What should my ideal charge percentage be?

[AAKEE]

So what do you set for charging %? Do you plug it in every night if possible?

I use 55% as the standard charge.
I use scheduled charging to have the car charged just in time before driving weekdays.
I charge every night when at home. I have a average of sligthly more than 1 charge each day ( 0.97 days between charges).

At my (new) work the car is parked for one week each work week. Some workdays I do a small trip to the store or so.
I have 240km to work so when I arrive I leave the car as is during the week (arriving with 15-30% SOC) and charge the day before I go home after one week.

 

[zoomer0056]

Ive been reading, which caused me to reduce max charge from 89% to 69% on my Feb 2022 S with 6500 miles. The battery health, according to Tessie, immediately dropped by 0.1%. From 3.9% to 4.0% degradation. It did not change for a couple of charge cycles. Just for grins I charged today back up to 89%. The Tessie app gave my car back that 0.1%. It now sits back at 3.9% degradation. See that last data point in the pic, that's after going back to 89% max charge.

 

[AAKEE]

Ive been reading, which caused me to reduce max charge from 89% to 69% on my Feb 2022 S with 6500 miles. The battery health, according to Tessie, immediately dropped by 0.1%. From 3.9% to 4.0% degradation. It did not change for a couple of charge cycles. Just for grins I charged today back up to 89%. The Tessie app gave my car back that 0.1%. It now sits back at 3.9% degradation. See that last data point in the pic, that's after going back to 89% max charge.

Real degradation is non reversible, whats lost is lost.
The Battery Management System (BMS) does not know the exact truth but it tries to constantly calculate the actual battery capacity.
The BMS is affected by charging level despite it shouldnt affect the range in short term.

More or less* all data about calendar aging tell us that lower SOC is better. In the case with Teslas LFP this is probably valid also.
So far it looks like the new LFP have lower calendar aging than before but we do not have any exact data yet.

Using high SOC does not seem that bad with the LFP Tesla use. The battery will be fine. Still its probable that using lower SOC average will reduce the calendar aging, even if the BMS show a reducing range.

*) I have seen one research report that showed the same calendar aging at 50% as at 100%, but this was some year ago, like 2017 so not the latest generation of LFP. Any other report from around 2017 show the known ”the lower the SOC, the better”.

 

[AAKEE]

Too late to edit the post above.

One thing that I have mentioned a lot of times is that 100% SOC is not as bad as people think. The forum rumor is that a classic litium battery will take a huge hit if left at 100% SOC. Well, its not true at normal temperatures.

Take a look in the boxed area:
For short term calendar aging we se that 100% is clearly better than 80-90%.
80-90% causes the highest calendar aging.

This is vanid at normal temperstures, and at 50C for the short term ( uppermost orange line) its about the same from 80-100%.

The picture above is for LFP. If the principle is valid for Teslas LFP’s (which is probable), we get the least degradation if we either stay at or below 70% or charge to 100%.

The battery will probably do very fine anyway, but if one would like to minimize degradation I would say the trick is to stay below 70% or charge to 100%.
If arriving at home with >70% charge early to reach 100% soon.
If the SOC is below 70%, charge late works as good also.

 

[Giampigua]

Too late to edit the post above.

One thing that I have mentioned a lot of times is that 100% SOC is not as bad as people think. The forum rumor is that a classic litium battery will take a huge hit if left at 100% SOC. Well, its not true at normal temperatures.

Take a look in the boxed area:
For short term calendar aging we se that 100% is clearly better than 80-90%.
80-90% causes the highest calendar aging.

This is vanid at normal temperstures, and at 50C for the short term ( uppermost orange line) its about the same from 80-100%.
View attachment 871629

The picture above is for LFP. If the principle is valid for Teslas LFP’s (which is probable), we get the least degradation if we either stay at or below 70% or charge to 100%.

The battery will probably do very fine anyway, but if one would like to minimize degradation I would say the trick is to stay below 70% or charge to 100%.
If arriving at home with >70% charge early to reach 100% soon.
If the SOC is below 70%, charge late works as good also.

Do you have similar picture of “non LFP” battery?
I appreciate what you say, but since it’s surprising with respect to what we understood till now for other batteries I am curious about it
Thanks

 

[Giampigua]

Do you have similar picture of “non LFP” battery?
I appreciate what you say, but since it’s surprising with respect to what we understood till now for other batteries I am curious about it
Thanks

As not said: I found it in another thread

 

[zoomer0056]

As not said: I found it in another thread

Which thread?

 

[Arctic_White]

A Tesla with a Panasonic NCA would stand some 500-1000 cycles if charged to 100% and driven to 0% each time, before loosing 20% capacity.
As most people do not do this, the battery would stand much more cycles.

1000 cycles would be about 350-400.000km (400km (250 miles) range from full to empty) or 250K miles.

A average car might do 15.000-20000 km per year?

400.000/20.000 = 1/20 of the 20% loss, or 1% cyclic degradation each year.
In reality the range loss probably is way less for some people that use small cycles.

So if it was not for calendar aging, we would see very low annual range loss.

Any range loss we see above 1% annually have to be considered to be calendar aging for a car used about average milies.

To get the range loss to be as high or higher from cyclic aging, we need to drive a lot with large cycles.

Teslas range loss graphs shows that the loss flattens. This comes from the calendar aging getting lower with the time.
Cyclic aging is often about the same per cycle even after a lot of cycles.

I've now owned 4 Teslas and my own experience with Tesla says different to what you just wrote above.

Both my 3 LR AWD and Y Performance lost about 7% in the first year, then they tapered off. My used S P100D had no battery degradation for the duration that I owned it (20K miles) at 8% battery degradation.

My S Plaid shows ~1% battery degradation in about 15K miles.

Based on what folks are saying, Tesla battery degrades rapidly in the first year (~8%), and then it stabilizes.

So what you're saying directly contradicts what I've experienced with Tesla vehicles. Not saying you're wrong, but just pointing out a few things to better have an understanding of what's happening.

I have said it before and will say it again: the battery will outlast the car so why bother being so anal about it? Charge it to 90% (or 80%, or 70%) and be happy. Supercharge as often as necessary. The battery can handle it.

 

[Arctic_White]

So, then we all know that low SOC is good. The lower, the better.

The lower the SOC the lower the calendar aging.
The lower the SOC the lower the cyclic aging.
The smaller the DoD, the lower the cyclicaging.

Below 20% is safe: it’s good. In fact, its very good.

100% SOC does not cause noticable more degradation than 70-80-90% as long as the temperature is reasonable.
In principal, there is not nessessary to drive asap after a 100% charge (but of course, we would never recommend to leave the car at 100% for extended time anyway).

OK, we all agree. No one is disagreeing.

But you have failed to demonstrate how much extra will the battery degrade if one is charging at 90% daily. Is it an extra 5% over 5 years? Is it an extra 10% over 10 years? You don't know the answer to that because there are too many variables at play.

Jeez, some of you folks are extremely sensitive! LOL.

 

[Arctic_White]

Too late to edit the post above.

One thing that I have mentioned a lot of times is that 100% SOC is not as bad as people think. The forum rumor is that a classic litium battery will take a huge hit if left at 100% SOC. Well, its not true at normal temperatures.

Take a look in the boxed area:
For short term calendar aging we se that 100% is clearly better than 80-90%.
80-90% causes the highest calendar aging.

This is vanid at normal temperstures, and at 50C for the short term ( uppermost orange line) its about the same from 80-100%.
View attachment 871629

The picture above is for LFP. If the principle is valid for Teslas LFP’s (which is probable), we get the least degradation if we either stay at or below 70% or charge to 100%.

The battery will probably do very fine anyway, but if one would like to minimize degradation I would say the trick is to stay below 70% or charge to 100%.
If arriving at home with >70% charge early to reach 100% soon.
If the SOC is below 70%, charge late works as good also.

One last thing: you're showing a graph that says average storage in MONTHS. I drive every day (pretty much) so we are not talking the same thing here. For 99% of the folks, they drive several times a day on average. So your post is only applicable to those that are storing and in that case, the evidence is clear: keep your charge low if storing for months and make sure you're not storing in a hot area if you can help it.

But for day-to-day driving, I will add once again that it matters not what the actual charge is. Posts like yours create more uncertainty and doubt which is counter-intuitive and makes it more confusing. (I know you're trying to help.)

 

[AAKEE]

But you have failed to demonstrate how much extra will the battery degrade if one is charging at 90% daily. Is it an extra 5% over 5 years? Is it an extra 10% over 10 years? You don't know the answer to that because there are too many variables at play.

It had been done numerous times by me, just search the forum.

There is not very many variables except finding out the average SOC: What SOC do the car stand with for the most part of the time and what is the average temperature.

The charts below show that having the SOC below 55% will cut the calendar aging in half compared to a SOC higher than this.

At 25C the first year will cause a calendar aging of about ~3% while at 90% the calendar aging will be more than 6%.
Cyclic aging is very small for most people, like 0.5% or so, so the sum is 3-3.5% ish for 50% vs 6-7% for 90%.

Calendar aging reduce with the square root of time so degradation will be smaller as time goes but the 50% SOC will continue to be ~1/2 of the 90% SOC.

Jeez, some of you folks are extremely sensitive! LOL.

I’m not sensitive, just trying to be very clear.

 

[Dave EV]

I've now owned 4 Teslas and my own experience with Tesla says different to what you just wrote above.

Both my 3 LR AWD and Y Performance lost about 7% in the first year, then they tapered off. My used S P100D had no battery degradation for the duration that I owned it (20K miles) at 8% battery degradation.

My S Plaid shows ~1% battery degradation in about 15K miles.

Based on what folks are saying, Tesla battery degrades rapidly in the first year (~8%), and then it stabilizes.

So what you're saying directly contradicts what I've experienced with Tesla vehicles. Not saying you're wrong, but just pointing out a few things to better have an understanding of what's happening.

I have said it before and will say it again: the battery will outlast the car so why bother being so anal about it? Charge it to 90% (or 80%, or 70%) and be happy. Supercharge as often as necessary. The battery can handle it.

Your experience is not typical, as previously mentioned, because you live in Edmonton, Canada where the average temperatures are significantly lower than where most people live.

I would estimate that your battery averages at least 10C cooler than the average person living south of the 40 latitude, and probably upwards of 20C cooler many times. Your car sees snow a lot of the year. My car's battery has never seen snow, the battery rarely gets below 20C and deals with 35C temps a lot of the summer!

Arrhenius equation (and the data that AAKEE posted) shows the effects of hot temperatures on both calendar and cycle life.

If you live where your battery stays below 20C nearly all the time and even if it does get heated up, ambient temps quickly cool it back down, don't worry about your SOC!

But if you live where the battery spends a lot of time at 30C+, you will see 2x the rate of capacity loss - so limiting your max charge to <= 55% and keeping your average SOC low will help you match the rate of capacity loss of a cooler climate.

 

[AAKEE]

I've now owned 4 Teslas and my own experience with Tesla says different to what you just wrote above.

I do not think it is different really.

The post above, the cited part was only about cyclic aging. I have written about this a lot of times: Cyclic aging is a very small part for the most people.
Each post tend to be long enough anyway and adding all information in each pist is not possible.

Your cars battery will continue to degrade from cyclic aging even when the calendar aging has gotten really low.

Both my 3 LR AWD and Y Performance lost about 7% in the first year, then they tapered off.

It probably did not flatten of completely.
Calendar aging reduces with (about) the square root of time so the degradation in the first year takes four year in total to double.

Here’s teslaloggers data chart for M3 LR. It clearly didnt flatten after one year.

My used S P100D had no battery degradation for the duration that I owned it (20K miles) at 8% battery degradation.

My S Plaid shows ~1% battery degradation in about 15K miles.

My M3P had no degradation at all according to the range (and BMS figures) for the first 1 1/2 year and 38.000km.
But this does mot mean that the battery degraded. It means that Teslas BMS sometime failes to follow the actual degradation and no not always show the appropriate range.

Based on what folks are saying, Tesla battery degrades rapidly in the first year (~8%), and then it stabilizes.

People also say that the battery get damaged if left at 100% SOC more than very briefly.
People also say that 80% or 90% is the optimum SOC charging target.
People also say that batteries get damaged below 20% SOC so it should be avoided.

In many cases, its the same people that say the statement you wrote (“rapidly first year, then stabilises”) as the three I wrote.
The three I wrote is not true. They are forum myths.
Research and data tell us facts.

The total degradation will look about as the M3 LR chart above. Initially high and it will reduce with about the square root of time.
If you have 5% the first year, you will have about 10% after four years and about 20% after 16 years. So it “stabilises” slowly.
What we see in the cars range is also affected by software changes to the range calculation, this is not always the same as true degradation.

So what you're saying directly contradicts what I've experienced with Tesla vehicles. Not saying you're wrong, but just pointing out a few things to better have an understanding of what's happening.

I have said it before and will say it again: the battery will outlast the car so why bother being so anal about it? Charge it to 90% (or 80%, or 70%) and be happy. Supercharge as often as necessary. The battery can handle it.

I have also always said that for more or less anyone, the battery will outlast the car.
There is no need to look after the battery, but If you do you might cut the degradation in half. Everyone is different, so its a free choise.

 

[AAKEE]

One last thing: you're showing a graph that says average storage in MONTHS. I drive every day (pretty much) so we are not talking the same thing here. For 99% of the folks, they drive several times a day on average.

Most people do not drive not that much in hours each day. An average car is not used for 20hours or so each year.
While the researchers in most cases divide the degradation into calendar aging and cyclic aging, calendar aging happens even if the car is used (because time goes by even if the car is driven, maybe except for the Plaid ) Some researchers do present calendar aging as a part of the cyclic aging test.
Count the calendar aging, as it happens anytime is the easiest way, and it is also correct.
If you like to see it the other way, your car probably is not on the road for ~20h each day (or more) so you still have 83% or more of the calendar aging.

So your post is only applicable to those that are storing and in that case, the evidence is clear: keep your charge low if storing for months and make sure you're not storing in a hot area if you can help it.

Well, its also applicable to all other.
(The battery resesrchers use the same viewpoint as I present here.)

But for day-to-day driving, I will add once again that it matters not what the actual charge is.

Your statement is wrong.

Posts like yours create more uncertainty and doubt which is counter-intuitive and makes it more confusing. (I know you're trying to help.)

I try to help with facts found and the feeling I get is not as you wrote above.

I try to kill the myths about batteries, and there is seldom that much worries or protests. I guess the ones protecting the myths is the ones that have ”non happy posts” ( I do not mean you )

 

[patgilm]

After reading this thread I put in a service request to check the health of the battery and got a call from the service guy yesterday and he said my battery is at about 86% and he looked at my charging history and said I’m doing nothing wrong, keep doing what I’m doing. Health of my battery is fine and within spec. If it gets below 70% then it could be replaced under warranty.

 

[AAKEE]

After reading this thread I put in a service request to check the health of the battery and got a call from the service guy yesterday and he said my battery is at about 86% and he looked at my charging history and said I’m doing nothing wrong, keep doing what I’m doing. Health of my battery is fine and within spec. If it gets below 70% then it could be replaced under warranty.

What car, age (of the car ) and how’s your charging habits?

Maryland, huh…. hot climate?

 

[patgilm]

What car, age (of the car ) and how’s your charging habits?

Maryland, huh…. hot climate?

22 Plaid with 17k miles. I charge to 90% every night which the Tesla guy said was perfectly fine.

 

[AAKEE]

22 Plaid with 17k miles. I charge to 90% every night which the Tesla guy said was perfectly fine.

Did you ask Tesla SC because you did see a big drop in range?
Seems like a big capacity drop for about one year…
I guess Maryland isnt that hot?

 

[patgilm]

Did you ask Tesla SC because you did see a big drop in range?
Seems like a big capacity drop for about one year…
I guess Maryland isnt that hot?

LOL no believe it or not I asked them because of this thread and was just curious. I did notice when I charged to 90% when I got the car it showed a range of 353 miles and now it shows 319 miles but the range it shows really doesn’t mean anything.

Maryland can get hot in July/August and today it is unseasonably cold at 32 degrees Fahrenheit.

 

[Leeclanual]

Im going with the 70% charge plan… see how it goes.