What should my ideal charge percentage be?

[FixUntilBroke]

Lots of good info in this thread and a sincere thanks to everyone who have contributed!

This video seems to summarize it similarly...some may find it helpful vs reading all 1300+ posts

 

[AAKEE]

I saw that one study about people who fast charge 90% of the time had almost no difference in degradation than those that did 10% fast charging. Does that line up with what you've read?

Tests in research do not show the same thing. Fast charging degrades the battery faster. In these tests, the mostly do not heat the batteries before the charging session.

There are a few things to consider:
-Preconditioning the battery reduces lithium plating which is the main issue with fast charging.

-Periods of slow charging and smaller cycles can actually restore capacity in a battery. Some part of the lithium plating can be reverted to cyclable lithium by slow charging ( = AC-charging).
So supercharging every now and then but not all the time might make the extra degradation from supercharging almost negligible.

-Constantly supercharging would eventually cause shorts in the cells, causing them to die. You probably need to do much supercharging specially if you always use preconditioning. But if you do it often enough and enough times, it will happen after (probably) quite lobg time.

I have free supercharging on the new car and there are so many more superchargers than before (and car charges incredibly quick compared to 2012 version) so might take advantage of it more.

I have 3 yrs of free SuC on my MSP. I still only use it as with the last Tesla I had = when needed and on a longer trip. I do not use it at home to save money.

I'm still stopping charging at 55% so my stops are only about 5-8 minutes which is amazing. I can't believe how quick it is. 27-55% in 8 minutes.

If you are to drive after the charge, there is not really a reason to stop at 55%.
(Well, it is not bad to stop at 55%, but the real reduction in calendar aging comes from the time above 55%, so you can charge higher and if you still park at or below 55%, youre fine.

I charged my Plaid to 100% today for about the 10th time since I got it 7 months ago.
Still very low degradation due to it mostly being parked at 55% or below. (I arrived at 40%, and just was on a shorter drive so no it is parked at ~ 37% or so.)
No danger to use 100%

 

[dsm363]

Tests in research do not show the same thing. Fast charging degrades the battery faster. In these tests, the mostly do not heat the batteries before the charging session.

There are a few things to consider:
-Preconditioning the battery reduces lithium plating which is the main issue with fast charging.

-Periods of slow charging and smaller cycles can actually restore capacity in a battery. Some part of the lithium plating can be reverted to cyclable lithium by slow charging ( = AC-charging).
So supercharging every now and then but not all the time might make the extra degradation from supercharging almost negligible.

-Constantly supercharging would eventually cause shorts in the cells, causing them to die. You probably need to do much supercharging specially if you always use preconditioning. But if you do it often enough and enough times, it will happen after (probably) quite lobg time.

I have 3 yrs of free SuC on my MSP. I still only use it as with the last Tesla I had = when needed and on a longer trip. I do not use it at home to save money.

If you are to drive after the charge, there is not really a reason to stop at 55%.
(Well, it is not bad to stop at 55%, but the real reduction in calendar aging comes from the time above 55%, so you can charge higher and if you still park at or below 55%, youre fine.

I charged my Plaid to 100% today for about the 10th time since I got it 7 months ago.
Still very low degradation due to it mostly being parked at 55% or below. (I arrived at 40%, and just was on a shorter drive so no it is parked at ~ 37% or so.)
No danger to use 100%

I've been charging little more from 45-55% on my way home from work a bit more. I used to only Supercharge on trips as well.
So I might have a bit more degradation I guess. Just wanted to make sure it wasn't going to be horrible. But I'll try and charge more at home like I did the prior 12 years.

I do navigate to the Supercharger so it is preconditioning the pack. Thanks.

 

[asterothe]

Tests in research do not show the same thing. Fast charging degrades the battery faster. In these tests, the mostly do not heat the batteries before the charging session.

There are a few things to consider:
-Preconditioning the battery reduces lithium plating which is the main issue with fast charging.

-Periods of slow charging and smaller cycles can actually restore capacity in a battery. Some part of the lithium plating can be reverted to cyclable lithium by slow charging ( = AC-charging).
So supercharging every now and then but not all the time might make the extra degradation from supercharging almost negligible.

-Constantly supercharging would eventually cause shorts in the cells, causing them to die. You probably need to do much supercharging specially if you always use preconditioning. But if you do it often enough and enough times, it will happen after (probably) quite lobg time.

I have 3 yrs of free SuC on my MSP. I still only use it as with the last Tesla I had = when needed and on a longer trip. I do not use it at home to save money.

If you are to drive after the charge, there is not really a reason to stop at 55%.
(Well, it is not bad to stop at 55%, but the real reduction in calendar aging comes from the time above 55%, so you can charge higher and if you still park at or below 55%, youre fine.

I charged my Plaid to 100% today for about the 10th time since I got it 7 months ago.
Still very low degradation due to it mostly being parked at 55% or below. (I arrived at 40%, and just was on a shorter drive so no it is parked at ~ 37% or so.)
No danger to use 100%

I am not charging to 100% at all. I have this new car for 6 months and only doing 55% like you said. Every other day so it goes between 55% to 20%. Is that enough? I’d charge higher for longer trips but did not need to do so far.

 

[dsm363]

I am not charging to 100% at all. I have this new car for 6 months and only doing 55% like you said. Every other day so it goes between 55% to 20%. Is that enough? I’d charge higher for longer trips but did not need to do so far.

From what I understand from his post is plug in every night. It’s fine. Charge to 55% only if it gives you enough range at the end of the day. If you need to charge to 65% every day to make car work, do that. Will age battery slightly faster but not the end of the world. I charged my old Model S to 90% for I think 5 years and 80% for 6 years. Car was fine for daily driving. We know more now than when I got my old Model S. With this new one, I’m trying the 55% and it’s been going ok for day to day.

 

[FSDIN2020!]

This thread is interesting. 2 years ago I picked up my MXP in February, then in March went on a 2 week vacation. I set the charge level to 60% but I think it was around 80% when I parked it, it could have even been 90. When I got back and charged to 90% the displayed miles were 264, it used to be 277. This amounted to about 6-7% reduction in max range. I tried recalibrating the battery and even used the Tesla service mode to test the battery and the range remained the same. Now I’m at between 8-9% reduction after 2 years and 18k miles. I have only supercharged 2-3 times, the rest was on my wall connector at home.

If we eliminated the initial 7% loss in range, the 1-2% over two years at low miles makes sense. Is the consensus here that I hurt my range by leaving it stored at the higher soc? Do you think I had a couple bad cells? Thoughts? Thanks!

My 2018 model x held its range pretty good before I upgraded (I don’t have stats because I wasn’t worried about it). Back in the day Elon recommended charging to 90% and we did that with our 2018 X and 2020 model 3 and the 3 is showing 10% reduction in displayed range. These days I charge the plaid to 80 as the daily driver and we only plug in the 3 at around 50% and charge to 80%.

Am I still doing it wrong?

 

[AAKEE]

This thread is interesting. 2 years ago I picked up my MXP in February, then in March went on a 2 week vacation. I set the charge level to 60% but I think it was around 80% when I parked it, it could have even been 90. When I got back and charged to 90% the displayed miles were 264, it used to be 277. This amounted to about 6-7% reduction in max range. I tried recalibrating the battery and even used the Tesla service mode to test the battery and the range remained the same.

I guess it was not too warm in that march whne you left the car?

The calendar aging thing is reducing the rate with the square root of time. This means that it happens very much in short time the first months but the rate lessens quite fast.


This is research on a similar cell (Panasonic NCR18650, with the same chemistry).
You can see that you would loose about 2.5% capacity after 2.1 months at 25C. You also see that from 70 to 100% there is no big changes in the rate of calendar aging.
Two weeks parked at 80 or 90% doesnt change anything really from the most common way to use a EV.
You would get a noticeble difference beeing at or below 55% though.

I would say your range loss was not caused by that. If the car was about 2 months, the total capacity loss would probably be around 2.5%
The MSP doesnt loose range until about 96.2 kWh capacity and the initial capacity is about 99.4kWh so you should not have been even below the point where the range start to reduce. Not charging full and looking at the range might induce rounding errors etc so thats not very exact in this case.

But my MSP started slightly below 96kWh and increased the range/capacity during 1-1.5months until it reached the maximum capacity, 98.4kWh. Still after about 10 months from manufacture date the range is at maximum,and the capacity is at 97.4-97.5 kWh.

Now I’m at between 8-9% reduction after 2 years and 18k miles. I have only supercharged 2-3 times, the rest was on my wall connector at home.

If we eliminated the initial 7% loss in range, the 1-2% over two years at low miles makes sense. Is the consensus here that I hurt my range by leaving it stored at the higher soc? Do you think I had a couple bad cells? Thoughts? Thanks!

My 2018 model x held its range pretty good before I upgraded (I don’t have stats because I wasn’t worried about it). Back in the day Elon recommended charging to 90% and we did that with our 2018 X and 2020 model 3 and the 3 is showing 10% reduction in displayed range. These days I charge the plaid to 80 as the daily driver and we only plug in the 3 at around 50% and charge to 80%.

Am I still doing it wrong?

 

[FSDIN2020!]

So if I understand correctly. The calendar aging would have occurred even if I was driving.

In hindsight I should set the charge to 50% to reduce the impact, especially in the first few months of ownership.

This helps because I have a msp on order and my commute is fairly short so keeping my soc around 50%-55% won’t be a problem.

Thanks for your response!

 

[AAKEE]

So if I understand correctly. The calendar aging would have occurred even if I was driving.

Calendar aging is defined as the degradation during non operating periods.
In reality they age all the time but for research purpose its said to happen when not used (to split from when they’re cycled)
The aging process from calendar aging doesnt stop when you drive or charge the car.
(Most owners do not drive much more than one hour a day, and the time for charging might be two to five or so?
That still leaves the car unused at 75-90% percent of each day. So during that time the cells aren’t cycled and per definition ”in calendar aging”.)

In hindsight I should set the charge to 50% to reduce the impact, especially in the first few months of ownership.

Calendar aging reduces the rate due to that the Solid Electrolyte Interphase (SEI) grows in thickness.
The SEI is also the thing reducingnthe capacity by stealing cycleble lithium.

So by loosing capacity to SEI the battery get protection from SEI.

—> which means that if you use low SOC for a short time in the beginning the calendar aging is low, but the protecting SEI does form slower.
So if you start to leave the car at high SOC after a few months the rate is probably higher until the degradation happened and the SEI is there.

So I would recommend continuing to not
Use higher SOC than needed and charge late.
(using 55% or less cut the calendar aging in ~half so you can charge up to 55% and leave it, still with low calendar aging)

This helps because I have a msp on order and my commute is fairly short so keeping my soc around 50%-55% won’t be a problem.

That’ll do it!

 

[FSDIN2020!]

Great clarification, thank you.