Electric Axle Sizing for the Conversion of a Conventional Production Vehicle to a Prototype Battery Electric Vehicle

The “Car of the Future” project converted a production 2015 rear-wheel-drive (RWD) Subaru BRZ into a series hybrid electric vehicle (HEV) with an intermediate milestone of a battery electric vehicle (BEV). This intermediate BEV step provided a point at which the vehicle could be evaluated in its all-electric operation with the absence of what were once critical components, including its original powertrain and powertrain electronics. This paper selects an appropriate electric machine that will meet the desired requirements for the “Car of the Future” BEV milestone. Vehicle technical specifications (VTS), which define critical vehicle requirements, were provided by the sponsor and adjusted to align with common requirement criteria such as acceleration and gradeability. These VTS are based on the performance of the original production vehicle, which includes acceleration time from 0 to 96.5 kph (0 to 60 mph) in 6.3 seconds, acceleration from 80.5 to 112.5 kph (50 to 70 mph) in 10 seconds, and maintaining a speed of 96.5 kph (60 mph) while driving on a grade of 10%. The minimum power required was determined to be 119.9 kW, which is driven by the 0-96.5 kph (0-60 mph) acceleration time requirement of 6.3 seconds. After reviewing available electric machines, a McLaren Engineering E-Axle was chosen for its all-in-one package unit that met the VTS requirements. The predicted performance of this E-Axle against the defined VTS parameters showed that the E-Axle would meet or exceed the VTS.