Battery Pack, Method Of Manufacturing Battery Pack, And Method Of Controlling Battery Pack

• US 20070210746A1
• Filed: 03/07/2007
• Published: 09/13/2007
• Est. Priority Date: 03/08/2006
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: TANJOU, Yuuji
• Granted Patent: US 7,609,034 B2
• Time in Patent Office: Days
• US Class Current: 320/112
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]

Abstract

A battery pack having a plurality of electrically connected unit cells and configured so that the cells degrade at similar rates is provided. The battery pack may comprise a first unit cell and a second unit cell, wherein a temperature of the second unit cell is lower than the first unit cell. A condition of the first cell, such as states of charge or an open circuit voltage is set so that the condition of the first unit cell is less than a corresponding condition of the second unit cell. The unit cells may be thin battery cells stacked in a thickness direction of the thin battery cells, and the first unit cell may be located on an inner side of the second unit cell as viewed in a stacked direction. A temperature detecting unit may detect a temperature of each of the first and second unit cells and a charge control unit may be configured to control charging of the plurality of unit cells according to the temperatures of the first and second unit cells. With this configuration, even when the temperatures of the unit cells are not uniform, the rates of deterioration of the unit cells are equalized as much as possible.

Claims

1. A battery pack having a plurality of electrically connected unit cells comprising:

a first unit cell; and

a second unit cell,

wherein a temperature of the second unit cell is lower than the first unit cell,

wherein a condition selected from the group consisting of states of charge and the open circuit voltage of the first unit cell is less than a corresponding condition of the second unit cell.

2. The battery pack according to claim 1, wherein

the unit cells are thin battery cells stacked in a thickness direction of the thin battery cells, and

the first unit cell is located on an inner side of the second unit cell as viewed in a stacked direction.

3. The battery pack according to claim 1, further comprising:

a temperature detecting unit which detects a temperature of each of the first and second unit cells; and

a charge control unit configured to control charging of the plurality of unit cells according to the temperatures of the first and second unit cells detected by the temperature detecting unit such that a condition selected from the group consisting of states of charge and the open circuit voltage of the first unit cell is less than a corresponding condition of the second unit cell having temperatures lower than those of the first unit cell.

4. The battery pack according to claim 2, wherein a difference between a state of charge of a unit cell having the highest state of charge among the plurality of unit cells and a state of charge of a unit cell having the lowest state of charge is 10% or less.

5. The battery pack according to claim 2, wherein a difference between an open circuit voltage of a unit cell having the highest open circuit voltage among the plurality of unit cells and an open circuit voltage of a unit cell having the lowest open voltage is 0.1 V or less.

6. A method of manufacturing a battery pack containing a stack of a plurality of unit cells that are electrically connected, comprising:

charging a first unit cell of the plurality of unit cells to a first condition selected from a group consisting of a state of charge and an open circuit voltage;

charging a second unit cell of the plurality of unit cells to a second condition selected from a group consisting of a state of charge and open circuit voltage, the second condition being higher than the first condition; and

stacking and electrically connecting in series the first and second unit cell such that the second unit cell is located on an outer sides of the first unit cell.

7. A method of controlling a battery pack containing a plurality of unit cells electrically connected, comprising:

detecting a temperature of each of a first and second unit cells; and

controlling charging of the plurality of unit cells according to the detected temperatures of the first and second unit cells such that a condition selected from a group consisting of states of charge and open circuit voltages is less for the first unit cell of the plurality of unit cells than a corresponding condition for the second unit cell of the plurality of unit cells, where the second unit cell have temperatures lower than temperatures of the first unit cell.

8. A battery pack comprising:

a plurality of unit cells electrically interconnected to form a battery;

temperature detecting means for detecting a temperature of each of a first and second unit cells; and

a state-of-charge control means for controlling charging of the plurality of unit cells according to the temperatures of the first and second unit cells detected by the temperature detecting means such that a condition selected from the group consisting of states of charge and open circuit voltages of the first unit cell among the plurality of unit cells is less than a corresponding condition of the second unit cell having temperatures lower than those of the first unit cell.