Is battery calibration pointless?!

[Kimmi]

Three year old M3 LR with 29K miles. What was 353 new is 318. I can live with 10% loss in three years. Battery still shows 74kWh full capacity. Happy dance!

 

[CWhite]

OK, here we go, I have a 2020 Model S LR+, had it 3 1/2 years with about 20k miles. Had it below 10% a few times and charged to 100% once when I first got it. Original has 402 miles range indicated, 6 months later changed to winter tires on Slipstreams and the range dropped to 380, never came back up in the spring changing back to the Tempists. Indicating about 375 now(interpreted from 188 @ 50%). Thinking of trying the ‘rebalancing’ I have heard so much about, doubt it will make much difference but what the heck. Other than confirming that you also think it will not make much difference is there any issue with this plan:

1) run battery down to 5% and let sit a few hours(less than 5%???)

2) charge at 11.5kw until 100% and let sit for three hours with it still plugged in, no accessing the car physically or via the app.

3) drive car to get to 90% or less so it does not sit for a long period at high SOC

4) report back to the forum

 

[aerodyne]

TL;DR:

Don't worry about the pack! Get a free copy of Recurrent and you will see your pack is fine, 375 is predicted after 3 years

More:

The MS BMS does recalibration and balancing just fine without any help from you. Range loss you are seeing is probably real and is mostly due to calendar aging, nothing you can do about that short of keeping the car in a meat locker.

Even if you had the pack sit at 50-35% for months like I did, the BMS will be able to compensate. First charge will regain the mile or two you "Lost"

You might see a mile or three of range improvement with you charging excercise just by keeping the pack warmer than it would normally be, or it could be rounding errors.

Instead I would suggest per the latest guidance:

1) Avoid long spells (overnight) below 30 or above 80% SoC.

2) Get more range by driving a little slower or precondition and scheduled charging.

 

[AAKEE]

1) Avoid long spells (overnight) below 30 or above 80% SoC.

Do you have any facts supporting that?

Low SOC is favorable for low degradation (low calendar aging) according to all research.

(I regularly leave my car at ~7-20% at work for one week at the time. ~ 7% is to have margin for ques/road accidents and short rerouting as I go into Alert readiness when I arrive at work.
If below 30% was not good my M3P 2021 i had until this summer would not have been among the cars having the lowest degradation at teslafi etc. I had a SOC average of 35.46% the first 1.5 years).

In my world the lower SOC point is range anxiety only (as long as we do not drive below 0% or leave the car below 0%.).

 

[aerodyne]

Do you have any facts supporting that?

Low SOC is favorable for low degradation (low calendar aging) according to all research.

(I regularly leave my car at ~7-20% at work for one week at the time. ~ 7% is to have margin for ques/road accidents and short rerouting as I go into Alert readiness when I arrive at work.
If below 30% was not good my M3P 2021 i had until this summer would not have been among the cars having the lowest degradation at teslafi etc. I had a SOC average of 35.46% the first 1.5 years).

In my world the lower SOC point is range anxiety only (as long as we do not drive below 0% or leave the car below 0%.).

The self labelled experts at Recurrent wrote an article that talked about avoiding below 30%. The reason was not given. It could be to avoid range anxiety if you were away from the car and it was not plugged in.

Elon tweeted in 2019 for 18650 packs, for best pack life operate between 30-70%.

Following his advice, and storing at 55%, I had the highest RR of any 85 pack on Teslafi once. Then the pack failed without warning.

I thought the benefits to degradation are minor below 50%, unless you put the cells in cold storage.

I don't like stopping the charging forcefully below the slider, but will try to not charge up to 50% unless I need it

 

[Steve446]

Of course my 55% is adjusted for the true SOC, so safe
(Already answered exactly this a few days ago).

The true SOC limit for calendar aging invrease with SOC is around 57-58% on a new NCA cell (it sctually can differ if the chemidtry or amount of different chems on the anode or cathode).

Google calendar aging + central graphite peak for more info.

This ”limit” increases from calendar aging, so a calendar aged cell with 5% loss would have it somewhere around 60%.
But the ”limit” decreases by lithium plating, which we get from fast charging.
In general, I would guess the ”limit” goes up for more or less anybody, so 57% True SOC is safe.

The buffer is 4.5% below 0% displayed.
100% displayed = 100% true SOC.

This means the true SOC = displayed SOC + ((100- displayed SOC)x0.045.

So, 55% on screen is 57% true SOC (57.025% to be exact).

(I did double check this the first time I connected Scan my Tesla almost three years ago, so it is confirmed to be correct)

I've previously understood the true SoC calculation mentioned above without ever really worrying about it. I don't worry about it now either but, was rather curious about the values shown and had some problems reconciling my calculated true SoC value with the SoC data in my SMT data. Please refer to the screen capture from my SMT ("All", tab). Displayed SoC is 28.8 and I calculate true SoC to be 32 (shown as the SoC min in the screen capture). But what do the other SoC entries correspond to? Any idea?

 

[AAKEE]

I've previously understood the true SoC calculation mentioned above without ever really worrying about it. I don't worry about it now either but, was rather curious about the values shown and had some problems reconciling my calculated true SoC value with the SoC data in my SMT data. Please refer to the screen capture from my SMT ("All", tab). Displayed SoC is 28.8 and I calculate true SoC to be 32 (shown as the SoC min in the screen capture). But what do the other SoC entries correspond to? Any idea?

No, I havent even tried to.

I guess where finte to know the displayed and true SOC for our concerns. If I remember it right, the Scan my Tesla people and the people that decoded the canbus data did not either understand it either.
One could assume that as there is imbalance in the cells, there is a slight difference in SOC (SOC is defined by the OCV on the cell). But the differences in soc max and avg is way to high compared to SOC min/true SOC so it is not that either. Just forget about them and live happily ever after

 

[Steve446]

No, I havent even tried to.

I guess where finte to know the displayed and true SOC for our concerns. If I remember it right, the Scan my Tesla people and the people that decoded the canbus data did not either understand it either.
One could assume that as there is imbalance in the cells, there is a slight difference in SOC (SOC is defined by the OCV on the cell). But the differences in soc max and avg is way to high compared to SOC min/true SOC so it is not that either. Just forget about them and live happily ever after

Thanks for the insight! Good to know that they don't know either