Constant Current, Constant Temperature, and Constant Voltage Charging of EV Battery

ABSTRACT Charging at a higher rate increases the operating temperature of a battery pack, which affects the battery life. To improve battery life, lower operating temperatures can be ensured through an external cooling arrangement or the appropriate charging strategy selection. The present paper considers the case of charging at higher rate and reduced operating temperature through the strategy of constant current, constant temperature, and constant voltage (CC‐CT‐CV) mode. During CC mode, current at a higher rate is injected and ensures the temperature rise should not exceed the maximum allowable temperature of the battery. As the temperature reaches the set limit, the charging current is reduced smoothly to an optimized value, where heat generate by the charging current in battery becomes equal to heat release by battery in surrounding due the difference between battery's temperature and ambient temperature, resulting in temperature regulation of battery and being termed CT mode. The charging process is completed through CV mode to stabilize battery chemistry. The proposed charging strategy is demonstrated through cascaded control of temperature, voltage, and current control loop implemented for a 1 kW@48 V charger and validated for effectiveness.