SOC, minimal bottom and above top SOC range iddling time

[Nikon201068]

Hello TMCers, I like to know how long can the car sit iddling at bottom SOC (let's say around 20% or less) before I should charge it back up to at least 50% or more. Also, how long can the car sit iddling at above SOC (let's say 90% or more) before it should be driven to bring the SOC to more ideal range? Is it few hours or a day or more? Thank you kindly for your inputs.
Edit: I mainly like to know in regard to battery degradation how long or how soon you should charge or drive off to minimize battery degradation.

 

[SageBrush]

No or very few battery changes on warranty that was caused by too high degradation.

That is an allowance of up to 30% degradation over 8 years. Personally, I'll take steps that will hopefully result in much less.

 

[AAKEE]

That is an allowance of up to 30% degradation over 8 years. Personally, I'll take steps that will hopefully result in much less.

Yes, I do too.

Still about 79kWh capacity, of 82 Full pack when new (498km at last full charge, from 507km) after 2 years and 1 month, 57.000km.

I have data on the average SOC (about 45%) and battery temp (13C).
My average SOC has climbed from about 35%. After changing job the car stsbds home with 55% more often. Earlier each night during weeks was about 15-20 to 30%.
I have done about 47 Supercharging sessions and some 25 full charges.
Still, the all 7 other M3P 2021 average shorter range.

 

[BitJam]

Also, it will take time to gain thrust to the insight that what you learned earlier might not be right.

I know there is not many others that spread facts about batteries that comes from research and real tests. Some others do, that theoretically could have been “fooled” by me.

Yes. Kyle Conner is usually a reliable source EV information. I've learned a lot from him and his influence helped me decide to buy a Tesla. When you posted your refutation to what I said, I didn't have time to really dig into it which is why I marked it as informative but didn't post a reply.

I'm still wading through the long How I Recovered Half of my Battery's Lost Capacity thread.

I was going to suggest that you start a battery myths thread but I see you already did.

 

[AAKEE]

In any of the applications tesla did send to the Environmental Protection Agency, they state that the battery if stored hould be stored at 15-50%.
Basic Search | Document Index System | US EPA

Postim pictures does not work right now, but the text say:

To maintain service life, the battery pack should be stored at a state of charge (SOC) of 15 to 50%

My guess is that the lower number is not due to that its bad for the battery but to ensure it stays above 0% SOC or so if it is stored for long time.
(as there is absolutely no data that shows that below 15% is not good).

 

[Hayseed_MS]

Can degradation be reversed at all if charging habits are changed?

 

[ucmndd]

Can degradation be reversed at all if charging habits are changed?

My understanding is no. Degradation is permanent physical/chemical change to the cells.

 

[AAKEE]

Can degradation be reversed at all if charging habits are changed?

As @ucmndd said, it is easiest to consider degradation permanent.

There is a recovery effect after time at low SOC, though.
I havent digged into it and can not give any numbers.

This is partly guessing as I only read what accidently came before my eyes, and have not studied it specifically:
Most probably you wont notice a big difference (at all?) after years at high SOC.
If you use low SOC normally and make a full charge/cycle and then return to low SOC you might get more recovery, possibly nulling out the effect of the larger cycle.

 

[DrChaos]

You are reading the graph the same way I would read it, but you will have to come up with a reasonable physical mechanism before I take it seriously.
Arrhenius is turning over in his grave. Until proven otherwise, this observation is artefact

Battery chemistry and degradation is very very complex, there are many aspects of chemistry going on at once.

The papers AKKEE referenced (and many more) are about that very phenomenon. There are some irreversible slow reactions on anodes and cathodes which take place over time which sequester actively cyling lithium (reducing capacity), and the rate of these reactions depends on temperature and state of charge.

 

[BlouieM3]

There so much going back and forth regarding when to charge etc.

Right now for my Wife’s 2023 Model Y perf.

We’re charging every night since Tesla recommends leaving your device plugged in.

1. 80% charge limit after 12am
2. Commute everyday is around 70 miles so she has around 45-50% when she’s home.

So the car is being plugged in 45-50% SOC to 80% every night.

Does this sound optimal long term for our battery or maybe lower the limit to 70%? So that it’s more of the range of 35 to 70% charge daily? Thanks everyone!

 

[DrChaos]

There so much going back and forth regarding when to charge etc.

Right now for my Wife’s 2023 Model Y perf.

We’re charging every night since Tesla recommends leaving your device plugged in.

1. 80% charge limit after 12am
2. Commute everyday is around 70 miles so she has around 45-50% when she’s home.

So the car is being plugged in 45-50% SOC to 80% every night.

Does this sound optimal long term for our battery or maybe lower the limit to 70%? So that it’s more of the range of 35 to 70% charge daily? Thanks everyone!

Optimal is set charge limit between 50% and 55%. I choose a random number between 50 and 55% each time I reset charging (to help BMS recalibrate).
Not much difference between 70% vs 80%, but there is a step in degradation around 55%, below that is better. The longer interval of time the state of charge is below 55% the lower the degradation.

You still have enough charge for every day commute, 50%->20%. Of course if it's uncomfortable or you need more on the weekends set it higher. I also set time-of-use period and scheduled departure so it charges at end of my 12AM-6AM cheap period which is slightly more optimal as well.

 

[AAKEE]

There so much going back and forth regarding when to charge etc.

Much of the back and forth are myths, if you ask me

Right now for my Wife’s 2023 Model Y perf.

We’re charging every night since Tesla recommends leaving your device plugged in.

1. 80% charge limit after 12am
2. Commute everyday is around 70 miles so she has around 45-50% when she’s home.

So the car is being plugged in 45-50% SOC to 80% every night.

To begin, just following Teslas simple advice will keep your battery fine with no issues. It will not give the lowest degradation though.

You can see that calendar aging is higher above 55%. Any time above increase the degradation. To reduce degradation its good to have more time at or below 55%, than above.
Temperature also has an impact but most people can not do anything about it.

To reduce the back and forth thing, I throw in sources for my statements and and to stress that that picture above is valid (its virtually the same as a lot of other research), I add a few pictures from other research:

Cut in another way of displaying, this is actual model S cells tested in the same way (time about 6 months or so, so basically the same rate as above):

This is actual model 3 cells, only three different SOC’s but they match the first picture very well.

I guess the above is data enough to make the case. All other research reports also implies about the same thing. No single report supports the forum myths (like 80% giving the least degradation, that below 20% is bad and that you need to drive asap after a 100% charge).
I call them myths as they are very present in forums and facebook etc. and even delivered on a silver plate by media from time to time and still no data / facts supporting them.

Does this sound optimal long term for our battery or maybe lower the limit to 70%? So that it’s more of the range of 35 to 70% charge daily? Thanks everyone!

From above you now know that if the SOC stays below 55% the battery wear less.
So reducing the time above 55% is a good idea.
If you (‘n your wife) are happy with 55% to 20-25%, this will give the lowest degradation. Below 20% is very very safe, so only range anxiety need to be adjusted for.
The other solution, if 55% doesn’t feel comfortable is to use more than 55% but to make sure to charge late, thats making sure the charging (set via scheduled charging) is finished shortly before the drive. One hour or 1.5-2h before is safe (range anxiety safe).
Many people think that the cycles cause a lot of wear. Well, they do not.
From your numbers I get it your Y is driven about 20K miles a year? That is about 75 FCE (Full Equivalent Cycles) each year.

Pictures for source below, but the end conclusion is that cycles wear very little so you should not stare blindly on that.


This is Tesla model 3 cells, cycled in small steps. 75 FCE is causing less wear than 1% a year.

Here is another test, using 50-0% (3.7-3.8V lines. 1000 FCE causes about 10% loss so 1% per 100 FCE or so.

In the end, using 55% charging level and charging late is the best option for low degradation.

This is summarized how to think:

- Do not charge more than you need (until next charge)

- Charge late (reduces mean SOC)

-Charge often (reduces the need in the first point)

In your case I would do:
-55% unless more actually is needed ( = longer drive than the daily commute).
- Set the scheduled charging to be finished one hour or two before the next days drive.

 

[SageBrush]

There so much going back and forth regarding when to charge etc.

Do you imagine that now that you have asked the same question as dozens (if not thousands) of people before you, all the answers will suddenly converge on the one TRUE answer ?

 

[SageBrush]

The other solution, if 55% doesn’t feel comfortable is to use more than 55% but to make sure to charge late, thats making sure the charging (set via scheduled charging) is finished shortly before the drive. One hour or 1.5-2h before is safe (range anxiety safe).

1+

 

[BlouieM3]

Much of the back and forth are myths, if you ask me

To begin, just following Teslas simple advice will keep your battery fine with no issues. It will not give the lowest degradation though.

You can see that calendar aging is higher above 55%. Any time above increase the degradation. To reduce degradation its good to have more time at or below 55%, than above.
Temperature also has an impact but most people can not do anything about it.
View attachment 985115

To reduce the back and forth thing, I throw in sources for my statements and and to stress that that picture above is valid (its virtually the same as a lot of other research), I add a few pictures from other research:

Cut in another way of displaying, this is actual model S cells tested in the same way (time about 6 months or so, so basically the same rate as above):
View attachment 985117

This is actual model 3 cells, only three different SOC’s but they match the first picture very well.
View attachment 985119

I guess the above is data enough to make the case. All other research reports also implies about the same thing. No single report supports the forum myths (like 80% giving the least degradation, that below 20% is bad and that you need to drive asap after a 100% charge).
I call them myths as they are very present in forums and facebook etc. and even delivered on a silver plate by media from time to time and still no data / facts supporting them.

From above you now know that if the SOC stays below 55% the battery wear less.
So reducing the time above 55% is a good idea.
If you (‘n your wife) are happy with 55% to 20-25%, this will give the lowest degradation. Below 20% is very very safe, so only range anxiety need to be adjusted for.
The other solution, if 55% doesn’t feel comfortable is to use more than 55% but to make sure to charge late, thats making sure the charging (set via scheduled charging) is finished shortly before the drive. One hour or 1.5-2h before is safe (range anxiety safe).
Many people think that the cycles cause a lot of wear. Well, they do not.
From your numbers I get it your Y is driven about 20K miles a year? That is about 75 FCE (Full Equivalent Cycles) each year.

Pictures for source below, but the end conclusion is that cycles wear very little so you should not stare blindly on that.


This is Tesla model 3 cells, cycled in small steps. 75 FCE is causing less wear than 1% a year.
View attachment 985122

Here is another test, using 50-0% (3.7-3.8V lines. 1000 FCE causes about 10% loss so 1% per 100 FCE or so.

View attachment 985123


In the end, using 55% charging level and charging late is the best option for low degradation.

This is summarized how to think:


In your case I would do:
-55% unless more actually is needed ( = longer drive than the daily commute).
- Set the scheduled charging to be finished one hour or two before the next days drive.

Thanks for the detailed responses. I’ll see if my wife doesn’t have range anxiety setting the charge limit ~55% and charging every night when she’s home (aprox 20-25%)

 

[BlouieM3]

Much of the back and forth are myths, if you ask me

To begin, just following Teslas simple advice will keep your battery fine with no issues. It will not give the lowest degradation though.

You can see that calendar aging is higher above 55%. Any time above increase the degradation. To reduce degradation its good to have more time at or below 55%, than above.
Temperature also has an impact but most people can not do anything about it.
View attachment 985115

To reduce the back and forth thing, I throw in sources for my statements and and to stress that that picture above is valid (its virtually the same as a lot of other research), I add a few pictures from other research:

Cut in another way of displaying, this is actual model S cells tested in the same way (time about 6 months or so, so basically the same rate as above):
View attachment 985117

This is actual model 3 cells, only three different SOC’s but they match the first picture very well.
View attachment 985119

I guess the above is data enough to make the case. All other research reports also implies about the same thing. No single report supports the forum myths (like 80% giving the least degradation, that below 20% is bad and that you need to drive asap after a 100% charge).
I call them myths as they are very present in forums and facebook etc. and even delivered on a silver plate by media from time to time and still no data / facts supporting them.

From above you now know that if the SOC stays below 55% the battery wear less.
So reducing the time above 55% is a good idea.
If you (‘n your wife) are happy with 55% to 20-25%, this will give the lowest degradation. Below 20% is very very safe, so only range anxiety need to be adjusted for.
The other solution, if 55% doesn’t feel comfortable is to use more than 55% but to make sure to charge late, thats making sure the charging (set via scheduled charging) is finished shortly before the drive. One hour or 1.5-2h before is safe (range anxiety safe).
Many people think that the cycles cause a lot of wear. Well, they do not.
From your numbers I get it your Y is driven about 20K miles a year? That is about 75 FCE (Full Equivalent Cycles) each year.

Pictures for source below, but the end conclusion is that cycles wear very little so you should not stare blindly on that.


This is Tesla model 3 cells, cycled in small steps. 75 FCE is causing less wear than 1% a year.
View attachment 985122

Here is another test, using 50-0% (3.7-3.8V lines. 1000 FCE causes about 10% loss so 1% per 100 FCE or so.

View attachment 985123


In the end, using 55% charging level and charging late is the best option for low degradation.

This is summarized how to think:


In your case I would do:
-55% unless more actually is needed ( = longer drive than the daily commute).
- Set the scheduled charging to be finished one hour or two before the next days drive.

 

[BlouieM3]

Approx 12-15k miles a year since she doesn’t always commute year round. So far we’ve settled at 75% limit and charges when she’s at home at around 45 to 75 limit after midnight. Gradually I’ll see if I can get it down to 55% charge limit if she’s comfortable.