In 2015, about one in every 150 cars sold in the U.S. had a plug and a battery. But mass adoption of electric vehicles is coming, and much sooner than most people realize. In part, this is because electric cars are gadgets, and technological change in gadgets is rapid. One big leap is in batteries. A typical electric vehicle today costs $30,000 and will go about 100 miles on a charge, if that. Within a year, you’ll be able to get double that range for just a little more money. Tesla Motors Inc. TSLA -0.44 % is the standard-bearer, promising a Model 3 vehicle meant to appeal to the masses at $35,000 without incentives and more than 200 miles of range. By comparison, the average new car in the U.S. today sells for about $33,000 . But Tesla is hardly alone. Later this year, Chevrolet will roll out its […]