I think Rivian will take the startup approach and pack as much density into their battery, even if it means sacrificing a large chunk of their margin. The r1t is supposed to have a weight of 8500 pounds[0], so I can see a 150-200kwh battery being packed in there on the Max pack to achieve that range.
That's the gross vehicle weight rating, which is the max weight of the vehicle including cargo. The R1T has a curb weight of ~7,000lbs[0] with the 135kWh battery. That is still as much as a Dually F-350. The 180kWh option would be heavier still and start eating into the payload capacity.
Yes, it's probably necessary if they wanna get near-400 miles on extended range. Even the F150E with extended range only has a 300 mile EPA with estimates of 170kwh[0], and the r1t doesn't look to be insanely more aerodynamic. It's indeed going to be a disaster, but Amazon wants a foot in the door regardless of how much it costs.
