A Suggestion Towards Improving Electric Vehicle Fast Charging

Fast charging of electric vehicles is considered a key step to improve the market receptivity of electric mobility. However, fast charging poses new development challenges, as traction batteries need to be able to handle the high charge current and the thermal management system is required to control excess heat caused by the charge current and the internal resistance of the battery. Based on the requirement of high charging powers, that are currently approaching 350 kW, the excess heat must not rise any further due to the limitations of the thermal management system and the resulting safety issues of an overheating battery. The constant voltage-constant current (CC-CV) charge algorithm is currently considered the standard charge protocol, but this research indicates that a change of this protocol should be performed in order to improve fast charging. This work focusses specifically on the boost-charge (BC) protocol, which has been tested against the CC-CV protocol and proven to be able to reduce the charge time by around 7 %, while not causing a significant temperature increase of the battery cell. Due to charge rate limitations specified by the cell manufacturer of the tested cell, not all desired charge tests could be performed. Therefore, a Simulink simulation was developed and verified, in order to make predictions about further improvements of the protocol as well as the application of higher charge currents. Based on these findings it is suggested to further research different charge protocols to improve fast charging.