A New State-Of-Charge Estimation Method For Valve Regulated Lead Acid Batteries

In this paper, a new improved coulomb counting method is proposed to estimate the State-of-Charge (SOC) of a 12V valve regulated lead acid (VRLA) battery. The conventional coulomb counting method estimates the SOC with a high error rate for high discharge current. Experimental results show the error in the conventional SOC estimation is as high as 16% for higher discharge currents. This error in the SOC estimation is due to the underestimation of the battery capacity. To compensate this error, a new charging coefficient is proposed. The inclusion of this charging coefficient could accurately estimate the SOC of the battery during the charging process.