Battery management system and battery management method thereof

1. A battery management system comprising:

a state information calculation unit configured to calculate state information of each of a plurality of battery cells; and

a cell selection unit configured to select at least one battery cell of a high-risk group using the state information,

wherein the at least one battery cell of the high-risk group includes a battery cell having a terminal voltage that is out of an operating voltage during a charge or a discharge, and

the cell selection unit calculates a maximum voltage change amount of the plurality of battery cells, calculates a voltage threshold value serving as a reference for selecting the at least one battery cell of the high-risk group by using the maximum voltage change amount, and selects the at least one battery cell of the high-risk group based on the voltage threshold value.

2. The battery management system of claim 1 , wherein the state information calculation unit receives at least one of a voltage of each of the battery cells, a current of the battery pack, and a temperature of the battery pack from the battery pack, and calculates at least one of a state of charge (SoC), a state of health (SoH), and an internal resistance of each of the battery cells as the state information.

3. The battery management system of claim 2 , wherein the cell selection unit calculates a maximum charging voltage change amount by using a difference value between a current open terminal voltage and an open terminal voltage when fully charged of a battery cell having the lowest SoH among the plurality of battery cells, an internal resistance value of a battery cell having the largest internal resistance among the plurality of battery cells, and a maximum current that flows through the plurality of cells during charging, calculates a value obtained by adding the maximum charging voltage change amount to an upper limit value of the operating voltage as a charging voltage threshold value, and selects at least one battery cell having a terminal voltage smaller than the upper limit value and greater than the charging voltage threshold value as the at least one battery cell of the high-risk group.

4. The battery management system of claim 2 , further comprising a current calculation unit configured to calculate a maximum charging current limit value for preventing the terminal voltage of each of the plurality of battery cells from being charged while exceeding the upper limit value of the operating voltage during charging,

wherein the current calculation unit calculates the maximum charging current limit value by using a current open terminal voltage of a battery cell having the largest SoC among the selected at least one battery cell of the high-risk group, a difference value between a current open terminal voltage and an open terminal voltage when fully charged of a battery cell having the smallest SoH, and a polarization voltage of a battery cell having the largest terminal voltage.

5. The battery management system of claim 2 , wherein the cell selection unit selects a battery cell having the lowest SoH among the plurality of battery cell, calculates a maximum discharging voltage change amount by using a difference value between a current open terminal voltage and an open terminal voltage when fully discharged of the selected battery cell, an internal resistance value of a battery cell having the largest internal resistance among the plurality of battery cells, and a maximum current that flows through the plurality of battery cells during discharging, calculates a value obtained by adding the maximum discharging voltage change amount to a lower limit value of the operating voltage as a discharging voltage threshold value, and selects at least one battery cell having a terminal voltage greater than the lower limit value and smaller than the discharging voltage threshold value as the at least one battery cell of the high-risk group.

6. The battery management system of claim 2 , further comprising a current calculation unit configured to calculate a maximum discharging current limit value for preventing the terminal voltage of each of the plurality of battery cells from being less than a lower limit value of the operating voltage during discharging,

wherein the current calculation unit calculates the maximum discharging current limit value by using a current open terminal voltage of a battery cell having the smallest SoC among the selected at least one battery cell of the high-risk group, a difference value between a current open terminal voltage and an open terminal voltage when fully discharged of a battery cell having the smallest SoH, and a polarization voltage of a battery cell having the smallest terminal voltage.

7. A battery management method, the method comprising:

calculating state information of each of a plurality of battery cells;

calculating a maximum voltage change amount of the plurality of battery cells by using the state information;

calculating a voltage threshold value serving as a reference for selecting the least one battery cell of a high-risk group by using the maximum voltage change amount; and

selecting the at least one battery cell of the high-risk group based on the voltage threshold value,

wherein the at least one battery cell of the high-risk group includes a battery cell having a terminal voltage that is out of an operating voltage during a charge or a discharge.

8. The battery management method of claim 7 , wherein in the calculating of the state information of each of the plurality of battery cells, at least one of a voltage of each of the battery cells, a current of the battery pack, and a temperature of the battery pack is received from the battery pack, and at least one of a state of charge (SoC), a state of health (SoH), and an internal resistance of each of the battery cells is calculated as the state information.

9. The battery management method of claim 8 , wherein in the calculating of the maximum voltage change amount, a maximum charging voltage change amount is calculated by using a difference value between a current open terminal voltage and an open terminal voltage when fully charged of a battery cell having the lowest SoH among the plurality of battery cells, an internal resistance value of a battery cell having the largest internal resistance among the plurality of battery cells, and a maximum current that flows through the plurality of cells during charging.

10. The battery management method of claim 9 , wherein in the calculating of the voltage threshold value, a value obtained by adding the maximum charging voltage change amount to an upper limit value of the operating voltage is calculated as a charging voltage threshold value.

11. The battery management method of claim 10 , wherein in the selecting of the at least one battery cell of the high-risk group, at least one battery cell having a terminal voltage smaller than the upper limit value and greater than the charging voltage threshold value is selected as the at least one battery cell of the high-risk group.

12. The battery management method of claim 8 , further comprising, after the selecting of the at least one battery cell of the high-risk group, calculating a maximum charging current limit value for preventing the terminal voltage of each of the plurality of battery cells from being charged while exceeding the upper limit value of the operating voltage during charging.

13. The battery management method of claim 12 , wherein in the calculating of the maximum current limit value, the maximum charging current limit value is calculated by using a current open terminal voltage of a battery cell having the largest SoC among the selected at least one battery cell of the high-risk group, a difference value between a current open terminal voltage and an open terminal voltage when fully charged of a battery cell having the smallest SoH, and a polarization voltage of a battery cell having the largest terminal voltage.

14. The battery management method of claim 8 , wherein in the calculating of the maximum voltage change amount, a battery cell having the lowest SoH among the plurality of battery cell is selected, and a maximum discharging voltage change amount is calculated by using a difference value between a current open terminal voltage and an open terminal voltage when fully discharged of the selected battery cell, an internal resistance value of a battery cell having the largest internal resistance among the plurality of battery cells, and a maximum current that flows through the plurality of battery cells during discharging.

15. The battery management method of claim 14 , wherein in the calculating of the voltage threshold value, a value obtained by adding the maximum discharging voltage change amount to a lower limit value of the operating voltage is calculated as a discharging voltage threshold value.

16. The battery management method of claim 15 , wherein in the selecting of the at least one battery cell of the high-risk group, at least one battery cell having a terminal voltage greater than the lower limit value and smaller than the discharging voltage threshold value is selected as the at least one battery cell of the high-risk group.

17. The battery management method of claim 8 , further comprising, after the selecting of the at least one battery cell of the high-risk group, calculating a maximum discharging current limit value for preventing the terminal voltage of each of the plurality of battery cells from being less than a lower limit value of the operating voltage during discharging.

18. The battery management method of claim 17 , wherein in the calculating of the maximum current limit value, the maximum discharging current limit value is calculated by using a current open terminal voltage of a battery cell having the smallest SoC among the selected at least one battery cell of the high-risk group, a difference value between a current open terminal voltage and an open terminal voltage when fully discharged of a battery cell having the smallest SoH, and a polarization voltage of a battery cell having the smallest terminal voltage.