Weird message came up suggesting I change the charge limit to 71%?

[RJUK]

Hi folks, I set my 2019 Model 3 Performance to charge last night and set the limit to 83% (I do this, as I use 3% getting to work the next morning, which then leaves the car at 80% for the day). However, the charge is also controlled by my electricity provider to get the car to charge at the best times for the grid, and I can only set the limit in 5% increments on that app, so I set it to 85%.

The car then stops the charge at 83% and the electricity provider stop is just used as a back up. My car was at 82% when I got in this morning and always varies by a few percent, usually depending on temperature.

Anyway, this morning (for the first time) I get in the car to find a message in the middle of the screen saying something along the lines of "Single charge limit not reached, we suggest setting the limit to 71% for daily driving." Below which there was a button to ignore that and another to set the charge limit to 71%.

Has anyone else ever seen this?

I thought the general rule of thumb was to keep it below 80% as much as possible and only charge above that for longer trips. Now they seem to be suggesting keeping it below the very arbitrary number of 71%...

Why 71%?!

I also wonder if I'm the only one seeing this, or if others are also having the same 71% suggested to them by their cars. And if anyone has any idea why? Like, has Tesla looked into the battery statistics of Tesla cars and decided that charging to 71% is optimal for battery life?

 

[fhteagle]

Haven't seen that before, 2023 MYLR.

I do remember a video with Jeff Dahn talking about high nickel chemistries having a voltage plateau and oxygen dissolution stage when charging through ~70% SOC. If legit and but just a random coding bug, maybe it has something to do with that.

 

[jjrandorin]

Hi folks, I set my 2019 Model 3 Performance to charge last night and set the limit to 83% (I do this, as I use 3% getting to work the next morning, which then leaves the car at 80% for the day). However, the charge is also controlled by my electricity provider to get the car to charge at the best times for the grid, and I can only set the limit in 5% increments on that app, so I set it to 85%.

The car then stops the charge at 83% and the electricity provider stop is just used as a back up. My car was at 82% when I got in this morning and always varies by a few percent, usually depending on temperature.

Anyway, this morning (for the first time) I get in the car to find a message in the middle of the screen saying something along the lines of "Single charge limit not reached, we suggest setting the limit to 71% for daily driving." Below which there was a button to ignore that and another to set the charge limit to 71%.

Has anyone else ever seen this?

I thought the general rule of thumb was to keep it below 80% as much as possible and only charge above that for longer trips. Now they seem to be suggesting keeping it below the very arbitrary number of 71%...

Why 71%?!

I also wonder if I'm the only one seeing this, or if others are also having the same 71% suggested to them by their cars. And if anyone has any idea why? Like, has Tesla looked into the battery statistics of Tesla cars and decided that charging to 71% is optimal for battery life?

Havent seen that number reported before, but you have wayy more charging shenanigans going on than most people. Too many cooks in the kitchen, as it were, as it relates to your charging.

 

[Kohan]

Hi folks, I set my 2019 Model 3 Performance to charge last night and set the limit to 83% (I do this, as I use 3% getting to work the next morning, which then leaves the car at 80% for the day). However, the charge is also controlled by my electricity provider to get the car to charge at the best times for the grid, and I can only set the limit in 5% increments on that app, so I set it to 85%.

The car then stops the charge at 83% and the electricity provider stop is just used as a back up. My car was at 82% when I got in this morning and always varies by a few percent, usually depending on temperature.

Anyway, this morning (for the first time) I get in the car to find a message in the middle of the screen saying something along the lines of "Single charge limit not reached, we suggest setting the limit to 71% for daily driving." Below which there was a button to ignore that and another to set the charge limit to 71%.

Has anyone else ever seen this?

I thought the general rule of thumb was to keep it below 80% as much as possible and only charge above that for longer trips. Now they seem to be suggesting keeping it below the very arbitrary number of 71%...

Why 71%?!

I also wonder if I'm the only one seeing this, or if others are also having the same 71% suggested to them by their cars. And if anyone has any idea why? Like, has Tesla looked into the battery statistics of Tesla cars and decided that charging to 71% is optimal for battery life?

Tesla is known for being cryptic perhaps this is telling you current degradation?

 

[RJUK]

Havent seen that number reported before, but you have wayy more charging shenanigans going on than most people. Too many cooks in the kitchen, as it were, as it relates to your charging.

I dunno. I just have the vehicle charge limit and a charge limit that I set on my energy company app. That's only 2 things.

Doesn't really explain the whole 71% suggestion though.

I'll get a photo of the message next time.

 

[RJUK]

Tesla is known for being cryptic perhaps this is telling you current degradation?

I doubt it. The car only has 24,000 miles on it and has never been charged to 100% or discharged particularly low. It mostly gets charged once a week and used between 83% to 50% with mostly 7kw charging and very little fast charging no higher than 50kw, so to have almost 30% degradation seems unlikely.

It was just sort of recommending that I set my daily charge limit to 71%... Which seems bizarre.

 

[3sr+buyer]

If you believe @AAKEE posts, it may be best in terms of minimizing battery degradation to keep the state-of-charge below 55% most of the time for NCA batteries (70% for LFP batteries), unless you need more than that for driving before you charge again (or approximately weekly to 100% to keep the BMS in sync for LFP batteries).

 

[jjrandorin]

I dunno. I just have the vehicle charge limit and a charge limit that I set on my energy company app. That's only 2 things.

Doesn't really explain the whole 71% suggestion though.

I'll get a photo of the message next time.

You have 2 different, completely separate things that can and will control charging, that dont work together. We dont even know which one of those things is generating this message you saw.

 

[AAKEE]

Why 71%?!

This is most certainly a funktion of the single charge setting.
If you normally use 71% and you set 100%, the car asks if only use this higher setting only once and return to the usual setting.
(This is a funktion that came with one of the latest updates.).
It might ask for settings above 80%.

That 71% has nothing to do with battery degradation and is not any kind of sweet spot. This we know for sure!
(Lets hope this doesnt evolve to a new myth )

This behaviour should probably be connected to the below, or a bug connected to it.

 

[RJUK]

This is most certainly a funktion of the single charge setting.
If you normally use 71% and you set 100%, the car asks if only use this higher setting only once and return to the usual setting.
(This is a funktion that came with one of the latest updates.).
It might ask for settings above 80%.

That 71% has nothing to do with battery degradation and is not any kind of sweet spot. This we know for sure!
(Lets hope this doesnt evolve to a new myth )

This behaviour should probably be connected to the below, or a bug connected to it.

View attachment 1036804

Yes, I think this is the right answer. The wording was along the lines of a single charge limit.

The only thing being that I didn't increase the limit any more than I usually do and I never set the limit to 71%. I suppose though, as it's a new function and my charge limit was set above 80%, that it could have just made some assumptions that I had set my limit high for a trip and picked a random number below 80% to suggest as my daily limit.

As for only charging the car to 55% for daily use, that would see me having to charge the car multiple times per week or deep discharging it down to around 20%.

If I charge to 83% then I usually end the week on around 50% and the car sits over the weekend on 50% until I charge it for the next week.

Another part of the reason I charge it to just over 80% is that I once read that performance really starts dropping off below 80%. So it seems silly to permanently run my car below the percentage that gives me optimal power.

It's a shame that batteries are so picky like this. It would be much better if they could be charged to 100% with no harm done and then deep discharged with no issues, so that you could use the full battery without worry.

 

[RJUK]

Aakee, what's your background in batteries then and what do you recommend for optimal battery life? I always try to look after the batteries in all my lithium powered devices as much as I can, but is charging to 83% really going to be detrimental over time?

It's that catch 22 between charging the car as much as possible to get the best performance from it and hurting the battery. My car lives mostly between 50% and 83% and only tends to get charged one per week. I'd hope my battery condition would be pretty good because I never charge to 100% and rarely fast charge.

 

[jjrandorin]

I know I am not @AAKEE , but in answer to their background and what they recommend, I will just say that @AAKEE has put in considerable effort here on TMC related to battery charging, health, maintenance etc, along with plenty of data and charts. When I am looking for info on the topic here, I search out posts made by @AAKEE to show to interested people on the topic.

You could search TMC for posts by them (@AAKEE ) and come away with quite a lot of explanation and data.

Since they will likely not say all that about themselves, I thought I would say it for them. They are one of the few sources here where I go when looking for this information on batteries, etc.

 

[AAKEE]

Aakee, what's your background in batteries then and what do you recommend for optimal battery life? I always try to look after the batteries in all my lithium powered devices as much as I can, but is charging to 83% really going to be detrimental over time?

It's that catch 22 between charging the car as much as possible to get the best performance from it and hurting the battery. My car lives mostly between 50% and 83% and only tends to get charged one per week. I'd hope my battery condition would be pretty good because I never charge to 100% and rarely fast charge.

You know, Tesla revently lowered the ”daily” from ”below 90” to ”80 or below”
Below 90 worked okey, right?

The upper daily limit is mostly there to make sure the cycles arent too big. If they used 100%, some people would charge to 100% daily and then not charge until it was very low - making the cycles large. Large cycles wear more, by principle.
Also, the upper limit limits the calendar aging in places which are really hot. At normal ambient it doesnt matter very much.

So, doin 83% daily will not be a problem.

If you like to minimize degradation, just read my other posts. Most discussions are about trying to reduce degradation and also what actually causes the lowest degradation.

If you like to stick with 83%, I mean like having a Performance but not getting the performance you bought otherwise - one trick is to charge late. Do not start the charging at arrival after work. Set it to commence to be ready shortly before the next days drive. Preferably charge with as high power as. Possible when charging home/AC.
That will shorten the time with high SOC - effectively reducing the calendar aging.
But it also will result in a warmer battery = more power. I use that trick, and and it works fine for the power as well.(but it charge less and still did get good power in my M3P).

Most people believe the cycles causes the main part of the wear. But it is calendar aging for the first 5-8 years or so (except driving a lot and using 100-0 cycles). So shortening the time at high SOC will do it in your case.

 

[RJUK]

OK thanks for that. I'll dig out your other posts.

I think I generally have the idea on lithium batteries for best practice, but I'm always open to learning more.

My car is a 2019 and is leased, due to go back at the end of this year (I extended the lease twice already).

Most would say "it's a lease, just charge it to 100%, it's not your problem", but I'm too mechanically sympathetic and don't believe in purposely abusing something just for the sake of it. If everyone has that selfish attitude then it means the future pool of used EVs will have more degraded batteries than it otherwise could have.

I know better and I know how to look after the battery, so why not?

What's the best SOC to leave the car (or any lithium battery) at then? Is it 50%, as this sort of represents an "equilibrium" in the battery, or is it around 30 - 40% (which is what I heard that they tend to store lithium batteries at)?

 

[AAKEE]

OK thanks for that. I'll dig out your other posts.

I think I generally have the idea on lithium batteries for best practice, but I'm always open to learning more.

My car is a 2019 and is leased, due to go back at the end of this year (I extended the lease twice already).

Most would say "it's a lease, just charge it to 100%, it's not your problem", but I'm too mechanically sympathetic and don't believe in purposely abusing something just for the sake of it. If everyone has that selfish attitude then it means the future pool of used EVs will have more degraded batteries than it otherwise could have.

I know better and I know how to look after the battery, so why not?

What's the best SOC to leave the car (or any lithium battery) at then? Is it 50%, as this sort of represents an "equilibrium" in the battery, or is it around 30 - 40% (which is what I heard that they tend to store lithium batteries at)?

For the calendar aging, the lower SOC the better (all the way to 0%). There’s a sharp twist for NCA (you have) chemistry at 57% real SOC, which means 55% displayed.
Calendar aging is = Time x SOC x temperature.
Reducing time above 55% displayed is the absolute best way to reduce the degradation.
Calendar aging reduces the rate with time and after 5 years like yours the rate is not that fast. Anyway, SOC below 55% reduces the rate.

Cyclic aging is generally lower with small cycles. Charge often (daily) is good.

100% is not as bad as people think.

Tesla model 3 cells cycled:

Same cells, but split into 10% cycles:
At a first glande 5-15% might look bad, but if you dig into it, they loose 20% after >3500 Full Equivalent Cycles which covers 875K miles or 1.4M km in a LR Tesla. Thats more than enough for 70 years of driving so this is very low degradation per year.

5% true SOC is ~ 0.5% displayed in a Tesla so the 5-15% is actually ~0-10% displayed.

 

[RJUK]

Wow, that's a lot of data. So am I right in reading that as saying keeping it between 45 - 55% and charging daily would provide the best longevity for the battery?

Obviously that's not particularly possible unless you always do short trips and don't mind the hassle of plugging the car in every night to keep it within that range.

Also, I guess the storage graph, whilst providing a good general guide, isn't exactly attributable to a car in use, as the car will likely go through many cycles in 10 months and isn't actually being stored.

It seems strange that there's such a dip after 55% though, but then it seems like once you're going over 55% there's not much difference between 60% and 80% so if you go over 55 you might as well go to 80% or so.

 

[AAKEE]

Wow, that's a lot of data. So am I right in reading that as saying keeping it between 45 - 55% and charging daily would provide the best longevity for the battery?

As cycles wear much much less than calendar aging, charging to 50% (max 55%) any day when 50-55% will take you all the way home. That is, even down to 0%.

When more is needed, charge only the amount needed (plus a margin to keep range anxiety at distance) and charge late, so the time at higher SOC is short.

Obviously that's not particularly possible unless you always do short trips and don't mind the hassle of plugging the car in every night to keep it within that range.

As even down to 0% is good, there is not that bad range at 55%.
Calendar aging has about the same rate at 30-55%, so thats the reason I charge to 55%. The last 5% is free, it do not come with more degradation.
Also, 50% is the lowest charge setting and the calendar aging is about the same down to about 30% so there is no need to try to charge even lower.

Also, I guess the storage graph, whilst providing a good general guide, isn't exactly attributable to a car in use, as the car will likely go through many cycles in 10 months and isn't actually being stored.

”Storage” is time when not used.
The battery doesnt know if it is stored or just parked so these graphs are actually spot on.
Most people only drive for ~ 1 hour a day, or maybe two and charge for 2-5hours.

Thats 18-21 hours a day of ”storage” for most people.

Try to think like this:

Degradation is split into two types:
-cyclic aging = charging/driving
-calendar aging = all other times.

In reality, calendar aging does happen when cycling it as well, but for the sake of the tests they split it.

It seems strange that there's such a dip after 55% though, but then it seems like once you're going over 55% there's not much difference between 60% and 80% so if you go over 55 you might as well go to 80% or so.

First thing we need to do is to let go of the myths.
Second thing, to accept how these batteries work.
If you like a easier peak into this:
Differential voltage

 

[RJUK]

Interesting. I thought it was detrimental to deep discharge the battery, but you think it's OK? I thought it was recommended to keep it above 20%? The graphs from earlier as well suggested that using it at a lower SOC was more detrimental than using it at higher SOCs?

Or is it just that calendar ageing at higher SOC'Ss offsets this? (I'd have thought that calendar ageing would be taken into account with both tests as its not possible to "pause" calendar ageing to test ageing from cycles.

 

[AAKEE]

Interesting. I thought it was detrimental to deep discharge the battery, but you think it's OK?

Deep discharge is a term not really relevant to lithium ion batteries.
Lead Acid batteries do not like deep discharge, but this is not lead acid.
Its not how low you go with lithium ion, its the size of the cycle.

I thought it was recommended to keep it above 20%? The graphs from earlier as well suggested that using it at a lower SOC was more detrimental than using it at higher SOCs?

I think I wrote that even doing the 5-15% (the same as 0-10% on the display) cycles that *looks* bad, causes only a fraction of the degradation from calendar aging? They might look bad but they really are not.
Instead, if the battery is mainly kept there (low) the calendar aging is reduced several times more than the difference between the best SOC-range in the picture and 5-15%.

Remember this: cyclic aging is not going to cause much degradation anyway, so you can gorget about that and solely focus on calendar aging. (Which in turn is not in opposite relationship to cyclic aging.)

Or is it just that calendar ageing at higher SOC'Ss offsets this? (I'd have thought that calendar ageing would be taken into account with both tests as its not possible to "pause" calendar ageing to test ageing from cycles.

All cyclic aging tests also incorporate a part of calendar aging. The larger cycles count might take 6-12 months so this vill be a part of it.
They often /sometimes throw in the calendar aging in the same graphs to show the real part that cycling took

 

[geofox784]

Aakee, I’m a little confused by your graphs and conclusions. According to the first graph, it looks like keeping the battery below 55% helps with calendar aging.

But the second graph seems to show that cycling 50% to 100% kept the most battery health when compared to 0% to 50%.

The 3rd graph shows that cycling 5% to 15% did much worse than cycling 85% to 95%, which goes against the conclusion that lowest SOC is best above all.

Maybe I am interpreting the graphs wrong, but according to graphs 2 and 3 it looks like cycling at the high range is better than a low range, but that goes against the first graph and the conclusion that you want to keep the SOC low to prevent calender aging.

For reference, I typically use 30% during my commute. I’m trying to figure out if I should:

Cycle 25% to 55% (keeps battery below that 55% “cliff” in graph one)

Cycle 35% to 65% (keeps median SOC around 50%, which seems to do best in graph 3, but goes over the 55% “cliff” that also seems to cause a penalty in graph 3 in the 55-65 result vs the 25-35 result).

Regardless, I will definitely start using the departure scheduling.