My M3 was built in July 2018, 76XXX off the Fremont line, LR RWD. Battery capacity since delivery has degraded by 9.5%, now at 280 miles. And that’s based on the high starting range of 309 mile when new. I never saw a ratings bump to 325. Of 113 M3s in the TeslFi database at my mileage level (low at less than 15k miles) 113 have better degradation results.
I charge whenever the SoC is more than 10% below my 80% SoC target. I leave the car plugged in to a HPWC between charges. I have supercharged only once in 24 months (at the SC). I’ve never dropped below 20% SoC, and rarely drop below 50%. I’m being very gentle and yet the battery is declining.
So outlier battery degradation cases like mine can definitely happen without charging weirdness.
I will give the recalibration process a try. It’s been a while since deep discharge.
as has been said many times, "charging only to 80%" confuses the BMS over time, so your "charging only to 80"% is likely why your rated miles looks the way it is. You ARE being "gentle" to the battery, but you are also guaranteeing that your BMS never sees the voltage of a higher 90% charge, so never really gets to see whats "actually" there.
If you want the number to appear higher, stop charging to "only 80%" and set it to 90% and let it sit there for a while (measured in several days, not hours, or "one charge to 90%". The pack will balance itself. You will likely (after a week or so) see a higher number reported in your car, while simultaneously putting a little more actual wear on your battery.
Or, keep charging to 80%, and be secure in the fact that you are actually babying your battery, but your car likely does not know its true pack range, so your reported number may keep going down.
I think for my own sake, I likely shouldnt look at, read or post to any more of these "battery degradation" threads, since my car seems to be "so different" than everyone who is following some specific charging regimine that isnt in the manual.
(I charge to 90% all the time, and my car only recently adjusted range down when they stated that Model3Ps with 20 inch wheels had 299 range and not 310). My car shows 298-299 range. Its a 2018 model 3P with 23.5k miles on it, always charged to 90%, always plugged in when not driven).