Capacity adjustment apparatus and capacity adjustment method for battery pack

• US 20060139004A1
• Filed: 12/22/2005
• Published: 06/29/2006
• Est. Priority Date: 12/27/2004
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Yoshida, Shinsuke, Uesugi, Yukio
• Granted Patent: US 7,609,030 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits

Abstract

A capacity adjustment circuit provided in conjunction with each cell discharges the corresponding cell if the cell voltage is higher than a bypass operating voltage and, as a result, the extent of inconsistency among the voltages at the individual cells is minimized. A cell switching circuit switches the connections between the individual cells and the capacity adjustment circuits over predetermined time intervals.

Claims

1. A capacity adjustment apparatus for a battery pack constituted by connecting a plurality of cells in series, comprising:

a plurality of capacity adjustment devices that discharge cells with voltages higher than a predetermined voltage; and

a switching device that switches connections between the plurality of cells and the plurality of capacity adjustment devices.

2. A capacity adjustment apparatus for a battery pack according to claim 1, wherein:

each capacity of the cells constituting the battery pack is adjusted by each of the capacity adjustment devices, a number of the capacity adjustment devices being equal with a number of the cells.

3. A capacity adjustment apparatus for a battery pack according to claim 1, wherein:

the switching device switches the connections between the plurality of cells and the plurality of capacity adjustment devices each time a predetermined length of time elapses.

4. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

an SOC calculating device that determines an SOC of either a battery pack or a cell; and

a control device that sets the capacity adjustment devices in a non-operational state if the SOC calculated by the SOC calculating device is less than a predetermined SOC and sets the capacity adjustment devices in an operational state if the SOC calculated by the SOC calculating device is equal to or greater than the predetermined SOC.

5. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

an SOC calculating device that determines an SOC of either a battery pack or a cell; and

a control device that sets the capacity adjustment devices in an operational state if the SOC calculated by the SOC calculating device is equal to or greater than a first SOC and also equal to or less than a second SOC, and sets the capacity adjustment devices in a non-operational state if the SOC calculated by the SOC calculating device is less than the first SOC or greater than the second SOC.

6. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

a temperature detection device that detects a temperature at the battery pack; and

a control device that sets the capacity adjustment devices in an operational state if the temperature detected by the temperature detection device is equal to or higher than a first temperature and also equal to or lower than a second temperature, and sets the capacity adjustment devices in a non-operational state if the temperature detected by the temperature detection device is lower than the first temperature or higher than the second temperature.

7. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

a charge decision-making device that makes a decision as to whether or not the battery pack is being charged; and

a control device that sets the capacity adjustment devices in an operational state if the charge decision-making device determines that the battery pack is being charged and sets the capacity adjustment devices in a non-operational state if the charge decision-making device determines that the battery pack is not being charged.

8. A capacity adjustment apparatus for a battery pack according to claim 7, included in a system that starts up a vehicle by using power from the battery pack, wherein:

the control device sustains the capacity adjustment devices in the non-operational state until vehicle startup is completed.

9. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

a temperature detection device that detects temperatures at the individual cells, wherein;

the switching device sequentially switches the connections between the cells and the capacity adjustment devices starting with a cell registering the highest temperature among the temperatures at the individual cells detected by the temperature detection device.

10. A capacity adjustment apparatus for a battery pack according to claim 1, further comprising:

an identifying device that identifies a cell disposed at a position where a high temperature tends to manifest readily, wherein;

the switching device sequentially switches the connection between the cells and the capacity adjustment devices, starting with the cell identified by the identifying device.

11. A capacity adjustment apparatus for a battery pack according to claim 4, wherein:

the switching device does not switch the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the non-operational state by the control device, and switches the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the operational state by the control device.

12. A capacity adjustment apparatus for a battery pack according to claim 5, wherein:

the switching device does not switch the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the non-operational state by the control device, and switches the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the operational state by the control device.

13. A capacity adjustment apparatus for a battery pack according to claim 6, wherein:

the switching device does not switch the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the non-operational state by the control device, and switches the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the operational state by the control device.

14. A capacity adjustment apparatus for a battery pack according to claim 7, wherein:

the switching device does not switch the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the non-operational state by the control device, and switches the connections between the plurality of cells and the plurality of capacity adjustment devices while the capacity adjustment devices are sustained in the operational state by the control device.

15. A capacity adjustment apparatus for a battery pack according to claim 4, wherein:

the capacity adjustment devices each comprise a discharge device that discharges a cell and a voltage comparison device that compares a voltage at the cell with the predetermined voltage and engages the discharge device in operation if the voltage at the cell is higher than the predetermined voltage;

the capacity adjustment apparatus further comprises a connection/disconnection device that connects/disconnects the voltage comparison device and the discharge device from each other; and

the control device sets the capacity adjustment device in the operational state by connecting the voltage comparison device and the discharge device to each other with the connection/disconnection device and sets the capacity adjustment device in the non-operational state by disconnecting the voltage comparison device and the discharge device from each other with the connection/disconnection device.

16. A capacity adjustment apparatus for a battery pack according to claim 4, wherein:

the capacity adjustment devices each comprise a discharge device that discharges a cell and a voltage comparison device that compares a voltage at the cell with the predetermined voltage and engages the discharge device in operation if the voltage at the cell is higher than the predetermined voltage;

the capacity adjustment apparatus further comprises a reference voltage generating device that generates the predetermined voltage and inputs the predetermined voltage to the voltage comparison device and a connection/disconnection device that connects/disconnects the reference voltage generating device and the voltage comparison device with each other; and

the control device sets the capacity adjustment device in the operational state by connecting the reference voltage generating device and the voltage comparison device to each other with the connection/disconnection device and sets the capacity adjustment device in the non-operational state by disconnecting the reference voltage generating device and the voltage comparison device from each other with the connection/disconnection device.

17. A capacity adjustment apparatus for a battery pack according to claim 15, wherein:

a plurality of voltage comparison devices are disposed in conjunction with the discharge device disposed in correspondence to each cell and the plurality of voltage comparison devices compare the cell voltage with various predetermined voltage values;

the capacity adjustment apparatus further comprises an average voltage calculating device that calculates an average voltage among the plurality of cells constituting the battery pack; and

the connection/disconnection device connects the discharge device and a voltage comparison device at which a predetermined voltage higher than the average voltage calculated by the average voltage calculating device is set, and disconnects the discharge device and other voltage comparison devices.

18. A capacity adjustment apparatus for a battery pack according to claim 16, wherein:

a plurality of voltage comparison devices are disposed in conjunction with the discharge device disposed in correspondence to each cell and the plurality of voltage comparison devices compare the cell voltage with various predetermined voltage values;

the capacity adjustment apparatus further comprises an average voltage calculating device that calculates an average voltage among the plurality of cells constituting the battery pack; and

the connection/disconnection device connects the reference voltage generating device and a voltage comparison device at which a predetermined voltage higher than the average voltage calculated by the average voltage calculating device is set, and disconnects the reference voltage generating device and other voltage comparison devices.

19. A capacity adjustment apparatus for a battery pack constituted by connecting a plurality of cells in series, comprising:

a plurality of capacity adjustment means for discharging cells with voltages higher than a predetermined voltage; and

a switch means for switching connections between the plurality of cells and the plurality of capacity adjustment means.

20. A battery pack capacity adjustment method through which a cell with a voltage higher than a predetermined voltage among a plurality of cells constituting a battery pack is discharged via a capacity adjustment devices, wherein:

connections between the plurality of cells and a plurality of capacity adjustment devices are switched.