Battery monitoring device

Abstract

To enable the internal state of a battery to be estimated without complicating a structure.SOLUTION: A battery pack 3C is composed of a plurality of battery cells Cb that are connected in series and supplies electric power to a load 4 that fluctuates in accordance with operation. A battery monitoring device 5 comprises: an information generation unit 13 for generating frequency information indicating a measurement frequency that corresponds to the fluctuating frequency of the load 4; a voltage measurement unit 14 for measuring an AC voltage value of the measurement frequency of the plurality of battery cells Cb; a current measurement unit 15 for using a resistor R1 connected in series to the battery pack 3 and measuring an AC current value of the measurement frequency of the plurality of battery cells Cb; and a processing unit 16. The processing unit 16 measures the AC impedance of the plurality of battery cells Cb by using the AC voltage value measured by the voltage measurement unit 14 as a measured voltage value and using the AC current value measured by the current measurement unit 15 as a measured current value, and executes temperature measurement processing for measuring the internal temperature of the plurality of battery cells Cb on the basis of the phase value of the measured AC impedance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a battery monitoring device used in a battery monitoring system that includes a plurality of battery monitoring devices that monitor each of a plurality of battery packs connected in series, and an electronic control device that communicates between the plurality of battery monitoring devices. [Background technology]

[0002] In recent years, the spread of battery-powered automobiles has led to an increased demand for battery monitoring systems to safely use secondary batteries. Battery monitoring systems are sometimes called Battery Management Systems, or BMS for short. Battery monitoring systems can estimate the internal state of a battery, such as the degree of battery deterioration and the internal temperature of the battery, and abnormalities in the battery state due to internal short circuits, by measuring the AC impedance of the battery.

[0003] Patent Document 1 discloses a battery monitoring device used in a battery monitoring system. The battery monitoring device disclosed in Patent Document 1 includes a current excitation unit that passes a current through the battery under measurement and a current measurement unit that measures the battery current, and includes voltage measurement units that measure the response voltage from the battery in the same number as the number of battery cells, and performs impedance measurement using the current and voltage values ​​obtained from the current and voltage measurement units. Hereinafter, the battery monitoring device disclosed in Patent Document 1 may be referred to as a conventional battery monitoring device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 003841 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional battery monitoring devices have problems such as the need for a current excitation unit, the need for a highly accurate shunt resistor for current measurement in order to improve the accuracy of estimating the internal state of the battery, and the need to improve the accuracy of time synchronization in the current measurement unit and voltage measurement unit. In particular, a synchronization circuit is required for time synchronization, which raises concerns about problems such as a complex configuration and increased costs.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to provide a battery monitoring device that can estimate the internal state of a battery without complicating the configuration. [Means for solving the problem]

[0007] The battery monitoring device described in claim 1 is a battery monitoring device used in a battery monitoring system (1) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 71, 81) that monitor a plurality of assembled batteries (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates between the plurality of battery monitoring devices. The assembled battery is configured with a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) connected in series, and supplies power to a load (4) that varies depending on the operation.

[0008] The battery monitoring device includes an information generating unit (13) that generates frequency information indicating a measurement frequency corresponding to a frequency of the load fluctuation, a voltage measuring unit (14, 14A, 14B, 14C, 14D) that measures an AC voltage value of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generating unit, a current measuring unit (15) that uses a measurement resistor (R1) connected in series to the assembled battery and measures an AC current value of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generating unit, and a processing unit (16, 53, 63, 73) that executes various processes to detect the state of the plurality of battery cells using the AC voltage value measured by the voltage measuring unit as a measured voltage value and the AC current value measured by the current measuring unit as a measured current value.

[0009] The processing unit executes a temperature measurement process that measures the AC impedance of the plurality of battery cells using the measured voltage value and the measured current value, and measures the internal temperature of the plurality of battery cells based on the phase value of the measured AC impedance. A battery monitoring device configured in this manner can measure the internal temperature of a battery cell without requiring a current excitation unit and a synchronous circuit as in conventional battery monitoring devices, and without requiring precise current measurement using a resistor because only the phase value of the AC impedance is used. Therefore, the above configuration makes it possible to estimate the internal state of a battery without complicating the configuration. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a battery monitoring system according to a first embodiment. [Diagram 2] FIG. 1 is a diagram showing a state of connection between battery cells and between battery packs according to a first embodiment; [Diagram 3] FIG. 1 is a diagram showing a schematic configuration of a battery monitoring device according to a first embodiment; [Figure 4] FIG. 1 is a diagram showing an example of a waveform of an orthogonal reference signal REFI according to the first embodiment; [Diagram 5]FIG. 1 is a diagram showing an example of a waveform of an orthogonal reference signal REFQ according to the first embodiment; [Figure 6] FIG. 1 is a diagram showing an example of the absolute value of the phase of AC impedance according to the first embodiment; [Figure 7] FIG. 1 is a diagram for explaining why the resistance value of a resistor for current measurement according to the first embodiment does not affect measurement of the phase value of AC impedance. [Figure 8] FIG. 1 is a diagram showing a first specific configuration example of a voltage measurement unit according to a first embodiment; [Figure 9] FIG. 11 is a diagram showing a second specific configuration example of the voltage measurement unit according to the first embodiment; [Figure 10] FIG. 11 is a diagram showing a third specific configuration example of the voltage measurement unit according to the first embodiment; [Figure 11] FIG. 1 is a schematic diagram showing a configuration of a battery monitoring device according to a comparative example; [Figure 12] FIG. 13 is a diagram showing an example of a time waveform of an output current of a current excitation unit according to a comparative example; [Figure 13] FIG. 13 is a diagram showing an example of a frequency spectrum of an output current of a current excitation unit according to a comparative example; [Figure 14] FIG. 13 is a diagram showing an example of a voltage frequency spectrum in an ideal state of a cell voltage according to a comparative example; [Figure 15] FIG. 13 is a diagram showing an example of a voltage frequency spectrum in an ideal state of the output of a voltage measuring unit according to a comparative example; [Figure 16] FIG. 11 is a diagram showing a schematic configuration of a battery monitoring device according to a second embodiment; [Figure 17] FIG. 11 is a diagram illustrating a configuration of a processing unit according to a second embodiment. [Figure 18] FIG. 13 is a diagram showing an example of a correction table according to the second embodiment; [Figure 19] FIG. 11 is a diagram for explaining an example of a first correction process according to the second embodiment; [Figure 20] FIG. 11 is a diagram showing a schematic configuration of a battery monitoring device according to a third embodiment; [Figure 21] FIG. 13 is a diagram showing a schematic configuration of a battery monitoring device according to a fourth embodiment; [Figure 22] FIG. 13 is a diagram showing an example of a thermal circuit network of a battery cell according to a fourth embodiment; [Diagram 23] FIG. 13 is a diagram illustrating a configuration of a battery monitoring device according to a fifth embodiment. [Figure 24] FIG. 1 is a schematic diagram showing a configuration of a battery monitoring system according to a modified example; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a number of embodiments will be described with reference to the drawings. Note that the same reference numerals are used to designate substantially the same components in the respective embodiments, and the description thereof will be omitted. (First embodiment) The first embodiment will be described below with reference to FIGS.

[0012] <Overall composition> As shown in FIG. 1, a battery monitoring system 1 of this embodiment is a system for monitoring a battery pack 2 mounted on a vehicle such as an automobile. The battery pack 2 is configured with a plurality of battery cells Cb connected in series between a pair of DC power lines L1, L2. Therefore, the same current flows through all of the plurality of battery cells Cb. In this embodiment, each battery cell Cb has the same battery specifications and is configured of a secondary battery such as a lithium ion battery. The "battery specifications" here refer to the type of battery, the battery capacity, the battery voltage value, etc. Therefore, the deterioration patterns of each battery cell Cb are similar.

[0013] In FIG. 1 and other drawings, only a portion of the battery cells Cb is shown. Each predetermined number of battery cells Cb are grouped together as one assembled battery 3. In other words, the assembled battery 3 is composed of some of the battery cells Cb. Specifically, each N number of battery cells Cb are grouped together as one assembled battery 3. Here, N is a positive integer of 2 or more. In other words, the assembled battery 3 is configured with N battery cells Cb connected in series. The battery pack 2 is composed of a plurality of assembled batteries 3 connected in series. However, in FIG. 1 and other drawings, only three assembled batteries 3 out of the plurality of assembled batteries 3 are shown, and alphabets are added to the end of the reference numerals to distinguish between the three assembled batteries 3.

[0014] The battery pack 3A is provided in the uppermost stage of the battery pack 2, i.e., on the side with the highest potential. The battery pack 3C is provided in the lowermost stage of the battery pack 2, i.e., on the side with the lowest potential. The battery pack 3B is provided between the battery pack 3A and the battery pack 3C. The components provided in the battery monitoring system 1 corresponding to each of these three battery packs 3A, 3B, and 3C may also be distinguished by adding the same alphabet to the end of the reference numeral. However, when it is not necessary to distinguish between these components, the alphabet at the end will be omitted and they will be referred to collectively.

[0015] A battery pack 2 consisting of a plurality of assembled batteries 3 supplies power to a load 4 via DC power lines L1 and L2. The load 4 is an inverter, a DC / DC converter, or the like mounted on the same vehicle as the battery pack 2. Therefore, the impedance of the load 4 varies according to the operation of the vehicle. As shown in FIG. 2, the battery cells Cb are electrically connected to each other and the two adjacent assembled batteries 3 are electrically connected to each other by bus bars BB1 and BB2, which are conductive members. In the above configuration, a common mode voltage is superimposed on the battery cells Cb. This common mode voltage is higher for battery cells Cb connected to the upper side of the battery pack 2, i.e., the higher potential side, and the maximum value of the common mode voltage is a relatively high voltage of, for example, about several hundred volts.

[0016] The battery monitoring system 1 includes a plurality of battery monitoring devices 5 that monitor the plurality of assembled batteries 3, respectively, and a battery monitoring ECU 6 that communicates with the plurality of battery monitoring devices 5. However, in FIG. 1 and other figures, only three of the plurality of battery monitoring devices 5 are shown: a battery monitoring device 5A that monitors the assembled battery 3A, a battery monitoring device 5B that monitors the assembled battery 3B, and a battery monitoring device 5C that monitors the assembled battery 3C. The battery monitoring device 5 includes a battery monitoring IC 7, which is an integrated circuit in which circuits that perform various operations for battery monitoring are integrated, and a plurality of external elements and circuits provided outside the battery monitoring IC 7. Note that IC is an abbreviation for Integrated Circuit.

[0017] The battery monitoring IC 7 executes various processes for monitoring the battery pack 3. The various processes executed by the battery monitoring IC 7 include a process for detecting the voltage of the battery cells Cb, a process for communicating with an external device, a temperature measurement process (to be described later), and a cell equalization process for equalizing the voltage of each battery cell Cb.

[0018] The battery monitoring ECU 6 is an electronic control device that controls the overall operation of the battery monitoring system 1, and includes an ECU IC8 configured as an IC, and a plurality of external elements and circuits provided outside the ECU IC8. The ECU IC8 executes various processes for overall control of the battery monitoring system 1. The ECU IC8 of the battery monitoring ECU 6 and each of the battery monitoring ICs 7 of the plurality of battery monitoring devices 5 are connected via a communication line 9.

[0019] The ECU IC8 of the battery monitoring ECU 6 communicates with each of the battery monitoring ICs 7 of the battery monitoring devices 5 according to a predetermined communication protocol. In this case, the connection between the battery monitoring ECU 6 and the battery monitoring devices 5 is a star connection. The ECU IC8 of the battery monitoring ECU 6 transmits data such as each command to the battery monitoring ICs 7 of the battery monitoring devices 5 via communication. The battery monitoring ICs 7 of the battery monitoring devices 5 transmit data such as each measurement result obtained by executing each process to the ECU IC8 of the battery monitoring ECU 6 via communication. In this case, a high common mode voltage superimposed on the battery cell Cb is applied to each battery monitoring device 5. Therefore, the battery monitoring ICs 7 of each battery monitoring device 5 and the ECU IC8 of the battery monitoring ECU 6 are insulated from each other by an insulating unit 10. The insulating unit 10 is provided in each of the battery monitoring devices 5 and the battery monitoring ECU 7, and the insulating method thereof may be, for example, an insulating transformer or a capacitance.

[0020] <Battery monitoring device configuration> The battery monitoring device 5 may be configured as shown in Fig. 3. In this case, the battery monitoring device 5C is used as an example to explain the configuration of the battery monitoring device 5, but the other battery monitoring devices 5 including the battery monitoring devices 5A and 5B may also employ a similar configuration.

[0021] In this case, the battery pack 3C is composed of four battery cells Cb, and alphabets are added to the end of the reference numerals to distinguish between the four battery cells Cb. The components provided in the battery monitoring device 5 corresponding to each of the four battery cells CbA, CbB, CbC, and CbD may also be distinguished by adding the same alphabets to the end of the reference numerals. However, when it is not necessary to distinguish between the components, the alphabets at the end will be omitted and they will be referred to collectively.

[0022] 3, the battery monitoring IC 7 of the battery monitoring device 5C includes a control unit 11 that controls the overall operation of the battery monitoring IC 7, a communication I / F 12 for communicating with an external device, an information generating unit 13, voltage measuring units 14A, 14B, 14C, and 14D, a current measuring unit 15, and a processing unit 16. Note that I / F is an abbreviation for interface. The information generating unit 13 generates frequency information that indicates a measurement frequency fLo that corresponds to the frequency of the fluctuation of the load 4.

[0023] The control unit 11 communicates with the battery monitoring ECU 6 via the communication I / F 12, thereby being able to acquire from the battery monitoring ECU 6 the operating frequency of the inverter or DC / DC converter which is the load 4, and in turn the frequency value of the fluctuation of the load 4. The control unit 11 can also acquire the frequency value of the fluctuation of the load 4 based on the measurement results by the voltage measurement units 14A-14D and the current measurement unit 15. The control unit 11 generates a frequency command which commands the value of the measurement frequency fLo based on the frequency value of the fluctuation of the load 4 acquired in this manner, and outputs the frequency command to the information generation unit 13. The information generation unit 13 generates frequency information based on the frequency command given by the control unit 11.

[0024] The frequency information may be various information according to the specific configuration of the voltage measurement unit 14, such as orthogonal reference signals REFI and REFQ, which are sine and cosine waves having the same frequency as the measurement frequency fLo, and data indicating the value of the measurement frequency fLo. Fig. 3 illustrates a case in which the frequency information is orthogonal reference signals REFI and REFQ. Specifically, the orthogonal reference signals REFI and REFQ are signals having waveforms as shown in Figs. 4 and 5.

[0025] The voltage measurement unit 14A is provided corresponding to the battery cell CbA and measures the voltage value of the battery cell CbA. The voltage measurement unit 14A receives the voltage VASP of the high potential terminal of the battery cell CbA, the voltage VASN of the low potential terminal of the battery cell CbA, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VASP and VASN and the frequency information, the voltage measurement unit 14A measures the voltage change of the battery cell CbA caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbA.

[0026] The voltage measurement unit 14B is provided corresponding to the battery cell CbB and measures the voltage value of the battery cell CbB. The voltage measurement unit 14B receives the voltage VBSP of the high potential terminal of the battery cell CbB, the voltage VBSN of the low potential terminal of the battery cell CbB, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VBSP and VBSN and the frequency information, the voltage measurement unit 14B measures the voltage change of the battery cell CbB caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbB.

[0027] The voltage measurement unit 14C is provided corresponding to the battery cell CbC and measures the voltage value of the battery cell CbC. The voltage measurement unit 14C receives the voltage VCSP of the high potential terminal of the battery cell CbC, the voltage VCSN of the low potential terminal of the battery cell CbC, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VCSP and VCSN and the frequency information, the voltage measurement unit 14C measures the voltage change of the battery cell CbC caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbC.

[0028] The voltage measurement unit 14D is provided corresponding to the battery cell CbD and measures the voltage value of the battery cell CbD. The voltage measurement unit 14D receives the voltage VDSP of the high potential terminal of the battery cell CbD, the voltage VDSN of the low potential terminal of the battery cell CbD, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages VDSP and VDSN and the frequency information, the voltage measurement unit 14D measures the voltage change of the battery cell CbD caused by the fluctuation of the load 4, that is, the AC voltage value of the measurement frequency fLo of the battery cell CbD.

[0029] The voltage measuring units 14A to 14D output measurement result information representing the measurement results of the AC voltage values ​​to the processing unit 16. The measurement result information is various information according to the specific configuration of the voltage measuring unit 14, such as signals representing the in-phase and quadrature components of the AC voltage having the same frequency as the orthogonal reference signals REFI and REFQ, and a signal representing the AC voltage amplitude component of the measurement frequency fLo. Fig. 3 illustrates an example in which the measurement result information is signals VABI, VBBI, VCBI, and VDBI representing the in-phase components of the AC voltage, and signals VABQ, VBBQ, VCBQ, and VDBQ representing the quadrature components.

[0030] The current measurement unit 15 measures the current values ​​of the multiple battery cells CbA to CbD using a resistance R1, which is a measurement resistance connected in series to the battery pack 3C. In this embodiment, the resistance R1 is the resistance of the bus bar BB2, which electrically connects the battery packs 3 together as described above. Note that the bus bar BB1 can be used as the resistance R1, or a resistance with higher accuracy than the bus bars BB1 and BB2, such as a shunt resistor separately provided for current detection, can also be used.

[0031] The current measurement unit 15 receives the voltage I1SP at the high potential terminal of the resistor R1, the voltage I1SN at the low potential terminal of the resistor R2, and the orthogonal reference signals REFI and REFQ, which are frequency information generated by the information generation unit 13. Based on the voltages I1SP and I1SN and the frequency information, the current measurement unit 15 measures the current changes in the multiple battery cells CbA-CbD caused by fluctuations in the load 4, that is, the AC current values ​​of the multiple battery cells CbA-CbD at the measurement frequency fLo.

[0032] The processing unit 16 executes various processes for detecting the states of the plurality of battery cells CbA-CbD by using the AC voltage values ​​measured by the voltage measuring units 14A-14D as measured voltage values ​​and the AC current values ​​measured by the current measuring unit 15 as measured current values. In this case, the processing unit 16 can execute a temperature measurement process for measuring the internal temperatures of the plurality of battery cells CbA-CbD.

[0033] The temperature measurement process includes a process of measuring the AC impedance of the battery cells CbA-CbD using a plurality of measured voltage values ​​and measured current values ​​corresponding to each of the battery cells CbA-CbD, and a process of measuring the internal temperature of the battery cells CbA-CbD based on the phase value of the measured AC impedance. The phase value of the AC impedance used in the temperature measurement process can be the absolute value of the phase of the AC impedance, which is the absolute phase value from the origin as shown in Fig. 6. Note that Im in Fig. 6 and the like represents the imaginary part, and Re represents the real part.

[0034] The temperature measurement process of this embodiment is performed based on the following concept. That is, the processing unit 16 calculates a complex impedance value by processing the measured current value and the measured voltage value. The resistor R1 used by the current measuring unit 15 for current measurement is the resistor of the busbar BB2 as described above. Therefore, it is assumed that the true value of the resistance value of the resistor R1 may not be clear due to temperature fluctuations, etc.

[0035] However, as described in the reference paper "R. Schwarz, et. al., "Sensorless battery cell temperature estimation circuit for enhanced safety in battery systems", IECON 2015, Yokohama, Japan, 2015, pp. 001536-001541", it is known that the phase of the complex impedance value does not depend on the resistance value. Therefore, the processing unit 16 can detect the internal temperatures of the multiple battery cells CbA to CbD based on the relationship between the phase value of the AC impedance measured in advance and the internal temperature of the battery cell Cb.

[0036] 7, the reason why the resistance value of resistor R1 does not affect the measurement of the phase value of AC impedance by processing unit 16 will be described below. The AC voltage value measured by voltage measuring unit 14 is expressed by equation (1), where the amplitude of the AC voltage value is V and the phase of the AC voltage value is θV. If it is assumed that the resistance value of resistor R1 deviates by ΔR from an assumed value R, which is an assumed value, the AC current value measured by current measuring unit 15 is expressed by equation (2), where the amplitude of the AC current value is I and the phase of the AC current value is θI.

[0037] The AC impedance value calculated based on these AC voltage value and AC current value is expressed by formula (3). As is clear from formula (3), the amplitude of the AC impedance value depends on the deviation ΔR of the resistance value of resistor R1 and thus a deviation occurs, but the phase of the AC impedance value does not depend on the deviation ΔR of the resistance value of resistor R1 and therefore no deviation occurs. Therefore, when the processing unit 16 uses only the phase value of the AC impedance, that is, when performing the temperature measurement process of this embodiment, there is no need to use a highly accurate resistor as resistor R1, and it is possible to use the resistance of busbar BB2, which has a relatively low accuracy, as resistor R1.

[0038] <Specific Configuration of Voltage Measurement Unit 14> As specific configurations of voltage measurement unit 14 and current measurement unit 15, for example, a first configuration example employing a frequency lock-in method as shown in Fig. 8, a second configuration example employing an FFT method as shown in Fig. 9, or a third configuration example employing a bandpass filter method as shown in Fig. 10 can be adopted. In this case, specific configuration examples of voltage measurement unit 14 and current measurement unit 15 will be described using voltage measurement unit 14A as an example, but the other voltage measurement units 14 or current measurement units 15 including voltage measurement units 14B to 14D can also adopt similar configurations.

[0039] [1] First configuration example As shown in Fig. 8, the voltage measurement unit 14A in the first configuration example includes subtractors 21, 22, 23, an A / D converter 24, a DC offset correction unit 25, a first filter 26, and a quadrature demodulator 27. In this specification, the A / D converter may be abbreviated as ADC. The subtractor 21 subtracts a signal corresponding to an offset value generated by the DC offset correction unit 25 from the voltage VASP. The subtractor 22 subtracts a signal corresponding to an offset value generated by the DC offset correction unit 25 from the voltage VASN. The ADC 24 inputs the output signals of the subtractors 21 and 22, and outputs a digital signal representing the result of A / D conversion of the input signals.

[0040] DC offset correction unit 25 receives the output signal of ADC 24, generates a signal corresponding to an offset value according to the input signal, and outputs the signal to each of subtractors 21 to 23. Subtractor 23 subtracts the signal corresponding to the offset value generated by DC offset correction unit 25 from the output signal of ADC 24. First filter 26 receives the output signal of subtractor 23, performs a predetermined filtering process, and outputs the filtered signal to quadrature demodulator 27.

[0041] The quadrature demodulator 27 includes mixers 28 and 29, and second filters 30 and 31. The output signal of the first filter 26 and the orthogonal reference signal REFI are input to the mixer 28. The output signal of the mixer 28, that is, the signal obtained by multiplying the output signal of the first filter 26 and the orthogonal reference signal REFI, is input to the second filter 30. The output signal of the first filter 26 and the orthogonal reference signal REFQ are input to the mixer 29. The output signal of the mixer 29, that is, the signal obtained by multiplying the output signal of the first filter 26 and the orthogonal reference signal REFQ, is input to the second filter 31.

[0042] The second filter 30 performs a predetermined filtering process on the input signal and outputs the filtered signal as a signal VABI. The second filter 31 performs a predetermined filtering process on the input signal and outputs the filtered signal as a signal VABQ. According to the voltage measurement unit 14A of the first configuration example, the signal VABI representing the in-phase component of the AC voltage and the signal VABQ representing the quadrature component, which have the same frequency as the quadrature reference signals REFI and REFQ, can be output as measurement result information. When the first configuration example is adopted as the voltage measurement unit 14, the processing unit 16 can use the in-phase component, quadrature component, voltage amplitude, voltage phase, etc. of the AC voltage based on the output signal of the voltage measurement unit 14 in the temperature measurement process.

[0043] [2] Second configuration example 9, the voltage measurement unit 14A in the second configuration example is different from the voltage measurement unit 14A in the first configuration example in that it includes an FFT unit 32 instead of the orthogonal demodulator 27. FFT is an abbreviation for Fast Fourier Transform. The output signal of the first filter 26 and the orthogonal reference signal REFI are input to the FFT unit 32.

[0044] The FFT unit 32 performs discrete Fourier transform processing on the output signal of the first filter 26, and can output a signal VABI representing the in-phase component of the frequency bin specified by the orthogonal reference signal REFI and a signal VABQ representing the orthogonal component as measurement result information. When the second configuration example is adopted as the voltage measurement unit 14, the processing unit 16 can use the in-phase component, orthogonal component, voltage amplitude, voltage phase, etc. of the AC voltage based on the output signal of the voltage measurement unit 14 in the temperature measurement process.

[0045] [3] Third configuration example 10, the voltage measurement unit 14A in the third configuration example is different from the voltage measurement unit 14A in the first configuration example in that it includes a band pass filter 33, a rectifier circuit 34, and a smoothing circuit 35 instead of the first filter 26 and the quadrature demodulator 27. In this specification, the band pass filter may be referred to as a BPF. The output signal of the subtractor 23 is input to the BPF 33.

[0046] The BPF 33 passes only a specific frequency component of the input signal. The BPF 33 is configured to be able to set the specific frequency to be passed based on data representing the value of the measurement frequency fLo, which is frequency information provided by the information generating unit 13. The rectifier circuit 34 receives the output signal of the BPF 33, rectifies the signal, and outputs the signal. The smoothing circuit 35 receives the output signal of the rectifier circuit 34, smoothes the signal, and outputs the signal. The output signal of the smoothing circuit 35 is a signal corresponding to the amplitude component of the AC voltage. Therefore, in this case, the output signal of the smoothing circuit 35 becomes the signal V representing the measurement result information.

[0047] According to the present embodiment described above, the following effects can be obtained. The battery monitoring device 5 of this embodiment includes an information generating unit 13 that generates frequency information representing a measurement frequency fLo corresponding to the frequency of fluctuation of the load 4, a voltage measuring unit 14 that measures the AC voltage values ​​of the measurement frequency of the multiple battery cells Cb based on the frequency information generated by the information generating unit 13, a current measuring unit 15 that uses a resistor R1 connected in series to the assembled battery 3 and measures the AC current values ​​of the multiple battery cells Cb based on the frequency information generated by the information generating unit 13, and a processing unit 16 that executes various processes to detect the state of the multiple battery cells Cb by using the AC voltage value measured by the voltage measuring unit 14 as the measured voltage value and the AC current value measured by the current measuring unit 15 as the measured current value.

[0048] The processing unit 16 executes a temperature measurement process that measures the AC impedance of the multiple battery cells Cb using the measured voltage value and the measured current value, and measures the internal temperature of the multiple battery cells Cb based on the phase value of the measured AC impedance. The battery monitoring device 5 configured in this way can measure the internal temperature of the battery cells Cb without requiring a current excitation unit and a synchronous circuit as in conventional battery monitoring devices, and without requiring precise current measurement by resistance because only the phase value of the AC impedance is used. Therefore, according to this embodiment, it is possible to estimate the internal state of the battery without complicating the configuration.

[0049] The effects obtained by this embodiment become clearer when compared with a conventional battery monitoring device. Therefore, a comparative example equivalent to the conventional battery monitoring device will be described and then the comparative example will be compared with this embodiment. As shown in Fig. 11, a battery monitoring device 41 of the comparative example differs from the battery monitoring device 5C of this embodiment shown in Fig. 3 in that it includes a battery monitoring IC 42 instead of the battery monitoring IC 7 and that a current generating unit 43 is added.

[0050] The battery monitoring IC 42 is configured to be able to measure battery impedance based on an AC impedance method. The battery monitoring IC 42 differs from the battery monitoring IC 7 in that an excitation signal processing unit 44 is added, that a current measuring unit 45 is provided instead of the current measuring unit 15, and that a measuring unit 46 is provided instead of the processing unit 16. In this case, the excitation signal processing unit 44 constitutes a current excitation unit 47 together with a current generating unit 43 provided outside the battery monitoring IC 42.

[0051] The excitation signal processing unit 44 receives the orthogonal reference signal REFI generated by the information generating unit 13. The excitation signal processing unit 44 performs signal processing such as amplification, level conversion, and application of a DC offset signal on the input signal and outputs the result. The current generating unit 43 receives the output signal of the excitation signal processing unit 44 and generates an excitation current to be applied to the battery cells CbA to CbD based on the signal. At this time, the voltage of the high potential side terminal of the battery cell CbD becomes the voltage V1FP, and the voltage of the low potential side terminal of the battery cell CbA becomes the voltage V1FN.

[0052] In this case, the specific configuration of the voltage measurement unit 14 is assumed to be the same as that of the first configuration example shown in Fig. 8. The voltage measurement units 14A to 14D output signals VABI, VBBI, VCBI, and VDBI representing the in-phase components of the AC voltage and signals VABQ, VBBQ, VCBQ, and VDBQ representing the quadrature components to the measurement unit 46. In the following description, the signals VABI, VBBI, VCBI, and VDBI may be collectively referred to as signal VxBI, and the signals VABQ, VBBQ, VCBQ, and VDBQ may be collectively referred to as signal VxBQ.

[0053] The current measurement unit 45 receives signals I1FN and I1FP for measuring the current generated by the current generation unit 43 and orthogonal reference signals REFI and REFQ generated by the information generation unit 13. In this case, the current generation unit 43 is configured to include a shunt resistor with higher accuracy than the resistor of the bus bar BB2, and to output signals I1FN and I1FP according to the terminal voltages of the shunt resistor. The current measurement unit 45 has a configuration similar to that of the voltage measurement unit 14. The current measurement unit 45 outputs a signal I1BI representing an in-phase component of the AC current and a signal I1BQ representing an orthogonal component to the measurement unit 46. The measurement unit 46 performs various processes for measuring the impedance of the battery cell Cb based on the output signal of the voltage measurement unit 14 and the output signal of the current measurement unit 45.

[0054] In the above configuration, when the information generating unit 13 generates the orthogonal reference signals REFI and REFQ during impedance measurement, an excitation current to be applied to the battery cells CbA to CbD is generated by the operation of the current exciting unit 47. The excitation current generated by the current exciting unit 47 includes a DC offset signal as shown in Fig. 12, and also includes an excitation AC current signal of the measurement frequency fLo as shown in Fig. 13.

[0055] The excitation current is applied to the battery pack 3 and is converted into a voltage by the impedance of the battery cells CbA to CbD. Therefore, the frequency spectrum of the voltage generated across each of the battery cells CbA to CbD generates a DC component and a signal at the measurement frequency fLo, as shown in Fig. 14, where the DC component is the sum of the voltage of the battery cell Cb and the product of the impedance of the battery cell Cb and the DC offset signal of the excitation current, and an excitation AC voltage is generated at the measurement frequency fLo, which is the product of the impedance of the battery cell Cb and the excitation AC current.

[0056] Such excitation voltages are input to voltage measurement units 14A-14D connected to the respective battery cells CbA-CbD, where they are synchronously detected by the orthogonal reference signals REFI and REFQ in the voltage measurement units 14A-14D, and then filtered to detect only the excitation AC voltage, which is the same frequency component as the measurement frequency fLo. The voltage measurement unit 14 supplies to the measurement unit 46 a signal VxBQ representing an in-phase component based on the amplitude and phase of the excitation voltage as shown in FIG. 15 and a signal VxBQ representing a quadrature component.

[0057] The excitation current is input to a current measuring unit 45, where it is synchronously detected by orthogonal reference signals REFI and REFQ, and then filtered to detect only the excitation AC current, which is the same frequency component as the measurement frequency fLo. The current measuring unit 45 supplies a signal I1BI representing an in-phase component and I1BQ representing a quadrature component based on the amplitude and phase of the generated excitation current to a measurement unit 46.

[0058] The measurement unit 46 calculates the real and imaginary parts of the impedance by vector dividing the excitation voltage thus input by the excitation current. The measurement unit 46 reports the calculation results to a higher-level system (not shown) via the control unit 11 and the communication I / F 12. According to the battery impedance measurement using the AC impedance method with the configuration of the comparative example, signal detection is performed only for frequency components equal to the measurement frequency fLo, so that the noise removal capability is high and measurements with a good SNR (signal-to-noise ratio) are possible.

[0059] However, the battery monitoring device 41 of the comparative example requires the current excitation unit 47 and a highly accurate shunt resistor as a resistor for current measurement by the current measurement unit 15, which causes problems of a more complex configuration and increased manufacturing costs. In addition, in the battery monitoring device 41 of the comparative example, when the current measurement unit 45 and the voltage measurement unit 14 perform measurements using different reference clocks, it is necessary to improve the accuracy of time synchronization in the current measurement unit 15 and the voltage measurement unit 14 in order to improve the accuracy of the impedance measurement and, by extension, the accuracy of the estimation of the internal state of the battery.

[0060] Therefore, the battery monitoring device 41 of the comparative example requires a synchronous circuit, which causes problems of further complicating the configuration and increasing manufacturing costs. In contrast, the battery monitoring device 5 of the present embodiment does not require the current excitation unit 47 and highly accurate shunt resistors as in the battery monitoring device 41 of the comparative example, and does not require a synchronous circuit. Therefore, according to the present embodiment, it is possible to estimate the internal state of the battery while having a simpler configuration than the comparative example and keeping manufacturing costs low.

[0061] Second embodiment The second embodiment will be described below with reference to FIGS. 16, a battery monitoring IC 52 included in a battery monitoring device 51 of this embodiment differs from the battery monitoring IC 7 of the first embodiment in that it includes a processing unit 53 instead of the processing unit 16. In this case, a temperature sensor 54 is provided for detecting the temperature of the battery pack 3, and a temperature detection signal Sa indicating the temperature detected by the temperature sensor 54 is input to the processing unit 53. The temperature sensor 54 is provided so as to be able to detect the temperature of an arbitrary location of the battery pack 2.

[0062] 17, the processing unit 53 includes a measurement unit 55, correction tables 56A, 56B, 56C, and 56D, correction processing units 57A, 57B, 57C, and 57D, and a temperature processing unit 58. The measurement unit 55 executes a part of the temperature measurement process executed by the processing unit 16 in the first embodiment, that is, a process of measuring a plurality of AC impedances using measured voltage values ​​and measured current values.

[0063] The measured voltage of each battery cell Cb may vary depending on the temperature and wiring of the battery pack 2. In this embodiment, the deviation of the voltage value and therefore the AC impedance value due to these factors is corrected using a correction table 56. As shown in FIG. 18, the correction table 56 stores correction values ​​corresponding to temperatures and frequencies. The AC impedance value and the temperature detection signal Sa of the corresponding battery cell Cb are input to the correction processing unit 57. The correction processing unit 57 is also configured to be able to acquire the value of the current measurement frequency fLo.

[0064] With this configuration, the correction processing unit 57 executes a first correction process to correct the AC impedance value measured by the measurement unit 55 using the correction value stored in the correction table 56. As a method of such correction, a method of vector calculation of a correction term for a complex impedance value, as shown in Fig. 19, can be mentioned. For example, when the temperature is 0°C and the measurement frequency fLo is 10 Hz, the AC impedance value before correction is the impedance value Z expressed by the formula (4), and the AC voltage value after correction is the impedance value Z' expressed by the formula (5). The temperature processing unit 58 executes a process of measuring the internal temperatures of the multiple battery cells Cb based on the value of the phase of the AC impedance after correction by the first correction process.

[0065] According to the present embodiment described above, it is possible to correct the deviation in the measured voltage for each battery cell Cb caused by the temperature, wiring, etc. of the battery pack 2. Therefore, according to the present embodiment, it is possible to accurately measure the internal temperature of the battery cell Cb without being affected by the temperature, wiring, etc. of the battery pack 2.

[0066] Third embodiment The third embodiment will be described below with reference to FIG. 20, a battery monitoring IC 62 included in a battery monitoring device 61 of this embodiment is different from the battery monitoring IC 7 of the first embodiment in that it has a processing unit 63 instead of the processing unit 16. In this case, as in the second embodiment, a temperature sensor 54 is provided to detect the temperature of the battery pack 3, and a temperature detection signal Sa indicating the temperature detected by the temperature sensor 54 is input to the processing unit 63.

[0067] The processing unit 63 executes a temperature measurement process similar to that of the processing unit 16 of the first embodiment. The processing unit 63 executes a second correction process to correct the internal temperature measured by the temperature measurement process using a temperature detection value detected by the temperature sensor 54. The processing unit 63 executes the second correction process in a temperature equilibrium state in which the temperature of the battery pack 3 is in an equilibrium state. In this case, a relationship between the temperature detection value detected by the temperature sensor 54 in the temperature equilibrium state and the measured voltage value estimated by the processing unit 63, etc., is obtained in advance, and the second correction process is executed based on the relationship.

[0068] In the above configuration, it can be determined that the temperature is in equilibrium if one or both of the following (a) and (b) are met: (a) A state in which the vehicle in which the battery monitoring device 61 and the battery pack 3 are mounted is stopped (b) After a certain period of time has elapsed during which the current flowing through the multiple battery cells Cb remains constant

[0069] For this reason, the processing unit 63 may execute the second correction process when the vehicle is stopped, or may execute the second correction process after a predetermined time has elapsed during which the current flowing through the multiple battery cells Cb has become constant.

[0070] As described above, according to this embodiment, the internal temperature measured by the temperature measurement process is corrected using the temperature detection value detected by the temperature sensor 54 that detects the temperature of the battery pack 3, so that the internal temperatures of the multiple battery cells Cb can be measured with even greater accuracy.

[0071] (Fourth embodiment) The fourth embodiment will be described below with reference to FIGS. 21 , a battery monitoring IC 72 provided in a battery monitoring device 71 of the present embodiment differs from the battery monitoring IC 62 of the third embodiment in that a processing unit 73 is provided instead of the processing unit 63. In this case, in addition to the temperature sensor 54 that detects the temperature of the battery pack 3 similar to the third embodiment, a temperature sensor 74 that detects the outside air temperature is provided.

[0072] The processing unit 73 executes the same temperature measurement process and second correction process as the processing unit 63 of the third embodiment. However, in the second correction process, the processing unit 73 corrects the internal temperature measured by the temperature measurement process using the temperature detection value and the thermal circuit network of the battery pack 3 including the temperature sensors 54, 74. The reason for performing such a correction is that a difference occurs between the temperature detection value by the temperature sensor 54 provided in the battery pack 2 and the actual temperature value inside the battery pack 2.

[0073] Specifically, in this embodiment, multiple temperature sensors 54, 74 are provided to detect the temperature of the battery pack 3 and the outside air temperature, and a thermal circuit of the battery pack 3 including these temperature sensors 54, 74 is measured and modeled in advance. The thermal circuit network of the battery pack 3, and therefore the battery cells Cb, may be as shown in Fig. 22, for example. The processing unit 73 calculates the amount of heat generated Q from the current value measured by the current measurement unit 15, and estimates the internal temperature of the battery pack 3, and therefore the battery cells Cb, based on the detected temperature value of the outside air temperature and the temperature of the battery pack 3, specifically the detected temperature value of the temperature outside the battery cells Cb, detected by the temperature sensors 54, 74.

[0074] As described above, according to this embodiment, in the second correction process, the internal temperature measured by the temperature measurement process is corrected using the temperature detection value and the thermal circuit network of the battery pack 3 including the temperature sensors 54, 74. This suppresses the estimation error of the internal temperature caused by the difference between the temperature detection value and the actual temperature value, and as a result, the internal temperatures of the multiple battery cells Cb can be measured with even greater accuracy.

[0075] Fifth embodiment The fifth embodiment will be described below with reference to FIG. As shown in Fig. 23, the battery monitoring device 81 of this embodiment differs from the battery monitoring device 5 of the first embodiment in that it includes a battery monitoring IC 82 instead of the battery monitoring IC 7, and in that it also includes a current excitation unit 47 similar to the battery monitoring device 41 of the comparative example shown in Fig. 11. The battery monitoring IC 82 differs from the battery monitoring IC 7 in that it also includes an excitation signal processing unit 44 constituting the current excitation unit 47, and in that it also includes a processing unit 83 instead of the processing unit 16. The current excitation unit 47 can generate an AC current having the same frequency as the measurement frequency fLo based on the orthogonal reference signal REFI, which is frequency information generated by the information generating unit 13, and apply the AC current to the battery pack 3.

[0076] In this case, the voltage measurement unit 14 can measure the AC voltage values ​​of the multiple battery cells Cb at the measurement frequency fLo during the period when the AC current generated by the current excitation unit 47 is applied to the assembled battery 3. Also, in this case, the current measurement unit 15 can measure the AC current values ​​of the multiple battery cells Cb at the measurement frequency fLo during the period when the AC current generated by the current excitation unit 47 is applied to the assembled battery 3. In this case, the processing unit 83 uses the AC voltage values ​​measured by the voltage measurement unit 14 during the period when the AC current generated by the current excitation unit 47 is applied to the assembled battery 3 as the measured values ​​and the AC current values ​​measured by the current measurement unit 15 as the measured current values, to perform a temperature measurement process similar to that performed by the processing unit 16 in the first embodiment.

[0077] According to the present embodiment described above, it is possible to estimate the state inside the battery without complicating the configuration, as in the first embodiment. In this case, a current excitation unit 47 is added to the configuration of the first embodiment, but since the amplitude value of the AC impedance is not used in the temperature measurement process, and only the phase value is used, there is no need to perform high-precision current measurement. Therefore, it is possible to simplify the configuration and reduce the manufacturing cost compared to the comparative example.

[0078] (Other embodiments) The present invention is not limited to the embodiments described above and shown in the drawings, and can be modified, combined, or expanded as desired without departing from the spirit and scope of the present invention. The numerical values ​​and the like shown in the above embodiments are merely examples and are not intended to be limiting. The connection between the battery monitoring ECU 6 and the multiple battery monitoring devices 5 does not have to be limited to a star-type connection, and the connection between the battery monitoring ECU 6 and the multiple battery monitoring devices 5 can also be a daisy-chain type connection, for example, as in a modified battery monitoring system 91 shown in Figure 24.

[0079] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

[0080] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer.

[0081] In addition to the inventions described in the claims, the present disclosure includes the following inventions. [1] A battery monitoring device used in a battery monitoring system (1, 91) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 71, 81) that monitors a plurality of battery packs (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates with the plurality of battery monitoring devices, The battery pack is configured by connecting a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) in series and supplies power to a load (4) whose power varies depending on the operation of the load (4). an information generating unit (13) that generates frequency information representing a measurement frequency corresponding to a frequency of the load fluctuation; a voltage measurement unit (14, 14A, 14B, 14C, 14D) that measures AC voltage values ​​of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a current measurement unit (15) that uses a measurement resistor (R1) connected in series to the battery pack and measures an AC current value of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a processing unit (16, 53, 63, 73) that executes various processes for detecting states of the plurality of battery cells by using the AC voltage value measured by the voltage measurement unit as a measured voltage value and the AC current value measured by the current measurement unit as a measured current value; Equipped with The processing unit includes: A battery monitoring device that performs a temperature measurement process to measure the AC impedance of the multiple battery cells using the measured voltage values ​​and the measured current values, and to measure the internal temperature of the multiple battery cells based on the phase value of the measured AC impedance. [2] The assembled batteries are electrically connected to each other by a conductive member (BB2), The battery monitoring device according to [1], wherein the measuring resistor is the conductive member. [3] The processing section (53) A first correction process is performed to correct the measured AC impedance value using a correction table (56A, 56B, 56C, 56D) in which correction values ​​corresponding to temperatures and frequencies are stored; The battery monitoring device according to any one of claims 1 to 2, further comprising: a first correction process for correcting a phase of the AC impedance of the battery cells; [4] The battery monitoring device according to any one of [1] to [3], wherein the processing unit (63, 73) executes a second correction process to correct the internal temperature measured by the temperature measurement process using a temperature detection value detected by a temperature sensor (54) that detects the temperature of the battery pack. [5] The battery monitoring device according to [4], wherein the processing unit (63) executes the second correction process in a temperature equilibrium state in which the temperature of the battery pack is in equilibrium. [6] The battery pack is mounted on a vehicle, The battery monitoring device according to any one of claims 4 to 5, wherein the processing unit (63) executes the second correction process when the vehicle is stopped. [7] The battery monitoring device according to any one of [4] to [6], wherein the processing unit (63) executes the second correction process after a predetermined time has elapsed since the current flowing through the plurality of battery cells became constant. [8] The battery monitoring device according to any one of [4] to [7], wherein, in the second correction process, the processing unit (73) corrects the internal temperature measured by the temperature measurement process using the temperature detection value and a thermal circuit network of the battery pack including the temperature sensor. [9] a current excitation unit (47) that generates an AC current having the same frequency as the measurement frequency based on the frequency information generated by the information generation unit and applies the AC current to the battery pack, the voltage measurement unit measures AC voltage values ​​of the plurality of battery cells at the measurement frequency during a period in which the AC current generated by the current excitation unit is applied to the battery pack; The battery monitoring device described in any one of [1] to [8], wherein the current measurement unit measures the AC current value of the measurement frequency of the multiple battery cells during a period in which the AC current generated by the current excitation unit is applied to the battery pack. [Explanation of symbols]

[0082] 1, 91...battery monitoring system, 3, 3A, 3B, 3C...battery pack, 4...load, 5, 5A, 5B, 5C, 51, 61, 71, 81...battery monitoring device, 6...battery monitoring ECU, 13...information generation unit, 14, 14A, 14B, 14C, 14D...voltage measurement unit, 15...current measurement unit, 16, 53, 63, 73...processing unit, 47...current excitation unit, 54...temperature sensor, 56, 56A, 56B, 56C, 56D...correction table, BB1, BB2...busbar, Cb, CbA, CbB, CbC, CbD...battery cell, R1...resistor.

Claims

1. A battery monitoring device used in a battery monitoring system (1) including a plurality of battery monitoring devices (5, 5A, 5B, 5C, 51, 61, 71, 81) that monitors a plurality of battery packs (3, 3A, 3B, 3C) connected in series, and an electronic control device (6) that communicates with the plurality of battery monitoring devices, The battery pack has a configuration in which a plurality of battery cells (Cb, CbA, CbB, CbC, CbD) are connected in series, and supplies power to a load (4) whose power varies depending on the operation of the load (4). An information generating unit (13) that generates frequency information representing a measurement frequency corresponding to a frequency of the load fluctuation; a voltage measurement unit (14, 14A, 14B, 14C, 14D) for measuring AC voltage values ​​of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a current measurement unit (15) that uses a measurement resistor (R1) connected in series to the battery pack and measures an AC current value of the plurality of battery cells at the measurement frequency based on the frequency information generated by the information generation unit; a processing unit (16, 53, 63, 73) that executes various processes for detecting states of the plurality of battery cells by using the AC voltage value measured by the voltage measurement unit as a measured voltage value and the AC current value measured by the current measurement unit as a measured current value; Equipped with The processing unit includes: A battery monitoring device that performs a temperature measurement process to measure the AC impedance of the multiple battery cells using the measured voltage values ​​and the measured current values, and to measure the internal temperature of the multiple battery cells based on the phase value of the measured AC impedance.

2. The battery packs and the battery cells are electrically connected to each other by conductive members (BB1, BB2), 2. The battery monitoring device according to claim 1, wherein the measuring resistor is the conductive member.

3. The processing section (53) performing a first correction process for correcting the measured AC impedance value using a correction table (56A, 56B, 56C, 56D) in which correction values ​​corresponding to temperatures and frequencies are stored; 3. The battery monitoring device according to claim 1, wherein the internal temperatures of the plurality of battery cells are measured based on a value of the phase of the AC impedance after the correction by the first correction process.

4. The battery monitoring device according to claim 1 or 2, wherein the processing unit (63, 73) executes a second correction process to correct the internal temperature measured by the temperature measurement process using a temperature detection value detected by a temperature sensor (54) that detects the temperature of the battery pack.

5. The battery monitoring device according to claim 4 , wherein the processing unit (63) executes the second correction process in a temperature equilibrium state in which the temperature of the battery pack is in equilibrium.

6. The battery pack is mounted on a vehicle, The battery monitoring device according to claim 4 , wherein the processing unit (63) executes the second correction process when the vehicle is stopped.

7. The battery monitoring device according to claim 4 , wherein the processing unit (63) executes the second correction process after a predetermined time has elapsed since the current flowing through the plurality of battery cells became constant.

8. The battery monitoring device according to claim 4, wherein the processing unit (73) corrects the internal temperature measured by the temperature measurement process in the second correction process using the temperature detection value and a thermal circuit network of the battery pack including the temperature sensor.

9. a current excitation unit (47) that generates an AC current having the same frequency as the measurement frequency based on the frequency information generated by the information generation unit and applies the AC current to the battery pack; the voltage measurement unit measures AC voltage values ​​of the plurality of battery cells at the measurement frequency during a period in which the AC current generated by the current excitation unit is applied to the battery pack; The battery monitoring device according to claim 1 , wherein the current measurement unit measures an AC current value at the measurement frequency of the plurality of battery cells during a period in which the AC current generated by the current excitation unit is applied to the battery pack.

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