Cell calculation apparatus and method for calculating an open-circuit voltage of a cell

A cell state calculation apparatus comprising:

• a voltage detector connected to a cathode terminal and an anode terminal of a secondary cell that detects a terminal voltage;
• a current detector connected to at least one of the cathode terminal or the anode terminal, the current detector detecting a current flowing through the secondary cell;
• a memory configured to store an initial charged capacity of the cathode of a secondary cell and an initial charged capacity of the anode of the secondary cell;
• and
• a processing circuitry coupled to the memory, the voltage detector, and the current detector, the processing circuitry being configured to:
• receive a voltage measurement, from the voltage detector, and a current measurement, from the current detector, while the secondary cell is charged or discharged;
• and
• calculate a function indicating a relationship between an open circuit voltage and a charged capacity of the secondary cell within a predetermined voltage range of the initial charged capacity of the cathode stored in the memory and the initial charged capacity of the anode stored in the database,
• wherein the memory is further configured to store the function calculated by the processing circuitry, and
• the processing circuitry is further configured to calculate a capacity of the secondary cell based on the second function stored in the memory.

A cell state calculation method comprising:

• detecting a terminal voltage of a secondary cell, with a voltage detector connected to a cathode terminal and an anode terminal of the secondary cell, while the secondary cell is charged or discharged;
• detecting a current flowing through the secondary cell, with a current detector connected to at least one of the cathode terminal or the anode terminal, while the secondary cell is charged or discharged;
• calculating an initial charged capacity of a cathode of the secondary cell and an initial charged capacity of an anode of the secondary cell based on a first function, the terminal voltage, and the current detected, the first function indicating a relationship between a voltage and a charged capacity of an active material;
• calculating a second function indicating a relationship between an open circuit voltage and a charged capacity of the secondary cell based on the first function, the initial charged capacity of the cathode, and the initial charged capacity of the anode;
• storing the calculated second function in a memory;
• and
• calculating a capacity of the secondary cell based on the second function stored in the memory.