Berlin (dpa) — Many still see range anxiety as the biggest obstacle to the rise of electric cars. Mercedes has designed an extremely energy-efficient car that may help allay the fear of running out of battery mid-journey. The Vision EQXX is a concept car that won’t be entering series production but some of its technology is bound for normal road cars. The German manufacturer didn’t take the easy option when aiming to save energy. Instead of simply installing a particularly large battery, they tightened all the screws to reduce energy consumption, from aerodynamics and weight to the battery, dr…