Impedance detection device and impedance detection method

Abstract

An impedance detection device (60) is provided with: an acquisition unit (61) that acquires measurement data of at least one of a current and a voltage at I times in a transient response when a predetermined current or a predetermined voltage is supplied to a secondary battery; and a calculation unit (60b) that calculates the internal impedance on the basis of the measurement data of the current and / or the voltage. The calculation unit (60b) has: a first calculation unit (62) that calculates I impedance data using measurement data of at least one of a voltage and a current; and a second calculation unit (60a) that calculates element parameters of the equivalent circuit model of the secondary battery on the basis of I impedance data and an Mth-order equation obtained from the equivalent circuit model, the Mth-order equation representing the internal impedance using a linear sum of a plurality of terms, the Mth-order equation being an equation based on a theoretical value corresponding to a predetermined current or a predetermined voltage.

Description

Technical Field

[0001] The present disclosure relates to an impedance detection device and an impedance detection method. Background Art

[0002] Applications using secondary batteries such as electric vehicles and storage batteries have increased rapidly. For example, a lithium-ion battery (LiB) is used as the secondary battery. In such a LiB, in order to manage and grasp the performance (deterioration grasp), it is desired to accurately estimate battery state indicators such as the SOH (State of Health), SOP (State Of Power), and SOC (State of Charge) of a battery cell. As a method for estimating such battery state indicators, a method is known in which component parameters (equivalent circuit constants) of an equivalent circuit model of a battery cell are estimated, and the estimated component parameters are used to estimate the battery state indicators. In Patent Document 1, a system for producing a Nyquist plot based on the impedance at each frequency and estimating component parameters based on the produced Nyquist plot is disclosed.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 6226261 Gazette Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, in the technique of Patent Document 1, there is a problem that component parameters cannot be accurately estimated due to the influence of the inductive component inside the secondary battery.

[0008] Therefore, the present disclosure provides an impedance detection device and an impedance detection method capable of estimating component parameters of an equivalent circuit model of a secondary battery with better accuracy than before.

[0009] Means for Solving the Problems

[0010] An impedance detection device according to an aspect of the present disclosure is an impedance detection device that detects the internal impedance of a secondary battery, and includes: an acquisition unit that acquires at least one of current measurement data and voltage measurement data at I (I is a natural number of 2 or more) moments in the transient response of the secondary battery when a predetermined current or a predetermined voltage is supplied to the secondary battery; and a calculation unit that calculates the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data. The calculation unit includes: a first calculation unit that calculates the I impedance data using at least one of the voltage measurement data and the current measurement data; and a second calculation unit that calculates element parameters of the equivalent circuit model of the secondary battery based on an M (M is a natural number of 2 or more) -th order equation obtained from the equivalent circuit model of the secondary battery and the I impedance data. The M -th order equation represents the internal impedance of the secondary battery as a linear sum of a plurality of terms, and the M -th order equation is an equation based on a theoretical value of the transient response of the internal impedance corresponding to the predetermined current or the predetermined voltage.

[0011] An impedance detection method according to an aspect of the present disclosure is an impedance detection method that detects the internal impedance of a secondary battery, and includes: an acquisition step of acquiring at least one of current measurement data and voltage measurement data at I (I is a natural number of 2 or more) moments in the pulse response of the secondary battery when a predetermined current or a predetermined voltage is supplied to the secondary battery; and a calculation step of calculating the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data. In the calculation step, at least one of the voltage measurement data and the current measurement data is used to calculate the I impedance data, and element parameters of the equivalent circuit model of the secondary battery are calculated based on an M (M is a natural number of 2 or more) -th order equation obtained from the equivalent circuit model of the secondary battery and the I impedance data. The M -th order equation represents the internal impedance of the secondary battery as a linear sum of a plurality of terms, and the M -th order equation is an equation based on a theoretical value of the transient response of the internal impedance corresponding to the predetermined current or the predetermined voltage.

[0012] Effect of the Invention

[0013] According to an impedance detection device or the like according to an aspect of the present disclosure, it is possible to estimate element parameters of an equivalent circuit model of a secondary battery with better accuracy than in the past. Description of the Drawings

[0014] Figure 1 It is a diagram showing a schematic configuration of an impedance detection system according to Embodiment 1.

[0015] Figure 2It is a diagram showing an equivalent circuit model of a battery cell including internal impedance according to Embodiment 1.

[0016] Figure 3 It is a diagram showing a circuit in which the electrode surface component in the internal impedance according to Embodiment 1 is replaced with a series connection of a plurality of parallel RC circuits.

[0017] Figure 4 It is a block diagram showing the functional structure of the impedance detection device according to Embodiment 1.

[0018] Figure 5 It is a flowchart showing the operation of the impedance detection device according to Embodiment 1.

[0019] Figure 6 It is a diagram schematically showing the shapes of the input current input to the battery cell and the output voltage output from the battery cell according to Embodiment 2.

[0020] Figure 7 It is a flowchart showing the operation of the impedance detection device according to Embodiment 2.

[0021] Figure 8 It is a diagram showing the battery characteristics of the battery cell for verification.

[0022] Figure 9A It is a diagram showing various measurement data of the first battery cell.

[0023] Figure 9B It is a diagram showing various measurement data of the second battery cell.

[0024] Figure 10A It is a diagram showing the estimation result of the internal parameter (series resistance R0) in the impedance detection device of the present disclosure.

[0025] Figure 10B It is a diagram showing the internal parameter (series connection value C tot ) in the impedance detection device of the present disclosure.

[0026] Figure 11A It is a diagram showing a first example of the measurement data of the input current and the output voltage of the first battery cell measured by the method of the prior art example.

[0027] Figure 11B It is a diagram showing a second example of the measurement data of the input current and the output voltage of the first battery cell measured by the method of the prior art example.

[0028] Figure 11C It is a diagram showing a third example of the measurement data of the input current and the output voltage of the first battery cell measured by the method of the prior art example.

[0029] Figure 12AIt is a diagram showing the Nyquist diagram of the first battery cell obtained by the method of the existing example.

[0030] Figure 12B It is a diagram showing the Nyquist diagram of the second battery cell obtained by the method of the existing example. Detailed implementation mode

[0031] An impedance detection device according to one aspect of the present disclosure is an impedance detection device that detects the internal impedance of a secondary battery, and includes: an acquisition unit that acquires at least one of current measurement data and voltage measurement data at I (I is a natural number of 2 or more) moments in the transient response of the secondary battery when a predetermined current or a predetermined voltage is supplied to the secondary battery; and a calculation unit that calculates the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data. The calculation unit includes: a first calculation unit that calculates the I impedance data using at least one of the voltage measurement data and the current measurement data; a second calculation unit that calculates element parameters of the equivalent circuit model of the secondary battery based on an M (M is a natural number of 2 or more) -th order equation obtained from the equivalent circuit model of the secondary battery and the I impedance data. The M -th order equation represents the internal impedance of the secondary battery as a linear sum of multiple terms, and the M -th order equation is an equation based on the theoretical value of the transient response of the internal impedance corresponding to the predetermined current or the predetermined voltage.

[0032] Thus, the impedance detection device can calculate the element parameters without using the Nyquist diagram, and thus can calculate the element parameters with almost no influence from the inductive reactance of the secondary battery. Therefore, an impedance detection device according to one aspect of the present disclosure can estimate the element parameters of the equivalent circuit model of the secondary battery with better accuracy than in the past.

[0033] In addition, for example, the predetermined current or the predetermined voltage may be a pulse current or a pulse voltage.

[0034] Thus, by using the pulse response as the transient response, the element parameters of the equivalent circuit model of the secondary battery can be estimated with better accuracy than in the past.

[0035] In addition, for example, the second calculation unit may be configured to set the I impedance data equal to the M -th order equation and calculate the element parameters.

[0036] Thus, by substituting the I impedance data into the M -th order equation, the element parameters can be calculated. Since the impedance data of the impedance detection device substantially does not include an inductive component, the element parameters of the equivalent circuit model of the secondary battery can be estimated with better accuracy than in the past.

[0037] Alternatively, for example, the M-th order equation may include a plurality of terms obtained by expanding the theoretical value of the transient response of the internal impedance of the secondary battery obtained from the equivalent circuit model of the secondary battery with respect to time. The plurality of terms include (M + 1) coefficients. The second calculation unit sets the I impedance data equal to the M-th order equation, calculates the (M + 1) coefficients respectively, and calculates the element parameters based on the calculated (M + 1) coefficients.

[0038] Thus, the impedance detection device calculates the (M + 1) coefficients of the M-th order equation, and thus can calculate the element parameters without using a Nyquist plot.

[0039] Alternatively, for example, the number of the I may be more than the number of the (M + 1), and the (M + 1) coefficients are calculated by the least squares method.

[0040] Thus, the impedance detection device can easily perform the calculation for calculating the (M + 1) coefficients.

[0041] Alternatively, for example, the equivalent circuit model of the secondary battery has a structure in which one or more capacitors and a parallel circuit of resistors are connected in series to a series resistor, and the second calculation unit calculates at least the series resistor as the element parameter of the secondary battery.

[0042] Thus, the impedance detection device can accurately estimate the series resistor as an element parameter.

[0043] Alternatively, for example, the equivalent circuit model of the secondary battery has a structure in which one or more capacitors and a parallel circuit of resistors are connected in series to a series resistor, and the second calculation unit calculates the total value of the capacitors in at least one or more of the parallel circuits as the element parameter of the secondary battery.

[0044] Thus, the impedance detection device can accurately estimate the total value of the capacitors as an element parameter.

[0045] Alternatively, for example, the acquisition unit acquires the current measurement data and the voltage measurement data respectively, and the first calculation unit calculates the I impedance data by dividing the I voltage measurement data by the corresponding I current measurement data at the same time.

[0046] Thus, since the voltage measurement data and the current measurement data are used, more accurate impedance data can be calculated. Therefore, the impedance detection device can use more accurate impedance data to estimate the element parameters, and thus can estimate the element parameters with better accuracy.

[0047] In addition, an impedance detection method according to one aspect of the present disclosure is an impedance detection method for detecting the internal impedance of a secondary battery, including: an acquisition step of acquiring at least one of current measurement data and voltage measurement data at I (I is a natural number of 2 or more) moments in the pulse response of the secondary battery when a predetermined current or a predetermined voltage is supplied to the secondary battery; and a calculation step of calculating the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data. In the calculation step, at least one of the voltage measurement data and the current measurement data is used to calculate the I impedance data, and based on an M (M is a natural number of 2 or more) -th order equation obtained from an equivalent circuit model of the secondary battery and the I impedance data, element parameters of the equivalent circuit model of the secondary battery are calculated. The M -th order equation represents the internal impedance of the secondary battery as a linear sum of a plurality of terms, and the M -th order equation is an equation based on a theoretical value of the transient response of the internal impedance corresponding to the predetermined current or the predetermined voltage.

[0048] Accordingly, the same effects as those of the above-described impedance detection device are achieved.

[0049] In addition, these general or specific aspects can be implemented by a system, a method, an integrated circuit, a computer program, or a non - transitory recording medium such as a computer - readable CD - ROM, or can be implemented by any combination of a system, a method, an integrated circuit, a computer program, or a recording medium. The program can be pre - stored in the recording medium or can be supplied to the recording medium via a wide - area communication network including the Internet and the like.

[0050] Hereinafter, each embodiment and the like will be specifically described with reference to the drawings.

[0051] In addition, each of the embodiments described below represents a general or specific example. The numerical values, constituent elements, arrangement positions and connection forms of the constituent elements, steps, order of steps, etc. shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, with respect to the constituent elements in the following embodiments and the like that are not described in the independent claims, they are described as optional constituent elements.

[0052] In addition, each figure is a schematic diagram and is not necessarily drawn strictly. Therefore, for example, the scales and the like in each figure are not necessarily the same. In addition, in each figure, the same reference numerals are given to substantially the same structures, and repeated explanations are omitted or simplified.

[0053] In addition, in this specification, relational terms such as equality and the like, as well as numerical values and numerical ranges, do not represent expressions with only a strict meaning, but mean substantially equivalent ranges, for example, expressions that also include differences of about several percent (for example, about 10%).

[0054] In addition, in this specification, unless otherwise specified, ordinal numbers such as "first" and "second" do not mean the number or order of components, but are used for the purpose of avoiding confusion and distinguishing between the same components.

[0055] (Embodiment 1)

[0056] Hereinafter, with reference to Figures 1 to 5 An impedance detection system including the impedance detection device according to this embodiment will be described.

[0057] [1-1. Structure of Impedance Detection System]

[0058] First, with reference to Figure 1 The structure of the impedance detection system according to this embodiment will be described. Figure 1 is a diagram showing a schematic structure of the impedance detection system 1 according to this embodiment. The impedance detection system 1 according to this embodiment can be mounted on various application devices such as electric vehicles (EV: Electric Vehicle) and industrial machinery.

[0059] As Figure 1 shown, the impedance detection system 1 includes a battery charger 10, a battery pack 20, a voltage measurement device 30, a shunt resistor 40, a current measurement device 50, and an impedance detection device 60. The battery charger 10, the battery pack 20, and the shunt resistor 40 are connected in series. That is, a series circuit is formed by the battery charger 10, the battery pack 20, and the shunt resistor 40. In addition, a measurement circuit is constituted by the battery charger 10, the voltage measurement device 30, the shunt resistor 40, and the current measurement device 50, and this measurement circuit supplies a pulse current or a pulse voltage to the secondary battery and holds the current measurement data and the voltage measurement data at I (I is a natural number of 2 or more) moments during the pulse response of the secondary battery.

[0060] The battery charger 10 is a power source for supplying a pulse current or a pulse voltage to the battery pack 20. In this embodiment, the battery charger 10 supplies a pulse current for charging or discharging to the battery pack 20. When the battery charger 10 supplies a pulse current, voltage data of each of the plurality of battery cells 21 of the battery pack 20 is obtained as measurement data.

[0061] In addition, in this embodiment, it is assumed that the rise time and the fall time of the pulse current are 0 seconds. Hereinafter, the pulse current will also be referred to as an input current. In addition, the rise time and the fall time will also be referred to as the pulse rise time and the pulse fall time.

[0062] The battery pack 20 is composed of a plurality of battery cells 21 connected in series or in parallel. In the present embodiment, the battery pack 20 is composed of a plurality of battery cells 21 connected in series. The plurality of battery cells 21 are secondary batteries respectively, for example, lithium-ion batteries, but may also be other secondary batteries such as nickel-metal hydride batteries. The battery pack 20 functions as a power source and supplies power to a load. When the impedance detection system 1 is mounted on an EV, the load is, for example, the motor of the EV, but is not particularly limited.

[0063] Both ends of each of the plurality of battery cells 21 are connected to a voltage measuring device 30 via a plurality of voltage detection lines.

[0064] Here, with reference to Figure 2 and Figure 3 an equivalent circuit model of the battery cell 21 will be described. Figure 2 is a diagram showing an equivalent circuit model of the battery cell 21 including the internal impedance according to the present embodiment. The battery cell 21 includes a positive electrode, a negative electrode, and an electrolyte.

[0065] As Figure 2 shown, the equivalent circuit model of the battery cell 21 is formed by an open-circuit voltage V OCV , an inductive component, and an internal impedance. In addition, the inductive component may also be included in the internal impedance. Further, the internal impedance is formed by an electrolyte component due to the electrolyte, an electrode surface component due to the electrode surface, and an active material component due to the active material.

[0066] The open-circuit voltage V OCV is the voltage of the battery cell 21 when the battery cell 21 is not energized, and is, for example, the voltage of a voltage source that becomes DC (Direct Current).

[0067] The inductive component is formed by an inductive reactance L and a resistance R L due to the internal impedance of the battery cell 21. The time constant based on the inductive reactance L and the resistance R L is, for example, 1 [μsec] or less. In addition, the width of the above-mentioned pulse current (the time width for supplying one pulse current) is sufficiently longer than the time constant based on the inductive reactance L and the resistance R L .

[0068] The electrolyte component is the impedance caused by the electrolyte itself of the battery cell 21 and is the main component of the series resistance R0. When the lithium ions decrease due to the deterioration of the battery cell 21, the series resistance R0 increases.

[0069] The electrode surface component is the impedance caused by the surfaces of the positive electrode and the negative electrode, and is represented by a C dl expressed by a so-called CPE (Constant Phase Element) and a resistance Rct is a parallel circuit representation. CPE is a hypothetical element used to represent the behavior of the electrolyte of the battery cell 21, and its impedance Z CPE is represented by Equation 1 below. Here, Q in Equation 1 is a constant equivalent to the capacitance of a normal capacitor, and α is a constant taking any small value between 0 and 1.

[0070] [Mathematical formula 1]

[0071]

[0072] The time constant of the impedance caused by the electrode surface is several msec.

[0073] The active material (diffusion) component is the impedance caused by the inside of the positive electrode and the negative electrode, and is the so-called eddy current impedance Z W . The time constant of the impedance caused by the active material is several seconds or more, which is extremely large compared to the transient response time span concerned in the impedance detection system 1. Therefore, the influence on the estimation of the internal impedance of the present disclosure is extremely small, and thus the description of the active material is omitted in the following description.

[0074] Thus, in the present embodiment, it is considered that the internal impedance is composed of an electrolyte component and an electrode surface component. In addition, for mathematical analysis, the electrode surface component is mostly represented by a serial connection of multiple RC parallel circuits. Refer to Figure 3 to illustrate an example of the serial connection of multiple RC parallel circuits. Figure 3 is a diagram showing a circuit in which the electrode surface component in the internal impedance of the present embodiment is replaced by a serial connection of multiple RC parallel circuits. Figure 3 (a) is a diagram showing the circuit before being replaced by a serial connection of multiple RC parallel circuits, Figure 3 (b) is a diagram showing the circuit after being replaced by a serial connection of multiple RC parallel circuits.

[0075] As Figure 3 (a) and (b) show, as an example, the C dl and the resistor R ct of one parallel circuit represented by the CPE representing the electrode surface component are represented by a serial connection of four RC parallel circuits. The four RC parallel circuits include a parallel circuit of capacitor C1 and resistor R1, a parallel circuit of capacitor C2 and resistor R2, a parallel circuit of capacitor C3 and resistor R3, and a parallel circuit of capacitor C4 and resistor R4. In addition, the total capacitor of capacitors C1 to C4 is also recorded as the serial connection value C tot . The serial connection value C tot means the total value of the capacitors in at least one or more parallel circuits of capacitors and resistors.

[0076] In addition, the number of serially connected RC parallel circuits is an example and is appropriately determined according to the type of the battery cell 21 or the like. One or more serially connected RC parallel circuits are sufficient. In this way, the equivalent circuit model of the battery cell 21 has a structure in which one or more parallel circuits of a capacitor and a resistor are serially connected to the series resistor R0. For example, it may have a structure in which two or more parallel circuits of a capacitor and a resistor are serially connected to the series resistor R0.

[0077] Referring again to Figure 1 , the number of the plurality of battery cells 21 included in the battery pack 20 and the voltage of each of the plurality of battery cells 21 are not particularly limited. Each of the plurality of battery cells 21 may be, for example, a battery cell of the same specification.

[0078] The voltage measurement device 30 measures the voltage of the battery pack 20. The voltage measurement device 30 is configured to be able to measure the voltage of each of the plurality of battery cells 21 separately. The voltage measurement device 30 may also be configured to include an IC (Integrated Circuit) for measuring the voltage of the battery cell 21.

[0079] Thereby, even when the overall voltage of the battery pack 20 is too high for direct measurement, the voltage can be measured, and in addition, the operations of the plurality of battery cells 21 can be determined separately. The voltage measurement device 30 measures the voltages of the plurality of battery cells 21 in sequence (in time series), for example.

[0080] The shunt resistor 40 is a current detection resistor for detecting the current flowing through the above series circuit. The shunt resistor 40 is serially connected to the battery pack 20. The shunt resistor 40 is connected between the negative electrode side of the battery pack 20 (for example, the negative electrode of the battery cell 21) and the battery charger 10. The resistance value of the shunt resistor 40 is not particularly limited.

[0081] The current measurement device 50 detects the current flowing in the battery pack 20. The current measurement device 50 is a resistance detection type current sensor using the shunt resistor 40, but may also be a magnetic field detection type current sensor. The current measurement device 50 may also be configured to include an IC for current measurement.

[0082] The impedance detection device 60 detects the internal impedance of the secondary battery. In the present embodiment, the impedance detection device 60 detects the internal impedance of at least one of each of the plurality of battery cells 21 and the battery pack 20 as a whole based on the voltage measurement data from the voltage measurement device 30 and the current measurement data from the current measurement device 50.

[0083] The impedance detection device 60 does not use the method of estimating component parameters based on the Nyquist diagram described in the above-mentioned Patent Document 1, but uses an estimation based on impulse response to estimate the component parameters of the equivalent circuit model of the battery cell 21, which will be described in detail later. In the method of estimating component parameters based on the Nyquist diagram, there is a case where the estimation accuracy of component parameters is reduced due to the influence of the inductive component. However, since the impedance detection device 60 uses an estimation based on impulse response, it is not easily affected by the inductive component and can estimate component parameters with good accuracy.

[0084] In addition, the estimation based on impulse response is to input a pulsed current (or voltage) to the battery cell 21 and measure the input current (or input voltage) and the offset voltage offset from the open-circuit voltage V of the battery cell 21. OCV The estimation based on impulse response can also be said to be an estimation method of estimating the component parameters of the equivalent circuit model of the battery cell 21 according to the transient response shape of the IR drop of the internal impedance of the battery cell 21.

[0085] In addition, hereinafter, an example in which the impedance detection device 60 is similarly mounted on an EV together with other components of the impedance detection system 1 will be described, but it is not limited thereto, and it may be separately provided from other components. For example, the impedance detection device 60 may be composed of a server device or the like connected to the EV in a communicable manner.

[0086] Figure 4 is a block diagram showing the functional structure of the impedance detection device 60 of the present embodiment. The impedance detection device 60 can be implemented by an MPU (Micro Processor Unit), a memory, and the like. In addition, the processing of each functional block of the impedance detection device 60 is usually realized by a program execution unit such as a processor reading and executing software (program) recorded in a recording medium such as a ROM.

[0087] As Figure 4 shown, the impedance detection device 60 includes an acquisition unit 61, a first calculation unit 62, an expansion unit 63, a formula column unit 64, a coefficient estimation unit 65, and a parameter estimation unit 66. In addition, a second calculation unit 60a is constituted by including the coefficient estimation unit 65 and the parameter estimation unit 66, and a calculation unit 60b is constituted by the first calculation unit 62 and the second calculation unit 60a. The calculation unit 60b calculates the internal impedance of the battery cell 21 based on the current measurement data and the voltage measurement data.

[0088] The acquisition unit 61 is an interface (e.g., a hardware interface) that acquires current measurement data and voltage measurement data at I (where I is a natural number of 2 or more) moments during the pulse response of the battery pack 20 when a pulse current or a pulse voltage is supplied to the battery pack 20. The acquisition unit 61 acquires the current measurement data flowing in the battery pack 20 and the voltage measurement data of each of the plurality of battery cells 21. The acquisition unit 61 can acquire the current measurement data and the voltage measurement data through wired communication (e.g., communication via wiring formed on a substrate), or can also acquire the current measurement data and the voltage measurement data through wireless communication.

[0089] The first calculation unit 62 detects the rising or falling moment of the input current or the input voltage, and divides the voltage measurement data after the rising or falling moment by the current measurement data to calculate I impedance data. The voltage measurement data and the current measurement data are time series data including at least the measurement data at I moments, and the first calculation unit 62 performs a division operation on the voltage measurement data and the current measurement data at the same moment. In addition, I represents the number of points (measurement points) of the moments for performing the measurement for estimating the equivalent circuit parameters. In addition, the number of each of the voltage measurement data and the current measurement data acquired by the acquisition unit 61 also includes the data for detecting the rising or falling moment of the input current or the input voltage, and thus is more than I.

[0090] In addition, in the case of supplying a pulse current to the battery pack 20, when calculating the above I impedance data, the I voltage measurement data can be respectively divided by the average current calculated based on the I current measurement data, or when the expected peak value of the pulse current is known, it can also be divided by the expected peak value to calculate. Similarly, in the case of supplying a pulse voltage to the battery pack 20, when calculating the above I impedance data, when the average voltage calculated based on the I voltage measurement data or the expected peak value of the pulse voltage is known, the expected peak value can also be respectively divided by the I current measurement data to calculate. In addition, in the impedance data, for example, there is substantially no inductive component. The voltage measurement data and the current measurement data can also be, for example, data at moments that are not affected or are less affected by the inductive component.

[0091] In addition, regarding the detection of the rising or falling moment of the above input current or input voltage, the moment when the peak value of the pulse is first taken in the time series measurement data of the input current or input voltage can be detected as the rising or falling moment of the input current or input voltage. In addition, other detection methods can also be used. The above peak value can include errors. For example, the moment when the value is within ±5% of the average value or the expected peak value calculated based on the I current measurement data can also be detected as the rising or falling moment of the input current or input voltage.

[0092] The expansion unit 63 is obtained from the equivalent circuit model of the battery cell 21, and approximates the internal impedance of the battery cell 21 as an M (M is a natural number of 2 or more) - order equation (for example, refer to Equation 4 described later). This M - order equation is represented by the linear sum of multiple terms (for example, each term of the polynomial shown in Equation 4 described later). The expansion unit 63 approximates the theoretical value Z(t) of the transient response of the internal impedance of the equivalent circuit model of the battery cell 21 as an M - order equation represented by multiple terms obtained by expanding with respect to the time t (measurement time) (refer to Equation 4 described later). The expansion unit 63 obtains the M - order equation, for example, by performing a power expansion of the theoretical value Z(t) of the transient response with respect to the time t.

[0093] The equation - listing unit 64 lists I simultaneous equations for calculating each coefficient of the M - order equation based on the I impedance data calculated by the first calculation unit 62 and the M - order equation after the power expansion performed by the expansion unit 63.

[0094] The coefficient estimation unit 65 estimates the measurement coefficients that are the coefficients of the M - order equation by solving the I simultaneous equations listed by the equation - listing unit 64.

[0095] The parameter estimation unit 66 estimates the component parameters based on the estimated measurement coefficients of the M - order equation and the theoretical coefficients of the M - order equation (for example, refer to Equation 5 and Equation 6 described later).

[0096] [1 - 2. Operation of the Impedance Detection Device]

[0097] Next, refer to Figure 5 The operation of the impedance detection device 60 configured as described above will be described. Figure 5 is a flowchart showing the operation (impedance detection method) of the impedance detection device 60 of the present embodiment.

[0098] In addition, Figure 5 The timing of executing the steps S10 and S20 and the steps S30 and S40 shown is not particularly limited. They can be executed in parallel, or the steps S30 and S40 can be executed before step S10. Also, Figure 5 The flowchart shown is executed, for example, periodically. However, steps S30 and S40 do not need to be executed every time, and can be executed at least once (for example, only once at the beginning) at an arbitrary timing.

[0099] As Figure 5 shown, the acquisition unit 61 acquires the measurement result of the pulse response of the battery pack 20 (S10). The acquisition unit 61 acquires the current measurement data including I moments and the voltage measurement data of each of the multiple battery cells 21. The acquisition unit 61 outputs the acquired current measurement data and voltage measurement data to the first calculation unit 62.

[0100] In addition, the pulse response of the battery pack 20 is obtained by supplying a pulse current from the battery charger 10 to the battery pack 20. Additionally, each of the I time instants is the time instant during the period when a pulse current is supplied once. Further, in cases where sufficient measurement accuracy cannot be obtained through a single pulse response, etc., multiple pulse responses may be obtained, and for the I relative time instants from the start time of each pulse current, the average of multiple measurement values at the same time instant is taken.

[0101] Next, the first calculation unit 62 divides the voltage measurement data by the current measurement data to calculate the I measurement values Z meas (t i )(impedance data) (S20). The first calculation unit 62 outputs the measurement value Z meas (t i ) calculated for each of the I time instants to the column formation unit 64.

[0102] In addition, the expansion unit 63 obtains the theoretical value Z(t) of the transient response of the equivalent circuit model of the battery cell 21 (S30). Here, the theoretical value Z(t) of the transient response is the theoretical value of the pulse response of the internal impedance of the battery cell 21. The expansion unit 63 may obtain the theoretical value Z(t) of the transient response stored in a storage unit (not shown), or may obtain the theoretical value Z(t) of the transient response via the acquisition unit 61. The theoretical value Z(t) of the transient response after the rise or fall of the input current is represented by the following equation 2. Herein, the time instant of the rise or fall of the input current is set to 0 [sec] in equation 2.

[0103] [Mathematical formula 2]

[0104]

[0105] Among them, ω Cn is represented by the following equation 3. ω Cn represents the reciprocal of the time constant.

[0106] [Mathematical formula 3]

[0107]

[0108] In addition, the input current or input voltage is, for example, a current or voltage in a shape in which the theoretical value Z(t) of the transient response of the internal impedance of the battery cell 21 can be represented by equivalent circuit parameters. The input current (for example, a pulse current) is an example of a prescribed current, and the input voltage (for example, a pulse voltage) is an example of a prescribed voltage.

[0109] Next, the expansion unit 63 performs a power expansion of the theoretical value Z(t) with respect to time t, and replaces the coefficient (determination coefficient) with A m(S40). The expansion unit 63 approximates Equation 2 to an M-th order equation shown in Equation 4 by, for example, Maclaurin expansion. Maclaurin expansion is an example of power expansion.

[0110] [Mathematical formula 4]

[0111]

[0112] Among them, the coefficients A0 and A m are represented by the following Equation 5 and Equation 6.

[0113] [Mathematical formula 5]

[0114] A0 = R0…(Equation 5)

[0115] [Mathematical formula 6]

[0116]

[0117] Equation 5 and Equation 6 are obtained by substituting the coefficients with A m . Equation 5 and Equation 6 show the relationship between the coefficient A m and the component parameters. A0 and A m are an example of M + 1 theoretical coefficients.

[0118] In this way, the M-th order equation is represented by a polynomial obtained by approximating the theoretical value Z(t) of the transient response of the internal impedance of the battery cell 21 obtained from the equivalent circuit model of the battery cell 21 with the power of time t (measurement time). In addition, the M-th order equation can also be said to be an equation obtained by approximating the theoretical impedance obtained from the equivalent circuit model of the battery cell 21 and expanding it at a moment. In addition, the M-th order equation, for example, does not have a reactance component. In addition, the M-th order equation can also be said to be an equation based on the theoretical value Z(t) of the transient response of the internal impedance of the battery cell 21 corresponding to a specified current or a specified voltage.

[0119] In addition, the order M is appropriately selected according to the purpose or the required estimation accuracy. By increasing the order M, the estimation accuracy of the component parameters can be improved. In addition, by reducing the order M, the amount of calculation for estimating the component parameters can be reduced.

[0120] In addition, the method of expanding Equation 2 into an M-th order equation is not limited to Maclaurin expansion, and the power series expansion of other functions can also be used. As the power series expansion of other functions, for example, Taylor expansion, etc. are exemplified.

[0121] Next, the equation-listing unit 64 lists a set of simultaneous equations (S50) by comparing the measured value Z meas (t i ) with the power expansion of t of the theoretical value Z(t). The equation-listing unit 64 is based on the I measured values Z meas (t iThe M-th order equation when the folded part 63 is unfolded, and a set of simultaneous equations is listed. Let Z be the measured value at the same time meas (t i ) is equal to the M-th order equation, then the equation-listing unit 64 lists a plurality of simultaneous equations shown in the following Equation 7.

[0122] [Equation 7]

[0123] Z meas (t1) = A0 + A1·t1 + A2·t1 2 + A3·t1 3 + A4·t1 4 + A5·t1 5 +…

[0124] Z meas (t2) = A0 + A1·t2 + A2·t2 2 + A3·t2 3 + A4·t2 4 + A5·t2 5 +…

[0125] Z meas (t3) = A0 + A1·t3 + A2·t3 2 + A3·t3 3 + A4·t3 4 + A5·t3 5 +……(Equation 7)

[0126] The simultaneous equations shown in Equation 7 are made, for example, I pieces.

[0127] Next, the coefficient estimation unit 65 estimates the coefficient A by solving the I simultaneous equations listed by the equation-listing unit 64 m (S60). The coefficient estimation unit 65 calculates the (M + 1) coefficients A when the measured values Z of the I impedance data meas (t i ) are substituted into the M-th order equation. m . The coefficient A calculated by the simultaneous equations using the measured data in this way m is an example of the measured coefficient.

[0128] Here, the coefficient estimation unit 65 can transform Equation 7 into a matrix form, substitute it with the characters of the following Equations 8, 9, and 10, and thus estimate the coefficient A m .

[0129] [Equation 8]

[0130]

[0131] [Equation 9]

[0132]

[0133] [Mathematical formula 10]

[0134]

[0135] Here, if the number of terms M of the power expansion at time t is less than the number of measurement points I, the coefficient group θ can be estimated by an estimation method such as the least squares method. In the case of estimating the coefficient group θ by the least squares method, it is estimated by the following equation 11.

[0136] [Mathematical formula 11]

[0137]

[0138] Thus, the calculation of the estimated value of the coefficient A m can be easily performed.

[0139] In addition, in the case of estimating θ by the least squares method considering the weight W, it is estimated by the following equation 12.

[0140] [Mathematical formula 12]

[0141]

[0142] Here, the weight matrix (I×I matrix) is represented by the following equation 13.

[0143] [Mathematical formula 13]

[0144]

[0145] In addition, p1, p2,... represent the weights of the measurement points at times t1, t2,... respectively.

[0146] In this way, when the number of measurement points I is more than (M + 1), the coefficient estimation unit 65 can also estimate the coefficient A m .

[0147] Next, the parameter estimation unit 66 performs inverse calculation (S70) on the component parameters of the equivalent circuit model of the (2N + 1) battery cells 21 for R0, R m (m = 0, 1, 2,..., M) of the M + 1 estimated values and equations 5 and 6, ω n , ω Cn (n = 1, 2, 3,..., N). The parameter estimation unit 66 sets the (M + 1) theoretical coefficients equal to the (M + 1) measured coefficients in step S70 and calculates the component parameters.

[0148] As shown in Equation 5, with respect to the estimated value of the series resistance R0, the estimated value of the coefficient A0 can be directly used in any case. Therefore, the parameter estimation unit 66 sets the coefficient A0 as the series resistance R0.

[0149] In addition, in the case where M + 1 ≥ 2N + 1, in principle, R n , ω Cn can also be estimated individually. However, in a system such as a lithium-ion battery, generally, R n with each other and ω Cn with each other mostly have close values and are difficult to separate. Therefore, as an alternative, for parameters other than the series resistance R0 (m = 1, 2,..., M), the following calculation of the value in the form of B in Equation 14 can be performed. m

[0150] [Mathematical formula 14]

[0151]

[0152] In particular, the estimated value of B1 with m = 1 in Equation 14 can be used, and according to the following Equation 15, only the series connection value C of C in the series connection of N RC parallel circuits representing the electrode surface portion can be estimated. tot .

[0153] [Mathematical formula 15]

[0154]

[0155] Thus, the impedance detection device 60 can estimate Figure 3 the series resistance R0 and the series connection value C in the component parameters of the equivalent circuit model of the battery cell 21 shown in (b). tot . In addition, the impedance detection device 60 only needs to estimate at least one of the series resistance R0 and the series connection value C tot . In the case where the equivalent circuit model of the battery cell 21 has a structure in which one or more capacitors and a parallel circuit of resistors are connected in series to the series resistance R0, the impedance detection device 60 can calculate at least the series resistance R0 as the component parameter of the battery cell 21, and calculate the total value of the capacitors in the parallel circuit of one or more capacitors and resistors (series connection value C tot ) as the component parameter of the battery cell 21.

[0156] As described above, the second calculation unit 60a calculates the component parameters of the equivalent circuit model of the battery cell 21 based on (M + 1) theoretical coefficients and I impedance data.

[0157] (Embodiment 2)

[0158] Hereinafter, refer to Figure 6and Figure 7 The impedance detection device of the present embodiment will be described. In addition, hereinafter, the description will focus on the differences from the first embodiment, and the description of the same or similar contents as those in the first embodiment will be omitted or simplified.

[0159] [2-1. Structure of impedance detection system]

[0160] The structure of the impedance detection device of the present embodiment can be the same as that of the impedance detection device 60 in the first embodiment. Hereinafter, the reference numerals of the impedance detection device 60 in the first embodiment will be used for description. Figure 6 It is a diagram schematically showing the shapes of the input current input to the battery cell 21 of the present embodiment and the output voltage output from the battery cell 21. Figure 6 (a) thereof is a diagram showing the input current input to the battery cell 21, Figure 6 (b) thereof is showing Figure 6 a diagram of the output voltage when the input current shown in (a) is input to the battery cell 21.

[0161] As Figure 6 shown in (a), in the present embodiment, the pulse rise time of the input current is not 0. The input current rises from 0 [A] (0%) to Ip [A] (100%) during the period from time t a to time t b . Time t a is the time when the battery charger 10 starts to apply the pulsed current. Time t b is the time when the current reaches Ip. Ip is, for example, the peak value of the pulsed current of the battery charger 10. In addition, the change in the current is represented by a slope D, for example. In addition, the following relationship of Equation 16 holds.

[0162] [Mathematical formula 16]

[0163] D·(t b -t a ) = I p …(Equation 16)

[0164] In addition, in the present embodiment, the pulse fall time of the input current is also not 0.

[0165] In addition, in the first embodiment, in the input current, t a = t b .

[0166] As Figure 6 shown in (b), when the input Figure 6 current shown in (a) is input, the voltage changes from time t a to a time exceeding time t b .

[0167] Thus, in this embodiment, the rise time and fall time of the input current are different from those in Embodiment 1.

[0168] [2-2. Operation of Impedance Detection Device]

[0169] Next, with reference to Figure 7 the operation of the impedance detection device 60 when the input current as described above is input will be described. Figure 7 is a flowchart showing the operation (impedance detection method) of the impedance detection device 60 of this embodiment.

[0170] As Figure 7 shown, the impedance detection method of this embodiment further includes step S110 between steps S10 and S20 shown in Figure 5 .

[0171] After step S10, the first calculation unit 62 calculates times t a , t b (S110). The first calculation unit 62 calculates times t a and t b , for example, based on the time series data of the current measurement data from the current measurement device 50. When the waveform of the input current is unknown, the first calculation unit 62 calculates the slope D and times t a , t b in advance according to the measured value of the current. As the calculation method, a method using the relationship between two measured points between times t a , t b , the least squares method for measuring three or more points, etc. are exemplified, but it is not limited thereto. In addition, times t a , t b are relative times based on a certain time (0 [sec]). For example, it can be based on the start time of obtaining the current measurement data and voltage measurement data, or any one of times t a , t b calculated in step S110.

[0172] Next, in the same manner as in Embodiment 1, the first calculation unit 62 divides the voltage measurement data by the current measurement data to calculate I measured values Z meas (t i )(impedance data) (S20). Then, the first calculation unit 62 outputs the measured value Z meas (t i ) of the calculated impedance data to the column formation unit 64. In addition, the first calculation unit 62 outputs the calculated times t a and t b to the parameter estimation unit 66.

[0173] In addition, the expansion unit 63 obtains the theoretical value Z(t) of the transient response of the equivalent circuit model of the battery cell 21 (S30). The theoretical value Z(t) of the transient response is the theoretical value of the impulse response of the internal impedance of the battery cell 21. At time t b The theoretical value Z(t) of the transient response after that is represented by the following Equation 17.

[0174] [Equation 17]

[0175]

[0176] Next, the expansion unit 63 performs a power expansion of the theoretical value Z(t) of the transient response with respect to t, and replaces the coefficients with A m (S40). The expansion unit 63 obtains Equation 18 and Equation 19, for example, by performing a Maclaurin expansion on Equation 17 and replacing the coefficients with A m

[0177] [Equation 18]

[0178]

[0179] [Equation 19]

[0180]

[0181] The coefficients A0 and A m are an example of M + 1 theoretical coefficients.

[0182] The subsequent processing is the same as that in Embodiment 1.

[0183] Next, the coefficient estimation unit 65 estimates the coefficient A by solving the I simultaneous equations listed by the equation listing unit 64 m (S60). The coefficient estimation unit 65 calculates the (M + 1) coefficients A meas when substituting the I measured values Z i (t m ) into the M-th order equation. The A m calculated here is an example of the measured coefficient.

[0184] Next, the parameter estimation unit 66, based on the M + 1 estimated values of A m (m = 0, 1, 2,..., M), Equation 18 and Equation 19, time t a and t b , performs an inverse operation on the (2N + 1) component parameters of the equivalent circuit model of the battery cell 21 for R0, R n , ω Cn (n = 1, 2, 3,..., N) (S70).

[0185] ​The parameter estimation unit 66 calculates B according to Equation 14 and Equation 19 m , and uses this value to calculate the series resistance R0 according to Equation 18. In addition, the parameter estimation unit 66 uses B1 with m = 1 set in the calculated B m to calculate the series connection value C according to Equation 15 tot .

[0186] In addition, even if the rise time and the fall time are finite values, if they are known numbers, step S110 can also be omitted.

[0187] (Verification result)

[0188] Refer to Figures 8 to 12B to describe the verification results of the estimation accuracy of the internal impedance in the impedance detection device 60 of the above-described embodiments. In the verification, two battery cells 21 (a first battery cell and a second battery cell) having different battery characteristics are used. The first battery cell is a battery cell 21 close to a new product, and the second battery cell is a battery cell 21 in which deterioration has progressed to a certain extent. In addition, as the element parameters of the battery cell 21, element parameters extracted from an actual lithium ion battery (18650 type) are assumed (refer to the following Figure 8 ).

[0189] Figure 8 is a diagram showing the battery characteristics of the battery cell 21 used for verification. The first battery cell and the second battery cell have Figure 8 the battery characteristics shown. Figure 8 The battery characteristics of the first battery cell and the second battery cell shown are values estimated by the AC impedance method.

[0190] Among the element parameters, in order to clarify the difference from Patent Document 1, it also includes the high-frequency inductive component included in the battery cell 21 (for example, a lithium ion battery) ( Figure 8 L and R in L ).

[0191] In addition, the pulse response with limited pulse rise time and fall time of the input current is verified. The pulse rise time and fall time are three types: 10 [μsec], 200 [μsec], and 500 [μsec]. In addition, regarding the theoretical value of the battery internal impedance as imaginary measurement data (imaginary measurement data), the estimation process of the internal parameters of the present disclosure is executed. In the imaginary measurement data shown in the following Figure 9A etc., the high-frequency inductive component included in the battery cell 21 is also considered. For example, the imaginary measurement data is data of a circuit in which the circuit on the electrode surface is replaced with the circuit shown in (b) of Figure 2 in the dotted line box of Figure 3 .

[0192] As an example, in Figure 9A and Figure 9B are shown the hypothetical measurement data of the first battery cell and the second battery cell when the peak input current is set to 1.8 [A], time t a = -200 [μsec], and time t b = 0 [μsec] (rise time 200 [μsec]). Figure 9A is a graph showing various measurement data of the first battery cell. Figure 9B is a graph showing various measurement data of the second battery cell.

[0193] Figure 9A (a) of Figure 9B and (a) of Figure 9A show the time-series data of the input current (current measurement data), with the horizontal axis representing time and the vertical axis representing the current value. Figure 9B The data shown in (a) of

[0194] Figure 9A and (a) of Figure 9B is equivalent to the data obtained from the current measurement device 50. Figure 9A (b) of Figure 9B and (b) of

[0195] Figure 9A show the time-series data of the output voltage (voltage measurement data), with the horizontal axis representing time and the vertical axis representing the voltage value. Figure 9B The data shown in (b) of Figure 9A and (b) of Figure 9B is equivalent to the data obtained from the voltage measurement device 30. Figure 9A (c) of Figure 9A and (c) of Figure 9B show the time-series data of the impedance (internal impedance) (impedance data), with the horizontal axis representing time and the vertical axis representing the impedance. Figure 9B (c) of

[0196] In addition, data after time 0 [sec] is used in the estimation of internal parameters. For example, in the estimation of internal parameters, by using a large amount of data close to time 0 [sec] (e.g., the first half of the width of the pulse current), the estimation accuracy can be improved. The use of a large amount here means that more data in the first half of the width of the pulse current is used than that in the second half of the width of the pulse current. In addition, in the estimation of internal parameters, by using a large amount of data far from time 0 [sec] (e.g., the second half of the width of the pulse current), the influence of noise can be reduced. The use of a large amount here means that more data in the second half of the width of the pulse current is used than that in the first half of the width of the pulse current.

[0197] In addition, time 0 [sec] is the time point when the pulse current supplied to the battery cell 21 reaches the peak value (here 1.8 [A]), for example, corresponding to Figure 6 the time t shown in (a) of b correspondence.

[0198] Next, with reference to Figure 10A and Figure 10B the estimation results in the case of estimating internal parameters using the method of the present disclosure will be described. Figure 10A is a diagram showing the estimation result of the internal impedance (series resistance R0) in the impedance detection device 60 of the present disclosure. Figure 10B is a diagram showing the estimation result of the internal impedance (serial connection value C tot ) in the impedance detection device 60 of the present disclosure.

[0199] In addition, the power expansion is one of three types: quadratic function, quartic function, and sextic function. In addition, the time t i is 120 [μsec], 180 [μsec], 240 [μsec], …, 1020 [μsec], and the sampling interval is 60 [μsec]. That is, the number of measurement points I is sixteen.

[0200] In addition, the estimation method of the coefficient A m in step S60 adopts the weighted least squares method, and in the cases of quadratic function, quartic function, and sextic function, the weights are set to the corresponding power of the reciprocal of time respectively. For example, in the weight matrix shown in Equation 13, in the case of quadratic function, it is set to p i =t i -2 , in the case of quartic function, it is set to p i =t i -4 , and in the case of sextic function, it is set to p i =t i -6 .

[0201] As shown Figure 10A in the figure, the measurement results of the series resistance R0 include items such as the rising / falling slope [μsec], true value, quadratic function, quartic function, and sextic function.

[0202] The rising / falling slope [μsec] is the value of the time (t b - t a ), that is, the rising / falling time, and there are three types: 10 μsec, 200 μsec, and 500 μsec.

[0203] The true value represents the series resistance R0 measured by the AC impedance method.

[0204] The quadratic function, quartic function, and sextic function represent an example of the internal impedance, that is, the estimation result of the series resistance R0, when estimated using functions with the order M of the M-th order equation being 2, 4, and 6.

[0205] As Figure 10B shown, the measurement results of the series connection value C tot include items such as the rising / falling slope [μsec], true value, quadratic function, quartic function, and sextic function.

[0206] The rising / falling slope [μsec] is the value of the time (t b - t a ), and there are three types: 10 μsec, 200 μsec, and 500 μsec.

[0207] The true value represents the series connection value C measured by the AC impedance method tot .

[0208] The quadratic function, quartic function, and sextic function represent an example of the internal impedance, that is, the estimation result of the series connection value C tot when estimated using functions with the order M of the M-th order equation being 2, 4, and 6.

[0209] According to Figure 10A and Figure 10B , it can be seen that both the first battery cell and the second battery cell have the following tendency: the higher the order M of the M-th order equation, the closer the series resistance R0 and the series connection value C tot are to the true value, that is, the estimation accuracy of the series resistance R0 and the series connection value C tot is improved. However, when the order M increases, the amount of calculation also increases. Therefore, the order M can be appropriately determined according to the required accuracy and the amount of calculation demanded by the impedance detection device 60.

[0210] In addition, according to Figure 10A and Figure 10BIt can be seen that by increasing the number of times M, the influence of the difference in the rising / falling slope on the estimation accuracy of the series resistance R0 and the series connection value C tot becomes smaller. For example, when the number of times M is 6, the series resistance R0 and the series connection value C tot are substantially constant regardless of the rising / falling slope.

[0211] In addition, from Figure 10A and Figure 10B it can be seen that the influence of the inductive reactance L and the resistance R in the equivalent circuit model of the battery cell 21 L is hardly seen because the time constant of the inductive reactance L and the resistance R L is smaller than the sampling interval (60 [μsec]).

[0212] Next, with reference to Figures 11A to 12B the estimation results and the like in the case where the internal parameters are estimated by using the method of the existing example will be described. The method of the existing example is a method of estimating element parameters based on the Nyquist diagram as shown in Patent Document 1.

[0213] Figures 11A to 11C is a diagram showing examples of the measurement data of the input current and the output voltage of the first battery cell measured by the method of the existing example. Figures 11A to 11C The rising / falling times are different, Figure 11A the rising / falling time of Figure 11B is 10 [μsec], Figure 11C the rising / falling time of Figure 2 is 200 [μsec], Figure 3 the rising / falling time of

[0214] Figures 11A to 11C is 500 [μsec]. In addition, the sampling interval is 60 [μsec], the number of Fourier transform (FFT) points is 256, and the period of the input current pulse is set to 60 × 256 = 15360 [μsec]. In addition, as the measurement data of the output voltage, the output voltage of the circuit formed by connecting in series the inductive component shown in Figure 2 and the circuit shown in Figure 3 (b) with respect to the theoretical value of the input current is directly used as the imaginary measurement data.

[0214] Figures 11A to 11C (a) shown in Figures 11A to 11C shows the time series data of the input current, the horizontal axis represents time, and the vertical axis represents the current value.

[0215] As Figure 11A shown, when the rising / falling time is extremely short (here it is 10 [μsec]), the curve indicating the rising / falling position is not drawn, and there is uncertainty in the rising / falling position between the sampling intervals.

[0216] In addition, asFigure 11C As shown, in the case where the fall time is extremely long (here 500 [μsec]), it is assumed that the frequency components on the high-frequency side of the input current pulse are extremely small.

[0217] These may be the main reasons for reducing the estimation accuracy of component parameters.

[0218] In addition, although not shown in the figure, the same plotting is also performed for each example of the measured data of the input current and output voltage of the second battery cell.

[0219] Next, referring to Figure 12A and Figure 12B , the results of plotting the Nyquist diagrams of the first battery cell and the second battery cell based on the measured data of the first battery cell shown in Figures 11A to 11C and the measured data of the second battery cell not shown in the figure will be described. Figure 12A is a diagram showing the Nyquist diagram of the first battery cell obtained by the method of the existing example. Figure 12A The (a) of Figure 11A is plotted based on Figure 12A The (b) of Figure 11B is plotted based on Figure 12A The (c) of Figure 11C is plotted based on Figure 12B is a diagram showing the Nyquist diagram of the second battery cell obtained by the method of the existing example. Figure 12A and Figure 12B The curves shown are the values that the Nyquist diagram should have (correct solution data), and the circle diagrams are the points of the Nyquist diagram obtained from the measured data such as Figures 11A to 11C (only sixteen points on the low-frequency side except for DC).

[0220] Figure 12A The (a) of Figure 12B represents the Nyquist diagram in the case where the rise / fall time is 10 [μsec], Figure 12A The (b) of Figure 12B represents the Nyquist diagram in the case where the rise / fall time is 200 [μsec], Figure 12A The (c) of Figure 12B represents the Nyquist diagram in the case where the rise / fall time is 500 [μsec]. In addition, in Figure 12A and Figure 12B , the horizontal axis represents the real part of the AC impedance, and the vertical axis represents the imaginary part of the AC impedance.

[0221] According to Figure 12A and Figure 12B, the Nyquist plot has a deviation according to the rise / fall time. For example, in the case where the rise / fall time is extremely small (here it is 10 [μsec]), as described above, the uncertainty of the rise / fall position occurs, so it is considered that one of the reasons is that the Nyquist plot cannot be accurately depicted. In addition, it is considered that one of the reasons is that in the case where the rise / fall time is extremely large (here it is 500 [μsec]), as described above, the frequency components on the high-frequency side of the input current pulse become extremely small, and the drawing accuracy of the Nyquist plot deteriorates at the points on the high-frequency side.

[0222] In addition, when the sampling interval (for example, 60 [μsec]) is larger than the time constant (for example, 1 [μsec] or less) based on the inductive reactance L and the resistance R in the equivalent circuit model of the battery cell 21 L most of the information on the transient response based on the inductive reactance L and the resistance R cannot be sampled as measured values, and it is difficult to accurately depict the Nyquist plot on the high-frequency side. L

[0223] In addition, by setting the sampling interval to be below the time constant, the information on the transient response based on the inductive reactance L and the resistance R can be obtained, but the sampling interval of currently practical ICs is about 60 [μsec], and it is difficult to implement an IC that operates with a sampling interval below the time constant based on the inductive reactance L and the resistance R. L L

[0224] In this way, in the method of the existing example, it is not easily affected by the rise / fall time, and it is difficult to obtain the information on the transient response based on the inductive reactance L and the resistance R, so it is difficult to accurately depict the Nyquist plot. Moreover, when using such an inaccurate Nyquist plot to estimate the element parameters of the equivalent circuit model of the battery cell 21, it is difficult to accurately estimate the element parameters. L

[0225] On the other hand, as described above, the impedance detection device 60 of the present embodiment can estimate (for example, calculate) the element parameters without using the Nyquist plot, so it can estimate (for example, calculate) the element parameters with almost no influence from the inductive reactance of the battery cell 21. Therefore, the impedance detection device 60 according to one aspect of the present disclosure can estimate the element parameters of the equivalent circuit model of the battery cell 21 with better accuracy than before.

[0226] (Other embodiments)

[0227] As described above, the impedance detection device and the like of one or more embodiments have been described based on the respective embodiments and the like. However, the present disclosure is not limited to these respective embodiments and the like. As long as it does not deviate from the gist of the present disclosure, embodiments obtained by applying various modifications conceived by those skilled in the art to the present embodiment, and embodiments constructed by combining constituent elements in different embodiments can also be included in the present disclosure.

[0228] For example, an example of the impedance detection device in the above-described respective embodiments and the like is a device that detects the impedance of each of a plurality of battery cells in a battery pack. However, it may also be a device that detects the impedance of the entire battery pack by measuring the voltage of the entire battery pack in the voltage measurement device 30.

[0229] In addition, in the above-described respective embodiments and the like, an example in which the impedance detection device includes a deployment unit has been described. However, it is not limited thereto. The impedance detection device may include a storage unit that stores the expanded M-th order equation instead of the deployment unit.

[0230] In addition, in the above-described respective embodiments and the like, an example of using a pulse response has been described. However, for example, a pulse response or a ramp response may also be used to estimate the element parameters. In this case, the theoretical value Z(t) of the transient response of the internal impedance used in (Equation 2) also uses the theoretical value corresponding to the response used. In addition, the pulse current or the ramp current is an example of a specified current, and the pulse voltage or the ramp voltage is an example of a specified voltage.

[0231] In addition, a switch pulse generation device (for example, a pulse generator or the like) may be used instead of the battery charger in the above-described respective embodiments and the like. In addition, a voltage waveform acquisition device (for example, an oscilloscope or the like) may be used instead of at least one of the voltage measurement device and the current measurement device in the above-described respective embodiments and the like. In addition, a computing device (for example, a PC (Personal Computer)) or the like may be used instead of the impedance detection device in the above-described respective embodiments and the like.

[0232] In addition, in the above-described respective embodiments and the like, each constituent element may be configured by dedicated hardware or may be implemented by executing a software program suitable for each constituent element. Each constituent element may be implemented by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

[0233] In addition, the order in which the respective steps in the flowchart are executed is an order illustrated for specifically explaining the present disclosure, and may be an order other than the above. In addition, a part of the above steps may be executed simultaneously (in parallel) with other steps, or a part of the above steps may not be executed.

[0234] In addition, the division of the functional blocks in the block diagram is just an example. Multiple functional blocks can also be implemented as one functional block, or one functional block can be divided into multiple ones, or a part of the function can be transferred to other functional blocks. Additionally, the functions of multiple functional blocks with similar functions can be processed in parallel or time-sharing by a single piece of hardware or software.

[0235] In addition, the impedance detection device in the above-described embodiments and the like can be implemented as a single device or by multiple devices. When the impedance detection device is implemented by multiple devices, the respective components included in the impedance detection device can be distributed to the multiple devices in any manner. For example, the device that executes Figure 5 the steps S10 and S20 shown and the device that executes Figure 5 the steps S30 and S40 shown can also be different devices. When the impedance detection device is implemented by multiple devices, the communication method between the multiple devices is not particularly limited and can be wireless communication or wired communication. Additionally, wireless communication and wired communication can be combined between the devices.

[0236] In addition, the respective components described in the above embodiments and the like can be implemented as software, and typically, can also be implemented as an integrated circuit, i.e., LSI. They can be individually made into a single chip or made into a single chip in a manner that includes a part or all of them. Here, it is assumed to be LSI, but depending on the degree of integration, it is sometimes referred to as IC, system LSI, super large LSI, and ultra large LSI. In addition, the method of integrating into an integrated circuit is not limited to LSI, and can also be implemented by a dedicated circuit (a general circuit that executes a dedicated program) or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconstruct the connection or setting of the circuit units inside the LSI can also be used. Furthermore, with the progress of semiconductor technology or the emergence of other derived technologies, if there appears an integrated circuit technology that can replace LSI, of course, that technology can be used for the integration of the components.

[0237] In addition, one aspect of the present disclosure can also be a computer program that causes a computer to execute Figure 5 and Figure 7 each of the characteristic steps included in the impedance detection method shown in any one of them.

[0238] In addition, for example, the program can also be a program for causing a computer to execute. Additionally, one aspect of the present disclosure can also be a non-transitory computer-readable recording medium storing such a program. For example, such a program can be recorded on a recording medium and distributed or circulated. For example, by installing the distributed program on a device having another processor and causing the processor to execute the program, the device can perform the above-described various processes.

[0239] Industrial Applicability

[0240] The present disclosure is useful in systems for managing batteries and the like.

[0241] Description of Reference Numerals

[0242] 1 Impedance Detection System

[0243] 10 Battery Charger

[0244] 20 Battery Pack

[0245] 21 Battery Cell

[0246] 30 Voltage Measurement Device

[0247] 40 Shunt Resistor

[0248] 50 Current Measurement Device

[0249] 60 Impedance Detection Device

[0250] 60a Second Calculation Unit

[0251] 60b Calculation Unit

[0252] 61 Acquisition Unit

[0253] 62 First Calculation Unit

[0254] 63 Expansion Unit

[0255] 64 Equation Forming Unit

[0256] 65 Coefficient Estimation Unit

[0257] 66 Parameter Estimation Unit

[0258] A0, A m Coefficients (theoretical coefficient, measured coefficient)

[0259] C1, C2, C3, C4 Capacitors

[0260] C dl CPE

[0261] C tot Series Connection Value

[0262] I Number of Measurement Points

[0263] Inductive reactance

[0264] Number of times M

[0265] Series resistance R0

[0266] R1, R2, R3, R4, R ct , R L , R n Resistance

[0267] t, t1, t2, t3, t a , t b Time

[0268] V OCV Open-circuit voltage

[0269] Z meas (t i ) Measured value (impedance data)

[0270] Theoretical value of the transient response of Z(t)

[0271] Z W Eddy current impedance

Claims

1. An impedance detection device for detecting the internal impedance of a secondary battery, wherein, Comprising: An acquisition unit that acquires at least one of current measurement data and voltage measurement data at I moments in the transient response of the secondary battery when supplying a specified current or a specified voltage to the secondary battery, where I is a natural number of 2 or more; and A calculation unit that calculates the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data, The calculation unit includes: A first calculation unit that calculates the I impedance data using at least one of the voltage measurement data and the current measurement data; A second calculation unit that calculates the element parameters of the equivalent circuit model of the secondary battery based on an M-th order equation obtained from the equivalent circuit model of the secondary battery and the I impedance data, where the M-th order equation represents the internal impedance of the secondary battery as a linear sum of multiple terms, and M is a natural number of 2 or more, The M-th order equation is an equation based on the theoretical value of the transient response of the internal impedance corresponding to the specified current or the specified voltage.

2. The impedance detection device according to claim 1, wherein The specified current or the specified voltage is a pulsed current or a pulsed voltage.

3. The impedance detection device according to claim 1 or 2, wherein The second calculation unit is configured to set the I impedance data equal to the M-th order equation and calculate the element parameters.

4. The impedance detection device according to claim 3, wherein The M-th order equation includes the multiple terms obtained by expanding the theoretical value of the transient response of the internal impedance of the secondary battery obtained from the equivalent circuit model of the secondary battery with respect to time, The multiple terms include (M + 1) coefficients, The second calculation unit is configured to set the I impedance data equal to the M-th order equation, calculate the (M + 1) coefficients respectively, and calculate the element parameters based on the calculated (M + 1) coefficients.

5. The impedance detection device according to claim 4, wherein The I is more than the (M + 1), The (M + 1) coefficients are calculated by the least squares method.

6. The impedance detection device according to any one of claims 1 to 5, wherein The equivalent circuit model of the secondary battery has a structure in which one or more parallel circuits are connected in series to a series resistance, and the parallel circuit is a parallel circuit of a capacitor and a resistor, The second calculation unit calculates at least the series resistance as the element parameter of the secondary battery.

7. The impedance detection device according to any one of claims 1 to 5, wherein The equivalent circuit model of the secondary battery has a structure in which one or more parallel circuits are connected in series to a series resistance, and the parallel circuit is a parallel circuit of a capacitor and a resistor, The second calculation unit calculates at least the total value of the capacitors in one or more of the parallel circuits as the element parameter of the secondary battery.

8. The impedance detection device according to any one of claims 1 to 7, wherein The acquisition unit acquires the current measurement data and the voltage measurement data respectively, The first calculation unit calculates the I impedance data by dividing the I voltage measurement data by the corresponding I current measurement data at the same time.

9. An impedance detection method for detecting the internal impedance of a secondary battery, wherein, Comprising: An acquisition step of acquiring at least one of the I current measurement data and voltage measurement data at I moments in the pulse response of the secondary battery when a predetermined current or a predetermined voltage is supplied to the secondary battery, where I is a natural number of 2 or more; And A calculation step of calculating the internal impedance of the secondary battery based on at least one of the current measurement data and the voltage measurement data. In the calculation step, Using at least one of the voltage measurement data and the current measurement data, calculate the I impedance data. Based on the M-th order equation obtained from the equivalent circuit model of the secondary battery and the I impedance data, calculate the element parameters of the equivalent circuit model of the secondary battery. The M-th order equation represents the internal impedance of the secondary battery by a linear sum of multiple terms, and M is a natural number of 2 or more. The M-th order equation is an equation based on the theoretical value of the transient response of the internal impedance corresponding to the predetermined current or the predetermined voltage.

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