48V-CityRoadster – Safety Extra Low Voltage Traction in the Stuttgart Metropolitan Area

Basic passenger cars with SELV (Safety Extra Low Voltage) traction drive are a promising – but barely investigated – alternative for emission-free individual mobility in urban metropolitan areas. 48V traction is often associated with light vehicles and therefore is considered as unattractive, unprestigious and unsafe. To dispel these prejudices, the 48V research group of the Esslingen University of Applied Sciences has electrified an appealing Youngtimer (BMW Z3) with SELV and reached the BEV (battery electric vehicle) registration for public roads. Despite the limited traction power of about 20 kW, a Twin-Motor with free-wheel and three-speed transmission achieves a comfortable, dignified and save mobility. To limit the empty weight to 1200 kg, the battery range is restricted to 60 km, an optional range extender battery increases the range to 90 km.

This contribution describes the setup of the 48V-vehicle, the longitudinal dynamics model in Matlab/Simulink as well as the comparatively low costs for conversion and maintenance from the vehicle service point of view. The traffic benefit is elucidated by real load cycles in the Stuttgart metropolitan area in comparison to modern series BEV with high voltage as well as in comparison to different combustion motor driven cars.