Patent ID: 8653794

Claim:
A method for estimating a voltage of a secondary battery which includes a cathode comprising a first cathode material and a second cathode material with different operating voltage ranges, an anode comprising an anode material and a separator for separating the cathode from the anode, the method comprising: providing a circuit model comprising a first cathode material circuit, a second cathode material circuit connected to the first cathode material circuit in parallel and an anode material circuit connected to the first and second cathode material circuits in series, each circuit corresponding to the first cathode material, the second cathode material and the anode material, respectively; measuring a current of the secondary battery; calculating a current flowing through each circuit based on the circuit model while the current of the secondary battery is flowing; calculating a voltage formed at the first cathode material circuit by calculating an open-circuit voltage according to SOC of the first cathode material and an impedance voltage according to an impedance component of the first cathode material based on the current flowing through the first cathode material circuit and then adding the open circuit voltage and the impedance voltage; calculating a voltage formed at the second cathode material circuit by calculating an open-circuit voltage according to SOC of the second cathode material and an impedance voltage according to an impedance component of the second cathode material based on the current flowing through the second cathode material circuit and then adding the open circuit voltage and the impedance voltage; calculating a voltage formed at the anode material circuit by calculating an open-circuit voltage according to SOC of the anode material and an impedance voltage according to an impedance component of the anode material based on the current flowing through the anode material circuit and then adding the open circuit voltage and the impedance voltage; and estimating a voltage formed between the cathode and the anode by using the voltage calculated for each circuit.