There is a theoretical, magic tipping point for adoption of electric vehicles. Once somewhere between 5 and 10 percent of new car sales are all-electric, some researchers say, huge numbers of drivers will follow. They predict that electric car sales will then soar — to 25 percent, 50 percent and eventually to close to 80 percent of new sales. Early adopters who love shiny new technologies will be replaced by mainstream consumers just looking for a…