We test an electric Mercedes that can can go 747 miles on a single charge

IMMENDINGEN, GERMANY—Driving off in the Mercedes-Benz Vision EQXX was slightly more stressful than I anticipated. Not that it's difficult to drive, or to see out of the low-slung streamliner, but it's also the only one in existence. Mercedes wouldn't tell us the program's exact budget, simply warning us that the sole EQXX should be considered priceless, but I'd guess somewhere in the range of three Bugatti Pur Sports.

Like the Bugatti, the EQXX was built to an engineering brief—in this case to build an electric vehicle capable of at least 621 miles (1,000km) on a single charge. Also like the Bugatti, it's road-legal: in April of this year, less than two years after the project was given the green light, the team drove the EV 625 miles (1,006 km) from Sindelfingen in Germany to Cassis, France, arriving with a 15 percent state of charge in the battery.

Two months later, they followed that up with a longer drive that involved descending down fewer mountains, driving from Stuttgart, Germany to the Silverstone racetrack in the UK, where reigning Formula E champion Nyck de Vries then used the remaining charge to drive some hot laps, the car eventually completing 747 miles (1,202 km) before coming to a halt in the pit lane.