Gasoline Cars Get a Mileage Jump-Start

One of the ways hybrids achieve big efficiency gains is through something called a start-stop system: When a Prius rolls to a halt, so does its engine, saving fuel and boosting miles per gallon. The car’s advanced battery keeps the lights on and the stereo buzzing until the pedal is pressed and the engine restarts.

In the U.S. that kind of efficiency gain hasn’t been available in regular cars because their lead-acid batteries would go dead in months if they had to restart the car so often. But new federal efficiency standards are encouraging automakers to wring every mile out of a gallon of gas, and a battery design from Johnson Controls, the Milwaukee-based industrial giant that makes a third of all auto batteries, will help. The company is currently retrofitting a factory west of Toledo to begin making its advanced batteries, which will power start-stop systems in conventional autos beginning next summer.