The Tesla pack energy density
The Tesla pack energy density continue to improve. in 2021 they were at 186 Wh/kg, so we can assume it'll be over 200 for the Semi. That means a 500 mile pack shouldn't be more 5000 kg or 11000 pounds. How much they'll need to make the rest of the semi is yet to be seen, but I'm sure that'll be one of the first thing we learn when they hit production.