Why EV Chargers Are So Expensive — And What To Do About It

Source: Wikimedia Commons

By Andrew Moseman

One of the challenges holding back electric vehicles in America is the lack of a robust network of high-speed electric vehicle (EV) chargers, the kind that can refill most of a car’s battery in a half hour or less. A big reason for the dearth of chargers is cost: A charging station with four ports costs a half-million dollars or more, according to a new article in IEEE Spectrum.

Caltech alums Wally Rippel (BS ’68) and Alan Cocconi (BS ’80), two crucial figures in the development of the electric vehicle and the authors of the article, know charging woes all too well. Rippel was part of the Caltech team that challenged MIT to a cross-country electric car race back in 1968. In the early 1990s, he and Cocconi cofounded AC Propulsion, a company whose work would influence the original Tesla Roadster. In their Spectrum article, the pair call out a specific engineering challenge that has driven up the price of fast chargers. As they explain:

“The time-tested way to prevent electric shock is to use electrical grounding. Grounding is exactly what it sounds like: a direct physical connection to the earth that provides a path for electric current. When such a path is present, stray electrical currents—in a chassis, for example—travel directly to the ground, avoiding any people who might be standing close by. In an electric car that’s charging, the green ground wire in the charging cable becomes the path to ground. (Because an electric car has rubber tires, the car itself can’t serve as a path.)

What happens if such a path is not present? If the ground connection in an electric car charger is broken or compromised, the charge port must have a backup solution. Today, that solution is something called galvanic isolation. In galvanic isolation, no direct conduction path is permitted between certain sections of an electrical system.”

The problem is that galvanic isolation is remarkably expensive to accomplish. By Rippel and Cocconi’s calculations, it accounts for more than half the cost of all the power electronics needed to make a charger. For a single 300-kilowatt charger, like one you might find at a new Tesla  Supercharger station, that amounts to more than $50,000.

The pair concludes that a much more affordable piece of hardware called a buck regulator could bring down this tremendous cost. Read the Spectrum feature here for their full explanation.