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Valeo Stop-Start Starter/Alternators - 20 Years of Technology

Valeo stop-start StARS
The technology behind the Valeo stop-start StARS system is built on precision and efficiency, ensuring that the engine shutdown and restart processes are seamless and imperceptible to the driver and passengers.


The automotive industry is continuously evolving, with a strong focus on developing technologies that enhance fuel efficiency and reduce environmental impact. One such innovation that has gained prominence is the Valeo stop-start StARS (Starter Alternator Reversible System) which has been in production for 20 years in 2024. This advanced system goes beyond the capabilities of standard alternators, offering an intelligent approach to managing a vehicle's power supply and reducing fuel consumption. As the first of its kind, and seamlessly stopping and restarting the engine when necessary, the Valeo stop-start StARS system transformed the way vehicles operate, paving the way for a more sustainable and economical driving experience and becoming a real game changer in the automotive industry.


Why is the Stop-Start system so important?

Driving in towns and cities, vehicles are stationary for nearly 35% of the time (traffic jams, red lights…), with their engine’s idling needlessly. The Stop-Start system automatically switches off the engine when the vehicle is at a standstill and restarts the engine immediately, as soon as the driver lifts his foot off the brake or disengages the clutch, leading to a significant reduction in CO2 emissions and fuel consumption, something every vehicle manufacturer applies heavy focus on!


Valeo StARS - Built for comfort!

The technology behind the Valeo stop-start StARS system is built on precision and efficiency, ensuring that the engine shutdown and restart processes are seamless and imperceptible to the driver and passengers. This seamless operation is made possible through real-time monitoring of the vehicle's status, such as the position of the accelerator pedal, the engagement of the clutch or brake, and the battery's charge level. By leveraging these inputs, the system can make informed decisions about when to shut off the engine and when to restart it, optimising fuel consumption without sacrificing performance or comfort.




The Evolution of Stop-Start Systems Lead by Valeo

The concept of stop-start alternators has gained significant traction in the last two decades, from when the first system (StARS) was produced by Valeo in 2004, and is continually being driven by the need for more environmentally friendly and fuel-efficient automotive solutions. As well as the StARS system, Valeo are the only manufacturer to pioneer and offer three other different solutions for OE and the Aftermarket:

The Valeo i-StARS system represents a paradigm shift in automotive technology, harnessing the power of advanced start-stop functionality to optimize vehicle performance and environmental conservation. At its core, the system employs intelligent energy management, seamlessly orchestrating the start-stop process to deliver unparalleled efficiency. Through a combination of sophisticated sensors and real-time data analysis, the Valeo i-StARS system anticipates the driver's actions, seamlessly restarting the engine with remarkable precision and speed in one combined unit with the original external ECU now incorporated. The i-StARS+ version is a seven-phase design, making it extremely quiet, giving it best-in-class noise performance and reduces CO2 and fuel consumption significantly.



This reinforced starter provides the extra durability needed for repeated stopping and starting when the vehicle comes to a complete standstill. ReStart has minimal impact on engine architecture and can be applied to a variety of engine types and displacements. The ReStarter with Permanent magnets inductor has less weight and is of a smaller size compared to a standard starter motor. The Restarter with wound filed inductor uses permanent magnets with heavy strip copper windings, wound around iron pole shoes that are fastened to the yoke. The resistance of the field and armature windings is low but the current flow is high when the motor starts under load, generating a strong magnetic field that produces a high turning effort at low speeds. ReStart also contains shock absorbers a “split solenoid” function and self-synchronized pinion.




At the forefront of the 48 Volt voltage revolution is the Valeo 48 Volt i-BSG (Integrated Belt Starter Generator, a compact) and powerful system that brings together the functionalities of both a starter and generator – the first of its kind. Its technical prowess lies in its ability to efficiently and seamlessly manage the electrical needs of modern vehicles.


This powertrain system, is on average 20% more affordable than high-voltage motors (60 Volts and greater), thanks to a simplified architecture that reduces safety equipment requirements. The i-BSG also produces 5% fuel savings with increased comfort and power compared to 12 Volts stop-start system.



The Stop-Start technology's seamless integration with the vehicle's electrical architecture, along with its ability to reduce CO2 emissions, improve fuel consumption and now, with its ability to recuperate energy during braking and deceleration, positions it as a catalyst for sustainable mobility solutions. As industries and applications across the automotive spectrum embrace the Valeo Stop-Start technologies, its impact reverberates across passenger vehicles, commercial fleets, and diverse mobility platforms, contributing to a more eco-conscious and refined driving experience. With ongoing advancements and potential developments on the horizon, Valeo Stop-Start systems stand poised to shape the future of sustainable mobility, setting new benchmarks for efficiency and environmental responsibility within the automotive industry.