Study on the Relationship Between Open-Circuit Voltage, Time Constant And Polarization Resistance of Lithium-Ion Batteries

Abstract

Battery management system (BMS) is an important role in battery applications. In BMS, the accurate estimation of the state of charge (SOC) of lithium-ion batteries is most important. Open circuit voltage (OCV) is very important for the accurate estimation of SOC. In order to obtain accurate SOC, the relationship between OCV and SOC requires real-time and accuracy. Due to the difference in lithium-ion concentration and battery internal resistance in the lithium-ion battery, OCV has the characteristics of relaxation. It is necessary to study the relaxation behavior of battery OCV. In this paper, the OCV behavior is studied and focuses on the relationship of the time constant and polarization resistance with SOC during relaxation. The results show that, when the SOC is 30%–100%, the time constant and polarization resistance of lithium-ion batteries are the smallest, the performance is the most stable, and the SOC estimation accuracy is the highest. When the battery is overcharged or SOC is low, the performance of the battery is obviously unstable. Finally, it is proposed that the SOC range of the battery can be roughly estimated by calculating the time constant, and the current aging degree of the battery can be judged.