Battery monitoring device

Abstract

A battery monitoring device (50) is applied to a battery pack (40) in which a plurality of battery cells (42) are connected in series and monitors the states of the respective battery cells. The battery monitoring device (50) causes an alternating current to flow through each battery cell, and includes: a voltage acquisition unit (62) that acquires voltage fluctuations (Vi) of each battery cell when the alternating current flows; an arithmetic unit (61) that calculates an impedance (Zi) and a phase difference (θi) for each battery cell based on the alternating current and the voltage fluctuations; and a current control unit (90) that designates an amplitude (Isi) and a phase (θsi) of the alternating current for each battery cell. The current control unit specifies at least one of the amplitude and the phase of the alternating current based on the calculated impedance and phase difference such that a total value (Vt) of the voltage fluctuations becomes below a threshold value, and makes the designation.

Description

[0001] Cross - reference to related applications

[0002] This application is based on Japanese Patent Application No. 2019 - 197376 filed on October 30, 2019, the contents of which are incorporated herein by reference. Technical field

[0003] The present disclosure relates to a battery monitoring device. Background art

[0004] Conventionally, in order to monitor the state of a storage battery, the complex impedance of the storage battery is measured (for example, Patent Documents 1 and 2). In the disclosure described in Patent Document 1, a rectangular wave signal (alternating current) is applied to the storage battery by a power controller, and the response signal (voltage change) is subjected to Fourier transform. Based on the obtained result, the complex impedance characteristics are calculated. Then, based on the complex impedance characteristics, the deterioration state of the storage battery is discriminated.

[0005] In addition, in Patent Document 2, a sine wave current (alternating current) is made to flow from an oscillator to the storage battery, and the response signal (voltage change) is detected by a lock - in amplifier. Based on the detection result, the complex impedance characteristics are calculated. Further, based on the complex impedance characteristics, the deterioration state of the storage battery is discriminated.

[0006] Prior art documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6226261

[0009] Patent Document 2: Japanese Patent Application Laid - Open No. 2018 - 190502 Summary of the invention

[0010] However, the response signal generated from the storage battery may become noise. That is, when the response signal propagates as external noise, there is a case where radio noise is generated. In addition, other devices may malfunction due to the noise.

[0011] The present disclosure has been made in view of the above - mentioned technical problems, and an object thereof is to provide a battery monitoring device capable of suppressing noise.

[0012] A means for solving the above technical problem is that in a battery monitoring device applied to a battery pack in which a plurality of battery cells including an electrolyte and a plurality of electrodes are connected in series and the states of the respective battery cells are monitored, the battery monitoring device includes: a current generation unit that causes an alternating current to flow through each of the battery cells; a voltage acquisition unit that acquires voltage fluctuations of each of the battery cells when the alternating current flows; an arithmetic unit that calculates an impedance of each of the battery cells and a phase difference between the alternating current and the voltage fluctuation for each of the battery cells based on the alternating current flowing through each of the battery cells and the voltage fluctuation acquired by the voltage acquisition unit; and a current control unit that designates an amplitude and a phase of the alternating current to the current generation unit for each of the battery cells, and the current control unit specifies at least one of the amplitude and the phase of the alternating current flowing through each of the battery cells based on the impedance and the phase difference of each of the battery cells calculated by the arithmetic unit so that a total value of voltage fluctuations of the respective battery cells becomes equal to or less than a threshold value, and designates at least one of the specified amplitude and phase of the alternating current to each battery cell.

[0013] In the above structure, at least one of the amplitude and the phase of the alternating current flowing through each of the battery cells is specified based on the impedance and the phase difference of each of the battery cells calculated by the arithmetic unit so that a total value of voltage fluctuations of the respective battery cells becomes equal to or less than a threshold value. Therefore, even if a noise suppression circuit such as a filter is not provided, voltage fluctuations of the entire battery pack can be suppressed and noise can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above objects, other objects, features, and advantages of the present disclosure can be made clearer by referring to the drawings and the following detailed description. The drawings are as follows.

[0015] Figure 1 is a schematic structural diagram of a power supply system.

[0016] Figure 2 is a structural diagram of a battery monitoring device.

[0017] Figure 3 is a structural diagram of an impedance detection unit.

[0018] Figure 4 is a vector diagram showing an existing alternating current and voltage fluctuations.

[0019] Figure 5 is a vector diagram showing an alternating current and voltage fluctuations.

[0020] Figure 6 is a flowchart showing a process flow of impedance detection.

[0021] Figure 7 It is a vector diagram showing the AC current and voltage variations of the second embodiment.

[0022] Figure 8 It is a vector diagram showing the AC current and voltage variations of the third embodiment.

[0023] Figure 9 It is a flowchart showing the process of the specified value setting process in the third embodiment.

[0024] Figure 10 It is a vector diagram showing the AC current and voltage variations of the fourth embodiment.

[0025] Figure 11 It is a diagram showing the voltage variation of the fourth embodiment.

[0026] Figure 12 It is a flowchart showing the process of the specified value setting process in the fourth embodiment.

[0027] Figure 13 It is a vector diagram showing the AC current and voltage variations of the fifth embodiment.

[0028] Figure 14 It is a diagram showing the voltage variation of the fifth embodiment.

[0029] Figure 15 It is a flowchart showing the process of the impedance detection process in the fifth embodiment. Detailed Embodiments

[0030] (First Embodiment)

[0031] Hereinafter, with reference to the drawings, a first embodiment of applying a "battery monitoring device" to a power supply system of a vehicle (for example, a hybrid vehicle or an electric vehicle) will be described.

[0032] As Figure 1 shown, the power supply system 10 includes: a motor 20 as a rotating electric machine; an inverter 30 as a power converter through which three-phase current flows to the motor 20; a battery pack 40 capable of charging and discharging; a battery monitoring device 50 that monitors the state of the battery pack 40; and an ECU 100 that controls the motor 20 and the like.

[0033] The motor 20 can transmit power to a drive wheel (not shown). In the present embodiment, a three-phase permanent magnet synchronous motor is used as the motor 20.

[0034] The inverter 30 is composed of a full-bridge circuit with upper and lower arms. The number of the upper and lower arms is the same as the number of phases of the phase windings. The on and off of switches (semiconductor switching elements such as IGBTs) provided in each arm are used to adjust the energizing current in each phase winding.

[0035] An inverter control device (not shown) is provided in the inverter 30. Based on various detection information in the motor 20, requests for power running drive and power generation, the inverter control device performs energization control by turning on and off each switch in the inverter 30. Thus, the inverter control device supplies power from the battery pack 40 to the motor 20 via the inverter 30 to drive the power running of the motor 20. In addition, the inverter control device 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, thereby charging the battery pack 40.

[0036] The battery pack 40 is electrically connected to the motor 20 via the inverter 30. The battery pack 40 has, for example, an inter-terminal voltage of more than one hundred volts and is composed of a plurality of battery modules 41 connected in series. The battery module 41 is composed of a plurality of battery cells 42 connected in series. As the battery cell 42, for example, a lithium-ion storage battery or a nickel-metal hydride storage battery can be used. Each battery cell 42 is a storage battery having an electrolyte and a plurality of electrodes. In the present embodiment, the battery module 41 is composed of six battery cells 42 connected in series.

[0037] The positive terminal of an electrical load such as the inverter 30 is connected to the positive power supply path L1 connected to the positive power supply terminal of the battery pack 40. Similarly, the negative terminal of an electrical load such as the inverter 30 is connected to the negative power supply path L2 connected to the negative terminal of the battery pack 40. In addition, relay switches SMR (system main relay switches) are respectively provided on the positive power supply path L1 and the negative power supply path L2, and are configured to be able to switch between energization and power-off.

[0038] The battery monitoring device 50 is a device that monitors the state of charge (SOC) and the state of deterioration (SOH) of each battery cell 42, etc. The battery monitoring device 50 is connected to the ECU 100 and outputs the state of each battery cell 42, etc. The structure of the battery monitoring device 50 will be described later.

[0039] The ECU 100 makes requests for power running drive and power generation for the inverter control device based on various information. The various information includes, for example, the operation information of the accelerator and the actuator, the vehicle speed, the state of the battery pack 40, etc.

[0040] Next, the battery monitoring device 50 will be described in detail. As Figure 2As shown, in the first embodiment, the battery monitoring device 50 is provided with an impedance detection unit 60 for each battery cell 42. Further, in the battery monitoring device 50, information on each battery cell 42 is input from each impedance detection unit 60, and a control device 90 as a current control unit for instructing each impedance detection unit 60 is provided.

[0041] Based on Figure 3 The impedance detection unit 60 will be described. The impedance detection unit 60 includes an arithmetic device 61 as an arithmetic unit and a lock-in amplifier 62 as a current generation unit and a voltage acquisition unit. The arithmetic device 61 has a function of instructing the lock-in amplifier 62 according to an instruction from the control device 90 and acquiring various information on the battery cell 42 to be monitored via the lock-in amplifier 62. Further, the arithmetic device 61 has functions of performing arithmetic operations based on the acquired various information, outputting an arithmetic result to the control device 90, etc. The detailed structure of the arithmetic device 61 will be described later.

[0042] Next, the lock-in amplifier 62 will be described. The lock-in amplifier 62 includes an oscillation circuit 71, a DA converter 72, an AD converter 73, a current modulation circuit 74, a differential amplifier circuit 75, an AD converter 76, a phase shift circuit 77, a first multiplier 78, a first integrator 79, a first filter 80, a second multiplier 81, a second integrator 82, and a second filter 83.

[0043] The oscillation circuit 71 is connected to the arithmetic device 61, and is a circuit that outputs a sine wave signal set according to an instruction from the arithmetic device 61. The oscillation circuit 71 is connected to the first multiplier 78 and the phase shift circuit 77, and outputs the sine wave signal as a first reference signal to the first multiplier 78 and the phase shift circuit 77. Further, the oscillation circuit 71 is connected to the current modulation circuit 74 via the DA converter 72, and outputs the sine wave signal as an instruction signal to the current modulation circuit 74.

[0044] The current modulation circuit 74 is a circuit that causes a specified alternating current (sine wave signal) to flow out (output) using the battery cell 42 to be monitored as a power source. Specifically, the current modulation circuit 74 has: a semiconductor switching element 74a (e.g., MOSFET); and a resistor 74b connected in series with the semiconductor switching element 74a. The drain terminal of the semiconductor switching element 74a is connected to the positive terminal of the battery cell 42, and the source terminal of the semiconductor switching element 74a is connected in series with one end of the resistor 74b. Further, the other end of the resistor 74b is connected to the negative terminal of the battery cell 42. The semiconductor switching element 74a is configured to be able to adjust the amount of current passing between the drain terminal and the source terminal.

[0045] In addition, a current detection amplifier 74c is provided at both ends of a resistor 74b in the current modulation circuit 74. The current detection amplifier 74c is configured to detect the current flowing through the resistor 74b and output it as a feedback signal. The above feedback signal is converted into a digital signal (feedback signal If) via an AD converter 73 and output to the arithmetic unit 61.

[0046] In addition, a feedback circuit 74d is provided in the current modulation circuit 74. The feedback circuit 74d is configured to input an indication signal from the oscillation circuit 71 via a DA converter 72 and input a feedback signal from the current detection amplifier 74c. In addition, it is configured to compare the indication signal with the feedback signal and output the comparison result to the gate terminal of the semiconductor switching element 74a.

[0047] Based on the signal from the feedback circuit 74d, the semiconductor switching element 74a adjusts the voltage applied between the gate and the source to adjust the current amount between the gate and the source, so that an alternating current (sine wave signal) indicated by the indication signal is output from the battery cell 42. In addition, when an error occurs between the waveform indicated by the indication signal and the current waveform actually flowing through the resistor 74b, the semiconductor switching element 74a adjusts the current amount based on the signal from the feedback circuit 74d to correct the error. Thereby, the alternating current (sine wave signal) flowing through the resistor 74b (i.e., the battery cell 42) is stabilized.

[0048] The differential amplifier circuit 75 is connected to the battery cell 42 to be monitored. The differential amplifier circuit 75 has a function of inputting, amplifying, and outputting a voltage change reflecting the internal complex impedance information of the battery cell 42 between the terminals of the battery cell 42 when an alternating current flows through the battery cell 42. In addition, the differential amplifier circuit 75 is configured to be connected to an AD converter 76 and output the input voltage change (response signal) to a first multiplier 78 and a second multiplier 81 via the AD converter 76, respectively.

[0049] The first multiplier 78 multiplies the first reference signal input from the oscillation circuit 71 by the voltage change (response signal) and outputs it to the first integrator 79. The first integrator 79 averages the value input from the first multiplier 78 and outputs it to the arithmetic unit 61 via a first filter 80 that is a low-pass filter. The value output from the first filter 80 to the arithmetic unit 61 is a value corresponding to the real part of the voltage change. In addition, the value corresponding to the real part of the voltage change is represented as Re_Vi (i = 1, 2... 6).

[0050] The second multiplier 81 is connected to the oscillation circuit 71 via the phase shift circuit 77 and receives the second reference signal. The second reference signal is a signal that advances the phase of the first reference signal by 90 degrees (π / 2). The phase shift circuit 77 advances the phase of the sine wave signal (first reference signal) input from the oscillation circuit 71 and outputs it as the second reference signal.

[0051] The second multiplier 81 multiplies the second reference signal by the voltage variation (response signal) and outputs the result to the second integrator 82. The second integrator 82 averages the value input from the second multiplier 81 and outputs it to the arithmetic unit 61 via the second filter 83 which acts as a low-pass filter. The value input to the arithmetic unit 61 via the second filter 83 is a value corresponding to the imaginary part of the voltage variation. Additionally, the value corresponding to the imaginary part of the voltage variation is denoted as Im_Vi (i = 1, 2... 6).

[0052] The arithmetic unit 61 is a microcomputer including a CPU, memory (RAM, ROM), etc., and is configured to be capable of performing various arithmetic processes. For example, the arithmetic unit 61 obtains Re_Vi (i = 1, 2... 6) and Im_Vi (i = 1, 2... 6) from the filters 80, 83, and based on these values and the amplitude Is of the alternating current, calculates the impedance Zi (more specifically, the absolute value |Zi|) and the phase difference θi using mathematical formulas (11) - (13). Additionally, the phase difference θi refers to the phase difference between the phase of the alternating current and the phase of the voltage variation (response signal). Furthermore, in this embodiment, the amplitude Is of the alternating current is based on the instruction (amplitude specified value Isi) from the arithmetic unit 61 to the lock-in amplifier 62, but it can also be based on the feedback signal If.

[0053] [Mathematical formula 1]

[0054]

[0055] θi = arctan(Re_Vi / Im_Vi) ··· (12)

[0056] |zi| = |vi| / |Is| ··· (13)

[0057] The arithmetic unit 61 outputs the calculated impedance Zi and phase difference θi to the control device 90. The control device 90 stores them. In addition, the control device 90 obtains the impedance Zi and phase difference θi (frequency characteristics of complex impedance) at multiple frequencies by scanning the frequency (measurement frequency fs) of the alternating current output from the battery cell 42 within a specified measurement range. Next, the control device 90 creates a Cole-Cole plot (Japanese: コールコールプロット) based on the above calculation results to grasp the characteristics of the electrode and electrolyte, etc. For example, the state of charge (SOC) and state of degradation (SOH) are grasped, and the results are output to the ECU 100. Additionally, although illustration and detailed description are omitted, the arithmetic unit 61 is configured to be able to obtain the voltage (DC voltage) between the terminals of the battery cell 42.

[0058] As described above, the impedance Zi of the battery cell 42 is calculated based on the voltage variation of the battery cell 42. Next, the voltage variations of each battery cell 42 are each a weak variation. However, the battery pack 40 is formed by connecting a plurality of battery cells 42 in series. Therefore, there is a possibility that the voltage variations are superimposed, resulting in a large voltage variation and becoming noise.

[0059] Here, based on Figure 4 The form of voltage variation superposition will be described. Hereinafter, the voltage variation Vi of the battery cell 42 when an alternating current flows may sometimes be represented as the voltage variation Vi. Additionally, in Figure 4 the voltage variation Vi is represented as a vector. Additionally, in Figure 4 for simplicity of explanation, it is assumed that the battery cells 42 constituting the battery pack 40 are two, namely the first battery cell 42a and the second battery cell 42b, and the explanation is made. Additionally, the explanation is made with the state of degradation and state of charge of the first battery cell 42a and the second battery cell 42b being different. Additionally, in Figure 4 it is assumed that the same alternating current is output from the first battery cell 42a and the second battery cell 42b. Specifically, the amplitude specified values Is1 and Is2 of the alternating current output from the first battery cell 42a and the second battery cell 42b are both set to "Ia". Similarly, the phases of the alternating current output from the first battery cell 42a and the second battery cell 42b are both set to zero (set as the reference).

[0060] As Figure 4As shown, even if the same alternating current is output from the first battery cell 42a and the second battery cell 42b, due to different battery states, the amplitudes (sizes) of the voltage variations V1 of the first battery cell 42a and V2 of the second battery cell 42b are different. That is, since the impedances Z1 and Z2 of the first battery cell 42a and the second battery cell 42b are different, the magnitudes of the voltage variations V1 and V2 proportional thereto are also different. For the same reason, the magnitudes of the phase differences θ1 between the voltage variation V1 of the first battery cell 42a and the alternating current and θ2 between the voltage variation V2 of the second battery cell 42b and the alternating current are different.

[0061] Therefore, the sum Vt (sum of vector values) of the voltage variations V1 and V2 is not zero, and depending on the situation, it becomes larger than each of the voltage variations V1 and V2. Therefore, when alternating current is output synchronously from each battery cell 42, there is a possibility of generating relatively large noise from the battery pack 40.

[0062] However, it is known that the impedance Zi and the phase difference θi of each battery cell 42 depend on the state of charge (SOC), the state of deterioration (SOH), etc., and as long as the measurement frequency remains unchanged, they do not change significantly in the short term. Thus, in the first embodiment, the control device 90 specifies (calculates) the amplitude specified value Isi and the phase specified value θsi of the alternating current flowing through each battery cell 42 based on the calculated impedance Zi and phase difference θi of each battery cell 42 so that the sum value of the voltage variations Vi of each battery cell 42 is below a threshold value. Then, the control device 90 assigns the specified amplitude specified value Isi and the phase specified value θsi thus specified to each battery cell 42.

[0063] Specifically, how the control device 90 specifies the specified values (amplitude specified value Isi and phase specified value θs) will be described. First, the battery cells 42 constituting the battery pack 40 (more specifically, the battery module 41) are divided into one group or multiple groups. At this time, each group includes at least two or more battery cells 42. Additionally, grouping may be done in advance.

[0064] Next, the control device 90 determines the amplitude specified value Isi and the phase specified value θsi of the alternating current to be output from each battery cell 42 in such a way that the voltage variations Vi of the battery cells 42 included in each group cancel each other out and the sum value approaches zero.

[0065] In the present embodiment, the amplitude specified value Isi of the alternating current is determined based on the impedance Zi of each battery cell 42 such that the amplitudes of the voltage fluctuations Vi of the battery cells 42 included in the group are exactly the same. That is, the impedance Zi and the voltage fluctuation Vi are in a proportional relationship. Therefore, when any one of the battery cells 42 included in the group is used as a reference and the amplitude specified value Isi of the alternating current output from the reference battery cell 42 is set to "Ia", if the reciprocal ratio (Japanese: inverse ratio) of the impedance Za of the reference battery cell 42 to the impedance Zb of the target battery cell 42 is taken, that is, if Ia×(Za / Zb) is calculated, the amplitude specified value Ib of the alternating current that should be output from the target battery cell 42 can be specified.

[0066] Next, as in the present embodiment, when the amplitudes of the voltage fluctuations Vi of the battery cells 42 included in the group are exactly the same, the phase specified value θsi is determined such that the deviation of the phases of the voltage fluctuations Vi in each of the battery cells 42 in the group is the same (equally spaced). That is, as described above, the phase difference θi represents the phase difference between the voltage fluctuation Vi and the alternating current. Therefore, the phase specified value θsi is determined by dividing 360° by the number of battery cells 42 included in the group and staggering the phases of the voltage fluctuations Vi by the calculated value. That is, considering the phase difference θa of the voltage fluctuation Va in the reference battery cell 42, the phase difference θb of the voltage fluctuation Vb in the target battery cell 42, and the calculated phase deviation, the phase specified value θsb of the alternating current output from the target battery cell 42 is determined.

[0067] Here, based on Figure 5 A specific description of the above determination method will be given. In Figure 5 , it is assumed that the group includes two battery cells 42, namely the first battery cell 42a and the second battery cell 42b, for explanation. In addition, the impedance of the first battery cell 42a calculated in the previous time (i.e., the latest) is set to "Z1", and the phase difference θi is set to "θ1". Similarly, the impedance of the second battery cell 42b calculated in the previous time (i.e., the latest) is set to "Z2", and the phase difference θi is set to "θ2". In addition, the amplitude specified value Isi of the alternating current output from the first battery cell 42a is set to "Is1", and the phase specified value θsi is set to "θs1". In addition, the amplitude specified value Isi of the alternating current output from the second battery cell 42b is set to "Is2", and the phase specified value θsi is set to "θs2". In addition, in Figure 5 , with the alternating current flowing through the first battery cell 42a as a reference, the voltage fluctuation Vi, the alternating current, and the impedance Zi are represented as vectors on the complex plane.

[0068] First, in order to make the voltage change V1 of the first battery cell 42a equal to the voltage change V2 of the second battery cell 42b, the amplitude specified value Is2 of the alternating current to be output from the second battery cell 42b can be specified by the following formula (14).

[0069] Is2 = Is1 × Z1 / Z2 ··· (14)

[0070] In addition, when the amplitude of the voltage change V1 of the first battery cell 42a is the same as the amplitude of the voltage change V2 of the second battery cell 42b, in order to cancel out the voltage changes with each other, it is necessary to shift the phase of the voltage change V1 and the voltage change V2 by 180°. That is to say, it is necessary to shift the phase of the voltage changes V1 and V2 by an amount equal to the value specified by dividing 360° by the number of battery cells "2".

[0071] Therefore, if the alternating current output from the first battery cell 42a is used as a reference, the phase specified value θs2 of the alternating current to be output from the second battery cell 42b can be specified by the following formula (15). In addition, the phase specified value θs1 of the alternating current output from the first battery cell 42a is set to "0".

[0072] θs2 = θ1 + 180° - θ2 ··· (15)

[0073] Next, based on Figure 6 , the impedance detection process performed by the control device 90 of the present embodiment will be described. The impedance detection process is configured to be executed at a specified time (for example, when the system is started, etc.). In addition, in the present embodiment, the battery module 41 to be monitored by the battery monitoring device 50 includes six battery cells 42, and hereinafter, it may be expressed as the first battery cell 42a to the sixth battery cell 42f. In addition, the first battery cell 42a to the sixth battery cell 42f are divided into three groups G1, G2, and G3. The group G1 includes the first battery cell 42a and the second battery cell 42b, the group G2 includes the third battery cell 42c and the fourth battery cell 42d, and the group G3 includes the fifth battery cell 42e and the sixth battery cell 42f.

[0074] In addition, the amplitude specified values Isi of the alternating current output from the first battery cell 42a to the sixth battery cell 42f may be respectively expressed as the amplitude specified values Is1 to Is6, and the phase specified values θsi may be respectively expressed as the phase specified values θs1 to θs6. In addition, the impedances Zi of the first battery cell 42a to the sixth battery cell 42f are respectively expressed as the impedances Z1 to Z6, and the phase differences θi are respectively expressed as the phase differences θ1 to θ6.

[0075] When starting the impedance detection process, the control device 90 sets initial values as the amplitude specified value Isi and the phase specified value θsi of the alternating current output from each battery cell 42 (step S101). The initial values can be arbitrary values, but it is preferable to set the initial values in a manner that suppresses the possibility of noise. For example, ideally, the specified values that make the alternating current outputs from the paired battery cells 42 within the groups G1 to G3 have the same amplitude and opposite phases are set as the initial values.

[0076] Specifically, as the initial values of the amplitude specified values Is1 to Is6 of the alternating current output from the first battery cell 42a to the sixth battery cell 42f, the same value "Ic" is set respectively. In addition, "Ic" is an arbitrary value. Furthermore, as the initial values of the phase specified values θs1, θs3, and θs5 of the alternating current output from the first battery cell 42a, the third battery cell 42c, and the fifth battery cell 42e, 0° is set respectively. As the initial values of the phase specified values θs2, θs4, and θs6 of the alternating current output from the second battery cell 42b, the fourth battery cell 42d, and the sixth battery cell 42f, 180° is set respectively.

[0077] In addition, the control device 90 sets the initial values as the frequency of the alternating current (measurement frequency fs) (step S102). The measurement frequency fs is configured to be determined from a specified measurement range, and the initial value in this embodiment is set as the minimum value in the measurement range.

[0078] In addition, the control device 90 outputs (indicates) the amplitude specified values Is1 to Is6, the phase specified values θs1 to θs6, and the measurement frequency fs to the respective impedance detection units 60 of the first battery cell 42a to the sixth battery cell 42f, indicating the detection of impedance (step S103).

[0079] In addition, when starting the impedance detection process and executing the first step S103, as the amplitude specified values Is1 to Is6 and the phase specified values θs1 to θs6, the control device 90 outputs the initial values set in step S101 respectively. Similarly, when starting the impedance detection process and executing the first step S103, as the measurement frequency fs, the control device 90 outputs the initial value set in step S102.

[0080] On the other hand, when executing the steps S103 after the second time, as the amplitude specified values Is1 to Is6 and the phase specified values θs1 to θs6, the control device 90 outputs the values set in the following step S105 respectively. Similarly, when executing the steps S103 after the second time, as the measurement frequency fs, the control device 90 outputs the value set in the following step S107.

[0081] When the amplitude specified values Is1 to Is6, the phase specified values θs1 to θs6, and the measurement frequency fs are output respectively, each impedance detection unit 60 causes an alternating current to be output from the first battery cell 42a to the sixth battery cell 42f based on the above specified values.

[0082] In addition, each impedance detection unit 60 inputs the voltage variations V1 to V6 of the first battery cell 42a to the sixth battery cell 42f based on the alternating current respectively, and calculates the impedances Z1 to Z6 and the phase differences θ1 to θ6 as described above based on the voltage variations V1 to V6, for output to the control device 90.

[0083] The control device 90 inputs (acquires) the calculation results (the impedances Z1 to Z6 and the phase differences θ1 to θ6) (step S104). Then, the control device 90 proceeds to step S105 to perform the specified value setting process. That is, the control device 90 specifies (calculates) the amplitude specified values Is1 to Is6 and the phase specified values θs1 to θs6 of the alternating current flowing through each battery cell 42 based on the calculated impedances Z1 to Z6 and the phase differences θ1 to θ6 of each battery cell 42 in such a manner that the sum value of the voltage variations V1 to V6 of each battery cell 42 becomes below the threshold value (step S105).

[0084] Specifically, the amplitude specified value Is and the phase specified value θs are specified based on the following mathematical formulas (16) to (27). In addition, in mathematical formulas (16) to (21), "Id" is an arbitrary value, which can be the same as the initial value or different from the initial value.

[0085] Is1 = Id ··· (16)

[0086] Is2 = Is1 × Z1 / Z2 ··· (17)

[0087] Is3 = Id ··· (18)

[0088] Is4 = Is3 × Z3 / Z4 ··· (19)

[0089] Is5 = Id ··· (20)

[0090] Is6 = Is5 × Z5 / Z6 ··· (21)

[0091] θs1 = 0° ··· (22)

[0092] θs2 = θ1 + 180° - θ2 ··· (23)

[0093] θs3 = 0° ··· (24)

[0094] θs4 = θ3 + 180° - θ4 ··· (25)

[0095] θs5 = 0° ··· (26)

[0096] θs6 = θ5 + 180° - θ6 ··· (27)

[0097] When the impedance detection process is not finished, the amplitude specified values Is1 to Is6 and the phase specified values θs1 to θs6 set in step S105 are output in the next step S103. In addition, the control device 90 determines whether all the frequencies within the measurement range have been scanned as the measurement frequency fs (step S106). Specifically, it is determined whether all the frequencies within the measurement range have been scanned by determining whether the measurement frequency fs is consistent with the maximum value of the measurement range.

[0098] When the above determination result is affirmative, the control device 90 ends the impedance detection process. On the other hand, when the determination result in step S106 is negative, the control device 90 updates the measurement frequency fs (step S107) and executes the process of step S103 again. The update method is arbitrary. For example, a new measurement frequency fs can be set by adding a specified value to the measurement frequency fs. In addition, when the added specified value is large, since the impedance or the like may change significantly, it is desirable that the change range of the measurement frequency fs is as small as possible.

[0099] As described above, the battery monitoring device 50 of the first embodiment has the following effects.

[0100] Based on the impedance Zi and the phase difference θi of the battery cell 42 calculated by the arithmetic device 61 in such a way that the total value of the voltage variations Vi of each battery cell 42 becomes zero, the amplitude specified value Isi and the phase specified value θsi of the alternating current flowing through each battery cell 42 are specified.

[0101] More specifically, taking the first battery cell 42a included in the group G1 as a reference, the amplitude specified value Isi of the alternating current output from the first battery cell 42a as the reference is set to "Id". Then, by taking the reciprocal ratio of the impedance Z1 of the first battery cell 42a as the reference and the impedance Z2 of the second battery cell 42b included in the group G1 in such a way that the amplitudes of the voltage variations V1 and V2 of each battery cell 42 are the same, the amplitude specified value Is2 of the alternating current to be output from the second battery cell 42b is specified.

[0102] Specifically, based on the impedances Z1 to Z6 of each battery cell 42 obtained (i.e., the latest) in the previous step S104, in step S105, the amplitude specified value Is1 of the first battery cell 42a and the amplitude specified value Is2 of the second battery cell 42b are specified by mathematical expressions (16) and (17). In addition, the same is done for the other groups G2 and G3.

[0103] In addition, the phase specified values θs1 and θs2 are determined in such a way that the phase deviations of the respective voltage fluctuations V1 and V2 in the first battery cell 42a and the second battery cell 42b within the group G1 are the same (equally spaced). Specifically, based on the phase differences θ1 to θ6 of each battery cell 42 input (i.e., the latest) in the previous step S104, in step S105, the phase specified value θs1 of the first battery cell 42a and the phase specified value θs2 of the second battery cell 42b are specified by mathematical expressions (22) and (23). In addition, the same is done for the other groups G2 and G3.

[0104] By the above, even without providing a noise suppression circuit such as a filter, it is possible to suppress the voltage fluctuations of the entire battery pack 40 and suppress noise.

[0105] In addition, the same value "Ic" is set as the initial values of the amplitude specified values Is1 to Is6 of the alternating current output from the first battery cell 42a to the sixth battery cell 42f. In addition, the initial values of the phase specified values θs1 and θs2 are set in such a way that the alternating current output from the first battery cell 42a and the alternating current output from the second battery cell 42b paired with the first battery cell 42a are in antiphase. The same setting is also made for the respective initial values of the other phase specified values θs3 to θs6. Thereby, even in a situation where the impedance Zi and the phase difference θi are not detected, it is possible to suppress the generation of noise as much as possible.

[0106] The measurement frequency fs is updated by increasing a prescribed value each time. Thereby, compared with the case where the measurement frequency fs is randomly determined within the measurement range, it is possible to suppress noise.

[0107] (Second Embodiment)

[0108] In the first embodiment, the number of battery cells 42 included in the group is two, but it may also be three. Hereinafter, with reference to the drawings, the second embodiment will be described centering on the differences from the first embodiment. In the second embodiment, the same reference numerals are given to the structures that are the same as those described in the first embodiment, and the description thereof is omitted.

[0109] Based on Figure 7Specifically describe the determination method of the second embodiment. In addition, in the second embodiment, it is described that the first battery cell 42a to the sixth battery cell 42f are divided into two groups G1 and G2, and the group G1 includes the first battery cell 42a, the second battery cell 42b, and the third battery cell 42c. In addition, it is described that the group G2 includes the fourth battery cell 42d, the fifth battery cell 42e, and the sixth battery cell 42f. In addition, the determination method of the group G2 is the same as that of the group G1. Therefore, the determination method of the group G1 is described as the center, and the determination method of the group G2 is omitted.

[0110] Figure 7 In this case, the impedances Zi of the first battery cell 42a to the third battery cell 42c obtained (input) through the previous step S104 are respectively set as "Z1" to "Z3". Similarly, the phase differences θi obtained (input) through the previous step S104 are respectively set as "θ1" to "θ3". In addition, Figure 7 In this case, with the alternating current output from the first battery cell 42a as the reference, the voltage variation Vi, the alternating current, and the impedance Zi are represented as vectors on the complex plane.

[0111] First, in order to make the voltage variations V1 of the first battery cell 42a, V2 of the second battery cell 42b, and V3 of the third battery cell 42c equal, the amplitude specified value Is2 of the alternating current that should be output from the second battery cell 42b can be specified by the following formulas (30) and (31). Similarly, the amplitude specified value Is3 of the alternating current that should be output from the third battery cell 42c can be specified by the following formulas (30) and (32). In addition, in the following formula (30), "Id" is an arbitrary number.

[0112] Is1 = Id ··· (30)

[0113] Is2 = Is1 × Z1 / Z2 ··· (31)

[0114] Is3 = Is1 × Z1 / Z3 ··· (32)

[0115] In addition, when making the amplitudes of the voltage variations V1 to V3 within the group G1 the same, in order to cancel out the voltage variations V1 to V3 with each other, it is necessary to stagger the phases of the voltage variations V1, V2, and V3 by the same angle (120°). That is, it is necessary to stagger the phases of the voltage variations V1, V2, and V3 by the amount of the value obtained by dividing 360 by the number "3" of the battery cells 42 within the group G1.

[0116] Therefore, when taking the alternating current output from the first battery cell 42a as a reference, the phase specified value θs2 of the alternating current to be output from the second battery cell 42b can be specified by the following formulas (33) and (34). Similarly, the phase specified value θs3 of the alternating current to be output from the third battery cell 42c can be specified by the following formulas (34) and (35).

[0117] θs1 = 0° ··· (33)

[0118] θs2 = θ1 + 120° - θ2 ··· (34)

[0119] θs3 = θ1 + 240° - θ3 ··· (35)

[0120] With the above settings, as Figure 7 shown, the sum Vt of the voltage fluctuations V1, V2, and V3 can be made close to zero, suppressing noise. Through the above, even if the number of battery cells 42 constituting the battery pack 40 or the group is either even or odd, noise can be suppressed.

[0121] (Third Embodiment)

[0122] Hereinafter, with reference to the drawings, the third embodiment will be described centering on the differences from the first embodiment. In the third embodiment, the same reference numerals are given to the structures that are the same as those described in the first embodiment, and the description thereof is omitted.

[0123] In the third embodiment, it is configured to change the amplitude of the alternating current output from each battery cell 42 according to the state of each battery cell 42, thereby simultaneously performing the equalization process for each battery cell 42. The equalization process is a process of causing a part of the battery cells 42 with a higher state of charge to discharge more than the other battery cells 42 in such a way that the state of charge of each battery cell 42 is made consistent.

[0124] In the third embodiment, the description will be made by dividing the first battery cell 42a to the sixth battery cell 42f into two groups G1 and G2, and the group G1 includes the first battery cell 42a, the second battery cell 42b, and the third battery cell 42c. In addition, the description will be made by the group G2 including the fourth battery cell 42d, the fifth battery cell 42e, and the sixth battery cell 42f. In addition, since the determination method of the group G2 is the same as that of the group G1, the description will be centered on the determination method of the group G1, and the determination method of the group G2 is omitted. In addition, the control device 90 of the third embodiment is configured to be able to acquire the state of charge of the battery cell 42 and function as a state detection unit.

[0125] In addition, similarly to the second embodiment, the impedances Zi of the first battery cell 42a to the third battery cell 42c obtained (input) in the previous step S104 are respectively set to "Z1" to "Z3", and the phase differences θi are respectively set to "θ1" to "θ3". In addition, based on the alternating current output from the first battery cell 42a, the voltage variation Vi, the alternating current, and the impedance Zi are vectorially represented in Figure 8 In

[0126] In Figure 9 the designation value setting process of step S105 of the third embodiment is shown. The control device 90 determines whether equalization processing is required for each of the groups G1 and G2 (step S301). For example, when the state of charge of any one of the battery cells 42 in the groups G1 and G2 is equal to or higher than a predetermined value, it is determined that equalization processing is required.

[0127] When the determination result is negative, similarly to the second embodiment, the control device 90 determines the amplitude designation values Is1 to Is6 so that the voltage variations Vi are equal, and in addition, determines the phase designation values θs1 to θs6 so that the phases are shifted by a predetermined angle (step S302).

[0128] On the other hand, when the determination result in step S301 is positive, the control device 90 specifies the battery cell 42 with the highest state of charge in the groups G1 and G2 (step S303). That is, the battery cell 42 to be discharged in the groups G1 and G2 is specified.

[0129] In addition, the control device 90 determines that the amplitude designation values Is1 to Is6 of the alternating current output from the battery cell 42 with the highest state of charge are larger than those of the other battery cells 42 (step S304).

[0130] For example, when the first battery cell 42a is specified as the battery cell 42 to be discharged in step S303 of the third embodiment, the amplitude designation values Is1 to Is3 are determined by the following formulas (41) to (43). In formula (41), "Id" is an arbitrary number. In addition, in a normal battery cell 42, Z1 / Z2 and Z1 / Z3 do not become 2 or more. Therefore, the amplitude designation value Is1 is larger than the other amplitude designation values Is2 and Is3.

[0131] Is1 = 2 × Id ··· (41)

[0132] Is2 = Id × Z1 / Z2 ··· (42)

[0133] Is3 = Id × Z1 / Z3 ··· (43)

[0134] In addition, the case where the first battery cell 42a is specified as the discharging battery cell 42 is illustrated, but the same applies to the cases where the second battery cell 42b and the third battery cell 42c are discharging. Further, the amplitude designation values Isi are determined in the same manner in the group G2.

[0135] Next, the control device 90 calculates the phase designation values θs1 to θs6 (step S305) based on the amplitude designation values Is1 to Is6 determined in step S303, the impedances Z1 to Z6 acquired in the previous step S104, and the phase differences θ1 to θ6 such that the sum value of the voltage variations Vi of the respective battery cells 42 becomes below the threshold value. That is, the control device 90 determines the phase designation values θs1 to θs6 such that the voltage variations V1 to V6 cancel each other out.

[0136] In step S303 of the third embodiment, when the first battery cell 42a is specified as the discharging battery cell 42 as described above, the voltage variation V1 becomes twice the other voltage variations V2 and V3.

[0137] Therefore, in order to cancel out the voltage variations V1 to V3, the phase designation values θs1 to θs3 can be determined such that the phase difference between the voltage variation V1 and the voltage variation V2 is 150°, the phase difference between the voltage variation V1 and the voltage variation V3 is 210°, and the phase difference between the voltage variation V2 and the voltage variation V3 is 60°. That is, the phase designation values θs1 to θs3 of the alternating current can be determined as shown in the following equations (44) to (46).

[0138] θs1 = 0° ··· (44)

[0139] θs2 = θ1 + 150° - θ2 ··· (45)

[0140] θs3 = θ1 + 210° - θ3 ··· (46)

[0141] In addition, the case where the first battery cell 42a is specified as the discharging battery cell 42 is illustrated, but the same applies to the cases where the second battery cell 42b and the third battery cell 42c are discharging. Further, the phase designation values θsi are determined in the same manner in the group G2.

[0142] Next, the designation value setting process of step S105 is ended. With the above settings, as Figure 8As shown, it is possible to make the sum Vt of the voltage fluctuations V1, V2, and V3 approach zero, suppressing noise. In addition, the amplitude of the alternating current output from the first battery cell 42a is larger than that of the second battery cell 42b and the third battery cell 42c. Therefore, it is possible to make the discharge amount of the first battery cell 42a larger than that of the second battery cell 42b and the third battery cell 42c to perform equalization. Thus, it is possible to make the charge storage states of the respective battery cells 42 consistent, thereby suppressing overcharging of a part of the battery cells 42.

[0143] In addition, since the impedance is detected while performing equalization, the discharge current from the battery cell 42 is not wasted, and power consumption can be suppressed.

[0144] In addition, in the above-described third embodiment, the amplitude specified value of the alternating current output from the first battery cell 42a (the battery cell 42 that should be discharged the most) can be arbitrarily changed as long as it is larger than the amplitude specified values of the other alternating currents. In this case, the phase specified value θs needs to be appropriately determined such that the sum value of the voltage fluctuations Vi becomes below the threshold value (for example, zero).

[0145] In addition, in the third embodiment, the amplitude specified value of the alternating current output from the battery cell 42 with the highest charge storage state is made larger than the other amplitude specified values. As another example, it is also possible to make the amplitude specified values of the alternating currents output from a plurality of battery cells 42 larger than the other amplitude specified values. For example, in the third embodiment, it is also possible to make the amplitude specified values Is1 and Is2 of the alternating currents output from the first battery cell 42a and the second battery cell 42b higher than the amplitude specified value Is3. In this case, the phase specified value θsi needs to be appropriately determined such that the sum value of the voltage fluctuations Vi becomes below the threshold value (for example, zero).

[0146] (Fourth Embodiment)

[0147] Hereinafter, with reference to the drawings, the fourth embodiment will be described centering on the differences from the first embodiment. In the fourth embodiment, the same reference numerals are given to the structures that are the same as those described in the first embodiment, and the description thereof is omitted.

[0148] In the first to third embodiments, if the impedance Zi is different for each battery cell 42, the amplitude of the alternating current output from the battery cell 42 is different. For example, in the case of calculating the amplitude specified values Is1 and Is2 based on Mathematical Formulas (16) and (17), if the impedances Z1 and Z2 are different, the amplitude specified values Is1 and Is2 are also different. In this case, the discharge amount is different for each battery cell 42, and unevenness in the charge storage states of the respective battery cells 42 may occur.

[0149] Therefore, in the fourth embodiment, on the basis of making the amplitude specified value Is of the alternating current output from each battery cell 42 the same, the phase specified value θsi is determined such that the total value of the voltage fluctuations Vi becomes equal to or less than a threshold value (for example, zero).

[0150] First, an explanation will be given based on Figure 10 and Figure 11 of the principle. In addition, in the fourth embodiment, the description will be given by dividing the first battery cell 42a to the sixth battery cell 42f into two groups G1 and G2, with the group G1 including the first battery cell 42a, the second battery cell 42b, and the third battery cell 42c. Further, the description will be given with the group G2 including the fourth battery cell 42d, the fifth battery cell 42e, and the sixth battery cell 42f. In addition, since the determination method of the group G2 is the same as that of the group G1, the description will be centered on the determination method of the group G1, and the determination method of the group G2 will be omitted.

[0151] In addition, in the same manner as in the second embodiment, the impedances Zi of the first battery cell 42a to the third battery cell 42c obtained (input) through the previous step S104 are respectively set to "Z1" to "Z3", and the phase differences θi are respectively set to "θ1" to "θ3". In addition, with the alternating current output from the first battery cell 42a as a reference, in Figure 10 the voltage fluctuations Vi, the alternating current, and the impedance Zi are represented in vector form.

[0152] As Figure 10 shown, when the amplitude specified values Is1 to Is3 of the alternating current output from each battery cell 42 are made the same, the differences in the impedances Z1 to Z3 cause differences in the amplitudes of the voltage fluctuations V1 to V3. However, by appropriately changing the phase differences θ12 between the voltage fluctuations V1 and V2, the phase difference θ23 between the voltage fluctuations V2 and V3, and the phase difference θ31 between the voltage fluctuations V3 and V1, as Figure 11 shown, the voltage fluctuations V1 to V3 can be made to cycle (configured cyclically). That is, it is possible to make the end point of the voltage fluctuation V1 coincide with the start point of the voltage fluctuation V2, the end point of the voltage fluctuation V2 coincide with the start point of the voltage fluctuation V3, and the end point of the voltage fluctuation V3 coincide with the start point of the voltage fluctuation V1.

[0153] In the case of making the voltage fluctuations V1 to V3 cycle as described above, the sum of the voltage fluctuations V1 to V3 (vector values) is zero, and the voltage fluctuations V1 to V3 can be made to cancel each other out. In addition, each of the phase differences θ12, θ23, θ31 can be adjusted by appropriately setting the phase specified value θsi while considering each of the phase differences θ1 to θ3. Hereinafter, based on Figure 12 the specified value setting process of step S105 in the fourth embodiment adopting the above principle will be described.

[0154] After the process of step S104 is completed, the control device 90 sets arbitrary identical values (for example, Id) as the amplitude specified values Is1 to Is3 of the alternating current flowing through each battery cell 42 (step S401).

[0155] Next, the control device 90 calculates the magnitudes (absolute values, scalar values) of the voltage fluctuations V1 to V3 of each battery cell 42 based on the latest impedances Z1 to Z3 of each battery cell 42 obtained in step S104 and the amplitude specified values Is1 to Is3 set in step S401 (step S402).

[0156] Next, the control device 90 calculates the phase difference θ12 between the voltage fluctuation V1 and the voltage fluctuation V2 and the phase difference θ31 between the voltage fluctuation V3 and the voltage fluctuation V1 based on mathematical expressions (51) and (52) (step S403). Additionally, in mathematical expressions (51) and (52), V1 to V3 are the values calculated in step S402.

[0157] [Mathematical Expression 2]

[0158]

[0159]

[0160] Furthermore, the control device 90 calculates the phase specified values θs1 to θs3 based on the phase differences θ12 and θ31 calculated in step S403 through mathematical expressions (51) and (52) and the latest phase differences θ1 to θ3 obtained in step S104 (step S404). Then, the specified value setting process of step S105 is completed.

[0161] θs1 = 0 ··· (53)

[0162] θs2 = θ1 + (180° - θ12) - θ2 ··· (54)

[0163] θs3 = θ1 + (180° + θ31) - θ3 ··· (55)

[0164] With the above configuration, it is possible to make the total value (vector total value) of the voltage fluctuations V1 to V3 approach zero and suppress noise. At the same time, it is possible to make the amplitudes of the alternating current output from each battery cell 42 the same and make the discharge amounts the same for each battery cell 42. That is to say, when detecting the impedance, it is possible to suppress unevenness in the charged states of each battery cell 42.

[0165] (Fifth Embodiment)

[0166] Hereinafter, with reference to the drawings, the fifth embodiment will be described centering on the differences from the first embodiment. In the fifth embodiment, the same reference numerals are assigned to the structures that are the same as those described in the first embodiment, and the description thereof will be omitted.

[0167] In the fourth embodiment, the amplitude designation value Is is always the same, but in the case where equalization processing is required, the amplitude designation value Is may be different. Even in the above case, if the phase designation value θsi is appropriately set, the total value of the voltage fluctuations can be suppressed below the threshold value (for example, zero).

[0168] Based on Figure 13 and Figure 14 the principle will be described. In addition, in the fifth embodiment, the first battery cell 42a to the sixth battery cell 42f are divided into two groups G1 and G2, and the description will be made with the group G1 including the first battery cell 42a, the second battery cell 42b, and the third battery cell 42c. In addition, the description will be made with the group G2 including the fourth battery cell 42d, the fifth battery cell 42e, and the sixth battery cell 42f. In addition, since the group G2 is determined in the same manner as the group G1, the description will be centered on the determination method of the group G1, and the determination method of the group G2 will be omitted.

[0169] In addition, in the same manner as in the second embodiment, the impedances Zi of the latest first battery cell 42a to the third battery cell 42c obtained (input) in the previous step S104 are respectively set to "Z1" to "Z3", and the phase differences θi are respectively set to "θ1" to "θ3". In addition, with the alternating current output from the first battery cell 42a as a reference, in Figure 13 the voltage fluctuations Vi, the alternating current, and the impedance Zi are represented in vector form.

[0170] As Figure 13 shown, even when the magnitude of the amplitude designation value Is1 of the alternating current output from each battery cell 42 is larger than the other amplitude designation values Is2 and Is3, by appropriately changing the phase differences θ12, θ23, and θ31, as Figure 14 shown, it is possible to make the voltage fluctuations V1 to V3 circulate (configured cyclically). That is, it is possible to make the end point of the voltage fluctuation V1 coincide with the start point of the voltage fluctuation V2, make the end point of the voltage fluctuation V2 coincide with the start point of the voltage fluctuation V3, and make the end point of the voltage fluctuation V3 coincide with the start point of the voltage fluctuation V1.

[0171] In the case where the voltage fluctuations V1 to V3 are made to circulate as described above, the sum of the voltage fluctuations V1 to V3 (vector values) is zero, and the voltage fluctuations can be canceled. In addition, each phase difference θ12, θ23, and θ31 can be adjusted by appropriately setting the phase designation value θsi in consideration of each phase difference θ1 to θ3.

[0172] Hereinafter, the structure of the battery monitoring device 50 according to the fifth embodiment adopting the above principle and the impedance detection process of the fifth embodiment will be described. In the fifth embodiment, the control device 90 is configured to be able to obtain the impedance Zi and the voltage change Vi from the impedance detection unit 60.

[0173] Next, based on Figure 15 The impedance detection process will be described. When starting the impedance detection process, in the same manner as step S102 of the first embodiment, the control device 90 sets an initial value as the measurement frequency fs (step S501).

[0174] Next, the control device 90 sets the amplitude specified values Is1 to Is3 of the alternating current output from the battery cells 42 (step S502). In step S502, when it is determined that the equalization process is not required, the control device 90 sets the same value as the amplitude specified values Is1 to Is3. On the other hand, when it is determined that the equalization process is required, the amplitude specified value Isi of the alternating current output from the battery cell 42 to be discharged is made larger than the other amplitude specified values Isi.

[0175] Next, the control device 90 determines whether the initial value is set for the measurement frequency fs (step S503). That is, it is determined whether it is the first detection of the impedances Z1 to Z3 and the like after the start of the impedance detection process.

[0176] When the determination result in step S503 is affirmative, the control device 90 proceeds to the process of step S504, and based on equations (61) to (62), calculates the phase differences θ12 and θ31 in such a manner that the alternating currents Is1 to Is3 flowing through the first battery cell 42a to the third battery cell 42c circulate (step S504).

[0177] In addition, the alternating currents flowing through the first battery cell 42a to the third battery cell 42c and the voltage changes V1 to V3 are in substantially the same phase, and thus can be calculated in the same manner as when the voltage changes V1 to V3 circulate. In addition, the reason for using the amplitude specified value Isi set in step S502 in equations (61) to (62) is as follows: Since it is the first time, the voltage changes V1 to V3 have not been obtained in step S508 described below.

[0178] [Mathematical formula 3]

[0179]

[0180]

[0181] On the other hand, when the determination result in step S503 is negative, the control device 90 proceeds to the process of step S505, and calculates phase differences θ12 and θ31 based on formulas (63) to (64) (step S505). In addition, in formulas (63) to (64), voltage fluctuations V1 to V3 are the latest voltage fluctuations V1 to V3 obtained in the previous step S508.

[0182] [Mathematical formula 4]

[0183]

[0184]

[0185] Next, the control device 90 calculates phase specified values θs1 to θs3 based on formulas (65) to (67) (step S506). More specifically, the phase specified values θs1 to θs3 are calculated such that the sum (vector value) of voltage fluctuations V2 and V3 is in antiphase with voltage fluctuation V1. In addition, in formulas (65) to (67), θ12 and θ31 calculated in step S504 or step S505 are used.

[0186] θs1 = 0 ··· (65)

[0187] θs2 = θ1 + (180° - θ12) - θ2 ··· (66)

[0188] θs3 = θ1 + (180° + θ31) - θ3 ··· (67)

[0189] In addition, the control device 90 respectively instructs each impedance detection unit 60 of the first battery cell 42a to the third battery cell 42c to detect amplitude specified values Is1 to Is3, phase specified values θs1 to θs3, and measurement frequency fs, and to detect impedances Z1 to Z3, etc. (step S507).

[0190] When the amplitude specified values Is1 to Is3, the phase specified values θs1 to θs3, and the measurement frequency fs are respectively output, each impedance detection unit 60 outputs an alternating current from the first battery cell 42a to the third battery cell 42c based on the above specified values.

[0191] In addition, each impedance detection unit 60 respectively inputs voltage fluctuations V1 to V3 of the first battery cell 42a to the third battery cell 42c based on the alternating current, calculates impedances Z1 to Z3 and phase differences θ1 to θ3 as described above based on voltage fluctuation Vi, and outputs them to the control device 90. In addition, each impedance detection unit 60 outputs voltage fluctuations V1 to V3 to the control device 90.

[0192] The control device 90 inputs the calculation results (voltage fluctuations V1 to V3, impedances Z1 to Z3, and phase differences θ1 to θ3) (step S508). In addition, as the measurement frequency fs, the control device 90 determines whether all the frequencies within the measurement range have been scanned (step S509). If the determination result is affirmative, the control device 90 ends the impedance detection process. On the other hand, if the determination result in step S509 is negative, the control device 90 updates the measurement frequency fs in the same manner as step S107 of the first embodiment (step S510), and executes the process of step S502 again.

[0193] As described above, the battery monitoring device 50 of the fifth embodiment has the following effects.

[0194] Thereby, in the case where equalization processing is not required, while making the discharge amounts of the respective battery cells 42 the same, the impedance Zi and the phase difference θi can be detected. At this time, the sum of the voltage fluctuations Vi can be made below the threshold value, suppressing noise.

[0195] In addition, in the case where equalization processing is required, while making the amplitude specified value Isi of the alternating current output from the battery cell 42 that needs to be discharged larger than that of the other battery cells 42, the impedance Zi and the phase difference θi can be detected. At this time, the sum of the voltage fluctuations Vi can also be made below the threshold value, suppressing noise.

[0196] (Other Embodiments)

[0197] In addition, the present disclosure is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present disclosure. In addition, in the following respective embodiments, the same or equivalent parts are denoted by the same reference numerals, and the description of the parts with the same reference numerals is cited.

[0198] ·In the above embodiment, the battery monitoring device 50 causes the battery cell 42 to output an alternating current, but an alternating current may be applied to the battery cell 42 from another power source (such as an external power source).

[0199] ·In the above embodiment, the control device 90 updates the measurement frequency fs, but the measurement frequency fs may be set based on an instruction from an external device such as the ECU 100.

[0200] ·In the above embodiment, the amplitude specified value Isi and the phase specified value θsi are specified using the latest impedance Zi and phase difference θi, but it may not be the latest impedance Zi and phase difference θi. However, ideally, it is a value as close as possible to the latest impedance Zi and phase difference θi.

[0201] ·In the above-described embodiments, the threshold value of the total value of the voltage change is an arbitrary number and can be appropriately set according to the allowable value of the noise. For example, it can be zero.

[0202] ·In the above-described embodiments, the battery cells are described in a manner of up to three groups, but they can also be divided into four or more groups. For example, in the fifth embodiment, when Is1 becomes extremely large in order to further improve the equalization ability, in Figure 14 it may become "|V1| > |V2| + |V3|", making it impossible to configure cyclically, but by providing four or more groups, it becomes possible.

[0203] The control unit and its method described in the present disclosure can also be implemented by a dedicated computer provided by configuring a processor and a memory, and the above processor is programmed to execute one or more functions embodied by a computer program. Alternatively, the control unit and its method described in the present disclosure can be implemented by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit described in the present disclosure and the method of the control unit are implemented by one or more dedicated computers, which are composed of a combination of a processor programmed to execute one or more functions and a memory and a processor composed of one or more hardware logic circuits. In addition, the computer program can also be stored in a computer-readable non-transitory tangible storage medium as instructions to be executed by a computer.

[0204] Although the present disclosure has been described based on the embodiments, it should be understood that the present disclosure is not limited to the above-described embodiments and structures. The present disclosure also includes various modifications and modifications within the equivalent scope. In addition, various combinations, methods, and further including only one element, other combinations and methods of one or more or one or less also fall within the scope and the scope of ideas of the present disclosure.

Claims

1. A battery monitoring device (50) is applied to a battery pack (40) in which a plurality of battery cells (42) including an electrolyte and a plurality of electrodes are connected in series, and monitors the states of the respective battery cells, and is characterized in that, Comprising: A current generation unit (62) that causes an alternating current to flow through each of the battery cells; A voltage acquisition unit (62) that acquires the voltage variation (Vi) of each of the battery cells when the alternating current flows; An arithmetic unit (61) that calculates the impedance (Zi) of each of the battery cells and the phase difference (θi) between the alternating current and the voltage variation for each of the battery cells based on the alternating current flowing through each of the battery cells and the voltage variation acquired by the voltage acquisition unit; and A current control unit (90) that designates the amplitude (Isi) and phase (θsi) of the alternating current for each of the battery cells to the current generation unit, The current control unit determines at least one of the amplitude and phase of the alternating current flowing through each of the battery cells based on the impedance and phase difference of each of the battery cells calculated by the arithmetic unit, such that the total value (Vt) of the voltage variations of each of the battery cells is below a threshold value, and designates at least one of the determined amplitude and phase of the alternating current for each of the battery cells.

2. The battery monitoring device according to claim 1, characterized in that, The current control unit Determines the amplitude of the alternating current output from each of the battery cells based on the impedance of each of the battery cells calculated by the arithmetic unit, such that the magnitudes of the voltage variations of each of the battery cells are the same, and Determines the phase of the alternating current output from each of the battery cells based on the phase difference of each of the battery cells calculated by the arithmetic unit, such that the phase deviations of the voltage variations of each of the battery cells are equally spaced.

3. The battery monitoring device according to claim 1, characterized in that, The battery pack includes three or more of the battery cells, The battery monitoring device includes a state detection unit (90) that detects the state of charge of each of the battery cells, The current generation unit is configured to output an alternating current from each of the battery cells, The current control unit Determines the amplitude of the alternating current output for each of the battery cells based on the state of charge detected by the state detection unit, On the other hand, based on the determined amplitude of the alternating current, the impedance and phase difference of each of the battery cells calculated by the arithmetic unit, such that the total value of the voltage variations of each of the battery cells is below a threshold value, calculates the phase of the alternating current output for each of the battery cells and designates the calculated phase of the alternating current for each of the battery cells.

4. The battery monitoring device according to claim 1, characterized in that, The battery pack includes three or more of the battery cells, The current generation unit is configured to output an alternating current from each of the battery cells, The current control unit Determines the amplitude of the alternating current flowing through each of the battery cells to be the same, Based on the impedance and phase difference of each of the battery cells calculated by the arithmetic unit, such that the total value of the voltage variations of each of the battery cells is below a threshold value, calculates the phase of the alternating current output for each of the battery cells and designates the calculated phase of the alternating current for each of the battery cells.

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