State of charge estimation for battery by time differenced ARMAX model representation

A new method to estimate the state of charge of battery is proposed. The state of charge of battery can be acquired by estimating the open circuit voltage which means the output voltage without loads. The battery charge and discharge model is derived into an ARMAX model with bias. To remove the bias term, the model is time differenced. For the time differenced ARMAX model, the gradient algorithm is used to estimate the model parameters. Through real experiment, we show that the proposed method can give good estimates of state of charge of battery.