Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[AAKEE]

thanks! I'm hoping thats the case. The car is performing brilliantly in all other ways.
It just seems that it does this every time I start thinking about a long trip
Its been a 90% down to 60-70 most week days and occasional longer trips
Car is garaged and lives in Texas, so it gets hot in summer

That heat with 70% or more will take a bite of the battery.
Just remember that the degradation from time will be slower by ^2 in the future.

 

[AAKEE]

In theory, shallow discharges around 50% SOC are the most gentle on a battery. It may help, or it may not, but the only obvious strategy is if something isn't working for you, then change it up.

Not to be picky( ) but, actually the lower the SOC range is, the better for the battery. So the best range is not around 50%. As low as possible is causing the least degradation.
If you need 30% depth of discharge, cycles between 40 and 10% is better than centered around 50%( 65-35%).
Tesla instruction to charge asap if below 10 or 20% is most likely coupled to the risk if discharging the 12V battery and getting stranded.
All research show us that small cycles at low SOC is causing minimal degradation.

 

[Candleflame]

Not to be picky( ) but, actually the lower the SOC range is, the better for the battery. So the best range is not around 50%. As low as possible is causing the least degradation.
If you need 30% depth of discharge, cycles between 40 and 10% is better than centered around 50%( 65-35%).
Tesla instruction to charge asap if below 10 or 20% is most likely coupled to the risk if discharging the 12V battery and getting stranded.
All research show us that small cycles at low SOC is causing minimal degradation.

indeed, apart from undervolting cells (i.e.. below 0.0%) during heavy demand it seems that the emptier, the better, as long as its not 0.0%.
Most manufacturers recommend completely discharging the batteries for storage and then freezing them.

 

[AAKEE]

indeed, apart from undervolting cells (i.e.. below 0.0%) during heavy demand it seems that the emptier, the better, as long as its not 0.0%.
Most manufacturers recommend completely discharging the batteries for storage and then freezing them.

Yes, and as teslas 0% actually is 4.5% SOC (at the battery level) thats well above the Panasonic low limit(2.5V), there is a good margin from going to low on the cells.

If we make sure we not get stranded due to low SOC, the battery is fine.

 

[MaxRSM]

Yes, and as teslas 0% actually is 4.5% SOC (at the battery level) thats well above the Panasonic low limit(2.5V), there is a good margin

My BMS thinks that my LR battery is 69 Kwh now from 77.8 Kwh new.
SOC is 22% and battery cells are at 3.5 Volts.
It seems strange to me, because if i watch at this graph :

i can see that 3.5 volts are reached at 150 minutes on 214 minutes for total discharge , so 70%.
So it seems that 3.5 V should be 100%-70% = 30% of SOC, so a 10% difference.
BMS shows 10% of degradation...
Mmmh...
BMS is confused ? or Tesla put a cutoff at higher voltage and built a larger buffer on the bottom ?

 

[AAKEE]

My BMS thinks that my LR battery is 69 Kwh now from 77.8 Kwh new.
SOC is 22% and battery cells are at 3.5 Volts.
It seems strange to me, because if i watch at this graph :

i can see that 3.5 volts are reached at 150 minutes on 214 minutes for total discharge , so 70%.
So it seems that 3.5 V should be 100%-70% = 30% of SOC, so a 10% difference.
BMS shows 10% of degradation...
Mmmh...
BMS is confused ? or Tesla put a cutoff at higher voltage and built a larger buffer on the bottom ?

The degradation will not show as a different voltage vs SOC. It will show as less capacity drawn from X to Y % SOC.

In the cycle test in the video the cell was loaded with 0.25C, that means it would go from full to empty in about four hours.
If you load your battery with 0.25C, that will be a power of about 17.5kW, your voltage will be lower for the same SOC.

The voltage vs SOC must be compared at the same load, or preferably at no load.
Thats why the BMS likes to having the battery at rest( contactors open) to be able to take a no load voltage.

Here is an example of a panasonic lithium battery discharge curves, with different loads.
There's one more factor, the temperature of the cell have an impact on the voltage curve. The colder, the lower voltage at the same SOC at load.
1A is about 0.2C, or 14kW power in the car.
We can se htat a full battery drop 1 Volt initially( from 4.2 to 4.1V) when the 1A load is applied.

Tesla have a 4.5% buffer in the bottom side, and 0% on the Tesla screen is supposed to be 4.5% "true" SOC. This shifts the voltage to a sligtly higher value for the same SOC.
True SOC should be something like = [SOC + (100-SOC)x0.045] where SOC ins the tesla showed SOC, and true SOC is the battery specs from max to minimum voltage.

So, you would have had a lower voltage if you had been driving at high road speed(about 0.25C), so probably thats the difference you see.
Of course, the temperature of the cells need to be about the same.

 

[AAKEE]

My BMS thinks that my LR battery is 69 Kwh now from 77.8 Kwh new.
SOC is 22% and battery cells are at 3.5 Volts.
It seems strange to me, because if i watch at this graph :

i can see that 3.5 volts are reached at 150 minutes on 214 minutes for total discharge , so 70%.

So, your 22% actually was 22+(100-22)x0.045 = 25.5%
25.5% at no load will have show a higher voltage so its not strange if it matches 30% at 0.25C load.

 

[raptor5244]

I know I will be told to just set it to percentage instead of miles of range but humor me. I am wondering what other SR+ with some miles owners are seeing. My car is a 2019 SR+, never been supercharged, always charged at home at 32 amp via wall connector. When we first bought it our 90% charge would yield about 210 miles of range, or about 231 miles on a full charge. About a year later it dropped to about 193 miles at 90%, now at 28 months and 26,000 miles and 90% yields 180 miles of range. Based on what I read, Tesla warranties the battery once you exceed 30% degradation or 168 miles of range in my case? Anyone, know how they technically validate the degradation? Can they run a test remotely?

 

[jjrandorin]

I know I will be told to just set it to percentage instead of miles of range but humor me. I am wondering what other SR+ with some miles owners are seeing. My car is a 2019 SR+, never been supercharged, always charged at home at 32 amp via wall connector. When we first bought it our 90% charge would yield about 210 miles of range, or about 231 miles on a full charge. About a year later it dropped to about 193 miles at 90%, now at 28 months and 26,000 miles and 90% yields 180 miles of range. Based on what I read, Tesla warranties the battery once you exceed 30% degradation or 168 miles of range in my case? Anyone, know how they technically validate the degradation? Can they run a test remotely?

I believe they can run remote tests. It should be based on whatever the specification was when new which was 240 miles I believe. That would be 168 miles like you said.

 

[KenC]

Not to be picky( ) but, actually the lower the SOC range is, the better for the battery. So the best range is not around 50%. As low as possible is causing the least degradation.
If you need 30% depth of discharge, cycles between 40 and 10% is better than centered around 50%( 65-35%).
Tesla instruction to charge asap if below 10 or 20% is most likely coupled to the risk if discharging the 12V battery and getting stranded.
All research show us that small cycles at low SOC is causing minimal degradation.

Interesting. When reading the "scientific" battery thread, a couple years ago, my vague recollection was that I should keep my battery lower than 3.92V, if I wanted to reduce cathode cracking issues, and above something, I forget what %age, to reduce anode plating, which slows charging and discharging. Maybe I should re-read that thread, it's been a while.

 

[Zoomit]

Interesting. When reading the "scientific" battery thread, a couple years ago, my vague recollection was that I should keep my battery lower than 3.92V, if I wanted to reduce cathode cracking issues, and above something, I forget what %age, to reduce anode plating, which slows charging and discharging. Maybe I should re-read that thread, it's been a while.

Wow, that thread was 2.5 years ago. I rewatched the video and picked-up more than when it originally came out.

Per the video, Low SoC causes current collector dissolution particularly at very low SoC (<5%) with mild effects below 15-20% SoC. See 10:53 and summarized at 16:36. This is just one effect, however, and the main point of the video is that there are many related and unrelated causes that combine to result in battery degradation.

Here's the thread with a link to the video: Battery Degradation Scientifically Explained

 

[MaxRSM]

So, your 22% actually was 22+(100-22)x0.045 = 25.5%
25.5% at no load will have show a higher voltage so its not strange if it matches 30% at 0.25C load.

Ok, thank you for the hint.
Today i have discharged the battery to 16% and drove uphill with a 25 Kw output from the battery ( 25/75 = 0.3C ) , the BMS was updating single cells all the time and reads were around 3.4 ( 3.35 -3.45 )
16 + (100-16 ) x0.045 = 19,8%
3.4 volt @ 20% SOC seems ok , it's like the graph from the YT video i posted above.
Without load the cells return to 3.5 volts.
So i think BMS needs also that the car is driven at low SOC , not only to be left to sleep for some hours at low SOC to have a good reading.

 

[AAKEE]

Interesting. When reading the "scientific" battery thread, a couple years ago, my vague recollection was that I should keep my battery lower than 3.92V, if I wanted to reduce cathode cracking issues, and above something, I forget what %age, to reduce anode plating, which slows charging and discharging. Maybe I should re-read that thread, it's been a while.

Well, I havent seen any research results that points at low SOC causes degradation.
Actually all research reports( 30+ research reports) I have seen points towards low SOC causes both lowest capacity degradation.

I’d like a link to that scientific battery thread if possible, I’ll read it and see.

I thought I would be able to stay with easy not that deep digging posts. This will be a messy deep dig, though

There’s a lot of info in the research telling is the facts.
For capacity, degradation in lost capacity of course. For the ability to release or recieve energy, increase in IR / internal resistance and impedance tell us about the changes that causes slower charging and less power.
Low IR will also cause low heat losses during drive, so it is a good thing.
Most graphs is easy to interpret, and show us that the less SOC the less degradation in capacity and charging speed/power.
The most research resports have graphs like this: It seems like a very good idea to use the lowest SOC possible.
These might lack one dimension, it shows the increase in internal resistance (IR) for the selected storage SOC. But it doesnt show the IR over the range for one selected storage SOC.

For the one below, the first view could fool one to believe that 10% SOC is worse than 20 or 30%.
The storage SOC is shown on the bottom axis(X-axis).
The tested IR at a specific SOC is what we read in tip of each picture.
At 10% SOC the IR is high to begin with( we notice lower power). While it is possible to ”save” the IR for 10% SOC, this could be done by store the battery at 75% SOC but that would cause more increase of IR over a big range of SOC, where we like to have most power. We will also loose more capacity .

To the mess: we have a storage SOC, at what SOC the battery was stored. But we would like to know how a specific storage SOC affects the battery over the whole range.
As an example, the 60% SOC picture tell us how the IR was affected at 60% SOC and the bottom axis show which storage SOC the battery had.
We can see that it is a more or less straight line between 0 and 35-40% SOC, where we have the least increase in IR.
This is more or less the same for SOC between 30 and 80% SOC, and the small increase barely noticable at 20 and 90% show us that low storage SOC is better for virtually all SOC’s.
If we check the 100% SOC picture, the lowest IR Increase comes from 25-30% SOC, so a small increase if a SOC below 25% is used. Still, if stored at 0% it is better than all storage SOC above 40%.

The conclusion is that the lower the SOC when the car is used, the less capacity fade will occur. Also, the internal resistance in the most used range( 90-20%) will increase least, meaning least degradation and most power available and also least heat losses from the battery.

This picture might take a while to understand, but it is very telling, so very good info. NCA if I remember it right.

 

[AAKEE]

Interesting. When reading the "scientific" battery thread, a couple years ago, my vague recollection was that I should keep my battery lower than 3.92V, if I wanted to reduce cathode cracking issues, and above something, I forget what %age, to reduce anode plating, which slows charging and discharging. Maybe I should re-read that thread, it's been a while.

I found the link, saw the video( seen it before), also shimmed through the thread but only the EV Tech posts. Good information. If you’ll be looking at the thread again you find that EV Tech refer to the same research report in that thread as one of the one I have been using. I also think there was a reference to store at low SOC is good, as long as the battery doesnt go completely blank( 1 or 2% was mentioned).

For the low SOC, I still have to see a research report that points to anything that is not good with low SOC.

I think EV Tech show all degrading mechanisms in that video, regardless of how severe or small each one is. The degrading mechanism from low SOC doesnt seem to happen or is outmanouvered by other mechanism that makes the total degradation less at low SOC anyway.
I dont know if he still is around but a discussion about these things would be very interesting.

 

[KenC]

Well, I havent seen any research results that points at low SOC causes degradation.
Actually all research reports( 30+ research reports) I have seen points towards low SOC causes both lowest capacity degradation.

I’d like a link to that scientific battery thread if possible, I’ll read it and see.

I thought I would be able to stay with easy not that deep digging posts. This will be a messy deep dig, though

There’s a lot of info in the research telling is the facts.
For capacity, degradation in lost capacity of course. For the ability to release or recieve energy, increase in IR / internal resistance and impedance tell us about the changes that causes slower charging and less power.
Low IR will also cause low heat losses during drive, so it is a good thing.
Most graphs is easy to interpret, and show us that the less SOC the less degradation in capacity and charging speed/power.
The most research resports have graphs like this: It seems like a very good idea to use the lowest SOC possible.
These might lack one dimension, it shows the increase in internal resistance (IR) for the selected storage SOC. But it doesnt show the IR over the range for one selected storage SOC.
View attachment 725542

For the one below, the first view could fool one to believe that 10% SOC is worse than 20 or 30%.
The storage SOC is shown on the bottom axis(X-axis).
The tested IR at a specific SOC is what we read in tip of each picture.
At 10% SOC the IR is high to begin with( we notice lower power). While it is possible to ”save” the IR for 10% SOC, this could be done by store the battery at 75% SOC but that would cause more increase of IR over a big range of SOC, where we like to have most power. We will also loose more capacity .

To the mess: we have a storage SOC, at what SOC the battery was stored. But we would like to know how a specific storage SOC affects the battery over the whole range.
As an example, the 60% SOC picture tell us how the IR was affected at 60% SOC and the bottom axis show which storage SOC the battery had.
We can see that it is a more or less straight line between 0 and 35-40% SOC, where we have the least increase in IR.
This is more or less the same for SOC between 30 and 80% SOC, and the small increase barely noticable at 20 and 90% show us that low storage SOC is better for virtually all SOC’s.
If we check the 100% SOC picture, the lowest IR Increase comes from 25-30% SOC, so a small increase if a SOC below 25% is used. Still, if stored at 0% it is better than all storage SOC above 40%.

The conclusion is that the lower the SOC when the car is used, the less capacity fade will occur. Also, the internal resistance in the most used range( 90-20%) will increase least, meaning least degradation and most power available and also least heat losses from the battery.

This picture might take a while to understand, but it is very telling, so very good info. NCA if I remember it right.

View attachment 725427

So, does that mean storage at 10% SoC raises IR levels?

 

[AAKEE]

So, does that mean storage at 10% SoC raises IR levels?

Short answer: No.

All storage SOC above 35-40% causes a higher increase in IR than at 10%.

The difference between 10% and the SOC that causes the lowest increase of IR (SOC 30%) is neglible.

If stored at 10%, the increase of IR in the normal SOC usage range is perhaps about 5-10% over a year.
If stored at 60-80% the increase is about 20-40%.

 

[swazi1]

My SR+ 2019 just had the High Voltage Battery replaced under warranty.

But the reconditioned battery is giving me about a 210 mile range at 100%. From the last few days of driving I believe this estimate is accurate based on normal (not high speed etc.) driving in normal conditions.

I performed the calculation of kWh today and got 45.6kWh

The answers I got from SC is not satisfactory in my mind. It ranged from "don't worry about it, it needs to relearn your driving habits" to "don't focus on the miles, only look at the %".

I have had the car for 2.5 years and I think I know what to expect and not expect.
My reasoning is that when we get a new car it gives an accurate display of the range (at the level of charge). There is no "learning the habits of the driver". It shows the range based on the estimated range and will either achieve that range or not based on driving and weather.

My best guess is that the pack is not calibrated across the cells.
But maybe there is an issue with the pack?
I feel I need to figure this out quickly to push back against the SC in case this pack is a dud.

I tried running the battery down to ~5% and charging to 100% but no success. But I have not had an opportunity to do it twice in a row yet.
I read about a couple of other possible techniques: Charge to 90 and let it sit there for a few hours. Another popular discussion on here talks about normal charging and letting the car sleep to calibrate. But it seems that could take months.

And lastly, I did some searching but could not find any previous complaints with remanufactured packs.

 

[jjrandorin]

My SR+ 2019 just had the High Voltage Battery replaced under warranty.

But the reconditioned battery is giving me about a 210 mile range at 100%. From the last few days of driving I believe this estimate is accurate based on normal (not high speed etc.) driving in normal conditions.

I performed the calculation of kWh today and got 45.6kWh

The answers I got from SC is not satisfactory in my mind. It ranged from "don't worry about it, it needs to relearn your driving habits" to "don't focus on the miles, only look at the %".

I have had the car for 2.5 years and I think I know what to expect and not expect.
My reasoning is that when we get a new car it gives an accurate display of the range (at the level of charge). There is no "learning the habits of the driver". It shows the range based on the estimated range and will either achieve that range or not based on driving and weather.

My best guess is that the pack is not calibrated across the cells.
But maybe there is an issue with the pack?
I feel I need to figure this out quickly to push back against the SC in case this pack is a dud.

I tried running the battery down to ~5% and charging to 100% but no success. But I have not had an opportunity to do it twice in a row yet.
I read about a couple of other possible techniques: Charge to 90 and let it sit there for a few hours. Another popular discussion on here talks about normal charging and letting the car sleep to calibrate. But it seems that could take months.

And lastly, I did some searching but could not find any previous complaints with remanufactured packs.

My guess is, you are expecting new range out of that replacement pack, and nothing in teslas warranty says they have to provide that. Its likely that what you are estimating is accurate.

This post I made in this thread has links to teslas battery warranty. I think I even put a screenshot of the relevant part of the warranty in this post:

https://teslamotorsclub.com/tmc/thr...n-battery-health.166549/page-156#post-6023654

 

[swazi1]

My guess is, you are expecting new range out of that replacement pack, and nothing in teslas warranty says they have to provide that. Its likely that what you are estimating is accurate.

This post I made in this thread has links to teslas battery warranty. I think I even put a screenshot of the relevant part of the warranty in this post:

https://teslamotorsclub.com/tmc/thr...n-battery-health.166549/page-156#post-6023654

I would say I was hoping for new range. I only had about 2% loss on the battery that got replaced and I'm not convinced the battery had to be replaced. But that's a different story.
And I realize, push comest to shove, under the warranty I have no basis to demand anything if the battery is above 70%. Thus my overall concern and wondering if there is (a) something I can do to get the battery sorted myself or (b) complain to Tesla and get a new pack (unlikely).

 

[stopcrazypp]

I would say I was hoping for new range. I only had about 2% loss on the battery that got replaced and I'm not convinced the battery had to be replaced. But that's a different story.
And I realize, push comest to shove, under the warranty I have no basis to demand anything if the battery is above 70%. Thus my overall concern and wondering if there is (a) something I can do to get the battery sorted myself or (b) complain to Tesla and get a new pack (unlikely).

They are supposed to replace with a battery of an energy capacity equivalent to the battery they replace (or at least of that of a car in similar age/mileage). Are you saying that the replacement pack has significantly less range than the one it replaced? If so, you may be able to take that up with them if you have documented evidence of that (like for example rated range much lower).

It's pretty clear however they won't be replacing with a brand new pack or a pack that is like-new in terms of capacity.