stopstart

Stopstart is an automotive technology that automatically shuts off the internal combustion engine when a vehicle is stationary and restarts it when movement resumes. Also referred to as idle-stop or start-stop in some contexts, it is designed to reduce idling fuel consumption and emissions in urban driving. Stopstart systems are common in modern city cars and in mild-hybrid architectures, and they are distinct from full-hybrid propulsion.

The system activates under predefined conditions: the vehicle is stationary, the brake is applied, the transmission is in drive or neutral, the engine is at operating temperature, and the battery has sufficient charge. When these conditions are met, the engine is shut down to idle. When the driver releases the brake or presses the accelerator, the engine restarts automatically. Restart times are typically within a fraction of a second to minimize disruption. Some implementations also integrate energy recovery or use an electric motor to assist restarting.

Hardware configurations vary. A simple stopstart setup can use a dedicated starter motor and a conventional 12-volt battery, but many applications employ reinforced batteries (EFB or AGM) or a 48-volt mild-hybrid system with a belt-integrated starter generator or a small electric motor. The 48-volt variant can also provide limited electric drive and regenerative braking.

Benefits include improved city fuel economy and reduced CO2 emissions, typically at modest cost and weight penalties. Limitations include potential wear on batteries and starters, restart smoothness concerns, and reduced effectiveness in cold weather, with high climate-control demand, or when the battery charge is low. Some drivers may perceive the restart timing as jarring, an issue mitigated by improvements in control software.

Stopstart has been widely adopted in Europe in response to vehicle efficiency targets and regulatory pressures and is increasingly used elsewhere as automakers pursue fuel-saving gains.