Research on Factors to Influence Coasting Resistance for Electric Vehicles 2020-01-1068
The research on coasting resistance is vital to electric vehicles, since the smaller the coasting resistance, the longer the coast-down distance. Vehicle resistance consists of rolling resistance, vehicle inner resistance and the aerodynamic drag. The vehicle inner resistance is mainly caused by driveline’s friction loss and oil splash loss. The rolling resistance is decided by tire resistance coefficient, which is influenced by tires and road conditions. And the aerodynamic drag is affected by vehicle’s shape and air. In this paper, four factors that are tire pressure, road surface condition, air circulating mode, and atmosphere temperature are examined. Experimental tests have been conducted on three different vehicles: one subcompact sedan, one compact sedan and one compact SUV. The outcome shows that, when the tire pressure is 20% less, the average coasting resistance is increased by 1% to 3% depending on vehicle types, which indicates an increase in energy consumption by 0.9% to 2.4%. On wet road surface, the average coasting resistance is increased by 10% - 20%, which could decrease the NEDC range by 6% to 12%. And vehicles at inner air circulating mode experiences an average 5% reduction in vehicle resistance than those at outer air circulating mode. With atmosphere temperature in 5 to 35°C range, the resistance is decreased by 0.48% for every 1°C increased. All three vehicles show the same trends. The overall results give a better understanding on how the coasting resistance is influenced by various factors and can instruct future vehicle’s low coasting resistance development. More factors such as brake calipers, tire size, and other corresponding influences will be studied in future tests.