Accurate state of charge estimation of sodium-ion batteries based on temperature and operating condition correction factors

Accurate state of charge (SOC) estimation plays a critical role in the safe and efficient operation of sodium-ion batterie (SIB). However, temperature and operating condition have a great influence on SOC algorithms. In this paper, an improved open circuit voltage method (OCV) combined with coulomb counting method (CC) is proposed to estimate the SOC of SIB. The effects of temperature, aging and magnification on SOC estimation are studied, and the generated data is converted and compensated to the CC-OCV estimation model. The model validation results show that when the ambient temperature increases from 25 to 60 °C, the maximum error rate of the traditional OCV + CC method increased from 2.98 to 4.73% and 3.03 to 4.67%, respectively. While the maximum error rate of the improved OCV + CC method with temperature correction factor compensation remains within a relatively low range (1.69 to 1.88%; 1.36 to 1.83%). This indicates that the temperature correction factor plays a positive role. This method provides a more accurate approach for estimating the SOC of SIB.