A comparative investigation on the energy flow of pure battery electric vehicle under different driving conditions

Abstract

The battery electric vehicle (BEV) shows great potential in energy security guarantee and harmful emissions reduction resulting from road traffic increasing. The energy consumption characteristics and operation status of key components under different driving conditions have great impacts on the performance of EVs. However, studies on its variations under different driving conditions over the entire driving distance are limited. In this study, the BEV energy flow characteristics, energy loss, working conditions, and efficiencies of key components under the New European Driving Cycle (NEDC), Worldwide Harmonized Light-duty Test Cycle (WLTC), China Light-duty Vehicle Test Cycle (CLTC), and a constant speed of 120 km/h were comparatively investigated using a chassis dynamometer. The test results revealed that the power consumption rate at 120 km/h was much higher than those under other driving cycle conditions. The increased ratios of the power consumption rate under 120 km/h over NEDC, WLTC, and CLTC were 27.1 %, 16.5 %, and 26.3 %, respectively. However, the energy utilization of the BEV under 120 km/h is much higher than that under other conditions, owing to the relatively high efficiency of the working points and the lack of brake energy consumption. The proportions of motor and motor control unit (MCU) losses under NEDC, WLTC, CLTC, and 120 km/h were 28.8 %, 27.5 %, 32.3 %, and 9.1 %, respectively. The power battery losses under NEDC, WLTC, CLTC, and 120 km/h were 5.4 %, 4 %, 4.8 %, and 1.3 %, respectively. The working efficiencies of the direct current (DC)/ DC and front and rear electric drive assemblies under the WLTC, NEDC, and CLTC conditions were less than 80 %. This study thoroughly demonstrates how driving conditions influence energy flow distribution and the operational state of critical components in BEVs. It provides a significant reference and foundation for the future optimization of BEV performance and energy consumption.