Battery monitoring system

Abstract

The excitation signal generating section (6) generates an excitation signal VCSx by processing the in-phase signal REFI of the quadrature reference signal generated by the signal generating section (5), and the current excitation section (7) generates an excitation current based on the excitation signal VCSx using the voltage signals IxSP and IxSN and applies the excitation current to the battery cell (2). The impedance measuring section (10) measures the ac impedance of the battery cell (2) based on the excitation current measured by the current measuring section (8) and the voltage of the battery cell (2) measured by the voltage measuring section (9). The noise measuring section (11) measures the noise superimposed on the battery cell (2) as a noise voltage based on the excitation current and the voltage. The control section (4) selects the battery cell (2(4)) which is not set as a measurement target of the ac impedance among the battery cells (2(1) to 2(4)), measures the noise voltage in the vicinity of the measurement frequency f LO of the quadrature reference signal in a state where the current excitation section (7) connected to the battery cell (2(4)) is not operated and only the corresponding voltage measuring section (8) is operated, by the noise measuring section (11).

Description

[0001] Cross-referencing of related applications

[0002] This application is based on Japanese Patent Application No. 2020-149046, filed on September 4, 2020, the contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a system for monitoring multiple battery cells that make up a battery pack. Background Technology

[0004] In recent years, with the increasing prevalence of electric vehicles and other vehicles utilizing rechargeable batteries, the demand for battery management systems (BMS) for the safe use of rechargeable batteries has been growing. Regarding rechargeable batteries, by measuring their AC impedance, the internal state, including the battery's state of charge (SOC), can be estimated. For example, in Patent Document 1, each battery cell is equipped with a signal excitation unit for flowing current to the object being measured, a current measuring unit, and a voltage measuring unit for measuring the response voltage from the battery. The impedance is measured using the voltage and current values ​​obtained from these components. In this AC impedance method, only the signal component with the same frequency as the measurement frequency is detected, resulting in high noise removal capability and enabling measurement of a good signal-to-noise ratio (SNR).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2020 / 003841 Summary of the Invention

[0008] However, in battery packs, such as those used in electric vehicles and hybrid vehicles, an inverter is connected to drive the motor. When the vehicle is in motion, the inverter's drive current acts as a noise current superimposed on the battery current. In conventional impedance measurements, if a noise current containing a frequency component at or near the measurement frequency is superimposed on the excitation current, the impedance measurement result will be inaccurate. Therefore, accurate impedance measurements cannot be performed while the vehicle is in motion, and errors will also occur in the estimation of the internal state.

[0009] This disclosure was made in view of the above circumstances, and its purpose is to provide a battery monitoring system that can accurately measure the impedance of a secondary battery even in an environment where a noisy current flows.

[0010] According to the battery monitoring system described in technical solution 1, the excitation signal generation unit processes the in-phase signal of the quadrature reference signal generated by the reference signal generation unit to generate an excitation signal, and the current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell. The impedance measurement unit measures the AC impedance of the battery cell based on the excitation current measured by the current measurement unit and the voltage of the battery cell measured by the voltage measurement unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the voltage measurement unit and estimates the noise current.

[0011] The control unit selects one or more battery cells from a plurality of battery cells that are not designated as AC impedance measurement targets. While keeping the current generation unit connected to the selected battery cell off and activating only the corresponding voltage measurement unit, the noise measurement unit measures the noise voltage near the measurement frequency, which is equal to the frequency of the quadrature reference signal. With this control, the impedance measurement and noise voltage measurement of the battery cell can be performed in parallel without interfering with each other. Therefore, even when the battery pack is supplying power to the load, impedance and noise voltage measurements can be performed with high accuracy.

[0012] According to the battery monitoring system described in technical solution 2, the cell voltage measuring unit measures the voltage of the battery cell, and the resistance voltage measuring unit measures the voltage of the resistive element connected in series with multiple battery cells. Furthermore, the control unit, in the same manner as in technical solution 1, operates the resistance voltage measuring unit without activating the current generating unit. With this configuration, similar to technical solution 1, the measurement of the battery cell impedance and the measurement of the noise voltage can be performed in parallel without interfering with each other.

[0013] According to the battery monitoring system described in technical solution 3, the control unit sends the noise voltage measured by the noise measurement unit and the AC impedance measurement result from the impedance measurement unit to the upper-level system. Thus, the upper-level system can evaluate the AC impedance measurement result based on the noise voltage level.

[0014] According to the battery monitoring system described in technical solution 5, the control unit switches the battery cells designated as noise voltage measurement targets in a time-division manner to measure the AC impedance of all battery cells within a fixed period, and sends these measurement results to the upper-level system. Thus, the upper-level system can obtain the measurement results of the AC impedance of all battery cells within a fixed period. Attached Figure Description

[0015] The foregoing and other objects, features, and advantages of this disclosure become clearer with reference to the accompanying drawings and the detailed description below. The drawings are as follows.

[0016] Figure 1This is a functional block diagram showing the structure of the battery monitoring device in the first embodiment.

[0017] Figure 2 This is a diagram showing the structure of the excitation signal processing unit.

[0018] Figure 3 This is a diagram showing the structure of the current excitation unit.

[0019] Figure 4 This is a diagram showing the structure of the current measuring unit.

[0020] Figure 5 This is a diagram showing the structure of the voltage measuring unit.

[0021] Figure 6 This diagram illustrates an example of the communication methods between multiple battery monitoring devices and battery control devices.

[0022] Figure 7 It is a diagram representing the waveform of the quadrature reference signal.

[0023] Figure 8 It is a graph showing the waveform and spectrum of the excitation current.

[0024] Figure 9 It is a graph showing the spectrum of the excitation AC voltage under ideal conditions and the spectrum of the voltage output by the voltage measuring unit.

[0025] Figure 10 This is the case where noise current is superimposed. Figure 9 A fairly accurate diagram.

[0026] Figure 11 This is a flowchart illustrating the measurement process of the battery monitoring device.

[0027] Figure 12 This refers to the case where only the voltage measuring unit is activated. Figure 10 A fairly accurate diagram.

[0028] Figure 13 This is a functional block diagram illustrating the structure of the battery monitoring device in the second embodiment.

[0029] Figure 14 This is a functional block diagram showing the structure of the battery monitoring device in the third embodiment.

[0030] Figure 15 This is a time diagram illustrating an example of the control method used in the fourth embodiment when the battery monitoring device of the third embodiment measures impedance and noise.

[0031] Figure 16 This is a functional block diagram showing the structure of the battery monitoring device in the fifth embodiment.

[0032] Figure 17 This is a flowchart illustrating the measurement process of the battery monitoring device.

[0033] Figure 18 This is a diagram illustrating the impedance measurement in the impedance measurement section.

[0034] Figure 19 This is a diagram showing an example of a data table representing impedance and noise values ​​at various frequencies.

[0035] Figure 20 This is a functional block diagram showing the structure of the battery monitoring device in the sixth embodiment.

[0036] Figure 21 This is a functional block diagram showing the structure of the battery monitoring device in the seventh embodiment. Detailed Implementation

[0037] (First Implementation)

[0038] like Figure 1 As shown, the battery pack 1 is constructed by connecting multiple, for example, four battery cells 2(1) to 2(4) in series. The battery cells 2 are, for example, secondary batteries such as lithium-ion batteries. The battery pack monitoring device 3 connected to the battery pack 1 includes a control unit 4, a signal generation unit 5, an excitation signal processing unit 6, a current excitation unit 7, a current measuring unit 8, a voltage measuring unit 9, an impedance measuring unit 10, a noise measuring unit 11, and a communication I / F 12. The current excitation unit 7, the current measuring unit 8, and the voltage measuring unit 9 are provided corresponding to each battery cell 2. The communication I / F 12 is used for communication between the battery pack monitoring device 3 and the upper-level system described later.

[0039] Voltage measuring units 8(1) to 8(4) are connected to the upper and lower electrodes of each battery cell 2(1) to 2(4), respectively. Signal generating unit 5 generates signals as shown in the figure. Figure 7 The frequency shown is the same as the measured frequency f. LO The same sine and cosine waves are the quadrature reference signals REFI and REFQ. These quadrature reference signals REFI and REFQ are output to the current measurement unit 8 and the voltage measurement unit 9. Only the reference signal REFI is input to the excitation signal processing unit 6.

[0040] like Figure 2 As shown, the excitation signal processing unit 6, which is equivalent to the excitation signal generation unit, performs a level shift on the input reference signal REFI according to the target excitation current set by the control unit 4 via the level converter 21, that is, it applies a DC bias, and then further converts it into an analog voltage signal via the DAC 22. The analog voltage signal is then input to the error amplifier 24 after the image component imparted in the demodulation process is removed by the filter 23.

[0041] For the inverting input terminal of the error amplifier 24, a voltage signal IxSP from the current excitation unit 7 is input. The output signal VCSx is controlled in such a way that the potential difference between the voltage signal IxSP and the voltage signal IxSN is consistent with the voltage signal provided to the non-inverting input terminal as a control target value. Furthermore, x = 1 to 4. The excitation current output from the current excitation unit 7 is as follows: Figure 8 The image shows an alternating current that has been DC biased, and its frequency components include a DC component and the measured frequency f. LO .

[0042] like Figure 3 As shown, the current excitation unit 7, which corresponds to the current generation unit, includes a series circuit of a resistive element RLx, an N-channel MOSFET_Mx, and a resistive element RSx. The output signal VCSx of the excitation signal processing unit 6 is provided to the gate of the FET_Mx, and the two ends of the resistive element RSx are input as voltage signals IxSP and IxSN to the excitation signal processing unit 6 and the current measurement unit 8, respectively. Furthermore, the two ends of the series circuit are output as excitation current signals IxFP and IxFN. That is, the current excitation unit 7 generates excitation current signals IxFP and IxFN in a manner that makes the terminal voltage of the element RSx, which serves as a sensing resistor, consistent with the control target value.

[0043] like Figure 4 As shown, the current measuring unit 8 includes subtractors 25P and 25N, an ADC 26, a DC bias correction unit 27, a subtractor 28, a filter 29, and a quadrature demodulator 30. Voltage signals IxSP and IxSN are input to the ADC 26 via subtractors 25P and 25N, respectively. The voltage data converted by the ADC 26 is input to the DC bias correction unit 27 and the subtractor 28. The DC bias correction unit 27 generates a DC bias correction value corresponding to the output data of the ADC 26 and inputs it to the subtractors 25 and 28.

[0044] The output data of subtractor 28 is input to quadrature demodulator 30 via filter 29. Quadrature demodulator 30 includes multipliers 31I and 31Q, and filters 32I and 32Q. The output data of filter 29 is input to multipliers 31I and 31Q. For multipliers 31I and 31Q, reference signals REFI and REFQ are also input respectively, and the input signals are multiplied to perform quadrature demodulation. The output data of multipliers 31I and 31Q are filtered by filters 32I and 32Q to remove image components, generating data IxBI and IxBQ, which are input to impedance measurement unit 10 and noise measurement unit 11.

[0045] Furthermore, the structure of the voltage measuring unit 9 is as follows: Figure 5As shown, it is symmetrical to the current measuring unit 8, and the corresponding structural elements are given the same symbols. For the voltage measuring unit 9, the terminal voltages VxSP and VxSN of the corresponding battery cell 2 are input, and quadrature demodulation is performed in the same manner as the current measuring unit 8 to generate data VxBI and VxBQ, which are then input to the impedance measuring unit 10 and the noise measuring unit 11. Furthermore, in the battery monitoring device 3, the parts other than the current excitation unit 7 are configured as an integrated circuit 33.

[0046] When the excitation current is applied to battery cell 2, it is converted into voltage through an AC impedance. The ideal spectrum of the excitation voltages VxSP and VxSN generated across battery cell 2 is as follows: Figure 9 As shown, it includes a DC component and is measured at frequency f. LO The signal is generated below. The DC component is the sum of the product of the voltage and impedance of battery cell 2 and the DC bias of the excitation current, at frequency f. LO Under these conditions, the product of the AC impedance and the excitation AC current is generated, which is the AC voltage. At this time, the voltage output by the voltage measuring unit 9 is only the DC voltage of the battery cell 2.

[0047] On the other hand, such as Figure 10 As shown, if noise is included in the input voltage due to the flow of noise current, the voltage measurement result will exhibit a DC component and a spectrum with a small frequency band in its vicinity. Previously, this was a major cause of error in impedance measurements.

[0048] In fact, such as Figure 6 As shown, multiple battery packs 1 are connected in series, and each battery pack 1 is connected to a battery monitoring device 3. The multiple battery monitoring devices 3 communicate with the ECU, i.e., the battery control unit 34, which is a higher-level system. The communication I / F 12 between the battery control unit 34 and each battery monitoring device 3 is, for example, daisy-chained.

[0049] Next, the function of this embodiment will be explained. An example is shown where the impedance of battery cells 2(1) to 2(3) is measured, and noise is measured in battery cell 2(4). Figure 11 As shown, the battery control device 34 sends a measurement frequency f to the battery monitoring device 3. LO The impedance measurement object is, in this case, battery cells 2(1) to 2(3) and the measurement start command (A1).

[0050] When the control unit 4 of the battery monitoring device 3 receives the measurement start command, it causes the excitation signal processing units 6(1) to 6(3) to generate VCSx as a DC voltage value. Then, the current excitation units 7(1) to 7(3) control the voltages IxFP and IxFN to connect the DC current (B1) corresponding to the voltage value VCSx.

[0051] At this time, for the current measuring units 8(1) to 8(3), signals IxSP and IxSN, which are DC bias signals corresponding to the DC current, are input from the current excitation units 7(1) to 7(3). Similarly, for the voltage measuring units 9(1) to 9(3), the terminal voltages VxSP and VxSN of the battery cells 2(1) to 2(3) are input as DC bias signals, respectively. Then, the current measuring units 8(1) to 8(3) and the voltage measuring units 9(1) to 9(3) remove the DC bias (B2) contained in the input signals by the DC bias correction unit 27.

[0052] Next, the signal generation unit 5 generates orthogonal reference signals REFI and REFQ. The excitation signal processing units 6(1) to 6(3) and the current excitation units 7(1) to 7(3) pass an excitation current (B3) corresponding to the reference signal REFI. The current measuring units 8(1) to 8(3) measure the current flowing through the sensing resistor RS of the current excitation units 7(1) to 7(3), and the voltage measuring units 9(1) to 9(4) measure the voltage (B4) of the corresponding battery cells 2(1) to 2(4).

[0053] In this state, the impedance measuring unit 10 measures the impedance of battery cells 2(1) to 2(3), and the noise measuring unit 11 measures the noise (B5) of battery cell 2(4). Figure 12 This indicates the frequency spectrum of the signal output by the voltage and noise measurement unit 11 under this condition. Then, the control unit 4 sends the measured impedance and noise to the battery control device 34 (B6) via the communication I / F 12.

[0054] The battery control device 34 saves the impedance and noise received from the battery monitoring device 3 to a table (A2) for storing the latest measurement results. Then, it determines the accuracy level of the measurement results (A3) based on the noise level. If the accuracy level determination value is less than a specified value, the received impedance and noise measurement results, along with the determination value, are written into the data storage table for updating. On the other hand, if the determination value is above the specified value, the data storage table is not updated (A4).

[0055] As described above, in the battery pack monitoring device 3 of this embodiment, the excitation signal processing unit 6 processes the in-phase signal REFI of the quadrature reference signal generated by the signal generation unit 5 to generate an excitation signal VCSx. The current excitation unit 7 generates an excitation current based on the excitation signal VCSx using voltage signals IxSP and IxSN and supplies power to the battery cell 2. The impedance measurement unit 10 measures the AC impedance of the battery cell 2 based on the excitation current measured by the current measurement unit 8 and the voltage of the battery cell 2 measured by the voltage measurement unit 9. The noise measurement unit 11 measures the noise superimposed on the battery cell 2 as a noise voltage based on the excitation current and the voltage.

[0056] The control unit 4 selects the battery cell 2(4) among battery cells 2(1) to 2(4) that is not set as the measurement object for AC impedance. Under the condition that the current excitation unit 7 connected to the battery cell 2(4) is not activated, but only the corresponding voltage measuring unit 8 is activated, the noise measuring unit 11 measures the frequency f of the quadrature reference signal. LO The noise voltage is measured at the same frequency. If controlled in this way, the impedance measurement and noise voltage measurement of battery cell 2 can be performed in parallel without interfering with each other. Therefore, even when battery pack 1 is supplying power to the load, impedance and noise voltage measurements can be performed with high accuracy.

[0057] Then, the control unit 4 sends the noise voltage of battery cell 2 (4) and the AC impedance measurement result of the impedance measurement unit 10 to the battery control device 34. The battery control device 34 determines the accuracy level of the measurement result based on the noise voltage level. If the accuracy level determination value is less than a specified value, the received impedance and noise measurement results are written into the data storage table along with the determination value for updating. However, if the determination value is above the specified value, the table is not updated. In this way, the battery control device 34 determines whether to update the data storage table based on the accuracy level of the measurement result, thereby improving the accuracy of the measurement result.

[0058] (Second Implementation)

[0059] Hereinafter, the same symbols will be used for parts that are the same as in the first embodiment, and descriptions will be omitted; the different parts will be described. For example... Figure 13 As shown, in the second embodiment, the battery monitoring device 41 connects excitation current to battery cells 2(1) and 2(2) via the excitation signal processing unit 6(1) and the current excitation unit 7(1), and connects excitation current to battery cells 2(3) and 2(4) via the excitation signal processing unit 6(2) and the current excitation unit 7(2). Then, the excitation current connected to battery cells 2(1) and 2(2) is measured by the current measuring unit 8(1), and the excitation current connected to battery cells 2(3) and 2(4) is measured by the current measuring unit 8(2). The portion of the battery monitoring device 41 after removing the current excitation unit 7 is configured as an integrated circuit 42.

[0060] According to the second embodiment configured as described above, only two sets of excitation signal processing unit 6, current excitation unit 7 and current measuring unit 8 are used to connect the excitation current to the battery cells 2(1) to 2(4) and perform the measurement, thus reducing the circuit area.

[0061] (Third Implementation)

[0062] like Figure 14As shown, the battery monitoring device 43 of the third embodiment is obtained by modifying the battery monitoring device 41, and only measuring units 9(1) and 9(2) are used for voltage measurement. Moreover, a selector 44(1) is arranged between the battery cells 2(1) and 2(2) and the voltage measuring unit 9(1), and a selector 44(2) is arranged between the battery cells 2(3) and 2(4) and the voltage measuring unit 9(2). The switching of the selector 44 is controlled by the control unit 4.

[0063] That is, the voltage measurement of battery cells 2(1) and 2(2) is performed by the voltage measuring unit 9(1) by switching the selector 44(1), and the voltage measurement of battery cells 2(3) and 2(4) is performed by the voltage measuring unit 9(2) by switching the selector 44(2). The portion of the battery monitoring device 43 after removing the current excitation unit 7 is configured as an integrated circuit 45. According to the third embodiment configured as described above, the circuit area can be further reduced.

[0064] (Fourth Implementation)

[0065] Figure 15 The fourth embodiment shown is an example of the control method for measuring impedance and noise using the battery monitoring device 43 of the third embodiment. Impedance measurements #1 to #4 are performed in the same manner; only the content of "Impedance Measurement #1" is shown. It includes four measurement stages. In the first stage, the control unit 4 measures the impedance of battery cell 2(1) using voltage measurement unit 9(1), and measures the noise of battery cell 2(3) using voltage measurement unit 9(2). In the next second stage, the impedance of battery cell 2(2) is measured by voltage measurement unit 9(1), and the noise of battery cell 2(3) is measured by voltage measurement unit 9(2) in the same manner.

[0066] In the next third stage, the voltage measuring unit 9(1) measures the noise of battery cell 2(1), and the voltage measuring unit 9(2) measures the impedance of battery cell 2(3). In the fourth stage, the voltage measuring unit 9(1) similarly measures the noise of battery cell 2(1), and the voltage measuring unit 9(2) measures the impedance of battery cell 2(4). The measured impedances and noise voltages of battery cells 2(1) to 2(4) are sent to the battery control device 34. This measurement method is repeated sequentially.

[0067] As described above, according to the fourth embodiment, the control unit 4 switches the battery cells 2 designated as the noise voltage measurement targets in a time-division manner to measure the AC impedance of all battery cells 2 within a fixed period, and sends these measurement results to the battery control device 34. Thus, the battery control device 34 can grasp the measurement results of the AC impedance and noise voltage of all battery cells 2 within a fixed period.

[0068] (Fifth Implementation)

[0069] like Figure 16 As shown, the battery monitoring device 46 of the fifth embodiment is obtained by modifying the battery monitoring device 41. The output signal of the noise measurement unit 11 is input to the noise subtraction units 47(1) and 47(2), and the output signals of the noise subtraction units 47(1) and 47(2) are input to the impedance measurement unit 48. The part of the battery monitoring device 46 after removing the current excitation unit 7 is configured as an integrated circuit 49.

[0070] Next, the function of the fifth embodiment will be explained. An example is shown where the impedance of battery cell 2 (1) is measured and noise is measured in battery cell 2 (3). Figure 17 As shown, the battery control device 34 sends a measurement frequency f to the battery monitoring device 3. LO The measurement objects are, in this case, battery cells 2(1) and 2(3), the latest and previous impedance measurement value of battery cell 2(1), and the measurement start command (A7).

[0071] When the control unit 4 of the battery monitoring device 46 receives a measurement start command, it causes the excitation signal processing unit 6(1) to generate VCSx as a DC voltage value. The current excitation unit 7(1) controls the voltages IxFP and IxFN to connect the DC current (B7) corresponding to the voltage value VCSx. In addition, the latest impedance measurement value is transmitted to the noise reduction unit 47. Similar to the first embodiment, the current measurement unit 8(1) and the voltage measurement unit 9(1) remove the DC bias (B8) contained in the input signal by the DC bias correction unit 27.

[0072] Next, the signal generation unit 5 generates orthogonal reference signals REFI and REFQ. The excitation signal processing unit 6 (1) and the current excitation unit 7 (1) transmit an excitation current (B9) corresponding to the reference signal REFI. The current measuring unit 8 (1) measures the current flowing through the sensing resistor RS of the current excitation unit 7 (1), selects battery cell 2 (1) by selector 44 (1), and selects battery cell 2 (3) by selector 44 (2). Then, the voltage measuring units 9 (1) and 9 (2) measure the voltages V1 and V3 (B10) of battery cells 2 (1) and 2 (3), respectively.

[0073] In this state, the noise measurement unit 11 measures the noise (B11) of the battery cell 2 (3). The noise subtraction unit 47 calculates the noise voltage of the battery cell 2 (1) based on the latest impedance measurement values ​​Z1 and Z3 notified from the battery control device 34, and subtracts the noise voltage (B12) from the measured voltage V1. For details of this process, please refer to [reference needed]. Figure 18 Let me explain.

[0074] When the impedances of battery cells 2(1) and 2(3) are set to Z1 and Z3, the excitation current is set to Imeas, and the noise current is set to In, the voltages V1 and V3 of battery cells 2(1) and 2(3) are represented as follows.

[0075] V1 = Z1(In + Imeas)

[0076] V3=Z3·In

[0077] The latest measured values ​​are represented as follows, which is the product of impedance Z1 and noise current In.

[0078] Z1·In=V3·Z1 / Z3

[0079] If the product (Z1·In) is subtracted from the measured voltage V1, the product of the impedance Z1 and the excitation current Imeas is obtained.

[0080] V1-V3·Z1 / Z3=V1=Z1(In+Imeas)-V3·Z1 / Z3

[0081] =Z1·Imeas

[0082] In the next step B13, the impedance measurement unit 10 divides the product (Z1·Imeas) by the excitation current Imeas to obtain the impedance Z1 of the battery cell 2 (1). Then, the control unit 4 sends the measured impedance and noise to the battery control device 34 (B6) via the communication I / F 12.

[0083] When the battery control device 34 executes steps A2 and A3, it writes the received impedance and noise measurement results together with the accuracy level judgment value into the data storage table for updating. However, if the above judgment value is above the specified value, the data storage table (A6) is not updated.

[0084] Battery control device 34 performs frequency changes based on a frequency list while executing... Figure 17 The process shown enables the production of, for example, Figure 19 The table shown represents the impedance and noise values ​​at various frequencies. Therefore, the battery control device 34 can determine the frequencies with high noise levels.

[0085] As described above, according to the fifth embodiment, a noise subtraction unit 47 is disposed between the voltage measuring unit 9 and the impedance measuring unit 48. The noise subtraction unit 47 subtracts a value (V3·Z1 / Z3) from the voltage V1 output by the voltage measuring unit 9 (1), which is equivalent to the result obtained by multiplying the estimated noise current In by the measurement result Z1 of the AC impedance previously measured for the test object, namely the battery cell 2. As a result, the impedance measuring unit 48 can eliminate the influence of the noise current In to obtain the impedance Z1 of the battery cell 2 (1).

[0086] (Sixth Implementation Method)

[0087] like Figure 20 As shown, the battery monitoring device 50 of the sixth embodiment is obtained by modifying the battery monitoring device 46. A resistor element 51 for noise measurement is connected to the low potential side of the battery cell 2 (4), and the terminal voltage of the resistor element 51 is measured by the voltage measuring unit 9 (3). The measurement result of the voltage measuring unit 9 (3) is input to the noise measuring unit 11. The part of the battery monitoring device 46 after removing the current excitation unit 7 is configured as an integrated circuit 52. The voltage measuring units 9 (1) and 9 (2) correspond to the cell voltage measuring unit, and the voltage measuring unit 9 (3) corresponds to the resistor voltage measuring unit.

[0088] According to the sixth embodiment configured as described above, voltage measuring units 9(1) and 9(2) measure the voltage of battery cell 2, and voltage measuring unit 9(3) measures the voltage of resistive element 51 connected in series with multiple battery cells 2. Then, control unit 4 operates voltage measuring unit 9(3) without operating current excitation unit 7 to measure noise voltage. With this configuration, the measurement of impedance of battery cell 2 and the measurement of noise voltage can be performed in parallel without affecting each other.

[0089] (Seventh Implementation)

[0090] like Figure 21 As shown, the battery monitoring device 53 of the seventh embodiment is obtained by modifying the battery monitoring device 50. Selectors 54(1) and 54(2) are provided instead of selectors 44(1) and 44(2), and these selectors 54(1) and 54(2) can switch the input of the voltage of each terminal of battery cells 2(1) to 2(4). The part of the battery monitoring device 53 after removing the current excitation unit 7 is configured as an integrated circuit 55.

[0091] With this configuration, for example, the following control can be performed: battery cell 2 (1) is selected in selector 54 (1), and the impedance of battery cell 2 (1) is always measured; for the impedances of other battery cells 2 (2) to 2 (4), selector 54 (2) is switched to measure them in a time-division manner. In this way, it is possible to select, for example, battery cell 2 that needs to be monitored closely because its impedance at a frequency of 100 Hz has changed by more than 20% from its average value, and measure its impedance continuously.

[0092] As described above, according to the seventh embodiment, two sets of voltage measuring unit 9 and selector 54 are provided, configured such that the voltages of all battery cells 2(1) to 2(4) can be measured in a switching manner in selectors 54(1) and 54(2). Thus, for example, the following measurement control can be performed: by using selector 54(1), the cell 2(1) under close monitoring is fixedly selected for high-speed measurement, while the voltages of other ordinary battery cells 2(2) to 2(4) are sequentially selected by selector 54(2) for low-speed measurement.

[0093] (Other implementation methods)

[0094] The number of battery cells 2 is not limited to "4", as long as there are multiple cells.

[0095] The communication methods between multiple battery monitoring devices and battery control devices are not limited to daisy chain connections; bus, polling, and wireless communication methods can also be used.

[0096] The method of measuring battery cell 2 using selectors 54(1) and 54(2) in the seventh embodiment can also be applied to other embodiments.

[0097] This disclosure has been described with reference to embodiments, but it should be understood that this disclosure is not limited to these embodiments or constructions. This disclosure also includes various modifications and equivalent variations. In addition, various combinations, methods, and other combinations and methods that contain only one element, or more or less, also fall within the scope and spirit of this disclosure.

Claims

1. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The voltage measuring unit measures the voltage of the battery cell; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit selects one or more battery cells from the plurality of battery cells that are not set as the AC impedance measurement object. The control unit, while activating only the corresponding voltage measuring unit without activating the current generating unit connected to the selected battery cell, measures a noise voltage near a measurement frequency equal to the frequency of the quadrature reference signal via the noise measuring unit. It has a higher-level system that can communicate with the control unit. The control unit sends the noise voltage measured by the noise measurement unit and the AC impedance measurement result from the impedance measurement unit to the upper-level system. The higher-level system determines the accuracy level of the measurement result based on the received noise voltage, and determines whether the measurement result is valid.

2. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The voltage measuring unit measures the voltage of the battery cell; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit selects one or more battery cells from the plurality of battery cells that are not set as the AC impedance measurement object. The control unit, while activating only the corresponding voltage measuring unit without activating the current generating unit connected to the selected battery cell, measures a noise voltage near a measurement frequency equal to the frequency of the quadrature reference signal via the noise measuring unit. The device includes a selector for the voltage measuring unit to switch and measure the voltages of two or more battery cells. Two sets of the voltage measuring unit and the selector are provided. The configuration is such that the voltage of all battery cells can be measured in a switching manner in each selector.

3. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The voltage measuring unit measures the voltage of the battery cell; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit selects one or more battery cells from the plurality of battery cells that are not set as the AC impedance measurement object. The control unit, while activating only the corresponding voltage measuring unit without activating the current generating unit connected to the selected battery cell, measures a noise voltage near a measurement frequency equal to the frequency of the quadrature reference signal via the noise measuring unit. It includes a noise level subtraction unit disposed between the voltage measuring unit and the impedance measuring unit. The noise level subtraction unit subtracts a value from the voltage output by the voltage measurement unit, which is equivalent to the result obtained by multiplying the estimated noise current by the measurement result of the AC impedance previously measured for the battery cell being measured.

4. The battery monitoring system according to any one of claims 1 to 3, characterized in that, The control unit switches the battery cells designated as noise voltage measurement objects in a time-division manner to measure the AC impedance of all battery cells within a fixed period, and sends these measurement results to the upper-level system.

5. The battery monitoring system according to any one of claims 1 to 3, characterized in that, The current generating unit is configured to supply excitation current to two or more battery cells connected in series.

6. The battery monitoring system according to any one of claims 1 to 3, characterized in that, The control unit causes the noise measurement unit to measure noise while scanning the frequency set as the measurement target. The higher-level system generates a data table representing the noise values ​​at each frequency.

7. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The cell voltage measuring unit measures the voltage of the battery cell; The resistance-voltage measuring unit measures the voltage of the resistive element connected in series with the plurality of battery cells; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the resistance voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit operates the resistance voltage measuring unit without operating the current generating unit, and then uses the noise measuring unit to measure a noise voltage near a measurement frequency that is equal to the frequency of the quadrature reference signal. It has a higher-level system that can communicate with the control unit. The control unit sends the noise voltage measured by the noise measurement unit and the AC impedance measurement result from the impedance measurement unit to the upper-level system. The higher-level system determines the accuracy level of the measurement result based on the received noise voltage, and determines whether the measurement result is valid.

8. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The cell voltage measuring unit measures the voltage of the battery cell; The resistance-voltage measuring unit measures the voltage of the resistive element connected in series with the plurality of battery cells; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the resistance voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit operates the resistance voltage measuring unit without operating the current generating unit, and then uses the noise measuring unit to measure a noise voltage near a measurement frequency that is equal to the frequency of the quadrature reference signal. The device includes a selector for the voltage measuring unit to switch and measure the voltages of two or more battery cells. Two sets of the voltage measuring unit and the selector are provided. The configuration is such that the voltage of all battery cells can be measured in a switching manner in each selector.

9. A battery monitoring system for monitoring the battery status of multiple battery cells, characterized in that, have: The reference signal generation unit generates an alternating quadrature reference signal; The excitation signal generation unit processes the in-phase signal of the quadrature reference signal to generate an excitation signal; The current generation unit generates an excitation current based on the excitation signal and connects it to the battery cell; The current measuring unit measures the excitation current generated by the current generating unit. The cell voltage measuring unit measures the voltage of the battery cell; The resistance-voltage measuring unit measures the voltage of the resistive element connected in series with the plurality of battery cells; The impedance measuring unit measures the AC impedance of the battery cell based on the excitation current measured by the current measuring unit and the voltage measured by the voltage measuring unit. The noise measurement unit measures the noise superimposed on the battery cell as a noise voltage based on the voltage measured by the resistance voltage measurement unit, and estimates the noise current. as well as The control unit controls the measurement of the AC impedance and the noise voltage. The control unit operates the resistance voltage measuring unit without operating the current generating unit, and then uses the noise measuring unit to measure a noise voltage near a measurement frequency that is equal to the frequency of the quadrature reference signal. It includes a noise level subtraction unit disposed between the voltage measuring unit and the impedance measuring unit. The noise level subtraction unit subtracts a value from the voltage output by the voltage measurement unit, which is equivalent to the result obtained by multiplying the estimated noise current by the measurement result of the AC impedance previously measured for the battery cell being measured.

10. The battery monitoring system according to any one of claims 7 to 9, characterized in that, The control unit switches the battery cells designated as noise voltage measurement objects in a time-division manner to measure the AC impedance of all battery cells within a fixed period, and sends these measurement results to the upper-level system.

11. The battery monitoring system according to any one of claims 7 to 9, characterized in that, The current generating unit is configured to supply excitation current to two or more battery cells connected in series.

12. The battery monitoring system according to any one of claims 7 to 9, characterized in that, The control unit causes the noise measurement unit to measure noise while scanning the frequency set as the measurement target. The higher-level system generates a data table representing the noise values ​​at each frequency.

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