Battery degradation question

[Mike_NoGas]

Hi,
I was trying to check the service menu for battery health check and I started it, it went to zero and start to charge to 100%, but it didn't give me the the health percentage.

Scan my Tesla shows car was on zero SoC, and the car showing +61Kwh was added that's means about 17.5% degradation for 2019 Model 3 performance with 90K mileage, however the car showing 279 total mileage of 310 car rated from Tesla and that about %10 degradation. Would someone help understand what's going on and why battery health didn't work.

Please I don't need just drive it comments as I'm doing it for 4 years already with 90K. But I'm really curious about how much I lost so far?

 

[KenC]

Some images of the screens you are looking at, helps. Battery health doesn't always give a result. Sometimes there's a glitch. As I said, a screenshot of what you saw, would help.

 

[Perscitus]

Try this, works much better than other methods (at least until we figure out how to open the contactors while in the service menu to be able to hard reset the BMS calibration based on HVB open voltage at >90% SoC).

Don't go by kWh added, instead if youre going to attempt to use basic info the car provides, deplete the SoC to single digit territory, keep unplugged and let the car deep sleep for 2-4hrs, with a way to charge nearby or where parked. Charge up to north of 90 or better yet 'assumed' 100 SoC, giving time for top end 'calibration' to happen if it triggers,
unplug and let car deep sleep at its supposed 100 SoC for 2hrs. No harm in doing that.

Drive off and travel at least 30-50 miles at fairly constant speed and 'throttle', ideally with no AC, no heater, no accessories powered and no lights except what the car forces on.

Pull over and take note of miles travelled since 100 SoC down to whatever it will show at 30, 50, 80 miles later. Extrapolate full charge range from that.

Then go back to the video above to try and force the BMS to adjust its estimated range at any given SoC for your car.
See if after doing the procedure once or twice over the course of a month, the range at say 90 SoC recovers back up or remains the same as now.

 

[jjrandorin]

Hi,
I was trying to check the service menu for battery health check and I started it, it went to zero and start to charge to 100%, but it didn't give me the the health percentage.

Scan my Tesla shows car was on zero SoC, and the car showing +61Kwh was added that's means about 17.5% degradation for 2019 Model 3 performance with 90K mileage, however the car showing 279 total mileage of 310 car rated from Tesla and that about %10 degradation. Would someone help understand what's going on and why battery health didn't work.

Please I don't need just drive it comments as I'm doing it for 4 years already with 90K. But I'm really curious about how much I lost so far?

What do you get when you follow the information in the stickied thread on how to calculate your battery capacity using the information on the cars screen?

Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen

Re posting here and making this a sticky post so it doesnt get lost. @AlanSubie4Life originally posted: =========================================== (originally posted by @AlanSubie4Life. Original thread this appeared in can be found here: ( 2021 model Y scan my Tesla battery size)...

teslamotorsclub.com

 

[Mechsmoto]

Quick question fir those of you with a much better understanding of this. I just did the let it sit for 3 hours at 8%... charge to 100% and let it balance. Range didn't change at all... but when I parked after doing a run to get it off 100%. I was at 88% soc. I didn't plug it in, just left it sit. When I went back it was at 90% on its own, and is now at 91%. Does this mean the BMS is indeed off in its calculations? I'm seeing 7% degradation according to tessie app with 26,000 miles. Mostly home charged with a shared charger so more often than not 24a or 7kw is the charge rate. Appreciate any help or insight you may be able to provide!!!

 

[Mechsmoto]

Quick question fir those of you with a much better understanding of this. I just did the let it sit for 3 hours at 8%... charge to 100% and let it balance. Range didn't change at all... but when I parked after doing a run to get it off 100%. I was at 88% soc. I didn't plug it in, just left it sit. When I went back it was at 90% on its own, and is now at 91%. Does this mean the BMS is indeed off in its calculations? I'm seeing 7% degradation according to tessie app with 26,000 miles. Mostly home charged with a shared charger so more often than not 24a or 7kw is the charge rate. Appreciate any help or insight you may be able to provide!!!

Car is M3P, September of 22, Fremont, always been on the 90 and forget it approach. Could have sworn my 21 m3p had 76-77kwh at similar mileage. This one is showing 73.4... again according to tessie. I do have SMT if there is data that can be found there that would help... please let me know.

 

[KenC]

Quick question fir those of you with a much better understanding of this. I just did the let it sit for 3 hours at 8%... charge to 100% and let it balance. Range didn't change at all... but when I parked after doing a run to get it off 100%. I was at 88% soc. I didn't plug it in, just left it sit. When I went back it was at 90% on its own, and is now at 91%. Does this mean the BMS is indeed off in its calculations? I'm seeing 7% degradation according to tessie app with 26,000 miles. Mostly home charged with a shared charger so more often than not 24a or 7kw is the charge rate. Appreciate any help or insight you may be able to provide!!!

For me, when that happens, it means the battery is warmer than when I first started. That is, when I left the house, the car was cold, the battery was cold. I drove somewhere, the car and battery warmed up, it sat in the warm sun, and the battery warmed up some more. When I got back in, based upon the new ambient, the SOC had increased by 2-3%. In the below chart, I consumed 15.9%, but when you look it went from 59% to 45%, or about 14%. The jump at around mile 28 was around 2%, when the car sat in the sun, when I had a doctor's appt. The opposite occurs, when the car and battery get colder, after sitting longer. It'll show drops. As far as I can tell, the SOC calculates based upon the ambient temp of the pack when you start driving, so even short stops can have a jump or drop.

As far as I can tell, it has nothing to do with pack degradation, or that the BMS is off. It's just calculating based upon the conditions it sees, and if the environmental conditions change, then you'll get a recalculation.

 

[Mechsmoto]

For me, when that happens, it means the battery is warmer than when I first started. That is, when I left the house, the car was cold, the battery was cold. I drove somewhere, the car and battery warmed up, it sat in the warm sun, and the battery warmed up some more. When I got back in, based upon the new ambient, the SOC had increased by 2-3%. In the below chart, I consumed 15.9%, but when you look it went from 59% to 45%, or about 14%. The jump at around mile 28 was around 2%, when the car sat in the sun, when I had a doctor's appt. The opposite occurs, when the car and battery get colder, after sitting longer. It'll show drops. As far as I can tell, the SOC calculates based upon the ambient temp of the pack when you start driving, so even short stops can have a jump or drop.

As far as I can tell, it has nothing to do with pack degradation, or that the BMS is off. It's just calculating based upon the conditions it sees, and if the environmental conditions change, then you'll get a recalculation.
View attachment 951804

 

[Mechsmoto]

Thanks so much for your detailed response! The way you explained it makes perfect sense!

 

[Mechsmoto]

One more quick question. After running the battery down from 100% SOC to 83%... under trips tab I see 54 miles... 14kwh used... 256wh/mi.

I checked to see what number 14 is 17% of... and it shows me 82.35?? If the pack total is 82.1kwh including a buffer... how could this be possible when I'm supposed to be at 7% degradation? @73.4kwh.

Guess I'm gonna sweat for a min while I wait for HV disconnect so I can plug OB2 back in and check SMT.

 

[E90alex]

Indicated SOC is not true battery SOC

 

[RayK]

Plus there's a rounding error. Miles and kWh are displayed as integer numbers, not fractional.

 

[Mechsmoto]

Thanks again for the help! I felt dumb as soon as I hit submit on the question, as KenC had already explained SOC is relative to temp.

On my 21 M3P I always charged to 90 and left it plugged in whenever possible... but only ever supercharged it once. It was somewhere between 76-77kwh at 25k miles before someone hit my wife driving it, and it got totalled out.

This time it's a year newer, but all else is the same... except the supercharging. It's probably been on 6-7 600 mile round trips... which have forced me to use Superchargers. Have kept it under 80% charge when using them... but I'm at 74.3kwh.

21 was 278 wh/mi lifetime.... 22 is at 270wh/mi lifetime.

 

[Mechsmoto]

Meant to type 73.4kwh not 74.3kwh

Thanks again for the help! I felt dumb as soon as I hit submit on the question, as KenC had already explained SOC is relative to temp.

On my 21 M3P I always charged to 90 and left it plugged in whenever possible... but only ever supercharged it once. It was somewhere between 76-77kwh at 25k miles before someone hit my wife driving it, and it got totalled out.

This time it's a year newer, but all else is the same... except the supercharging. It's probably been on 6-7 600 mile round trips... which have forced me to use Superchargers. Have kept it under 80% charge when using them... but I'm at 74.3kwh.

21 was 278 wh/mi lifetime.... 22 is at 270wh/mi lifetime.

 

[KenC]

One more quick question. After running the battery down from 100% SOC to 83%... under trips tab I see 54 miles... 14kwh used... 256wh/mi.

I checked to see what number 14 is 17% of... and it shows me 82.35?? If the pack total is 82.1kwh including a buffer... how could this be possible when I'm supposed to be at 7% degradation? @73.4kwh.

Guess I'm gonna sweat for a min while I wait for HV disconnect so I can plug OB2 back in and check SMT.

As mentioned, that is rounding. Go to SMT and take some screenshots:

That's a good one, NFP, Nominal Full Pack, relative to Full Pack when New.

And when you scroll down, you also get Cell imbalance. Oh, I thought mine showed 6mV, but it's showing 4mV. I don't balance it at all. Then when you go to the bottom you see your Full rated range vs your Full ideal range. My 2018 came with 310 EPA-rated miles.

 

[Mechsmoto]

Your stats are amazing man! Still showing 310 miles on a 2018 with 50k miles is outstanding!!! I'm only seeing 287 with half the mileage, and a car that's not even a year old yet! Sure hope mine plateaus sooner than later!

 

[Mechsmoto]

Your stats are amazing man! Still showing 310 miles on a 2018 with 50k miles. I'm seeing 259 with half the mileage and a car that's not even a year old. 50 miles of range sure is a tough pill to swallow! Super happy for you!!!... and super depressed for me!

I think this car was mire than likely a reject, that someone else caught, and I missed. I know my 21 said 278 at 90% when new... this one never did.