Is 100% charge on MYLR once a month good for extended battery life?

[AlanSubie4Life]

Right or wrong I never saw more than 315 miles even after the "unlock" and 309 when new.

Yeah that is fine.

We know from SMT captures that these vehicles had at least 76kWh when new (captures from LR RWD posted on this site show greater than that for a 9-month-old car as I recall), so just stating the actual capacity loss of the pack.

The achievable range may or may not have changed as much (hard for me to know for sure due to unknowns about exactly how that 310->325 was achieved - I have my guesses but I haven’t hunted for “proof” because it doesn’t matter for purposes of capacity loss).

Pack that has FPWN value of about 77.8kWh now has estimated capacity of ~69kWh. That is all I was making a statement about.

 

[CaseyL]

I'm picking up my wife's car tomorrow and all this information has been helpful.

If she is a person that probably drives 25 miles or so a day, mainly errands and picking up the kids, would it be best to let the charge get down lower and then charge it up at the end of the week? Or just set a charge limit like 55-60% and do it daily?

Thank you in advance.

I commute about 50 miles round trip most days. I have the car set to charge every morning at 4:00am to 50%. I usually return home from work with about 34% left. Car still has plenty of "oomph" in that range.

This is just my personal routine (except for road trips). It works for me.

 

[dhrivnak]

Agreed. I took it as 90% or less also. If dropping to 50% were an issue, the message would have reappeared.

I believe the 90% recommendation is to provide good range. I'm sure they don't want those limiting charge percentage to hurt their long range reputation. You know how perception can be. Basically, we are operating the vehicle somewhat like a Nissan Leaf, even thought it has way more capability.

I only noticed it because last night I decided to charge to 90% after midnight, so it would charge with enough time to sleep for 3 hours, before I left for work. This is purely for calibration/cell balancing purposes. Was going to do 100% but the message dissuaded me. I'll be back to 60% tonight.

Interesting that for the 6 months in 2019 you charged to 80%, you experienced the range loss. Was anything else different about your routine?

The numbers are the numbers the car showed at 90 or 80% they are NOT corrected to the 100% charge level. Sorry for the confusion.

 

[flixden]

While I do not recommend to leave the battery often at 100%*, it is not at all that bad as the myth says.
Calendar aging is about as bad at 80% as it is at 100%. In some cases, 80% is the worst SOC to have the battery at.

Here’s a common result of calendar aging:
For 60-100% the calendar aging is virtually the same. At high cell temps, its just a little higher at 100% than at 60-80%.
This means that at 40C 9hours at 100% wears as much as 10 hours at 25C.
View attachment 956672

This is a almost new real Model S pack taken apart and the cells tested:
80% is the worst SOC among the tested SOC’s (not multipoint, but 20,50 and 100% is also tested)
View attachment 956673

This is 2170 NCA cells ”of a non disclosed brand”.
View attachment 956674

I did buy 35 pieces of Tesla model 3 2170 NCA cells, and performed calendar aging tests for 1.5 years. My numbers look the same and very very close to the model S cells, I saw ightly less calendar aging at 100% than at 80%. I used Teslas SOC numbers (Voltage vs displayed SOC) for my tests so the 80% I used was the same voltage as when we read 80% displayed.

Besides this, there is literally hundreds of research reports showing the same thing, and none showing that 100% causes rapid degradation. Tesla do not tell us to drive asap after a 100% charge.

Teslas “below 90% daily” is because it makes us use smaller cycles, reducing the cyclic aging with about 30-50%.


*)Because there is no reason to do it. Ot because it is very bad.

The first graph seems to not quite agree with that second one (table). The graph says that 20% SOC degradation is about equal to 50% SOC. The table says that 20% SOC causes 1/3 to 1/2 the degradation, compared to 50%.
Which one do you feel is more accurate?

 

[AAKEE]

The first graph seems to not quite agree with that second one (table). The graph says that 20% SOC degradation is about equal to 50% SOC. The table says that 20% SOC causes 1/3 to 1/2 the degradation, compared to 50%.
Which one do you feel is more accurate?

Use the first graph. That is how they really behave, or how we should think of it. Slight simplification but good enough for understanding.
I actually had to think a little about that the first time I did read that report, to understand why it was so low at low SOC. The most probable explanation is like follows:

There is a recovery effect if the battery has been at high SOC.
These cells where taken from a Tesla Model S that was 6 month old.
Most probably, that owner had charged to 80-90% daily.

This means that the cells resting at low SOC had that recovery where som lithium returns to cycleble lithium.
There are som research that covers this but not very deep. From memory this is one of the better, search for “recovery” in this document:
https://mediatum.ub.tum.de/doc/1355829/document.pdf

I have seen this myself after longer traveling using higher SOC and larger DoD’s and also Supercharing. During the trip the Nomimal full pack reduces slightly and when returning home, and using my normal SOC the capacity increases slightly.

( I mostly use the two lower graph’s to make it extra clear that 80-90% is not the sweet spot in the degradation aspect.)

 

[flixden]

Use the first graph. That is how they really behave, or how we should think of it. Slight simplification but good enough for understanding.
I actually had to think a little about that the first time I did read that report, to understand why it was so low at low SOC. The most probable explanation is like follows:

There is a recovery effect if the battery has been at high SOC.
These cells where taken from a Tesla Model S that was 6 month old.
Most probably, that owner had charged to 80-90% daily.

This means that the cells resting at low SOC had that recovery where som lithium returns to cycleble lithium.
There are som research that covers this but not very deep. From memory this is one of the better, search for “recovery” in this document:
https://mediatum.ub.tum.de/doc/1355829/document.pdf

I have seen this myself after longer traveling using higher SOC and larger DoD’s and also Supercharing. During the trip the Nomimal full pack reduces slightly and when returning home, and using my normal SOC the capacity increases slightly.

( I mostly use the two lower graph’s to make it extra clear that 80-90% is not the sweet spot in the degradation aspect.)

Makes sense, thanks!

 

[agmonaco]

I have a 2023 MYLR (13000 miles) with the 2170 batteries built in Texas. This question has got to of been asked before. I hardly ever need to charge over 70%. I have owned it since May and I have only charged it to 80% a few times and 100% only one time. Is it better for the battery to charge to 100% occasionally (like every couple months) for 2170 battery health? I have never heard a definitive answer from a Tesla battery expert. And if anyone can give a technical explanation on why this helps, please do'. Thx Tony

 

[jjrandorin]

I have a 2023 MYLR (13000 miles) with the 2170 batteries built in Texas. This question has got to of been asked before. I hardly ever need to charge over 70%. I have owned it since May and I have only charged it to 80% a few times and 100% only one time. Is it better for the battery to charge to 100% occasionally (like every couple months) for 2170 battery health? I have never heard a definitive answer from a Tesla battery expert. And if anyone can give a technical explanation on why this helps, please do'. Thx Tony

Not only has " should I charge to 100% occassionally" been asked multiple times before, one of those multiple times is actually a thread you created yourself (which is why I merged your new thread today into the thread you created on this topic previously).

 

[ucmndd]

Is it better for the battery to charge to 100% occasionally (like every couple months) for 2170 battery health?

Still no.

But if it makes you feel better, go for it. There’s no real harm.

 

[agmonaco]

Still no.

But if it makes you feel better, go for it. There’s no real harm.

I have a great memory.. But its just real short. I did a search but did not see my post. Thx.

 

[crunchor]

Many people seem to think that the batteries is damaged by 0% SOC and 100% SOC.

In reality, lithium batteries can be charged
well above the 100% SOC mark.

100% is 4.20V/cell for many chemistries but it is possible to charge them to 4.4V. The
life will not be that many cycles but it can be done.
The battery manufacturers set a max level ( 100% definition, that is safe for the battery in question. When reducing the max voltage from 4.4 to 4.2V this is done to give the battery a descent life with an acceptable number of cycles and calendar aging.
The 100% level set by the manufacturer is of course on a safe level. If the cells would break when used at 100%, the manufacturer would get a lot of warranty exchanges.

The same with the 0% level. 0% is not completely empty but the safe discharge level, set as a minimum discharge level.

The specification might say 500 or 1000
Cycles 100-0% and research tests often
confirm this.

The most left part of the picture is 100% to 0%. Some 625 full Cycles or about 250.000km/155.000 miles. (400km per Full Charge until it stops)
Doing 100% until the car stops well
Below 0% on the screen, will still give us quite many miles to drive.
Middle is about 90% to 0%
Right is about 80% to 0%

View attachment 956736

Well I believe Tesla only cares if its suggestion is good for the car with warranty. If we want to keep using the car after years of end of warranty then it is another story.

I don’t know suggestion form here is good:

Best charging behavior for LFP batteries

I have been writing about the importance of LFP (LiFePO4) batteries for a while now, but I havenât written about the best charging behavior for this battery chemistry yet. Itâs time to write a small, but important article about the subject, especially because I have seen some confusion on online...

pushevs.com

It suggests charge from 70% to 20% only to max battery health. Charge to 100% only when the battery percentage calculate has serious problem if you have lfp and use the battery as soon as possible so not stay at 100% for long time.


He also points out that always lower voltage is much better for battery. For example, 80% to 0% is much better than 100% to 20%.

 

[AAKEE]

I don’t know suggestion form here is good:

Best charging behavior for LFP batteries

I have been writing about the importance of LFP (LiFePO4) batteries for a while now, but I havenât written about the best charging behavior for this battery chemistry yet. Itâs time to write a small, but important article about the subject, especially because I have seen some confusion on online...

pushevs.com

It suggests charge from 70% to 20% only to max battery health.

No.

A brief check showed he’s article linked to another article where he uses som kind of research that is clearly not modern LFP and doesnt match the other mass of research tests. Probably not even LFP in that test. (I know I did read that research long time ago).

Modern LFP’s can do several thousand full 100-0% cycles without much degradation.
Partial cycles, many thousand FCE is expected.

- Cycle depth is a non issue. There is no reason for the sake of the battery to stop discharging at 20%.
- The BMS increases the bufffer below zero to minimize the risk of getting stranded if the BMS sees thecrisk of wrong estimation of the SOC. A full charge with reosonable periodity would be good to make sure that the BMS hasnt ”lost it”.

To sum it up, 100-0% is very okey.

Charge to 100% only when the battery percentage calculate has serious problem if you have lfp and use the battery as soon as possible so not stay at 100% for long time.

No.

How would you know that the ”BMS has problems” ?
Do it on a periodical basis to hinder the BMS from even getting there.

He also points out that always lower voltage is much better for battery. For example, 80% to 0% is much better than 100% to 20%.

But why would he then say 70-20%.

Remember three things:

-Cycle depth of cycle numbers is a non issue in Teslas LFP cars. Do however you like as it in practical terms doesn’t matter.

-Calendar aging is the only thing that matters.

-If yo keep the time short at 100% (100% to 70%) you can charge to 100% any time or how many times you like to or need.


I had over 30 full charges with my Model 3 Performance (not LFP but NCA) over 2.5 years. That averaged > 1 / month. The battery had very little degradation. It still has very little degradation compared to other M3P’s, after 3.5 years (in contact with the current owner).

I now had my Model S Plaid for 10 months (again, not LFP but NCA). I have 13 full charges so far, Yesterday full charge and 100-7%. Drove > 500km.
Again, this car has very low degradation.

At 20K km the car still shows full range.
Nominal full pack 97.1 kWh, and nominal remaining 97.9 kWh out of 99.4kWh.
Thats ~ 2% degradation.
The range doesnt start to drop until 96.2kWh and the mean value at 20K km seems like ~545km which is around 5.5% degradation.
The red line is my markings for my car.

Both cars has often ben parked with low SOC, and used low SOC cycles.

Why do I use my cars with NCA as examples?
Well, NCA is much more sensitive to large cycles than LFP. Much, much more.
Still, doing 100% or down to 0% or both whenever needed will not noticably affect degradation.

The myths keeps people being afraid of things that doesn’t matter and also to increase the degradation.

LFP’s do not (in practical terms) care about the cycle size or high/low cycles.

LFP’s care about calendar aging in about the same way as the other common chemistries does.

 

[QtownTaxiGreg]

How would you know that the ”BMS has problems” ?

Reporting a much reduced range would be one way of telling.

 

[QtownTaxiGreg]

I got my new car theis afternoon. No spec on the battery chemistry can I find in the dash screens. Only says "lithium ion" which could be anything.

 

[AAKEE]

Reporting a much reduced range would be one way of telling.

No.

When the buffer increases, each mile get less energy. So with a large buffer means less Wh/mile but same max range (information from the ones that check this up, I did not check it myself but info from a thrustworthy source)

You would need to charge full to see this (as the range for a partial charge vary several miles on the same SOC number), or use for example scan my tesla to read the buffer number.