Battery degradation - 2019.32.2.2

[hcdavis3]

Don't let the short Y-axis fool you. Your Rated Range has varied no more than 7 miles, 320 to 327. It's barely more than a rounding error. If you set the Y-axis base to Zero, it'll look like a straight line!

Your last Rated Range figure is 324.5 miles, literally perfect.

Interestingly, my chart has a very similar shape. Alot of squiggles in Winter to Spring, then nice and flattish during the warm months, and then the beginning of squiggles again now that it's turned colder.
View attachment 480124
I put your chart on top of mine, and tried to normalize the scale a little bit. I put a red line in at 325 on yours and 310 on mine. Notice how similar the shapes are, and how the volatility of the squiggles increase as the weather gets colder.

In my opinion, it may be related to how the data is pulled from the API. When I typically get an outlier Rated Range figure, it's a colder night with more drain. The 3rd party app, in this case Stats, will show a higher SOC figure than the car or the Tesla app. If I use the car's SOC %age, and divide into the Range number, I'll get 308 to 312. The 3rd party app reads low on colder nights, presumably due to some drain, which shows up as a lower SOC in the car, but not in the 3rd-party app.

Here's a screenshot to illustrate:
View attachment 480128
You can see at the top the data from the Tesla app, 59% SOC. From Stats, I'm showing 60%. And the same from EV Watch. 3rd party apps, always lag behind the Tesla app and what the car will display.

If you take the Rated Range figure 184m, and divide by the 60% SOC, I get 306 miles, and that's what shows up in my graph, 306. But if I divide 184m by the correct 59% SOC that Tesla shows, then I get 311 miles.

Thanks Ken. I find all this data fascinating.

 

[JGard]

I'm going to set my charge limit to 60% and see how is does with a ~25% to 60% charge and where the rated range comes out. What makes me most concerned about this recent drop is what my odometer is showing for kWh usage over a certain battery range. Over the past two days I drove the car from 80% down to 40% charge, and the odometer said I used 26 kWh. When you run the math on 26kWh being 40% of the battery, this suggests my battery size is only 65kWh, when it should be 75kWh. So I wonder if there's more wrong with this update and its calculations.

 

[KenC]

I'm going to set my charge limit to 60% and see how is does with a ~25% to 60% charge and where the rated range comes out. What makes me most concerned about this recent drop is what my odometer is showing for kWh usage over a certain battery range. Over the past two days I drove the car from 80% down to 40% charge, and the odometer said I used 26 kWh. When you run the math on 26kWh being 40% of the battery, this suggests my battery size is only 65kWh, when it should be 75kWh. So I wonder if there's more wrong with this update and its calculations.

Since you drove over 2 days, you have to factor in the time that the car is sitting overnight, draining. Under optimal summer conditions, it might only be 0.1mi/hr, but under colder temps, it can be 0.8mi/hr or higher, especially if you have Sentry turned on. where it'll easily be 1.2mi/hr or more.

26kWh is 34.7% of a 75kWh battery. The diff from 40% is about 5%, and that 5% is 3.75kWh or about 13miles of range. Could your battery drain 13 miles? Sure, if Sentry was on, or it were really cold, or if it never slept.

 

[JGard]

Since you drove over 2 days, you have to factor in the time that the car is sitting overnight, draining. Under optimal summer conditions, it might only be 0.1mi/hr, but under colder temps, it can be 0.8mi/hr or higher, especially if you have Sentry turned on. where it'll easily be 1.2mi/hr or more.

26kWh is 34.7% of a 75kWh battery. The diff from 40% is about 5%, and that 5% is 3.75kWh or about 13miles of range. Could your battery drain 13 miles? Sure, if Sentry was on, or it were really cold, or if it never slept.

yeah but I’m not taking mileage into it so that shouldn’t factor in. It’s just showing me how many kWh were used since the last charge

also that charge up to only 70% trick didn’t help. My range is still down at that 304 mark. Just unsettling how all of a sudden it dropped significantly and now just stays there

 

[cherrybomb]

Well my first charge at the 70% level brought me to 212 not 217 as expected. I am also charging at 32 amps as opposed to 48amps. I assume I have to keep doing this for a few cycles to see if any of this will work. Looking through this thread I see many ppl have said the same thing so will report back after a few more charging cycles.

 

[Allistah]

Well my first charge at the 70% level brought me to 212 not 217 as expected. I am also charging at 32 amps as opposed to 48amps. I assume I have to keep doing this for a few cycles to see if any of this will work. Looking through this thread I see many ppl have said the same thing so will report back after a few more charging cycles.

Good luck to you.. I found myself spending so much time on this thing... time I didn't have to spend so I need to step back a bit. I am going to be charging to 90% as my baseline and then maybe sprinkling in some 95% and the occasional 100% to see what happens. I'll also be letting it fall to around 10% from time to time as someone else had suggested so it sort of knows where the bottom is. Let us know what you find out! The problem with all this is that it takes weeks to really see anything. Thats what makes this so difficult.

 

[Allistah]

I really wish they had a setting to display the predicted miles from your your driving habits/history on the main screen. I changed ours over to show % battery left because I didn't want my wife thinking she had x amount of miles left and get stuck somewhere since it is so wildly inaccurate. She drives aggressively so that available miles is way off. Would be cool if we had the choice on what to show there so it was much closer to being realistic.

 

[Snow Drift]

I am having the same issue. 90% = 272 miles vs. 279. (~1 year, 8655 miles on the car)

We are trying to hit 90% each night to recalibrate, with little change so far. I'll try the 70% trick when we get low.

 

[Allistah]

Sorry, I just can't leave this alone, I have to figure this out.

Take a look at this data... I took all the data from TeslaFi that was from charges above 50% and included incomplete charges as well to see if I could extract some information from it. The link to my sheet is below. I attempted to find out if there was something that resulted in a positive change in the estimated range at 100%, on average so I could see if there was a trend of some kind. This could give me tips to what charging practices that may help us figure this out. This is what I found.

From the data in the link below, I found that on average:

• On average, Decreases in charge % resulted in an INCREASE of the estimated range at 100%
• On average, Increases of charge % resulted in a DECREASE of the estimated range at 100%

The average decrease in charge % that resulted in an increase of range was -0.2075%.
The average increase in charge % that resulted in a decrease in range was 0.0161%.

To boil it down: We should do more, smaller decreases in charge % and less increases of charge %. If you do an increase, do it in one big charge, then do many charges with slightly decreased amounts.

See the bottom of my spreadsheet for these numbers in the link below.

Following this logic, if it's true, I should start by charging to 100% then every time you charge, decrease the charge to % by something like 5 or 10% to see if you get an increase, on average, of estimated range at 100% over time. So for me, something along the lines of:

Sunday - Charge to 100% and drive it down to 90% (So it's not at 100% very long)
Monday - Charge to 95% and drive down to 90% (So its not at 95% very long)
Tuesday - Charge to 90%
Wednesday - Charge to 85%
Thursday - Charge to 80%
Friday - Charge to 75%
Saturday Charge to 70%
Sunday - Back up to 100% and start over - if this is helping

Here is the link to my spreadsheet where I came to these findings:
Tesla Battery Info

Let me know what you think!

 

[Allistah]

If someone has TeslaFi and wants to give me their data in a spreadsheet, I'd be happy to do the same thing to see if this data is consistent across cars. This is what you should set your report to from TeslaFi below. Then I just copied all the data from the web page into a Google Spreadsheet.

 

[dmurphy]

I’m 100% convinced it’s a display thing and has no real bearing on “how far will the car go ...”

but ...

Since picking up the Model 3, I’ve “set it and forget it” at 90%. All has been linear ... except for the last month. See, a deer ended itself on my wife’s hood last month. Since then, she’s been driving the Model 3 (and how did I end up in the craptastic rental?? But I digress ...) In and of itself, that shouldn’t change anything ... except ... that now I’ve enabled scheduled charging, so the car is warm when she leaves in the morning. That seems to have had a minimal - but noticeable - effect on what charging to 90% means.

I say that because, on the weekends when it’s not scheduled and goes back to “Set it and forget it” - we see a small uptick.

so, yeah. My battery’s awesome. And I’m convinced that micro-managing charging percentages actually sends the BMS askew.

Set it, forget it, and drive the hell out of it!

 

[KenC]

I’m 100% convinced it’s a display thing and has no real bearing on “how far will the car go ...”

but ...

Since picking up the Model 3, I’ve “set it and forget it” at 90%. All has been linear ... except for the last month. See, a deer ended itself on my wife’s hood last month. Since then, she’s been driving the Model 3 (and how did I end up in the craptastic rental?? But I digress ...) In and of itself, that shouldn’t change anything ... except ... that now I’ve enabled scheduled charging, so the car is warm when she leaves in the morning. That seems to have had a minimal - but noticeable - effect on what charging to 90% means.

I say that because, on the weekends when it’s not scheduled and goes back to “Set it and forget it” - we see a small uptick.

so, yeah. My battery’s awesome. And I’m convinced that micro-managing charging percentages actually sends the BMS askew.

Set it, forget it, and drive the hell out of it!

View attachment 480469

Do you have a Stats screenshot of your full charge history?

 

[KenC]

Sorry, I just can't leave this alone, I have to figure this out.

Take a look at this data... I took all the data from TeslaFi that was from charges above 50% and included incomplete charges as well to see if I could extract some information from it. The link to my sheet is below. I attempted to find out if there was something that resulted in a positive change in the estimated range at 100%, on average so I could see if there was a trend of some kind. This could give me tips to what charging practices that may help us figure this out. This is what I found.

From the data in the link below, I found that on average:

• On average, Decreases in charge % resulted in an INCREASE of the estimated range at 100%
• On average, Increases of charge % resulted in a DECREASE of the estimated range at 100%

The average decrease in charge % that resulted in an increase of range was -0.2075%.
The average increase in charge % that resulted in a decrease in range was 0.0161%.

To boil it down: We should do more, smaller decreases in charge % and less increases of charge %. If you do an increase, do it in one big charge, then do many charges with slightly decreased amounts.

See the bottom of my spreadsheet for these numbers in the link below.

Following this logic, if it's true, I should start by charging to 100% then every time you charge, decrease the charge to % by something like 5 or 10% to see if you get an increase, on average, of estimated range at 100% over time. So for me, something along the lines of:

Sunday - Charge to 100% and drive it down to 90% (So it's not at 100% very long)
Monday - Charge to 95% and drive down to 90% (So its not at 95% very long)
Tuesday - Charge to 90%
Wednesday - Charge to 85%
Thursday - Charge to 80%
Friday - Charge to 75%
Saturday Charge to 70%
Sunday - Back up to 100% and start over - if this is helping

Here is the link to my spreadsheet where I came to these findings:
Tesla Battery Info

Let me know what you think!

So, here's an observation that you may find interesting.

Look at the correlation.

My takeaway is that temperature change correlates to BMS drift. If you look at @hcdavis3 's post on the prior page, his battery chart, looks alot like my battery chart, and wouldn't you know it, we are in the same geographical area, so our vehicles see roughly the same swings in temps.

 

[Allistah]

Hey - thanks for the post!

Indeed, the correlation is pretty much right there. I don't doubt that colder weather affects it. But what is weird is that it seems that I can control the increases as well with my charging habits which you wouldn't think should be the case, but I guess that's the way it is. Going to do some other experiments which I've made my own thread for and I'll be posting back tonight after I get the data. Look at my other thread I made and tell me what you think..

 

[dmurphy]

Do you have a Stats screenshot of your full charge history?

Unfortunately I only have a few months’ worth of data as I guess I reinstalled the app along the way.

Charging data:

Range data:


p

 

[KenC]

Unfortunately I only have a few months’ worth of data as I guess I reinstalled the app along the way.

Charging data:

View attachment 480589

Range data:
View attachment 480586
View attachment 480587
View attachment 480588 p

It's okay, the same happened to me, but I found most of my early data in an early export.

 

[dmurphy]

It's okay, the same happened to me, but I found most of my early data in an early export.

Pro tip! Tesla made a backend change, so if you triple-tap the main screen in Stats, it retrieves the original data.

Here's the historical; for the charge data, I set it at 30-day so we could see it all on one graph.

 

[KenC]

Now that's a flat line!

 

[Allistah]

Pro tip! Tesla made a backend change, so if you triple-tap the main screen in Stats, it retrieves the original data.

Can you elaborate on this? I tried triple clicking on the main screen in Stats but couldn't see what you were talking about.

 

[KenC]

Can you elaborate on this? I tried triple clicking on the main screen in Stats but couldn't see what you were talking about.

From the Stats FAQs;