Apparatus for calculating state of charge, method of calculating state of charge, and electric system

A method of calculating a state of charge of a power storage system provided with a first power storage device and a second power storage device, comprising:

• calculating a first state of charge of said first power storage device;
• calculating a second state of charge of said second power storage device;
• selecting a higher one of said first state of charge and said second state of charge when a sum of said first state of charge and said second state of charge is larger than or equal to a predetermined first value, and selecting a lower one of said first state of charge and said second state of charge when the sum of said first state of charge and said second state of charge is smaller than said first value;
• setting a first coefficient in accordance with a selected state of charge, and setting a second coefficient so as to be lower than said first coefficient;
• and
• adding a product of said first coefficient and said selected state of charge to a product of said second coefficient and the other state of charge, to thereby calculate the state of charge of said power storage system.

An electric system comprising:

• a first power storage device;
• a second power storage device;
• and
• a control unit that
• calculates a first state of charge of said first power storage device,
• calculates a second state of charge of said second power storage device,
• selects a higher one of said first state of charge and said second state of charge when a sum of said first state of charge and said second state of charge is larger than or equal to a predetermined first value, and selects a lower one of said first state of charge and said second state of charge when the sum of said first state of charge and said second state of charge is smaller than said first value,
• sets a first coefficient in accordance with a selected state of charge, and sets a second coefficient so as to be lower than said first coefficient, and
• adds a product of said first coefficient and said selected state of charge to a product of said second coefficient and the other state of charge, to thereby calculate a state of charge of said power storage system.