Since we have you speaking about batteries already, any theory on the chemistry of the elusive BTX7 battery that comes with the BR05 upgrade code?...As for the 75s, my speculation is that they've returned to using a cell chemistry closer to that of the original 85s, as the 90/75 cells do not hold up on the longevity side as well as the 85-type chemistry. The 100-type seems to not be the same as the 75/90 and is holding up significantly better. So, my guess is that newer packs have the 100-type cells, and Tesla is now comfortable with taxing these more than the original 75/90 type cells in the smaller pack versions...