Tesla sets charge limit to 90%

[AAKEE]

@AAKEE

So, in my situation, I drive about 25 miles a day. For the best results, I plan to charge to 50-55%. Would you recommend charging everyday even though my SOC at the end of the day is around 40-45% or should I charge every 3-4 days when my SOC is down to 20%? Also, I will plan to schedule my charging to happen closer to leaving home in the AM when I do go to hook up. Thanks for the info!
Chad

I did set 55% when the car was new, even if 50% would have been enough.

When at home I charge mor or less every day, but late (about 03:30 Am) even if I havent driven the car. My routine is to connect it when parking in the garage.
As I do it, I actually follow the instructions Tesla give.

Charging more seldom would reduce the average SOC. But the research shows that there isnt a big difference between 30-55%.
(There is a plateau between 30-55%, and also between 60-90%)
Because of this it would not make a big difference, only a very small one. The big difference lies in going below 55% displayed SOC.
If charging more seldom the cycles get bigger which can be assumed to increase the cyclic wear, so in total there probably is no win in delaying the charging as the reduction in calendar aging is very small but the cyclic aging increase slightly.

 

[SageBrush]

(There is a plateau between 30-55%, and also between 60-90%)

There is nothing magical going on between 54% and 61%. Chemistry kinetics are a continuous function. The plateaus of which you speak are artefacts

 

[radchad3]

Thank you both for the replies. I will plan to charge daily then. Last question, I have the ability to charge at 48A. Is there any advantage/detriment to charging at a slower rate, say 32A?

 

[AAKEE]

There is nothing magical going on between 54% and 61%. Chemistry kinetics are a continuous function. The plateaus of which you speak are artefacts

Nope, not at all. What I refer to is accepted facts among researchers. There is no research data suggesting otherwise.

The degradation from time is caused by a few factors, one with big influence is the anode potential. Low anode potential is bad, and that lowers with increased SOC but not in a linear way. There are plateaus in the anode potential that is similar to the calendar aging rate.

There is a lot of research on this.
Some researchers only set up a few different SOC test points and then draw straight lines between them, effectively hiding the reality.

I so far have not seen any multi test points not showing the fact that below the central graphite peak you have much lower calendar aging. The two-five SOC data point tests follow the same data, not different at all but these have to low resolution.

The anode potential can be seen in the upper graph.

 

[AAKEE]

Thank you both for the replies. I will plan to charge daily then. Last question, I have the ability to charge at 48A. Is there any advantage/detriment to charging at a slower rate, say 32A?

Any AC ”home charging” is at 11kW or below. It is so ”slow” that it is considered slow charging anyway.
11kW is about 0.15C which is very safe charging.

0.15C equals about 0.4A in this graph:

You can see that all charge rates below 1A (is = 0.35C on that battery) is not making any difference in degradation.

 

[dhrivnak]

Just took delivery on my MYLR three days ago. Tesla has the charge limit set to 90%. I see many here set it to 80%. I do have a garage with a wall connector installed and set to full 48A charging. Would it be more beneficial for the battery if I dial it back to 80%? Daily work commute is about 40 mi RT. I've only charged it a few times and the max charge so far is 66 mi.

I charge to 90% and my pack is 94% of new after 108,000 miles. I learned on the Roadster that below 85% the cells do not properly balance leaving you at the weakest brick.

 

[AAKEE]

I charge to 90% and my pack is 94% of new after 108,000 miles. I learned on the Roadster that below 85% the cells do not properly balance leaving you at the weakest brick.

How did you come up to 94% ?

More or less any time this have been properly checked the degradation numbers are not correct.

What car do you have (model, year and battery?)
What range does it show at 100% or 90% ?

We can calculates the degradation from this and see if it is correct.


The balancing part is not a problem for me at least.
I have logged data (Scan my tesla sends) and even after very long periods at charging to 55% and fis harging to anytking between 10 and no drives between charges I have 4mV imbalance. Teslas logic only balances if the imbalance is 5mV or more.
2 years and 4 months of low SOC strategy, I occasionally do longer trips needing higher SOC.

 

[SageBrush]

You can see that all charge rates below 1A (is = 0.35C on that battery) is not making any difference in degradation.

That data has to be viewed in the context of temperature. Re-do the tests at 0C or below and I'm not sure that 11 kW (say, 0.15C) will not have increased degradation

 

[dhrivnak]

How did you come up to 94% ?

More or less any time this have been properly checked the degradation numbers are not correct.

What car do you have (model, year and battery?)
What range does it show at 100% or 90% ?

We can calculates the degradation from this and see if it is correct.


The balancing part is not a problem for me at least.
I have logged data (Scan my tesla sends) and even after very long periods at charging to 55% and fis harging to anytking between 10 and no drives between charges I have 4mV imbalance. Teslas logic only balances if the imbalance is 5mV or more.
2 years and 4 months of low SOC strategy, I occasionally do longer trips needing higher SOC.

Most days I record the Miles of range and log into a spreadsheet now 5+ years old. Current average is 267 miles at 90%. Last full charge was 297 down from to initial 310.

 

[AAKEE]

That data has to be viewed in the context of temperature. Re-do the tests at 0C or below and I'm not sure that 11 kW (say, 0.15C) will not have increased degradation

Tesla always heat the battery before needed if the battery is to cold. If connecting the charger with a sub freezing temp in the cells there will only be cell heating initially and when the cells is heated enough the charging will start. We do not even need to think about this, as Tesla manages it automagically.

I have a lot of logged data. This is in february when the car had been parked for a week at work, except a short trip to the local store.
Cell temp -1.5C when I set the charging to "on" (UMC 230V set for max 10 to12Aor something).
The battery power was 8kW and SOC reduced from 35 to 29% before the charging commenced.

At Cell temp 3C no charging was either done or allowed, but at 3.5C 1kW max charge power was allowed and at 3.75C cell temp the BMS max charge power was 3.85kW, which is more than the 10-12A/230V gives (2.3-2.8kW).

At

 

[SageBrush]

Tesla always heat the battery before needed if the battery is to cold.

Very true, but I was talking about interpreting the cell degradation studies

 

[GreenCoffee]

Congrats. Just took delivery of mine today after 7 months of having a Model 3.

Lots of debate on this. In my opinion there are two schools of thought, one super in-the-weeds, the other not so much:

1. Figure out a charge limit that allows the car to sit as close to 50% as possible for as long as possible (in theory this is best for the battery long term). For instance, I set my charge limit to exactly 57% and I schedule charging using the off-peak hours to end right when I leave for work. I drive to work and end up there at about 54%, the car sits at that SOC while I'm at work, then I depart and arrive home right at 50% give or take where it sits until the whole thing repeats. On the weekend I usually set it to 55%. I'm weird so I actually enjoy this sort of granular charging habit and wish I had more control over it in the app.

2. Set the charge limit to 80 or 90 and don't worry about any of that above.

I'd go with whichever method sounds the best for you. If you never want to worry about it, set it to 90 percent and never think about it again (or 80% doesn't really matter, might be slightly better for the battery long term). If you like the sort of thing described in #1 then go for that.

Edit to add that setting it to a lower SOC will mess with the car's ability to estimate the range (though not its actual range), which is why Tesla recommends 90%. Lots of threads on this if you do a search, especially in the Model 3 forums.

I prefer to set mine at 57.83576021% because I tend to use 15.6715204% on an average daily use and this way I use exactly the same amount over and under 50%

Just kidding, I charge to 90% whenever it drops below 50%

 

[Iron]

I learned on the Roadster that below 85% the cells do not properly balance leaving you at the weakest brick.

This is quite the statement. Links?

 

[dhrivnak]

This is quite the statement. Links?

No links but it was easily observable as one can bring up the balancing screen. Ask any Roadster owner.

 

[Iron]

No links but it was easily observable as one can bring up the balancing screen. Ask any Roadster owner.

Went searching and as a by-product, found this from Tesla....
The whole article is interesting.

A Bit About Batteries | Tesla

www.tesla.com

Calendar Life

Li-ion cells lose capacity with time, even if they are just sitting on a shelf. They lose the most early in their life (year one) and then continue to lose capacity gradually thereafter. Two factors shorten calendar life considerably: lifetime average temperature and time spent at high states of charge. Batteries would last the longest if they were stored in a refrigerator at a very low state of charge. They age the fastest when stored in a hot place at a full state of charge – like those in your laptop computer, plugged into its charger and being cooked by a toasty Pentium processor. At Tesla Motors one of our key inventions to maximize battery lifetime is a sophisticated liquid cooling system that maintains a favorable temperature for the batteries, even under extreme ambient conditions. Our cooling system engages to try and keep the temperature of the cells below 35° C at all times and the lifetime average temperature at or below 25° C.
The battery pack gets a lift
The other significant factor that affects calendar aging is the charge state of the battery during storage. At higher charge states cells lose capacity faster. This is a second reason why we have limited our maximum state of charge to 4.15V/cell instead of 4.2V/cell. We also offer the driver the option of charging to only 3.8V/cell (~50 percent) or 4.10V/cell (~90 percent) to further extend calendar life if the full vehicle range is not needed on the next few trips. We advise and encourage a full (4.15V/cell) charge only when it is needed. So what does this all mean for the real-world performance of a car? As batteries in any EV age, they lose capacity and the vehicle will lose range. This is unavoidable and true in any EV with any type of battery. You can think of this as a very slow reduction in the volume of your vehicle’s “gas tank” over its lifetime. We limit how fast this aging and loss of range happens by working very hard to select the best cells, design the best cooling systems, and carefully manage charge states. By doing all of this we expect more than 100,000 miles of driving range and more than five years of useful life. However, at the end of this period the pack will have less capacity than when new (just like an internal combustion engine has less power and much worse emissions than when new). If, for example, you drive 10,000 miles per year at the end of five years you will have around 70 percent of the energy storage capacity of when new. This performance gives the Tesla Roadster battery pack the best range and lifetime combination of any production EV battery ever built. Consider that even after five years and an aggressive 100,000 miles of driving, the Tesla Roadster pack will have more energy storage available than the Gen2 EV1 (with its high-capacity NiMH cells) had when it was NEW!

Footer menu​

• Tesla © 2023

 

[AAKEE]

Photo is 30 minute old.

4 mV is the usual imbalance at mine pack, normally charge to 55% since the car was new. Higher SOC for longer drives, I always time it so it doesnt really leave any time to balance the pack.

It is also so, that a pack that was just balanced at top have slightly more imbalance at middle and low SOC.
If I had charged to 90 or 100% and then driven down to 55%, and given it a rest, it would not have less than 4mV. If any, more as the cells was balanced at top.

 

[RichAZ/CapeCod]

Thank you both for the replies. I will plan to charge daily then. Last question, I have the ability to charge at 48A. Is there any advantage/detriment to charging at a slower rate, say 32A?

While I fully admit to enjoy reading and learning about EV battery life and how to best keep them healthy, I will also admit that I sometimes suspect many of us are debating how many angels dance on the head of a pin.

For the record I have two Teslas (Y LR & 3 SR). I charge at 32A from a mobile connector. The connector charges the vehicles up so quickly that I personally never had the need to charge at a faster rate for a shorter charge time. You may have other needs.

I "think" that charging at 32A over 48A "may" be a good thing. I'm sure someone/s will soon comment one way or the other on the matter.

Rich

 

[AAKEE]

I "think" that charging at 32A over 48A "may" be a good thing. I'm sure someone/s will soon comment one way or the other on the matter.

Rich

Already commented a bit up 32A = 48A

32A will not be worse than 48A, for the cyclic degradation part.

If one like to reduce the time at high SOC by charging late (above 55% for LR / P cars) and usually have the car sitting below, a shorter charge will reduce the time at high SOC.
I always have the WC at 3 phase 230V 16A, which is 11kW.

Also, if one would like to save energy, the faster the AC charge is, the lower is the losses. The car use about 200Wh each hour it is awake, as when charging.

An average car might do 10K miles a year? (Give or take…)
Thats 3200 kWh which equals about 914 hours of charging.
With 48A thats 606hrs of charging.

300 hrs less charging time is about 60kWh of extra losses. Not much, but anyway.

 

[johnny_cakes]

Went searching and as a by-product, found this from Tesla....
The whole article is interesting.

A Bit About Batteries | Tesla

www.tesla.com

Calendar Life

Li-ion cells lose capacity with time, even if they are just sitting on a shelf. They lose the most early in their life (year one) and then continue to lose capacity gradually thereafter. Two factors shorten calendar life considerably: lifetime average temperature and time spent at high states of charge. Batteries would last the longest if they were stored in a refrigerator at a very low state of charge. They age the fastest when stored in a hot place at a full state of charge – like those in your laptop computer, plugged into its charger and being cooked by a toasty Pentium processor. At Tesla Motors one of our key inventions to maximize battery lifetime is a sophisticated liquid cooling system that maintains a favorable temperature for the batteries, even under extreme ambient conditions. Our cooling system engages to try and keep the temperature of the cells below 35° C at all times and the lifetime average temperature at or below 25° C.
The battery pack gets a lift
The other significant factor that affects calendar aging is the charge state of the battery during storage. At higher charge states cells lose capacity faster. This is a second reason why we have limited our maximum state of charge to 4.15V/cell instead of 4.2V/cell. We also offer the driver the option of charging to only 3.8V/cell (~50 percent) or 4.10V/cell (~90 percent) to further extend calendar life if the full vehicle range is not needed on the next few trips. We advise and encourage a full (4.15V/cell) charge only when it is needed. So what does this all mean for the real-world performance of a car? As batteries in any EV age, they lose capacity and the vehicle will lose range. This is unavoidable and true in any EV with any type of battery. You can think of this as a very slow reduction in the volume of your vehicle’s “gas tank” over its lifetime. We limit how fast this aging and loss of range happens by working very hard to select the best cells, design the best cooling systems, and carefully manage charge states. By doing all of this we expect more than 100,000 miles of driving range and more than five years of useful life. However, at the end of this period the pack will have less capacity than when new (just like an internal combustion engine has less power and much worse emissions than when new). If, for example, you drive 10,000 miles per year at the end of five years you will have around 70 percent of the energy storage capacity of when new. This performance gives the Tesla Roadster battery pack the best range and lifetime combination of any production EV battery ever built. Consider that even after five years and an aggressive 100,000 miles of driving, the Tesla Roadster pack will have more energy storage available than the Gen2 EV1 (with its high-capacity NiMH cells) had when it was NEW!

Footer menu​

• Tesla © 2023

Right from the horse's mouth. It's also consistent with all the research reports that @AAKEE 's been posting. Thanks for sharing this. Hopefully this dispels the "Tesla recommends charging to 90% daily for best battery health" myth.

 

[Iron]

Right from the horse's mouth. It's also consistent with all the research reports that @AAKEE 's been posting. Thanks for sharing this. Hopefully this dispels the "Tesla recommends charging to 90% daily for best battery health" myth.

They actually do that too. It's the standard charge when they deliver vehicles. At least mine was @ 90%... hence this thread.

Home Charging - Frequently Asked Questions

Learn more about how to charge a Tesla at home, including home charger installation costs, equipment options and how long it takes to fully charge a Tesla battery.

www.tesla.com