A new estimation method of state of charge using terminal voltage and internal resistance for lead acid battery

The accurate state of charge (SOC) is required for the battery for electric vehicles. Various estimation methods for the SOC of the lead acid battery have been proposed. However, any method cannot accurately predict the residual capacity. A new estimation method of the SOC on the lead acid battery is proposed. This method is based on the terminal voltage and the internal resistance of the battery. This proposed equation can decrease the estimation error for the little SOC region. We conducted discharge experiments for the lead acid battery and compared the former method with the proposed new method.