Getty ImagesYou could be forgiven for thinking that electric cars might finally be gaining momentum in the US. After all, sales of battery cars topped 1.2 million last year, more than five times the number just four years earlier. Hybrid sales have jumped by a factor of three.Battery-powered cars accounted for 10% of overall sales in August - a new high, according to S&P Global Mobility. And in updates to investors this week, General Motors, Ford, Tesla and other companies all reported record el...