Wow. Didn't expect to see this thread resurrected.
Been sitting on this, mostly, but since the last time I posted anything relevant here, a Tesla insider leaked a TON of data to me about the entire fleet of Tesla vehicles. That data quite clearly shows that no 85 was ever 85, no 90 was ever 90. In fact, the vast majority of 90 packs have even degraded to be below the capacity of the vast majority of 85 packs at the time that data was given to me. This is
their own internal data. 60, 70, 75, and 100s get a pass, as most of those meet spec. 85 and 90 folks got mislead, and they should be labeled 80 and 85 respectively. Since Tesla charges.. what, $3k to upgrade from a 70-75? ... I feel like we should all get $3k in credit or something. Not going to happen, but it is what it is.
Also since that time I've run capacity tests on loads of 85-type modules... and, you guessed it, not even the best come out to 85 kWh total capacity.
Next, I actually spoke with an ex-Tesla engineer who actually worked on the BMS software early on. He explained that the 4 kWh "buffer" doesn't mean what we think it means. It was actually a kludge built in to smooth the range calculation, and to make sure you actually could hit zero miles consistently without getting stranded. On average, the actual capacity "buffer" is 2 kWh, so the code was written so that a 4 kWh window was used and scaled along with the SoC as the car discharged, adjusted and calibrated as possible based on other measurements. This was to ensure that the range calculation would never adjust abruptly, and should never (rarely) run out of capacity while rated miles were > 0. TL;DR: The actual capacity left on the table by the value of the "buffer" is targeted by the BMS to be half that much.
Finally, in the past 2 years since my last substance post in this thread, I've almost completely reverse engineered the Tesla BMS software and hardware. Guess what's in there? Oh, right the factory "new" profiles for every battery type. More interestingly is that the other values (like those actually reported by the BMS) are directly
derived from the initial factory capacity number. Anyone want to take a stab at what the new-from-the-factory values are for the "85"? Spoiler: Not 85. If you guessed 80, you win. (And for those playing along at home, the remaining initial values: 60 for the 60, 70 for the 70, 75 for the 75, 85 for the 90, and 100 for the 100.... one of these things is not like the other...). (Note: My reverse engineering also confirms what the engineer told me above.)
Let's stop beating this dead horse and get over it. Tesla lies, and they lied about the 85 capacity. Still love the products, hate the company.