Investigating an influence of temperature and relative humidity on the electrical performance of lithium polymer ion battery using constant-current and constant voltage protocol at small scale for electric vehicles

Lithium-ion batteries suffer from insufficient electrical performance due to the unpredictable thermal effect and dynamic behaviour during the charging and discharging process. However, the comprehensive impact of relative humidity (RH) on the charging process rate has yet to be investigated. In this paper, a set of experimental tests is implemented to investigate the charging and discharging thermal and electrical behaviour of lithium-ion batteries represented by a single-cell 1000 mAh and battery pack 2200 mAh. The charging process is employed using the constant current-constant voltage (CC-CV) protocol, according to the safety specifications of the manufacturer. The proposed scenarios applied in this paper are initiated by investigating the behaviour of the charging current, total interval time, and battery terminal voltage whilst varying the ambient temperature between 30°C and 40°C at a fixed RH of 52%. Then a set of experiments are conducted by changing the RH conditions (35%, 52%, and 70%) at a fixed ambient temperature of 40°C. Finally, the impact of changing the RH at a fixed ambient temperature during the charging process is scrutinized. The results of the investigations of lithium-ion battery charging behaviour reveal that charging at low RH ensures the fastest charging rate response using the CC-CV protocol. At low RH (35%) the charging interval time is reduced by almost 23% corresponding to high RH (70%).