20 years of Stop-Start system: from pioneering innovation to market standard

“If I had to briefly describe Stop-Start, I would say it’s just common sense,” says Ulrike Sinner, who was in charge of marketing and external communications for the Valeo division that worked on stop-start development. “Just as we don’t leave the light on when we leave a room, why should the engine stay on when the vehicle is stationary? All the more so in city traffic, when the vehicle is stationary around 35% of the time. It was on the basis of this simple idea that Valeo engineers came up with the stop-start concept”.

 “At that time, electrification was just at the beginning, with the launch of the Prius from Toyota in&nbsp,1997. However, this solution was still expensive,” reminds Claudine Rochette, in charge of strategy and communication at Valeo Power. “That’s why Valeo decided to launch this new affordable solution, with a pragmatic approach, given its leadership on starters and alternators. This is how the Stop Start was born.”

Daniel Richard, who at the time was head of the R&D team working on stop-start, recalls the enthusiasm of the engineers who brought this innovation to life. “At the beginning, in 1997 and 1998, there were just a few people in the team, maybe 10 or 15. They were the heart of the development, not only because they had the knowledge and eager to learn even more, but also, and most of all, because they were passionate. When I arrived in the morning at the office, the site guard would come to me in a panic and say, “Your teams broke into the site in the middle of the night to work in the lab!” It was an incredible human adventure and obviously one of the best memories from my professional career.”

From the simple idea to its realization, the challenge was immense, starting with the introduction of electronics into mechanical engineering. Ulrike Sinner explains, “To combine the alternator and starter, as we achieved with the Stop-Start, you need very sophisticated electronics in the machine. You might say it’s very common and very easy. We have it in our smartphone, in our computer, it’s everywhere. Yes, of course. But this is more challenging on an alternator which is piloted as a motor, under the hood of the engine, which is turning at 6,000 RPM, at 120°C, vibrating, having shocks, a lot of dust… and including innovative power electronic rated at a few hundreds amps. So that was the challenge. Not only to integrate it into this environment, but also to achieve reliability and cybersecurity.”

Stop-Start automatically switches off the engine when it is at a standstill, enabling significant reductions in CO₂ emissions and fuel consumption. Around a 5% reduction was calculated at the time on official combined cycles. And even more in the urban cycle, as Ulrike Sinner reminds us. “We took two identical cars equipped with stop-start, but one car had it turned off, and in the other it was activated,” she explains. “At the end of a three-hour test drive in Paris, we went to the fuel station to compare the difference in terms of refuel. We had an official legal officer who could state that our Start-Stop system in the city has a real fuel saving of 35%”.

The first two vehicles to be equipped were the Citroen C3, in 2004, and then the Smart Mild Hybrid. However, “It took some time for the stop-start system to catch on,” says Claudine Rochette. “But now the stop-start function is used by everyone, is known by everyone, and it’s in every car all over the world. The stop-start was the first big move of Valeo into electrification. And 20 years later, Valeo is engaged more than ever in the electrification of mobility”.