For future vehicles, the 42-V power system offers a variety of new applications, from the capability to sustain increased comfort loads up to mild hybridization. To meet these requirements, considerable progress is needed for the lead–acid system to achieve reasonable lifetime and reliability in service. In addition to cycle-life improvement at partial state-of-charge, both a state-of-health indication and a battery management system with sophisticated algorithms to achieve sufficient cycle-life are required. Due to the inherently lower cost of lead–acid, only a slow migration towards more advanced battery systems is anticipated. Some applications for nickel–metal-hydride and Li-ion batteries are discussed.