Abnormality diagnostic device

This application claims priority to Japanese Patent Application No. 2006-339897, filed on Dec. 18, 2006 and Japanese Patent Application No. 2007-285875 filed on Nov. 2, 2007. The entire disclosures of Japanese Patent Application No. 2006-339897 and Japanese Patent Application No. 2007-285875 are hereby incorporated herein by reference.

1. Field of the Invention

The present invention relates to an abnormality diagnostic device for a battery pack adapted to detect if there is a break in an electrical connection between a cell and a detection terminal provided between terminals of the cell.

2. Background Information

A battery pack generally has a plurality of cells and a plurality of detection terminals for detecting the voltages between the terminals of the cells. Japanese Laid-Open Patent Application Publication No. 2001-157367 discloses a device for determining if there is a break in an electrical connection between a detection terminal and a cell of such a battery pack. The conventional device controls switches to short circuit the detection terminals of the cell for a prescribed amount of time and then to cancel the short circuit. If, after a prescribed amount of time has elapsed, the voltage between the detection terminals remains substantially the same as when the detection terminals were short circuited, then the device determines that there is a break in the electrical connection between the cell and the detection terminals.

Japanese Laid-Open Patent Application Publication No. 2005-168118 discloses another device configured to alternately short-circuit connections between detection terminals of a plurality of cells, which form a battery pack, to determine if a cell is over-discharged or a break in a wire connection exists.

In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved abnormality diagnostic device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.

The devices described in the above mentioned references may determine that there is a break in an electrical connection between the cell and the detection terminals even when no break actually exists in the electrical connection between the cell and the detection terminals, but a switch portion that is used to short-circuit the detection terminals of a cell is malfunctioning.

One object of the present invention is to provide an abnormality diagnostic device that more accurately determines when a break in an electrical connection of a battery has occurred.

Accordingly, an abnormality diagnostic device is provided for diagnosing an abnormality in a battery pack having a plurality of cells connected in series, which includes a plurality of cell voltage detecting circuits, a plurality of discharging circuits, a switch drive circuit, a plurality of diagnostic voltage detecting circuits and an abnormality diagnostic control section. Each of the cell voltage detecting circuits is connected in parallel to a corresponding one of the cells of the battery pack to detect a voltage of the corresponding one of the cells. Each of the discharging circuits is connected in parallel to a corresponding one of the cells to selectively discharge an electric power of the corresponding one of the cells, each of the discharging circuits including a switch and a resistor that are connected in series. The switch drive circuit is connected to the switches of the discharging circuits to selectively turn on and off the switches. Each of the diagnostic voltage detecting circuits is electrically connected to a corresponding one of the discharging circuits to detect one of a voltage across a corresponding one of the switches and a voltage across a corresponding one of the resistors. The abnormality diagnostic control section is configured to control the switch drive circuit to perform a first diagnostic operation in which the switches corresponding to alternate ones of the cells are turned on and a second diagnostic operation in which all of the switches are turned on. The abnormality diagnostic control section is further configured to determine whether a break exists in an electrical connection between one of the cells and a corresponding one of the discharging circuits or an abnormality exists in one of the switches based on the voltages detected by the diagnostic voltage detecting circuits during the first diagnostic operation and the voltages detected by the diagnostic voltage detecting circuits during the second diagnostic operation.

These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention.

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is a schematic diagram of a battery pack provided with an abnormality diagnostic device in accordance with a first embodiment of the present invention;

FIG. 2 is a flowchart showing a diagnostic processing executed by the abnormality diagnostic device in accordance with the first embodiment of the present invention;

FIG. 3 is a schematic diagram of the battery pack provided with the abnormality diagnostic device illustrating a case in which all of switches of the abnormality diagnostic device are turned on and there is a break in a line connected to a positive terminal of a highest cell of the battery pack in accordance with the first embodiment of the present invention;

FIG. 4 is a schematic diagram of the battery pack provided with the abnormality diagnostic device illustrating a case in which all of the switches are turned on and there is a break in a line connected to a terminal of a cell other than the highest cell of the battery pack in accordance with the first embodiment of the present invention;

FIG. 5 is a schematic diagram of the battery pack provided with the abnormality diagnostic device illustrating a case in which an abnormality exists in one of the switches such that the switch remains off even though an on-signal is being sent from an abnormality diagnostic section of the abnormality diagnostic device in accordance with the first embodiment of the present invention;

FIG. 6 is a table summarizing a method of distinguishing among the different types of abnormalities based on the control state of the switches, the resistor voltages, and the cell voltages in accordance with the first embodiment of the present invention;

FIG. 7 is a schematic diagram of a battery pack provided with an abnormality diagnostic device in which switch voltage detecting circuits are provided for detecting the voltages across the switches in accordance with a second embodiment of the present invention; and

FIG. 8 is a flowchart showing a diagnostic processing executed by the abnormality diagnostic device in accordance with the second embodiment of the present invention.

Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Referring initially to FIG. 1 , an abnormality diagnostic device is illustrated in accordance with a first embodiment of the present invention. FIG. 1 is schematic diagram of a battery pack 1 provided with the batter abnormality diagnostic device of the first embodiment. As shown in FIG. 1 , the battery pack 1 includes a plurality of rechargeable cells (e.g., lithium battery cells) C 1 to Cn (where “n” is a natural number) connected in series. The abnormality diagnostic device includes a plurality of switches SW 1 to SWn and a plurality of resistors R 1 to Rn. One of the switches SW 1 to SW and a corresponding one of the resistors R 1 to Rn are connected in series to form a discharging circuit, which is connected in parallel to a corresponding one of the cells C 1 to Cn. For example, the discharging circuit, which has the switch SW 1 and the resistor R 1 that are connected together in series, is connected in parallel with the cell C 1 as shown in FIG. 1 . The switches SW 1 to SWn include, for example, transistors. The abnormality diagnostic device further includes an abnormality diagnostic section 10 (abnormality diagnostic control section) including a switch drive circuit configured to selectively control the on/off states of the switches SW 1 to SWn. The resistance values of the resistors R 1 to Rn are all equal to one another.

As shown in FIG. 1 , a line L 0 connects between the positive electrode of the highest cell C 1 and the switch SW 1 , and lines L 1 to Ln connect between the negative electrode of the corresponding ones of the cells C 1 to Cn and the corresponding ones of resistor R 1 to Rn. In other words, the lines L 0 to Ln are connection lines that serve to connect each of the cells C 1 to Cn to a corresponding one of the discharging circuits that comprise the switches SW 1 to SWn and the resistors R 1 to Rn connected together in series. As used herein, “the highest cell” or “the highest ordered cell” refers to one of the cells of the battery pack that is electrically positioned at the positive electrode end of the serially connected cells (e.g., the cell C 1 in the illustrated embodiment).

Moreover, the abnormality diagnostic device further includes a plurality of resistor voltage detecting circuits B 1 to Bn (diagnostic voltage detecting circuits) provided with respect to each of the resistors R 1 to Rn corresponding to each of the cells C 1 to Cn. Each of the resistor voltage detecting circuits B 1 to Bn is configured to detect the voltage across the corresponding one of the resistors R 1 to Rn and to send the detected voltage value to the abnormality diagnostic section 10 .

Furthermore, the abnormality diagnostic device includes a plurality of cell voltage detecting circuits D 1 to Dn provided with respect to each of the cells C 1 to Cn as shown in FIG. 1 . Each of the cell voltage detecting circuits D 1 to Dn is configured to detect the voltage of a corresponding one of the cells C 1 to Cn and to send the detect voltage value to the abnormality diagnostic section 10 .

The abnormality diagnostic section 10 preferably includes a microcomputer with an abnormality diagnostic control program as discussed below. The abnormality diagnostic section 10 can also include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The microcomputer of the abnormality diagnostic section 10 is programmed to control the on/off states of switches SW 1 to SW 2 . The memory circuit stores processing results and control programs that are run by the processor circuit. The abnormality diagnostic section 10 is operatively coupled to the switches SW 1 to SWn, the resistor voltage detecting circuits B 1 to Bn, the cell voltage detecting circuits D 1 to Dn and other components in a conventional manner. The internal RAM of the abnormality diagnostic section 10 stores statuses of operational flags and various control data. The abnormality diagnostic section 10 is capable of selectively controlling any of the components of the control system in accordance with the control program. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the abnormality diagnostic section 10 can be any combination of hardware and software that will carry out the functions of the present invention.

The abnormality diagnostic section 10 is configured to control the on/off states of the switches SW 1 to SWn and to determine if there is an abnormality in the switches SW 1 to SWn, if there is a break in the lines L 0 to Ln, and if the cells C 1 to Cn are overdischarged or overcharged based on the voltages received from the resistor voltage detecting circuits B 1 to Bn and the voltages received from the cell voltage detecting circuits D 1 to Dn. The method by which the abnormality diagnostic section 10 makes these determinations will be explained later.

The voltages of the cells C 1 to Cn stay within a prescribed range due to the characteristics of a battery. In the first embodiment, the prescribed range is approximately 1.0 V (volt) to approximately 4.35 V. In other words, the cell voltage will not fall below 1.0 V and the cell voltage will not rise above 4.35 V. When the cells C 1 to Cn are normal, the cell voltages will lie in another prescribed range (e.g., 2.0 V to 4.3 V). The abnormality diagnostic section 10 is configured to determine that one of the cells C 1 to Cn is in an overdischarged state if the cell voltage detected by the corresponding cell voltage detecting circuit D 1 to Dn is equal to or below a prescribed overdischarge threshold value V 1 (e.g., 2.0 V) and that a cell is in an overcharged state if the detected cell voltage is equal to or above a prescribed overcharge threshold value V 2 (e.g., 4.3 V).

The method of diagnosing an abnormality using the switches SW 1 to SWn executed will now be explained. In this explanation, the switch SW 1 will be used for the explanation, but the same method applies to the other switches SW 2 to SWn, as well. When the switch SW 1 is on, current flows from the cell C 1 to the resistor R 1 and the voltage across the resistor R 1 becomes the voltage value obtained by subtracting the on-resistance voltage of the switch SW 1 from the voltage of the cell C 1 . When the switch SW 1 is turned off, current does not flow to the resistor R 1 and the voltage across the resistor R 1 becomes substantially 0 V.

The abnormality diagnostic section 10 is configured to determine if an abnormality or failure exists in the switch SW 1 based on a control signal for turning the switch SW 1 on and off and the voltage across the resistor R 1 detected by the resistor voltage detecting circuit B 1 . More specifically, the abnormality diagnostic section 10 is configured to determine that the switch SW 1 is normal if the voltage across the resistor R 1 is in a prescribed range (e.g., from 1.0 V to 3.8 V) when control is executed to turn the switch SW 1 on. Also, the abnormality diagnostic section 10 is configured to determine that the switch SW 1 is normal if the voltage across the resistor R 1 is equal to or smaller than a prescribed voltage V 3 (e.g., 0.1 V) when control is executed to turn the switch SW 1 off.

Even if the cell C 1 is overcharged, e.g., charged to the maximum cell voltage of 4.35 V, the voltage across the resistor R 1 will be within the prescribed voltage range when the switch SW 1 is turned on, because the voltage value obtained by subtracting the on-resistance voltage of the switch SW 1 from the cell voltage will be below 3.8 V (i.e., within the prescribed voltage range from 1.0 V to 3.8 V). Additionally, the voltage across the voltage R 1 will be within the prescribed voltage range (i.e., above 1.0V) even if the cell C 1 is overdischarged when the switch SW 1 is turned on.

FIG. 2 is a flowchart for explaining a diagnostic processing executed by the abnormality diagnostic device in accordance with the first embodiment. The abnormality diagnostic section 10 is configured to start the control processing of step S 10 at any timing to determine if there is an abnormality in the switches SW 1 to SWn, if there is a break in the lines L 0 to Ln, and if each cell is overdischarged or overcharged.

In step S 10 (first diagnostic operation), the abnormality diagnostic section 10 is configured to issue a signal to turn on the switches SW 1 , SW 3 , etc., corresponding to alternate ones every other of the cells of the battery pack 1 (every other of the cells of the battery pack 1 ), starting from the highest cell C 1 . In other words, the abnormality diagnostic section 10 is configured to issue a signal serving to turn on the switches SW 1 , SW 3 , etc., which correspond to the odd numbered cells C 1 , C 3 , etc. On the other hand, the switches SW 2 , SW 4 , etc., corresponding to the even numbered cells C 2 , C 4 , C 6 , etc., remain off.

Then, in step S 20 (diagnostic voltage detecting step), the abnormality diagnostic section 10 is configured to determine if the respective voltages across the resistors R 1 to Rn (resistor voltages) are normal based on the voltage values received from the resistor voltage detecting circuits B 1 to Bn. In other words, the resistor voltage of each of the resistors R 1 , R 3 , R 5 , etc. corresponding to the odd numbered switches SW 1 , SW 3 , etc. (which are turned on) is determined to be normal if the voltage across that resistor is in the prescribed voltage range (e.g., 1.0 V to 3.8 V). On the other hand, the resistor voltage of each of the resistors R 2 , R 4 , R 6 , etc. corresponding to the even numbered switches SW 2 , SW 4 , etc. (which are turned off) is determined to be normal if the voltage across that resistor is equal to or below the prescribed voltage V 3 (e.g., 0.1 V). Once the voltages across the resistors R 1 to Rn are detected, the abnormality diagnostic section 10 is preferably configured to turn off the switches SW 1 , SW 3 , etc., which correspond to the odd numbered cells C 1 , C 3 , etc.

If all of the resistor voltages are determined to be normal in step S 20 , then the abnormality diagnostic section 10 proceeds to step S 30 .

In step S 30 (cell voltage detecting step), the abnormality diagnostic section 10 is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or larger than the prescribed overcharge threshold value V 2 (e.g., 4.3 V). If there is a cell voltage that is equal to or larger than the prescribed overcharge threshold value V 2 , then the abnormality diagnostic section 10 proceeds to step S 40 .

In step S 40 , the abnormality diagnostic section 10 determines that an overcharged cell exists. Under such circumstances, a user can be informed of the existence of the overcharged cell by, for example, illuminating an indicator lamp (not shown).

On the other hand, if the abnormality diagnostic section 10 determines that none the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or larger than the prescribed overcharge threshold value V 2 (No in step S 30 ), then the abnormality diagnostic section 10 proceeds to step S 50 .

In step S 50 , the abnormality diagnostic section 10 is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or smaller than the prescribed overdischarge threshold value V 1 (e.g., 2.0 V). If there is a cell voltage that is equal to or smaller than the prescribed overdischarge threshold value V 1 , then the abnormality diagnostic section 10 proceeds to step S 60 .

In step S 60 , the abnormality diagnostic section 10 determines that an overdischarged cell exists. Under such circumstances, a user can be informed of the existence of the overcharged cell by, for example, illuminating an indicator lamp (not shown).

On the other hand, if the abnormality diagnostic section 10 determines that none of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or smaller than the prescribed overdischarge threshold value V 1 (No in step S 50 ), the abnormality diagnostic section 10 proceeds to step S 70 .

In step S 70 (third diagnostic operation), the abnormality diagnostic section 10 is configured to issues a signal configured to turn on the switches SW 2 , SW 4 , etc., corresponding to the even numbered cells C 2 , C 4 , etc. On the other hand, the switches SW 1 , SW 3 , etc., corresponding to the odd numbered cells C 1 , C 3 , etc., remain off.

Then, in step S 71 , the abnormality diagnostic section 10 is configured to determine if the respective voltages across the resistors R 1 to Rn (resistor voltages) are normal based on the voltage values received from the resistor voltage detecting circuits B 1 to Bn. In other words, the resistor voltage of each of the resistors R 2 , R 4 , etc., corresponding to the even numbered switches SW 2 , SW 4 , etc. (which are turned on), is determined to be normal if the voltage across that resistor is in the prescribed voltage range (e.g., 1 V to 3.8 V). The resistor voltage of each of the resistors R 1 , R 3 , etc., corresponding to the odd numbered switches SW 1 , SW 3 , etc. (which are turned off), is determined to be normal if the voltage across that resistor is equal to or below the prescribed voltage V 3 (e.g., 0.1 V).

If the abnormality diagnostic section 10 determines any one of the respective voltages across the resistors R 1 to Rn (resistor voltages) is not normal (No in step S 71 ), the abnormality diagnostic section 10 proceeds to step S 72 .

In step S 72 , the abnormality diagnostic section 10 is configured to determine that at least one of the odd numbered switches SW 1 , SW 3 , etc., has a switching abnormality (failure) that makes the switch unable to turn off or that at least one of the even numbered switches SW 2 , SW 4 , etc., has a switching abnormality (failure) that makes the switch unable to turn on. Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

On the other hand, if the abnormality diagnostic section 10 determines the respective voltages across the resistors R 1 to Rn (resistor voltages) are normal (Yes in step S 71 ), then the abnormality diagnostic section 10 proceeds to step S 73 .

In step S 73 , the abnormality diagnostic section 10 determines that no break exists in the lines L 0 to Ln, that no abnormality exists in the switches SW 1 to SWn (i.e., all of the switches SW 1 to SWn are normal), and that none of the cells C 1 to Cn is overdischarged or overcharged.

In step S 20 , if the abnormality diagnostic section 10 determines that any one of the resistor voltages is not within the prescribed voltage range (e.g., 1 V to 3.8 V), the abnormality diagnostic section 10 proceeds to step S 80 . In such a case, one of the following types of abnormalities (1) to (4) exists: (1) there is a break in line L 0 ; (2) there is a break in one of lines L 1 to Ln; (3) one or more of the cells C 1 to Cn are in an overdischarged state or an overcharged state; and (4) one or more of the switches SW 1 to SWn are abnormal. In step S 80 and subsequent steps, the abnormality diagnostic section 10 identifies which type of abnormality exists.

FIG. 3 is a schematic diagram illustrating a case in which all of the switches SW 1 to SWn are on and there is a break in the line L 0 . In such a case, the voltage detected by the resistor voltage detecting circuit B 1 is substantially 0 V. Thus, the voltage detected by the resistor voltage detecting circuit B 1 is not within a voltage range (e.g., 1.0 V to 3.8 V) that is normal for when the switch SW 1 is on. Additionally, since the voltage detected by the cell voltage detecting circuit D 1 is substantially 0 V, the abnormality diagnostic section 10 determines that the voltage detected by the cell voltage detecting circuit D 1 is equal to or below the prescribed overdischarge threshold value V 1 .

FIG. 4 is a schematic diagram illustrating a case in which all of the switches SW 1 to SWn are on and there is a break in the line L 2 . Additionally, in this example, none of the cells C 1 to Cn is overdischarged or overcharged (i.e., the cell voltages of all of the cells C 1 to Cn are normal). When a break occurs in the line L 2 , current flows from the positive electrode of the cell C 2 to the negative electrode of the cell C 3 through the switch SW 2 , the resistor R 2 , the switch SW 3 , and the resistor R 3 . Under such conditions, since the average voltage of the cell C 2 and the cell C 3 acts on each of the resistors R 2 and R 3 , the voltages detected by the resistor voltage detecting circuits B 2 and B 3 are both within the normal voltage range for when the switches SW 2 and SW 3 are on. Additionally, since the voltages detected by both of the cell voltage detecting circuits D 2 and D 3 are equal to the average of the voltages of the cell C 2 and the cell C 3 , both detected voltages are higher than the prescribed overdischarge threshold value V 1 and lower than the prescribed overcharge threshold value V 2 . Although the explanation just presented with reference to FIG. 4 describes the detected voltages that occur when a break occurs in the line L 2 , the same situation regarding the detected voltages occurs when a break occurs in any of the lines L 1 , L 3 , L 4 , . . . , Ln other than the line L 0 connected to the positive terminal of the highest cell C 1 .

FIG. 5 is a schematic diagram illustrating a case in which an abnormality exists in the switch SW 3 such that the switch SW 3 remains off even though an on-signal is being sent from the abnormality diagnostic section 10 . All of the switches other than the switch SW 3 are on as shown in FIG. 5 . Additionally, in this example, none of the cells C 1 to Cn is overdischarged or overcharged (i.e., the cell voltages of all of the cells C 1 to Cn are normal). In such a case, the voltage detected by the resistor voltage detecting circuit B 3 is substantially 0 V, and thus, is not within the normal voltage range for when the switch SW 3 is on. Additionally, since the voltage detected by the cell voltage detecting circuit D 3 is equal to the voltage of the cell C 3 , the detected cell voltage is higher than the prescribed overdischarge threshold value V 1 and lower than the prescribed overcharge threshold value V 2 . Although the explanation just presented with reference to FIG. 5 describes the detected voltages that occur when an abnormality occurs in the switch SW 3 , the same situation regarding the detected voltages occurs when an abnormality occurs in any of the switches SW 1 , SW 2 , SW 4 , . . . , SWn.

As explained above, when one of the cells C 1 to Cn is in an overdischarged state, the voltage detected by one of the cell voltage detecting circuits D 1 to Dn corresponding to the overdischarged cell is equal to or below the prescribed overdischarge threshold value V 1 (e.g., 2.0 V). Similarly, when a cell is in an overcharged state, the voltage detected by the cell voltage detecting circuit corresponding to the overdischarged cell is equal to or above a prescribed overcharge threshold value V 2 (e.g., 4.3 V). Even if a cell is overdischarged or overcharged, the resistor voltage detected by the resistor voltage detecting circuit will be within the normal voltage range for when the switch is on (e.g., from 1.0 V to 3.8 V).

Referring back to the flowchart of FIG. 2 , in step S 80 (second diagnostic operation), the abnormality diagnostic section 10 is configured to issue a signal to turn all of the switches SW 1 to SWn on. Then, the abnormality diagnostic section 10 proceeds to step S 90 .

In step S 90 , the abnormality diagnostic section 10 is configured to determine if the respective voltages across the resistors R 1 to Rn (resistor voltages) are normal based on the voltage values received from each of the resistor voltage detecting circuits B 1 to Bn. In other words, the abnormality diagnostic section 10 is configured to determine that the resistor voltages of the resistors are normal if the voltage detected by each of the resistor voltage detecting circuits B 1 to Bn is within a prescribed voltage range (e.g., 1.0 V to 3.8 V). If any of the detected resistor voltages is not within the prescribed voltage range in step S 90 (No in step S 90 ), then the abnormality diagnostic section 10 determines that there is an abnormal resistor voltage, and thus, the abnormality diagnostic section 10 proceeds to step S 150 . On the other hand, if the abnormality diagnostic section 10 determines that the resistor voltages are normal in step S 90 (Yes in step S 90 ), then the abnormality diagnostic section 10 proceeds to step S 100 .

In step S 100 , the abnormality diagnostic section 10 is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or larger than the prescribed overcharge threshold value V 2 (e.g., 4.3 V). If the abnormality diagnostic section 10 determines that all of the detected cell voltages are smaller than the prescribed overcharge threshold value V 2 in step S 100 (No in step S 100 ), then the abnormality diagnostic section 10 proceeds to step S 110 . On the other hand, if the abnormality diagnostic section 10 determines that any one of the detected cell voltages is equal to or larger than the prescribed overcharge threshold value V 2 (Yes in step S 100 ), then the abnormality diagnostic section 10 proceeds to step S 140 .

In step S 140 , the abnormality diagnostic section 10 determines that an overcharged cell exists. Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

In step S 110 , the abnormality diagnostic section 10 is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or smaller than the prescribed overdischarge threshold value V 1 (e.g., 2.0 V). If the abnormality diagnostic section 10 determines that all of the detected cell voltages are larger than the prescribed overdischarge threshold value V 1 (No in step S 110 ), then the abnormality diagnostic section 10 proceeds to step S 120 . On the other hand, if the abnormality diagnostic section 10 determines that any one of the detected cell voltages is equal to or smaller than the prescribed overdischarge threshold value V 1 (Yes in step S 110 ), then the abnormality diagnostic section 10 proceeds to step S 130 .

In step S 130 , the abnormality diagnostic section 10 determines that an overdischarged cell exists. Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

In step S 120 , the abnormality diagnostic section 10 determines there is a break in any of the lines L 1 to Ln, i.e., the lines other than the highest line L 0 connected to the positive terminal of the highest cell C 1 , as explained previously with reference to FIG. 4 . Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

On the other hand, in step S 150 , the abnormality diagnostic section 10 is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or smaller than the prescribed overdischarge threshold value V 1 (e.g., 2.0 V). If the abnormality diagnostic section 10 determines that all of the detected cell voltages are larger than the prescribed overdischarge threshold value V 1 (No in step S 150 ), then the abnormality diagnostic section 10 proceeds to step S 160 . On the other hand, if the abnormality diagnostic section 10 determines that any of the detected cell voltages is equal to or smaller than the prescribed overdischarge threshold value V 1 (Yes in step S 150 ), then the abnormality diagnostic section 10 proceeds to step S 170 .

In step S 160 , as explained previously with reference to FIG. 5 , the abnormality diagnostic section 10 determines that an abnormality has occurred in at least one of the switches SW 1 to SWn. Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

In step S 170 , as explained previously with reference to FIG. 3 , the abnormality diagnostic section 10 determines that a break has occurred in the highest line L 0 that is connected to the positive terminal of the highest cell C 1 . Under such circumstances, a user can be informed of the abnormality by, for example, illuminating an indicator lamp (not shown).

FIG. 6 is a table summarizing the method of distinguishing among the different types of abnormalities based on the control state of the switches SW 1 to SWn, the resistor voltages, and the cell voltages. The types of abnormality include a switching abnormality of any of the switches SW 1 to SWn, a break in the line L 0 connected to the positive electrode of the highest cell C 1 , a brake in any of the lines L 1 to Ln, and an overdischarge of any of the cells C 1 to Cn and an overcharge of any of the cells C 1 to Cn.

The abnormality diagnostic device in accordance with the first embodiment has the discharging circuits, each including one of the switches SW 1 to SWn and one of the resistors R 1 to Rn connected in parallel with one of the cells C 1 to Cn of the battery pack 1 . Each pair of the switches SW 1 to SWn and the resistors R 1 to Rn is connected in series. With the abnormality diagnostic device in accordance with the first embodiment, voltage abnormalities of the cells C 1 to Cn, breaks in electrical connections between the cells C 1 to Cn and corresponding discharging circuits, and switching abnormalities of the switches SW 1 to SWn of the discharging circuits are detected and identified based on the control states of the switches SW 1 to SWn, the voltages of the cells C 1 to Cn, and the voltages across (between the terminals of) the resistors R 1 to Rn of the discharging circuits. In this way, voltage abnormalities of the cells C 1 to Cn, breaks in electrical connections, and switching abnormalities of the switches SW 1 to SWn can be detected and identified according to abnormality types.

In particular, the abnormality diagnostic device in accordance with the first embodiment is configured to determine that a break in electrical connection does not exist in any of the connection lines L 0 to Ln if each of the resistor voltages is within the prescribed normal voltage range (e.g., 1.0 V to 3.8 V) in accordance with the on/off state of the corresponding switch SW 1 to SWn when the on/off states of the switches SW 1 to SWn are being controlled so as to short circuit alternate ones of the cells C 1 to Cn. In this way, when a break in electrical connection does not exist, the fact that a break in electrical connection does not exist can be detected in a reliable manner.

The abnormality diagnostic device in accordance with the first embodiment is also configured to determine that a cell voltage abnormality (overcharged or overdischarged) exists or that a break in electrical connection exists in one of the connection lines L 1 to Ln other than the connection line L 0 connected to the positive terminal of the highest cell if any of the resistor voltages is not within the prescribed normal voltage range (e.g., 1.0 V to 3.8 V) when the on/off states of the switches SW 1 to SWn are being controlled so as to short circuit alternate ones of the cells C 1 to Cn and all of the resistor voltages are within the prescribed normal voltage range after all of the switches SW 1 to SWn have been turned on. More specifically, if any of the cell voltages is equal to or larger than a prescribed overcharge threshold value V 2 (e.g., 4.3 V) when all of the switches SW 1 to SWn are turned on such that all of the cells C 1 to Cn are short circuited, then the abnormality diagnostic device determines that an overcharged cell exists. On the other hand, if any of the cell voltages is equal to or smaller than a prescribed overdischarge threshold value V 1 (e.g., 2.0 V), then the abnormality diagnostic device determines that an overdischarged cell exists. Additionally, if the cell voltages are all smaller than the prescribed overcharge threshold value V 2 and larger than the prescribed overdischarge threshold value V 1 , the abnormality diagnostic device determines that a break exists in one of the connection lines L 1 to Ln other than the connection line L 0 that connects to the positive terminal of the highest cell C 1 . In this way, existence of an overcharged cell, existence of an overdischarged cell, and a break in a connection line L 1 to Ln other than the connection line L 0 that connects to the positive electrode of the highest cell C 1 can each be detected in a reliable fashion.

The abnormality diagnostic device in accordance with the first embodiment is configured to determine that a switching abnormality exists in the switches SW 1 to SWn or that a break in electrical connection exists in the connection line L 0 connected to the positive terminal of the highest cell C 1 if any of the resistor voltages is not within the prescribed voltage range (e.g., from 1.0 V to 3.8 V) when the on/off states of all of the switches SW 1 to SWn are being controlled to the on-state such that all of the cells C 1 to Cn are short circuited. More specifically, if a cell voltage is equal to or below the prescribed overdischarge threshold value V 1 (e.g., 2.0 V) when all of the switches SW 1 to SWn are turned on such that all of the cells are short circuited, then the abnormality diagnostic device determines that a break exists in the connection line L 0 connected to the positive electrode of the highest cell C 1 . In this way, a brake in the connection line L 0 connected to the positive electrode of the highest cell C 1 can be detected in a reliable manner. On the other hand, if all of the cell voltages are higher than the prescribed overdischarge threshold value when all of the switches SW 1 to SWn are turned on such that all of the cells C 1 to Cn are short circuited, then the abnormality diagnostic device determines that a switching abnormality exists in the switches SW 1 to SWn. In this way, a switching abnormality in the switches SW 1 to SWn can be detected in a reliable manner.

Since the first embodiment of the present invention enables an abnormality to be detected and identified as a break in one of the lines L 0 to Ln, an abnormality in one of the switches SW 1 to SWn, and an overdischarged or overcharged cell, it is possible not only to inform a user by, for example, illuminating an indicator, but also to change the operation of the battery to accommodate the particular abnormality that has occurred.

For example, if a break has occurred in one of the lines L 0 to Ln, then the voltage across the cell corresponding to the disconnected line cannot be detected and it is necessary to prohibit or limit consumption of electric power from the battery pack 1 or charging of the battery pack 1 . On the other hand, if an abnormality has occurred in any of the switches SW 1 to SWn, the voltages across the cells C 1 to Cn can be detected and it is possible to continue consuming electric power from the battery pack 1 or charging the battery pack 1 so long as the voltages of the cells C 1 to Cn are normal. In such a case, it is feasible instead to, for example, limit the amount of electric power and urge the user to have the battery pack 1 repaired. In other words, depending on the type of abnormality, it may not be necessary to prohibit consumption of electric power from the battery pack 1 or charging of the battery pack 1 . Since consumption of electric power from the battery pack 1 or charging of the battery pack 1 can be continued in such a case (e.g., when the switching abnormality exists in one of the switches SW 1 to SWn), the first embodiment of the present invention provides a favorable effect from a user's perspective.

Second Embodiment

Referring now to FIGS. 7 and 8 , an abnormality diagnostic device in accordance with a second embodiment will now be explained. In view of the similarity between the first and second embodiments, the parts of the second embodiment that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the second embodiment that are identical to the parts of the first embodiment may be omitted for the sake of brevity. The parts of the second embodiment that differ from the parts of the first embodiment will be indicated with a single prime (′).

The abnormality diagnostic device of the second embodiment differs from the abnormality diagnostic device of the first embodiment in that the abnormality diagnostic device of the second embodiment includes a plurality of switch voltage detecting circuits E 1 to En (diagnostic voltage detecting circuits) configured to detect the voltages across the switches SW 1 to SWn instead of the voltages across the resistors R 1 to Rn, while, in the abnormality diagnostic device of the first embodiment, the voltages across the resistors R 1 to Rn were detected by the resistor voltage detecting circuits B 1 to Bn.

FIG. 7 is a schematic diagram of the battery pack 1 provided with the abnormality diagnostic device according to the second embodiment.

FIG. 8 is a flowchart showing a diagnostic processing executed by the abnormality diagnostic device of the second embodiment shown in FIG. 7 . An abnormality diagnostic section 10 ′ of the second embodiment is configured to start the diagnostic processing shown in FIG. 8 at any timing to determine if there is an abnormality in the switches SW 1 to SWn, if there is a break in the lines L 0 to Ln, and if each cell is overdischarged or overcharged.

In step S 210 , the abnormality diagnostic section 10 ′ is configured to send a signal to turn on the switches SW 2 , SW 4 , etc. corresponding to alternate ones of the cells C 1 to Cn (every other of the cells C 1 to Cn) of the battery pack 1 , starting from the next cell after the highest cell C 1 . In other words, in the second embodiment, the abnormality diagnostic section 10 ′ is configured to send signals to turn on the switches SW 2 , SW 4 , etc., corresponding to the even numbered cells C 2 , C 4 , etc, (first diagnostic operation). On the other hand, the switches SW 1 , SW 3 , etc., corresponding to the odd numbered cells C 1 , C 3 , etc., remain off.

Then, in step S 220 , the abnormality diagnostic section 10 ′ is configured to determine if the respective voltages across the switches SW 1 to SWn (switch voltages) are normal based on the voltage values detected by the switch voltage detecting circuits E 1 to En. More specifically, the abnormality diagnostic section 10 ′ is configured to determine that the switch voltages are normal if the voltages of all of the even numbered switches SW 2 , SW 4 , etc., (which are turned on) are equal to or below a prescribed voltage (e.g., 1.0 V) and the voltages of all of the odd numbered switches SW 1 , SW 3 , etc., (which are turned off) are higher than the prescribed voltage.

If the abnormality diagnostic section 10 ′ determines that all of the switch voltages are normal in step S 220 (Yes in step S 220 ), then the abnormality diagnostic section 10 ′ proceeds to step S 230 .

In step S 230 (second diagnostic operation), the abnormality diagnostic section 10 ′ is configured to turn on all of the switches SW 1 to SWn.

Then, in step S 240 , the abnormality diagnostic section 10 ′ is configured to receive the switch voltages of the switches SW 1 to SWn detected by the switch voltage detecting circuits E 1 to En. If all of the switch voltages are equal to or below the prescribed voltage (e.g., 1.0 V) in step S 240 (Yes in step S 240 ), then the abnormality diagnostic section 10 ′ determines that the switch voltages are normal and proceeds to step S 260 . On the other hand, if any of the switch voltages is higher than the aforementioned prescribed voltage in step S 240 (No in step S 240 ), then the abnormality diagnostic section 10 ′ determines that a switch voltage is abnormal and proceeds to step S 250 .

In step S 250 , the abnormality diagnostic section 10 ′ determines that all of the switch voltages are normal (Yes in step S 220 ) when the even numbered switches SW 2 , SW 4 , etc., are turned on and the odd numbered switches SW 1 , SW 3 , etc., are turned off but a switch voltage is discovered to be abnormal (No in step S 240 ) when all of the switches SW 1 to SWn are turned on. Therefore, the abnormality diagnostic section 10 ′ determines that at least one of the odd numbered switches SW 1 , SW 3 , etc., is in an open fault state in which it cannot turn on (i.e., it cannot close). Thus, the abnormality diagnostic section 10 ′ also informs the user of the abnormality by, for example, illuminating an indicator (not shown).

On the other hand, if the abnormality diagnostic section 10 ′ determines that all of the switch voltages are normal in step S 240 (Yes in step S 240 ), then the abnormality diagnostic section 10 ′ proceeds to step S 260 .

In step S 260 (third diagnostic operation), the abnormality diagnostic section 10 ′ is configured to turn all of the switches SW 1 to SWn off.

Then, in step S 270 , the abnormality diagnostic section 10 ′ is configured to receive the switch voltages of the switches SW 1 to SWn detected by the switch voltage detecting circuits E 1 to En. If all of the switch voltages are higher than the prescribed voltage (e.g., 1.0 V) (Yes in step S 270 ), then the abnormality diagnostic section 10 ′ determines that the switch voltages are normal and proceeds to step S 290 . On the other hand, if any of the switch voltages is equal to or below than the aforementioned prescribed voltage (No in step S 270 ), then the abnormality diagnostic section 10 ′ determines that a switch voltage is abnormal and proceeds to step S 280 .

In step S 280 , the abnormality diagnostic section 10 ′ determines that at least one of the even numbered switches SW 2 , SW 4 , etc., is in a closed fault state in which it cannot turn off (i.e., it cannot open). Thus, the abnormality diagnostic section 10 ′ is configured to inform the user of the abnormality by, for example, illuminating an indicator (not shown).

On the other hand, in step S 290 , the abnormality diagnostic section 10 ′ is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or smaller than a prescribed overdischarge threshold value V 1 (e.g., 2.0 V). If there is a cell voltage that is equal to or smaller than the prescribed overdischarge threshold value V 1 (Yes in step S 290 ), then the abnormality diagnostic section 10 ′ proceeds to step S 300 .

In step S 300 , the abnormality diagnostic section 10 ′ determines that an overdischarged cell exists and informs the user of the abnormality by, for example, illuminating an indicator (not shown).

If the abnormality diagnostic section 10 ′ determines in step S 290 that all of the cell voltages are higher than the prescribed overdischarge threshold value V 1 (No in step S 290 ), then the abnormality diagnostic section 10 ′ determines that none of the cells is in an overdischarged state and proceeds to step S 310 .

In step S 310 , the abnormality diagnostic section 10 ′ is configured to determine if any of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn is equal to or larger than a prescribed overcharge threshold value V 2 (e.g., 4.3 V). If there is a cell voltage that is equal to or larger than the prescribed overcharge threshold value V 2 (Yes in step S 310 ), then the abnormality diagnostic section 10 ′ proceeds to step S 320 .

In step S 320 , the abnormality diagnostic section 10 ′ determines that an overcharged cell exists and informs the user of the abnormality by, for example, illuminating an indicator (not shown).

If the abnormality diagnostic section 10 ′ determines in step S 310 that all of the cell voltages are lower than the prescribed overcharge threshold value V 2 (No in step S 310 ), then the abnormality diagnostic section 10 ′ determines that none of the cells is in an overcharged state and proceeds to step S 330 .

In step S 330 , the abnormality diagnostic section 10 ′ determines that the battery pack 1 is in a normal state in which there are no breaks in the lines L 0 to Ln, no switching abnormalities in the switches SW 1 to SWn, and no cells that are overdischarged or overcharged.

Referring back to step S 220 , if the abnormality diagnostic section 10 ′ determines in step S 220 that any of the switch voltages is abnormal (No in step S 220 ), then the abnormality diagnostic section 10 ′ proceeds to step S 340 .

In step S 340 , the abnormality diagnostic section 10 ′ is configured to turn all of the switches SW 1 to SWn on.

Then, in step S 350 , the abnormality diagnostic section 10 ′ is configured to determine if any of the switch voltages detected by the switch voltage detecting circuits E 1 to En is higher than the prescribed voltage (e.g., 1.0 V). If the abnormality diagnostic section 10 ′ determines that any of the switch voltages is higher than the prescribed voltage (No in step S 350 ), then the abnormality diagnostic section 10 ′ determines that there is an abnormal switch voltage and proceeds to step S 360 .

In step S 360 , the abnormality diagnostic section 10 ′ determines that at least one of the even numbered switches SW 2 , SW 4 , etc., is in an open fault state in which it cannot turn on (i.e., it cannot close). Then, the abnormality diagnostic section 10 ′ is configured to inform the user of the abnormality by, for example, illuminating an indicator (not shown).

On the other hand, if the abnormality diagnostic section 10 ′ determines in step S 350 that all of the switch voltages are normal (Yes in step S 350 ), then the abnormality diagnostic section 10 ′ proceeds to step S 370 .

In step S 370 , the abnormality diagnostic section 10 ′ is configured to determine if all of the cell voltages detected by the cell voltage detecting circuits E 1 to En are within a prescribed range (e.g., 2.0 V to 4.3 V). If any of the cell voltages is outside the prescribed range (No in step S 370 ), then the abnormality diagnostic section 10 ′ determines that there is an abnormal cell voltage and proceeds to step S 380 .

In step S 380 , the abnormality diagnostic section 10 ′ determines that all of the switch voltages are normal (Yes in step S 350 ) but there is a cell voltage that is not within the prescribed range when all of the switches SW 1 to SWn are on (No in step S 370 ). Therefore, in step S 380 , the abnormality diagnostic section 10 ′ determines that there is a break in the line L 0 connected to the positive terminal of the highest cell C 1 . Therefore, the abnormality diagnostic section 10 ′ is configured to inform the user of the abnormality by, for example, illuminating an indicator (not shown).

On the other hand, if the abnormality diagnostic section 10 ′ determines in step S 370 that all of the cell voltages are within the prescribed range and are thus normal (Yes in step S 370 ), then the abnormality diagnostic section 10 ′ proceeds to step S 390 .

In step S 390 (third diagnostic operation), the abnormality diagnostic section 10 ′ is configured to turn all of the switches SW 1 to SWn off.

Then, in step S 400 , the abnormality diagnostic section 10 ′ is configured to determine if all of the cell voltages detected by the cell voltage detecting circuits D 1 to Dn are normal, i.e., within the aforementioned prescribed range. If all of the cell voltages are normal (Yes in step S 400 ), then the abnormality diagnostic section 10 ′ proceeds to step S 410 .

In step S 410 , the abnormality diagnostic section 10 ′ determines that at least one of the odd numbered switches SW 1 , SW 3 , etc., is in a closed fault state in which it cannot turn off (i.e., it cannot open). Thus, the abnormality diagnostic section 10 ′ is configured to inform the user of the abnormality by, for example, illuminating an indicator (not shown).

On the other hand, if the abnormality diagnostic section 10 ′ determines in step S 400 that any of the cell voltages are abnormal (No in step S 400 ), then the abnormality diagnostic section 10 ′ proceeds to step S 420 .

In step S 420 , the abnormality diagnostic section 10 ′ is configured to determine that a break exists in one of the lines L 1 to Ln other than the line L 0 connected to the positive electrode of the highest cell C 1 . Thus, the abnormality diagnostic section 10 ′ is configured to inform the user of the abnormality by, for example, illuminating an indicator (not shown).

Although in the first and second embodiments it is assumed that the cells C 1 to Cn making up the battery pack 1 are lithium ion cells, it is also possible to use another type of cell. Furthermore, the threshold values to which the cell voltages and resistor voltages are compared are not limited to the values mentioned in the illustrated explanations. Rather, the threshold values can be appropriately determined according to the various conditions such as the specification of the cells used in the battery pack.

The abnormality diagnostic device in accordance with the illustrated embodiments of the present invention can be employed in system that uses a battery. For example, the abnormality diagnostic device in accordance with the illustrated embodiments of the present invention can be employed in a hybrid vehicle, an electric vehicle, a fuel cell vehicle, or a system other than a vehicle that uses a battery.

Accordingly, with the abnormality diagnostic device in accordance with the present invention, voltage abnormalities of the cells C 1 to Cn, breaks in electrical connections, and switching abnormalities of the switches SW 1 and SWn can be detected and identified.

General Interpretation of Terms

In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. The term “detect” as used herein to describe an operation or function carried out by a component, a section, a device or the like includes a component, a section, a device or the like that does not require physical detection, but rather includes determining, measuring, modeling, predicting or computing or the like to carry out the operation or function. The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.