Battery management circuit, battery management system and battery management network

Abstract

The battery management circuit (105) includes: a reference signal generation unit (109) that generates first and second reference frequency signals having different phases; an AC superimposition unit (104) that superimposes an alternating current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement unit (115) that measures a voltage of the secondary battery by sampling at a higher frequency than the first reference frequency signal; a current measurement unit (112) that measures a current of the secondary battery by sampling at a higher frequency than the first reference frequency signal; and a conversion unit (118b) that converts measurement results of the voltage measurement unit (115) and the current measurement unit (112) into real and imaginary components of complex voltage and complex current, respectively, by multiplying the measurement results by the first and second reference frequency signals.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a battery management circuit, a battery management system, and a battery management network that manage the state of a battery. BACKGROUND

[0002] Development of a vehicle that travels using a secondary battery as a power source, such as a HEV (Hybrid Electric Vehicle) or an EV (Electric Vehicle), is being conducted. In order to safely use a secondary battery, a technology of performing battery remaining amount estimation and abnormality detection by a battery management system (BMS) is known.

[0003] For example, Patent Literature 1 discloses a battery state determination device that can measure the complex impedance of a battery and diagnose the capacity and the amount of deterioration of the battery.

[0004] Patent Literature 2 discloses a capacity maintenance rate determination device that can determine the capacity maintenance rate without performing full charge and discharge of a battery.

[0005] Patent Literature 3 discloses a vehicle controller that programs charge and discharge of a battery using parameters of an RC circuit model corresponding to the impedance of the battery.

[0006] Non-Patent Literature 1 specifically discloses a method that applies an alternating current to the complex impedance of a battery and measures an alternating voltage, and determines the complex impedance of the battery by an alternating superposition method.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Publication No. 2015-94726

[0010] Patent Literature 2: Japanese Patent Application Publication No. 2011-38857

[0011] Patent Literature 3: U.S. Patent No. 10023064

[0012] NON-PATENT LITERATURE

[0013] Non-Patent Literature 1: "IC for online EIS in automotive batteries and hybrid architecture for high-current perturbation in low-impedance cells" Z. Gong, Z. Liu, Y. Wang, et al., 2018 IEEE Applied Power Electronics Conference and Exposition (APEC) SUMMARY

[0014] PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] However, according to the related art, there is a problem that an error is easily generated in measurement of complex impedance.

[0016] The present disclosure provides a battery management circuit, a battery management system, and a battery management network that measure complex impedance of a secondary battery with high precision with a simple circuit structure.

[0017] MEANS FOR SOLVING PROBLEMS

[0018] The battery management circuit of one embodiment of the present disclosure is a battery management circuit that manages a secondary battery, and includes a reference signal generation portion that generates a first reference frequency signal and a second reference frequency signal having a different phase from the first reference frequency signal; an AC superimposition portion that superimposes an alternating current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement portion that measures a voltage of the secondary battery by sampling at a higher frequency than the first reference frequency signal; a current measurement portion that measures a current of the secondary battery by sampling at a higher frequency than the first reference frequency signal; and a conversion portion that converts measurement results of the voltage measurement portion and the current measurement portion into real and imaginary components of a complex voltage and a complex current, respectively, by multiplying the measurement results by the first reference frequency signal and the second reference frequency signal.

[0019] The battery management system of one embodiment of the present disclosure includes the above-described battery management circuit and a comprehensive control portion that specifies a frequency of the first reference frequency signal to the battery management circuit, the battery management circuit that transmits real and imaginary components of the complex voltage and the complex current to the comprehensive control portion, and the comprehensive control portion that calculates a complex impedance of the specified frequency on the basis of the transmitted real and imaginary components of the complex voltage and the complex current.

[0020] The battery management network of one embodiment of the present disclosure includes the battery management system described above and the server device that generates battery information including a result of estimating the state of the secondary battery on the basis of the measurement information.

[0021] Effects of Invention

[0022] The battery management circuit and the battery management system according to one embodiment of the present disclosure can measure the complex impedance of a secondary battery with high precision with a simple circuit structure. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a block diagram of a battery management system of an embodiment and a battery management server.

[0024] Figure 2 is a diagram of a structure example of a comprehensive control unit of an embodiment.

[0025] Figure 3 is a flowchart of a processing example of a comprehensive control unit of an embodiment.

[0026] Figure 4 is an explanatory diagram of a structure example of a battery cell of an embodiment and an example of an equivalent circuit model.

[0027] Figure 5A is a Cole-Cole plot showing an example of a complex impedance of a battery cell of an embodiment.

[0028] Figure 5B is a Bode plot showing an example of a complex impedance of a battery cell of an embodiment.

[0029] Figure 6 is a graph showing an example of a temperature characteristic of a complex impedance of a battery cell of an embodiment.

[0030] Figure 7 is a block diagram of a structure example of a battery management network of an embodiment.

[0031] Figure 8 is a timing chart of a processing example of a battery management network of an embodiment.

[0032] Figure 9 is a block diagram of a structure example of a battery management system of a modified example and a battery management server. DETAILED DESCRIPTION

[0033] (Insight as a Basis of the Present Disclosure)

[0034] The present inventors found that the following problems occur with regard to the device for managing a secondary battery described in the "BACKGROUND" section.

[0035] In a case where the internal complex impedance (also referred to as the AC impedance) of a secondary battery is measured by the AC superimposition method, a method in which the phase delay of a voltage change due to the internal complex impedance is expressed by a complex number on the basis of an applied AC current, the complex voltage is measured, and the measured complex voltage is divided by the applied current to perform the calculation is generally used. The applied AC current is a current that is applied to the secondary battery after being amplified in accordance with a reference frequency signal.

[0036] In this method, the phase of the AC current actually applied to the secondary battery is often delayed from the phase of the reference frequency signal due to the influence of a wire (for example, a wiring harness) that connects the secondary battery and a device for measurement, a drive amplifier that amplifies the reference frequency signal, and the like.

[0037] On the other hand, the voltage measurement is measured by an AD converter that samples with a sampling clock that is synchronized with the reference frequency signal. Therefore, the phase difference between the AC current actually applied to the secondary battery and the voltage measurement timing represents a phase error of the complex impedance, and thus, an error is easily generated in the complex impedance of the secondary battery.

[0038] In order to eliminate such a phase error, for example, feedback control of the AC current is required so that the frequency of the AC current actually applied to the secondary battery coincides with the original reference frequency signal.

[0039] However, in this method, the influence of a phase error due to the frequency characteristics within the feedback loop, a phase error generated in a later stage from the feedback point, cannot be excluded.

[0040] Further, in a case where feedback control is implemented, the feedback loop needs to be designed to be able to linearly operate. Since the complex impedance of an actual secondary battery is only several tens to several mΩ, the applied AC current needs to be a current value of several to several tens A, and it is difficult to design the frequency characteristics of a drive amplifier and the like so as not to affect the feedback loop, and other problems such as an increase in power consumption are generated.

[0041] Therefore, in the present disclosure, a battery management circuit, a battery management system, and a battery management network that measure the complex impedance of a secondary battery with high precision without performing feedback control of an applied AC current with a simple circuit structure are provided.

[0042] To solve such a problem, a battery management circuit of one embodiment of the present disclosure is a battery management circuit which manages a secondary battery, and includes: a reference signal generation portion which generates a first reference frequency signal and a second reference frequency signal having a different phase from the first reference frequency signal; an alternating current superimposition portion which superimposes an alternating current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement portion which measures a voltage of the secondary battery by sampling at a higher frequency than the first reference frequency signal; a current measurement portion which measures a current of the secondary battery by sampling at a higher frequency than the first reference frequency signal; and a conversion portion which converts measurement results of the voltage measurement portion and the current measurement portion into real and imaginary components of a complex voltage and a complex current, respectively, by multiplying the measurement results by the first reference frequency signal and the second reference frequency signal.

[0043] Thus, the complex impedance of the secondary battery can be measured with high accuracy without error in the orthogonality of the real and imaginary parts by a simple circuit structure. In other words, the real and imaginary parts of the complex voltage are separated and measured with the first and second reference signals generated orthogonally as a reference, the complex current is measured with the real and imaginary parts separated with the first and second reference signals as a reference, and the measured complex voltage is divided by the complex current, whereby the orthogonality of the real and imaginary parts of the measured complex impedance depends only on the orthogonality of the first and second reference signals, so that high-accuracy measurement in which the phase error of the complex impedance caused by the phase error of the measured voltage and the superimposed current is eliminated can be performed.

[0044] In addition, since the phase delay of the superimposed current is corrected, feedback control of the alternating current is not needed, so that the circuit structure can be made simple.

[0045] Hereinafter, embodiments will be described with reference to drawings. Note that each of the embodiments described below shows a general or specific example. Values, shapes, materials, positions of constituent elements, connection modes, steps, orders of steps, and the like shown in the following embodiments are examples, and the present disclosure is not intended to be limited to the following embodiments. Furthermore, the embodiments of the present disclosure are not limited to the current independent technical solutions, and can be expressed by other independent technical solutions.

[0046] In addition, each of the drawings is a schematic view and is not necessarily a strict illustration. In each of the drawings, the same reference numeral is attached to substantially the same structure, and repetitive description is omitted or simplified.

[0047] (Embodiment 1)

[0048] [Structure]

[0049] First, the structure of the battery management system of Embodiment 1 will be described.

[0050] Figure 1 is a structural example of the battery management system 200 of the embodiment and a block diagram of the battery management server 301.

[0051] The battery management system 200 of the figure is provided with a plurality of battery packs 101, a plurality of battery management devices 100, and a comprehensive control section 201. The comprehensive control section 201 and the plurality of battery management devices 100 are daisy-chained through a communication line 132.

[0052] The battery pack 101 is a secondary battery including a plurality of battery cells B0 to B5 connected in series. Each battery cell is, for example, a lithium-ion battery, but can also be another battery such as a nickel-hydrogen battery. In addition, it can also be a series-connected power storage cell such as a lithium-ion capacitor. The battery pack 101 is connected to a load and a charging circuit. The load is, for example, a motor of an HEV or an EV, but is not limited thereto. In addition, Figure 1 The battery pack 101 of the figure shows an example having six battery cells, but the number of battery cells within the battery pack 101 is not limited to six.

[0053] The battery management device 100 is a device that manages the state of the battery pack 101, and is also called a cell management unit (CMU). The battery management device 100 calculates the AC impedance of the battery pack 101, and specifically, calculates the complex impedance (also called the AC impedance) of each of the battery cells B0 to B5. Therefore, the battery management device 100 is provided with a battery management circuit 105 and a temperature sensor 107 (for example, a thermistor).

[0054] In addition, the battery management circuit 105 can also be configured as an integrated circuit (IC) of one chip, for example. In addition, the battery management device 100 can also be configured as an IC chip on which the battery management circuit 105 is mounted and a printed circuit board (PCB) of the temperature sensor.

[0055] The battery management circuit 105 is provided with an AC superimposition section 104, a reference signal generation section 109, a current measurement section 112, a clock generation section 113, a voltage measurement section 115, a reference voltage generation section 117, a conversion section 118b, an integration section 118c, a holding section 118d, a temperature measurement section 120, and a communication interface section 131.

[0056] The AC superimposition section 104 superimposes an AC current having a frequency component of a first reference frequency signal generated by the reference signal generation section 109 on the secondary battery. Figure 1 The AC superimposition section 104 has a differential buffer that applies the first reference frequency signal as a differential signal to the positive electrode and the negative electrode of the battery pack 101.

[0057] The reference signal generating section 109 generates a first reference frequency signal and a second reference frequency signal having a phase orthogonal to the first reference frequency signal. For example, the first reference frequency signal is a sine wave signal, and the second reference frequency signal is a cosine wave signal. In addition, the first reference frequency signal and the second reference frequency signal are preferably orthogonal within a range of allowable phase error, and it is not necessary to be exactly 90 degrees, and the allowable error. Also, since distortion occurs on a complex plane, the calculation becomes very complicated, but it is possible to perform measurement at a phase other than 90 degrees, for example, at a phase of 45 degrees, of the first reference frequency signal and the second reference frequency signal, and convert to a complex plane in which the real part and the imaginary part are orthogonal after measurement.

[0058] In addition, the reference signal generating section 109 accepts designation of the frequency f of the first reference frequency signal from the integrated control section 201 via the communication interface section 131, and generates the first reference frequency signal in accordance with the designation.

[0059] The current measuring section 112 measures the alternating current superimposed on the battery pack 101 by sampling the current of the battery pack 101 using the sampling clock signal from the clock generating section 113. The current of the battery pack 101 is measured as the voltage drop of the current detection resistor element 106 inserted into a path through which the alternating current applied by the alternating current superimposition section 104 flows. This voltage drop is proportional to the alternating current, and thus means the alternating current value. More specifically, the current measuring section 112 has an analog-digital converter for measuring the current of the battery pack 101 as a secondary battery. The analog-digital converter samples the voltage drop of the current detection resistor element 106 using the sampling clock signal from the clock generating section 113, and converts the sampled voltage drop to a digital signal.

[0060] The clock generating section 113 generates a sampling clock signal having a higher frequency than the first reference frequency signal and being synchronized with the first reference frequency signal. The sampling clock signal is supplied to the current measuring section 112 and the voltage measuring section 115. For example, in the case of measuring a complex impedance of about 5 KHz, the frequency of the first reference frequency signal is about 5 KHz, and the sampling clock needs to be set to satisfy the required phase resolution. Therefore, if the phase resolution is about 1 degree in the case of measuring a frequency of about 5 KHz, the sampling clock can be about 1.8 MHz which is 360 times 5 KHz.

[0061] The voltage measurement section 115 measures the voltage of the battery pack 101 by sampling the voltage of the battery pack 101 using the sampling clock signal from the clock generation section 113. More specifically, the voltage measurement section 115 has the same number of analog-digital converters (ADC0 to ADC5) as the number of the battery cells B0 to B5 in the battery pack 101. Each analog-digital converter samples the voltage of the corresponding battery cell among the plurality of battery cells B0 to B5 using the sampling clock signal from the clock generation section 113, and converts the sampled voltage to a digital signal. The voltage measurement section 115 uses the same sampling clock as the current measurement section 112, and thus can minimize the phase error of the measurement frequency and the sampling clock, and achieve high-precision complex frequency measurement.

[0062] The reference voltage generation section 117 supplies a common reference voltage to the plurality of analog-digital converters (ADC0 to ADC5) of the voltage measurement section 115, the analog-digital converter of the current measurement section 112, and the analog-digital converter of the temperature measurement section 120. More specifically, the reference voltage generation section 117 is a BGR (Band Gap Reference) circuit that outputs a stable constant voltage value with respect to the variation of temperature or power supply voltage, and generates, for example, a voltage of about 1.25 V due to the band gap of silicon. The plurality of analog-digital converters of the voltage measurement section 115 and the analog-digital converter of the current measurement section 112 use the same reference voltage, and thus the absolute error of the reference voltage is canceled by the division operation of the denominator / nominator in the complex impedance calculation. Therefore, the complex impedance can be measured with high precision.

[0063] The conversion section 118b converts the measurement results of the voltage measurement section 115 and the current measurement section 112 into real and imaginary components of complex voltage and complex current, respectively, by multiplying the measurement results of the voltage measurement section 115 and the current measurement section 112 by the first reference frequency signal and the second reference frequency signal. Thus, the conversion section 118b has the same number of multiplier pairs as the analog-digital converters (ADC0 to ADC5) of the voltage measurement section 115 and multiplier pairs corresponding to the analog-digital converters of the current measurement section 112. Each multiplier pair corresponding to the voltage measurement section 115 is composed of a multiplier that multiplies the conversion result (i.e., a sampled digital voltage value) of the corresponding analog-digital converter by the first reference frequency signal and a multiplier that multiplies the conversion result by the second reference frequency signal. The multiplication result of the former indicates the real component when the sampled voltage is expressed as complex voltage. The multiplication result of the latter indicates the imaginary component when the sampled voltage is expressed as complex voltage. The multiplier pair corresponding to the current measurement section 112 is composed of a multiplier that multiplies the conversion result (i.e., a sampled digital current value) of the corresponding analog-digital converter by the first reference frequency signal and a multiplier that multiplies the conversion result by the second reference frequency signal. The multiplication result of the former indicates the real component when the sampled current is expressed as complex current. The multiplication result of the latter indicates the imaginary component when the sampled current is expressed as complex current.

[0064] In addition, the analog-digital converters (ADC0 to ADC5) can each be, for example, a delta-sigma type analog-digital converter. Further, the plurality of analog-digital converters (ADC0 to ADC5) have the same analog-digital conversion characteristics. The analog-digital conversion characteristics are various parameters such as resolution (number of bits). Specifically, the same analog-digital converter is used in the plurality of analog-digital converters (ADC0 to ADC5). Thus, it is possible to reduce measurement errors caused by differences in conversion time (latency) due to differences in the types of analog-digital converters, which are generated between the battery cells B0 to B5.

[0065] The integrator 118c averages the real and imaginary components of the complex voltage and complex current, which are repeatedly measured by the voltage measurement unit 115 and converted by the conversion unit 118b. This averaging reduces measurement errors of the complex voltage and complex current, and improves resolution (measurement accuracy) through oversampling. It also enhances measurement accuracy. More specifically, the integrator 118c and the conversion unit 118b have the same number of averaging circuit pairs corresponding to their multipliers. Each averaging circuit pair consists of an averaging circuit that averages the real component of the complex voltage or complex current, and an averaging circuit that averages the imaginary component of the complex voltage or complex current. In the case of a lithium-ion battery, the internal complex impedance is, for example, a few mΩ. If the superimposed AC current is assumed to be 1A, the output voltage change is only a few mV. On the other hand, the DC output voltage of a lithium-ion battery is approximately 3.4V. Therefore, to measure the voltage using an analog-to-digital converter connected to a single battery cell, a dynamic range of approximately 4 to 5V is required. In this case, given the need for approximately 8 bits of accuracy in complex impedance measurement, an analog-to-digital converter with approximately 18 to 20 effective bits is required. However, high-resolution A / D converters consume significant power and have a large footprint. Furthermore, the internal complex impedance measured for electrochemical impedance analysis of lithium-ion batteries is measured in a low-frequency range from approximately 0.01Hz near DC to tens of kHz, making complex voltage measurements via AC connection impossible. Figure 1 In this structure, complex voltages or currents are separated into real and imaginary parts and averaged by repeatedly applying alternating current. Therefore, resolution can be improved through integration via oversampling. Thus, even with a relatively small number of bits (e.g., around 16 bits) in the analog-to-digital converter, complex impedance measurement results with an accuracy of 20–24 bits can be obtained. Therefore, if the accuracy of complex voltage measurement can be improved, the magnitude of the applied alternating current can be reduced, making it easier to measure secondary batteries with large capacity and low internal complex impedance.

[0066] The holding unit 118d holds the real and imaginary components of the complex voltage and complex current after averaging. Therefore, the holding unit 118d has the same number of register pairs as the multiple battery cells in the battery pack 101, and register pairs for holding the complex current, in order to hold the complex voltage. Each register pair for holding the complex voltage consists of a register (Re(Vi)) that holds the real component of the complex voltage of the corresponding battery cell and a register that holds the imaginary component (Im(Vi)). Here, i is an integer from 0 to 5. Furthermore, the register pair for holding the complex current consists of a register (Re(I0)) that holds the real component of the complex current of the corresponding battery pack 101 and a register that holds the imaginary component (Im(I0)).

[0067] The temperature measuring section 120 measures the temperature of the battery group 101 using the temperature sensor 107 provided to the battery group 101. The temperature sensor 107 can be, for example, a thermistor, but can also be a temperature sensor using other elements such as a thermocouple. Specifically, the temperature measuring section 120 is provided with an analog-digital converter and a temperature calculating section 121. The analog-digital converter samples the voltage of the temperature sensor 107 and converts the sampled voltage to a digital value. The temperature calculating section 121 calculates the temperature corresponding to the digital voltage from the analog-digital converter.

[0068] The communication interface section 131 is a communication circuit for the battery management circuit 105 to communicate with other battery management circuits 100 or the integrated control section 201. The communication interface section 131 is used, for example, to transmit the complex impedance and the like calculated by the holding section 118d to the integrated control section 201. The communication by the communication interface section 131 can be wireless communication or wired communication. The communication standard for the communication by the communication interface section 131 is not particularly limited.

[0069] The integrated control section 201 specifies the frequency f of the first reference frequency signal to the battery management circuit 100, and collects the real part component and the imaginary part component held in the holding section 118d from the plurality of battery management devices 100 via the communication line 132, and calculates the complex impedance at the specified frequency from the collected real part component and imaginary part component of the complex voltage and the complex current. In the calculation of the impedance, the AC impedance is calculated by dividing each of the complex voltages held in the holding section 118d by the complex current. Specifically, the integrated control section 201 has a division function, and calculates the AC impedance of the battery cell B0 by dividing the complex voltage represented by (Re(V0), Im(V0)) by the complex current represented by (Re(I0), Im(I0)), for example.

[0070] The battery management device 100 is a subordinate CMU (Cell Management Unit) that manages each battery cell. In contrast, the integrated control section 201 is a BMU (Battery Management Unit) of a superior system that manages the entire battery group. The integrated control section 201 is mounted with an MCU (Micro Control Unit) capable of performing high-speed large-capacity operation faster than the battery management device 100, and performs battery control. In the integrated control section 201, the complex impedance of each battery cell is calculated, and the state of the battery group is grasped. The integrated control section 201 is connected to the battery management device 100 via the communication line 132. Figure 1In the structure, the function of the battery management device 100 as the CMU is limited to measurement of the complex voltage and the complex current, and the superior comprehensive control section 201 with higher calculation ability calculates the complex impedance. Thus, in the complex impedance measurement, it is not necessary to mount a plurality of CMU-side arithmetic circuits that calculate the complex impedance, and it is possible to simplify the circuit of the CMU and realize the complex impedance measurement at low cost. In addition, it is easy for the comprehensive control section 201 to perform temperature correction of the variation of the complex impedance due to temperature, calculation of the measurement time by interval interpolation of the measurement frequency interval, and the like.

[0071] Next, a structure example of the comprehensive control section 201 will be described.

[0072] Figure 2 is a diagram showing a structure example of the comprehensive control section 201 according to the embodiment.

[0073] As shown in the diagram, the comprehensive control section 201 is provided with a CPU 31, a memory 32, a communication circuit 33, and a wireless circuit 34.

[0074] The CPU 31 executes a program stored in the memory 32.

[0075] The memory 32 stores various programs for managing a plurality of battery management devices 100, and various data including battery state data of the complex impedance of the battery pack 101.

[0076] The communication circuit 33 communicates with the plurality of battery management devices 100 connected in daisy chain through the communication line 132.

[0077] The wireless circuit 34 performs wireless communication with the battery management server 301.

[0078] [Operation]

[0079] Next, a specific processing example of the comprehensive control section 201 will be described.

[0080] Figure 3 is a flowchart showing a processing example of the comprehensive control section 201 according to the embodiment.

[0081] In the diagram, a processing example for one of the plurality of battery management devices 100 is shown. The comprehensive control section 201 also sequentially performs the same processing for the other battery management devices 100.

[0082] First, the integrated control section 201 specifies the frequency f of the first reference frequency signal to the battery management device 100 (Sll). In response to this, the battery management device 100 generates the first reference frequency signal of the specified frequency, and performs measurement of the complex voltage, the complex current, and the temperature of the battery pack 101 as the secondary battery. When these measurements are completed, the integrated control section 201 acquires data indicating the measured complex voltage, complex current, and temperature of the battery pack 101 from the battery management device 100 via the communication line 132 (S12 to S14). In addition, instead of acquiring the temperature of the battery pack 101, the temperature of the secondary battery at the time of measurement can be estimated from the calculated complex impedance converted to the past complex impedance and information indicating the temperature of the secondary battery. This estimation is useful for the battery management device 100 not equipped with the temperature sensor 107.

[0083] Next, the integrated control section 201 calculates the complex impedance of the specified frequency from the real and imaginary components of the complex voltage and complex current in the acquired data (S15). In addition, the integrated control section 201 can specify multiple times while changing the frequency f of the first reference frequency signal, and calculate the change in the complex impedance corresponding to the change in the specified frequency.

[0084] Further, the integrated control section 201 generates drawing data indicating the Cole-Cole plot that sets the complex impedance as a locus on the complex plane (S16). In addition, the integrated control section 201 can generate drawing data indicating the Bode plot that converts the complex impedance to the magnitude and phase instead of the drawing data indicating the Cole-Cole plot.

[0085] In addition, the integrated control section 201 normalizes the complex impedance based on the acquired temperature (or the estimated temperature) (S17). Specifically, the integrated control section 201 converts the complex impedance to the complex impedance corresponding to a prescribed temperature based on the acquired temperature. In addition, the order of step S16 and step S17 can be reversed. That is, the integrated control section 201 can generate the drawing data after the normalization based on the temperature.

[0086] Next, the integrated control section 201 calculates the element constant of the circuit element such as the resistance R and the capacitance C that constitute the equivalent circuit model indicating the corresponding battery cell based on the complex impedance corresponding to the prescribed temperature (i.e., the complex impedance corrected to the standard temperature different from the measured temperature) (S18).

[0087] Further, the comprehensive control section 201 generates measurement information including the complex impedance and the element constant of the above-described element, gives the measurement information identification information that identifies the corresponding battery cell (S19), and further gives information indicating the current time and the operation time (S20). The comprehensive control section 201 transmits the measurement information to which the identification information, the current time, and the operation time are given as battery state data to the battery management server 301 via a network (S21).

[0088] Next, an example of an equivalent circuit model of a battery cell and element constants thereof will be described.

[0089] Figure 4 is a diagram showing an example of a configuration example of a battery cell of the embodiment and an equivalent circuit model. Figure 4 (a) of shows a symbol of the battery cell B0. Figure 4 (b) of shows a configuration example in a case where the battery cell B0 is a lithium ion battery. As a premise of the equivalent circuit model, the battery cell B0 has a negative electrode, a negative electrode material, an electrolyte, a separator, a positive electrode material, and a positive electrode. Figure 4 (c) of shows an example of an equivalent circuit model of the battery cell B0. The equivalent circuit model has an inductive component L0, resistance components R0 to R2, capacitance components C1 and C2, and a lithium ion diffusion resistance component Zw. The inductive component L0 represents an impedance component of an electrode wire. The resistance component R0 represents an impedance component of an electrolyte. A parallel circuit of the resistance component R1 and the capacitance component C1 represents an impedance component of a negative electrode. A circuit portion composed of the resistance component R2, the lithium ion diffusion resistance component Zw, and the capacitance component C2 represents an impedance component of a positive electrode. The lithium ion diffusion resistance Zw is known as a Warburg Impedance.

[0090] If the element constants of each circuit element that constitutes such an equivalent circuit model are calculated, the state of the battery cell B0 can be estimated. For example, the deterioration state of the battery cell B0 can be estimated from the change in the element constants over time.

[0091] Next, an example of a characteristic of the complex impedance of a battery cell will be described.

[0092] Figure 5A is a Cole-Cole plot showing an example of the complex impedance of a battery cell of the embodiment. Figure 5A The thick solid line in (a) and (b) of shows an example of a correct complex impedance with no phase error. Figure 5A The thick dotted line in (a) of shows an example of a complex impedance in a case where a phase error with a fixed angle occurs. In addition, Figure 5A The thick dotted line in (b) of shows an example of a complex impedance in a case where a phase error with a fixed delay time occurs.

[0093] Cole-Cole plot is also called complex plane plot, Nyquist plot. Figure 5A The thick solid line in (a) and (b) of FIG. 10 corresponds to the correct complex impedance without phase error. Figure 4 The equivalent circuit model in (c) of FIG. 10. In a method of superimposing alternating current to calculate the complex impedance of a battery cell, it is generally known that in a case where charge movement is rate-determining, resistance and capacitance are represented by an equivalent circuit of a parallel configuration, which is semicircular in the complex plane. Furthermore, in a case where the Warburg impedance is included, it is generally known that from the middle of the semicircle (near the upper right), it becomes a straight line rising at an inclination of 45 degrees as an inclination caused by the Warburg impedance.

[0094] In the calculation of the complex impedance, if the measurement system of voltage and current has a phase error, the phase error is represented as the complex impedance. Generally, the phase error of the measurement system factor has a frequency characteristic, and becomes a problem in the case of measuring the complex impedance at different frequencies. In particular, in the case of plotting the complex impedance at each frequency in the Cole-Cole plot while making the frequency variable, the frequency phase error is represented as an orthogonal error of the real axis (horizontal axis) and the imaginary axis (vertical axis) on the complex plane of the Cole-Cole plot. Therefore, it is difficult to plot an accurate Cole-Cole plot. However, in the structure of FIG. 10, Figure 1 In the structure of FIG. 10, by calculating the complex impedance after measuring the complex voltage and the complex current, the phase error of the measurement system of voltage and current is minimal, and an accurate Cole-Cole plot can be plotted. As shown by the thick solid line in (a) of FIG. 10, in a case where the phase error is fixed in angle, the Cole-Cole plot has a characteristic of rotating around the origin. In addition, as shown by the thick solid line in (b) of FIG. 10, in a case where the phase error is fixed in delay time, the Cole-Cole plot has a characteristic of rotating only on the high frequency side, and coinciding with the thick solid line on the low frequency side. In other words, it has a characteristic that the phase error is generated only on the high frequency side, and not generated on the low frequency side. Figure 5A Figure 5A

[0095] FIG. 11 is a Bode plot showing an example of the complex impedance of the battery cell of the embodiment. Figure 5B The thick solid line in the upper part of (a) and the upper part of (b) of FIG. 10 shows an example of the magnitude of the correct complex impedance without phase error with respect to the frequency. Figure 5B The thick solid line in the lower part of (a) and the lower part of (b) of FIG. 10 shows an example of the phase θ of the correct complex impedance without phase error with respect to the frequency. Figure 5B The thick solid line in the lower part of (a) and the lower part of (b) of FIG. 10 shows an example of the phase θ of the correct complex impedance without phase error with respect to the frequency.

[0096] Figure 5B The thick solid line in the lower part of (a) and the lower part of (b) of FIG. 10 shows an example of the phase θ of the correct complex impedance without phase error with respect to the frequency. Figure 5B ​The thick dashed line in the lower part of (b) represents an example of the phase θ of the complex impedance relative to the frequency in the case of a phase error with a fixed delay time. Figure 5B The thick solid lines in (a) and (b) are Figure 4 The equivalent circuit model of (c) corresponds to this.

[0097] When depicting a complex impedance as a Bode plot representing magnitude and phase while simultaneously varying the frequency, phase errors in the voltage and current measurement system are represented as phase errors on the Bode plot. Therefore, it is difficult to accurately depict a complex impedance as a Bode plot. However, in... Figure 1 In this structure, by calculating the complex impedance after measuring the complex voltage and complex current, the phase error of the voltage and current measurement system is minimized, enabling the accurate depiction of the Bode plot. For example... Figure 5B As shown by the thick dashed line at the bottom of (a), when the angle of phase error is fixed, the Bode plot indicating phase relative to frequency exhibits a parallel shift characteristic. Additionally, as... Figure 5B As shown by the thick dashed line at the bottom of (b), with a fixed phase error delay time, the Bode plot of phase relative to frequency has the characteristic that it is only affected by the high-frequency side, while coinciding with the thick solid line at the low-frequency side. In other words, it has the characteristic that the phase error only occurs on the high-frequency side and not on the low-frequency side.

[0098] also, Figure 5A , Figure 5B This is useful in estimating the condition of individual battery cells. For example, it can be assumed that the more degraded a battery cell is, the better. Figure 5A The thicker solid line increases in size as it moves to the right. This can be interpreted as indicating that the more degraded the individual battery cell, the more... Figure 5B The thick solid line at the top of the character increases in size as it rises.

[0099] Next, the temperature characteristics of the individual battery cells will be explained.

[0100] Figure 6 This is a graph showing an example of the temperature characteristics of the complex impedance of a battery cell in an embodiment. The graph shows Cole-Cole plots for battery cell temperatures of 20°C, 25°C, and 30°C. As mentioned above, the complex impedance of a battery cell is temperature-dependent; however, by converting the complex impedance to a normalized complex impedance corresponding to a specified temperature, the effect of temperature dependence can be reduced.

[0101] As described above, the battery management circuit 105 is capable of measuring the complex impedance of each individual cell in the battery pack 101 with high precision using a simple circuit structure.

[0102] As explained above, the battery management circuit 105 of Embodiment 1 is a battery management circuit that manages a secondary battery, and includes: a reference signal generation section 109 that generates a first reference frequency signal and a second reference frequency signal having a phase that is offset by 90 degrees from the first reference frequency signal; an AC superimposition section 104 that superimposes an alternating current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement section 115 that measures a voltage of the secondary battery by sampling at a higher frequency than the first reference frequency signal; a current measurement section 112 that measures a current of the secondary battery by sampling at a higher frequency than the first reference frequency signal; and a conversion section 118b that converts measurement results of the voltage measurement section 115 and the current measurement section 112 into real number components and imaginary number components of a complex voltage and a complex current, respectively, by multiplying the measurement results by the first reference frequency signal and the second reference frequency signal.

[0103] Thus, the complex impedance of the secondary battery can be measured with high accuracy with a simple circuit configuration.

[0104] Here, the battery management circuit 105 can also include a clock generation section 113 that generates a sampling clock signal that is higher in frequency and synchronous with the first reference frequency signal, and the voltage measurement section 115 and the current measurement section 112 sample using the sampling clock signal generated by the clock generation section 113.

[0105] In addition, the clock generation section 113 can generate one or more sampling clock signals.

[0106] In addition, the plurality of sampling clock signals can be synchronous with the first reference frequency signal, or can be asynchronous with the first reference frequency signal. Even if the sampling clock signal is asynchronous with the first reference frequency signal, as long as the frequency is sufficiently higher than the first reference frequency signal, the voltage measurement section 115 and the current measurement section 112 can measure the voltage and the current with high accuracy.

[0107] The voltage measurement section 115 and the current measurement section 112 can use the same sampling clock signal, or can use different sampling clock signals. That is, the sampling signals for voltage measurement and current measurement can be the same sampling clock signal, or can be different sampling clock signals. Even if the sampling clock signals are different, as long as the frequencies are sufficiently higher than the first reference frequency signal, the same measurement as in the case of using the same sampling clock signal can be performed.

[0108] Here, the voltage measurement section 115 and the current measurement section 112 can repeatedly measure the voltage and the current of the secondary battery, and the battery management circuit 105 can include an integration section 118c that averages the real number components and the imaginary number components of the complex voltage and the complex current, respectively, corresponding to the repeated measurements.

[0109] Thus, the resolution of the voltage measurement and the current measurement can be improved by averaging, and the measurement accuracy can be improved. If the measurement accuracy of the complex voltage can be improved, the size of the applied alternating current can be reduced, and a secondary battery having a large capacity and a small internal complex impedance can be easily measured.

[0110] Here, the voltage measurement section 115 has one or more analog-digital converters for measuring the voltage of the secondary battery, the current measurement section 112 has an analog-digital converter for measuring the current of the secondary battery, and the battery management circuit 105 can have a reference voltage circuit 117 that supplies a common reference voltage to the one or more analog-digital converters of the voltage measurement section 115 and the analog-digital converter of the current measurement section 112.

[0111] For example, even an analog-digital converter having a small number of bits (e.g., about 16 bits) can provide a complex impedance measurement result having a precision of 20 to 24 bits. Further, since the voltage measurement and the current measurement use the same reference voltage, the absolute error of the reference voltage occurs in both the numerator and the denominator in the calculation of the complex impedance, i.e., the measured voltage divided by the measured current, and is canceled out. Thus, the complex impedance can be measured with high precision.

[0112] Here, the battery pack 101 as the secondary battery has a plurality of battery cells connected in series, and the voltage measurement section 115 can have the same number of analog-digital converters as the battery cells as the one or more analog-digital converters, and measure the voltage of each of the plurality of battery cells.

[0113] Thus, the voltage measurement and the current measurement of the plurality of battery cells can be performed simultaneously and in parallel by the same number of analog-digital converters as the battery cells. The measurement can be performed with high precision even in the case of a sharp temperature change.

[0114] Here, the battery management circuit 105 can be a one-chip semiconductor integrated circuit (BMIC).

[0115] Thus, the battery management device 100 can be easily implemented as an IC, and cost reduction can be easily achieved.

[0116] In addition, the battery management system 200 of Embodiment 1 has the above-described battery management circuit 105, and a comprehensive control section 201 that specifies the frequency of the first reference frequency signal to the battery management circuit 100, the battery management circuit 100 that transmits the real component and the imaginary component of each of the complex voltage and the complex current to the comprehensive control section 201, and the comprehensive control section 201 that calculates the complex impedance at the specified frequency based on the transmitted real component and imaginary component of each of the complex voltage and the complex current.

[0117] Here, the battery management system 200 has at least one battery management circuit 105, and a communication line 132 that daisy-chains the integrated control section 201 and the at least one battery management circuit 105, and the integrated control section 201 can collect the real number component and the imaginary number component from the at least one battery management circuit 105 via the communication line 132.

[0118] Thus, the integrated control section 201 is a superior system that manages the entire battery pack, and the integrated control section 201 calculates the complex impedance using the complex voltage and the complex current measured by the battery management circuit 105. Thus, in the complex impedance measurement, the circuit structure of the battery management circuit 105 can be simplified, and can be implemented at low cost. In addition, by the integrated control section 201 collecting the complex voltage and the complex current, it also becomes easy to highly correct measurement errors or measurement temperature deviations, and the like.

[0119] Here, the integrated control section 201 can also be specified multiple times while changing the frequency of the first reference frequency signal, and calculate the change in the complex impedance corresponding to the change in the specified frequency.

[0120] Thus, it is possible to calculate the change in the complex impedance corresponding to the change in the frequency under the control of the integrated control section 201.

[0121] Here, the integrated control section 201 can generate drawing data indicating a Cole-Cole plot that sets the complex impedance as a locus on a complex plane.

[0122] Here, the integrated control section 201 can also generate drawing data indicating a Bode plot that converts the complex impedance into a magnitude and a phase.

[0123] Thus, using the Cole-Cole plot or the Bode plot of the secondary battery, it is easy to perform state estimation (deterioration state, and the like) of the battery cell.

[0124] Here, the integrated control section 201 can also acquire the temperature of the secondary battery, and convert the complex impedance into a complex impedance corresponding to a prescribed temperature according to the acquired temperature.

[0125] According to this structure, it is possible to reduce the influence of the temperature dependence of the complex impedance of the secondary battery.

[0126] Here, the integrated control section 201 can also estimate the temperature of the secondary battery at the time of measurement according to the conversion of the calculated complex impedance into a past complex impedance and information indicating the temperature of the secondary battery.

[0127] Thus, even a battery management device that does not have a temperature sensor can estimate the temperature of the secondary battery at the time of measurement.

[0128] Here, the comprehensive control section 201 can also calculate the element constant of the circuit element constituting the equivalent circuit model of the secondary battery based on the complex impedance corresponding to the prescribed temperature.

[0129] Thus, the state estimation using the equivalent circuit model of the secondary battery can be performed.

[0130] Here, the comprehensive control section 201 can also attach the identification information identifying the secondary battery to the measurement information including the calculated complex impedance, and transmit the measurement information to which the identification information is attached to the server device via the network.

[0131] Thus, the battery management system 200 can perform the battery management in cooperation with the server device (battery management server 301).

[0132] Here, the comprehensive control section 201 can also receive the battery information including the result of estimating the state of the secondary battery based on the measurement information from the server device.

[0133] (Embodiment 2)

[0134] Next, a structure example of the battery management network in the case where the battery management server 301 is a so-called cloud server device will be described.

[0135] Figure 7 is a block diagram showing a structure example of the battery management network of the embodiment. The battery management network of this drawing includes the automobile 400 and the cloud system 300.

[0136] The automobile 400 is provided with the battery management system 200 and the motor 401.

[0137] The battery management system 200 has been described by the embodiment 1. Figure 7 The comprehensive control section 201 in the battery management system 200 communicates with the server device of the cloud system 300 via the wireless circuit 34. Further, there is sometimes a relay device between the wireless circuit 34 and the server device 301.

[0138] The cloud system 300 is a server device group on a network including the server device 301. The battery management server 301 is a server device disposed at a place separate from the battery management system 200. The server device 301 is a so-called cloud server.

[0139] Figure 8 is a timing chart showing a processing example of the battery management network of the embodiment.

[0140] The battery management system 200 of the automobile 400 appends, in Embodiment 1, identification information that identifies the secondary battery to the measurement information that contains the calculated complex impedance, and transmits the measurement information to which the identification information is appended as battery state data to the server device 301 via a network (S21).

[0141] The battery management server 301 estimates the state of the secondary battery based on the battery state data (S22), and generates battery information that contains the estimation result. The state of the secondary battery includes, for example, the state of charge of the battery, the deterioration state, the operation history, and the like. Further, the server device 301 transmits the battery information that is the state estimation result to the automobile 400 (S23).

[0142] Further, the battery management system 200 performs block issuance (S24) of block data that contains the measurement information or the battery information to the server device 301.

[0143] The battery management server 301 performs sharing processing of sharing the issued block data in a cloud server device group (S25). The sharing processing can be, for example, processing called mining processing. The cloud server device group shares a collection of the block data as a block chain, performs processing of joining the block data issued from the automobile 400 to the block chain (that is, mining processing), and performs state estimation and deterioration diagnosis.

[0144] After the processing of connecting the battery management server 301 to the block chain is completed, the battery management server 301 transmits data indicating block acknowledgment to the automobile 400 (S26).

[0145] As described above, the server device 301 of Embodiment 2 is contained in a server device group that shares battery information on a network.

[0146] Therefore, cloud battery telematics can be realized. Here, the cloud battery telematics refers to battery management using a cloud service system and a battery management system 200 mounted on an automobile and capable of connecting to a network, as a part of information services that can utilize various information.

[0147] Here, the integrated control section 201 can also cause a server device group to share a collection of block data by transmitting block data that contains measurement information or battery information to the server device.

[0148] Thus, block data that contains measurement information or battery information can be shared and managed by a server device group. For example, if the server device group manages block data by a block chain technology, battery information can be securely managed.

[0149] (Modified Example)

[0150] Next, a modification of the battery management system 200 of Embodiments 1 and 2 will be described.

[0151] Figure 9 is a configuration example of the battery management system of the modification and a block diagram of the battery management server.

[0152] This figure is the same as Figure 1 Compared with the battery management device 100, the battery management circuit 105A and the battery management circuit 105B are provided instead of the battery management circuit 105. Hereinafter, the differences will be described. The battery management circuit 105 as a single-chip semiconductor integrated circuit is divided into two-chip semiconductor integrated circuits. Also, the circuit structures of the current measurement section 112 and the voltage measurement section 115 are simplified.

[0153] The battery management circuit 105A mainly differs from the battery management device 100 in that it has a measurement section 122 that measures voltage, a first reference signal generation section as the reference signal generation section 109, and a first signal synchronization section 119.

[0154] The battery management circuit 105B has the current measurement section 112, the first signal synchronization section 119, a second reference signal generation section equivalent to the reference signal generation section 109, and a second synchronization section 119.

[0155] The first signal synchronization section controls the first reference signal generation section so that the phases of the first reference frequency signals inside the battery management circuit 105A and the battery management circuit 105B coincide.

[0156] The second signal synchronization section controls the second reference signal generation section so that the phases of the first reference frequency signals inside the battery management circuit 105A and the battery management circuit 105B coincide.

[0157] The measurement section 122 has a multiplexer (MUX) that selects one battery cell from a plurality of battery cells, an analog-digital converter that measures the voltage of the battery cell selected by the multiplexer, and a demultiplexer that distributes the conversion result of the analog-digital converter. The measurement section 122 sequentially selects one battery cell from a plurality of battery cells and measures the voltage thereof. In addition, the measurement section 122 also measures temperature.

[0158] As described above, in the battery management system 200 of the modified example, the secondary battery has a plurality of battery cells connected in series, the battery management circuit 105 includes a multiplexer that selects one battery cell from among the plurality of battery cells, and the one or more analog-digital converters of the voltage measurement section 115 is one analog-digital converter that measures the voltage of the battery cell selected by the multiplexer.

[0159] Thus, by one analog-digital converter, the voltage measurement and the current measurement of the plurality of battery cells can be sequentially performed, and the circuit structure can be simplified.

[0160] Here, the battery management circuit can be configured of a first semiconductor integrated circuit (battery management circuit 105A) and a second semiconductor integrated circuit (battery management circuit 105B), the first semiconductor integrated circuit can have the voltage measurement section 115, a first reference signal generation section as the reference signal generation section 109, and a first signal synchronization section 119, the second semiconductor integrated circuit can have the current measurement section 112, the first signal synchronization section 119, a second reference signal generation section equivalent to the reference signal generation section 109, and a second signal synchronization section 119, the first signal synchronization section can control the first reference signal generation section so that the phase of the first reference frequency signal inside the first semiconductor integrated circuit and the phase of the first reference frequency signal inside the second semiconductor integrated circuit coincide, and the second signal synchronization section can control the second reference signal generation section so that the phase of the first reference frequency signal inside the first semiconductor integrated circuit and the phase of the first reference frequency signal inside the second semiconductor integrated circuit coincide.

[0161] Thus, if only one second semiconductor integrated circuit is provided in the entire battery management system 200, the measurement of the current can be performed collectively at one place for the plurality of battery packs 101. In other words, since the measurement of the current does not need to be performed individually for the plurality of battery packs 101, the circuit structure can be further simplified. Moreover, by the first and second signal synchronization sections, the phase of the first reference frequency signal inside the first semiconductor integrated circuit and the phase of the first reference frequency signal inside the second semiconductor integrated circuit coincide, and thus the measurement can be performed with high accuracy.

[0162] (Other Embodiments)

[0163] The embodiments have been described above, but the present disclosure is not limited to the above-described embodiments.

[0164] For example, in the above-described embodiments, the battery management system that manages the battery used for a vehicle such as an EV has been described, but the battery management system can manage any battery for any use.

[0165] In addition, the circuit structure described in the above-described embodiments is one example, and the present disclosure is not limited to the above-described circuit structure. That is, the present disclosure also includes a circuit capable of achieving the characteristic functions of the present disclosure, as with the above-described circuit structure. For example, a structure in which a switching element (transistor), a resistance element, or a capacitance element, or the like is connected in series or in parallel with respect to a certain element is also included in the present application, within a range in which the same functions as the above-described circuit structure can be achieved.

[0166] Further, in the above-described embodiments, the constituent elements included in the integrated circuit are realized by hardware. However, a part of the constituent elements included in the integrated circuit can also be realized by executing a software program suitable for the constituent element. A part of the constituent elements included in the integrated circuit can also be realized by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded in a recording medium such as a hard disk or a semiconductor memory.

[0167] Further, in the above-described embodiments, the processing performed by a specific processing unit can also be performed by another processing unit. In addition, in the actions described in the above-described embodiments, the order of a plurality of processes can be changed, or a plurality of processes can be performed in parallel.

[0168] Further, a mode obtained by various modifications thought of by those skilled in the art to each of the embodiments, or a mode realized by arbitrarily combining the constituent elements and functions in the embodiments within a range that does not depart from the gist of the present disclosure is also included in the present disclosure.

[0169] Industrial applicability

[0170] The present disclosure can be utilized in a battery management circuit, a battery management system, and a battery management network that manage a secondary battery.

[0171] Explanation of reference signs

[0172] 31 CPU

[0173] 32 memory

[0174] 33 communication circuit

[0175] 34 wireless circuit

[0176] 100, 100A, 100B battery management device

[0177] 101 battery pack

[0178] 104 AC superimposition unit

[0179] 105, 105A, 105B battery management circuit

[0180] 106 detection resistor

[0181] 107 temperature sensor

[0182] 109 reference signal generation section

[0183] 110 reference frequency generator

[0184] 111 phase shifter

[0185] 112 current measurement section

[0186] 113 clock generation section

[0187] 115 voltage measurement section

[0188] 117 reference voltage generation section

[0189] 118b conversion section

[0190] 118c integration section

[0191] 118d holding section

[0192] 119 synchronization section

[0193] 120 temperature measurement section

[0194] 121 temperature calculation section

[0195] 122 measurement section

[0196] 131 communication interface section

[0197] 132 communication line

[0198] 200 battery management system

[0199] 201 integrated control section

[0200] 300 cloud system

[0201] 301 battery management server

[0202] 302 communication line

[0203] 400 automobile

[0204] 401 motor

[0205] B0 to B5 battery cells

Claims

1. A battery management circuit that manages a secondary battery, wherein, Possess: reference signal generation section, generate the first reference frequency signal and have the second reference frequency signal with the first reference frequency signal different phase; AC superimposition section, superimposed with the alternating current having the frequency component of the first reference frequency signal to the secondary battery; voltage measurement section, by sampling at a higher frequency than the first reference frequency signal, measure the voltage of the secondary battery; current measurement section, by sampling at a higher frequency than the first reference frequency signal, measure the current of the secondary battery; and conversion section, by multiplying the measurement results of the voltage measurement section and the current measurement section by the first reference frequency signal and the second reference frequency signal, the measurement results are converted into the real part component and the imaginary part component of the complex voltage and the complex current respectively, The voltage measurement section and the current measurement section repeatedly measure the voltage and current of the secondary battery, The battery management circuit has an integration section that averages the real part component and the imaginary part component of the complex voltage and the complex current corresponding to the repeated measurement.

2. The battery management circuit according to claim 1, wherein The voltage measurement section has one or more analog-to-digital converters for measuring the voltage of the secondary battery, The current measurement section has an analog-to-digital converter for measuring the current of the secondary battery, The battery management circuit has a reference voltage circuit that supplies a common reference voltage to the one or more analog-to-digital converters of the voltage measurement section and the analog-to-digital converter of the current measurement section.

3. The battery management circuit according to claim 2, wherein The secondary battery has a plurality of battery cells connected in series, The voltage measurement section has the same number of analog-to-digital converters as the battery cells as the one or more analog-to-digital converters, and measures the voltage of each of the plurality of battery cells.

4. The battery management circuit according to claim 2, wherein The secondary battery has a plurality of battery cells connected in series, The battery management circuit has a multiplexer that selects one battery cell from the plurality of battery cells, The one or more analog-to-digital converters of the voltage measurement section is one analog-to-digital converter that measures the voltage of the battery cell selected by the multiplexer.

5. The battery management circuit according to any one of claims 1 to 4, wherein The battery management circuit is a semiconductor integrated circuit.

6. The battery management circuit according to any one of claims 1 to 4, wherein The battery management circuit is composed of a first semiconductor integrated circuit and a second semiconductor integrated circuit, The first semiconductor integrated circuit has the voltage measurement section, a first reference signal generation section as the reference signal generation section, and a first signal synchronization section, The second semiconductor integrated circuit has the current measurement section, a first signal synchronization section, a second reference signal generation section equivalent to the reference signal generation section, and a second signal synchronization section, The first signal synchronization section controls the first reference signal generation section so that the first reference frequency signal inside the first semiconductor integrated circuit and the first reference frequency signal inside the second semiconductor integrated circuit are in phase, The second signal synchronization section controls the second reference signal generation section so that the first reference frequency signal inside the first semiconductor integrated circuit and the first reference frequency signal inside the second semiconductor integrated circuit are in phase.

7. The battery management circuit according to any one of claims 1 to 4, wherein The second reference frequency signal has a phase orthogonal to the first reference frequency signal.

8. A battery management system, wherein, provided with: the battery management circuit according to any one of claims 1 to 7; and a comprehensive control section that specifies a frequency of the first reference frequency signal to the battery management circuit, the battery management circuit transmits real and imaginary components of each of the complex voltage and the complex current to the comprehensive control section, the comprehensive control section calculates a complex impedance of the specified frequency based on the transmitted real and imaginary components of each of the complex voltage and the complex current.

9. The battery management system of claim 8, wherein, provided with: at least one of the battery management circuits; and a communication line that daisy-chains the comprehensive control section and the at least one of the battery management circuits, the comprehensive control section collects the real and imaginary components from the at least one of the battery management circuits via the communication line.

10. The battery management system according to claim 8 or 9, wherein the comprehensive control section specifies the frequency of the first reference frequency signal multiple times while changing the frequency, and calculates a change in the complex impedance corresponding to the change in the specified frequency.

11. The battery management system according to claim 10, wherein the comprehensive control section generates drawing data of a Cole-Cole plot that represents a complex impedance as a locus on a complex plane.

12. The battery management system according to claim 10, wherein the comprehensive control section generates drawing data of a Bode plot that represents a complex impedance as a magnitude and a phase.

13. The battery management system according to claim 8 or 9, wherein the comprehensive control section acquires a temperature of the secondary battery, and converts the complex impedance into a complex impedance corresponding to a specified temperature based on the acquired temperature.

14. The battery management system according to claim 8 or 9, wherein the comprehensive control section estimates a temperature of the secondary battery at the time of measurement based on the calculated complex impedance, a past complex impedance, and information representing a temperature of the secondary battery.

15. The battery management system according to claim 13, wherein the comprehensive control section calculates an element constant of a circuit element constituting an equivalent circuit model of the secondary battery based on the complex impedance corresponding to the specified temperature.

16. The battery management system according to claim 8 or 9, wherein The integrated control section appends identification information that identifies the secondary battery to measurement information that includes the calculated complex impedance, and transmits the measurement information to which the identification information is appended to a server device via a network.

17. The battery management system according to claim 16, wherein The integrated control section receives battery information from the server device, the battery information including a result of estimation of a state of the secondary battery based on the measurement information.

18. The battery management system according to claim 17, wherein The server device is included in a group of server devices that share the battery information on the network.

19. The battery management system according to claim 18, wherein The integrated control section causes the group of server devices to share a collection of block data including the measurement information or the battery information by transmitting the block data to the server device.

20. A battery management network, wherein, Possessing: The battery management system according to any one of claims 17 to 19; and The server device, The server device generates the battery information based on the measurement information.

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