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What should my ideal charge percentage be?

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Research may indicate that low SoC is better for battery in terms of capacity loss but Tesla's own battery loss is not as severe as other batteries thanks to their Battery Management System/Software.

A battery management system can not affect calendar aging, except lowering the battery temperature (which Tesla does not for obvious reasons like the energy cost etc.).

Calendar aging comes from [Time x SOC x Temperature].
It will occur even with the best BMS there is.
 
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.
 
The manufacturer (Tesla) does not recommend to charge to 90% specifically.
The slider is 50-90% and 90% is the maximum “daily” charge.

There is no Tesla recommendation to better charge to 90% than 80%.

Tesla does not use the recommendation to minimize degradation. Its most certain a combo of acceptable degradation and having a useble range.

Lowest degradation will be at low SOC, but if Tesla did recommend that we should charge to 50% or even lower they probably would get sued for selling a 300mile car that only can be driven 150miles, or less.

80-90% SOC during a lot of time will degrade the battery noticeble. 80-90% is causing about the same calendar aging as 100% SOC.

The car will (most probably) stay inside the >70% capacity after eight years anyway.

Calendar aging lessens with time and is quite small after about five years.

So using 80-90% SOC is not a problem condidering the warranty etc.

But if someone is worried about degradation, 80-90% will not cause the lowest degradation possible.

Using as low SOC as possible and charging often, preferably just before the car is to be driven could cut the degradation in half.

This means having 5% instead of 10% or 10% instead of 20% after some years.
For some it doesnt matter, for some the lesser loss of range is important.

Others can not charge at home and do not have the possibility to use low SOC or charge just before the drive. In this case, we need to accept the degradation as a normal sequence of the charging habits.
You know a lot about EV batteries, what is your background?
 
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You know a lot about EV batteries, what is your background?
Engineer education but I am a pilot. I was in an air force until this summer, retired and I fly civilian aircraft now.

The battery knowledge comes from that I started to play with RC helicopters about 2006 and I did find a lot of advice that was conflicting and/or clearly more of the rumor kind than facts.
There was a lot of research reports on the net and I started to learn a little back then.
when I ordered my first Tesla two years ago, I started looking at research reports again.
 
Engineer education but I am a pilot. I was in an air force until this summer, retired and I fly civilian aircraft now.

The battery knowledge comes from that I started to play with RC helicopters about 2006 and I did find a lot of advice that was conflicting and/or clearly more of the rumor kind than facts.
There was a lot of research reports on the net and I started to learn a little back then.
when I ordered my first Tesla two years ago, I started looking at research reports again.
Than you for that. Can you point me to a research report. I can take it from there and find other research too. Battery tech seems to be moving very fast these days. My background is also engineering. Hardware/software, retired after 30yrs supporting Marines/Navy.
 
Than you for that. Can you point me to a research report. I can take it from there and find other research too. Battery tech seems to be moving very fast these days. My background is also engineering. Hardware/software, retired after 30yrs supporting Marines/Navy.

Basically just search for calendar aging or cyclic aging. To a narrow the results closer to a US built Tesla, add “NCA” to the search. NCA has been the normal lithium battery chemistry for most Teslas.
( recent standard range might have LFP, and Europe and China built model 3/Y comes with NMC these days).

Evelina Wikner has done an excellent research suite which includes mist of what we need to know. It is presented very nice, easy to understand. She didn’t use NCA chemistry so we get the lithium battery basics but not NCA specific.

A few examples ( I have between 50 and 100 reports saved so there is a lot):

https://publications.lib.chalmers.se/records/fulltext/249356/249356.pdf

https://research.chalmers.se/publication/512004/file/512004_Fulltext.pdf

NCA-specific:

https://mdpi-res.com/d_attachment/w...e_deploy/wevj-07-00041.pdf?version=1526551363

https://www.researchgate.net/profil...oulomb-Tracking.pdf?origin=publication_detail
 
Basically just search for calendar aging or cyclic aging. To a narrow the results closer to a US built Tesla, add “NCA” to the search. NCA has been the normal lithium battery chemistry for most Teslas.
( recent standard range might have LFP, and Europe and China built model 3/Y comes with NMC these days).

Evelina Wikner has done an excellent research suite which includes mist of what we need to know. It is presented very nice, easy to understand. She didn’t use NCA chemistry so we get the lithium battery basics but not NCA specific.

A few examples ( I have between 50 and 100 reports saved so there is a lot):

https://publications.lib.chalmers.se/records/fulltext/249356/249356.pdf

https://research.chalmers.se/publication/512004/file/512004_Fulltext.pdf

NCA-specific:

https://mdpi-res.com/d_attachment/w...e_deploy/wevj-07-00041.pdf?version=1526551363

https://www.researchgate.net/profil...oulomb-Tracking.pdf?origin=publication_detail
Awesome, thank you!
 
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 started charging to 50% and using the lower bit of my pack as my daily mileage started to decline during COVID. Did this at about 175k in miles on our S.

My first 200k ended with 90.5% of my remaining charge. 2017 S 100D. I had super high mileage in those early times. Would come home at 20% sometimes after once charging during the day. Yet each night my time actually spent in the higher charge % was not very long. So yes I did charge to 90% yet I would say it never really sat which may be why I had such low degradation. I initially didn't agree with the keeping a lower charge %. Firm believer, but I will say many might not see tangible benefits. For the long term owner or those who care about where the car ends up might. Or at least understand how BMS' work.

Lucky to have a colder garage that is conditioned.

I do supercharge a healthy amount, but only on trips.

I noticed that my range rebounds on the screen much faster after charging to 50% for many times when I go back to 90% compared to my 3. I guess I am saying the the 18650's or the BMS shows quick after two or three charges the correct range. My 3 or 2170's and its BMS it takes 5 or 6 cycles to recover the shown range. I know its not gone, but it needs to figure where it is.

So I charge to 50% on both cars yet, I do calculate my driving strategies more than most. So I will slide it up or down based on a little math each night. More than 50k a year dictates such. My suggestion is to take the advice of @AAKEE. Save oneself the reading of thousands of pages of one of the most often questions asked.
 
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).
 
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).

This is excellent insight based on the research, but if someone reads this the last sentences and takes them out of context, please make sure to read the first 3 bullet points in the post as well - best to limit charging to 100% unless you need it avoid the cyclic aging if possible. But if you do happen to charge to 100%, don't worry about leaving it there a bit if you can help it. Doing so should also help the BMS top-balance the pack, too.
 
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).
These are pretty much the rules I have been living by with my S. It also helps that performance on the refreshed S at lower charge levels is still excellent or I might keep a high SOC.

My biggest issue is that Tesla sets the lower limit for charging at 50%. I could get by with 25-30% charge level most of the days just fine. Unfortunately the car charges back up to 50% if I forget to stop the charge.

Based on my experience with my Y and other TVs, I realized maximum range is a lot more important than I initially thought. By having the ability to have greater range, it meant I could more easily keep my car at a low SOC and still have enough range for daily usage. One of the worst vehicles I had for degradation was a PHEV. Not much range unless you charged it to 100% and discharged to 0 every day. That pack took a huge hit in 100k miles. I think I had something like 50% degradation so my original 30 mile range was at best 15 and that is if I didn't use AC or heat.

I also noticed that using the my 3 the same way as my Y, my degradation has been less as well. It started with better "theoretical" range but in the real world it was far better. As a result my discharge cycles are a lot less for the same usage. I can get by with a lower SOC on a daily basis and easily still have more range than the Y. The S goes another step better in that regard. I just need a way to stop the charing on all of them at about 30%.

It is also why I use the wall charger at home. I can top up more quickly just before leaving and my avg SOC is at a lower level as a result.
 
These are pretty much the rules I have been living by with my S. It also helps that performance on the refreshed S at lower charge levels is still excellent or I might keep a high SOC.

My biggest issue is that Tesla sets the lower limit for charging at 50%. I could get by with 25-30% charge level most of the days just fine. Unfortunately the car charges back up to 50% if I forget to stop the charge.
Fortunately the difference in calendar aging between 30 and 50% is not that big.
B22E3F77-B5A9-4702-8FCD-7C724C0A75BA.jpeg

Your “safe” up to about 57% ( = 55% displayed).
I use 55% as the standard charge, as I get maximum range with reasonable calendar aging.
I also charge short before driving weekdays, on weekends the car get charged at the same time but the driving mostly is later and shorter.
The average SOC for me during one year was about 35%, despite 55% charge setting.
A charge setting below 50% would of course be welcome!

Based on my experience with my Y and other TVs, I realized maximum range is a lot more important than I initially thought. By having the ability to have greater range, it meant I could more easily keep my car at a low SOC and still have enough range for daily usage. One of the worst vehicles I had for degradation was a PHEV. Not much range unless you charged it to 100% and discharged to 0 every day. That pack took a huge hit in 100k miles. I think I had something like 50% degradation so my original 30 mile range was at best 15 and that is if I didn't use AC or heat.
Yep, thats what yo expect from PHEV with small sized batteries. A hard life, always very large cycles and high C-rates. The concept is more or less built to kill the battery fast.
I also noticed that using the my 3 the same way as my Y, my degradation has been less as well. It started with better "theoretical" range but in the real world it was far better. As a result my discharge cycles are a lot less for the same usage. I can get by with a lower SOC on a daily basis and easily still have more range than the Y. The S goes another step better in that regard. I just need a way to stop the charing on all of them at about 30%.

It is also why I use the wall charger at home. I can top up more quickly just before leaving and my avg SOC is at a lower level as a result.
 
Wow this is a lot to take in. The range on my Plaid is a bit optimistic to begin with so there is no way I am going to charge only up to 50% each day since there are days I unexpectedly drive more than others.

I bought my car to drive so I don’t overanalyze it and charge to 90% each night at home. While the power is still there most of the time I can feel it decline a fair amount when my range is less than 100 miles. Because I want full power all the time there is no way I’m charging less than 90%.

I feel that a general buyer shouldn’t have to analyze this stuff so much to the point that you need a phd to make sure your battery lasts a long time.
 
I feel that a general buyer shouldn’t have to analyze this stuff so much to the point that you need a phd to make sure your battery lasts a long time.

And indeed the average buyer needs to do no such thing.

Obsessing over a few percentage points of degradation over the lifetime of the vehicle is an interesting intellectual pursuit but generally completely irrelevant to the typical owner.
 
This is excellent insight based on the research, but if someone reads this the last sentences and takes them out of context, please make sure to read the first 3 bullet points in the post as well - best to limit charging to 100% unless you need it avoid the cyclic aging if possible. But if you do happen to charge to 100%, don't worry about leaving it there a bit if you can help it. Doing so should also help the BMS top-balance the pack, too.
I’m not a native english. I do not really get the point, and I’m sure its because of me not reading my post like you do.

For 100% SOC, more or less any research report show less or the same degradation per time unit at 100% compared to 70-80-90%. So in real life we can leave it at 100% for long without any issues.

For the reports showing worse degradation at 100% its more or less at elevated temperature ( 40C or higher).
The increased rate of degradation is not high though:
04A3F846-B939-45A1-86F1-102455E57C26.jpeg


We can see that at 50C, the increased rate is very slightly increased: 9.5 months at 80% costs 11.5-12% degradation and 9.5 months at 100% costs about 12.5%.

The difference in lost capacity for leaving the battery at 80% for one year and 100% for one year is quite small, even at 50C.

One year is about 8700h, and a extended time like overnight or 10hrs will not wear noticable on the capacity.

There actually is a few research reports that shows that 100% cause less degradation than 70-80-90% for normal temperatures.
In general i try not to promote this idea.

We know the internal resistance increase more the higher the SOC is.
For a EV that is power limited by the battery power like the Tesla model 3 Performance, keeping the SOC low will slow down the reduction of power loss.

We can really leave the car for quite long time at 100% SOC without any clear disadvantage.
This is not related to the “55% SOC limit” as the car actually can be left at 100% SOC for hours without “damage”. Leave it at 70-80-90% and it will take the same “damage”.

As there is no reason to leave the car at 100% after the charging is complete, there will be no recommendation to do this*.

For me, knowing this, I do not leave the car at 100%, but I do not leave it at 70-80-90% either.

The forum rumors (not specifically SM, and not true):
- 80% is the recommended best charging target to “baby” the battery.
- Going below 20% is dangerous for the battery.
- If you need to charge to 100%, drive immediately else the battery dies.



*) I think we should try to separate “best for battery” with “BMS calibrations” as these doesnt really walk hand by hand.
 
Engineer education but I am a pilot. I was in an air force until this summer, retired and I fly civilian aircraft now.

The battery knowledge comes from that I started to play with RC helicopters about 2006 and I did find a lot of advice that was conflicting and/or clearly more of the rumor kind than facts.
There was a lot of research reports on the net and I started to learn a little back then.
when I ordered my first Tesla two years ago, I started looking at research reports again.
So what do you set for charging %? Do you plug it in every night if possible?
 
I plug in every day when home, even when not charging. I use the power from the charger to cool or heat the car before getting in rather than it drawing down from the battery.

In 8 months use and 7k miles, I've had 0.5% degradation. I also did a lot of performance testing on my S and my 0-60 times stay pretty consistent until I am pretty close to 15% SOC and less. The acceleration above 60 mph does take a bit of hit starting as early as 20% SOC. It is still by no means slow even at 15% SOC.

All in all a lower SOC works well for me. I live in a very hot climate with temps often over 100F. So I am doing all I can to offset the environmental impact.