The two largest obstacles to making electric vehicles, especially big rigs, the dominating force in the market are range capacity and charging rates. But, there is a third you may have not even considered: heat generation.
When charging a small car into a standard 120-volt electrical socket, the car charges at a rate of about four miles per hour. That means if you were to drive it 100 miles, you would need to wait over a full day for it to become fully charged again. The problem is even worse in electric semi-trucks that charge at an average rate of less than one mile per hour when plugged into a standard outlet.
One solution that Tesla has come up with is to use specialized chargers that can carry electricity at rates much higher than a standard outlet. A Supercharger V3 would charge at 100 MPH and a Megacharger would charge at 800 MPH.
This faster charging sounds great, until you realize that a larger current running through direct current batteries means more heat is generated. Doubling the current quadruples the amount of heat generated. At best the increased heat will reduce battery capacity at a faster rate, and at worst it can cause battery fires that put the entire vehicle at risk of being destroyed.
The problem is compounded when vehicular fuel batteries are composed of thousands of smaller lithium-ion batteries, each one individually susceptible to causing a fire. This could be part of the reason why the Tesla Semi was delayed another year.
The best chance electric semi-trucks have is to find the optimal time for charging: as much time as possible and not a second less. By providing the electricity during the full seven or eight hours a trucker sleeps in the berth (depending on which Hours-of-Service regulations apply) a 500-mile battery charging at approximately 70 MPH can reduce the heat generated when compared to a Supercharger V3 by a large margin.
Other ways to deal with the heat is to increase the rate of dissipation (perhaps by maximizing airflow), or to make the batteries more heat resistant so they lose less charge when exposed to higher temperatures.
Whatever the method used to solve it, solving the problem of charging times for electric vehicles, cars and 18 wheelers alike, has only just begun.