Maxwell Technologies has signed a memorandum of understanding with Valeo, a Tier 1 supplier to automakers worldwide, covering a development collaboration to incorporate Maxwell's Boostcap ultracapacitors in Valeo's next generation StARS+X -- "stop-start" and regenerative braking system. The 14+X StARS (starter alternator reversible system) consists of a reversible starter-alternator, a multi-cell ultracapacitor energy storage module and other power and control electronics in a 14-volt architecture that enables standard gasoline and diesel engines to shut down during idle phases and restart instantly, eliminating fuel consumption and emissions anytime the vehicle is stopped. Valeo estimates that the system can reduce fuel consumption and associated emissions by about 12 percent in normal operation and more than 20 percent in stop-and-go urban traffic.

The first generation StARS with start-stop capability, which did not include a dedicated energy storage component, initially was offered in certain European passenger car models in 2004. The new 14+X architecture incorporates enhanced electronics and an ultracapacitor energy storage module that allows it to recuperate and store energy from braking, which otherwise would be dissipated as friction and heat in a conventional braking system. The recovered energy is then available to power peak electrical loads such as de-icing and rapid cabin and seat heating and cooling, avoiding increased fuel consumption for such functions.