State-of-Charge Estimation with Open-Circuit-Voltage for Lead-Acid Batteries

A state-of-charge (SOC) estimation method is proposed based on the relationship between the state-of-discharge (SOD) and the dynamically changed open-circuit-voltage. The variation of the open-circuit-voltage is observed experimentally on the lead-acid batteries and, by considering the open-circuit time and the previous discharging current, an estimation equation based on the equivalent circuit of the battery is derived. With an accurate SOD estimation, a precise prediction of the SOC is achievable. The estimation accuracy is verified by coulomb counting on experiments with intermittent discharging test.