the battery, and also a bit the cold climate.

Right now we have 28-30C (actually above freezing So we do not only store outself and the cars in the freezer).

 

[Geir]

Except from short range, no,

I work far away from home and aim to arrive with low SOC. I still have a little to be able to cirmumnavigate any accident etc, as I go live into readinnes when I arrive at work (not good to be late).

So I aim to arrive with ~ 10-20% and I have the car parked not connected during the work week. Sometime I drive a little during the week so it can end up below 10%.
I charge up so the charge is ready shortly before I finish the shift and drive home.

At home I always have the charging set to be performed early in the morning begimning like 3-4 or 5 aclock depending on the energy needed.

I use 55% as the daily, even if 50% would be more than enough as 55% is the sweet spot between range and degradation.

My first Tesla, M3P 2021 had very low degradation after 2.5 years and 66K km.

View attachment 1052191

My 23 MSP is a bit over one year from manufacturing / 11 months since delivery and still shows full range.
97.0kWh nomimal remaining according to the BMS - full pack when new is 99.4, but these packs usually tops slightly above 97kWh. My pack topped 98.4 nominal full pack and 99.0 nominal remaining at a full charge. Still had 97.9kWh nominal remaining around three weeks back.

Other Swedish Plaids seem to be at around 94-95 kWh after one year.
Basically my car has lost almost nothing during the first year which most often costs ~ 5% battery capacity.

Not many cars, and the MSP shows two different ranges depending on the wheel selection. Still full range on both.
View attachment 1052200

I also use Teslalogger. I do not know why the data from my car is not present, same thing with the M3P.
I sid draw my still full range at 20K km plus into the chart:
View attachment 1052206

It is not ”the battery lottery” that made me get two cars with low degradation.
It is the low SOC preserving the battery, and also a bit the cold climate.

Right now we have 28-30C (actually above freezing So we do not only store outself and the cars in the freezer).

What is then the + to have the car plugged in when you don’t need the higher state of charge? When not charging, which adventages to have it plugged?