Favor Low SoC or Small Cycles?

[Drinyth]

A sudden drop of the hat emergency with zero warning that not only requires you to drive 150+ miles away, but also you can’t stop at all even for ~15 mins to top up at a supercharger (likely also while eating or using the restroom).

Maybe a situation where someone is a secondary care giver to someone with unstable health issues? Or where you may be responsible for providing care to an elderly relative in case of an emergency? And maybe that person lives in a small town 75+ miles away where you can't conveniently charge to get back home?

I don't know. I'm just spitballing here. But I don't doubt that there is a valid scenario that exists. And even if it didn't, if someone really had range anxiety over not being able to travel more than 150+ miles without causing them stress, I'd say go ahead and just charge to whatever makes you feel comfortable. While I do believe that higher SoC causes increased battery degradation, I wouldn't want anyone to suffer or lose sleep over not having enough range if it was really making them worry.

I'm sure there is someone out there with range anxiety that needs to charge to 90% to balance out those people with battery degradation anxiety that has them capping their charges to 50%.

 

[STS-134]

I don't know. I'm just spitballing here. But I don't doubt that there is a valid scenario that exists. And even if it didn't, if someone really had range anxiety over not being able to travel more than 150+ miles without causing them stress, I'd say go ahead and just charge to whatever makes you feel comfortable. While I do believe that higher SoC causes increased battery degradation, I wouldn't want anyone to suffer or lose sleep over not having enough range if it was really making them worry.

For those people, there are ICE vehicles. In fact, I have a PHEV, and if I am ever in that type of situation, I'd probably leave the Tesla at home and take the PHEV, just so I don't have to worry about where to charge at all.

 

[AAKEE]

if the pack is in a car used regularly it does not mean optimum life is achieved in the storage batery number range.
Thats all I am saying.

It is you against all researchers that really did test this with real batteries.

The research is quite conclusive that:
- The use of low SOC reduces the calendar aging.
- The use of small cycles reduce cyclic aging
- The use of low SOC range during cycles reduce cyclic aging.

-Calendar aging is less at lower temperature. This might not be possible to affect for most people.
-Cyclic aging is least at about 25-30C or so.

Charging not higher than what we need until the next charging session reduce degradation.
Charging shortly before departure reduce degradation.
Charge often, daily for most people and maybe at work in the middle of the day to lower the average SOC and reduce cycle size reduce degradation.

 

[RedY23]

It is you against all researchers that really did test this with real batteries.

The research is quite conclusive that:
- The use of low SOC reduces the calendar aging.
- The use of small cycles reduce cyclic aging
- The use of low SOC range during cycles reduce cyclic aging.

-Calendar aging is less at lower temperature. This might not be possible to affect for most people.
-Cyclic aging is least at about 25-30C or so.

Charging not higher than what we need until the next charging session reduce degradation.
Charging shortly before departure reduce degradation.
Charge often, daily for most people and maybe at work in the middle of the day to lower the average SOC and reduce cycle size reduce degradation.

Do you happen to be a Tesla Engineer with Tesla Test data? Show me the Tesla Research you are quoting! OW you are just another “oppinion” on a forum.
Putting up a number from tesla for “Storage Battery Charge Reccomendation” does not reflect best use and life of battery on a Tesla, is all I am saying.

 

[STS-134]

Do you happen to be a Tesla Engineer with Tesla Test data? Show me the Tesla Research you are quoting! OW you are just another “oppinion” on a forum.
Putting up a number from tesla for “Storage Battery Charge Reccomendation” does not reflect best use and life of battery on a Tesla, is all I am saying.

Batteries with the same chemistry are going to behave the same under the same conditions. They don't care whether they're in a Tesla, a Powerwall, a PG&E storage site, a cell phone, a toy, etc.

And then you go around misquoting what Tesla says:

I think the only people that know the answer to the question topic here are tesla engineers. AND DRUMROLL.....the TESLA Engineers recommend to

...
2. Keep the car charged at 90% for daily use and 100 for long trips.
...

Tesla never said to "keep the car charged at 90% for daily use".

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

What percentage should I charge the battery to?
For regular use, we recommend keeping your car set within the 'Daily' range bracket, up to approximately 90%. Charging up to 100% is best saved for when you are preparing for a longer trip. You can adjust how full the battery charges from the charge settings menu.

Within the 'Daily' range bracket is between 50% and 90%. "Up to" means "at most". "<=" does not mean "==".

 

[E90alex]

Do you happen to be a Tesla Engineer with Tesla Test data? Show me the Tesla Research you are quoting! OW you are just another “oppinion” on a forum.
Putting up a number from tesla for “Storage Battery Charge Reccomendation” does not reflect best use and life of battery on a Tesla, is all I am saying.

Unlike what Elon would like to have people believe, Tesla cannot defy the laws of physics and chemistry. The studies quoted are true for all lithium ion batteries.

 

[AAKEE]

Do you happen to be a Tesla Engineer with Tesla Test data? Show me the Tesla Research you are quoting!

I’m not quoting any Tesla research. They ate not that open with the findings

OW you are just another “oppinion” on a forum.

Yes, I am.

I have built my knowledge about lithium batteries by reading research reports since about 2007.
Since about three year back I’ve looked specifically after research on lithium ion batteries in general and Panasonic NCA specifically.
I have read more than 100 research reports during the ladt three years.

The science/research show us how the batteries really work and the factors that affect the degradation.

Putting up a number from tesla for “Storage Battery Charge Reccomendation” does not reflect best use and life of battery on a Tesla, is all I am saying.

You clearly lack knowledge in this area and that statement is a pure guess, which in this this case the guess was wrong.

You would need to read this thread over again, as the last picture only was an add on to the earlier posts.
Did you see the note about Tesla actually stating ”To maximize battery longevity, only charge to the level needed” ?

This is from real research about Panasonic NCA cells, after five months:

This is another one, covering NCA, NMC and LFP:

Below, 2170 NCA (they did not reveal the brand/vendor)

I also have bought 35 Panasonic NCA cells that I keep at different SOC, since a little over one year back.
What Ive seen is in line with these charts.
80% is not very good if low decradation is the goal.
100% is not that bad as people think.

20-30% even did gain capacity after 6 months.

 

[RedY23]

I’m not quoting any Tesla research. They ate not that open with the findings

Yes, I am.

I have built my knowledge about lithium batteries by reading research reports since about 2007.
Since about three year back I’ve looked specifically after research on lithium ion batteries in general and Panasonic NCA specifically.
I have read more than 100 research reports during the ladt three years.

The science/research show us how the batteries really work and the factors that affect the degradation.

You clearly lack knowledge in this area and that statement is a pure guess, which in this this case the guess was wrong.

You would need to read this thread over again, as the last picture only was an add on to the earlier posts.
Did you see the note about Tesla actually stating ”To maximize battery longevity, only charge to the level needed” ?
View attachment 914130


This is from real research about Panasonic NCA cells, after five months:
View attachment 914131

This is another one, covering NCA, NMC and LFP:
View attachment 914133
Below, 2170 NCA (they did not reveal the brand/vendor)
View attachment 914134

View attachment 914135

I also have bought 35 Panasonic NCA cells that I keep at different SOC, since a little over one year back.
What Ive seen is in line with these charts.
80% is not very good if low decradation is the goal.
100% is not that bad as people think.

20-30% even did gain capacity after 6 months.

And that is what I like to see. I appreciate a well informed response. Ill take a look and educate myself. Thank you for taking the time to respond. So bottom line if i only ise 40/60% of the battery on a regular basis I am best off keeping it at 80% drawing down to 20/30% and have a little to spare?

 

[AAKEE]

And that is what I like to see. I appreciate a well informed response. Ill take a look and educate myself. Thank you for taking the time to respond. So bottom line if i only ise 40/60% of the battery on a regular basis I am best off keeping it at 80% drawing down to 20/30% and have a little to spare?

Using 80% SOC target is not giving you the lovest degradation (but it wont ruin the battery either).
If you like to have 20-30% spare and use 40-60% you end up in needeing 80% or so.

Of you need to charge to 80% and would like to reduce the calendar aging, charging late is a good option. As calendar aging is dependent on SOC x TEMP x Time, if you set the charge so it is finished shortly before the drive, the calendar aging will be low (meaning you have 20-30% in the end of the day and the car sleeps with low SOC during the night).

There is no danger going below 20%, that is a forum myth. So the lower limit is only set by your own preferences like ”reserve for unplanned drives” and to not get range anxiety.

These cycles where all run down to 0% SOC, (2.5V end of discharge).
The 0.5 and 0.7A (on a 2.8Ah cell) does best match normal car usage for driving, most people charge slower but it would not really make a difference.
100-0% (4.2-2.5V) got 650 cycles to 80% capacity. Thats about 270K km.
4.1-2.5V / About 90-0% got about 800 FCE cycles, thats about 320K km.
4.0-2.5V /about 80-0% got about 1000FCE, thats about 400K km. Also about 1250 single cycles (1000/0.8) discharged to 0% every time. Discharging to 0% is not bad.
A Tesla still have 4.5% remaining ehen the display says 0%, so we have extra safety.

Source for this picture:
Edit: new link

This is a very good research report, covering a lot of the things. Not too hard to ubderstand, and mostly graphs that a non researcher could understand without too much issues.

 

[STS-134]

And that is what I like to see. I appreciate a well informed response. Ill take a look and educate myself. Thank you for taking the time to respond. So bottom line if i only ise 40/60% of the battery on a regular basis I am best off keeping it at 80% drawing down to 20/30% and have a little to spare?

AAKEE has been posting stuff about maximizing battery life for a long time. I used to charge to 60% on the assumption that the battery was happiest close to 50%, and I used about 8-14% each day, and I'd let the batteries sit overnight at whatever SoC I arrived back with before charging them up in the morning. But then after looking at all of the studies he posted, I determined the calendar degradation is actually minimized by keeping the SoC as low as possible, so I started setting the charge limit to 50%. I would set it lower (probably to around 30-35%) if I could, but Tesla only allows a minimum of 50%. If Tesla allowed use of Sentry Mode all the way down to 0%, I'd probably set it to 25% for daily driving, since in the rare case I actually wanted to use it, I'd still be able to (currently it shuts down below 20%).

 

[ewoodrick]

Nope. I’ll tell you why below.

This statement is because you lack knowledge about how these things is tested and evaluated. We will sort this out further down

Any descent chart or graph use Full Cycles Equivalent (FCE) to compare different cycle tests.

One FCE is the same energy as a full 100% to 0% cycle.
This means for 50% DoD cycles, two is needed to cover one FCE.
For 10% DoD cycles, ten is needed to cover one FCE.

I don't see anywhere that you specify which Tesla batteries that you are referring to. It makes a big difference. I mean just between the two Tesla batteries, one gets the 100% nag not to the other says you can.

Chemistry matters. Generic charts/studies tend to be not very useful.

Many of the EV manufacturers had issues with their batteries before about 2015, they all change to a much more reliable battery through some relatively small chemical and manufacturing changes. Yes, the manufacturing method had a big input.

 

[ewoodrick]

Fair point. If your EV was your only vehicle and you were worried about needing maximum range at the drop of a dime, I could see the desire to keep it charged to 90%.

I normally drive about 30 miles a day. Following your recommendation, I should probably only charge to about 20%? (60 miles)

 

[ewoodrick]

For those people, there are ICE vehicles. In fact, I have a PHEV, and if I am ever in that type of situation, I'd probably leave the Tesla at home and take the PHEV, just so I don't have to worry about where to charge at all.

I don't have an ICE, Just two Teslas.

I guess I could get on my riding mower and do it.

Wait, my mower is electric as well.

 

[STS-134]

I don't have an ICE, Just two Teslas.

I guess I could get on my riding mower and do it.

Wait, my mower is electric as well.

Sure, but you're not the one who has a ridiculous level of range anxiety. If you're so anxious that you're forever keeping your car charged to 90-100% for the 1 day in every 10 years or more than you might have to drive on short notice, and having to stop at a supercharger makes you even more anxious, an EV probably isn't for you. Or at least, you're the type of person who should keep at least one ICE vehicle around for that specific use case.

 

[ewoodrick]

Sure, but you're not the one who has a ridiculous level of range anxiety. If you're so anxious that you're forever keeping your car charged to 90-100% for the 1 day in every 10 years or more than you might have to drive on short notice, and having to stop at a supercharger makes you even more anxious, an EV probably isn't for you. Or at least, you're the type of person who should keep at least one ICE vehicle around for that specific use case.

No, but having range anxiety isn't a permanent state. And I do keep mine at 80-90% (where ever the slider falls), that's where I feel that guidance from Tesla tells you to set it to get the best experience from the battery and the car.

Basic answer, just stop worrying about the frigging battery. There's not really ANYTHING that you can do to damage it or change its lifetime.

 

[Drinyth]

I normally drive about 30 miles a day. Following your recommendation, I should probably only charge to about 20%? (60 miles)

Tesla doesn't provide a mechanism for you to go below 50% within their app or the vehicle itself. But sure, if you wanted to unplug or otherwise discontinue charging at 20%, from the data presented it would seem to indicate that that is indeed what would provide the lowest calendar aging for the battery.

Of course, at 20% you also start running into other issues like sentry mode not working. But from a battery longevity standpoint, it looks like charging to 20% and driving down to 10% would be even better than charging to 50% and driving down to 40% (although the aging differences between 20% and 50% are much less than 50% and 80%).

 

[Drinyth]

No, but having range anxiety isn't a permanent state. And I do keep mine at 80-90% (where ever the slider falls), that's where I feel that guidance from Tesla tells you to set it to get the best experience from the battery and the car.

Tesla lets you set the slider anywhere from 50% to 90% (daily range) or up to 100% (for maximum trip range). There are hash marks every 10%.

What is the best experience and what's best for your car can be different things. For people with long daily needs or people that want maximum available range at all times, I can see setting it to 80-90% being "best". For people that have lower needs and/or want to favor battery health over having available range, then I'd say that 50% would be "best".

Basic answer, just stop worrying about the frigging battery. There's not really ANYTHING that you can do to damage it or change its lifetime.

Damage it within Tesla's warranty parameters? Probably not. But I disagree with your statement that there isn't anything that you can do to change its lifetime.

 

[AAKEE]

I don't see anywhere that you specify which Tesla batteries that you are referring to. It makes a big difference

All Tesla batteries made by Panasonic is NCA chemistry. Most NCA in the research is Panasonic as there are not very many vendors of NCA batteries.

From the chart in an earlier post we can see that for calendar aging, there is no big difference in how they age nu from time.

The basic behaviour is more or less the same. There is a steep step in calendar aging that happens due to the centeal graphite peak, which differs due to chemistry. A NCA cell kept below 55% (58% is the exact point for a new NCA cell) and below 70% for LFP cells(72% is the initial point for LFP).
NMC has the same step.

So this basic behaviour is the same and the differences are small, like the rate is slightly different in some cases.
For all three of these chemistries it is safe to say that the calendar aging is lower at low SOC and higher at high SOC. Many research reports show that the calendar aging is slightly less above 80% at room temperature and that the maximum calendar aging happens at 80-90%.


For cyclic aging there is bigger differences but as cyclic aging is a much smaller part of the total aging this do not not change the total degradation that much.
The later generation LFP’s is less sensitive to large cycles, this is one of the reasons why these is used in Teslas with less capacity.

. I mean just between the two Tesla batteries, one gets the 100% nag not to the other says you can.

I do not get “the 100 nag”, is it maybe the standard range with LFP you are refering to?
They still have about the same calendar aging behaviour, maybe sligtly less in the latest generation but the basic behaviour would most probably be there anyway.
As they are less sensitive to large cycles Tesla do not need to try to reduce the high SOC to limit cyclic aging.

Tesla use all three chemistries in that chart:
Panasonic NCA
LG NMC (long range and Performance M3/MY built in Germany and China).
CATL LFP

Chemistry matters. Generic charts/studies tend to be not very useful.

Many of the EV manufacturers had issues with their batteries before about 2015, they all change to a much more reliable battery through some relatively small chemical and manufacturing changes. Yes, the manufacturing method had a big input.

While the basic behaviour has not changed very much, there are differences.
I do not refer to dated research reports in general but use data from as new reports as possible.

At Degradation you can select a wide number of Tesla models, including some older ones. There is not a very big differens in early Tesla model S and later.

 

[ewoodrick]

Damage it within Tesla's warranty parameters? Probably not. But I disagree with your statement that there isn't anything that you can do to change its lifetime.

So, how many more miles can I expect to get?

 

[STS-134]

Basic answer, just stop worrying about the frigging battery. There's not really ANYTHING that you can do to damage it or change its lifetime.

I'll tell you what. How about I buy two Teslas and drive them for the same number of miles and put the same number of FCE cycles on both of their batteries, except on one of them, I'll do everything I can to prolong the life of its batteries and on the other, I'll do everything I can to shorten the life of its batteries, according to what I believe shortens or prolongs the life of lithium ion batteries. If there is significantly more degradation on the one whose battery life I am trying to shorten, then you pay me for both Teslas but I remain the legal owner and can do whatever I want with them. Deal?