Battery pack control apparatus and battery pack control method

Abstract

A battery pack control apparatus for a battery pack that includes a plurality of unit cells electrically connected in series prevents overdischarging based on the total voltage of the battery pack, as opposed to being based on the separate voltages of the individual unit cells. When a total voltage of the battery pack corresponds to a lowest voltage of one of the plurality of unit cells decreasing to a predetermined threshold at which overdischarging would begin to occur, power supply to a load from the battery pack is at least partially restricted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate preferred embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain features of the invention.

FIG. 1 is a block diagram of a system including a battery pack control apparatus in accordance with an embodiment of the present invention.

FIG. 2A is an explanatory diagram illustrating voltage variations of unit cells during a load driving event.

FIG. 2B is a diagram illustrating a relationship between a total voltage threshold value of a battery pack and an open-circuit voltage of the battery pack.

FIG. 3 is a flow chart illustrating control associated with a battery pack control apparatus such as depicted in FIG. 1.

FIG. 4 is a flow chart similar to FIG. 3 additionally taking into consideration the influence of the battery temperature on a battery pack control apparatus such as depicted in FIG. 1.

FIG. 5 is a flow chart similar to FIG. 3 illustrating operation of a battery pack control apparatus such as depicted in FIG. 1 in connection with an electric starting motor for an engine of a motor vehicle.

Claims

1. A battery pack control apparatus for supplying power from a battery pack to a load, the battery pack including a plurality of unit cells electrically connected in series, the battery pack control apparatus comprising: a first voltage detecting unit sensing a first voltage, the first voltage corresponding to a voltage of the battery pack;a second voltage detecting unit determining a second voltage, the second voltage corresponding to a voltage of the battery pack when a voltage of at least one unit cell of the plurality of unit cells becomes a predetermined voltage; anda power control unit restricting the power supplied from the battery pack to the load in response to the first voltage being equal to or less than the second voltage.

2. A battery pack control apparatus according to claim 1, wherein the second voltage corresponds to a voltage of the battery pack when a voltage of a lowest voltage unit cell of the plurality of unit cells becomes the predetermined voltage.

3. A battery pack control apparatus according to claim 2, wherein the second voltage corresponds to an output current of the battery pack which is determined so that the voltage of the lowest voltage unit cell of the plurality of unit cells becomes the predetermined voltage, and the second voltage detecting unit determines the second voltage based on the output current, an open-circuit voltage of the battery pack, and an internal resistance of the battery pack.

4. A battery pack control apparatus according to claim 3, wherein the second voltage detecting unit determines the output current based on a voltage of a lowest open-circuit voltage unit cell of the plurality of unit cells, an internal resistance of a highest internal resistance unit cell of the plurality of unit cells, and the predetermined voltage.

5. A battery pack control apparatus according to claim 3, wherein the second voltage detecting unit senses battery pack temperature and determines internal resistance of the battery pack relative to the battery pack temperature.

6. A battery pack control apparatus according to claim 1, wherein the second voltage detecting unit determines a third voltage, the third voltage corresponds to a voltage of the battery pack when a maximum current allowed by the load is output from the battery pack, and the power control unit restricts the power supplied from the battery pack to the load when the first voltage is equal to or less than the larger one of the second voltage or the third voltage.

7. A battery pack control apparatus according to claim 1, wherein the load comprises an electric motor starting an internal combustion engine.

8. A battery pack control apparatus according to claim 7, wherein the power control unit restricts the power supplied from the battery pack during an engine start operation when the first voltage is equal to or less than the second voltage, and the power control unit restricts the power supplied from the battery pack after the engine start operation when the first voltage is equal to or less than a threshold voltage that is greater than the second voltage.

9. A battery pack control apparatus according to clam 1, wherein the predetermined voltage comprises a unit cell voltage at which overdischarging begins to occur.

10. A battery pack control apparatus for supplying power from a battery pack to a load, the battery pack including a plurality of unit cells electrically connected in series, the battery pack control apparatus comprising: first voltage detecting means for sensing a total voltage output of the battery pack;second voltage detecting means for determining a threshold voltage of the battery pack when a voltage of at least one unit cell of the plurality of unit cells becomes a predetermined voltage; andpower control means for at least partially restricting the power supplied from the battery pack to the load in response to the total voltage being equal to or less than the threshold voltage.

11. A battery pack control apparatus according to clam 10, wherein the predetermined voltage comprises a unit cell voltage at which overdischarging begins to occur.

12. A method of controlling a supply of power from a battery pack to a load, the battery pack including a plurality of unit cells electrically connected in series, the method comprising: sensing a first voltage, the first voltage corresponding to a voltage of the battery pack;determining a second voltage, the second voltage corresponding to a voltage of the battery pack when a voltage of at least one unit cell of the plurality of unit cells became a predetermined voltage; andrestricting the power being supplied from the battery pack to the load when the first voltage is equal to or less than the second voltage.

13. A method according to claim 13, further comprising: determining a third voltage corresponds to a voltage of the battery pack when a maximum current allowed by the load is output from the battery pack; andrestricting the power being supplied from the battery pack to the load when the first voltage is equal to or less than either larger the second voltage or the third voltage.