Tire and Aerodynamic Friction and MotorDriveline Efficiency of Electric Vehicles from Track Tests

Tests of seventeen electric vehicles were analyzed to estimate tire friction, aerodynamic drag-area product, and average motor-driveline efficiency. The tests included coastdown runs, range over the SAE J227a driving schedules (B, C, and constant speed), and constant-current battery discharges. Analysis indicates that winds during coastdown tests resulted in average standard deviations of seven percent for tire friction, and fifteen percent for drag-area product. Motor-driveline efficiency estimates ranged from 40 percent to 93 percent (fifteen vehicles, J227a/B schedule), and from 61 percent to 93 percent (eleven vehicles, J227a/C schedule).