WO2024134867A1 - Battery diagnosis device, battery diagnosis method - Google Patents

Battery diagnosis device, battery diagnosis method Download PDF

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WO2024134867A1
WO2024134867A1 PCT/JP2022/047597 JP2022047597W WO2024134867A1 WO 2024134867 A1 WO2024134867 A1 WO 2024134867A1 JP 2022047597 W JP2022047597 W JP 2022047597W WO 2024134867 A1 WO2024134867 A1 WO 2024134867A1
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battery
calculation unit
period
frequency
time
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PCT/JP2022/047597
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French (fr)
Japanese (ja)
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亨 河野
隼 角田
アキラ 藤本
穣 植田
博也 藤本
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株式会社日立ハイテク
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Priority to PCT/JP2022/047597 priority Critical patent/WO2024134867A1/en
Publication of WO2024134867A1 publication Critical patent/WO2024134867A1/en

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  • the present invention relates to technology for diagnosing the condition of a battery.
  • Various methods have been proposed for diagnosing the state of a battery (e.g., state of charge, state of health). For example, there is a method that estimates the state of deterioration of a battery based on the change in battery voltage over time during the rest period after the end of charging and discharging operations. There is also a method that diagnoses a battery by performing analytical processing such as a Fourier transform on the battery impedance.
  • Patent Document 1 describes the technology that "The present invention aims to provide a technology that can simultaneously measure the internal resistance and degradation state of a battery by simple means in a short time.
  • the battery management device of the present invention obtains a first difference between the voltage at a first calculation point after the end point of charging or discharging and the voltage at a first time point when a first period has elapsed from the first calculation point, and further obtains a second difference between the voltage at a second calculation point after the first time point and the voltage at a second time point when a second period has elapsed from the second calculation point, estimates the internal resistance according to the relationship between the first difference and the internal resistance of the battery, and estimates the degradation state according to the relationship between the second difference and the degradation state of the battery (see FIG. 7)" (see abstract).
  • the performance of devices e.g. chargers
  • the cut-off performance for cutting off the battery current after charging and discharging operations are stopped differs from device to device. Therefore, the time required from when charging and discharging operations are stopped until the charging and discharging current completely stops also varies. Accordingly, the change over time in the battery voltage during the rest period (the period after charging and discharging operations are stopped) also varies from device to device.
  • the present invention was made in consideration of the above-mentioned problems, and aims to provide a technology that can appropriately identify the battery voltage waveform used to diagnose the battery state, regardless of the performance of the device attached to the battery when the battery performs charging and discharging operations.
  • the battery diagnostic device of the present invention identifies a first period in the rest period after the battery has finished charging or discharging, converts the change in voltage in the first period into frequency components and phase components, identifies the phase components that are within a predetermined range as a target range, and estimates the state of the battery using the change in the target range.
  • the battery diagnostic device can appropriately identify the battery voltage waveform used to diagnose the battery state, regardless of the performance of the device attached to the battery when the battery performs charging and discharging operations.
  • Other issues, configurations, effects, etc. of the present invention will become clear from the description of the embodiments below.
  • FIG. 2 is an equivalent circuit diagram of a secondary battery cell 1.
  • FIG. FIG. 13 is an equivalent circuit diagram for impedance diagnosis.
  • 2 is an example of a Nyquist diagram of AC impedance of a secondary battery cell 1.
  • 2 is an example of a Nyquist diagram of AC impedance of a secondary battery cell 1.
  • 4 is an example showing the time-dependent variation of the battery voltage during a rest period of the secondary battery cell 1.
  • 4 is an example showing the time-dependent variation of the battery voltage during a rest period of the secondary battery cell 1.
  • 13 is an example of data describing the correspondence relationship between dV1 and the internal resistance 11.
  • 1 is an example of data describing the correspondence between dV2 and SOH.
  • FIG. 2 is a configuration diagram of a battery system.
  • FIG. 1 is an example of data describing the correspondence between dV2 and SOH.
  • FIG. 2 is a configuration diagram of a battery system.
  • FIG. 1 is an example of data describing the correspondence between
  • FIG. 2 is a diagram illustrating a configuration for charging a battery mounted on an electric vehicle EV.
  • FIG. 2 is a diagram illustrating a configuration for charging a battery mounted on an electric vehicle EV.
  • FIG. 13 is a flowchart illustrating another procedure for the battery diagnostic device 100 to diagnose a secondary battery cell 1 .
  • 4 is an example of a Fourier transform result of a battery voltage of a secondary battery cell 1.
  • FIG. 13 is a diagram showing a specific example of S1107.
  • 11 is an example of a C rate correction coefficient in S1109.
  • a specific example of S1110 will be shown.
  • Another specific example of S1110 will be described.
  • a specific example of S1112 is shown below.
  • 13 is an example of a user interface provided by the battery diagnosis device 100 according to the second embodiment.
  • ⁇ First embodiment> 1 is an equivalent circuit diagram of a secondary battery cell 1.
  • the secondary battery cell 1 can be represented by an internal resistance 11, a negative electrode 12, a positive electrode 13, and a diffused resistor 14.
  • FIG. 2 is an equivalent circuit diagram for impedance diagnosis.
  • the secondary battery cell 1 has an impedance Zc.
  • An AC voltage Vin is applied to the secondary battery cell 1, and an amplified voltage Vo is obtained corresponding to a reference resistance r0.
  • the impedance of the secondary battery cell 1 has a component caused by the negative electrode 12, a component caused by the positive electrode 13, a component caused by the diffusion resistance 14, and the like.
  • the component caused by the internal resistance 11 corresponds to the distance from the origin to the first zero cross point.
  • the RC time constant T anode of the negative electrode 12 is smaller than the RC time constant T cathode of the positive electrode 13. Therefore, in the time-dependent variation of the battery voltage during the rest period after the secondary battery cell 1 is charged and discharged, the component mainly caused by the negative electrode 12 appears first, and then the component mainly caused by the positive electrode 13 appears.
  • FIG. 3B is an example of a Nyquist diagram of the AC impedance of a secondary battery cell 1. While FIG. 3A shows an ideal waveform, FIG. 3B shows an example of an actually measured waveform.
  • Frequency region f1 is the component mainly caused by the internal resistance 11.
  • Frequency region f2 is the component mainly caused by the negative electrode 12.
  • Frequency region f3 is the component mainly caused by the positive electrode 13.
  • FIGS. 4A and 4B are examples showing the time-dependent variation of the battery voltage during the rest period of the secondary battery cell 1.
  • FIG. 4A shows the rest period after a charging operation
  • FIG. 4B shows the rest period after a discharging operation.
  • the battery voltage during the rest period changes sharply (dV1) in the first period t1, changes somewhat more slowly (dV2) in the next time t2, and changes even more slowly (dV3) in the next period t3.
  • t1 is a predetermined range from the origin to time 1/f1.
  • t2 is a predetermined range from the origin to 1/f2.
  • t3 is a predetermined range from the origin to 1/f3.
  • dV1 is a component mainly caused by the internal resistance 11
  • dV2 is a component mainly caused by the negative electrode 12
  • dV3 is a component mainly caused by the positive electrode 13.
  • dV1 corresponds well to the aging of the internal resistance 11
  • dV2 corresponds well to the SOH of the secondary battery cell 1.
  • these are used to diagnose the state of the secondary battery cell 1.
  • the specific steps of the diagnostic method will be described later.
  • the method of specifying which time range to use for t1 to t3 will be described again below.
  • FIG. 5A is an example of data describing the correspondence between dV1 and internal resistance 11.
  • dV1 corresponds well to internal resistance 11 (the vertical axis of FIG. 5A), so by obtaining the relationship between the two in advance by actual measurement or the like, saving data describing the results, and then referencing this with the actual measurement results of dV1, internal resistance 11 can be estimated.
  • Figure 5B is an example of data describing the correspondence between dV2 and SOH.
  • dV2 corresponds well to SOH (the vertical axis of Figure 5B), so if the relationship between the two is obtained in advance by actual measurement, data describing the results is saved, and this can be referenced using the actual measurement results of dV2 to estimate SOH.
  • FIG. 6 is a configuration diagram of a battery system.
  • the battery system is configured by a battery management unit (BMU) managing one or more battery modules 3.
  • BMU battery management unit
  • the battery module 3 is configured with one or more sub-modules 2, and the sub-modules 2 are configured with one or more secondary battery cells 1.
  • FIGS. 7A and 7B are diagrams explaining the configuration for charging a battery mounted on an electric vehicle (EV).
  • the battery mounted on an electric vehicle (EV) is connected to the motor via the main contactor and inverter.
  • a charging plug is connected to the normal charging contactor or quick charging contactor.
  • An emulator or an emulator and a (quick) charger are connected to the battery via the charging plug.
  • FIG. 7B shows an example of the configuration of a compact charger.
  • the quick charging contactor is configured to turn off (cut off the electrical connection between the charger and the battery) within a maximum of three seconds after the charging current becomes zero.
  • the emulator can connect to the EV using, for example, an in-vehicle communication protocol, and adjust the length of time until the quick charging contactor is cut off (e.g., to make it as long as possible).
  • FIG. 7C is a configuration diagram of the battery diagnostic device 100 according to the first embodiment.
  • the battery diagnostic device 100 can be configured as, for example, the emulator in FIGS. 7A and 7B, or as an external device that receives data describing the waveform of the battery voltage and uses the data to diagnose the battery.
  • the battery diagnostic device 100 comprises a detection unit 110, a calculation unit 120, and a memory unit 130.
  • the detection unit 110 acquires data describing the measurement results of the secondary battery cell 1, such as the battery voltage, battery current, and battery temperature, from, for example, a BMU.
  • the calculation unit 120 uses the data to diagnose the state of the secondary battery cell 1.
  • the memory unit 130 is a storage device that stores data used by the calculation unit 120 (e.g., the data in Figures 5A and 5B, the C-rate correction coefficient in Figure 14 described later, and various other data).
  • Figure 8 is an example showing how the charging current changes over time after the charger stops charging. Even if a command (charging stop signal) is issued to the charger to stop charging, the output current from the charger does not immediately become zero, but rather it takes a certain amount of time for the output current to become zero. Furthermore, it also takes a certain amount of time for the contactor that connects the charging plug (e.g. the quick charging contactor in Figures 7A-7B) to turn OFF after the output current becomes zero. In this example, the contactor turns OFF t1 (e.g. 3 seconds) after the charging current falls below I1.
  • a command charging stop signal
  • Figures 9A and 9B are examples showing the change in battery current over time during a rest period after a charging operation.
  • the battery current reaches zero relatively quickly after entering the rest period, whereas in Figure 9B it takes a longer time for the battery current to reach zero than in Figure 9A.
  • the time it takes for the battery current to reach zero varies depending on the performance of charging devices such as chargers and contactors (when discharging, the discharge destination device and contactors, etc.).
  • Figure 10 is an example showing the change over time in battery current and battery voltage during a pause period after a charging operation.
  • the time required for the battery current to reach 0 after entering the pause period is t10.
  • the battery voltage decreases as the battery current decreases, but continues to decrease slowly even after the battery current reaches 0.
  • FIG. 11A is a flowchart explaining the procedure by which the battery diagnostic device 100 diagnoses the secondary battery cell 1. A similar diagnostic procedure can also be performed on the submodule 2 and the battery module 3. Each step in FIG. 11 will be explained below.
  • the detection unit 110 acquires a waveform of the battery voltage over time during the rest period of the secondary battery cell 1 (for example, the one described in FIG. 10 ).
  • the battery voltage can be acquired, for example, via a battery management device. It may also be acquired by other appropriate means.
  • the calculation unit 120 acquires the voltage waveform (hereinafter, may be simply referred to as the voltage waveform) and stores data describing the results in the memory unit 130.
  • the calculation unit 120 calculates the Nyquist frequency fs of the voltage waveform. fs corresponds to half the reciprocal of the time from the start of the rest period until the battery current becomes zero (t10 in FIG. 10).
  • the calculation unit 120 specifies the frequency range to be analyzed in the Fourier transform of the voltage waveform.
  • the diagnosis is performed using the components of the voltage waveform that are mainly caused by the negative electrode 12, so the lower limit frequency f_LL and the upper limit frequency f_UL of the frequency range to be analyzed satisfy f_LL ⁇ (1/T anode ) ⁇ f_UL (i.e., the periphery of the components caused by the negative electrode 12 is analyzed). (1/T cathode ) ⁇ f_LL.
  • the specific values of f_LL and f_UL may be determined in advance, for example, by actual measurement, so that they are in a range that reliably includes f2 in FIG. 3.
  • Step S1103 Part 2 If f_UL ⁇ fs, the frequency range to be analyzed is f_LL to f_UL. If f_LL ⁇ fs ⁇ f_UL, the frequency range to be analyzed is f_LL to fs. If fs ⁇ f_LL, it is excluded from the analysis. In the following, as shown in FIG. 12, it is assumed that f_LL ⁇ fs ⁇ f_UL and the frequency range to be analyzed is f_LL to fs.
  • the calculation unit 120 performs a Fourier transform on the waveform of the battery voltage that changes over time from the start of the pause period to at least the end of t3 described in Fig. 4.
  • the result of the transform is stored in the storage unit 130.
  • the calculation unit 120 specifies an upper limit fa and a lower limit fb of the frequency analysis range (a "partial frequency range" of the Fourier transform result).
  • the calculation unit 120 specifies a phase ⁇ a corresponding to fa and a phase ⁇ b corresponding to fb based on the relationship between frequency and phase obtained from the Fourier transform of the voltage waveform.
  • ⁇ b can be specified as a phase that is, for example, 45° ahead of the phase corresponding to the Nyquist frequency in the phase-frequency characteristics of Fig. 12.
  • ⁇ a can be specified as a phase that is slightly ahead (by a value appropriately determined according to the properties of the battery, etc.) of the phase corresponding to the Nyquist frequency in the phase-frequency characteristics of Fig. 12.
  • fa and fb are frequencies corresponding to ⁇ a and ⁇ b, respectively.
  • the calculation section 120 specifies Gain_a corresponding to fa and Gain_b corresponding to fb based on the relationship between the frequency and amplitude (denoted as Gain in FIG. 12) obtained from the Fourier transform of the voltage waveform.
  • step S1107 The calculation unit 120 sets the time 1/fa as the start time and the time 1/fb as the end time.
  • the calculation unit 120 calculates the difference deltaV between the voltage V at the start time (start point) and the voltage V at the end time (end point). A specific example of this step will be described with reference to FIG. 13.
  • correction coefficient deltaV/(Gain_b-Gain_a). This correction coefficient is used to align the Nyquist diagram with the scale of the battery voltage. In other words, the horizontal axis of the corrected Nyquist diagram represents dV itself as described in FIG. 4.
  • Step S1109 Part 1
  • the calculation unit 120 multiplies the vertical and horizontal axes of the Nyquist diagram of the AC impedance of the secondary battery cell 1 by the correction coefficients in S1108. This makes it possible to identify dV1 to dV3 in Fig. 4 on the horizontal axis of the corrected Nyquist diagram. Specific examples of how these are identified will be described later.
  • FIG. 11A Step S1109: Part 2
  • a user may perform high-speed charging of a battery multiple times in a short period of time, perform a battery diagnosis for each charge, and identify the battery state by combining the results. This is because the battery voltage waveform is not necessarily the same each time charging is performed, and therefore the diagnosis results may vary. Since the battery state of charge changes each time charging is performed, the charging current (C rate) also changes each time charging is performed. As a result, dV2 also varies each time charging is performed. In order to standardize the diagnosis results each time charging is performed, it is desirable to perform diagnosis using the same C rate (i.e., using the same dV2 value).
  • the calculation unit 120 multiplies the Nyquist diagram by the C rate correction coefficient described in FIG. 14. This makes it possible to obtain a diagnosis result normalized using the same dV2.
  • the calculation section 120 creates a corrected Nyquist diagram (Cole-Cole plot) by multiplying the Nyquist diagram by the above two correction coefficients.
  • the calculation unit 120 specifies dV1 and dV2 on the corrected Nyquist diagram.
  • the horizontal axis of the corrected Nyquist diagram corresponds to dV itself in FIG. 4, so the specific regions on the horizontal axis correspond to dV1 to dV3, respectively. A specific example of specifying these will be described later in FIG. 15A.
  • dV1 to dV3 specified on the corrected Nyquist diagram will be referred to as dV1' to dV3'.
  • the calculation unit 120 estimates the internal resistance 11 by using dV1' and referring to the data described in Fig. 5A.
  • the calculation unit 120 estimates the SOH by using dV2' and referring to the data described in Fig. 5B. These are stored in the storage unit 130 as the results of diagnosing the state of the secondary battery cell 1.
  • step S1112 The calculation unit 120 determines dV3' on the corrected Nyquist diagram. A specific determination method will be described later with reference to FIG.
  • the calculation unit 120 calculates the ratio between dV3' and dv2'(dV3'/dv2'). If the ratio exceeds a threshold, it is determined that a transient excessive stress (e.g., C rate is too high) is being applied to the secondary battery cell 1. If the ratio is equal to or less than the threshold, it is determined that the stress on the secondary battery cell 1 is within the normal range. This determination result is stored in the memory unit 130 as a diagnostic result separate from the estimated results of SOH and internal resistance.
  • a transient excessive stress e.g., C rate is too high
  • FIG. 11B is a flowchart explaining another procedure in which the battery diagnostic device 100 diagnoses the secondary battery cell 1. Unlike FIG. 11A, S1111 is performed only if it is determined to be normal in S1113. The rest is the same as FIG. 11A.
  • FIG. 12 is an example of the Fourier transform result of the battery voltage of a secondary battery cell 1.
  • the upper part of FIG. 12 shows the phase frequency characteristic, and the lower part shows the amplitude frequency characteristic.
  • the upper limit frequency f_UL and the lower limit frequency f_LL in S1103 are set so as to include the components of the battery voltage waveform that are mainly caused by the negative electrode 12. Frequencies fa and fb are further identified as those to be used for battery diagnosis.
  • FIG. 13 is a diagram showing a specific example of S1107.
  • Time 1/fa corresponds to the start time of dV2
  • time 1/fb corresponds to the end time of dV2.
  • the calculation unit 120 calculates the difference deltaV in the battery voltage between the start time and the end time.
  • FIG. 14 is an example of the C rate correction coefficient in S1109. As shown in FIG. 14, the value of dV2 increases proportionally as the C rate increases.
  • the memory unit 130 stores data describing the relationship in FIG. 14 in advance as the C rate correction coefficient.
  • the calculation unit 120 corrects the actual measured value of dV2 for each charging operation by referring to the data in FIG. 14 using the C rate at the time of charging.
  • FIG. 15A shows a specific example of S1110.
  • the horizontal axis of the corrected Nyquist diagram represents dV in FIG. 4 itself, so the specific regions on the horizontal axis represent dV1 to dV3.
  • dV1 corresponds to the distance between the zero crossing point and the origin of the Nyquist plot.
  • dV2 corresponds to the frequency range fb to fa on the Nyquist diagram.
  • the calculation unit 120 can identify dV1 and dV2 as described above.
  • the calculation unit 120 must determine dV1 and dV2 after filling in any missing plots in the Nyquist diagram using an interpolation calculation or the like.
  • the plot portion used to determine dV1 is missing, so the calculation unit 120 determines dV1 after filling in the missing portion as shown by the dotted line in the figure.
  • FIG. 15B shows another specific example of S1110.
  • the end of dV2 may also be missing a plot. Even in this case, the calculation unit 120 complements the missing plot portion and estimates dV1 and dV2.
  • FIG. 16 shows a specific example of S1112.
  • dV3 is a component of the battery voltage waveform during the rest period that is caused by the positive electrode 13, and therefore appears later than dV2.
  • the component caused by the positive electrode 13 is located between the component caused by the diffused resistor 14 and the component caused by the negative electrode 12.
  • the end of the component caused by the negative electrode 12 is ⁇ b in FIG. 12. Since the component caused by the diffused resistor 14 has a constant phase (the angle is constant in FIG. 3), the point where the phase converges to a constant value in the phase-frequency characteristic in FIG. 12 is the starting point of the component caused by the diffused resistor 14. Therefore, dV3 can be identified as the frequency region sandwiched between these.
  • the calculation unit 120 identifies that frequency region in the corrected Nyquist diagram as dV3.
  • the calculation unit 120 can determine whether or not such stress is present based on the ratio (dV3'/dv2').
  • the battery diagnostic device 100 performs FFT on the battery voltage waveform during the rest period of the secondary battery cell 1, and specifies ⁇ a to ⁇ b on the phase characteristic obtained as a result as the analysis target range.
  • the position of dV2 on the time axis differs for each individual secondary battery cell 1, and the position is mainly caused by the frequency component caused by the negative electrode 12.
  • the component caused by the negative electrode 12 can be accurately specified as the analysis target range even if the time range of dV2 varies for each individual battery. This is because the phase frequency characteristic is obtained by the FFT, and the component caused by the negative electrode 12 appears in the phase frequency characteristic.
  • the significance of this embodiment is that it uses this property to specify the analysis target range.
  • the battery diagnostic device 100 converts the Nyquist diagram of the impedance of the secondary battery cell 1 into a scale corresponding to the time-varying waveform of the battery voltage of the secondary battery cell 1, and identifies the analysis range (dV2) on the converted Nyquist diagram.
  • This makes it possible to directly obtain dV2 on the Nyquist diagram by matching the phase range identified on the phase-frequency characteristic with the Nyquist diagram. In other words, not only is it possible to identify the time range in which dV2 is obtained for each individual secondary battery cell 1, but it is also possible to obtain dV2 itself during the identification process.
  • the battery diagnostic device 100 creates a Nyquist diagram after correcting the variation in dV2 caused by the difference in C rate each time a charging operation is performed on the secondary battery cell 1 using a C rate correction coefficient. This makes it possible to obtain diagnostic results in which the variation in C rate is standardized.
  • the battery diagnostic device 100 specifies dV1 to dV3 after complementing any missing plot points on the Nyquist diagram. This makes it possible to use the method according to this embodiment even when dV1 to dV3 do not appear clearly on the Nyquist diagram due to the characteristics of the secondary battery cell 1.
  • the battery diagnostic device 100 determines whether or not excessive stress is being applied to the secondary battery cell 1 according to the ratio between the component (dV3) attributable to the positive electrode 13 and the component (dV2) attributable to the negative electrode 12 in the battery voltage waveform. This makes it possible to diagnose a transient stress state in addition to the battery's state of health (SOH). Furthermore, this determination can be performed during the procedure for estimating the SOH and internal resistance.
  • Fig. 17 is an example of a user interface provided by the battery diagnosis device 100 according to the second embodiment of the present invention.
  • the calculation unit 120 can provide a user interface such as that shown in Fig. 17 on a display device such as an appropriate display, or via a network such as a Web application.
  • the other configurations are the same as those of the first embodiment.
  • the user interface can present, for example, the following information: the length of time (sampling time) during which the battery voltage waveform after the rest period was acquired; Nyquist frequency fs; f anode ; f cathode ; the value of the internal resistance 11; a graph of the battery voltage waveform; the time ranges of each of dV1 to dV3; a Nyquist plot of impedance (Nyquist plots after correction by each correction coefficient); the values of each of dV1 to dV3; and SOH.
  • the present invention is not limited to the above-described embodiment, and includes various modified examples.
  • the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those having all of the configurations described.
  • it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment and it is also possible to add the configuration of another embodiment to the configuration of one embodiment.
  • the state of the secondary battery cell 1 is diagnosed using the Fourier transform of the time-varying waveform of the battery voltage.
  • a transformation method other than the Fourier transform may be used as long as it is possible to obtain the phase frequency characteristics and amplitude frequency characteristics of the time-varying waveform of the battery voltage and to identify the regions on the impedance characteristics that correspond to these phase frequency characteristics and amplitude frequency characteristics.
  • the detection unit 110 and the calculation unit 120 can be configured by hardware such as a circuit device that implements the functions, or can be configured by a calculation device such as a CPU (Central Processing Unit) executing software that implements the functions.
  • a CPU Central Processing Unit
  • dV2 is set immediately before the start time of the idle period.
  • first period it is desirable to set each time of dV2 (first period) as follows: (a) start time: the time when more than twice the time length t10 from the start time of the idle period until the battery current becomes 0 has elapsed, (b) end time: the time when more than 0.1 seconds has elapsed from the start time of the idle period, (c) time length of dV2: 2 milliseconds or more and less than 100 milliseconds.

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Abstract

The purpose of the present invention is to provide technology with which it is possible to suitably specify a battery voltage waveform used to diagnose the battery state regardless of the performance of a device mounted on a battery when the battery performs a charge/discharge operation. A battery diagnosis device according to the present invention specifies a first period in an inactive period after the battery has finished a charging operation or a discharging operation, converts a first change in the voltage in the first period into a frequency component and a phase component, specifies the phase component within a prescribed range as a target range, and estimates the state of the battery using the amount of change corresponding to the target range (see fig. 12).

Description

電池診断装置、電池診断方法Battery diagnostic device and battery diagnostic method
　本発明は、電池の状態を診断する技術に関する。 The present invention relates to technology for diagnosing the condition of a battery.
　電池の状態（例：充電状態（Ｓｔａｔｅ　Ｏｆ　Ｃｈａｒｇｅ）、劣化状態（Ｓｔａｔｅ　Ｏｆ　Ｈｅａｌｔｈ））を診断する手法として、様々なものが提案されている。例えば充放電動作が終了した後の休止期間における電池電圧の経時変化にしたがって、電池の劣化状態を推定する手法がある。また、電池インピーダンスに対してフーリエ変換などの解析処理を実施することにより、電池を診断する手法がある。 Various methods have been proposed for diagnosing the state of a battery (e.g., state of charge, state of health). For example, there is a method that estimates the state of deterioration of a battery based on the change in battery voltage over time during the rest period after the end of charging and discharging operations. There is also a method that diagnoses a battery by performing analytical processing such as a Fourier transform on the battery impedance.
　下記特許文献１は、『本発明は、電池の内部抵抗と劣化状態を同時にかつ短時間で簡易な手段によって測定することができる技術を提供することを目的とする。本発明に係る電池管理装置は、充電または放電を終了した終了時点以後の第１起算時点における前記電圧と、前記第１起算時点から第１期間が経過した第１時点における前記電圧との間の第１差分を取得し、さらに、前記第１時点以後の第２起算時点における前記電圧と、前記第２起算時点から第２期間が経過した第２時点における前記電圧との間の第２差分を取得し、前記第１差分と前記電池の内部抵抗との間の関係にしたがって前記内部抵抗を推定し、前記第２差分と前記電池の劣化状態との間の関係にしたがって前記劣化状態を推定する（図７参照）。』という技術を記載している（要約参照）。 The following Patent Document 1 describes the technology that "The present invention aims to provide a technology that can simultaneously measure the internal resistance and degradation state of a battery by simple means in a short time. The battery management device of the present invention obtains a first difference between the voltage at a first calculation point after the end point of charging or discharging and the voltage at a first time point when a first period has elapsed from the first calculation point, and further obtains a second difference between the voltage at a second calculation point after the first time point and the voltage at a second time point when a second period has elapsed from the second calculation point, estimates the internal resistance according to the relationship between the first difference and the internal resistance of the battery, and estimates the degradation state according to the relationship between the second difference and the degradation state of the battery (see FIG. 7)" (see abstract).
ＷＯ２０２２０２４２３５WO2022024235
　電池が充放電動作を実施するとき電池に対して取り付けるデバイス（例：充電器）の性能は様々である。例えば充放電動作を停止した後の電池電流を遮断するための遮断性能はデバイスごとに異なる。したがって、充放電動作を停止してから充放電電流が完全に停止するまでの所要時間も様々に変動する。これにともない、休止期間（充放電動作を停止した後の期間）における電池電圧の経時変動も、デバイスごとに様々である。 The performance of devices (e.g. chargers) attached to batteries when the batteries are performing charge and discharge operations varies. For example, the cut-off performance for cutting off the battery current after charging and discharging operations are stopped differs from device to device. Therefore, the time required from when charging and discharging operations are stopped until the charging and discharging current completely stops also varies. Accordingly, the change over time in the battery voltage during the rest period (the period after charging and discharging operations are stopped) also varies from device to device.
　そうすると、特許文献１のように休止期間における電池電圧の経時変化を用いて電池状態を診断しようとするとき、電池電圧波形のうちどの部分を解析すべきかについても、充放電デバイスの性能によってばらつくことになる。 As a result, when attempting to diagnose the battery condition using the change over time in battery voltage during a rest period, as in Patent Document 1, the portion of the battery voltage waveform that should be analyzed will vary depending on the performance of the charging/discharging device.
　本発明は、上記のような課題に鑑みてなされたものであり、電池が充放電動作を実施するとき電池に対して取り付けるデバイスの性能によらず、電池状態を診断するために用いる電池電圧波形を適切に特定することができる技術を提供することを目的とする。 The present invention was made in consideration of the above-mentioned problems, and aims to provide a technology that can appropriately identify the battery voltage waveform used to diagnose the battery state, regardless of the performance of the device attached to the battery when the battery performs charging and discharging operations.
　本発明に係る電池診断装置は、電池が充電動作または放電動作を終了したあとの休止期間における第１期間を特定し、前記第１期間における前記電圧の変化分を、周波数成分と位相成分に変換し、前記位相成分のうち所定範囲内にあるものを対象範囲として特定し、前記対象範囲における前記変化分を用いて、前記電池の状態を推定する。 The battery diagnostic device of the present invention identifies a first period in the rest period after the battery has finished charging or discharging, converts the change in voltage in the first period into frequency components and phase components, identifies the phase components that are within a predetermined range as a target range, and estimates the state of the battery using the change in the target range.
　本発明に係る電池診断装置によれば、電池が充放電動作を実施するとき電池に対して取り付けるデバイスの性能によらず、電池状態を診断するために用いる電池電圧波形を適切に特定することができる。本発明のその他の課題、構成、効果などについては、以下の実施形態の説明により明らかとなる。 The battery diagnostic device according to the present invention can appropriately identify the battery voltage waveform used to diagnose the battery state, regardless of the performance of the device attached to the battery when the battery performs charging and discharging operations. Other issues, configurations, effects, etc. of the present invention will become clear from the description of the embodiments below.
２次電池セル１の等価回路図である。2 is an equivalent circuit diagram of a secondary battery cell 1. FIG. インピーダンス診断の等価回路図である。FIG. 13 is an equivalent circuit diagram for impedance diagnosis. ２次電池セル１の交流インピーダンスのナイキスト線図の例である。2 is an example of a Nyquist diagram of AC impedance of a secondary battery cell 1. ２次電池セル１の交流インピーダンスのナイキスト線図の例である。2 is an example of a Nyquist diagram of AC impedance of a secondary battery cell 1. ２次電池セル１の休止期間における電池電圧の経時変動を示す例である。4 is an example showing the time-dependent variation of the battery voltage during a rest period of the secondary battery cell 1. ２次電池セル１の休止期間における電池電圧の経時変動を示す例である。4 is an example showing the time-dependent variation of the battery voltage during a rest period of the secondary battery cell 1. ｄＶ１と内部抵抗１１との間の対応関係を記述したデータの例である。13 is an example of data describing the correspondence relationship between dV1 and the internal resistance 11. ｄＶ２とＳＯＨとの間の対応関係を記述したデータの例である。1 is an example of data describing the correspondence between dV2 and SOH. 電池システムの構成図である。FIG. 2 is a configuration diagram of a battery system. 電気自動車ＥＶが搭載しているバッテリを充電する構成を説明する図である。FIG. 2 is a diagram illustrating a configuration for charging a battery mounted on an electric vehicle EV. 電気自動車ＥＶが搭載しているバッテリを充電する構成を説明する図である。FIG. 2 is a diagram illustrating a configuration for charging a battery mounted on an electric vehicle EV. 実施形態１に係る電池診断装置１００の構成図である。1 is a configuration diagram of a battery diagnosis device 100 according to a first embodiment. 充電器が充電動作を停止した以後の充電電流の経時変化を示す例である。1 is an example showing a change in charging current over time after a charger stops a charging operation. 充電動作後の休止期間における電池電流の経時変化を示す例である。10 is an example showing a change in battery current over time during a rest period after a charging operation. 充電動作後の休止期間における電池電流の経時変化を示す例である。10 is an example showing a change in battery current over time during a rest period after a charging operation. 充電動作後の休止期間における電池電流と電池電圧それぞれの経時変化を示す例である。1 is an example showing changes over time in battery current and battery voltage during a rest period after a charging operation. 電池診断装置１００が２次電池セル１を診断する手順を説明するフローチャートである。4 is a flowchart illustrating a procedure for the battery diagnostic device 100 to diagnose a secondary battery cell 1 . 電池診断装置１００が２次電池セル１を診断する別手順を説明するフローチャートである。13 is a flowchart illustrating another procedure for the battery diagnostic device 100 to diagnose a secondary battery cell 1 . ２次電池セル１の電池電圧のフーリエ変換結果の１例である。4 is an example of a Fourier transform result of a battery voltage of a secondary battery cell 1. Ｓ１１０７の具体例を示す図である。FIG. 13 is a diagram showing a specific example of S1107. Ｓ１１０９におけるＣレート補正係数の例である。11 is an example of a C rate correction coefficient in S1109. Ｓ１１１０の具体例を示す。A specific example of S1110 will be shown. Ｓ１１１０の別具体例を示す。Another specific example of S1110 will be described. Ｓ１１１２の具体例を示す。A specific example of S1112 is shown below. 実施形態２に係る電池診断装置１００が提供するユーザインターフェースの例である。13 is an example of a user interface provided by the battery diagnosis device 100 according to the second embodiment.
＜実施の形態１＞
　図１は、２次電池セル１の等価回路図である。２次電池セル１は、内部抵抗１１、負極１２、正極１３、拡散抵抗１４によって表すことができる。 <First embodiment>
1 is an equivalent circuit diagram of a secondary battery cell 1. The secondary battery cell 1 can be represented by an internal resistance 11, a negative electrode 12, a positive electrode 13, and a diffused resistor 14.
　図２は、インピーダンス診断の等価回路図である。２次電池セル１はインピーダンスＺｃを有する。２次電池セル１に対して交流電圧Ｖｉｎを印加し、基準抵抗ｒ０に対応して増幅した電圧Ｖｏを得る。Ｚｃは以下の式によって表される：Ｚｃ＝－ｒ０・（Ｖｉｎ／Ｖｏ）。 Figure 2 is an equivalent circuit diagram for impedance diagnosis. The secondary battery cell 1 has an impedance Zc. An AC voltage Vin is applied to the secondary battery cell 1, and an amplified voltage Vo is obtained corresponding to a reference resistance r0. Zc is expressed by the following formula: Zc = -r0 (Vin/Vo).
　図３Ａは、２次電池セル１の交流インピーダンスのナイキスト線図の例である。図３Ａに示すように、２次電池セル１のインピーダンスは、負極１２に起因する成分、正極１３に起因する成分、拡散抵抗１４に起因する成分、などを有する。内部抵抗１１に起因する成分は、原点から最初のゼロクロス点までの距離に相当する。負極１２のＲＣ時定数Ｔａｎｏｄｅ＜正極１３のＲＣ時定数Ｔｃａｔｈｏｄｅである。したがって、２次電池セル１に対して充放電動作を実施した後の休止期間における電池電圧の経時変動においては、主に負極１２に起因する成分が先に現れ、次に主に正極１３に起因する成分が現れる。 3A is an example of a Nyquist diagram of the AC impedance of the secondary battery cell 1. As shown in FIG. 3A, the impedance of the secondary battery cell 1 has a component caused by the negative electrode 12, a component caused by the positive electrode 13, a component caused by the diffusion resistance 14, and the like. The component caused by the internal resistance 11 corresponds to the distance from the origin to the first zero cross point. The RC time constant T anode of the negative electrode 12 is smaller than the RC time constant T cathode of the positive electrode 13. Therefore, in the time-dependent variation of the battery voltage during the rest period after the secondary battery cell 1 is charged and discharged, the component mainly caused by the negative electrode 12 appears first, and then the component mainly caused by the positive electrode 13 appears.
　図３Ｂは、２次電池セル１の交流インピーダンスのナイキスト線図の例である。図３Ａは理想的な波形を表すのに対して、図３Ｂは実測波形の１例を示す。周波数領域ｆ１は、主に内部抵抗１１に起因する成分である。周波数領域ｆ２は、主に負極１２に起因する成分である。周波数領域ｆ３は、主に正極１３に起因する成分である。２次電池セル１の状態を高速診断するためには、ＲＣ時定数が小さい負極１２に起因する成分を解析することが望ましい。したがって、周波数領域ｆ２を適切に特定してこれを解析することが望ましい。 FIG. 3B is an example of a Nyquist diagram of the AC impedance of a secondary battery cell 1. While FIG. 3A shows an ideal waveform, FIG. 3B shows an example of an actually measured waveform. Frequency region f1 is the component mainly caused by the internal resistance 11. Frequency region f2 is the component mainly caused by the negative electrode 12. Frequency region f3 is the component mainly caused by the positive electrode 13. To quickly diagnose the state of the secondary battery cell 1, it is desirable to analyze the component caused by the negative electrode 12, which has a small RC time constant. Therefore, it is desirable to appropriately identify and analyze frequency region f2.
　図４Ａ～図４Ｂは、２次電池セル１の休止期間における電池電圧の経時変動を示す例である。図４Ａは充電動作後の休止期間を示し、図４Ｂは放電動作後の休止期間を示す。休止期間における電池電圧は、最初の期間ｔ１において急峻に変動し（ｄＶ１）、次の時間ｔ２においてやや緩やかに変動し（ｄＶ２）、次の期間ｔ３においてさらに緩やかに変動する（ｄＶ３）。ｔ１は、原点から時刻１／ｆ１までのうち所定範囲である。ｔ２は、原点から１／ｆ２までのうち所定範囲である。ｔ３は、原点から１／ｆ３までのうち所定範囲である。換言すると、ｄＶ１は主に内部抵抗１１に起因する成分であり、ｄＶ２は主に負極１２に起因する成分であり、ｄＶ３は主に正極１３に起因する成分である。 FIGS. 4A and 4B are examples showing the time-dependent variation of the battery voltage during the rest period of the secondary battery cell 1. FIG. 4A shows the rest period after a charging operation, and FIG. 4B shows the rest period after a discharging operation. The battery voltage during the rest period changes sharply (dV1) in the first period t1, changes somewhat more slowly (dV2) in the next time t2, and changes even more slowly (dV3) in the next period t3. t1 is a predetermined range from the origin to time 1/f1. t2 is a predetermined range from the origin to 1/f2. t3 is a predetermined range from the origin to 1/f3. In other words, dV1 is a component mainly caused by the internal resistance 11, dV2 is a component mainly caused by the negative electrode 12, and dV3 is a component mainly caused by the positive electrode 13.
　本発明者は、ｄＶ１が内部抵抗１１の経年劣化とよく対応しており、ｄＶ２が２次電池セル１のＳＯＨとよく対応していることを見出した。そこで本発明においては、これらを用いて２次電池セル１の状態を診断する。診断手法の具体的な手順については後述する。ｔ１～ｔ３としてどの時間領域を用いるかを特定する手法については、以下で改めて説明する。 The inventors have found that dV1 corresponds well to the aging of the internal resistance 11, and dV2 corresponds well to the SOH of the secondary battery cell 1. In the present invention, these are used to diagnose the state of the secondary battery cell 1. The specific steps of the diagnostic method will be described later. The method of specifying which time range to use for t1 to t3 will be described again below.
　図５Ａは、ｄＶ１と内部抵抗１１との間の対応関係を記述したデータの例である。上述のようにｄＶ１は内部抵抗１１（図５Ａの縦軸）とよく対応しているので、両者の関係をあらかじめ実測などによって取得し、その結果を記述したデータを保存しておいてこれをｄＶ１の実測結果によって参照することにより、内部抵抗１１を推定することができる。 FIG. 5A is an example of data describing the correspondence between dV1 and internal resistance 11. As described above, dV1 corresponds well to internal resistance 11 (the vertical axis of FIG. 5A), so by obtaining the relationship between the two in advance by actual measurement or the like, saving data describing the results, and then referencing this with the actual measurement results of dV1, internal resistance 11 can be estimated.
　図５Ｂは、ｄＶ２とＳＯＨとの間の対応関係を記述したデータの例である。上述のようにｄＶ２はＳＯＨ（図５Ｂの縦軸）とよく対応しているので、両者の関係をあらかじめ実測などによって取得し、その結果を記述したデータを保存しておいてこれをｄＶ２の実測結果によって参照することにより、ＳＯＨを推定することができる。 Figure 5B is an example of data describing the correspondence between dV2 and SOH. As mentioned above, dV2 corresponds well to SOH (the vertical axis of Figure 5B), so if the relationship between the two is obtained in advance by actual measurement, data describing the results is saved, and this can be referenced using the actual measurement results of dV2 to estimate SOH.
　図６は、電池システムの構成図である。電池システムは、１つ以上の電池モジュール３をバッテリ管理装置（ＢＭＵ）が管理することによって構成されている。電池モジュール３は１つ以上のサブモジュール２によって構成され、サブモジュール２は１つ以上の２次電池セル１によって構成されている。 FIG. 6 is a configuration diagram of a battery system. The battery system is configured by a battery management unit (BMU) managing one or more battery modules 3. The battery module 3 is configured with one or more sub-modules 2, and the sub-modules 2 are configured with one or more secondary battery cells 1.
　図７Ａ～図７Ｂは、電気自動車ＥＶが搭載しているバッテリを充電する構成を説明する図である。電気自動車ＥＶが備えるバッテリは、メインコンタクタとインバータを介してモータと接続されている。バッテリを充電する際は、ノーマルチャージングコンタクタまたはクイックチャージングコンタクタに対して充電プラグを接続する。充電プラグを介して、エミュレータまたはエミュレータと（急速）充電器が、バッテリに対して接続されることになる。図７Ｂは小型充電器の構成例である。 FIGS. 7A and 7B are diagrams explaining the configuration for charging a battery mounted on an electric vehicle (EV). The battery mounted on an electric vehicle (EV) is connected to the motor via the main contactor and inverter. When charging the battery, a charging plug is connected to the normal charging contactor or quick charging contactor. An emulator or an emulator and a (quick) charger are connected to the battery via the charging plug. FIG. 7B shows an example of the configuration of a compact charger.
　クイックチャージングコンタクタは、例えば充電電流が０になってから最長３秒以内にＯＦＦする（充電器とバッテリとの間の電気的接続を遮断する）ように構成されている。エミュレータは、例えば車載通信プロトコルを用いてＥＶと接続し、クイックチャージングコンタクタが遮断するまでの時間長を調整する（例：なるべく引き延ばす）ことができる。 The quick charging contactor is configured to turn off (cut off the electrical connection between the charger and the battery) within a maximum of three seconds after the charging current becomes zero. The emulator can connect to the EV using, for example, an in-vehicle communication protocol, and adjust the length of time until the quick charging contactor is cut off (e.g., to make it as long as possible).
　図７Ｃは、本実施形態１に係る電池診断装置１００の構成図である。電池診断装置１００は、例えば図７Ａ～図７Ｂにおけるエミュレータとして構成することもできるし、電池電圧の波形を記述したデータを受け取ってそのデータを用いて電池を診断する外部装置として構成することもできる。 FIG. 7C is a configuration diagram of the battery diagnostic device 100 according to the first embodiment. The battery diagnostic device 100 can be configured as, for example, the emulator in FIGS. 7A and 7B, or as an external device that receives data describing the waveform of the battery voltage and uses the data to diagnose the battery.
　電池診断装置１００は、検知部１１０、演算部１２０，記憶部１３０を備える。検知部１１０は、２次電池セル１の電池電圧、電池電流、電池温度、などの計測結果を記述したデータを、例えばＢＭＵから取得する。演算部１２０は、そのデータを用いて２次電池セル１の状態を診断する。記憶部１３０は、演算部１２０が用いるデータ（例：図５Ａと図５Ｂのデータ、後述する図１４のＣレート補正係数、その他各種データ）を格納する記憶装置である。 The battery diagnostic device 100 comprises a detection unit 110, a calculation unit 120, and a memory unit 130. The detection unit 110 acquires data describing the measurement results of the secondary battery cell 1, such as the battery voltage, battery current, and battery temperature, from, for example, a BMU. The calculation unit 120 uses the data to diagnose the state of the secondary battery cell 1. The memory unit 130 is a storage device that stores data used by the calculation unit 120 (e.g., the data in Figures 5A and 5B, the C-rate correction coefficient in Figure 14 described later, and various other data).
　図８は、充電器が充電動作を停止した以後の充電電流の経時変化を示す例である。充電動作を停止するように充電器に対する指令（充電停止信号）が出されたとしても、充電器からの出力電流は直ちに０になるのではなく、出力電流が０になるまである程度の時間を要する。さらに、出力電流が０になってから充電プラグを接続するコンタクタ（例：図７Ａ～図７Ｂのクイックチャージングコンタクタ）がＯＦＦとなるまでにも、ある程度の時間を要する。この例においては、充電電流がＩ１以下に低下してからｔ１（例：３秒）でコンタクタがＯＦＦする。 Figure 8 is an example showing how the charging current changes over time after the charger stops charging. Even if a command (charging stop signal) is issued to the charger to stop charging, the output current from the charger does not immediately become zero, but rather it takes a certain amount of time for the output current to become zero. Furthermore, it also takes a certain amount of time for the contactor that connects the charging plug (e.g. the quick charging contactor in Figures 7A-7B) to turn OFF after the output current becomes zero. In this example, the contactor turns OFF t1 (e.g. 3 seconds) after the charging current falls below I1.
　これらの時間は、充電器やコンタクタの性能に依拠する。すなわち、充電電流を遮断する性能（電流が０になるまでに要する時間）は、充電デバイスやコンタクタの性能によって様々に変動する可能性がある（後述する図９Ａ～図９Ｂに１例を示す）。放電時においても同様の変動が生じる。コンタクタがＯＦＦになると、それ以後の電池電圧の経時変動を取得することはできない。したがって、充放電動作にともなって電池診断を速やかに実施するためには、コンタクタがＯＦＦするよりも前に電池診断を完了することが望ましい。それ以後は電池電圧の経時変動をリアルタイムで取得できない（ログデータなどを介して後発的に取得しなければならない）ので時間的ロスが生じるからである。 These times depend on the performance of the charger and contactor. In other words, the performance of cutting off the charging current (the time it takes for the current to become 0) can vary depending on the performance of the charging device and contactor (one example is shown in Figures 9A and 9B, described later). Similar variations occur during discharging. Once the contactor is turned OFF, it is not possible to obtain any subsequent changes in the battery voltage over time. Therefore, in order to perform battery diagnosis promptly in conjunction with charging and discharging operations, it is desirable to complete the battery diagnosis before the contactor is turned OFF. This is because there is a time loss as the changes in the battery voltage over time cannot be obtained in real time after that (it must be obtained later via log data, etc.).
　図９Ａ～図９Ｂは、充電動作後の休止期間における電池電流の経時変化を示す例である。図９Ａにおいては、休止期間に入った後、電池電流が比較的速やかに０に達するのに対して、図９Ｂにおいては電池電流が０に達するまでに図９Ａよりも長い時間を要する。このように、電池電流が０に達するまでに要する時間は、充電器やコンタクタなどの充電デバイス（放電時は放電先デバイスおよびコンタクタなど）の性能によって変動する。 Figures 9A and 9B are examples showing the change in battery current over time during a rest period after a charging operation. In Figure 9A, the battery current reaches zero relatively quickly after entering the rest period, whereas in Figure 9B it takes a longer time for the battery current to reach zero than in Figure 9A. Thus, the time it takes for the battery current to reach zero varies depending on the performance of charging devices such as chargers and contactors (when discharging, the discharge destination device and contactors, etc.).
　図１０は、充電動作後の休止期間における電池電流と電池電圧それぞれの経時変化を示す例である。休止期間に入ってから電池電流が０になるまでの所要時間をｔ１０とする。電池電圧は、電池電流が低下するのにともなって低下するが、電池電流が０になった以降も緩やかに低下し続ける。 Figure 10 is an example showing the change over time in battery current and battery voltage during a pause period after a charging operation. The time required for the battery current to reach 0 after entering the pause period is t10. The battery voltage decreases as the battery current decreases, but continues to decrease slowly even after the battery current reaches 0.
　図１１Ａは、電池診断装置１００が２次電池セル１を診断する手順を説明するフローチャートである。同様の診断手順をサブモジュール２や電池モジュール３に対して実施することもできる。以下図１１の各ステップについて説明する。 FIG. 11A is a flowchart explaining the procedure by which the battery diagnostic device 100 diagnoses the secondary battery cell 1. A similar diagnostic procedure can also be performed on the submodule 2 and the battery module 3. Each step in FIG. 11 will be explained below.
（図１１Ａ：ステップＳ１１０１）
　検知部１１０は２次電池セル１の休止期間における電池電圧の経時変化波形（例えば図１０で説明したもの）を取得する。電池電圧は例えばバッテリ管理装置を介して取得することができる。その他適当な手段によって取得してもよい。演算部１２０はその電圧波形（以下では単に電圧波形と呼ぶ場合がある）を取得し、記憶部１３０にその結果を記述したデータを格納する。 (FIG. 11A: step S1101)
The detection unit 110 acquires a waveform of the battery voltage over time during the rest period of the secondary battery cell 1 (for example, the one described in FIG. 10 ). The battery voltage can be acquired, for example, via a battery management device. It may also be acquired by other appropriate means. The calculation unit 120 acquires the voltage waveform (hereinafter, may be simply referred to as the voltage waveform) and stores data describing the results in the memory unit 130.
（図１１Ａ：ステップＳ１１０２）
　演算部１２０は、電圧波形のナイキスト周波数ｆｓを算出する。ｆｓは、休止期間に入ってから電池電流が０になるまでの時間（図１０におけるｔ１０）の逆数の２分の１に相当する。 (FIG. 11A: step S1102)
The calculation unit 120 calculates the Nyquist frequency fs of the voltage waveform. fs corresponds to half the reciprocal of the time from the start of the rest period until the battery current becomes zero (t10 in FIG. 10).
（図１１Ａ：ステップＳ１１０３：その１）
　演算部１２０は、電圧波形のフーリエ変換のうち解析対象とする周波数範囲を特定する。本実施形態においては、電圧波形のうち主に負極１２に起因する成分を用いて診断を実施するので、解析する周波数範囲の下限周波数ｆ＿ＬＬと上限周波数ｆ＿ＵＬは、ｆ＿ＬＬ≦（１／Ｔａｎｏｄｅ）≦ｆ＿ＵＬを満たす（すなわち負極１２に起因する成分の周辺を解析する）。（１／Ｔｃａｔｈｏｄｅ）≦ｆ＿ＬＬとなる。ｆ＿ＬＬとｆ＿ＵＬの具体的な値は、図３のｆ２が確実に含まれる範囲となるように、例えばあらかじめ実測などによって定めておけばよい。 (FIG. 11A: Step S1103: Part 1)
The calculation unit 120 specifies the frequency range to be analyzed in the Fourier transform of the voltage waveform. In this embodiment, the diagnosis is performed using the components of the voltage waveform that are mainly caused by the negative electrode 12, so the lower limit frequency f_LL and the upper limit frequency f_UL of the frequency range to be analyzed satisfy f_LL≦(1/T anode )≦f_UL (i.e., the periphery of the components caused by the negative electrode 12 is analyzed). (1/T cathode )≦f_LL. The specific values of f_LL and f_UL may be determined in advance, for example, by actual measurement, so that they are in a range that reliably includes f2 in FIG. 3.
（図１１Ａ：ステップＳ１１０３：その２）
　ｆ＿ＵＬ＜ｆｓである場合は、解析する周波数範囲はｆ＿ＬＬ～ｆ＿ＵＬとなる。ｆ＿ＬＬ＜ｆｓ＜ｆ＿ＵＬである場合は、解析する周波数範囲はｆ＿ＬＬ～ｆｓとなる。ｆｓ＜ｆ＿ＬＬである場合は、解析対象外となる。以下では図１２が例示するように、ｆ＿ＬＬ＜ｆｓ＜ｆ＿ＵＬであり、解析する周波数範囲はｆ＿ＬＬ～ｆｓであるものとする。 (FIG. 11A: Step S1103: Part 2)
If f_UL<fs, the frequency range to be analyzed is f_LL to f_UL. If f_LL<fs<f_UL, the frequency range to be analyzed is f_LL to fs. If fs<f_LL, it is excluded from the analysis. In the following, as shown in FIG. 12, it is assumed that f_LL<fs<f_UL and the frequency range to be analyzed is f_LL to fs.
（図１１Ａ：ステップＳ１１０４）
　演算部１２０は、休止期間の開始時点から、少なくとも図４で説明したｔ３の終了時点までにおける、電池電圧の経時変化波形に対して、フーリエ変換を実施する。変換結果は記憶部１３０に格納する。 (FIG. 11A: step S1104)
The calculation unit 120 performs a Fourier transform on the waveform of the battery voltage that changes over time from the start of the pause period to at least the end of t3 described in Fig. 4. The result of the transform is stored in the storage unit 130.
（図１１Ａ：ステップＳ１１０５）
　演算部１２０は、周波数解析範囲（フーリエ変換結果の『一部の周波数範囲』）のうち、上限ｆａと下限ｆｂをそれぞれ特定する。演算部１２０は、電圧波形のフーリエ変換から得られる周波数と位相との間の関係に基づき、ｆａに対応する位相θａとｆｂに対応する位相θｂをそれぞれ特定する。 (FIG. 11A: step S1105)
The calculation unit 120 specifies an upper limit fa and a lower limit fb of the frequency analysis range (a "partial frequency range" of the Fourier transform result). The calculation unit 120 specifies a phase θa corresponding to fa and a phase θb corresponding to fb based on the relationship between frequency and phase obtained from the Fourier transform of the voltage waveform.
（図１１Ａ：ステップＳ１１０５：補足）
　θｂは、図１２の位相周波数特性のうち、ナイキスト周波数に対応する位相から例えば４５°進んだ位相として特定することができる。θａは、図１２の位相周波数特性のうち、ナイキスト周波数に対応する位相から若干（電池の性質などに応じて適宜定めた値）進んだ位相として特定することができる。ｆａとｆｂはそれぞれθａとθｂに対応する周波数である。 (FIG. 11A: Step S1105: Supplement)
θb can be specified as a phase that is, for example, 45° ahead of the phase corresponding to the Nyquist frequency in the phase-frequency characteristics of Fig. 12. θa can be specified as a phase that is slightly ahead (by a value appropriately determined according to the properties of the battery, etc.) of the phase corresponding to the Nyquist frequency in the phase-frequency characteristics of Fig. 12. fa and fb are frequencies corresponding to θa and θb, respectively.
（図１１Ａ：ステップＳ１１０６）
　演算部１２０は、電圧波形のフーリエ変換から得られる周波数と振幅（図１２においてはＧａｉｎとしている）との間の関係に基づき、ｆａに対応するＧａｉｎ＿ａとｆｂに対応するＧａｉｎ＿ｂをそれぞれ特定する。 (FIG. 11A: step S1106)
The calculation section 120 specifies Gain_a corresponding to fa and Gain_b corresponding to fb based on the relationship between the frequency and amplitude (denoted as Gain in FIG. 12) obtained from the Fourier transform of the voltage waveform.
（図１１Ａ：ステップＳ１１０７）
　演算部１２０は、時刻１／ｆａを開始時刻としてセットし、時刻１／ｆｂを終了時刻としてセットする。演算部１２０は、開始時刻における電圧Ｖ（開始点）と、終了時刻における電圧Ｖ（終了点）との間の差分ｄｅｌｔａＶを計算する。本ステップの具体例は図１３で説明する。 (FIG. 11A: step S1107)
The calculation unit 120 sets the time 1/fa as the start time and the time 1/fb as the end time. The calculation unit 120 calculates the difference deltaV between the voltage V at the start time (start point) and the voltage V at the end time (end point). A specific example of this step will be described with reference to FIG. 13.
（図１１Ａ：ステップＳ１１０８）
　演算部１２０は、以下の計算式によって補正係数を計算する：補正係数＝ｄｅｌｔａＶ／（Ｇａｉｎ＿ｂ－Ｇａｉｎ＿ａ）。この補正係数は、ナイキスト線図を、電池電圧のスケールと揃えるようにするためのものである。換言すると、補正後のナイキスト線図の横軸は、図４で説明したｄＶそのものを表すことになる。 (FIG. 11A: step S1108)
The calculation unit 120 calculates the correction coefficient by the following formula: Correction coefficient = deltaV/(Gain_b-Gain_a). This correction coefficient is used to align the Nyquist diagram with the scale of the battery voltage. In other words, the horizontal axis of the corrected Nyquist diagram represents dV itself as described in FIG. 4.
（図１１Ａ：ステップＳ１１０９：その１）
　演算部１２０は、２次電池セル１の交流インピーダンスのナイキスト線図の縦軸と横軸それぞれに対してＳ１１０８の補正係数を乗算する。これにより、補正後のナイキスト線図の横軸上で、図４のｄＶ１～ｄＶ３それぞれを特定することができることになる。これらを特定する具体例は後述する。 (FIG. 11A: Step S1109: Part 1)
The calculation unit 120 multiplies the vertical and horizontal axes of the Nyquist diagram of the AC impedance of the secondary battery cell 1 by the correction coefficients in S1108. This makes it possible to identify dV1 to dV3 in Fig. 4 on the horizontal axis of the corrected Nyquist diagram. Specific examples of how these are identified will be described later.
（図１１Ａ：ステップＳ１１０９：その２）
　ユーザは、バッテリの高速充電を短時間内に複数回実施し、各充電においてそれぞれ電池診断を実施し、それらの結果を総合して電池状態を特定する場合がある。電池電圧波形は充電を実施するごとに必ずしも同一ではなく、したがって診断結果もばらつく可能性があるからである。充電を実施するごとに電池の充電状態が変わるので、したがって充電電流（Ｃレート）も充電を実施するごとに変わる。これによりｄＶ２も充電を実施するごとに変動する。充電を実施するごとの診断結果を均一化するためには、同じＣレートを用いて（すなわち同じｄＶ２の値を用いて）診断を実施することが望ましい。そこでＣレートの変動にともなうｄＶ２の変動を補正するために、演算部１２０は図１４で説明するＣレート補正係数をナイキスト線図に対して乗算する。これにより、同じｄＶ２を用いて規格化した診断結果を得ることができる。 (FIG. 11A: Step S1109: Part 2)
A user may perform high-speed charging of a battery multiple times in a short period of time, perform a battery diagnosis for each charge, and identify the battery state by combining the results. This is because the battery voltage waveform is not necessarily the same each time charging is performed, and therefore the diagnosis results may vary. Since the battery state of charge changes each time charging is performed, the charging current (C rate) also changes each time charging is performed. As a result, dV2 also varies each time charging is performed. In order to standardize the diagnosis results each time charging is performed, it is desirable to perform diagnosis using the same C rate (i.e., using the same dV2 value). Therefore, in order to correct the variation in dV2 due to the variation in C rate, the calculation unit 120 multiplies the Nyquist diagram by the C rate correction coefficient described in FIG. 14. This makes it possible to obtain a diagnosis result normalized using the same dV2.
（図１１Ａ：ステップＳ１１０９：その３）
　演算部１２０は、以上の２つの補正係数をナイキスト線図に対して乗算することにより、補正後のナイキスト線図（コールコールプロット）を作成する。 (FIG. 11A: Step S1109: Part 3)
The calculation section 120 creates a corrected Nyquist diagram (Cole-Cole plot) by multiplying the Nyquist diagram by the above two correction coefficients.
（図１１Ａ：ステップＳ１１１０）
　演算部１２０は、補正したナイキスト線図上で、ｄＶ１とｄＶ２をそれぞれ特定する。補正したナイキスト線図の横軸は図４のｄＶそのものに対応するので、横軸上の特定の領域が、それぞれｄＶ１～ｄＶ３に対応する。これらを特定する具体例については後述の図１５Ａで説明する。補正後のナイキスト線図上で特定したｄＶ１～ｄＶ３を、便宜上、ｄＶ１’～ｄＶ３’と呼ぶ。 (FIG. 11A: step S1110)
The calculation unit 120 specifies dV1 and dV2 on the corrected Nyquist diagram. The horizontal axis of the corrected Nyquist diagram corresponds to dV itself in FIG. 4, so the specific regions on the horizontal axis correspond to dV1 to dV3, respectively. A specific example of specifying these will be described later in FIG. 15A. For convenience, dV1 to dV3 specified on the corrected Nyquist diagram will be referred to as dV1' to dV3'.
（図１１Ａ：ステップＳ１１１１）
　演算部１２０は、ｄＶ１’を用いて、図５Ａで説明したデータを参照することにより、内部抵抗１１を推定する。演算部１２０は、ｄＶ２’を用いて、図５Ｂで説明したデータを参照することにより、ＳＯＨを推定する。これらは２次電池セル１の状態を診断した結果として記憶部１３０へ格納される。 (FIG. 11A: step S1111)
The calculation unit 120 estimates the internal resistance 11 by using dV1' and referring to the data described in Fig. 5A. The calculation unit 120 estimates the SOH by using dV2' and referring to the data described in Fig. 5B. These are stored in the storage unit 130 as the results of diagnosing the state of the secondary battery cell 1.
（図１１Ａ：ステップＳ１１１２）
　演算部１２０は、補正したナイキスト線図上で、ｄＶ３’を特定する。具体的な特定手法については後述の図１６で説明する。 (FIG. 11A: step S1112)
The calculation unit 120 determines dV3' on the corrected Nyquist diagram. A specific determination method will be described later with reference to FIG.
（図１１Ａ：ステップＳ１１１３）
　演算部１２０は、ｄＶ３’とｄｖ２’との間の比率（ｄＶ３’／ｄｖ２’）を計算する。比率が閾値超であれば、２次電池セル１に対して過渡的な過剰ストレス（例：Ｃレートが高すぎる）がかかっていると判定する。比率が閾値以下であれば２次電池セル１に対するストレスは正常範囲であると判定する。この判定結果は、ＳＯＨと内部抵抗の推定結果とは別の診断結果として、記憶部１３０へ格納される。 (FIG. 11A: step S1113)
The calculation unit 120 calculates the ratio between dV3' and dv2'(dV3'/dv2'). If the ratio exceeds a threshold, it is determined that a transient excessive stress (e.g., C rate is too high) is being applied to the secondary battery cell 1. If the ratio is equal to or less than the threshold, it is determined that the stress on the secondary battery cell 1 is within the normal range. This determination result is stored in the memory unit 130 as a diagnostic result separate from the estimated results of SOH and internal resistance.
　図１１Ｂは、電池診断装置１００が２次電池セル１を診断する別手順を説明するフローチャートである。図１１Ａとは異なり、Ｓ１１１３において正常であると判定した場合のみ、Ｓ１１１１を実施する。その他は図１１Ａと同様である。 FIG. 11B is a flowchart explaining another procedure in which the battery diagnostic device 100 diagnoses the secondary battery cell 1. Unlike FIG. 11A, S1111 is performed only if it is determined to be normal in S1113. The rest is the same as FIG. 11A.
　図１２は、２次電池セル１の電池電圧のフーリエ変換結果の１例である。図１２上段は位相周波数特性を示し、下段は振幅周波数特性を示す。Ｓ１１０３における上限周波数ｆ＿ＵＬと下限周波数ｆ＿ＬＬは、電池電圧波形のうち主に負極１２に起因する成分を包含するようにセットする。周波数ｆａとｆｂは、そのなかでさらに電池診断のために用いるものとして特定される。 FIG. 12 is an example of the Fourier transform result of the battery voltage of a secondary battery cell 1. The upper part of FIG. 12 shows the phase frequency characteristic, and the lower part shows the amplitude frequency characteristic. The upper limit frequency f_UL and the lower limit frequency f_LL in S1103 are set so as to include the components of the battery voltage waveform that are mainly caused by the negative electrode 12. Frequencies fa and fb are further identified as those to be used for battery diagnosis.
　図１３は、Ｓ１１０７の具体例を示す図である。時刻１／ｆａはｄＶ２の開始時刻に相当し、時刻１／ｆｂはｄＶ２の終了時刻に相当する。演算部１２０は、開始時刻と終了時刻における電池電圧の差分ｄｅｌｔａＶを計算する。 FIG. 13 is a diagram showing a specific example of S1107. Time 1/fa corresponds to the start time of dV2, and time 1/fb corresponds to the end time of dV2. The calculation unit 120 calculates the difference deltaV in the battery voltage between the start time and the end time.
　図１４は、Ｓ１１０９におけるＣレート補正係数の例である。図１４に示すように、ｄＶ２の値は、Ｃレートが増加するにしたがって、比例的に増加する。記憶部１３０は、図１４の関係を記述したデータを、Ｃレート補正係数としてあらかじめ格納しておく。演算部１２０は、充電を実施するときのＣレートを用いて図１４のデータを参照することにより、充電実施ごとのｄＶ２の実測値を補正する。 FIG. 14 is an example of the C rate correction coefficient in S1109. As shown in FIG. 14, the value of dV2 increases proportionally as the C rate increases. The memory unit 130 stores data describing the relationship in FIG. 14 in advance as the C rate correction coefficient. The calculation unit 120 corrects the actual measured value of dV2 for each charging operation by referring to the data in FIG. 14 using the C rate at the time of charging.
　図１５Ａは、Ｓ１１１０の具体例を示す。補正後のナイキスト線図の横軸は、図４のｄＶそのものを表しているので、横軸上の特定の領域はｄＶ１～ｄＶ３それぞれを表している。ｄＶ１は、ナイキストプロットのゼロクロス点と原点との間の距離に相当する。ｄＶ２は、ナイキスト線図のうち周波数ｆｂ～ｆａの範囲に相当する。演算部１２０はｄＶ１とｄＶ２を以上のように特定することができる。 FIG. 15A shows a specific example of S1110. The horizontal axis of the corrected Nyquist diagram represents dV in FIG. 4 itself, so the specific regions on the horizontal axis represent dV1 to dV3. dV1 corresponds to the distance between the zero crossing point and the origin of the Nyquist plot. dV2 corresponds to the frequency range fb to fa on the Nyquist diagram. The calculation unit 120 can identify dV1 and dV2 as described above.
　演算部１２０は、ナイキスト線図のうちプロットが欠損している部分については、補間演算などによって補った上で、ｄＶ１とｄＶ２を特定する必要がある。図１５Ａにおいては、ｄＶ１を特定するために用いるプロット部分が欠損しているので、演算部１２０は同図の点線のように欠損部分を補完した上で、ｄＶ１を特定する。 The calculation unit 120 must determine dV1 and dV2 after filling in any missing plots in the Nyquist diagram using an interpolation calculation or the like. In FIG. 15A, the plot portion used to determine dV1 is missing, so the calculation unit 120 determines dV1 after filling in the missing portion as shown by the dotted line in the figure.
　図１５Ｂは、Ｓ１１１０の別具体例を示す。２次電池セル１の特性などによっては、ｄＶ２の端部もプロットが欠損している場合がある。この場合においても演算部１２０は、欠損しているプロット部分を補完した上で、ｄＶ１とｄＶ２を推定する。 FIG. 15B shows another specific example of S1110. Depending on the characteristics of the secondary battery cell 1, the end of dV2 may also be missing a plot. Even in this case, the calculation unit 120 complements the missing plot portion and estimates dV1 and dV2.
　図１６は、Ｓ１１１２の具体例を示す。ｄＶ３は、休止期間の電池電圧波形のうち正極１３に起因する成分であるので、ｄＶ２よりもさらに後に現れる。図３に示すように、正極１３に起因する成分は、拡散抵抗１４に起因する成分と負極１２に起因する成分との間に配置されている。負極１２に起因する成分の端部は、図１２におけるθｂである。拡散抵抗１４に起因する成分は、位相が一定である（図３において角度が一定である）ので、図１２の位相周波数特性のうち位相が一定値に収束した箇所が、拡散抵抗１４に起因する成分の開始点である。したがってｄＶ３は、これらによって挟まれた周波数領域として特定することができる。演算部１２０は、補正後のナイキスト線図におけるその周波数領域を、ｄＶ３として特定する。 FIG. 16 shows a specific example of S1112. dV3 is a component of the battery voltage waveform during the rest period that is caused by the positive electrode 13, and therefore appears later than dV2. As shown in FIG. 3, the component caused by the positive electrode 13 is located between the component caused by the diffused resistor 14 and the component caused by the negative electrode 12. The end of the component caused by the negative electrode 12 is θb in FIG. 12. Since the component caused by the diffused resistor 14 has a constant phase (the angle is constant in FIG. 3), the point where the phase converges to a constant value in the phase-frequency characteristic in FIG. 12 is the starting point of the component caused by the diffused resistor 14. Therefore, dV3 can be identified as the frequency region sandwiched between these. The calculation unit 120 identifies that frequency region in the corrected Nyquist diagram as dV3.
　２次電池セル１に対して過度なストレスがかかると、ｄＶ３が相対的に大きくなる。したがって演算部１２０は、Ｓ１１１３において、比率（ｄＶ３’／ｄｖ２’）に基づき、かかるストレスの有無を判定することができる。 If excessive stress is applied to the secondary battery cell 1, dV3 becomes relatively large. Therefore, in S1113, the calculation unit 120 can determine whether or not such stress is present based on the ratio (dV3'/dv2').
＜実施の形態１：まとめ＞
　本実施形態に係る電池診断装置１００は、２次電池セル１の休止期間における電池電圧波形に対してＦＦＴを実施し、その結果として得られる位相特性上のθａ～θｂまでを、解析対象範囲として特定する。２次電池セル１の個体ごとにｄＶ２の時間軸上の位置は異なり、その位置は負極１２に起因する周波数成分によって主に生じる。ＦＦＴの位相特性上で負極１２に起因する位相範囲を特定することにより、電池個体ごとにｄＶ２の時間範囲が変動したとしても、負極１２に起因する成分を解析対象範囲として正確に特定することができる。これは、ＦＦＴによって位相周波数特性が得られるとともに、その位相周波数特性のなかに負極１２に起因する成分が現れていることによる。本実施形態はこの性質を利用して、解析対象範囲を特定することに意義がある。 <Embodiment 1: Summary>
The battery diagnostic device 100 according to the present embodiment performs FFT on the battery voltage waveform during the rest period of the secondary battery cell 1, and specifies θa to θb on the phase characteristic obtained as a result as the analysis target range. The position of dV2 on the time axis differs for each individual secondary battery cell 1, and the position is mainly caused by the frequency component caused by the negative electrode 12. By specifying the phase range caused by the negative electrode 12 on the phase characteristic of the FFT, the component caused by the negative electrode 12 can be accurately specified as the analysis target range even if the time range of dV2 varies for each individual battery. This is because the phase frequency characteristic is obtained by the FFT, and the component caused by the negative electrode 12 appears in the phase frequency characteristic. The significance of this embodiment is that it uses this property to specify the analysis target range.
　本実施形態に係る電池診断装置１００は、２次電池セル１のインピーダンスのナイキスト線図を、２次電池セル１の電池電圧の経時変動波形に対応するスケールへ変換し、その変換後のナイキスト線図上で、解析対象範囲（ｄＶ２）を特定する。これにより、位相周波数特性上で特定した位相範囲を、ナイキスト線図に対して対応付けた上で、そのナイキスト線図上でｄＶ２を直接得ることができる。換言すると、ｄＶ２を取得する時間範囲を２次電池セル１の個体ごとに特定するのみならず、その特定過程においてｄＶ２そのものも得ることができる。 The battery diagnostic device 100 according to this embodiment converts the Nyquist diagram of the impedance of the secondary battery cell 1 into a scale corresponding to the time-varying waveform of the battery voltage of the secondary battery cell 1, and identifies the analysis range (dV2) on the converted Nyquist diagram. This makes it possible to directly obtain dV2 on the Nyquist diagram by matching the phase range identified on the phase-frequency characteristic with the Nyquist diagram. In other words, not only is it possible to identify the time range in which dV2 is obtained for each individual secondary battery cell 1, but it is also possible to obtain dV2 itself during the identification process.
　本実施形態に係る電池診断装置１００は、２次電池セル１に対して充電動作を実施するごとのＣレートの違いに起因するｄＶ２のばらつきを、Ｃレート補正係数によって補正した上で、ナイキスト線図を作成する。これにより、Ｃレートのばらつきを規格化した診断結果を得ることができる。 The battery diagnostic device 100 according to this embodiment creates a Nyquist diagram after correcting the variation in dV2 caused by the difference in C rate each time a charging operation is performed on the secondary battery cell 1 using a C rate correction coefficient. This makes it possible to obtain diagnostic results in which the variation in C rate is standardized.
　本実施形態に係る電池診断装置１００は、ナイキスト線図のプロット点が欠損している部分については、その欠損を補完した上で、ｄＶ１～ｄＶ３を特定する。これにより、２次電池セル１の特性によってナイキスト線図上でｄＶ１～ｄＶ３が明確に現れていない場合であっても、本実施形態に係る手法を用いることができる。 The battery diagnostic device 100 according to this embodiment specifies dV1 to dV3 after complementing any missing plot points on the Nyquist diagram. This makes it possible to use the method according to this embodiment even when dV1 to dV3 do not appear clearly on the Nyquist diagram due to the characteristics of the secondary battery cell 1.
　本実施形態に係る電池診断装置１００は、電池電圧波形のうち正極１３に起因する成分（ｄＶ３）と負極１２に起因する成分（ｄＶ２）との間の比率にしたがって、２次電池セル１に対して過度なストレスがかかっているか否かを判定する。これにより、電池の劣化状態（ＳＯＨ）に加えて、過渡的なストレス状態を診断することができる。さらに、ＳＯＨや内部抵抗を推定する手順のなかでこの判定を実施することができる。 The battery diagnostic device 100 according to this embodiment determines whether or not excessive stress is being applied to the secondary battery cell 1 according to the ratio between the component (dV3) attributable to the positive electrode 13 and the component (dV2) attributable to the negative electrode 12 in the battery voltage waveform. This makes it possible to diagnose a transient stress state in addition to the battery's state of health (SOH). Furthermore, this determination can be performed during the procedure for estimating the SOH and internal resistance.
＜実施の形態２＞
　図１７は、本発明の実施形態２に係る電池診断装置１００が提供するユーザインターフェースの例である。演算部１２０は、図１７のようなユーザインターフェースを、例えば適当なディスプレイなどの表示装置上で、あるいはＷｅｂアプリケーションなどのようなネットワーク経由で、提供することができる。その他の構成は実施形態１と同様である。 <Embodiment 2>
Fig. 17 is an example of a user interface provided by the battery diagnosis device 100 according to the second embodiment of the present invention. The calculation unit 120 can provide a user interface such as that shown in Fig. 17 on a display device such as an appropriate display, or via a network such as a Web application. The other configurations are the same as those of the first embodiment.
　ユーザインターフェースは例えば以下の情報を提示することができる：休止期間後の電池電圧波形を取得した時間長（サンプリング時間）；ナイキスト周波数ｆｓ；ｆａｎｏｄｅ；ｆｃａｔｈｏｄｅ；内部抵抗１１の値；電池電圧波形のグラフ；ｄＶ１～ｄＶ３それぞれの時間範囲；インピーダンスのナイキスト線図（各補正係数によって補正した後のナイキスト線図）；ｄＶ１～ｄＶ３それぞれの値；ＳＯＨ。 The user interface can present, for example, the following information: the length of time (sampling time) during which the battery voltage waveform after the rest period was acquired; Nyquist frequency fs; f anode ; f cathode ; the value of the internal resistance 11; a graph of the battery voltage waveform; the time ranges of each of dV1 to dV3; a Nyquist plot of impedance (Nyquist plots after correction by each correction coefficient); the values of each of dV1 to dV3; and SOH.
＜本発明の変形例について＞
　本発明は、前述した実施形態に限定されるものではなく、様々な変形例が含まれる。例えば、上記した実施形態は本発明を分かりやすく説明するために詳細に説明したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施形態の構成の一部を他の実施形態の構成に置き換えることが可能であり、また、ある実施形態の構成に他の実施形態の構成を加えることも可能である。また、各実施形態の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 <Modifications of the present invention>
The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.
　以上の実施形態において、図１１Ａ～図１１Ｂで説明した診断手順をサブモジュール２や電池モジュール３に対して実施する場合は、電池電圧波形やインピーダンスはサブモジュール２ごとあるいは電池モジュール３ごとに取得する。その他は以上の実施形態と同様である。 In the above embodiment, when the diagnostic procedure described in Figures 11A and 11B is performed on the submodule 2 or battery module 3, the battery voltage waveform and impedance are obtained for each submodule 2 or each battery module 3. The rest is the same as the above embodiment.
　以上の実施形態において、電池電圧の経時変化波形のフーリエ変換を用いて２次電池セル１の状態を診断することを説明したが、電池電圧の経時変化波形の位相周波数特性と振幅周波数特性を取得し、インピーダンス特性上でこれらの位相周波数特性と振幅周波数特性に対応する領域を特定することができるのであれば、フーリエ変換以外の変換手法を用いてもよい。 In the above embodiment, the state of the secondary battery cell 1 is diagnosed using the Fourier transform of the time-varying waveform of the battery voltage. However, a transformation method other than the Fourier transform may be used as long as it is possible to obtain the phase frequency characteristics and amplitude frequency characteristics of the time-varying waveform of the battery voltage and to identify the regions on the impedance characteristics that correspond to these phase frequency characteristics and amplitude frequency characteristics.
　以上の実施形態において、検知部１１０と演算部１２０は、その機能を実装した回路デバイスなどのハードウェアによって構成することもできるし、その機能を実装したソフトウェアをＣＰＵ（Ｃｅｎｔｒａｌ　Ｐｒｏｃｅｓｓｉｎｇ　Ｕｎｉｔ）などの演算装置が実行することによって構成することもできる。 In the above embodiment, the detection unit 110 and the calculation unit 120 can be configured by hardware such as a circuit device that implements the functions, or can be configured by a calculation device such as a CPU (Central Processing Unit) executing software that implements the functions.
　以上の実施形態において、充電器によって２次電池セル１を充電するときの遮断特性が充電器とコンタクタごとに異なる例を説明したが、放電先負荷とコンタクタごとに遮断特性が異なる場合においても、本発明を適用することができる。この場合は、図４Ａに代えて図４Ｂのように放電後の休止期間における電池電圧の経時変化を用いることになるが、その他は以上の実施形態と同じである。 In the above embodiment, an example was described in which the interruption characteristics when the secondary battery cell 1 is charged by a charger differ for each charger and contactor, but the present invention can also be applied when the interruption characteristics differ for each discharge destination load and contactor. In this case, the change over time in the battery voltage during the rest period after discharge, as shown in Figure 4B, is used instead of Figure 4A, but the rest is the same as the above embodiment.
　以上の実施形態において、２次電池セル１を高速に診断する観点から、ｄＶ２は休止期間の開始時刻から直近であることが望ましい。例えばｄＶ２（第１期間）の各時刻は以下のようにセットすることが望ましい。（ａ）開始時刻：休止期間の開始時刻から電池電流が０になるまでの時間長ｔ１０の２倍以上が経過した時刻、（ｂ）終了時刻：休止期間の開始時刻から０．１秒以上が経過した時刻、（ｃ）ｄＶ２の時間長：２ミリ秒以上１００ミリ秒未満。 In the above embodiment, from the viewpoint of quickly diagnosing the secondary battery cell 1, it is desirable that dV2 is set immediately before the start time of the idle period. For example, it is desirable to set each time of dV2 (first period) as follows: (a) start time: the time when more than twice the time length t10 from the start time of the idle period until the battery current becomes 0 has elapsed, (b) end time: the time when more than 0.1 seconds has elapsed from the start time of the idle period, (c) time length of dV2: 2 milliseconds or more and less than 100 milliseconds.
１００：電池診断装置
１１０：検知部
１２０：演算部 100: Battery diagnostic device 110: Detection unit 120: Calculation unit

Claims (18)

  1. 　電池の状態を診断する電池診断装置であって、
    　前記電池が出力する電圧の検出値を取得する検知部、
    　前記電池の状態を推定する演算部、
    　を備え、
    　前記演算部は、前記電池が充電動作または放電動作を終了したあとの休止期間における第１期間を特定し、
    　前記演算部は、前記第１期間における前記電圧の変化分を、周波数成分と位相成分に変換し、
    　前記演算部は、前記変換によって得られる前記位相成分のうち所定範囲内にあるものを特定するとともに、その特定した前記位相成分に対応する時間範囲における前記変化分を対象範囲として特定し、
    　前記演算部は、前記対象範囲における前記変化分を用いて、前記電池の状態を推定する
    　ことを特徴とする電池診断装置。     A battery diagnostic device for diagnosing a state of a battery, comprising:
    a detection unit that acquires a detection value of a voltage output by the battery;
    A calculation unit that estimates the state of the battery;
    Equipped with
    The calculation unit identifies a first period in a pause period after the battery has finished a charging operation or a discharging operation,
    The calculation unit converts the change in the voltage during the first period into a frequency component and a phase component,
    the calculation unit identifies the phase components obtained by the conversion that are within a predetermined range, and identifies the change in a time range corresponding to the identified phase components as a target range;
    the calculation unit estimates a state of the battery by using the change in the target range.
  2. 　前記演算部は、前記変化分を、周波数成分と位相成分との間の第１関係、および、周波数成分と振幅との間の第２関係、によって構成された周波数特性へ変換し、
    　前記演算部は、前記周波数特性に対応するナイキスト線図を生成し、
    　前記演算部は、前記ナイキスト線図の形状を用いて、前記電池の状態を推定する
    　ことを特徴とする請求項１記載の電池診断装置。     the calculation unit converts the change into a frequency characteristic that is configured by a first relationship between a frequency component and a phase component and a second relationship between a frequency component and an amplitude;
    The calculation unit generates a Nyquist diagram corresponding to the frequency characteristic,
    The battery diagnostic device according to claim 1 , wherein the calculation unit estimates the state of the battery by using a shape of the Nyquist diagram.
  3. 　前記演算部は、前記周波数特性のうち一部の周波数範囲のみを、前記対象範囲として解析することにより、前記電池の状態を推定し、
    　前記一部の周波数範囲は、前記周波数特性に含まれる周波数のうち、前記電池が備える負極の時定数によって定まる周波数およびその前後の所定範囲である
    　ことを特徴とする請求項２記載の電池診断装置。     The calculation unit estimates the state of the battery by analyzing only a part of a frequency range of the frequency characteristics as the target range,
    3. The battery diagnostic device according to claim 2, wherein the partial frequency range is a frequency determined by a time constant of a negative electrode of the battery, and a predetermined range around the frequency, among the frequencies included in the frequency characteristics.
  4. 　前記周波数特性は、
    　　前記電池が備える負極の時定数によって定まる第１周波数、
    　　前記電池が備える正極の時定数によって定まる第２周波数、
    　　前記休止期間が開始してから、前記充電動作における充電電流または前記放電動作における放電電流が０になるまでの時間によって定まる第３周波数、
    　を含んでおり、
    　前記演算部は、前記第１周波数を包含する下限周波数と上限周波数をセットし、
    　前記演算部は、前記第３周波数が前記上限周波数よりも高い場合は、前記一部の周波数範囲を前記下限周波数から前記上限周波数までとし、
    　前記演算部は、前記第３周波数が前記上限周波数と前記下限周波数との間である場合は、前記一部の周波数範囲を前記下限周波数から前記第３周波数までとし、
    　前記下限周波数は、前記第２周波数よりも高い
    　ことを特徴とする請求項３記載の電池診断装置。     The frequency characteristic is
    a first frequency determined by a time constant of a negative electrode of the battery;
    A second frequency determined by a time constant of a positive electrode of the battery;
    a third frequency determined by the time from the start of the pause period until the charging current in the charging operation or the discharging current in the discharging operation becomes zero;
    Contains
    The calculation unit sets a lower limit frequency and an upper limit frequency that include the first frequency,
    When the third frequency is higher than the upper limit frequency, the calculation unit sets the partial frequency range from the lower limit frequency to the upper limit frequency,
    When the third frequency is between the upper limit frequency and the lower limit frequency, the calculation unit sets the partial frequency range to the lower limit frequency to the third frequency,
    The battery diagnostic device according to claim 3 , wherein the lower limit frequency is higher than the second frequency.
  5. 　前記演算部は、前記一部の周波数範囲の上限と下限をそれぞれ特定し、
    　前記演算部は、前記第２関係のうち前記上限に対応する上限振幅と、前記第２関係のうち前記下限に対応する下限振幅とをそれぞれ特定し、
    　前記演算部は、前記下限振幅と前記上限振幅との間の第１差分を用いて、前記ナイキスト線図を補正し、
    　前記演算部は、前記補正した前記ナイキスト線図を用いて、前記電池の状態を推定する
    　ことを特徴とする請求項３記載の電池診断装置。     The calculation unit identifies an upper limit and a lower limit of the partial frequency range,
    the calculation unit identifies an upper limit amplitude corresponding to the upper limit of the second relationship and a lower limit amplitude corresponding to the lower limit of the second relationship,
    The calculation unit corrects the Nyquist diagram using a first difference between the lower limit amplitude and the upper limit amplitude;
    4. The battery diagnostic device according to claim 3, wherein the calculation unit estimates the state of the battery by using the corrected Nyquist diagram.
  6. 　前記演算部は、
    　　前記第１期間のうち前記上限に対応する時刻における前記電圧と、
    　　前記第１期間のうち前記下限に対応する時刻における前記電圧と、
    　の間の第２差分を求め、
    　前記演算部は、前記第２差分を前記第１差分によって除算した値を補正係数として前記ナイキスト線図に対して乗算することにより、前記ナイキスト線図を補正する
    　ことを特徴とする請求項５記載の電池診断装置。     The calculation unit is
    the voltage at a time corresponding to the upper limit during the first period; and
    the voltage at a time corresponding to the lower limit during the first period; and
    Find the second difference between
    The battery diagnostic device according to claim 5 , wherein the calculation unit corrects the Nyquist diagram by multiplying the Nyquist diagram by a value obtained by dividing the second difference by the first difference as a correction coefficient.
  7. 　前記演算部は、前記電池に対して実施される前記充電動作または前記放電動作のうち少なくとも２回について、前記変化分を用いた前記推定を実施し、
    　前記演算部は、各前記充電動作または各前記放電動作におけるＣレートの差異に起因して生じる、前記充電動作または前記放電動作ごとの前記変化分の差異を補正するためのＣレート補正係数を取得し、
    　前記演算部は、前記推定を実施する前に、前記Ｃレート補正係数を前記ナイキスト線図に対して乗算することにより、前記ナイキスト線図を補正し、その補正後の前記ナイキスト線図を用いて前記電池の状態を推定する
    　ことを特徴とする請求項６記載の電池診断装置。     The calculation unit performs the estimation using the change for at least two of the charging operation or the discharging operation performed on the battery,
    The calculation unit acquires a C-rate correction coefficient for correcting a difference in the change amount for each of the charging operations or the discharging operations caused by a difference in a C-rate in each of the charging operations or each of the discharging operations;
    7. The battery diagnostic device according to claim 6, wherein the calculation unit corrects the Nyquist diagram by multiplying the Nyquist diagram by the C-rate correction coefficient before performing the estimation, and estimates the state of the battery using the corrected Nyquist diagram.
  8. 　前記変化分は、前記電池が備える内部抵抗によって主に生じる第１部分と、前記電池が備える負極によって主に生じる第２部分とを有し、
    　前記演算部は、前記ナイキスト線図のうち前記第１部分に対応する第１領域と、前記ナイキスト線図のうち前記第２部分に対応する第２領域とをそれぞれ特定し、
    　前記演算部は、前記ナイキスト線図のうち前記第１領域または前記第２領域に相当する部分が欠損している場合は、その欠損している部分を推定することによって前記ナイキスト線図を補完し、
    　前記演算部は、前記欠損を補完した前記ナイキスト線図上の前記第１領域を用いて前記電池の内部抵抗を推定し、
    　前記演算部は、前記欠損を補完した前記ナイキスト線図上の前記第２領域を用いて前記電池の劣化状態を推定する
    　ことを特徴とする請求項２記載の電池診断装置。     The change has a first portion mainly caused by an internal resistance of the battery and a second portion mainly caused by a negative electrode of the battery,
    the calculation unit specifies a first region of the Nyquist diagram corresponding to the first portion and a second region of the Nyquist diagram corresponding to the second portion,
    the calculation unit, when a portion of the Nyquist diagram corresponding to the first region or the second region is missing, complements the Nyquist diagram by estimating the missing portion;
    The calculation unit estimates an internal resistance of the battery using the first region on the Nyquist diagram in which the loss is complemented,
    The battery diagnostic device according to claim 2 , wherein the calculation unit estimates the deterioration state of the battery by using the second region on the Nyquist diagram in which the missing portion is complemented.
  9. 　前記演算部は、前記第１部分と前記電池の内部抵抗との間の第１対応関係を特定し、
    　前記演算部は、前記第１部分を用いて前記第１対応関係を参照することにより、前記電池の内部抵抗を推定する
    　ことを特徴とする請求項８記載の電池診断装置。     The calculation unit determines a first correspondence relationship between the first portion and an internal resistance of the battery;
    The battery diagnostic device according to claim 8 , wherein the calculation unit estimates the internal resistance of the battery by referring to the first correspondence relationship using the first portion.
  10. 　前記演算部は、前記第２部分と前記電池の劣化状態との間の第２対応関係を特定し、
    　前記演算部は、前記第２部分を用いて前記第２対応関係を参照することにより、前記電池の劣化状態を推定する
    　ことを特徴とする請求項８記載の電池診断装置。     The calculation unit determines a second correspondence relationship between the second portion and a degradation state of the battery;
    The battery diagnostic device according to claim 8 , wherein the calculation unit estimates the deterioration state of the battery by referring to the second correspondence relationship using the second portion.
  11. 　前記変化分は、前記電池が備える内部抵抗によって主に生じる第１部分と、前記電池が備える負極によって主に生じる第２部分と、前記電池が備える正極によって主に生じる第３部分とを有し、
    　前記演算部は、前記ナイキスト線図のうち前記第１部分に対応する第１領域と、前記ナイキスト線図のうち前記第２部分に対応する第２領域と、前記ナイキスト線図のうち前記第３部分に対応する第３領域とをそれぞれ特定し、
    　前記演算部は、前記ナイキスト線図上の前記第１領域を用いて前記電池の内部抵抗を推定し、
    　前記演算部は、前記変化分のうち前記第２領域に対応する部分と、前記変化分のうち前記第３領域に対応する部分との間の比率が所定範囲内であるか否かによって、前記電池が正常であるか否かを推定する
    　ことを特徴とする請求項２記載の電池診断装置。     the change has a first portion mainly caused by an internal resistance of the battery, a second portion mainly caused by a negative electrode of the battery, and a third portion mainly caused by a positive electrode of the battery,
    the calculation unit identifies a first region of the Nyquist diagram corresponding to the first portion, a second region of the Nyquist diagram corresponding to the second portion, and a third region of the Nyquist diagram corresponding to the third portion,
    The calculation unit estimates an internal resistance of the battery using the first region on the Nyquist diagram;
    3. The battery diagnostic device according to claim 2, wherein the calculation unit estimates whether the battery is normal or not based on whether a ratio between a portion of the change corresponding to the second region and a portion of the change corresponding to the third region is within a predetermined range.
  12. 　前記演算部は、前記第１関係のうち前記位相が一定値に収束している第１箇所と、前記第１関係のうち前記対象範囲の上限に対応する第２箇所とをそれぞれ特定し、
    　前記演算部は、前記特定した前記第１箇所と前記第２箇所にしたがって、前記ナイキスト線図上における前記第３領域を特定する
    　ことを特徴とする請求項１１記載の電池診断装置。     the calculation unit identifies a first point in the first relationship where the phase converges to a constant value and a second point in the first relationship that corresponds to an upper limit of the target range,
    The battery diagnostic device according to claim 11 , wherein the calculation unit identifies the third region on the Nyquist diagram in accordance with the identified first location and the identified second location.
  13. 　前記比率が前記所定範囲内である場合、
    　　前記演算部は、前記第１部分と前記電池の内部抵抗との間の第１対応関係を特定し、
    　　前記演算部は、前記第１部分を用いて前記第１対応関係を参照することにより、前記電池の内部抵抗を推定し、
    　　前記演算部は、前記第２部分と前記電池の劣化状態との間の第２対応関係を特定し、
    　　前記演算部は、前記第２部分を用いて前記第２対応関係を参照することにより、前記電池の劣化状態を推定する
    　ことを特徴とする請求項１１記載の電池診断装置。     If the ratio is within the predetermined range,
    The calculation unit determines a first correspondence relationship between the first portion and an internal resistance of the battery;
    The calculation unit estimates an internal resistance of the battery by referring to the first correspondence relationship using the first portion;
    The calculation unit determines a second correspondence relationship between the second portion and a degradation state of the battery;
    The battery diagnostic device according to claim 11 , wherein the calculation unit estimates the deterioration state of the battery by referring to the second correspondence relationship using the second portion.
  14. 　前記電池は、コンタクタを介して充電器または放電先負荷と接続されるように構成されており、
    　前記第１期間の終了時刻は、前記コンタクタがＯＦＦされる時刻またはそれ以前である
    　ことを特徴とする請求項１記載の電池診断装置。     The battery is configured to be connected to a charger or a load via a contactor;
    2. The battery diagnostic device according to claim 1, wherein the end time of the first period is a time when the contactor is turned off or before that time.
  15. 　前記演算部は、ユーザインターフェースを生成し、
    　前記ユーザインターフェースは、
    　　前記第１期間の開始時刻と終了時刻、
    　　前記変化分、
    　　前記推定した前記電池の状態、
    　のうち少なくともいずれかを提示する
    　ことを特徴とする請求項１記載の電池診断装置。     The computing unit generates a user interface;
    The user interface includes:
    The start and end times of the first period;
    The change amount,
    the estimated state of the battery;
    The battery diagnostic device according to claim 1, characterized in that it presents at least one of the following:
  16. 　前記休止期間は、前記休止期間の開始時刻から、前記電池の電流が０になるまでの、第２期間を有しており、
    　前記第１期間の開始時刻は、前記休止期間の開始時刻から前記第２期間の時間長の２倍が経過した以降であり、
    　前記第１期間の終了時刻は、前記休止期間の開始時刻から０．１秒が経過した以降であり、
    　前記第１期間の時間長は、２ｍ秒以上１００ｍ秒未満である
    　ことを特徴とする請求項１記載の電池診断装置。     the rest period has a second period from a start time of the rest period to a time when the current of the battery becomes zero,
    the start time of the first period is after twice the time length of the second period has elapsed from the start time of the idle period,
    the end time of the first period is 0.1 seconds or later from the start time of the idle period,
    The battery diagnostic device according to claim 1 , wherein a time length of the first period is equal to or longer than 2 ms and shorter than 100 ms.
  17. 　電池の状態を診断する電池診断方法であって、
    　前記電池が出力する電圧の検出値を取得するステップ、
    　前記電池の状態を推定するステップ、
    　を有し、
    　前記推定するステップにおいては、前記電池が充電動作または放電動作を終了したあとの休止期間における第１期間を特定し、
    　前記推定するステップにおいては、前記第１期間における前記電圧の変化分を、周波数成分と位相成分に変換し、
    　前記推定するステップにおいては、前記変換によって得られる前記位相成分のうち所定範囲内にあるものを特定するとともに、その特定した前記位相成分に対応する時間範囲における前記変化分を対象範囲として特定し、
    　前記推定するステップにおいては、前記対象範囲における前記変化分を用いて、前記電池の状態を推定する
    　ことを特徴とする電池診断方法。     A battery diagnostic method for diagnosing a battery state, comprising:
    obtaining a detection value of a voltage output by the battery;
    estimating a state of the battery;
    having
    In the step of estimating, a first period in a pause period after the battery has finished a charging operation or a discharging operation is identified;
    In the estimating step, a change in the voltage during the first period is converted into a frequency component and a phase component;
    In the estimating step, among the phase components obtained by the conversion, those within a predetermined range are identified, and the change in the time range corresponding to the identified phase components is identified as a target range;
    the estimating step estimates the state of the battery using the change in the target range.
  18. 　電池の状態を診断する電池診断装置であって、
    　前記電池が出力する電圧の検出値を取得する検知部、
    　前記電池の状態を推定する演算部、
    　を備え、
    　前記演算部は、前記電池が充電動作または放電動作を終了したあとの休止期間における第１期間を特定し、
    　前記演算部は、前記第１期間における前記電圧の変化分を用いて、前記電池の状態を推定し、
    　前記休止期間は、前記休止期間の開始時刻から、前記電池の電流が０になるまでの、第２期間を有しており、
    　前記第１期間の開始時刻は、前記休止期間の開始時刻から前記第２期間の時間長の２倍が経過した以降であり、
    　前記第１期間の終了時刻は、前記休止期間の開始時刻から０．１秒が経過した以降であり、
    　前記第１期間の時間長は、２ｍ秒以上１００ｍ秒未満である
    　ことを特徴とする電池診断装置。     A battery diagnostic device for diagnosing a state of a battery, comprising:
    a detection unit that acquires a detection value of a voltage output by the battery;
    A calculation unit that estimates the state of the battery;
    Equipped with
    The calculation unit identifies a first period in a pause period after the battery has finished a charging operation or a discharging operation,
    The calculation unit estimates a state of the battery using the change in the voltage during the first period;
    the rest period has a second period from a start time of the rest period to a time when the current of the battery becomes zero,
    the start time of the first period is after twice the time length of the second period has elapsed from the start time of the idle period,
    the end time of the first period is 0.1 seconds or later from the start time of the idle period,
    a time length of the first period is equal to or greater than 2 ms and less than 100 ms.
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