Let’s look at some numbers.
A diesel engine for a semi weighs in at between 2000 and 3000 pounds. The horsepower ranges from 250hp to over 600hp. Torque ranges from 1000 ft-lbs to over 2000 ft-lbs. Fuel ranges from 100 to 400 gallons of diesel weighing from 715 to 3000 pounds.
The Mack Trucks MP-8 engine is a 13 liter 415-485 horsepower engine with 1540-1700 ft-lbs of torque.
Now, if we can get a 3000 pound electric motor that produces 400 hp @ 1750 rpm and develops 1200 ft-lbs of torque (and we can), then that leaves some 700-3000 pounds for batteries.
The Tesla roadster has a 200hp motor and can go over 200 miles on its 53 kWh (750 lbs) battery pack.
If we scale that up to a rig, then we can get 159 kWh in 2250 lbs worth of Li+ batteries. This should give about the same range of travel. Taking in to account the fact that the truck is pulling way more weight, but it also has a transmission that can handle the power and torque so we can still have the benefits of an efficient engine speed for vehicle speed.
I’ll freely admit that’s a heck of a lot of battery. But I think that it’s doable and a reasonable compromise, especially for mostly local freight hauling (like from a warehouse on the outskirts of the city, to the stores inside the city).
As I’ve said, I think that hybrids are the worst of both worlds. You get modest improvements in gasoline efficiency in exchange for excessively complex internals and lower overall power.
Here’s one company that’s working on this. Again, short and medium haul applications would work great for this. If you place the battery packs in the same place and the standard deisel tanks, then it should be pretty easy to swap them out between runs.