48 Volt Mild-Hybridization and its Impacts on CO2 Emissions

Tough regulations for emission reduction force OEMs to develop and introduce highly efficient vehicle concepts. Drivetrain electrification represents one of the main measures for reducing the fuel consumption of passenger vehicles. Mild-hybridization based on a voltage level below 60 V is a promising alternative to cost-intensive high voltage powertrains. The objective of this study is to investigate the belt-driven starter/generator architecture for its CO 2 emission reduction potential within different driving cycles. In order to evaluate the CO 2 emission reduction potential resulting from 48 V mild-hybridization, a complete vehicle simulation model was built up. Key components like internal combustion engine and electric motor were parameterized with characteristic diagrams, representing the efficiency of each operating point. Different hybrid functions were implemented in the simulation model. The superior operation strategy was designed in dependence of the battery state of charge (SOC). This study shows the influence of different driving cycles, electric motors and transmission types on the CO 2 emissions, focusing on a 48 V P0 mild-hybrid vehicle. Additionally, the impacts of different hybrid functions on the emissions are shown. It was demonstrated that load shifting can have negative effects on the cumulated fuel consumption, depending on the given loss chain. Finally, deductions for the development of 48 V mild-hybrid systems are drawn. The identical vehicle without drivetrain electrification was selected as comparison base.