So, I finally got around to adding the temperature data from the last year to my Stats battery health data. Unlike Teslafi, we don't get the temp data, so I had to add it in manually.
This is my Stats Battery Health data. As I got my car in December, it's now been almost a year. Ignore the straight line, as you can see it's starting to show a curve. My stats data is missing my first 2000 miles, due to software issues, when my rated range was lower, as low as 287 miles. Originally, I charged to 90%, because it was Winter. Then as Spring hit, I changed to 80%, and my Rated Range improved. Based upon that one datapoint, I thought perhaps the more conservative approach to charging improved my range. Now that Winter has hit, my Rated Range has started to drop again, which kind of disproves that theory.
But, it raises another one, that my Rated Range is varying with ambient temperature change.
So, I finally got around to exporting my Stats data, and adding the temperature data manually, and this is what it shows. Luckily, I also had my range data from January/February, all the way back to 400 miles on the odometer.
I've graphed the Temperature on the left axis in red, and the Rated Range on the right axis in blue. I adjusted the scale to get them to overlay, and as you can see, as the seasons pass and the temp changes, my Rated Range bounces in sync. There's a red horizontal line at 310 miles to show my battery is right there during the summer months. And the dark blue squiggly line is a moving average to smooth out the bounces.
So, there seems to be a strong correlation between my Rated Range as reported by Stats and outside temps. My car is outdoors year-round, as I don't have a garage.
Now, I think there may be at least 3 things going on, making analysis difficult: one, BMS drift, like mine, due to seasonal temp change; two, sudden BMS drop, which I'm not sure anyone can quite explain yet, could be buffer change, could be software update causing BMS error, etc; and three, real battery deg.
Mine seems to be completely BMS drift. The interesting thing, is if I look at Stats and the Tesla app at the same time, I notice that there's a mismatch when it's cold. Tesla shows my SOC at 59%, while Stats sees it at 60%. If you divide the Rated Range number in the lower left corner, 184miles, by 59%, you get 312 miles; and if by 60%, you get 307 miles, a 5 mile difference. Which is right? Well, the Tesla app is what the car shows, if I toggle the odometer display from range to SOC, it'll show what the Tesla app shows, 184miles and 59%. The Stats app, and the other 3rd party app I have EV Watch, show the same 60%. It lags. And, since it's cold, it always lags high, resulting in Rated Range estimates too low. During the warm months, there's no lag, because the vampire drain is low. During the cold months, the vampire drain is high, so the lag coming from the API becomes apparent. It may be the API doesn't update as often as the car itself does.
My drain in summer was 0.1miles/hr. My drain last winter was 0.4miles/ hr. I would suggest to anyone with possible BMS drift issues, to just toggle their display from miles to SOC and back, and do the math manually. Whenever I get an oddly low Rated Range figure as reported by Stats, when I do the math manually, I always get 308 to 312 miles. My battery isn't showing any change, but if I were to only look at Stats, I'd think there was something going on, when there isn't. Last winter, I vaguely recall, the difference being greater than 1%, as high as 3%. I'll try to capture a screenshot this year.
So, my conclusion is, if you just have BMS drift, like I do, there's nothing wrong with your battery, it'll bounce back when the temps warm up. If you have big drops, like some people I've seen, then I'd consider trying to recalibrate the BMS, once a month, to see if that corrects it. And, if you have true deg, then there's nothing to do, but either try to slow it down, by charging only up to 63%, 3.92V, or speed it up and get 30% deg and file a warranty claim to have your battery replaced.
This is my Stats Battery Health data. As I got my car in December, it's now been almost a year. Ignore the straight line, as you can see it's starting to show a curve. My stats data is missing my first 2000 miles, due to software issues, when my rated range was lower, as low as 287 miles. Originally, I charged to 90%, because it was Winter. Then as Spring hit, I changed to 80%, and my Rated Range improved. Based upon that one datapoint, I thought perhaps the more conservative approach to charging improved my range. Now that Winter has hit, my Rated Range has started to drop again, which kind of disproves that theory.
But, it raises another one, that my Rated Range is varying with ambient temperature change.
So, I finally got around to exporting my Stats data, and adding the temperature data manually, and this is what it shows. Luckily, I also had my range data from January/February, all the way back to 400 miles on the odometer.
I've graphed the Temperature on the left axis in red, and the Rated Range on the right axis in blue. I adjusted the scale to get them to overlay, and as you can see, as the seasons pass and the temp changes, my Rated Range bounces in sync. There's a red horizontal line at 310 miles to show my battery is right there during the summer months. And the dark blue squiggly line is a moving average to smooth out the bounces.
So, there seems to be a strong correlation between my Rated Range as reported by Stats and outside temps. My car is outdoors year-round, as I don't have a garage.
Now, I think there may be at least 3 things going on, making analysis difficult: one, BMS drift, like mine, due to seasonal temp change; two, sudden BMS drop, which I'm not sure anyone can quite explain yet, could be buffer change, could be software update causing BMS error, etc; and three, real battery deg.
Mine seems to be completely BMS drift. The interesting thing, is if I look at Stats and the Tesla app at the same time, I notice that there's a mismatch when it's cold. Tesla shows my SOC at 59%, while Stats sees it at 60%. If you divide the Rated Range number in the lower left corner, 184miles, by 59%, you get 312 miles; and if by 60%, you get 307 miles, a 5 mile difference. Which is right? Well, the Tesla app is what the car shows, if I toggle the odometer display from range to SOC, it'll show what the Tesla app shows, 184miles and 59%. The Stats app, and the other 3rd party app I have EV Watch, show the same 60%. It lags. And, since it's cold, it always lags high, resulting in Rated Range estimates too low. During the warm months, there's no lag, because the vampire drain is low. During the cold months, the vampire drain is high, so the lag coming from the API becomes apparent. It may be the API doesn't update as often as the car itself does.
My drain in summer was 0.1miles/hr. My drain last winter was 0.4miles/ hr. I would suggest to anyone with possible BMS drift issues, to just toggle their display from miles to SOC and back, and do the math manually. Whenever I get an oddly low Rated Range figure as reported by Stats, when I do the math manually, I always get 308 to 312 miles. My battery isn't showing any change, but if I were to only look at Stats, I'd think there was something going on, when there isn't. Last winter, I vaguely recall, the difference being greater than 1%, as high as 3%. I'll try to capture a screenshot this year.
So, my conclusion is, if you just have BMS drift, like I do, there's nothing wrong with your battery, it'll bounce back when the temps warm up. If you have big drops, like some people I've seen, then I'd consider trying to recalibrate the BMS, once a month, to see if that corrects it. And, if you have true deg, then there's nothing to do, but either try to slow it down, by charging only up to 63%, 3.92V, or speed it up and get 30% deg and file a warranty claim to have your battery replaced.
