As automobile emission standards are strengthened, the demand for eco-friendly vehicles is increasing. According to a study by the Automotive Thermal System market in 2021, the number of electric vehicles is expected to reach 27,536 thousand by 2030, with an average annual increase of 28.4% from 2021. Growing demand for eco-friendly vehicles is boosting thermal management system market, set to reach $49.98 billion by 2026. Various studies are being conducted on the thermal management system to maximize the efficiency and performance of key components by maintaining their temperature, aiming to improve the range and battery life of electric vehicles. In this study, the driving characteristics of an electric vehicle were analyzed by driving the Combination US06 mode according to the SOC state(100, 70, 50%) under temperature conditions of normal temperature(25℃) and low temperature(-7℃) in a vehicle dynamometer. Driving data of electric vehicles were acquired through CAN Bus. The air conditioning system was not used under room temperature conditions, and the heater was set to the maximum temperature and fan speed (27℃, 8th level) under low temperature conditions. The Combination US06 mode consists of UDDS1-UDDS2-HWFET-US06 mode sequences, with 10 minutes of soaking between UDDS1, UDDS2 and HWFET modes, and a 15 second stop between HWFET and US06 modes. As a result of the test, the energy efficiency was highest in the UDDS1, UDDS2, HWFET, and US06 modes in normal temperatures tests. The UDDS mode has the best energy efficiency because it drives at a lower speed than the HWFET mode, which has less impact on air resistance. Additionally, the US06 mode has more than twice the amount of energy recovered due to frequent braking despite having a similar average speed to the HWFET mode, but had lower energy efficiency due to the high battery consumption caused by sudden acceleration and deceleration. On the other hand, in the low temperature test, the energy efficiency was high in order of HWFET, US06, UDDS2 and UDDS1 modes. Unlike normal temperature, the major reason for high energy consumption in the UDDS1 mode was the use of a heater to raise the indoor temperature at the beginning of the test. During the test, soaking for over 16 hours was conducted under SOC 100% conditions at both normal and low temperatures, while for SOC 70% and 50% conditions, the test was conducted after a 2 hour soaking period. It was determined that soaking had little effect on the normal temperature test, but in the low temperature test, the indoor temperature and the initial temperatures of the motor and components were not set to be the same, resulting in a 20% lower energy consumption during the UDDS1 test compared to the test that soaked for over 16 hours. In many previous studies, each test accroding to single-mode driving, such as UDDS, HWFET, US06 and SC03 modes, was analyzed, but this study was analyzed through Combination US06 mode, which is one of the electric vehicle 5Cycle test methods introduced in SAE-J1634 in 2021. In addition, the study aimed to evaluate the energy efficiency of electric vehicles based on ambient temperature and SOC state using a chassis dynamometer, and conducted research on driving characterisitcs according to each influencing factor. This study aimed to analyze the driving characteristics of an electric vehicle in a low temperature. The analysis was conducted on the chassis dynamometer under SOC conditions of 100, 70, 50% at both normal and low temperatures. The conclusions are as follows: (1) The SOC conditions applied during the test did not have a significant impact on the electric vehicle`s performance. (2) A significant increase in energy consumption was observed due to the air conditioning system during the low temperature test compared to the normal temperature test. Additionally, the low temperature test showed approximately 25~30% higher energy consumption and 25% lower regenerative braking than the normal temperature test.

Mr. Gwangryeol Lee, Student, Konkuk University