Why not add larger batteries? The energy stored in a battery is measured in kilowatt-hours (kWh). The energy stored in a gallon of diesel is equivalent to 37.85 kWh stored in batteries. To store the same amount of energy contained in the 200 to 300 gallons typically carried aboard a semi would require 7,570 to 11,355 kWh. Since electric motors are about three times more efficient than diesel engines, only about 2,523 to 3,785 kWh would be required to equal 200 to 300 gallons of diesel. For reference, the lithium-ion battery in the Freightliner eCascadia is rated at 550 kWh.
Using the best-state-of-art lithium-ion battery technology, the above batteries would weigh about 18,500 to 27,800 pounds. In comparison, 200 and 300 gallons of the diesel weighs about 1,400 to 2,000 pounds, so an electric 18-wheeler would carry 17,100 to 25,800 pounds less payload than a comparable diesel truck.
Time to recharge is a killer. Compared to the about 15 minutes it takes to tank up with diesel, recharging a huge battery in a semi would take many hours. Normally, lithium-ion batteries are charged from 10% to 80% state-of-charge (SOC). Letting a battery discharge below 10% SOC can be hard on batteries and after 80% SOC charging can slow to a trickle. Assuming fast charging at 350 kilowatts, capability now being deployed, it would take 5 hours to recharge a 2,500 kWh battery for about 1,000 miles of range and 7.5 hours for a 3,750 kWh one for 1500 miles. If today, most of the 18-wheelers carrying vital supplies were electric powered, truck stops with charging stations would be long term parking lots.
The Hydrogen solution
Another way to achieve zero-emission trucking is to replace diesel engines with hydrogen fuel cells and diesel fuel tanks with hydrogen tanks. There is not big difference in weight so payload is not compromised. Nikola is offering both Nikola One battery-electric and Nikola Two hydrogen fuel cell semi tractor trucks, Anheuser-Busch has ordered up to 800 of the hydrogen semi trucks with first deliveries in 2020. Two prototypes are already delivering Budweiser beer. Nikola claims the Nikola Two has a range of 500 to 750 miles and can be refilled with hydrogen in 10 to 15 minutes. Kenworth and Toyota are developing 10 zero-emissions Kenworth T680s powered by Toyota hydrogen fuel cell electric powertrains that will be used at Port of Los Angeles.
The downside to hydrogen fuel cells is the current lack of a refueling infrastructure. Today, there are only 47 hydrogen stations, of which 42 are in California. This compares to about 25,000 electric charging station across the U.S. Nikola is planning to build 7000 hydrogen filling stations to support its fuel cell OTR trucks. It doubtful that an investment in a hydrogen infrastructure that parallels the electric one will be made in the near future. Thus, hydrogen fuel cell trucks will be used mainly on dedicated routes, leaving the diesel to make deliveries everywhere deliveries have to be made.