Battery monitoring system and power supply monitoring device

Abstract

This battery monitoring system (50) comprises a battery monitoring device (70) for monitoring the state of a battery pack (40). In the battery pack, a plurality of battery cells (41) are aligned in a prescribed direction, and the positive electrode terminals (42a) and negative electrode terminals (42b) of the respective battery cells are alternately disposed such that the positive electrode terminals (42a) of the respective battery cells face the negative electrode terminals (42b) of adjacent battery cells. The plurality of battery cells are connected in series by connecting the positive electrode terminals of the respective battery cells to the negative electrode terminals of the adjacent battery cells. The battery monitoring system has a voltage detection unit (72) for detecting, as a first voltage, the total voltage of a cell group which is composed of some of the plurality of battery cells and serves as a first detection target, and in which an even number of consecutive battery cells are connected in series.

Description

Battery Monitoring System and Power Supply Monitoring Device ,

[0007] , ,

[0006] , ,

[0005] Cross - Reference to Related Applications

[0001] This application is based on Japanese Application No. 2025 - 015060 filed on January 31, 2025, the contents of which are incorporated herein by reference.

[0002] This disclosure relates to a battery monitoring system and a power supply monitoring device.

[0003] Conventionally, in order to monitor the state of a battery, devices that detect the voltage and impedance of the battery are known. At this time, due to the alternating current applied during impedance detection, external noise, etc., an induced electromotive force is generated in the voltage detection line, resulting in an error. Therefore, in Patent Document 1, in order to cancel out the induced electromotive force, a predetermined region surrounded by an electrical path was provided on the substrate.

[0004] Japanese Patent Application Laid - Open No. 2021 - 22473

[0005] However, when providing the predetermined region surrounded by the electrical path on the substrate, there are restrictions on the wiring, and a certain size is required. For this reason, there was a problem that the substrate became larger.

[0006] This disclosure has been made in view of the above problems, and its object is to provide a battery monitoring system and a power supply monitoring device that can miniaturize the substrate while suppressing the influence of the induced electromotive force.

[0007] A battery monitoring system for solving the above problems is a battery monitoring system comprising a battery monitoring device for monitoring the state of a battery pack composed of multiple battery cells, wherein in the battery pack, the multiple battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminal of each battery cell faces the negative terminal of an adjacent battery cell, and the multiple battery cells are connected in series by connecting the positive terminal of each battery cell to the negative terminal of an adjacent battery cell, and the system has a voltage detection unit that identifies a cell group composed of some of the multiple battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and detects its total voltage as the first voltage.

[0008] This makes it possible to miniaturize the substrate while suppressing the effects of induced electromotive force.

[0009] A battery monitoring device for solving the above problems is a battery monitoring device for monitoring the state of a battery pack composed of multiple battery cells, wherein in the battery pack, the multiple battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminal of each battery cell faces the negative terminal of the adjacent battery cell, and the multiple battery cells are connected in series by connecting the positive terminal of each battery cell to the negative terminal of the adjacent battery cell, and the device has a voltage detection unit that identifies a cell group composed of some of the multiple battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and detects its total voltage as the first voltage.

[0010] This makes it possible to miniaturize the substrate while suppressing the effects of induced electromotive force.

[0011] The above-mentioned and other purposes, features and advantages of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. The drawings are: Figure 1, a schematic diagram of the power supply system; Figure 2, a perspective view of the battery pack and battery monitoring system; Figure 3, a plan view of the battery pack and battery monitoring system; Figure 4, a side view of the battery pack and battery monitoring system; Figure 5, a block diagram of the battery monitoring system; Figure 6, a circuit diagram showing a part of the battery monitoring system; Figure 7, a flowchart of the impedance detection process; Figure 8, a schematic diagram showing the impedance vector calculation of each battery cell; and Figure 9, inside one battery cell. Figure 10 is a schematic perspective view showing the path through which current flows, Figure 11 is a diagram showing the relationship between induced electromotive force and the distance between electrical paths, Figure 12 is a perspective view showing the current path inside a battery cell, Figure 13 is a side view showing the current path inside a battery cell, Figure 14 is an exploded view showing the region enclosed by the current path inside a battery cell, Figure 15 is a perspective view of the battery pack and battery monitoring system of the second embodiment, Figure 16 is a perspective view of the battery pack and battery monitoring system of the second embodiment. Figure 17 is a plan view of the battery monitoring system, Figure 18 is a block diagram of the battery monitoring system of the second embodiment, Figure 19 is a circuit diagram showing a part of the battery monitoring system of the second embodiment, Figure 20 is a perspective view showing the current path inside the battery cell in the second embodiment, Figure 21 is a plan view showing the current path inside the battery cell in the second embodiment, Figure 22 is an exploded view showing the region enclosed by the current path in the second embodiment, and Figure 23 is a second embodiment Figure 24 is a perspective view showing the current path inside the battery cell in the embodiment, Figure 25 is a block diagram of the battery monitoring system in the third embodiment, Figure 26 is a circuit diagram showing a part of the battery monitoring system in the third embodiment, Figure 27 is a side view of the battery pack and battery monitoring system in the third embodiment, Figure 28 is a block diagram of the battery monitoring system in the fourth embodiment, Figure 29 is a plan view of the battery pack and battery monitoring system in the fourth embodiment, and Figure 30 is...Figure 31 is a schematic diagram of the vector operation of the fourth embodiment, Figure 32 is a plan view showing the current path inside the battery cell in the fifth embodiment, Figure 33 is a circuit diagram showing the voltage detection points in (a) to (c), Figure 34 is a block diagram of the battery monitoring system of the sixth embodiment, Figure 35 is a schematic diagram of the vector operation of the sixth embodiment, Figure 36 is a block diagram of the battery monitoring system of Modification 1, Figure 37 is a circuit diagram showing a part of the battery monitoring system of Modification 1, and Figure 38 is a block diagram of the battery monitoring system of Modification 2.

[0012] Hereinafter, embodiments of the battery monitoring system described herein will be explained with reference to the drawings. Note that functionally and / or structurally corresponding parts and / or related parts may be assigned the same reference numeral, or reference numerals with a difference of hundreds or more digits, between embodiments and modifications. For corresponding parts and / or related parts, refer to the descriptions of other embodiments and modifications.

[0013] (First Embodiment) The battery monitoring system 50 of this embodiment is installed in the power supply system 10 of an electrified vehicle such as a hybrid vehicle or an electric vehicle. As shown in Figure 1, the power supply system 10 includes a motor 20 as a rotating electric machine, an inverter 30 as a power converter that supplies three-phase current to the motor 20, a rechargeable battery pack 40, a battery monitoring system 50 that monitors the state of the battery pack 40, and an ECU 60 that controls the motor 20 and the like.

[0014] Motor 20 is an on-board main motor and is capable of transmitting power to drive wheels (not shown). In this embodiment, a three-phase permanent magnet synchronous motor is used as motor 20.

[0015] The inverter 30 is composed of a full-bridge circuit having the same number of upper and lower arms as the number of phases in the phase windings, and the current supplied to each phase winding is adjusted by turning on and off switches (semiconductor switching elements) provided on each arm.

[0016] The inverter 30 is equipped with an inverter control device (not shown), which controls the power supply by turning switches on and off in the inverter 30 based on various detection information from the motor 20 and the demands for power driving and power generation. As a result, the inverter control device supplies power from the battery pack 40 to the motor 20 via the inverter 30, driving the motor 20. The inverter control device also causes the motor 20 to generate power based on the power from the drive wheels, converts the generated power via the inverter 30, and supplies it to the battery pack 40 to charge the battery pack 40.

[0017] The battery pack 40 is electrically connected to the motor 20 via the inverter 30. The battery pack 40 has a terminal voltage of, for example, 100V or more, and is composed of multiple battery cells 41a to 41h connected in series. For example, lithium-ion batteries or nickel-metal hydride batteries can be used as battery cells 41a to 41h. Each battery cell 41a to 41h is a battery having an electrolyte and multiple electrodes. In this embodiment, the battery pack 40 is assumed to be composed of eight battery cells 41a to 41h. Note that battery cells 41a to 41h may be collectively referred to as battery cell 41.

[0018] As shown in Figures 2 to 4, the battery cell 41, or more specifically its housing case 44, is formed in a flattened rectangular parallelepiped shape, and power terminals 42 (positive electrode terminal 42a and negative electrode terminal 42b) are provided on its upper surface at both ends in the longitudinal direction (Y direction). The housing case 44 is made of metal and houses the electrolyte and multiple electrodes, and the electrodes are connected to the power terminals 42.

[0019] In this embodiment, the Z direction corresponds to the vertical direction of the battery cell 41, the X direction (a predetermined direction) corresponds to the short-side direction of the battery cell 41, and the Y direction corresponds to the longitudinal direction of the battery cell 41 (a direction perpendicular to the Z and X directions).

[0020] The positive terminal 42a and the negative terminal 42b protrude equally upward from the housing case 44. As shown in Figures 2 to 4, the housing cases 44 for the battery cells 41 are arranged in alignment in the X direction. In this arrangement, the sides of the battery cells 41 are aligned so that they face each other with a predetermined distance between them. The battery cells 41 may also be stacked in a predetermined direction such that the sides of adjacent battery cells 41 are in contact with each other. In this embodiment, in Figure 2, the battery cells are arranged from right to left in the order of battery cell 41a → battery cell 41b → battery cell 41c... → battery cell 41h.

[0021] When aligning, the positive terminals 42a and negative terminals 42b of each battery cell 41 are arranged so that they are staggered relative to each other. In other words, the positive terminals 42a and negative terminals 42b of each battery cell 41 are arranged so that the positive terminal 42a of each battery cell 41 faces the negative terminal 42b of the adjacent battery cell 41 in the X direction. For example, the positive terminal 42a of battery cell 41a faces the negative terminal 42b of battery cell 41b, and the negative terminal 42b of battery cell 41a faces the positive terminal 42a of battery cell 41b.

[0022] The positive terminal 42a of each battery cell 41 is connected to the negative terminal 42b of an adjacent battery cell 41 via a busbar 43, so that each battery cell 41 is connected in series. The negative terminal 42b of each battery cell 41 is connected to the positive terminal 42a of an adjacent battery cell 41 via a busbar 43. The busbar 43 is made of a conductive material and is formed in the shape of a thin plate with a length such that it can reach the adjacent power terminals 42, for example, about two to three times the thickness of the battery cell 41 in the X direction. The positive terminal 42a and the negative terminal 42b are inserted into through holes in the busbar 43 and connected by welding or the like.

[0023] Of the multiple battery cells 41 that make up the battery pack 40, the positive terminal 42a of the battery cell 41h on one side of the X-direction corresponds to the positive side power supply terminal of the battery pack 40. This positive terminal 42a (the positive side power supply terminal of the battery pack 40) is not connected to the negative terminal 42b of the adjacent battery cell 41g, but is connected to the positive side power supply path L1, as shown in Figure 1.

[0024] Similarly, among the multiple battery cells 41 that make up the battery pack 40, the negative terminal 42b of the battery cell 41a on the other end in the X direction corresponds to the negative side power supply terminal of the battery pack 40. This negative terminal 42b (the negative side power supply terminal of the battery pack 40) is not connected to the positive terminal 42a of the adjacent battery cell 41b, but is connected to the negative side power supply path L2, as shown in Figure 1.

[0025] As shown in Figure 1, the positive terminal power supply path L1, which is connected to the positive terminal power supply terminal of the battery pack 40, is connected to the positive terminal terminal of an electrical load such as the inverter 30. Similarly, the negative terminal power supply path L2, which is connected to the negative terminal power supply terminal of the battery pack 40, is connected to the negative terminal terminal of an electrical load such as the inverter 30. Relay switches SMR (system main relay switches) are provided in both the positive terminal power supply path L1 and the negative terminal power supply path L2, and the relay switches SMR are configured to switch between supplying and disconnecting power.

[0026] The battery monitoring system 50 monitors the status of each battery cell 41. For example, the battery monitoring system 50 measures and monitors the voltage, impedance, etc., of each battery cell 41. It may also identify and monitor the state of charge (SOC) and state of health (SOH). In the first embodiment, the battery monitoring system 50 is provided for the battery pack 40. The battery monitoring system 50 is connected to the ECU 60 and outputs the status of each battery cell 41, etc. The configuration of the battery monitoring system 50 will be described later.

[0027] The ECU 60 requests power driving and power generation from the inverter control device based on various information. This information includes, for example, accelerator and brake operation information, vehicle speed, and the status of the battery pack 40.

[0028] Next, the battery monitoring system 50 will be described in detail. As shown in Figures 4 to 6, the battery monitoring system 50 comprises a BMU 70 (Battery Management Unit) and a circuit board 80. The BMU 70 corresponds to the battery monitoring device.

[0029] As shown in Figure 5, the battery monitoring system 50 comprises a plurality of impedance detection units 71a to 71h and a calculation unit 76 that calculates the impedance of each battery cell 41a to 41h. As shown in Figures 5 and 6, most of the plurality of impedance detection units 71a to 71h and the calculation unit 76 are mounted on the BMU 70, and only a part of the impedance detection unit 71a is mounted on the circuit board 80.

[0030] Of the impedance detection units 71a to 71h, the impedance detection units 71b to 71h are configured to detect the impedance of a cell group consisting of some of the battery cells 41 from a plurality of battery cells 41, where an even number of consecutive battery cells 41 are connected in series. Hereinafter, the impedance detection units 71b to 71h will be referred to as the first impedance detection units 71b to 71h.

[0031] In this embodiment, a cell group in which two consecutive battery cells 41 are connected in series is designated as the first detection target. Specifically, the first impedance detection unit 71b designates a cell group consisting of battery cell 41a and battery cell 41b as the first detection target C12, the first impedance detection unit 71c designates a cell group consisting of battery cell 41b and battery cell 41c as the first detection target C23, the first impedance detection unit 71d designates a cell group consisting of battery cell 41c and battery cell 41d as the first detection target C34, and the first impedance detection unit 71e designates battery cell 41d and The cell group consisting of battery cell 41e is designated as the first detection target C45, the first impedance detection unit 71f designates the cell group consisting of battery cell 41e and battery cell 41f as the first detection target C56, the first impedance detection unit 71g designates the cell group consisting of battery cell 41f and battery cell 41g as the first detection target C67, and the first impedance detection unit 71h designates the cell group consisting of battery cell 41g and battery cell 41h as the first detection target C78. Thus, the first detection targets C12, C23, C34, C45, C56, C67, and C78 are provided at multiple locations (seven locations in this embodiment), and each of the first detection targets C12, C23, C34, C45, C56, C67, and C78 is arranged to be shifted by one cell in the X direction.

[0032] On the other hand, among the impedance detection units 71a to 71h, the impedance detection unit 71a detects the impedance of one battery cell 41a as the second detection target C1. Hereinafter, the impedance detection unit 71a will be referred to as the second impedance detection unit 71a.

[0033] The configuration of the first impedance detection units 71b to 71h will now be described. Since the first impedance detection units 71b to 71h have the same configuration, the first impedance detection unit 71b will be described as a representative example, and the other first impedance detection units 71c to 71h will not be described.

[0034] As shown in Figure 6, the first impedance detection unit 71b comprises a voltage detection unit 72, a current control unit 73, a lock-in amplifier 74, and a detection control unit 75.

[0035] The voltage detection unit 72 is a circuit for detecting the voltage of the first target to be detected and inputting it to the lock-in amplifier 74. The voltage detection unit 72 of the first impedance detection unit 71b detects the voltage V12 of the first target to be detected C12 and inputs it to the lock-in amplifier 74.

[0036] The current control unit 73 is a circuit for supplying a predetermined alternating current to the first detection target. In this embodiment, the current control unit 73 is a circuit that outputs a predetermined alternating current (sine wave signal) using the group of cells, which are the first detection target, as a power source. For example, in the case of the first impedance detection unit 71b, the current control unit 73 outputs a predetermined alternating current using the series-connected battery cells 41a and 41b as a power source.

[0037] More specifically, the current control unit 73 includes a semiconductor switch element 73a (for example, a MOSFET) and a detection resistor 73b connected in series with the semiconductor switch element 73a. In the first impedance detection unit 71b, the drain terminal of the semiconductor switch element 73a is connected to the positive terminal 42a of the battery cell 41b constituting the first detection target C12, and the source terminal of the semiconductor switch element 73a is connected in series with one end of the detection resistor 73b. In addition, in the first impedance detection unit 71b, the other end of the detection resistor 73b is connected to the negative terminal 42b of the battery cell 41a constituting the first detection target C12. The semiconductor switch element 73a is configured to allow adjustment of the amount of current flowing between the drain terminal and the source terminal.

[0038] Furthermore, the current control unit 73 is provided with a current detection amplifier 73c connected to both ends of the detection resistor 73b. The current detection amplifier 73c detects the signal (current) flowing through the detection resistor 73b and inputs the detection signal to the lock-in amplifier 74.

[0039] Furthermore, the current control unit 73 is provided with a feedback circuit 73d. The feedback circuit 73d is configured to receive an instruction signal generated based on an instruction from the detection control unit 75 via a lock-in amplifier 74, and also to receive a detection signal from the current detection amplifier 73c. ​​It is configured to compare the instruction signal and the detection signal and output the result to the gate terminal of the semiconductor switch element 73a.

[0040] The semiconductor switch element 73a adjusts the voltage applied between the gate and source, based on the signal from the feedback circuit 73d, to adjust the amount of current between the drain and source, so that it outputs a sinusoidal signal (a predetermined alternating current) instructed by the instruction signal from the cell group. If there is an error between the waveform of the sinusoidal signal instructed by the instruction signal and the waveform of the current actually flowing through the detection resistor 73b, the semiconductor switch element 73a adjusts the amount of current based on the signal from the feedback circuit 73d so that the error is corrected. As a result, the current flowing through the detection resistor 73b is stabilized and becomes approximately equal to the sinusoidal signal instructed by the instruction signal.

[0041] The lock-in amplifier 74 performs two-phase lock-in detection and measures the amplitude and phase of the input signal relative to the reference signal. In this embodiment, the lock-in amplifier 74 generates a sinusoidal signal as a reference signal based on instructions from the detection control unit 75, and inputs the instruction signal obtained by analog conversion of the sinusoidal signal to the current control unit 73, thereby causing the sinusoidal signal to flow to the first detection target C12.

[0042] When a sinusoidal signal (a predetermined alternating current) flows through the first detection target C12, a voltage fluctuation (response signal) occurs corresponding to the impedance Z12 of the first detection target C12. The lock-in amplifier 74 acquires the voltage fluctuation (response signal) of the first detection target C12 by obtaining the voltage of the first detection target C12 via the voltage detection unit 72.

[0043] Then, the lock-in amplifier 74 uses the sine wave signal generated based on the instruction of the detection control unit 75 as a reference signal, detects a value Re_Vi proportional to the real part of the voltage fluctuation (response signal) with respect to the reference signal and a value Im_Vi proportional to the imaginary part, and outputs them to the detection control unit 75.

[0044] Also, the lock-in amplifier 74 inputs a detection signal from the current control unit 73, converts the detection signal (analog signal) into a digital signal, and outputs the feedback signal to the detection control unit 75. Since the configuration and mechanism of the lock-in amplifier 74 are well-known technologies and are also described in, for example, Patent Document 1, detailed description is omitted.

[0045] The detection control unit 75 is composed of an integrated circuit or a microcomputer, inputs a value Re_Vi proportional to the real part of the voltage fluctuation and a value Im_Vi proportional to the imaginary part, and calculates the impedance (more specifically, the real part and the imaginary part of the impedance) of the first detection target C12 based on these values. At this time, the detection control unit 75 may calculate (correct) the impedance by taking into account the amplitude of the actually flowing signal (energization current) and the phase shift between the energization current and the reference signal using the input feedback signal. Since the impedance detection method is a well-known technology and is also described in, for example, Patent Document 1, detailed description is omitted.

[0046] Next, the second impedance detection unit 71a will be described. As shown in FIG. 6, the second impedance detection unit 71a includes a voltage detection unit 72, a current control unit 73, a lock-in amplifier 74, and a detection control unit 75, similar to the first impedance detection unit 71b. However, unlike the first impedance detection unit 71b, the current control unit 73 of the second impedance detection unit 71a is provided on the circuit board 80 and is not provided inside the BMU 70. Since the functions are the same except for the different detection targets, the description thereof is omitted.

[0047] Next, a method for detecting the impedance of the first detection target and the second detection target will be described. The impedance detection units 71a to 71h each execute the impedance detection process shown in FIG. 7 at a predetermined cycle. Hereinafter, the first detection target C12 will be exemplified for description, but the same applies to other first detection targets and second detection targets.

[0048] In the impedance detection process, the detection control unit 75 instructs the lock-in amplifier 74 to generate and output a sine wave signal (predetermined alternating current) (step S101). The lock-in amplifier 74 generates a sine wave signal based on the instruction, converts it into an analog signal, and outputs it as an instruction signal to the current control unit 73. The current control unit 73 outputs a sine wave signal using the first detection target C12 as a power source based on the input instruction signal.

[0049] When a sine wave signal is output from the first detection target C12, that is, when the first detection target C12 is disturbed, a voltage fluctuation reflecting the impedance of the first detection target C12 occurs between the terminals of the first detection target C12. The voltage detection unit 72 detects the voltage of the first detection target C12, inputs the voltage fluctuation (response signal), and outputs it to the lock-in amplifier 74 (step S102).

[0050] The lock-in amplifier 74 performs lock-in detection from the input voltage fluctuation of the first detection target C12 and the sine wave signal generated based on the instruction of the detection control unit 75, detects a value Re_Vi proportional to the real part of the voltage fluctuation and a value Im_Vi proportional to the imaginary part, and inputs the detection result to the detection control unit 75 (step S103). The sine wave signal generated based on the instruction of the detection control unit 75 is equal to the energization current flowing through the first detection target C12 as described above.

[0051] The detection control unit 75 calculates the impedance Z12 of the first detection target C12 based on the value Re_Vi proportional to the real part of the voltage fluctuation and the value Im_Vi proportional to the imaginary part (step S104), and outputs it to the arithmetic unit 76 (step S105). Then, the impedance detection process ends.

[0052] Each impedance detection unit 71a to 71h performs impedance detection processing, thereby detecting the impedance Z12 of the first detection target C12, the impedance Z23 of the first detection target C23, the impedance Z34 of the first detection target C34, the impedance Z45 of the first detection target C45, the impedance Z56 of the first detection target C56, the impedance Z67 of the first detection target C67, the impedance Z78 of the first detection target C78, ​​and the impedance Z1 of the second detection target C1, respectively, and inputting them to the calculation unit 76.

[0053] Next, the calculation unit 76 will be described. The calculation unit 76 is composed of an integrated circuit or a microcontroller. The calculation unit 76 sets the frequency of the alternating current supplied to each of the first and second detection targets and instructs each of the impedance detection units 71a to 71h. At this time, the set frequency instructed to each of the impedance detection units 71a to 71h is the same. The detection control unit 75 of each of the impedance detection units 71a to 71h gives instructions based on this set frequency.

[0054] Furthermore, the calculation unit 76 identifies the impedances Z1 to Z8 of each battery cell 41a to 41h based on the impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78, and Z1 detected (calculated) by each impedance detection unit 71a to 71h.

[0055] To explain in more detail, as shown in Figure 8, the calculation unit 76 calculates the impedance Z2 of battery cell 41b by subtracting impedance Z1 from impedance Z12. Next, the calculation unit 76 calculates the impedance Z3 of battery cell 41c by subtracting impedance Z2 from impedance Z23. The same calculation is repeated thereafter to calculate impedances Z4 to Z8. Note that impedance is a vector quantity consisting of a real part and an imaginary part, so a vector calculation is performed. In Figure 8, the horizontal axis is the real part and the vertical axis is the imaginary part. The calculation unit 76 also notifies the ECU 60 or the like of the impedances Z1 to Z8 of each identified battery cell 41a to 41h.

[0056] In this embodiment, the voltage detection unit 72 and the current control unit 73 are provided inside the impedance detection units 71a to 71h, but they may be provided outside. Also, the lock-in amplifier 74 and the detection control unit 75 in this embodiment correspond to the detection unit that detects impedance.

[0057] Next, the connection configuration between the battery cells 41a to 41h and the BMU 70 will be described. Figure 3 is a plan view of the battery cells 41a to 41h as seen from above (the mounting surface for the power terminals 42).

[0058] As described above, the battery cells 41a to 41h are arranged so that their positive terminal 42a and negative terminal 42b are staggered and aligned in the X direction. The battery cells 41a to 41h are connected in series by a bus bar 43.

[0059] The BMU 70 is positioned next to the battery cell 41a, which is the second detection target C1, among the battery cells 41a and 41h arranged at both ends of the battery pack 40 in the X direction. As shown in Figures 2 and 3, the BMU 70 is housed in a box-shaped case and is positioned vertically so as to be aligned in the X direction, similar to the battery cells 41a to 41h.

[0060] A thin, plate-shaped circuit board 80 is provided between the positive terminal 42a and the negative terminal 42b of the battery cells 41a to 41h. The circuit board 80 is a PCB (printed circuit board) or an FPC (flexible printed circuit board), and conductive metal electrical paths are wired on the circuit board 80.

[0061] In the circuit board 80 of this embodiment, a current output line 81, which is connected to the current control unit 73 and serves as a first electrical path through which an alternating current (sine wave signal) flows, and a voltage detection line 82, which is connected to the voltage detection unit 72 and serves as a second electrical path for detecting voltage, are wired. In this embodiment, circuit elements are mounted on the circuit board 80. In this embodiment, the circuit board 80 is equipped with a current control unit 73, which is part of the second impedance detection unit 71a, as a circuit element. Note that other circuit elements (for example, a filter circuit) may also be mounted on the circuit board 80.

[0062] The circuit board 80 has a pair of elongated first substrate portions 83 that extend in the X direction, and a second substrate portion 84 that extends in the Y direction to connect the pair of first substrate portions 83. The pair of first substrate portions 83 and the second substrate portion 84 are integrally formed.

[0063] The pair of first substrate portions 83 are positioned along the positive terminals 42a and negative terminals 42b, which are aligned at both ends in the Y direction of the battery cells 41a to 41h. More specifically, the first substrate portions 83 are positioned inside the positive terminals 42a and negative terminals 42b in the Y direction. As shown in Figure 2, the end of the first substrate portion 83 on the BMU 70 side in the X direction is bent and inserted into the connector 70a of the BMU 70. This electrically connects the electrical path wired to the circuit board 80 to the BMU 70.

[0064] The second substrate portion 84 is provided between the battery cell 41a and the BMU 70. More specifically, as shown in Figure 3, in the X direction, the width of the second substrate portion 84 extends from the power terminal 42 of the battery cell 41a to the center of the BMU 70 in the width direction. Circuit elements constituting the current control unit 73 are arranged on this second substrate portion 84. The current control unit 73 is located on the second substrate portion 84 near the positive terminal 42a of the battery cell 41a, which is the second detection target C1, that is, on the lower side in Figure 3.

[0065] Next, we will explain the electrical path. First, we will explain the electrical path connecting the first impedance detection units 71b to 71h and the power terminal 42. The electrical path wired from the first impedance detection units 71b to 71h includes current output lines 81b to 81h through which alternating current flows, as mentioned above, and voltage detection lines 82b to 82h for detecting voltage.

[0066] In Figure 3, the current output lines 81b to 81h and the voltage detection lines 82b to 82h are shown as solid lines, while the current output line 81a and the voltage detection line 82a are shown as dashed lines. Also in Figure 3, the current output lines 81a to 81h and the voltage detection lines 82a to 82h connected to the positive terminal 42a are shown with their designation ending in "p". Also in Figure 3, the current output lines 81a to 81h and the voltage detection lines 82a to 82h connected to the negative terminal 42b are shown with their designation ending in "n".

[0067] The current output lines 81b to 81h are connected to the first impedance detection units 71b to 71h inside the BMU 70, respectively, and the voltage detection lines 82b to 82h are connected to the first impedance detection units 71b to 71h, respectively.

[0068] Here, we will describe the wiring of the current output line 81h, which is connected to the first impedance detection unit 71h, among the current output lines 81b to 81h, and the wiring of the voltage detection line 82h, which is connected to the first impedance detection unit 71h, among the voltage detection lines 82b to 82h. These are wired to the upper first circuit board portion 83a in Figure 3.

[0069] Of the current output lines 81h, the positive-side current output line 81hp is connected to the positive terminal 42a of the first detection target C78 (the positive terminal 42a of the battery cell 41h) via the busbar 43. The positive-side current output line 81hp is then wired to extend straight in the X direction toward the BMU 70 from the connection point with the busbar 43. Subsequently, the positive-side current output line 81hp bends inward in the Y direction near the negative terminal 42b of the first detection target C78 (the negative terminal 42b of the battery cell 41g) in the X direction, and is wired to extend straight toward the positive terminal 42a of the battery cell 41g along the Y direction. Subsequently, the positive-side current output line 81hp bends in the X direction near the end of the first substrate portion 83a in the Y direction, and is wired straight in the X direction toward the BMN 70.

[0070] On the other hand, of the current output lines 81h, the negative electrode side current output line 81hn is connected to the negative electrode terminal 42b of the first detection target C78 (the negative electrode terminal 42b of the battery cell 41g) via the busbar 43. The negative electrode side current output line 81hn is wired so as to extend straight from the connection point with the busbar 43 along the Y direction towards the positive electrode terminal 42a of the battery cell 41g. Subsequently, near the end of the first substrate portion 83a in the Y direction, the negative electrode side current output line 81hn is bent in the X direction and wired straight toward the BMU 70. At this time, the negative electrode side current output line 81hn is wired along the positive electrode side current output line 81hp, leaving a gap in the Y direction so as not to directly contact the positive electrode side current output line 81hp, and parallel to the positive electrode side current output line 81hp.

[0071] Furthermore, the positive-side voltage detection line 82hp of the voltage detection lines 82h is connected to the positive terminal 42a of the first detection target C78 via a busbar 43, similar to the positive-side current output line 81hp, and is wired in the same way as the positive-side current output line 81hp. Note that the positive-side voltage detection line 82hp is wired parallel to the positive-side current output line 81hp, with its position offset in the X and Y directions so as not to come into contact with the positive-side current output line 81hp.

[0072] Furthermore, the negative electrode voltage detection line 82hn of the voltage detection lines 82h is connected to the negative electrode terminal 42b of the first detection target C78 via the busbar 43, similar to the negative electrode current output line 81hn, and is wired in the same way as the negative electrode current output line 81hn. The negative electrode voltage detection line 82hn is wired along the negative electrode current output line 81hn, with gaps in the X and Y directions so as not to come into contact with the negative electrode current output line 81hn, and parallel to the negative electrode current output line 81hn.

[0073] The wiring of the current output line 81h and the voltage detection line 82h has been described, but as shown in Figure 3, the other current output lines 81b to 81g and the voltage detection lines 82b to 82g are wired in a generally similar manner. However, the current output lines 81b, 81d, 81f, 81h and the voltage detection lines 82b, 82d, 82f, 82h are wired to the upper first substrate portion 83a in Figure 3. On the other hand, the other current output lines 81c, 81e, 81g and the voltage detection lines 82c, 82e, 82g are wired to the lower first substrate portion 83b.

[0074] Furthermore, the current output lines 81b, 81d, 81f, 81h and the voltage detection lines 82b, 82d, 82f, 82h are slightly offset in the X and Y directions so that each electrical path is parallel. Similarly, the current output lines 81c, 81e, 81g and the voltage detection lines 82c, 82e, 82g are also slightly offset in the X and Y directions so that each electrical path is parallel.

[0075] Next, the wiring of the current output line 81a and voltage detection line 82b connected to the second impedance detection unit 71a will be described. Of the current output lines 81a, the positive-side current output line 81ap is connected to the positive terminal 42a of the battery cell 41a, which is the second detection target C1, via the busbar 43. This positive-side current output line 81ap is wired to extend straight in the Y direction from the connection point with the busbar 43 and is connected to the current control unit 73.

[0076] Furthermore, the negative electrode current output line 81an is connected to the negative electrode terminal 42b of the battery cell 41a, which is the second detection target C1, via the bus bar 43. The negative electrode current output line 81an is wired to extend straight in the Y direction from the connection point with the bus bar 43 and is connected to the current control unit 73.

[0077] Furthermore, the pair of electrical paths connecting the current control unit 73 and the BMU 70 (an electrical path 85 through which instruction signals are input and output, and an electrical path 86 through which detection signals are input and output) are wired to extend straight from the current control unit 73 toward the BMU 70 in the X direction.

[0078] Of the voltage detection lines 82a, the positive electrode voltage detection line 82ap is connected to the positive electrode terminal 42a of the battery cell 41a, which is the second detection target C1, via the busbar 43. The positive electrode voltage detection line 82ap is wired to extend straight in the X direction toward the BMU 70 from the connection point with the busbar 43.

[0079] On the other hand, of the voltage detection lines 82b, the negative electrode voltage detection line 82an is connected to the negative electrode terminal 42b of the battery cell 41a, which is the second detection target C1, via the busbar 43. This negative electrode voltage detection line 82an is wired to extend straight in the X direction toward the BMU 70 from the connection point with the busbar 43 to the center in the width direction of the BMU 70, then bends in the Y direction and is wired to extend straight toward the positive electrode terminal 42a of the battery cell 41a, which is the second detection target C1. After that, the negative electrode voltage detection line 82an is wired to extend straight toward the lower first substrate portion 83b, then bends in the X direction to be parallel to the positive electrode voltage detection line 82ap and is wired straight toward the BMU 70.

[0080] In other words, the current output line 81a and the voltage detection line 82a are wired such that the entire second substrate portion 84 is almost completely surrounded by the current output lines 81ap and 81an, the voltage detection lines 82ap and 82an, and the positive terminal 42a and negative terminal 42b of the battery cell 41a. The region enclosed by the current output line 81a, the voltage detection line 82a, the positive terminal 42a and negative terminal 42b of the battery cell 41a may be referred to as region S1.

[0081] Note that the 90-degree bend in Figure 3 is an example and does not mean that the wiring has no bend radius. It will have a bend radius as needed. Also, the wiring pattern at the bend does not necessarily have to be 90 degrees; it may be an arc or a rounded corner as needed. Furthermore, when electrical paths intersect, they are routed through separate layers.

[0082] Incidentally, when the current control unit 73 causes an alternating current (such as a sine wave signal) to flow from the battery cell 41 to the current output line 81, an induced electromotive force based on the alternating current is generated in the voltage detection line 82. Since the voltage fluctuation (response signal) used for impedance detection is an extremely weak signal, the generation of an induced electromotive force based on the alternating current in the voltage detection line 82 will result in measurement errors. Therefore, a battery monitoring system 50 is configured to reduce the induced electromotive force.

[0083] First, a configuration for reducing the induced electromotive force generated when detecting the impedance of a single battery cell 41a, which is the second target for detection, will be explained with reference to Figures 9 and 10. Before explaining the configuration for reducing the induced electromotive force, the principle of how the induced electromotive force is generated and the principle for suppressing it will be explained. Figure 9 is a diagram showing a model of the battery cell 41a, and Figure 10 is a diagram showing a model of the current output line 81, the voltage detection line 82, and the electrical path (current path) within the battery cell 41. Note that points P1 to P8 in Figures 9 and 10 correspond to each other. The current output line 81 is shown as a dashed line, the voltage detection line 82 as a solid line, and the electrical path within the battery cell 41 as a dashed line.

[0084] The flow of current within the housing case 44 of the battery cell 41 is complex, depending on the electrode structure and other factors. However, it is expected that the magnetic flux generated when current flows within the housing case 44 of the battery cell 41 will be canceled out by eddy currents generated on the surface of the housing case 44 (resulting in a shielding effect). Based on this premise, if we assume that current flows from point P6 to point P3 along the current output line 81a, the current can be simplified to flow within the housing case 44 as follows: point P3 → point P4 → point P5 → point P6.

[0085] When an alternating current flows from point P6 to point P3 along the current output line 81a, a magnetic flux density vector B is generated in a counterclockwise direction, as shown in Figure 9. As a result, an induced electromotive force Va (shown by the dashed line) is generated in the voltage detection line 82 (point P6 → point P7 → point P8 → point P1 → point P2 → point P3) such that the potential at point P3 is higher than that at point P6.

[0086] Furthermore, along the path from point P3 → point P4 → point P5 → point P6, that is, inside the battery cell 41, an induced electromotive force Vb (shown by the dashed line) is generated such that the potential at point P3 is higher than that at point P6. In other words, the induced electromotive force Va and the induced electromotive force Vb cancel each other out.

[0087] Here, the induced electromotive force Va correlates with the region S1 formed by point P1 → point P2 → point P3 → point P6 → point P7 → point P8 → point P1. More specifically, it correlates with the magnetic flux passing through region S1. Region S1 is also defined as the region enclosed by the current output line 81, the voltage detection line 82, and the positive terminal 42a and negative terminal 42b of the battery cell 41a.

[0088] On the other hand, the induced electromotive force Vb correlates with the region S2 formed by point P3 → point P4 → point P5 → point P6 → point P3. More specifically, it correlates with the magnetic flux passing through region S2. Region S2 can also be described as the region enclosed by the current output line 81 and the electrical path inside the battery cell 41.

[0089] Here, the configuration of the battery cell 41 (shape of the housing case 44, arrangement and shape of electrodes, position and shape of power terminals 42, etc.) is determined to some extent by standards and is therefore difficult to change. Therefore, the size of region S1 is set so that the induced electromotive force generated in the voltage detection line 82a based on the alternating current flowing on the current output line 81a falls within the allowable electromotive force range, including zero. Specifically, as shown in Figure 11, it is known that the induced electromotive force changes depending on the distance L10 in the X direction between the current output line 81an and the voltage detection line 82an (see Figure 3). In Figure 11, the horizontal axis is the distance L10 and the vertical axis is the magnitude of the induced electromotive force.

[0090] Therefore, by adjusting the distance between the current output line 81a and the voltage detection line 82a in the X direction, the induced electromotive force is made to fall within the electromotive force tolerance range, including zero. The electromotive force tolerance range can be arbitrarily set, taking into consideration the calculation accuracy required for monitoring, the magnitude of voltage fluctuations (response signals), and the noise signal. In this embodiment, the electromotive force tolerance range is set to ±200 μV, centered on zero.

[0091] Furthermore, if the region S2 enclosed by the current output line 81 and the housing case 44 can be identified, the size of region S1 may be set according to region S2 such that the difference between the first magnetic flux based on the AC current passing through region S1 and the second magnetic flux based on the AC current passing through region S2 falls within the magnetic flux tolerance range, including zero. This makes it possible to suppress induced electromotive force. The magnetic flux tolerance range may be set arbitrarily, taking into consideration the calculation accuracy required for monitoring, the magnitude of the response signal and noise signal, etc.

[0092] Incidentally, in order to detect the impedance of one battery cell 41a, a region S1 was provided on the circuit board 80 as shown in Figure 3. Specifically, a second substrate portion 84 was provided on the circuit board 80 adjacent to the battery cell 41a, which is the second detection target C1, having a width dimension of approximately L10 in the X direction and a width extending from the positive terminal 42a to the negative terminal 42b in the Y direction. The region S1 was then formed on this second substrate portion 84.

[0093] Therefore, if we were to individually detect the impedance of all the battery cells 41, we would need to provide a region S1 adjacent to each battery cell 41, and consequently, a second substrate portion 84 would need to be provided for each battery cell 41. In this case, a circuit board that almost completely covers the top surface of the battery pack 40 would be required, resulting in a large substrate area and long wiring, which presents a problem.

[0094] Therefore, in this embodiment, in order to reduce the induced electromotive force without providing a region S1 for each battery cell 41, the first impedance detection units 71b to 71h target a group of cells in which an even number (two in this embodiment) consecutive battery cells 41 are connected in series as the first detection target and detect the total voltage of these cells. The mechanism by which the induced electromotive force can be reduced by detecting the voltage of a group of cells in which two consecutive battery cells 41 are connected in series will be explained with reference to Figures 12 to 14.

[0095] Figure 12 is a perspective view of two battery cells 41g and 41h connected in series, Figure 13 is a schematic plan view showing the current path flowing inside the two battery cells 41g and 41h connected in series, and Figure 14 is an unfolded view showing the region enclosed by the current path flowing inside the two battery cells 41g and 41h connected in series.

[0096] As shown in Figures 12 and 13, in two battery cells 41g and 41h connected in series, assuming that current flows from point P12 (positive terminal 42a of battery cell 41h) to point P11 along the current output line 81hp, the current can be simplified by assuming that it flows within the housing case 44 from point P19 (negative terminal 42b of battery cell 41g) → point P18 → point P17 → point P16 (positive terminal 42a of battery cell 41g) → point P15 (negative terminal 42b of battery cell 41h) → point P14 → point P13 → point P12 (positive terminal 42a of battery cell 41h).

[0097] Here, the region S21 enclosed by the current path inside battery cell 41h (points P12 → P13 → P14 → P15) is adjacent to and opposite to the region S22 enclosed by the current path inside battery cell 41g (points P16 → P17 → P18 → P19) in the X direction, and the direction of the current is opposite. For this reason, the effects of the magnetic flux passing through region S21 and the effects of the magnetic flux passing through region S22 are considered to cancel each other out. For this reason, the induced electromotive force generated by regions S21 and S22 can be ignored.

[0098] Therefore, the region affected by the alternating current (the region through which the magnetic flux passes) is considered to be the region S23 enclosed by points P12 → P13 → P14 → P15 → P16 → P17 → P18 → P19 → P12, as shown in Figure 14. Note that Figure 14 is a planar unfolded view of region S23.

[0099] If we assume that the width dimension of the battery cell 41 in the Y direction is "La", the width dimension of the battery cell 41 in the Z direction is "Lb", and the distance in the X direction between the positive terminal 42a and the negative terminal 42b is "Lc", then the area of ​​the region S23 enclosed by the current path is (La + 2Lb) × Lc. Generally, the distance Lc between the positive terminal 42a and the negative terminal 42b is much shorter than the width dimensions La and Lb of the battery cell 41, and there is air (gap) with low magnetic permeability between the battery cells 41. From this, it can be considered that the area of ​​region S23 is much smaller than the area of ​​the region S2 enclosed by the current path in one battery cell 41 (= La × Lb). As a result of the smaller area of ​​the region through which the magnetic flux generated based on the alternating current passes, the induced electromotive force generated can be reduced compared to when detecting the impedance of each individual battery cell 41.

[0100] The effects of the battery monitoring system 50 of the first embodiment will be described below.

[0101] When an alternating current is applied to detect impedance, the voltage detection unit 72 selects a group of two consecutive battery cells 41 connected in series as the first detection target and detects their total voltage as the first voltages V12, V23, V34, V45, V56, V67, and V78. In this case, as described above, compared to detecting the voltage of a single battery cell 41, the area of ​​the region surrounded by the current path inside the battery cell 41 can be reduced, and the induced electromotive force based on the alternating current can be reduced without providing a region S1 surrounded by current output lines 81 and voltage detection lines 82 on the substrate.

[0102] Therefore, it is no longer necessary to provide a second substrate portion 84, which extends between the positive terminal 42a and the negative terminal 42b, for each battery cell 41, thus reducing the area of ​​the circuit board 80. Furthermore, it is no longer necessary to wire the current output line 81 and the voltage detection line 82 across the positive terminal 42a and the negative terminal 42b, and to maintain a predetermined distance between the current output line 81 and the voltage detection line 82, increasing the flexibility of wiring and simplifying circuit design. It also becomes possible to shorten the wiring.

[0103] Furthermore, the current control units 73 of the first impedance detection units 71b to 71h can be placed inside the BMU 70, reducing the number of circuit elements mounted on the circuit board 80. This further reduces the area of ​​the circuit board 80.

[0104] As shown in Figures 4 and 5, the first detection targets C12, C23, C34, C45, C56, C67, and C78 are arranged with a one-cell shift in the X direction, and the voltage detection units 72 of the first impedance detection units 71b to 71h detect the voltage fluctuations of each of the first detection targets C12, C23, C34, C45, C56, C67, and C78. The lock-in amplifier 74 then detects Re_Vi, a value proportional to the real part of the voltage fluctuation, and Im_Vi, a value proportional to the imaginary part, with respect to the AC current flowing through each of the first detection targets C12, C23, C34, C45, C56, C67, and C78. The detection control unit 75 of the first impedance detection units 71b to 71h calculates the impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 of each of the first detection targets C12, C23, C34, C45, C56, C67, and C78 from these values.

[0105] Meanwhile, the voltage detection unit 72 of the second impedance detection unit 71a detects the battery cell 41a that does not overlap with the first detection target C23 among the battery cells 41a and 41b that constitute the first detection target C12 as the second detection target C1, and detects its voltage as the second voltage V1. The lock-in amplifier 74 of the second impedance detection unit 71a then detects Re_Vi, a value proportional to the real part of the voltage fluctuation with respect to the AC current flowing through the second detection target C1, and Im_Vi, a value proportional to the imaginary part. The detection control unit 75 of the second impedance detection unit 71a calculates the impedance Z1 of the second detection target C1 from these values.

[0106] The calculation unit 76 then calculates the impedances Z1 to Z8 of each battery cell 41a to 41h from these values. Specifically, the calculation unit 76 calculates the impedance Z2 of battery cell 41b from the difference between the second impedance Z1 and the first impedance Z12 of the first detection target C12, which includes the second detection target C1. Subsequently, the calculation unit 76 calculates the impedance Z3 of battery cell C3 from the difference between the calculated impedance Z2 and impedance Z23. The same process is repeated thereafter to calculate the impedances Z1 to Z8 of each battery cell 41.

[0107] This allows the impedance of each battery cell 41 to be calculated from the impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78 of the cell group consisting of two battery cells 41 connected in series, and the impedance Z1 of battery cell 41a.

[0108] The battery cells 41 are aligned in the X direction such that the positive terminal 42a and negative terminal 42b of each battery cell 41 are staggered. As a result, the positive terminal 42a of each battery cell 41 faces the negative terminal 42b of the adjacent battery cell 41. Therefore, when a group of two consecutive battery cells 41 connected in series is used as the first detection target, as shown in Figure 3, wiring can be done on only one side of the Y direction for each first detection target. For this reason, by providing a pair of strip-shaped first substrate portions 83, the electrical path between each first detection target and the BMU 70 can be wired. In other words, it is not necessary to provide a second substrate portion 84 that extends across both ends in the Y direction for each first detection target. Thus, the substrate area can be reduced.

[0109] A second substrate portion 84 is provided near the battery cell 41, which is the second detection target C1. A region S1 is provided on the second substrate portion 84, enclosed by current output lines 81ap, 81an, voltage detection lines 82ap, 82an, positive terminal 42a, and negative terminal 42b. This reduces the induced electromotive force, allowing for accurate calculation of the impedance Z1 of the battery cell 41a, which is the second detection target C1.

[0110] Furthermore, the circuit board 80 is provided on the upper surface of the battery cell 41. This allows the circuit board 80 to be stably fixed in place.

[0111] (Second Embodiment) A second embodiment is described in which a part of the configuration of the battery monitoring system 50 of the first embodiment is modified. In cases where the configuration is the same as that of the first embodiment, the same reference numerals as in the first embodiment are used, and their detailed description is omitted.

[0112] As shown in Figure 15, the battery cells 141a to 141h constituting the battery pack 40 in the second embodiment are provided with power terminals 42 on their sides in the Y direction. Specifically, a positive terminal 142a is provided on one side of each battery cell 141, and a negative terminal 142b is provided on the other side. Furthermore, the positive terminal 142a and the negative terminal 142b are located in the central part of each battery cell 141 in the vertical direction (Z direction). Note that the battery cells 141a to 141h may be collectively referred to as battery cell 141.

[0113] Furthermore, as shown in Figures 18 and 19, the battery monitoring system 50 is equipped with impedance detection units 71a to 71h, similar to the first embodiment. The second impedance detection unit 71a differs from the first embodiment in that a current control unit 73 is provided inside the BMU 70, but the other configurations are the same as in the first embodiment. The impedance detection method and calculation method are also the same as in the first embodiment.

[0114] Next, the connection configuration between each battery cell 141a to 141h and the BMU 70 will be described. As shown in Figure 16, the battery cells 141a to 141h are arranged so that their positive terminal 142a and negative terminal 142b are staggered and aligned in the X direction. The battery cells 141a to 141h are connected in series by a busbar 43.

[0115] A circuit board 180 is provided on the Y-side of each of the battery cells 141a to 141h, and the battery cells are fixed to this side. In this embodiment, the circuit board 180 has current output lines 81 and voltage detection lines 82 wired to it, similar to the first embodiment. On the other hand, the circuit board 180 does not have a current control unit 73 mounted on it. The circuit board 180 is formed in an elongated shape so as to extend in the X-direction.

[0116] A pair of circuit boards 180 are positioned above the positive terminal 142a and negative terminal 142b, which are aligned in the X direction. As shown in Figure 16, the end of the circuit board 180 on the BMU 70 side in the X direction is bent and inserted into the connector 70a of the BMU 70. This electrically connects the electrical paths wired to the circuit board 180 with the BMU 70.

[0117] Next, we will explain the electrical path. First, we will explain the electrical path connecting the first impedance detection units 71b to 71h and the power terminal 142. As shown in Figures 17 and 18, the first impedance detection units 71b to 71h are connected to current output lines 81b to 81h and voltage detection lines 82b to 82h. In Figure 17, only one electrical path is shown in the Y direction, but the other electrical path is wired similarly. As can be understood by comparing Figure 17 and Figure 3, there is a difference between the Y and Z directions, but the wiring of the current output lines 81b to 81h and the voltage detection lines 82b to 82h in the first impedance detection units 71b to 71h is the same as in the first embodiment. For this reason, we will omit a detailed explanation by simply reinterpreting the Y and Z directions.

[0118] Next, the wiring of the current output line 181a and voltage detection line 182a connected to the second impedance detection unit 71a will be described. The current output line 181a and voltage detection line 182a are shown as dashed lines in Figure 17. Of the current output lines 181a, the positive-side current output line 181ap is connected to the positive terminal 42a of the battery cell 41a, which is the second detection target C1, via the busbar 43. This positive-side current output line 181ap is wired to extend straight in the X direction from the connection point with the busbar 43 and is connected to the BMU 70. Although not shown in the figure, the negative-side current output line 181an is wired similarly.

[0119] Of the voltage detection lines 182a, the positive electrode voltage detection line 182ap is connected to the positive terminal 42a of the battery cell 41a, which is the second detection target C1, via the busbar 43. The positive electrode voltage detection line 182ap is wired to extend straight in the X direction toward the BMU 70 from the connection point with the busbar 43. At this time, it is wired with a Z-direction offset so that it is parallel to the positive electrode current output line 181ap. Although not shown in the figure, the negative electrode voltage detection line 182an is wired similarly.

[0120] In other words, in the second embodiment, there is no region on the circuit board 180 enclosed by the current output line 181a, the voltage detection line 182a, the positive terminal 42a of the battery cell 41a, and the negative terminal 42b. Furthermore, in the second embodiment, the current control unit 73 is not located on the circuit board 180.

[0121] Next, the principle by which the induced electromotive force is reduced in the second embodiment will be explained. First, the mechanism by which the induced electromotive force can be reduced in the second embodiment by detecting the voltage of a cell group in which two consecutive battery cells 141 are connected in series will be explained with reference to Figures 20 to 22.

[0122] Figure 20 is a perspective view of two battery cells 141g and 141f connected in series, Figure 21 is a schematic plan view showing the current path flowing inside the two battery cells 141g and 141f connected in series, and Figure 22 is an unfolded view showing the region enclosed by the current path flowing inside the two battery cells 141g and 141f connected in series.

[0123] As shown in Figures 20 and 21, in two battery cells 141g and 141f connected in series, assuming that current flows along the current output line 81hp from point P24 (positive terminal 142a of battery cell 141g) to point P25, the current can be simplified by assuming that it flows from the negative terminal current output line 81gn (not shown) within the housing case 44 to point P21 (negative terminal 142b of battery cell 141f) → point P22 (positive terminal 142a of battery cell 141f) → point P23 (negative terminal 142b of battery cell 141g) → point P24 (positive terminal 142a of battery cell 141g).

[0124] Here, since the sides Sx of battery cell 141f and battery cell 141g in the X direction are facing each other, it is considered that the influence of magnetic flux passing through the region of the X-direction side Sx is canceled out, similar to the first embodiment. For this reason, the induced electromotive force generated by the magnetic flux passing through the sides Sx of battery cell 141f and battery cell 141g can be ignored.

[0125] Furthermore, in the second embodiment, the current output line 81gp is wired so as to pass approximately through the center in the Z direction on the side surface Sy in the Y direction of the battery cell 141 (the front side surface in Figure 20). When an alternating current flows through this current output line 81gp, a magnetic flux is generated clockwise (or counterclockwise) around the current output line 81gp. As shown in Figure 20, this magnetic flux enters from the top of the side surface Sy and returns from the bottom, so if we look at the side surface Sy as a whole, it can be considered that there is no increase or decrease in the magnetic flux passing through the side surface Sy. For this reason, the induced electromotive force generated by the magnetic flux passing through the Y-direction side surface Sy of the battery cell 141g can be ignored. Note that on the rear side surface in Figure 20, a busbar 43 is provided in the center in the Z direction, so similarly, the induced electromotive force can be ignored there as well.

[0126] Therefore, the region affected by the alternating current is considered to be the region S31 enclosed by points P24 → P23 → P22 → P21, as shown in Figure 21.

[0127] Assuming that the width dimension of the battery cell 141 in the Y direction is "La" and the distance in the X direction between the positive terminal 142a and the negative terminal 142b is "Lc", then, as shown in Figure 22, the area Sc of the region S31 enclosed by the current path is La × Lc. Generally, the distance Lc between the positive terminal 142a and the negative terminal 142b is much shorter than the width dimension La in the X direction and the width dimension Lb in the Z direction of the battery cell 141, and there is air (gap) with low magnetic permeability between the battery cells 141. From this, it can be considered that the area of ​​region S31 is much smaller than the area Sa (= La × Lb) of the region S2 enclosed by the current path in one battery cell 141. As a result of the smaller area of ​​the region through which the magnetic flux generated based on the alternating current passes, the induced electromotive force generated can be reduced compared to when detecting the impedance of each individual battery cell 141.

[0128] Next, in the second embodiment, a mechanism that can reduce induced electromotive force by arranging the power terminal 142 in the center of the side in the Z direction and detecting the voltage of the battery cell 141a located near the BMU 70 will be explained with reference to Figures 23 and 24. As a premise, as shown in Figure 23, the current output line 81a is wired to pass through the center in the Z direction even inside the BMU 70.

[0129] The current output line 81a is wired so as to pass approximately through the center in the Z direction on the side surface Sy of the battery cell 141 in the Y direction. When an alternating current flows through this current output line 81a, a magnetic flux is generated clockwise (or counterclockwise) around the current output line 81. As mentioned above, this magnetic flux enters from the upper side of the side surface Sy and returns from the lower side, so it can be considered that there is no increase or decrease in the magnetic flux passing through the side surface Sy as a whole. For this reason, the induced electromotive force generated by the magnetic flux passing through the Y-direction side surface Sy of the battery cell 41a can be ignored.

[0130] Similarly, the current output line 81a is wired to pass through the center in the Z direction inside the BMU 70. When alternating current flows through this current output line 81, a magnetic flux is generated clockwise (or counterclockwise) around the current output line 81. As mentioned above, this magnetic flux enters from the upper side of the side surface Sx of the battery cell 41a and returns from the lower side, so if we look at the entire side surface Sx, it can be considered that there is no increase or decrease in the magnetic flux passing through side surface Sx. For this reason, the induced electromotive force generated by the magnetic flux passing through the X-direction side surface Sx of the battery cell 41a can be ignored.

[0131] Therefore, the region affected by the alternating current is considered to be the region S32 enclosed by points P31 → P33 → P34, as shown in Figure 24.

[0132] If we assume that the width dimension of the battery cell 41 in the Y direction is "La" and the distance in the X direction between the power terminal 42 and the BMU 70 is "Ld", then the area Sd of the region S32 enclosed by the current path is La × Ld. Since the battery cell 141a is located closest to the BMU 70, the distance Ld between the power terminal 142 and the BMU 70 is also short. From this, it can be assumed that the area Sd of region S32 is much smaller than the area Sa (= La × Lb) of the region S2 enclosed by the current path in one battery cell 41. As a result of the smaller area through which the magnetic flux generated based on the alternating current passes, the induced electromotive force generated can be reduced compared to when the current output line 81 is wired on the upper surface side of the battery cell 41a, as in the first embodiment.

[0133] The effects of the battery monitoring system 50 of the second embodiment will be described below.

[0134] The positive terminal 142a and negative terminal 142b of the battery cell 141 are located in the middle of the vertical direction on the side surface of the battery cell 141. As described above, this further reduces the induced electromotive force when detecting the voltage of a cell group in which two consecutive battery cells 41 are connected in series.

[0135] The current output line 81 and the power terminal 142 are positioned in the center of the side in the Z direction, and the voltage of the battery cell 141a located near the BMU 70 is detected. As a result, the induced electromotive force can be reduced without providing a second substrate portion 84 having a region S1 surrounded by the current output line 81 and the voltage detection line 82. Therefore, the area of ​​the circuit board 180 can be reduced.

[0136] Furthermore, by fixing the circuit board 180 to the side of the battery pack 40, the vertical height of the battery pack 40 and the battery monitoring system 50 can be reduced.

[0137] (Third Embodiment) A third embodiment is described in which a part of the configuration of the battery monitoring system 50 of the second embodiment is modified. In cases where the configuration is the same as in the second embodiment, the same reference numerals as in the second embodiment are used, and their detailed description is omitted.

[0138] As shown in Figures 25 and 26, the current control unit 373 of the third embodiment is configured to supply alternating current to the entire battery pack 40 via a current output line 181. This eliminates the need for the current control unit 73 from each impedance detection unit 71a to 71h. Consequently, it is no longer necessary to provide a current output line 81 for each first detection target. Furthermore, it is no longer necessary to provide a current output line 81 for the second detection target. As a result, as shown in Figure 27, the amount of wiring can be reduced, further decreasing the board area of ​​the circuit board 180.

[0139] (Modification of the third embodiment) In the third embodiment described above, the entire battery pack 40 is used to output alternating current, but the alternating current may be output from a group of three or more battery cells 41 connected in series, or alternating current may be input to such a group of cells. In this case, it is necessary to control the system so that the same alternating current flows through each battery cell 41 with high precision.

[0140] (Fourth Embodiment) A fourth embodiment is described in which the configuration of the battery monitoring system 50 of the first embodiment is partially modified. In cases where the configuration is the same as that of the first embodiment, the same reference numerals as in the first embodiment are used, and their detailed description is omitted.

[0141] In the fourth embodiment, as shown in Figure 28, the battery cells 41a and 41h at both ends in the X direction of the battery cells 41a to 41h are designated as the second detection targets C1 and C8, respectively. Accordingly, a second impedance detection unit 171 is added to detect the impedance of the second detection target C8. The second impedance detection unit 171 has the same configuration as the second impedance detection unit 71a, except that the detection target is different.

[0142] Furthermore, as shown in Figure 29, a second substrate portion 84 is provided at both ends in the X direction. In Figure 29, on the left side in the X direction, the second substrate portion 84 also has a region S1 enclosed by current output lines 181ap, 181an, voltage detection lines 182ap, 182an, positive terminal 42a, and negative terminal 42b. As the wiring is substantially the same as in the first embodiment, as shown in Figure 29, the region S1 enclosed by current output lines 81ap, 81an, voltage detection lines 82ap, 82an, positive terminal 42a, and negative terminal 42b is the same as in the first embodiment, so the explanation will be omitted using the drawing.

[0143] Next, a method for calculating the impedance of each battery cell 41 in the fourth embodiment will be described. The first impedance detection units 71b to 71h detect the impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 of the first detection targets C12, C23, C34, C45, C56, C67, and C78. The second impedance detection unit 71a detects the impedance Z1 of the battery cell 41a, which is the second detection target C1. Similarly, the second impedance detection unit 171 detects the impedance Z8 of the battery cell 41h, which is the second detection target C8. These impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78, Z1, and Z8 are input to the calculation unit 76. The calculation unit 76 calculates the impedances Z1 to Z8 of each battery cell 41a to 41h based on these impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78, Z1, and Z8.

[0144] To explain in more detail, as shown in Figure 30, the calculation unit 76 calculates the impedance Z2 of battery cell 41b by subtracting impedance Z1 from impedance Z12. Next, the calculation unit 76 calculates the impedance Z3 of battery cell 41c by subtracting impedance Z2 from impedance Z23. Similarly, the calculation unit 76 calculates the impedance Z4 of battery cell 41d by subtracting impedance Z3 from impedance Z34.

[0145] Furthermore, the calculation unit 76 subtracts impedance Z8 from impedance Z78 to calculate the impedance Z7 of battery cell 41g. Next, the calculation unit 76 subtracts impedance Z7 from impedance Z67 to calculate the impedance Z6 of battery cell 41f. Similarly, the calculation unit 76 subtracts impedance Z6 from impedance Z56 to calculate the impedance Z5 of battery cell 41e.

[0146] The effects of the fourth embodiment will be described.

[0147] Although the induced electromotive force is reduced, the impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 still contain errors based on the induced electromotive force. Therefore, if the vector operation of subtracting impedances Z1 to Z7 from impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 is repeated as in the first embodiment, the error may accumulate and become larger with each repetition.

[0148] Therefore, as in the fourth embodiment, by setting the second detection target to two locations, the number of repetitions of the vector calculation can be reduced, as shown in Figure 30. This makes it possible to improve the detection accuracy of the impedance of each battery cell 41a to 41h.

[0149] (Modification of the fourth embodiment) - The structure of the fourth embodiment may be used to determine if there is an abnormality in the battery monitoring system 50. Specifically, as shown, the calculation unit 76 calculates the impedances Z1a to Z8a of each battery cell 41a to 41h from impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78 and impedance Z1. Similarly, the calculation unit 76 calculates the impedances Z1b to Z8b of each battery cell 41a to 41h from impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78 and impedance Z8. Then, the calculation unit 76 subtracts the impedances Z1b to Z8b from the impedances Z1a to Z8a to find the difference, and if all the differences are greater than or equal to a predetermined error range, it determines that there is some kind of abnormality in the battery monitoring system 50.

[0150] (Fifth Embodiment) A fifth embodiment is described in which the configuration of the battery monitoring system 50 of the second embodiment is partially modified. In cases where the configuration is the same as that of the second embodiment, the same reference numerals as in the second embodiment are used, and their detailed description is omitted.

[0151] In the second embodiment, a group of two consecutive battery cells 141 connected in series was used as the first detection target, but in the fourth embodiment, a group of four consecutive battery cells 141 connected in series is used as the first detection target. This will be explained in detail below.

[0152] As shown in Figure 31, the battery monitoring system 50 comprises a plurality of impedance detection units 71a to 71h, a calculation unit 76 that calculates the impedance of each battery cell 141a to 141h, and a current control unit 373. Note that the current control unit 373 is the same as in the third embodiment (see Figures 25 and 26), so its description is omitted.

[0153] Of the impedance detection units 71a to 71h, the impedance detection units 71d to 71h use a group of four consecutive battery cells 141 connected in series as the first detection target and detect the impedance of the first detection target. Hereinafter, in this embodiment, the impedance detection units 71d to 71h will be referred to as the first impedance detection units 71d to 71h.

[0154] Specifically, the first impedance detection unit 71d designates the cell group consisting of battery cells 141a to 141d as the first detection target C1234, the first impedance detection unit 71e designates the cell group consisting of battery cells 141b to 141e as the first detection target C2345, the first impedance detection unit 71f designates the cell group consisting of battery cells 141c to 141f as the first detection target C3456, the first impedance detection unit 71g designates the cell group consisting of battery cells 141d to 141g as the first detection target C4567, and the first impedance detection unit 71h designates the cell group consisting of battery cells 141e to 141h as the first detection target C5678. As described above, the first detection targets C1234, C2345, C3456, C4567, and C5678 are provided at multiple locations (five locations in this embodiment), and each of the first detection targets C1234, C2345, C3456, C4567, and C5678 is positioned with a one-cell offset in the X direction.

[0155] These first impedance detection units 71d to 71h detect the impedances Z1234, Z2345, Z3456, Z4567, and Z5678 of each of the first detection targets C1234, C2345, C3456, C4567, and C5678.

[0156] On the other hand, among the impedance detection units 71a to 71h, the impedance detection unit 71a detects the impedance Z1 of one battery cell 141a as the second detection target C1, as shown in Figures 31 and 33(a). The impedance detection unit 71b detects the impedance Z12 of two battery cells 141a and 141b as the second detection target C12. The impedance detection unit 71c detects the impedance Z123 of three battery cells 141a, 141b, and 141c as the second detection target C123.

[0157] Note that the impedance detection units 71a to 71h of the fifth embodiment have the same configuration as the first embodiment, differing only in the object being detected; therefore, the figures and descriptions are omitted.

[0158] The calculation unit 76 identifies the impedances Z1 to Z8 of each battery cell 141a to 141h based on the impedances Z1234, Z2345, Z3456, Z4567, Z5678, Z1, Z12, and Z123 detected by each impedance detection unit 71a to 71h.

[0159] To explain in more detail, the calculation unit 76 subtracts impedance Z1 from impedance Z12 to calculate the impedance Z2 of battery cell 41b. Next, the calculation unit 76 subtracts impedances Z1 and Z2 from impedances Z123 to calculate the impedance Z3 of battery cell 41c. Next, the calculation unit 76 subtracts impedances Z1, Z2, and Z3 from impedances Z1234 to calculate the impedance Z4 of battery cell 41d. Next, the calculation unit 76 subtracts impedances Z2, Z3, and Z4 from impedances Z2345 to calculate the impedance Z5 of battery cell 41e. The same calculation is repeated thereafter to calculate impedances Z6 to Z8. The calculation unit 76 notifies the ECU 60 or the like of the impedances Z1 to Z8 of each identified battery cell 41a to 41h.

[0160] Next, we will explain the mechanism for reducing induced electromotive force. Note that the mechanism for reducing induced electromotive force when detecting the voltage of a single battery cell 141a, and when detecting the voltages of two consecutive battery cells 141a and 141b, has been explained in the second embodiment and will be omitted here.

[0161] A mechanism for reducing the induced electromotive force when detecting the voltages of three consecutive battery cells 141a, 141b, and 141c will be explained with reference to Figure 32. As shown in Figure 32, the magnetic flux B3 passing through the region between battery cell 141c and battery cell 141b and the magnetic flux B2 passing through the region between battery cell 141b and battery cell 141a are in opposite directions, and the area of ​​each region is the same, so it is thought that the induced electromotive forces between them cancel each other out. Then, the only remaining induced electromotive force is the one based on the magnetic flux B1 passing through the region between battery cell 141a and BMU 70, which is essentially almost the same as the induced electromotive force when detecting the voltage of a single battery cell 141a. Thus, the induced electromotive force can be reduced.

[0162] Furthermore, the mechanism for reducing the induced electromotive force when detecting the voltage of four consecutive battery cells 141a and 141b is almost the same as the mechanism for reducing the induced electromotive force when detecting the voltage of two consecutive battery cells 141a and 141b.

[0163] (Modification of the fifth embodiment) In the fifth embodiment described above, the first detection target may be six or more, as long as the voltage of an even number of consecutive battery cells 141 is detected.

[0164] In the fifth embodiment described above, the voltage of one or more battery cells 141 was detected as shown in Figure 33(a). However, the voltage may be detected at any location as long as it is possible to detect the impedances Z1, Z2, and Z3 of the battery cells 141a to 141c that constitute the second detection target. For example, as shown in Figure 33(b), the voltage of each battery cell 141a to 141c may be detected, and the impedances Z1 to Z3 of each may be detected.

[0165] Alternatively, as shown in Figure 33(c), impedance Z1 may be detected from the voltage of one battery cell 141a, impedance Z23 from the voltages of two consecutive battery cells 141b and 141c, and impedance Z34 from the voltages of two consecutive battery cells 141c and 141d. In this case as well, the calculation unit 76 can calculate each impedance Z1 to Z4 from impedances Z1, Z23, Z34, and Z1234.

[0166] The location where voltage is detected can be determined by a system of equations where the impedances Z1 to Z4, along with impedances Z1, Z2, Z3, and Z4, are equal. A general mathematical rule is that the rank of matrix A, derived from the four detections, is equal to the rank of matrix A and b containing the detected values, and also equal to the number of rows m. Since the location detected by the voltage detection unit 72 is solely due to matrix A, the rank of matrix A representing the detection location of the voltage detection unit 72 should be equal to the number of cells detected (4 in this embodiment). As long as this condition is met, the number and location of detected cells can be arbitrary. Furthermore, this rule can be applied even if the number of detected battery cells 141 is not 4.

[0167] (Sixth Embodiment) A sixth embodiment is described in which the configuration of the battery monitoring system 50 of the first embodiment is partially modified. In cases where the configuration is the same as that of the first embodiment, the same reference numerals are used as in the first embodiment, and their detailed description is omitted.

[0168] As shown in Figure 34, in the sixth embodiment, impedance detection units 71a to 71c and 71d to 71h take a group of cells in which two consecutive battery cells 41 are connected in series as the first detection target and detect the impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 of the first detection target. Then, in the sixth embodiment, impedance detection unit 71d takes a single battery cell 41d as the second detection target and detects its impedance Z4.

[0169] Then, as shown in Figure 35, the calculation unit 76 calculates the impedances Z1 to Z8 from those impedances Z12, Z23, Z34, Z45, Z56, Z67, Z78, and Z4.

[0170] To explain in more detail, as shown in Figure 35, the calculation unit 76 calculates the impedance Z3 of battery cell 41c by subtracting impedance Z4 from impedance Z34. Next, the calculation unit 76 calculates the impedance Z2 of battery cell 41b by subtracting impedance Z3 from impedance Z23. Similarly, it calculates the impedance Z1 of battery cell 41a.

[0171] Furthermore, the calculation unit 76 subtracts impedance Z4 from impedance Z45 to calculate the impedance Z5 of battery cell 41e. Next, the calculation unit 76 subtracts impedance Z5 from impedance Z56 to calculate the impedance Z6 of battery cell 41f. The same calculation is repeated thereafter to calculate impedances Z7 to Z8.

[0172] This reduces the number of times calculations are repeated, thereby preventing errors from accumulating.

[0173] (Modification 1 of each embodiment) In the above embodiments and their modifications, one or more voltage fluctuations were detected and impedance was detected from the voltage. However, it is not necessary to detect impedance, and the system may be applied to a system that detects voltage.

[0174] Here, we will describe an example of Modification 1. Modification 1 is a modification of the battery monitoring system 50 of the first embodiment. In cases where the configuration is the same as in the first embodiment, the same reference numerals as in the first embodiment are used, and their detailed description is omitted.

[0175] For example, as shown in Figures 36 and 37, the voltage detection unit 172a detects the voltage V1 of the battery cell 41a. The voltage detection unit 172b detects the voltage V12 of two consecutive series-connected battery cells 41a and 41b. The voltage detection unit 172c detects the voltage V23 of two consecutive series-connected battery cells 41b and 41c. The voltage detection unit 172d detects the voltage V34 of two consecutive series-connected battery cells 41c and 41d. The voltage detection unit 172e detects the voltage V45 of two consecutive series-connected battery cells 41d and 41e. The voltage detection unit 172f detects the voltage V56 of two consecutive series-connected battery cells 41e and 41f. The voltage detection unit 172g detects the voltage V67 of two consecutive series-connected battery cells 41f and 41g. The voltage detection unit 172h detects the voltage V78 of two consecutively connected battery cells 41g and 41h.

[0176] The calculation unit 176 then calculates the voltages V1 to V8 from the detected voltages V1, V12, V23, V34, V45, V56, V67, and V78.

[0177] As a result, even if noise consisting of alternating current enters the electrical path from an external device such as an inverter 30, the induced electromotive force caused by that noise is suppressed, and the voltage can be detected with high accuracy.

[0178] The wiring method and board layout are the same as in the above embodiment. Furthermore, as another example of this modified example 1, four or more consecutive battery cells 41 may be used as the first detection target, as in the fifth embodiment. In this case as well, as in the fifth embodiment, the voltages of one or more consecutive battery cells 41 constituting the second detection target are detected at multiple locations, and the voltage of the first detection target and the voltage of each battery cell 41 can be calculated from these voltages.

[0179] (Modification 2 of each embodiment) In the above embodiments and their modifications, the purpose was to detect the impedance of each battery cell 41, 141, but the purpose may also be to detect abnormalities in the battery cells 41, 141.

[0180] Here, we will describe an example of Modification 2. Modification 2 is a modification of the battery monitoring system 50 of the first embodiment. In cases where the configuration is the same as in the first embodiment, the same reference numerals as in the first embodiment are used, and their detailed description is omitted.

[0181] In Modification 2, the impedance of each battery cell 41a to 41h is not calculated, and abnormalities are detected based on the difference in impedance. As shown in Figure 38, Modification 2 includes a first impedance detection unit 71b to 71h, but does not have a second impedance detection unit 71a. Accordingly, region S1 is eliminated, and the second substrate portion 84 is omitted.

[0182] Next, we will explain the method for detecting abnormalities.

[0183] Similar to the first embodiment, the first impedance detection units 71b to 71h detect the impedances Z12, Z23, Z34, Z45, Z56, Z67, and Z78 of the first detection targets C12, C23, C34, C45, C56, C67, and C78, ​​and input them to the determination unit 276.

[0184] The determination unit 276 determines whether or not there is an abnormality in any of the battery cells 41 based on the difference between the first voltages of adjacent first detection targets. More specifically, the determination unit 276 subtracts impedance Z23 from impedance Z12 to calculate the difference between impedance Z1 and impedance Z3 (Z1-Z3). If this difference (Z1-Z3) is greater than or equal to a predetermined threshold, and impedance Z1 is larger when comparing absolute values, it is determined that an abnormality has occurred in battery cell 41a, and if impedance Z3 is larger, it is determined that an abnormality has occurred in battery cell 41c.

[0185] Similarly, the determination unit 276 subtracts impedance Z34 from impedance Z23 to calculate the difference between impedance Z2 and impedance Z4 (Z2-Z4). If this difference (Z2-Z4) is greater than or equal to a predetermined threshold and impedance Z2 is larger when comparing absolute values, it is determined that an abnormality has occurred in battery cell 41b. If impedance Z4 is larger, it is determined that an abnormality has occurred in battery cell 41d. The determination unit 276 then determines abnormalities in the other battery cells 41 in the same manner.

[0186] According to this modified example 2, the induced electromotive force can be reduced and abnormalities in the battery cell 41 can be detected with a simple configuration.

[0187] (Modification 3 of each embodiment) In each of the above embodiments, the current control unit 73 outputs an alternating current from the battery cell 41, but the alternating current may be input (applied) to the battery cell 41. That is, an AC power source and a current control unit that controls the AC power source may be provided, and when detecting impedance, the current control unit may input a predetermined alternating current from the AC power source to the battery cell 41. Note that only the input and output of the alternating current change, and the impedance detection method and wiring are the same as in the above embodiments.

[0188] The following is an addendum detailing the technical ideas that can be derived from each embodiment and each variation. [Configuration 1] A battery monitoring system (50) comprising a battery monitoring device (70) for monitoring the state of a battery pack (40) composed of a plurality of battery cells (41, 41a to 41h, 141, 141a to 141h), wherein in the battery pack, the plurality of battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminals (42a, 142a) of each battery cell face the negative terminals (42b, 142b) of the adjacent battery cell, and the plurality of battery cells are connected in series by the connection of the positive terminal of each battery cell to the negative terminal of the adjacent battery cell, and the battery monitoring system comprises a voltage detection unit (72) that detects a cell group composed of some of the plurality of battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and the total voltage thereof as the first voltage.[Configuration 2] The system comprises a current control unit (73) that energizes a predetermined alternating current through the battery cells, detection units (74, 75) that detect impedance, and a calculation unit (76) that calculates the impedance of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of two of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit is configured to select one of the two battery cells that constitute one of the multiple first detection targets as the second detection target and to detect its voltage as the second voltage, the voltage detection unit detects the first voltage for each of the first detection targets when the predetermined alternating current is flowing through the current control unit, and detects the second voltage for the second detection target when the predetermined alternating current is flowing through the current control unit, the detection unit detects the first impedance for each of the first detection targets based on the detected first voltage and the energized predetermined alternating current, The battery monitoring system according to configuration 1, wherein the second impedance of the second detection target is detected based on the detected second voltage and the predetermined AC current that is supplied, and the calculation unit calculates the impedance of the battery cell itself from the first impedance of each of the first detection targets and the second impedance of the second detection target.[Configuration 3] The system comprises a current control unit (73) that supplies a predetermined alternating current to the battery cells, detection units (74, 75) that detect impedance, and a calculation unit (76) that calculates the impedance of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of four or more of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit detects the first voltage for each of the first detection targets when the predetermined alternating current is flowing by the current control unit, and the detection unit detects the first impedance for each of the first detection targets based on the detected first voltage and the supplied predetermined alternating current. The voltage detection unit is configured to select a group of batteries connected in series, excluding one battery cell located at the end in a predetermined direction, from among the plurality of battery cells constituting one of the plurality of first detection targets, as the second detection target, and to detect the voltage of one or a plurality of consecutive battery cells constituting the second detection target at multiple locations when a predetermined AC current is flowing by the current control unit; the detection unit detects the impedance of one or a plurality of consecutive battery cells constituting the second detection target based on the voltage of one or a plurality of consecutive battery cells constituting the second detection target detected by the voltage detection unit and the predetermined AC current; and the calculation unit calculates the impedance of a single battery cell from the first impedance for each of the first detection targets and the impedance of one or a plurality of consecutive battery cells constituting the second detection target, as described in Configuration 1.[Configuration 4] The battery monitoring system according to Configuration 2 or 3, wherein the positive and negative terminals of the battery cells are located at both ends of the battery cells in a direction perpendicular to the predetermined direction in which the battery cells are aligned, and when a plurality of the battery cells are arranged in alignment in the predetermined direction, the positive and negative terminals of each of the battery cells are also arranged in alignment in the predetermined direction, and the system includes a circuit board (80, 180) on which the alternating current flows (81, 81a to 81h, 81ap to 81hp, 81an to 81hn) and an electrical path (82, 82a to 82h, 82ap to 82hp, 82an to 82hn) connected to the voltage detection unit for detecting the voltage, and the circuit board has a pair of first board portions (83) at both ends of the battery cells, each configured to extend in the alignment direction of the positive and negative terminals of the plurality of battery cells. [Configuration 5] The battery monitoring system according to any one of Configurations 2 to 4, wherein the positive and negative terminals of the battery cell are located in the middle of the vertical direction on the side surface of the battery cell. [Configuration 6] The battery monitoring device is located at either end of the battery pack in the predetermined direction in which the battery cells are aligned, and the one or more battery cells that are the second target of detection are located on the battery monitoring device side of the battery pack in the predetermined direction. [Configuration 7] The battery monitoring system according to Configuration 4, wherein the circuit board has a second circuit board portion (84) that extends across both ends of the battery cell so as to connect a pair of first circuit board portions in the direction from the positive terminal to the negative terminal of the battery cell, the second circuit board portion is provided with a region (S1) surrounded by the positive terminal of the battery cell, the negative terminal, an electrical path through which alternating current flows, and an electrical path where voltage is detected, and the second circuit board is provided so as to be adjacent to the second target of detection in the predetermined direction. [Configuration 8] The battery monitoring system according to Configuration 7, wherein the positive and negative terminals of the battery cell are provided on the upper surface of the battery cell at both ends of the battery cell, and the circuit board is provided on the upper surface of the battery cell between the positive and negative terminals of the battery cell.[Configuration 9] The current control unit energizes the entire battery pack with the predetermined alternating current, as described in any of Configurations 2 to 8. [Configuration 10] The battery monitoring system according to Configuration 1, comprising: a voltage calculation unit (176) that calculates the voltage of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of two of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit is configured to select one of the two battery cells that constitute one of the multiple first detection targets as the second detection target and to detect its voltage as the second voltage, and the voltage calculation unit calculates the voltage of the battery cell itself from the detected first voltage and second voltage. [Configuration 11] A battery monitoring system according to Configuration 1, comprising: a voltage calculation unit (176) that calculates the voltage of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of four or more of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit detects the first voltage for each of the first detection targets when a predetermined AC current is flowing by the current control unit, the voltage detection unit is configured to set a group of cells in series, where a plurality of battery cells constituting any of the plurality of first detection targets are connected, excluding one battery cell located at the end in the predetermined direction, as the second detection target, and to detect the voltage of one or a plurality of consecutive battery cells constituting the second detection target at multiple locations, and the voltage calculation unit calculates the voltage of a single battery cell based on the first voltage for each of the first detection targets detected by the voltage detection unit and the voltage of one or a plurality of consecutive battery cells constituting the second detection target. [Configuration 12] The battery monitoring system according to any one of Configurations 2 to 11, wherein the second detection target is included in any of the first detection targets other than the first detection target which is located at the end of the battery pack in a predetermined direction.[Configuration 13] The battery monitoring system according to any of Configurations 2 to 12, wherein the second detection target is provided in two or more locations. [Configuration 14] The battery monitoring system according to Configuration 1, comprising: a current control unit (73) that energizes a predetermined alternating current through the battery cells; a detection unit that detects impedance; and a determination unit (276) that determines whether or not there is an abnormality in any of the battery cells constituting the battery pack, wherein the first detection target is provided in multiple locations, and each of the first detection target is arranged shifted by one cell in a predetermined direction, the voltage detection unit detects the first voltage for each of the first detection target when the current control unit is energizing a predetermined alternating current, the detection unit calculates the first impedance for each of the first detection target based on the detected first voltage and the energized predetermined alternating current, and the determination unit determines whether or not there is an abnormality in any of the battery cells based on the difference between the impedances of adjacent first detection targets. [Configuration 15] A battery monitoring system according to any one of Configurations 1 to 14, wherein the total number of battery cells constituting the first detection target is less than or equal to half the total number of battery cells constituting the battery pack. [Configuration 16] A battery monitoring device (70) for monitoring the state of a battery pack (40) composed of a plurality of battery cells (41, 41a to 41h, 141, 141a to 141h), wherein in the battery pack, the plurality of battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminals (42a, 142a) of each battery cell face the negative terminals (42b, 142b) of the adjacent battery cell, and the plurality of battery cells are connected in series by the connection of the positive terminal of each battery cell to the negative terminal of the adjacent battery cell, and the battery monitoring device has a voltage detection unit (72) that detects a cell group composed of some of the plurality of battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and the total voltage thereof as the first voltage.

[0189] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A battery monitoring system (50) comprising a battery monitoring device (70) for monitoring the state of a battery pack (40) composed of multiple battery cells (41, 41a to 41h, 141, 141a to 141h), wherein in the battery pack, the multiple battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminals (42a, 142a) of each battery cell face the negative terminals (42b, 142b) of adjacent battery cells, and the multiple battery cells are connected in series by the connection of the positive terminal of each battery cell to the negative terminal of adjacent battery cells, and the battery monitoring system comprises a voltage detection unit (72) that detects a cell group composed of some of the multiple battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and the total voltage thereof as the first voltage.

2. The device comprises a current control unit (73) that energizes a predetermined alternating current through the battery cells, detection units (74, 75) that detect impedance, and a calculation unit (76) that calculates the impedance of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of two of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit is configured to select one of the two battery cells that constitute one of the multiple first detection targets as a second detection target and to detect its voltage as a second voltage, the voltage detection unit detects the first voltage for each of the first detection targets when the predetermined alternating current is flowing through the current control unit, and detects the second voltage for the second detection target when the predetermined alternating current is flowing through the current control unit, the detection unit detects the first impedance for each of the first detection targets based on the detected first voltage and the energized predetermined alternating current, The battery monitoring system according to claim 1, wherein the second impedance for the second detection target is detected based on the detected second voltage and the predetermined AC current that has been energized, and the calculation unit calculates the impedance of the battery cell itself from the first impedance for each of the first detection targets and the second impedance for the second detection target.

3. The device comprises a current control unit (73) that energizes a predetermined alternating current through the battery cells, detection units (74, 75) that detect impedance, and a calculation unit (76) that calculates the impedance of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of four or more of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit detects the first voltage for each of the first detection targets when the predetermined alternating current is flowing through the current control unit, and the detection unit detects the first impedance for each of the first detection targets based on the detected first voltage and the energized predetermined alternating current. The voltage detection unit is configured to select a group of batteries connected in series, excluding one battery cell located at the end in a predetermined direction, from among the plurality of battery cells constituting one of the plurality of first detection targets, as the second detection target, and to detect the voltage of one or a plurality of consecutive battery cells constituting the second detection target at multiple locations when a predetermined AC current is flowing by the current control unit; the detection unit detects the second impedance of one or a plurality of consecutive battery cells constituting the second detection target based on the voltage of one or a plurality of consecutive battery cells constituting the second detection target detected by the voltage detection unit and the predetermined AC current; and the calculation unit calculates the impedance of a single battery cell from the first impedance for each of the plurality of first detection targets and the second impedance of one or a plurality of consecutive battery cells constituting the second detection target, as described in claim 1.

4. The battery monitoring system according to claim 2 or 3, wherein the positive and negative terminals of the battery cells are located at both ends of the battery cell in a direction perpendicular to the predetermined direction in which the battery cells are aligned, and when a plurality of the battery cells are arranged in alignment in the predetermined direction, the positive and negative terminals of each of the battery cells are also arranged in alignment in the predetermined direction, and the system comprises a circuit board (80, 180) on which the alternating current flows (81, 81a to 81h, 81ap to 81hp, 81an to 81hn) and the electrical paths (82, 82a to 82h, 82ap to 82hp, 82an to 82hn) connected to the voltage detection unit for detecting the voltage, and the circuit board has a pair of first substrate portions (83, 183) at both ends of the battery cell, respectively configured to extend in the alignment direction of the positive and negative terminals of the plurality of battery cells.

5. The battery monitoring system according to claim 4, wherein the positive and negative terminals of the battery cell are located on the side surface of the battery cell, in the middle portion in the vertical direction.

6. The battery monitoring system according to claim 5, wherein the battery monitoring device is located at either end of the battery pack in the predetermined direction in which the battery cells are aligned, and the one or more battery cells to be detected are located on the battery monitoring device side of the battery pack in the predetermined direction.

7. The battery monitoring system according to claim 4, wherein the circuit board has a second substrate portion (84) that extends across both ends of the battery cell so as to connect a pair of first substrate portions in the direction from the positive terminal to the negative terminal of the battery cell, the second substrate portion is provided with a region (S1) surrounded by the positive terminal of the battery cell, the negative terminal, an electrical path through which alternating current flows, and an electrical path through which voltage is detected, and the second substrate is provided so as to be adjacent to the second detection target in the predetermined direction.

8. The battery monitoring system according to claim 7, wherein the positive and negative terminals of the battery cell are provided on the upper surface of the battery cell at both ends of the battery cell, and the circuit board is provided on the upper surface of the battery cell between the positive and negative terminals of the battery cell.

9. The battery monitoring system according to claim 2 or 3, wherein the current control unit energizes the entire battery pack with the predetermined alternating current.

10. A battery monitoring system according to claim 1, comprising: a voltage calculation unit (176) for calculating the voltage of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of two of the battery cells, each of the first detection targets is arranged with one cell offset in the predetermined direction, the voltage detection unit is configured to select one of the two battery cells constituting any of the multiple first detection targets as a second detection target and detect its voltage as a second voltage, and the voltage calculation unit calculates the voltage of the battery cell itself from the detected first voltage and second voltage.

11. A battery monitoring system according to claim 1, comprising: a voltage calculation unit (176) for calculating the voltage of each of the battery cells, wherein the first detection targets are provided at multiple locations and consist of four or more of the battery cells, each of the first detection targets is arranged with one cell offset in a predetermined direction, the voltage detection unit detects the first voltage for each of the first detection targets when a predetermined AC current is flowing by the current control unit, the voltage detection unit designates a group of cells in series, consisting of multiple battery cells from among the multiple battery cells constituting one of the multiple first detection targets, excluding one battery cell located at the end in a predetermined direction, as a second detection target, and is configured to detect the voltage of one or more consecutive battery cells constituting the second detection target at multiple locations, and the voltage calculation unit calculates the voltage of a single battery cell based on the first voltage for each of the first detection targets detected by the voltage detection unit and the second voltage of one or more consecutive battery cells constituting the second detection target.

12. The battery monitoring system according to any one of claims 2, 3, 10, or 11, wherein the second detection target is included in any of the first detection targets other than the first detection target which is located at the end of the battery pack in a predetermined direction.

13. The battery monitoring system according to any one of claims 2, 3, 10, or 11, wherein the second detection target is provided in two or more locations.

14. A battery monitoring system according to claim 1, comprising: a current control unit (73) that energizes a predetermined alternating current through a battery cell; a detection unit that detects impedance; and a determination unit (276) that determines whether or not there is an abnormality in any of the battery cells constituting the battery pack, wherein the first detection targets are provided at multiple locations, and each of the first detection targets is arranged shifted by one cell in a predetermined direction; the voltage detection unit detects a first voltage for each of the first detection targets when a predetermined alternating current is flowing through the current control unit; the detection unit calculates a first impedance for each of the first detection targets based on the detected first voltage and the energized predetermined alternating current; and the determination unit determines whether or not there is an abnormality in any of the battery cells based on the difference between the first impedances of adjacent first detection targets.

15. The battery monitoring system according to any one of claims 2, 3, 10, 11, or 14, wherein the total number of battery cells constituting the first detection target is less than or equal to half the total number of battery cells constituting the battery pack.

16. A battery monitoring device (70) for monitoring the state of a battery pack (40) composed of multiple battery cells (41, 41a to 41h, 141, 141a to 141h), wherein in the battery pack, the multiple battery cells are arranged in a predetermined direction, and the positive and negative terminals of each battery cell are arranged alternately such that the positive terminals (42a, 142a) of each battery cell face the negative terminals (42b, 142b) of adjacent battery cells, and the multiple battery cells are connected in series by connecting the positive terminal of each battery cell to the negative terminal of adjacent battery cells, and the battery monitoring device has a voltage detection unit (72) that detects a cell group composed of some of the multiple battery cells, in which an even number of consecutive battery cells are connected in series, as the first detection target, and the total voltage thereof as the first voltage.

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