Ok, now I'm not so sure it is just a change in how they calculate the range. During the media call:
ELON: "We do find ways over time and have done this many times in the past where we are able to improve the efficiency of say of the drive inverter or the motor or we get a bit more comfortable with what how much energy you can extract safely from the battery pack without causing it long term harm. And so as we get more road validation and we are we're able to find optimizations and a feel a bit more comfortable widening the margins. And then we just update the car and make it better for free."
I was just about to go pull that quote as well..
Either Elon is just blowing smoke about what is possible, not what is ACTUALLY happening, or we take him at face value on these statements.
I can think of three speculative ways that Tesla could have adjusted the firmware to truly increase the range of the car.
A)The drive inverter and/or motor could by tuned in software to use less energy than before during certain driving scenarios Perhaps it is possible to run it with less current, or with more efficient timings, but with the potential for drive unit issues; they've now defined a new range for tolerances based on road validation.
B)They could have limited the packs because they didn't know how much range degradation to expect long term on the new 2170 cells. They locked more of the pack than necessary in case of the event that cells degraded faster than expected, so they could mitigate the issue. Now road validation is showing that cell reliability and resilience is proving to be either better than expected, or as expected with no unexpected issues after long term road validation. They can now unlock an extra kwh or two based on the current battery statistics.
C) What is considered 100% in a li-ion cell is to some degree variable, perhaps they considered 4.17v the maximum voltage for a cell, but now through road and longer term validation, they consider 4.21 the maximum safe voltage of the cells, resulting in more power being allowed to be placed in the cells.
Remember that 325 vs. 310 miles range is only a 4.8% difference. It does not seem extremely out of the realm of possibility that through firmware adjustments to the motor and battery pack range could have been improved this small measure. (heck they could probably get a 4.8% improvement by tuning the heater and AC power limits under some driving conditions.)
The fact that the range increase is coming at the same time as a 5% performance improvement makes me lean on the side that they've actually just tuned up the firmware for a lot of the cars systems after a lot of road validation and there truly is additional range being added above and beyond just adjusting the rated range in the HUD.