I suspect that fleets may find it advantageous to exchange tractors rather than change batteries. OO's aren't on the road 24 hours, and so charging infrastructure at rest stops may address that problem. I don't see the need for a standard battery pack, but a standard charging inductor or connector is key. Another point is that the roof of a 45 ft trailer offers enough space for an 8KW solar array, which can add range in some applications. Long haul electric is barely viable today, but the path for improvement is clear.