Battery pack

Abstract

To provide a battery pack of which degradation of the internal resistance can be easily diagnosed by a single battery pack.SOLUTION: A battery pack 40 includes: a battery 50; contacts 75, 76: an AC constant current source 3 for providing the battery 50 with an AC constant current of a predetermined frequency; and an AC voltage meter 4 for detecting the voltage value between a positive electrode 51 and a negative electrode 52 when an AC constant current is applied to the battery 50; and a control unit 85 for providing an AC constant current to the battery 50 by controlling the AC constant current source 3, calculating the inner resistance of the battery 50 on the basis of the voltage detected by the AC voltage meter 4, and diagnosing the degree of degradation of the battery 50 on the basis of the inner resistance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery pack mounted on a hybrid system.

Background Art

[0002] Hybrid systems that combine an engine, a motor, and a battery have been developed for industrial machines, automobiles, etc. in response to demands for lower emissions and reduced consumption of fossil fuels. A hybrid system includes, for example, an internal combustion engine that uses fossil fuel to generate power, a motor that assists the internal combustion engine, and a battery such as a lithium-ion battery that supplies power to the motor.

[0003] In a hybrid system, a battery pack including, for example, a lithium-ion battery is used as a power source for driving the motor. In a lithium-ion battery, internal resistance increases due to long-term storage or long-term use, resulting in internal resistance degradation in which the voltage drop amount during discharge increases. When internal resistance degradation occurs, the ECU (Electronic Control Unit) may perform output limitation to suppress the voltage range.

[0004] Patent Document 1 discloses a method and a detector for detecting the degree of deterioration of a lithium secondary battery, which detect at least one of the set of the charging end voltage at the time of closed circuit and the voltage at the time of open circuit after charging, and the set of the discharging end voltage at the time of closed circuit and the voltage at the time of open circuit after discharging of the lithium secondary battery, calculate a determination value from the detected set of voltages, and estimate the degree of deterioration of the lithium secondary battery based on the result of comparing the determination value with a reference value stored in advance. However, in the deterioration detection method and the deterioration detector described in Patent Document 1, it is necessary to detect at least one of the set of the charging end voltage at the time of closed circuit and the voltage at the time of open circuit after charging, and the set of the discharging end voltage at the time of closed circuit and the voltage at the time of open circuit after discharging, and a discharging resistor or the like that enables charging or discharging is required. Therefore, it is difficult to simply diagnose the degree of deterioration of the internal resistance of the battery with a single battery pack without providing a discharging resistor such as a DC / DC converter.

[0005] Patent Document 2 discloses a method for determining the deterioration of a storage battery, which measures the internal impedance of a test storage battery during discharging and determines the deterioration of the test storage battery because the maximum value at the sharp rise of the internal impedance immediately before the discharging end voltage is larger than the maximum value of the internal impedance of a non-defective storage battery. However, in the method for determining the deterioration of the storage battery described in Patent Document 2, a load such as a discharging resistor is required as in Patent Document 1. Therefore, it is difficult to simply diagnose the degree of deterioration of the internal resistance of the battery with a single battery pack.

[0006] Patent Document 3 discloses a capacity termination warning method for a secondary battery, which includes a secondary battery, a circuit for measuring the internal impedance of the secondary battery with an AC voltage of a predetermined period, and an alarm circuit for issuing an alarm when the measured internal impedance value of the circuit is equal to or greater than a predetermined value. However, the secondary battery described in Patent Document 3 is not the battery of the battery pack mounted on the hybrid system (that is, the assembled battery of lithium-ion batteries). Since the battery pack mounted on the hybrid system includes various electrical devices such as contacts, there is room for improvement in applying the degradation diagnosis based on the measurement of the internal impedance of the secondary battery to the assembled battery of lithium-ion batteries.

[0007] From the above, for the battery pack mounted on the hybrid system, it is desired that the degree of degradation of the internal resistance of the battery can be simply diagnosed with the battery pack alone.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a battery pack that can simply diagnose the degree of degradation of the internal resistance of the battery alone.

Means for Solving the Problems

[0010] One aspect of the present invention is a battery pack mounted on a hybrid system, including a battery that supplies power to a motor generator of the hybrid system, a first wiring between the positive electrode of the battery and the motor generator, and a second wiring between the negative electrode of the battery and the motor generator. A contact is provided in at least one of the wirings to open and close at least one of the first wiring and the second wiring, an alternating current constant current source that applies an alternating current constant current of a predetermined frequency to the battery, and an alternating current voltmeter that detects a voltage value between the positive electrode and the negative electrode when the alternating current constant current is applied to the battery. A control unit that applies the alternating current constant current to the battery by controlling the alternating current constant current source, calculates the internal resistance of the battery based on the voltage value detected by the alternating current voltmeter, and diagnoses the degree of deterioration of the battery based on the internal resistance. A battery pack characterized by comprising:

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a battery pack that can easily diagnose the degree of deterioration of the internal resistance of a battery alone.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, and thus are technically preferably subject to various limitations. However, the scope of the present invention is not limited to these aspects unless otherwise specifically stated to limit the present invention in the following description. In addition, in each drawing, the same components are denoted by the same reference numerals, and detailed descriptions thereof are appropriately omitted.

[0014] FIG. 1 is a block diagram showing a hybrid system equipped with a battery pack according to a first embodiment of the present invention. The hybrid system 10 shown in FIG. 1 includes an engine 1, a motor generator 2, and a battery pack 40.

[0015] The engine 1 is, for example, a multi-cylinder diesel engine such as a supercharged high-output 3-cylinder engine or 4-cylinder engine having turbocharging. However, the engine 1 is not necessarily limited to a diesel engine. The engine 1 has an ECU (Electronic Control Unit) 150. The ECU 150 controls the operation of the engine 1 and communicates with the motor generator 2 and controls the motor generator 2, for example, via CAN (Controller Area Network).

[0016] The motor generator 2 operates by the electric power supplied from the battery pack 40 to support the engine 1 when power is required, such as at the start or acceleration of industrial machines or the like on which the hybrid system 10 is mounted. Note that the hybrid system 10 is mounted on industrial machines or the like including construction machines such as forklifts and agricultural machines such as tractors. Further, the motor generator 2 uses a regenerative brake or the like to convert the kinetic energy of industrial machines or the like on which the hybrid system 10 is mounted into electric energy for power generation. The motor generator 2 incorporates an inverter. However, the inverter does not necessarily have to be incorporated in the motor generator 2 and may be provided separately from the motor generator 2.

[0017] The battery pack 40 includes a battery 50 and a BMU (Battery Management Unit) 85. The BMU 85 in the present embodiment is an example of the "control unit" of the present invention. The battery 50 is provided as a drive power source for the motor generator 2 and supplies electric power to the motor generator 2. The battery 50 has a positive electrode terminal 51 and a negative electrode terminal 52. The positive electrode terminal 51 in the present embodiment is an example of the "positive electrode" of the present invention. The negative electrode terminal 52 in the present embodiment is an example of the "negative electrode" of the present invention. Examples of the battery 50 include a 48V high-voltage type lithium-ion battery (LiB). However, the battery 50 is not limited to a lithium-ion battery. Further, the voltage of the battery 50 is not limited to 48V and may be 48V or higher.

[0018] The motor generator 2 is connected to a positive electrode wiring 174 connected to the positive electrode terminal 51 of the battery 50. The positive electrode wiring 174 is a wiring that electrically connects the positive electrode terminal 51 of the battery 50 and the motor generator 2. The positive electrode wiring 174 is an example of the "first wiring" of the present invention. Further, the motor generator 2 is connected to a negative electrode wiring 175 connected to the negative electrode terminal 52 of the battery 50. The negative electrode wiring 175 is a wiring that electrically connects the negative electrode terminal 52 of the battery 50 and the motor generator 2. The negative electrode wiring 175 is an example of the "second wiring" of the present invention.

[0019] The battery pack 40 further includes a positive electrode side contact 75, a negative electrode side contact 76, and a current value detection unit 65. Note that the battery pack 40 does not necessarily have both the positive electrode side contact 75 and the negative electrode side contact 76, and may have only the positive electrode side contact 75 or may have only the negative electrode side contact 76. In the following description, the case where the battery pack 40 has both the positive electrode side contact 75 and the negative electrode side contact 76 will be taken as an example.

[0020] The positive electrode side contact 75 is an example of the "first contact" of the present invention, and is provided in an electric circuit between the positive electrode terminal 51 of the battery 50 and the motor generator 2, that is, in the positive electrode wiring 174. The positive electrode side contact 75 is electrically connected to the ECU 150 by a signal line 181, and opens and closes the positive electrode wiring 174 based on a control signal transmitted from the ECU 150 through the signal line 181.

[0021] Note that the positive electrode side contact 75 may be electrically connected to the BMU 85. In this case, the positive electrode side contact 75 opens and closes the positive electrode wiring 174 based on a control signal transmitted from the BMU 85.

[0022] The negative electrode side contact 76 is an example of the "second contact" of the present invention and is provided in the electrical circuit between the negative electrode terminal 52 of the battery 50 and the motor generator 2, that is, in the negative electrode wiring 175. The negative electrode side contact 76 is electrically connected to the BMU 85 through the signal line 182, and opens and closes the negative electrode wiring 175 based on the control signal transmitted from the BMU 85 through the signal line 182.

[0023] Note that the negative electrode side contact 76 may be electrically connected to the ECU 150. In this case, the negative electrode side contact 76 opens and closes the negative electrode wiring 175 based on the control signal transmitted from the ECU 150.

[0024] The BMU 85 is electrically connected to the battery 50 through the signal line 183, and detects the voltage value of the battery 50 based on the signal transmitted from the battery 50 through the signal line 183. Specifically, the BMU 85 uses an internal circuit built in the BMU 85 itself to detect the voltage value of each cell built in the battery 50, and detects the sum of the voltage values of each cell as the voltage value of the battery 50. The BMU 85 monitors the state of the battery 50, and can detect an abnormality of the battery 50 based on the signal transmitted from the battery 50 through the signal line 183. For example, the BMU 85 detects the voltage value of the battery 50 based on the signal transmitted from the battery 50 through the signal line 183, and detects overcharge abnormality and overdischarge abnormality.

[0025] The BMU 85 is electrically connected to the current value detection unit 65 through the signal line 184, and acquires the current value from the current value detection unit 65 through the signal line 184. The current value detection unit 65 is provided in the positive electrode wiring 174 and detects the current value flowing through the positive electrode wiring 174. That is, the BMU 85 acquires the current value flowing through the positive electrode wiring 174 from the current value detection unit 65 through the signal line 184. The BMU 85 detects an overcurrent abnormality based on the current value acquired from the current value detection unit 65 through the signal line 184. Alternatively, the BMU 85 detects an over-temperature abnormality based on the cell temperature acquired from a CMU (Cell Management Unit; not shown).

[0026] Further, the BMU 85 is electrically connected to the ECU 150 via the signal line 193, and controls the negative electrode side contactor 76 based on a control signal transmitted from the ECU 150 through the signal line 193. The ECU 150 and the BMU 85 communicate with each other and monitor each other's states, for example, via CAN.

[0027] Here, in a secondary battery such as a lithium-ion battery, internal resistance deterioration occurs in which the internal resistance increases due to long-term storage or long-term use, and the voltage drop amount during discharge increases. This will be described below with reference to the drawings.

[0028] FIG. 2 is a graph showing an example of the behavior of voltage fluctuations of the battery when current flows from the battery to the motor generator. FIG. 3 is a graph showing the relationship between the degree of deterioration and the amount of voltage change and output during charge and discharge.

[0029] As shown in FIG. 2, when current flows from the battery 50 to the motor generator 2 for a predetermined time, the voltage value of the battery 50 detected by the BMU 85 drops. That is, when the battery 50 discharges, a voltage drop occurs in the battery 50. And when the internal resistance of the battery 50 increases due to, for example, a metal compound adhering to the negative electrode of the battery 50 and internal resistance deterioration of the battery 50 occurs, as shown by the arrow in FIG. 2, the voltage drop amount during discharge increases.

[0030] And as shown in FIG. 3, when internal resistance deterioration of the battery 50 occurs and the amount of voltage change during charge and discharge (that is, the voltage drop amount during discharge in the description of FIG. 2) becomes equal to or greater than the threshold value, the ECU 150 may perform output limitation to suppress the voltage range.

[0031] Here, as a general method for detecting deterioration of a secondary battery such as a lithium-ion battery, for example, a method using a discharge resistor such as a DC / DC converter and a load can be cited. However, in such a deterioration detection method, since a discharge resistor is required, it is difficult to simply diagnose the degree of deterioration of the internal resistance of the battery with the battery pack alone. Further, the battery 50 of the battery pack 40 mounted on the hybrid system 10 is provided as a battery module in which a plurality of cells are connected in series to obtain a required voltage (48V in the above-described example). Therefore, as described above, the battery pack 40 has various electrical devices such as not only the battery 50 but also the positive electrode side contact 75, the negative electrode side contact 76, and the current value detection unit 65. Therefore, depending on the deterioration detection method, the resistance component of at least any one of the positive electrode side contact 75, the negative electrode side contact 76, and the current value detection unit 65 may be included, and it is difficult to simply diagnose the degree of deterioration of the internal resistance of the battery with the battery pack alone.

[0032] On the other hand, as shown in FIG. 1, the battery pack 40 according to the present embodiment further includes an AC constant current source 3 and an AC voltmeter 4. The AC constant current source 3 is connected to the positive electrode wiring 174 at a connection point 33 between the positive electrode terminal 51 of the battery 50 and the positive electrode side contact 75 via the first lead wire 31. The connection point 33 of the present embodiment is an example of the "second connection point" of the present invention. In the battery pack 40 shown in FIG. 1, the AC constant current source 3 is connected to the positive electrode wiring 174 at a connection point 33 between the positive electrode terminal 51 of the battery 50 and the current value detection unit 65 via the first lead wire 31.

[0033] Further, the AC constant current source 3 is connected to the negative electrode wiring 175 at a connection point 34 between the negative electrode terminal 52 of the battery 50 and the negative electrode side contact 76 via the second lead wire 32. The connection point 34 of the present embodiment is an example of the "fourth connection point" of the present invention.

[0034] The alternating current constant current source 3 is electrically connected to the BMU 85 by the signal line 186, and based on the signal transmitted from the BMU 85 through the signal line 186, an alternating current constant current at a frequency of, for example, 1 kilohertz (kHz) is supplied to the battery 50 through the first lead wire 31 and the second lead wire 32. Note that the frequency of the alternating current constant current supplied by the alternating current constant current source 3 to the battery 50 is not limited to 1 kHz.

[0035] The alternating current voltmeter 4 is connected to the positive electrode wiring 174 at the connection point 43 between the positive electrode terminal 51 of the battery 50 and the positive electrode side contactor 75 via the first lead wire 41. The connection point 43 of the present embodiment is an example of the "first connection point" of the present invention. In the battery pack 40 shown in FIG. 1, the alternating current voltmeter 4 is connected to the positive electrode wiring 174 at the connection point 43 between the positive electrode terminal 51 of the battery 50 and the current value detection unit 65 via the first lead wire 41.

[0036] Further, the alternating current voltmeter 4 is connected to the negative electrode wiring 175 at the connection point 44 between the negative electrode terminal 52 of the battery 50 and the negative electrode side contactor 76 via the second lead wire 42. The connection point 44 of the present embodiment is an example of the "third connection point" of the present invention.

[0037] The alternating current voltmeter 4 detects the voltage value generated between the positive electrode terminal 51 of the battery 50 and the negative electrode terminal 52 of the battery 50 when the alternating current constant current source 3 supplies an alternating current constant current to the battery 50 based on the signal transmitted from the BMU 85.

[0038] The BMU 85 is electrically connected to the alternating current voltmeter 4 by the signal line 185, and acquires the voltage value detected by the alternating current voltmeter 4 through the signal line 185. That is, the BMU 85 acquires, through the signal line 185 from the alternating current voltmeter 4, the voltage value generated between the positive electrode terminal 51 of the battery 50 and the negative electrode terminal 52 of the battery 50 when the alternating current constant current source 3 supplies an alternating current constant current to the battery 50 based on the signal transmitted from the BMU 85. Then, the BMU 85 calculates the internal resistance of the battery 50 based on the voltage value acquired from the alternating current voltmeter 4.

[0039] As shown in FIG. 1, the connection point 43 where the AC voltmeter 4 is connected to the positive electrode wiring 174 is located between the connection point 33 where the AC constant current source 3 is connected to the positive electrode wiring 174 and the positive electrode terminal 51. The connection point 44 where the AC voltmeter 4 is connected to the negative electrode wiring 175 is located between the connection point 34 where the AC constant current source 3 is connected to the negative electrode wiring 175 and the negative electrode terminal 52. Further, since the impedance (i.e., internal resistance) of the AC voltmeter 4 is extremely large, when the AC constant current source 3 applies an AC constant current to the battery 50 based on the signal transmitted from the BMU 85, almost no current flows through the first lead wire 41 and the second lead wire 42 connected to the AC voltmeter 4. As a result, the AC voltmeter 4 can detect the voltage value generated between the positive electrode terminal 51 of the battery 50 and the negative electrode terminal 52 of the battery 50 without being affected by the respective wiring resistances of the first lead wire 41 and the second lead wire 42 and the respective contact resistances of the connection point 43 and the connection point 44.

[0040] Next, a second embodiment of the present invention will be described. Note that when the components of the battery pack according to the second embodiment are the same as those of the battery pack according to the first embodiment described above with reference to FIGS. 1 to 3, the overlapping descriptions will be omitted as appropriate, and the following description will focus on the differences.

[0041] FIG. 4 is a block diagram showing a hybrid system equipped with a battery pack according to a second embodiment of the present invention. The hybrid system 10A shown in FIG. 4 includes an engine 1, a motor generator 2, and a battery pack 40A.

[0042] The battery pack 40A has a battery 50 and a BMU 85A. The BMU 85A in this embodiment is an example of the "control unit" of the present invention. The BMU 85A includes an AC constant current source 3 and an AC voltmeter 4. That is, in the battery pack 40A according to this embodiment, the AC constant current source 3 and the AC voltmeter 4 described above with respect to FIGS. 1 to 3 are included in the BMU 85A. In this regard, the battery pack 40A according to the second embodiment is different from the battery pack 40 according to the first embodiment described above with respect to FIGS. 1 to 3.

[0043] The AC constant current source 3 and the AC voltmeter 4 may be realized by hardware, or may be realized by a combination of hardware and software. Alternatively, the AC constant current source 3 and the AC voltmeter 4 may be realized by a computer executing a program stored in a storage unit (not shown) of the BMU 85A. The "computer" mentioned here is not limited to a personal computer, but also includes an arithmetic processing unit, a microcomputer, etc. included in an information processing device, and generally refers to a device or apparatus capable of realizing the functions of the present invention by a program.

[0044] Based on the signal transmitted from the BMU 85A, the AC constant current source 3 applies an AC constant current with a frequency of, for example, 1 kilohertz (kHz) to the battery 50 through the signal line 183. Note that the frequency of the AC constant current applied by the AC constant current source 3 to the battery 50 is not limited to 1 kHz.

[0045] When the AC constant current source 3 applies an AC constant current to the battery 50 based on the signal transmitted from the BMU 85, the AC voltmeter 4 detects the voltage value generated between the positive terminal 51 of the battery 50 and the negative terminal 52 of the battery 50. As described above with respect to FIG. 1, for example, the AC voltmeter 4 detects the voltage value of each cell built in the battery 50 based on the signal transmitted from the battery 50 through the signal line 183, and detects the sum of the voltage values of each cell as the voltage value of the battery 50.

[0046] The BMU85A acquires the voltage value detected by the AC voltmeter 4. Then, the BMU85A calculates the internal resistance of the battery 50 based on the voltage value acquired from the AC voltmeter 4. Other configurations are the same as the components of the battery pack 40 according to the first embodiment described above with respect to FIGS. 1 to 3.

[0047] FIG. 5 is a flowchart showing the diagnosis process of the degree of deterioration of the battery in this embodiment. Note that the flowchart shown in FIG. 5 represents the diagnosis process of the degree of deterioration of the battery 50 in the battery pack 40 according to the first embodiment and the battery pack 40A according to the second embodiment. That is, each of the battery pack 40 according to the first embodiment and the battery pack 40A according to the second embodiment can execute the diagnosis process regarding the flowchart shown in FIG. 5. In the following description, the case where the battery pack 40 according to the first embodiment executes the diagnosis process of the degree of deterioration of the battery 50 will be taken as an example.

[0048] First, in step S1, before the battery pack 40 is mounted on the hybrid system 10, the BMU85 calculates the internal resistance of the battery 50 based on the voltage value acquired from the AC voltmeter 4. Specifically, before the battery pack 40 is mounted on the hybrid system 10, the BMU85 controls the AC constant current source 3 to apply an AC constant current to the battery 50. At this time, the AC voltmeter 4 detects the voltage value generated between the positive terminal 51 of the battery 50 and the negative terminal 52 of the battery 50. Then, the BMU85 calculates the internal resistance of the battery 50 based on the voltage value acquired from the AC voltmeter 4.

[0049] Subsequently, in step S2, the BMU 85 is based on the internal resistance calculated before the battery pack 40 is mounted on the hybrid system 10. Subsequently, in step S3, the BMU 85 determines whether or not the number of charge / discharge cycles of the battery 50 has reached a predetermined number after the battery pack 40 is mounted on the hybrid system 10. The "predetermined number" mentioned here is, for example, 60,000 or more. Alternatively, the "predetermined number" mentioned here is, for example, 60,000 or more and 80,000 or less. However, the "predetermined number" regarding the number of charge / discharge cycles of the battery 50 is not limited to this.

[0050] When the number of charge / discharge cycles of the battery 50 has not reached the predetermined number (step S3: NO), in step S3, the BMU 85 continues to determine whether or not the number of charge / discharge cycles of the battery 50 has reached the predetermined number. On the other hand, when the number of charge / discharge cycles of the battery 50 has reached the predetermined number (step S3: YES), in step S4, the BMU 85 applies an alternating current to the battery 50 by controlling the alternating current constant current source 3.

[0051] Subsequently, in step S5, the alternating voltage meter 4 detects the voltage value generated between the positive terminal 51 of the battery 50 and the negative terminal 52 of the battery 50.

[0052] Subsequently, in step S6, the BMU 85 calculates the internal resistance of the battery 50 based on the voltage value obtained from the alternating voltage meter 4. Then, the BMU 85 diagnoses the degree of deterioration of the battery 50 based on the rate of increase of the internal resistance calculated after the battery pack 40 is mounted on the hybrid system 10 (that is, the internal resistance calculated when the number of charge / discharge cycles of the battery 50 reaches the predetermined number) with respect to the reference internal resistance set in step S2 (that is, the internal resistance calculated before the battery pack 40 is mounted on the hybrid system 10). For example, when the rate of increase of the internal resistance calculated after the battery pack 40 is mounted on the hybrid system 10 with respect to the reference internal resistance is equal to or higher than a predetermined threshold value, the BMU 85 determines that the internal resistance of the battery 50 has deteriorated.

[0053] As described above, according to this embodiment, the battery pack 40 includes an alternating current constant current source 3 that applies an alternating current constant current of a predetermined frequency to the battery 50, and an alternating current voltmeter 4 that detects the voltage value between the positive electrode terminal 51 and the negative electrode terminal 52 when the alternating current constant current is applied to the battery 50. Then, the BMU 85 applies an alternating current constant current to the battery 50 by controlling the alternating current constant current source 3, calculates the internal resistance of the battery 50 based on the voltage value detected by the alternating current voltmeter 4, and diagnoses the degree of deterioration of the battery 50 based on the calculated internal resistance. Specifically, the BMU 85 diagnoses the degree of deterioration of the battery 50 based on the rate at which the internal resistance calculated after the battery pack 40 is mounted on the hybrid system 10 increases with respect to the internal resistance calculated before the battery pack 40 is mounted on the hybrid system 10. Thereby, the battery pack 40 according to this embodiment does not require a discharge resistor such as a DC / DC converter and a load, and can easily diagnose the degree of internal resistance deterioration of the battery 50 with the battery pack 40 alone. Such an effect can be similarly obtained in the battery pack 40A according to the second embodiment.

[0054] Further, in the battery pack 40 according to the first embodiment, the alternating current voltmeter 4 is connected to the positive electrode wiring 174 at the connection point 43 between the positive electrode terminal 51 of the battery 50 and the positive electrode side contact 75 (the current value detection unit 65 in the battery pack 40 shown in FIG. 1) via the first lead wire 41. The alternating current voltmeter 4 is also connected to the negative electrode wiring 175 at the connection point between the negative electrode terminal 52 of the battery 50 and the negative electrode side contact 76 via the second lead wire 42. Thereby, the battery pack 40 suppresses the resistance components of the positive electrode side contact 75, the negative electrode side contact 76, and the current value detection unit 65 from entering, that is, suppresses the influence of the resistance components of the positive electrode side contact 75, the negative electrode side contact 76, and the current value detection unit 65, and can easily diagnose the degree of internal resistance deterioration of the battery 50 with the battery pack 40 alone.

[0055] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the claims. The configurations of the above embodiments can be partially omitted or arbitrarily combined in a manner different from the above.

Description of Reference Numerals

[0056] 1: Engine, 2: Motor generator, 3: Alternating current constant current source, 4: Alternating voltage meter, 10: Hybrid system, 10A: Hybrid system, 31: First lead wire, 32: Second lead wire, 33: Connection point, 34: Connection point, 40: Battery pack, 40A: Battery pack, 41: First lead wire, 42: Second lead wire, 43: Connection point, 44: Connection point, 50: Battery, 51: Positive terminal, 52: Negative terminal, 65: Current value detection unit, 75: Positive side contactor, 76: Negative side contactor, 85: BMU, 85A: BMU, 150: ECU, 174: Positive electrode wiring, 175: Negative electrode wiring, 181: Signal line, 182: Signal line, 183: Signal line, 184: Signal line, 185: Signal line, 186: Signal line, 193: Signal line

Claims

1. A battery pack mounted in a hybrid system, a battery that supplies power to a motor generator of the hybrid system, a contact provided in at least one of a first wiring between the positive electrode of the battery and the motor generator and a second wiring between the negative electrode of the battery and the motor generator, and that opens and closes at least one of the first wiring and the second wiring, an alternating current constant current source that applies an alternating current constant current of a predetermined frequency to the battery, an alternating voltage meter that detects a voltage value between the positive electrode and the negative electrode when the alternating current constant current is applied to the battery, a control unit that applies the alternating current constant current to the battery by controlling the alternating current constant current source, calculates an internal resistance of the battery based on the voltage value detected by the alternating voltage meter, and diagnoses a degree of degradation of the battery based on the internal resistance, comprising, the control unit is based on the internal resistance calculated before being mounted in the hybrid system, and after being mounted in the hybrid system, when the number of charge / discharge cycles of the battery reaches a predetermined number, the alternating current constant current is applied to the battery by controlling the alternating current constant current source to calculate the internal resistance, and the degree of degradation is diagnosed based on a rate at which the calculated internal resistance has increased with respect to the reference internal resistance. A battery pack characterized by that.

2. The battery pack according to claim 1, wherein each of the alternating current constant current source and the alternating voltage meter is connected to the first wiring and the second wiring.

3. The contact is a first contact provided in the first wiring and that opens and closes the first wiring, a second contact provided in the second wiring and that opens and closes the second wiring, including, The battery pack according to claim 2, wherein each of the alternating current constant current source and the alternating voltage meter is connected to the first wiring between the positive electrode and the first contact and the second wiring between the negative electrode and the second contact.

4. A first connection point where the alternating voltage meter is connected to the first wiring is located between a second connection point where the alternating current constant current source is connected to the first wiring and the positive electrode, The third connection point where the AC voltage meter is connected to the second wiring is located between the fourth connection point where the AC constant current source is connected to the second wiring and the negative electrode. The battery pack according to claim 3, characterized in that.

5. The battery pack according to claim 1, characterized in that the AC constant current source and the AC voltage meter are included in the control unit.

6. The battery pack according to claim 1, characterized in that the predetermined number is 60,000 or more.

7. The battery pack according to any one of claims 1 to 6, characterized in that the predetermined frequency is 1 kilohertz.

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