# Start-Stop

> System that switches off the engine at stops (traffic lights) to save 5-15% fuel. Requires EFB or AGM battery.

**Categoría**: Vehicle features
**URL canónica**: https://baterias.com/gb/battery-glossary/start-stop
**Idioma**: en-GB

## Definition

Start-Stop is a system that automatically switches off the engine when the vehicle is stationary (traffic light, traffic jam) and restarts it instantly when the brake is released or the clutch is pressed. It saves **5-15% fuel and CO₂** in urban driving. It was introduced in mass production by BMW (EfficientDynamics, 2007), Mazda (i-stop, 2009), Toyota (Stop & Start) and Volkswagen; today it equips more than 90% of new European passenger cars. It subjects the battery to **hundreds of starts per day** (versus around 10 for a car without Start-Stop), which destroys a conventional SLI battery within months. That is why it requires either **EFB (basic Start-Stop)** or **AGM (Start-Stop with regenerative braking)**. The ECU continuously reads battery SOC and SOH; if the battery is degraded, it disables the system. NEVER replace a Start-Stop battery with a conventional one — besides premature failure, the vehicle electronics may register fault codes and reduce performance.

## See also

- [AGM (Absorbent Glass Mat)](https://baterias.com/gb/battery-glossary/agm)
- [EFB (Enhanced Flooded Battery)](https://baterias.com/gb/battery-glossary/efb)
- [Regenerative braking](https://baterias.com/gb/battery-glossary/regenerative-braking)
- [MHEV (Mild Hybrid Electric Vehicle)](https://baterias.com/gb/battery-glossary/mhev)

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