Japan’s nonstop search for best stop-start system

Suppliers and carmakers are trying out competing energy-storage systems to power the fuel-saving engine stop-start systems that are increasingly common on vehicles. In Japan, automakers are working with lead-acid, lithium ion and nickel-metal hydride batteries, as well as capacitors. Each has pluses and minuses. The industry is still juggling cost against safety and performance. But the technology is already delivering better fuel economy.
Toyota Motor Corp., Honda Motor Co., Mitsubishi Motors Corp., Mazda Motor Corp. and Suzuki Motor Corp. are introducing vehicles that shut down the engine when the car comes to a stop. The move saves petrol but requires beefed up batteries to run the radio, navigation, air conditioning and other electronics while the engine is disengaged. When the driver lifts up on the brake pedal, the engine fires up again and is ready to go. The technology is popular in hybrid vehicles, which already have big batteries to store power and have regenerative braking systems to recharge those batteries when the car slows down. But the stop-start systems are migrating to traditional petrol-powered cars. Those cars typically need more electricity storage than the standard 12-volt battery.