Customer requirements such as range anxiety are the driver for increasing the charging power of battery-electric vehicles. High-performance charging theoretically enables time targets of faster than 30 kilometers (19 miles) recharging per minute. Due to physical limitations (i.e., current limits of the components available) a charging power of greater than 200 kilowatt arises the question of the voltage level required to fulfill the power demand. One possible approach to achieve high charging power is increasing the battery voltage, i.e., increasing the voltage level from 400 V to 800 V is one simple measure. This publication discusses the main aspects of charging by incorporating all high-voltage components in the vehicle. An increase of the voltage level and charging power affects all high-voltage components, especially the thermal management of the battery needs special consideration.
High-voltage vehicle architecture design considerations are discussed including thermal-management and battery-design aspects. Different charging curves from existing vehicles are compared with a generic fast charging profile which is defined using theoretical background of available cells including consideration of physical and chemical limits (e.g., thermal-limits, cell-degradation).
Additionally, high charging-power levels also require a consideration of the infrastructure available. Extending the technical point of view with customer values, the charging efficiency is regarded including the infrastructure. Furthermore customer acceptance and market forecasts are considered. A higher voltage level enables higher power also for other components in the vehicle, such as the electric drives, high-voltage heaters, compressors and voltage converters. To determine the optimum voltage level, for an example vehicle used in this publication, all those considerations are compared in the discussion. Focusing on the early development phase of a complete vehicle, a methodology for conceptual design considerations is discussed incorporating the high-voltage vehicle architecture and the battery from the thermal point of view.
Christian Josef Paar, Helmut Martin Waser, Heimo Kreimaier, Inés Cuenca-Jaen, Florian Eibler
Magna Steyr Fahrzeugtechnik AG & Co. KG