Method for compensating state of charge of battery, battery management system using the method, and hybrid vehicle having the battery management system

A state of charge (SOC) compensation method that compensates an SOC of a battery, the SOC compensation method comprising:

• detecting a first SOC and calculating a first open circuit voltage (OCV) corresponding to the first SOC, wherein a range of possible SOCs is divided into at least two sections, each section being assigned a compensation value;
• measuring a pack current and a pack voltage of the battery, calculating a second OCV by using the pack current, the pack voltage, and an internal resistance, and calculating a second SOC corresponding to the second OCV;
• and
• comparing the first OCV and the second OCV, and, when the first OCV differs from the second OCV by an amount greater than a predetermined value, compensating the first SOC using the compensation value assigned to the section of the range of possible SOCs corresponding to the first SOC;
• and
• controlling a charging and discharging of the battery according to the compensated SOC.

A battery management system coupled to a battery comprising a plurality of battery cells as one battery pack, the battery management system comprising:

• an estimation state of charge (SOC) calculator that calculates an estimation SOC by using a pack current of the battery;
• a data base that stores data relating to open circuit voltages (OCV) corresponding to the estimation SOC;
• a reference SOC calculator that uses values of the pack current, a pack voltage and an internal resistance of the battery to calculate a reference OCV, and that uses the data base to calculate a reference SOC corresponding to the reference OCV;
• and
• an SOC compensator that uses the data base to detect the OCV corresponding to the estimation SOC, that compares a difference between the reference OCV and the detected OCV to determine whether to perform compensation, and that varies a compensation value according to a section, in which the estimation SOC is included, to perform the compensation.

A battery management system coupled to a battery comprising a plurality of battery cells as one battery pack, the battery management system comprising:

• an estimation state of charge (SOC) calculator that calculates an estimation SOC by using a pack current of the battery;
• a data base that stores data relating to open circuit voltages (OCV) over a range of SOCs, wherein the range of SOCs is divided into at least two sections;
• a reference SOC calculator that uses values of the pack current, a pack voltage and an internal resistance of the battery to calculate a reference OCV, and that uses the data base to calculate a reference SOC corresponding to the reference OCV;
• and
• an SOC compensator that uses the data base to detect the OCV corresponding to the estimation SOC, that compares a difference between the reference OCV and the detected OCV with a predetermined reference value to determine whether to perform compensation, and that compensates the estimation SOC according to a compensation value according to the section in which the estimation SOC is included if the reference OCV and the detected OCV differ by a value greater than the predetermined reference value.

A hybrid vehicle comprising a battery management system that transmits a state of charge (SOC) of a battery to an engine control unit (ECU) controlling an engine of the vehicle, the hybrid vehicle comprising:

• a sensing unit that measures a pack current, a pack voltage, and an internal resistance of the battery;
• a main control unit (MCU) that uses the pack current, the pack voltage, and the internal resistance transmitted from the sensing unit to determine the SOC, and that controls the battery to be charged and discharged;
• and
• a communication unit that transmits the SOC output from the MCU to the ECU, wherein the MCU comprises:
• an estimation SOC calculator that uses the pack current of the battery to calculate an estimation SOC;
• a reference SOC calculator that uses values of the pack current, the pack voltage and the internal resistance received from the sensor to calculate a reference open circuit voltage (OCV), and that calculates a reference SOC corresponding to the reference OCV;
• and
• an SOC compensator that detects an OCV corresponding to the estimation SOC, using a difference between the reference OCV and the detected OCV to determine whether to perform compensation, varying a compensation value according to a section in which the estimation SOC is included, to compensate the estimation SOC when the SOC compensator is required to perform the compensation, and outputting the estimation SOC when the SOC compensator is not required to perform the compensation.