Battery management circuit, battery management system, and battery management network

Abstract

To provide a battery management circuit for precisely measuring a complex impedance of a secondary battery by a simple circuit configuration.SOLUTION: A battery management circuit 105 includes: a reference signal generation section 109 for generating first and second reference frequency signals having different phases; an AC superposition section 104 for superposing an AC current having a frequency component of the first reference frequency signal on a secondary battery; a voltage measurement section 115 for measuring the voltage of the secondary battery by performing sampling at a frequency higher than that of the first reference frequency signal; a current measurement section 112 for measuring the current of a secondary battery by performing sampling at a frequency higher than that of the first reference frequency signal; and a conversion section 118b for converting measurement results to real number part components of each of a complex voltage and a complex current 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.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a battery management circuit, a battery management system, and a battery management network for managing the state of a battery. [Background technology]

[0002] Automobiles that run on secondary batteries as a power source, such as HEVs (Hybrid Electric Vehicles) and EVs (Electric Vehicles), are being developed. In addition, in order to safely use secondary batteries, a technology is known that estimates the remaining battery capacity and detects abnormalities using a battery management system (BMS).

[0003] For example, Patent Document 1 discloses a battery state determination device that is capable of measuring the complex impedance of a battery and diagnosing the capacity and deterioration level of the battery.

[0004] Patent Document 2 discloses a capacity maintenance rate determination device that is capable of determining the capacity maintenance rate of a battery without completely charging and discharging the battery.

[0005] Patent Document 3 discloses a vehicle controller that programs the charging and discharging of a battery using parameters of an RC circuit model that corresponds to the impedance of the battery.

[0006] Non-Patent Document 1 specifically discloses a method for measuring the complex impedance of a battery by applying an AC current and measuring the AC voltage, thereby measuring the complex impedance by an AC superposition method. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2015-94726 A [Patent Document 2] JP 2011-38857 A [Patent Document 3] U.S. Patent No. 10023064 [Non-patent literature]

[0008] [Non-Patent Document 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 of the Invention [Problem to be solved by the invention]

[0009] However, the conventional technology has a problem in that errors are likely to occur in the measurement of complex impedance.

[0010] The present disclosure provides a battery management circuit, a battery management system, and a battery management network that measure the complex impedance of a secondary battery with a simple circuit configuration and with high accuracy. [Means for solving the problem]

[0011] A battery management circuit according to one embodiment of the present disclosure is a battery management circuit that manages a secondary battery, and includes a reference signal generating unit 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 superposition unit that superposes an AC current having a frequency component of the first reference frequency signal on the secondary battery, a voltage measurement unit that measures the voltage of the secondary battery by sampling at a frequency higher than the first reference frequency signal, a current measurement unit that measures the current of the secondary battery by sampling at a frequency higher than the first reference frequency signal, and a conversion unit that converts the measurement results into real and imaginary components of a complex voltage and complex current by multiplying the measurement results of the voltage measurement unit and the current measurement unit by the first reference frequency signal and the second reference frequency signal.

[0012] A battery management system according to one embodiment of the present disclosure includes the above-mentioned battery management circuit and an integrated control unit that specifies the frequency of the first reference frequency signal to the battery management circuit, wherein the battery management circuit transmits real and imaginary components of the complex voltage and the complex current to the integrated control unit, and the integrated control unit calculates a complex impedance of the specified frequency from the real and imaginary components of the complex voltage and the complex current transmitted thereto.

[0013] A battery management network according to one embodiment of the present disclosure includes the above-mentioned battery management system and the server device, and the server device generates battery information including a result of estimating the state of the secondary battery based on the measurement information. Effect of the Invention

[0014] According to the battery management circuit and the battery management system according to an aspect of the present disclosure, the complex impedance of a secondary battery can be measured with high accuracy using a simple circuit configuration. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is a block diagram showing a configuration example of a battery management system and a battery management server according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of a configuration of the integrated control unit according to the embodiment. [Diagram 3] FIG. 3 is a flowchart illustrating an example of processing by the integrated control unit according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of the structure of a battery cell according to an embodiment and an example of an equivalent circuit model. [Figure 5A] FIG. 5A is a Cole-Cole plot diagram showing an example of the complex impedance of a battery cell according to an embodiment. [Figure 5B] FIG. 5B is a Bode diagram showing an example of the complex impedance of the battery cell according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of temperature characteristics of the complex impedance of a battery cell according to the embodiment. [Figure 7] FIG. 7 is a block diagram illustrating a configuration example of a battery management network according to an embodiment. [Figure 8] FIG. 8 is a sequence diagram illustrating an example of a process performed by the battery management network according to the embodiment. [Figure 9] FIG. 9 is a block diagram showing a configuration example of a battery management system and a battery management server according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (Findings on which this disclosure is based) The present inventors have found that the following problems occur with the device for managing secondary batteries described in the "Background Art" section.

[0017] When measuring the internal complex impedance (also called AC impedance) of a secondary battery by the AC superposition method, the general method is to use the applied AC current as a reference, measure a complex voltage that expresses the phase delay of the voltage change caused by the internal complex impedance as a complex number, and calculate by dividing the measured complex voltage by the applied current. The applied AC current is amplified based on a reference frequency signal and applied to the secondary battery.

[0018] In this method, the phase of the AC current actually applied to the secondary battery often lags behind the phase of the reference frequency signal due to the influence of the electrical wiring (e.g., wire harness) connecting the secondary battery to the measuring device and the drive amplifier that amplifies the reference frequency signal.

[0019] On the other hand, the voltage is measured by an AD converter that samples with a sampling clock synchronized with a reference frequency signal. Therefore, the phase difference between the AC current actually applied to the secondary battery and the timing of the voltage measurement appears as a phase error in the complex impedance, which makes it easy for errors to occur in the complex impedance of the secondary battery.

[0020] To eliminate such a phase error, for example, it is necessary to feedback control the AC current so that the frequency of the AC current actually applied to the secondary battery coincides with the original reference frequency signal.

[0021] However, even with this method, it is not possible to eliminate the effects of phase errors due to frequency characteristics within the feedback loop, or phase errors occurring downstream from the feedback point.

[0022] Furthermore, when implementing feedback control, it is necessary to design the feedback loop so that it can operate linearly. Since the complex impedance of an actual secondary battery is only a few tens of mΩ to a few milliohms, the applied AC current needs to be a few amperes to a few tens of amperes, and it is extremely difficult to design the frequency characteristics of the driving amplifier etc. so that they do not affect the feedback loop, which also causes another problem of increased current consumption.

[0023] Therefore, the present disclosure provides a battery management circuit, a battery management system, and a battery management network that measure the complex impedance of a secondary battery with a simple circuit configuration and high accuracy without feedback control of the applied AC current.

[0024] In order to solve such problems, a battery management circuit according to one embodiment of the present disclosure is a battery management circuit that manages a secondary battery, and includes: a reference signal generating unit that generates a first reference frequency signal and a second reference frequency signal having a phase different from that of the first reference frequency signal; an AC superposition unit that superposes an AC current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement unit that measures the voltage of the secondary battery by sampling at a frequency higher than the first reference frequency signal; a current measurement unit that measures the current of the secondary battery by sampling at a frequency higher than the first reference frequency signal; and a conversion unit that converts the measurement results into real and imaginary components of a complex voltage and complex current by multiplying the measurement results of the voltage measurement unit and the current measurement unit by the first reference frequency signal and the second reference frequency signal.

[0025] According to this, the complex impedance of the secondary battery can be measured with high accuracy without error in orthogonality between the real part and the imaginary part with a simple circuit configuration. In other words, the complex voltage is separated into real and imaginary parts based on the first and second reference signals generated to be orthogonal, and measured, the complex current is separated into real and imaginary parts based on the same first and second reference signals as those used in the voltage measurement, and measured, and the measured complex voltage is divided by the complex current. Since the orthogonality between the real and imaginary parts of the measured complex impedance depends only on the orthogonality between the first and second reference signals, this enables high accuracy measurement without phase error in the complex impedance due to phase error between the measured voltage and the superimposed current.

[0026] Furthermore, since there is no need to feedback control the AC current in order to correct the phase delay of the superimposed current, the circuit configuration can be simplified.

[0027] Hereinafter, the embodiments will be described with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, the arrangement and connection forms of the components, steps, and the order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure. In addition, the realization of the present disclosure is not limited to the current independent claims, and may be expressed by other independent claims.

[0028] In addition, each drawing is a schematic diagram and is not necessarily a precise illustration. In each drawing, the same reference numerals are used for substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0029] (Embodiment 1) [composition] First, the configuration of the battery management system according to the first embodiment will be described.

[0030] FIG. 1 is a block diagram showing an example of the configuration of a battery management system 200 and a battery management server 301 according to an embodiment.

[0031] The battery management system 200 in the figure includes a plurality of assembled batteries 101, a plurality of battery management devices 100, and an integrated control unit 201. The integrated control unit 201 and the plurality of battery management devices 100 are daisy-chained together by a communication line 132.

[0032] The assembled battery 101 is a secondary battery and includes a plurality of battery cells B0 to B5 connected in series. Each battery cell is, for example, a lithium ion battery, but may be other batteries such as nickel metal hydride batteries. Also, each battery cell may be a series-connected storage cell such as a lithium ion capacitor. The assembled battery 101 is connected to a load and a charging circuit. The load is, for example, a motor of an HEV or EV, but is not limited to this. Note that, although an example of the assembled battery 101 in FIG. 1 having six battery cells is shown, the number of battery cells in the assembled battery 101 is not limited to six.

[0033] The battery management device 100 is a device that manages the state of the assembled battery 101, and is also called a cell management unit (CMU). The battery management device 100 calculates the AC impedance of the assembled battery 101, specifically, the complex impedance (also called AC impedance) of each of the battery cells B0 to B5. To this end, the battery management device 100 includes a battery management circuit 105 and a temperature sensor 107 (e.g., a thermistor).

[0034] The battery management circuit 105 may be configured as, for example, a one-chip integrated circuit (IC). The battery management device 100 may be configured as a printed circuit board (PCB) on which the IC chip of the battery management circuit 105 and a temperature sensor are mounted.

[0035] The battery management circuit 105 includes an AC superposition unit 104, a reference signal generating unit 109, a current measurement unit 112, a clock generation unit 113, a voltage measurement unit 115, a reference voltage generation unit 117, a conversion unit 118b, an integration unit 118c, a holding unit 118d, a temperature measurement unit 120, and a communication interface unit 131.

[0036] The AC superimposing unit 104 superimposes, on the secondary battery, an AC current having a frequency component of a first reference frequency signal generated by the reference signal generating unit 109. The AC superimposing unit 104 in Fig. 1 has a differential buffer that applies the first reference frequency signal as a differential signal to the positive and negative electrodes of the battery pack 101.

[0037] The reference signal generating unit 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. It is desirable that the first reference frequency signal and the second reference frequency signal are orthogonal within a range of an allowable phase error, but there is no need for them to be exactly 90 degrees, and an error is allowed. Furthermore, although the calculation becomes very complicated because of distortion in the complex plane, it is possible to measure the first reference frequency signal and the second reference frequency signal at a phase other than 90 degrees, for example, 45 degrees, and convert the signal into a complex plane in which the real part and the imaginary part are orthogonal after the measurement.

[0038] Furthermore, the reference signal generating unit 109 receives a specification of the frequency f of the first reference frequency signal from the integrated control unit 201 via the communication interface unit 131, and generates the first reference frequency signal in accordance with the specification.

[0039] The current measurement unit 112 measures the AC current superimposed on the battery pack 101 by sampling the current of the battery pack 101 using a sampling clock signal from the clock generation unit 113. The current of the battery pack 101 is measured as a voltage drop of a current detection resistive element 106 inserted in a path through which the AC current applied by the AC superimposition unit 104 flows. This voltage drop is proportional to the AC current and therefore means an AC current value. More specifically, the current measurement unit 112 includes an analog-digital converter for measuring the current of the battery pack 101, which is a secondary battery. This analog-digital converter samples the voltage drop of the current detection resistive element 106 using the sampling clock signal from the clock generation unit 113 and converts the sampled voltage drop into a digital signal.

[0040] The clock generating unit 113 generates a sampling clock signal having a higher frequency than the first reference frequency signal and synchronized with the first reference frequency signal. The sampling clock signal is supplied to the current measuring unit 112 and the voltage measuring unit 115. For example, when 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 so as to satisfy the required phase resolution. Therefore, when the measurement frequency is about 5 KHz and the phase resolution is about 1 degree, the sampling clock should be set to about 1.8 MHz, which is 360 times 5 KHz.

[0041] The voltage measurement unit 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 unit 113. More specifically, the voltage measurement unit 115 has the same number of analog-digital converters (ADC0-ADC5) corresponding to the battery cells B0-B5 in the battery pack 101. Each analog-digital converter samples the voltage of a corresponding battery cell among the plurality of battery cells B0-B5 using the sampling clock signal from the clock generation unit 113, and converts the sampled voltage into a digital signal. The voltage measurement unit 115 uses the same sampling clock as the current measurement unit 112, and therefore can achieve highly accurate complex frequency measurement with a minimum phase error between the measurement frequency and the sampling clock.

[0042] The reference voltage generating unit 117 supplies a common reference voltage to the multiple analog-digital converters (ADC0 to ADC5) of the voltage measuring unit 115, the analog-digital converter of the current measuring unit 112, and the analog-digital converter of the temperature measuring unit 120. Specifically, the reference voltage generating unit 117 is a BGR (Band Gap Reference) circuit that generates a constant voltage value that is stable against fluctuations in temperature and power supply voltage, and generates a voltage of about 1.25 V due to the band gap of silicon, for example. Since the multiple analog-digital converters of the voltage measuring unit 115 and the analog-digital converter of the current measuring unit 112 use the same reference voltage, the absolute error of the reference voltage is canceled by the division of the numerator / denominator when calculating the complex impedance. This makes it possible to measure the complex impedance with high accuracy.

[0043] The conversion unit 118b converts the measurement results of the voltage measurement unit 115 and the current measurement unit 112 into real and imaginary components of a complex voltage and a complex current, respectively, by multiplying the measurement results of the voltage measurement unit 115 and the current measurement unit 112 by a first reference frequency signal and a second reference frequency signal. For this purpose, the conversion unit 118b includes the same number of multiplier pairs corresponding to the analog-digital converters (ADC0 to ADC5) of the voltage measurement unit 115, and a corresponding multiplier pair of the analog-digital converter of the current measurement unit 112. Each multiplier pair corresponding to the voltage measurement unit 115 is composed of a multiplier that multiplies the conversion result of the corresponding analog-digital converter (i.e., the sampled digital voltage value) by the first reference frequency signal, and a multiplier that multiplies the conversion result by the second reference frequency signal. The former multiplication result indicates the real component when the sampled voltage is expressed as a complex voltage. The latter multiplication result indicates the real component when the sampled voltage is expressed as a complex voltage. The multiplier pair corresponding to the current measurement unit 112 is composed of a multiplier that multiplies the conversion result of the corresponding analog-to-digital converter (i.e., the sampled digital current value) by a first reference frequency signal, and a multiplier that multiplies the conversion result by a second reference frequency signal. The former multiplication result indicates the real part component when the sampled current is expressed as a complex current. The latter multiplication result indicates the real part component when the sampled current is expressed as a complex current.

[0044] Each of the analog-digital converters (ADC0 to ADC5) may be, for example, a delta-sigma type analog-digital converter. The multiple 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 for the multiple analog-digital converters (ADC0 to ADC5). This makes it possible to reduce measurement errors caused by differences in conversion time (latency) due to differences in the types of analog-digital converters used among the battery cells B0 to B5.

[0045] The integrating unit 118c averages the real and imaginary components of the complex voltage and complex current repeatedly measured by the voltage measuring unit 115 and converted by the converting unit 118b. This averaging also reduces the measurement error of the complex voltage and complex current, and oversampling can improve the resolution (measurement accuracy). This averaging also improves the accuracy of the measurement. More specifically, the integrating unit 118c has the same number of averaging circuit pairs as the multiplier pairs of the converting unit 118b. Each averaging circuit pair is composed of an averaging circuit that averages the real components of the complex voltage or complex current, and an averaging circuit that averages the imaginary components of the complex voltage or complex current. When the battery cell is a lithium ion battery, the internal complex impedance is, for example, several mΩ. If the superimposed AC current is assumed to be 1 A, the change in output voltage is only several mV. On the other hand, the DC output voltage of a lithium-ion battery is approximately 3.4V, so a dynamic range of approximately 4 to 5V is required to measure the voltage using an analog-digital converter connected to a battery cell. In this case, if the complex impedance measurement accuracy requires approximately 8 bits, an analog-digital converter with approximately 18 to 20 effective bits is required, but a high-resolution AD converter consumes a lot of power and has a large area. On the other hand, the internal complex impedance measured to perform electrochemical impedance analysis of a lithium-ion battery is measured in the low frequency range of 0.01 Hz to several tens of KHz, which is almost DC, so complex voltage cannot be measured by AC connection. In the configuration of Figure 1, an AC current is repeatedly applied to separate the complex voltage and complex current into real and imaginary parts and average them, making it possible to increase the resolution by integration through oversampling, so that even an analog-digital converter with a small number of bits (for example, approximately 16 bits) can obtain complex impedance measurement results with 20 to 24 bits of accuracy. If the measurement accuracy of the complex voltage can be improved, it will be possible to reduce the magnitude of the applied AC current, facilitating the measurement of secondary batteries with large capacity and small internal complex impedance.

[0046] The holding unit 118d holds the real and imaginary components of the complex voltage and complex current after averaging. For this purpose, the holding unit 118d includes a number of register pairs equal to the number of battery cells of the assembled battery 101 for holding the complex voltage, and a register pair for holding the complex current. Each register pair for holding the complex voltage includes a register (Re(Vi)) for holding the real component of the complex voltage of the corresponding battery cell, and a register for holding the imaginary component (Im(Vi)). Here, i is an integer between 0 and 5. The register pair for holding the complex current includes a register (Re(I0)) for holding the real component of the complex current of the corresponding assembled battery 101, and a register for holding the imaginary component (Im(I0)).

[0047] The temperature measurement unit 120 measures the temperature of the battery pack 101 using a temperature sensor 107 provided in the battery pack 101. The temperature sensor 107 may be, for example, a thermistor, but may also be a temperature sensor using other elements such as a thermocouple. Specifically, the temperature measurement unit 120 includes an analog-to-digital converter and a temperature calculation unit 121. This analog-to-digital converter samples the voltage of the temperature sensor 107 and converts the sampled voltage into a digital value. The temperature calculation unit 121 calculates a temperature corresponding to the digital voltage from the analog-to-digital converter.

[0048] The communication interface unit 131 is a communication circuit for the battery management circuit 105 to communicate with other battery management circuits 100 or the integrated control unit 201. The communication interface unit 131 is used, for example, to transmit the complex impedance calculated by the holding unit 118d to the integrated control unit 201. The communication performed by the communication interface unit 131 may be wireless communication or wired communication. There is no particular limitation on the communication standard of the communication performed by the communication interface unit 131.

[0049] The integrated control unit 201 specifies the frequency f of the first reference frequency signal to the battery management circuit 100, collects the real and imaginary components stored in the storage unit 118d from the multiple battery management devices 100 via the communication line 132, and calculates the complex impedance of the specified frequency from the real and imaginary components of the collected complex voltages and complex currents. In calculating the impedance, the integrated control unit 201 calculates the AC impedance by dividing each of the complex voltages stored in the storage unit 118d by the complex current. Specifically, the integrated control unit 201 has a division function, and calculates, for example, the AC impedance of the battery cell B0 by dividing the complex voltage indicated by (Re(V0), Im(V0)) by the complex current indicated by (Re(I0), Im(I0)).

[0050] The battery management device 100 is a lower-level CMU (Cell Management Unit) that measures and manages each battery cell. On the other hand, the integrated control unit 201 is a higher-level system BMU (Battery Management Unit) that manages the entire battery pack. The integrated control unit 201 is equipped with an MCU (Micro Control Unit) that can perform large-capacity calculations faster than the battery management device 100, and controls the battery. In the configuration of FIG. 1, the function of the battery management device 100, which is a CMU, is limited to measuring complex voltage and complex current, and the higher-level integrated control unit 201, which has a higher calculation capacity, calculates complex impedance. This makes it unnecessary to install a calculation circuit that calculates complex impedance on the CMU side, which has multiple CMUs, in complex impedance measurement, and simplifies the CMU circuit, making it possible to realize complex impedance measurement at low cost. In addition, by the integrated control unit 201 collecting complex voltages and complex currents, it becomes easier to perform calculations and corrections, such as temperature correction of fluctuations in complex impedance due to measurement temperature, and shortening measurement time by thinning out and interpolating the measurement frequency interval.

[0051] Next, a configuration example of the integrated control unit 201 will be described.

[0052] FIG. 2 is a diagram showing an example of the configuration of the integrated control unit 201 according to the embodiment.

[0053] As shown in the figure, the integrated control unit 201 includes a CPU 31, a memory 32, a communication circuit 33, and a wireless circuit .

[0054] The CPU 31 executes a program stored in the memory 32 .

[0055] The memory 32 stores various programs for managing the multiple battery management devices 100 and various data such as battery state data including the AC impedance of the assembled battery 101 .

[0056] The communication circuit 33 communicates with a plurality of battery management devices 100 daisy-chained by a communication line 132 .

[0057] The wireless circuit 34 wirelessly communicates with the battery management server 301 .

[0058] [Operation] Next, a specific example of the processing performed by the integrated control unit 201 will be described.

[0059] FIG. 3 is a flowchart showing an example of processing by the integrated control unit 201 according to the embodiment.

[0060] 2 shows an example of processing for one battery management unit 100 out of the plurality of battery management units 100. The integrated control unit 201 performs similar processing for the other battery management units 100 in sequence.

[0061] First, the integrated control unit 201 specifies the frequency f of the first reference frequency signal to the battery management unit 100 (S11). As a result, the battery management unit 100 generates a first reference frequency signal of the specified frequency and measures the complex voltage, complex current, and temperature of the assembled battery 101, which is a secondary battery. When these measurements are completed, the integrated control unit 201 acquires data indicating the measured complex voltage, complex current, and temperature of the assembled battery 101 from the battery management unit 100 via the communication line 132 (S12 to S14). Note that instead of acquiring the temperature of the assembled battery 101, the temperature of the secondary battery at the time of measurement may be estimated from the calculated complex impedance, the complex impedance previously converted, and information indicating the temperature of the secondary battery. This estimation is useful for the battery management unit 100 that does not include the temperature sensor 107.

[0062] Next, the integrated control unit 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). The integrated control unit 201 may specify the frequency f of the first reference frequency signal multiple times while changing it, and calculate the change in the complex impedance corresponding to the change in the specified frequency.

[0063] Furthermore, the integrated control unit 201 generates drawing data showing a Cole-Cole plot in which the complex impedance is plotted as a locus on a complex plane (S16). Note that the integrated control unit 201 may generate drawing data showing a Bode diagram in which the complex impedance is converted into magnitude and phase, instead of the drawing data showing the Cole-Cole plot.

[0064] Furthermore, the integrated control unit 201 normalizes the complex impedance by the acquired temperature (or the estimated temperature) (S17). Specifically, the integrated control unit 201 converts the complex impedance according to the acquired temperature into a complex impedance corresponding to a predetermined temperature. Note that the order of steps S16 and S17 may be reversed. In other words, the integrated control unit 201 may generate drawing data after normalization by temperature.

[0065] Next, the integrated control unit 201 calculates element constants of circuit elements such as resistance R and capacitance C that constitute an equivalent circuit model representing the corresponding battery cell based on the complex impedance corresponding to a predetermined temperature (i.e., corrected to a standard temperature different from the measured temperature) (S18).

[0066] Furthermore, the integrated control unit 201 generates measurement information including the complex impedance and the above element constants, and assigns identification information for identifying the corresponding battery cell to the measurement information (S19), and further assigns information indicating the current time and operation time to the measurement information (S20). The integrated control unit 201 transmits the measurement information with the identification information, current time, and operation time assigned as battery state data to the battery management server 301 via the network (S21).

[0067] Next, an example of an equivalent circuit model of a battery cell and its element constants will be described.

[0068] FIG. 4 is an explanatory diagram showing an example of the structure of a battery cell according to an embodiment and an example of an equivalent circuit model. FIG. 4(a) shows a symbol of a battery cell B0. FIG. 4(b) shows a schematic diagram of an example of the structure of the battery cell B0 when it is a lithium ion battery. The battery cell B0 has a negative electrode, a negative electrode material, an electrolyte, a separator, a positive electrode material, and a positive electrode as the premise of the equivalent circuit model. FIG. 4(c) shows an example of an equivalent circuit model of the battery cell B0. This 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 the impedance component of the electrode wire. The resistance component R0 represents the impedance component of the electrolyte. The parallel circuit of the resistance component R1 and the capacitance component C1 represents the impedance component of the negative electrode. The circuit portion consisting of the resistance component R2, the lithium ion diffusion resistance component Zw, and the capacitance component C2 represents the impedance component of the positive electrode. The lithium ion diffusion resistance Zw is known as the Warburg impedance.

[0069] By calculating the element constants of each circuit element constituting such an equivalent circuit model, the state of the battery cell B0 can be estimated. For example, the deterioration state of the battery cell B0 can be estimated based on the change in the element constants over time.

[0070] Next, an example of the complex impedance characteristics of a battery cell will be described.

[0071] FIG. 5A is a Cole-Cole plot diagram showing an example of the complex impedance of a battery cell according to an embodiment. The thick solid lines in (a) and (b) of FIG. 5A show an example of the correct complex impedance without a phase error. The thick dashed line in (a) of FIG. 5A shows an example of the complex impedance when a phase error with a fixed angle occurs. Also, the thick dashed line in (b) of FIG. 5A shows an example of the complex impedance when a phase error with a fixed delay time occurs.

[0072] Cole-Cole plots are also called complex plane diagrams or Nyquist plots. The thick solid lines in (a) and (b) of Figure 5A correspond to the equivalent circuit model in (c) of Figure 4. In the method of calculating the complex impedance of a battery cell by superimposing an AC current, it is generally known that in the case of charge transfer rate-limiting, it is expressed as an equivalent circuit in which resistance and capacitance are arranged in parallel, and in the complex plane it becomes a semicircle. In addition, when the Warburg impedance is included, it is generally known that the semicircle becomes a straight line that rises at a 45-degree angle halfway (near the upper right) as a slope derived from the Warburg impedance.

[0073] When complex impedance is calculated, if there is a phase error in the voltage and current measurement system, it appears as a phase error in the complex impedance. In general, phase errors caused by the measurement system often have frequency characteristics, which becomes a problem when measuring complex impedance at different frequencies. In particular, when plotting the complex impedance at each frequency on a Cole-Cole plot while varying the frequency, each frequency phase error appears as an orthogonal error between the real axis (horizontal axis) and the imaginary axis (vertical axis) on the complex plane of the Cole-Cole plot. This makes it difficult to plot an accurate Cole-Cole plot. However, in the configuration of Figure 1, by measuring the complex voltage and complex current and then calculating the complex impedance, the phase error of the voltage and current measurement system is extremely small, making it possible to plot an accurate Cole-Cole plot. As shown by the thick dashed line in Figure 5A (a), when the angle of the phase error is fixed, the Cole-Cole plot has the characteristic of rotating around the origin. In addition, as shown by the thick dashed line in Figure 5A(b), when the delay time of the phase error is fixed, the Cole-Cole plot rotates only on the high-frequency side and overlaps with the thick solid line on the low-frequency side. In other words, the phase error occurs only on the high-frequency side and not on the low-frequency side.

[0074] Fig. 5B is a Bode plot showing an example of the complex impedance of a battery cell according to an embodiment. The thick solid lines in the upper part of (a) and the upper part of (b) of Fig. 5B show an example of the magnitude of the correct complex impedance with no phase error versus frequency. The thick solid lines in the lower part of (a) and the lower part of (b) of Fig. 5B show an example of the phase θ of the correct complex impedance with no phase error versus frequency.

[0075] The thick dashed line in the lower part of Fig. 5B(a) shows an example of the phase θ of the complex impedance with respect to the frequency when a phase error with a fixed angle occurs. The thick dashed line in the lower part of Fig. 5B(b) shows an example of the phase θ of the complex impedance with respect to the frequency when a phase error with a fixed delay time occurs. The thick solid lines in Fig. 5B(a) and (b) correspond to the equivalent circuit model in Fig. 4(c).

[0076] When complex impedance is plotted as a Bode diagram, which expresses the magnitude and phase while varying the frequency, if there is a phase error in the voltage and current measurement system, it appears as a phase error on the Bode diagram. Therefore, it is difficult to plot an accurate complex impedance as a Bode diagram. However, in the configuration of FIG. 1, the complex voltage and complex current are measured and then the complex impedance is calculated, so that the phase error of the voltage and current measurement system is extremely small, making it possible to plot an accurate Bode diagram. As shown by the thick dashed line in the lower part of FIG. 5B (a), when the angle of the phase error is fixed, the Bode diagram showing the phase with respect to the frequency has the characteristic of moving in parallel. Also, as shown by the thick dashed line in the lower part of FIG. 5B (b), when the delay time of the phase error is fixed, the Bode diagram showing the phase with respect to the frequency has the characteristic of being affected only on the high frequency side and overlapping with the thick solid line on the low frequency side. In other words, the phase error occurs only on the high frequency side, and does not occur on the low frequency side.

[0077] 5A and 5B are also useful for estimating the state of the battery cell. For example, the thick solid line in Fig. 5A is considered to move to the right as the battery cell deteriorates. The thick solid line in the upper part of Fig. 5B is considered to move upward as the battery cell deteriorates.

[0078] Next, the temperature characteristics of the battery cells will be described.

[0079] 6 is a diagram showing an example of the temperature characteristic of the complex impedance of a battery cell according to the embodiment. The diagram shows Cole-Cole plots when the temperatures of the battery cell are 20 degrees, 25 degrees, and 30 degrees. As described above, the complex impedance of a battery cell has temperature dependency, but the effect of the temperature dependency can be reduced by normalizing the complex impedance to a complex impedance corresponding to a predetermined temperature.

[0080] As described above, the battery management circuit 105 can measure the complex impedance of each battery cell of the assembled battery 101 with high accuracy using a simple circuit configuration.

[0081] As described above, the battery management circuit 105 of embodiment 1 is a battery management circuit that manages a secondary battery, and includes a reference signal generating unit 109 that generates a first reference frequency signal and a second reference frequency signal having a phase shifted by 90 degrees from the first reference frequency signal, an AC superposition unit 104 that superposes an AC current having a frequency component of the first reference frequency signal on the secondary battery, a voltage measurement unit 115 that measures the voltage of the secondary battery by sampling at a higher frequency than the first reference frequency signal, a current measurement unit 112 that measures the current of the secondary battery by sampling at a higher frequency than the first reference frequency signal, and a conversion unit 118b that converts the measurement results of the voltage measurement unit 115 and the current measurement unit 112 by the first reference frequency signal and the second reference frequency signal to convert the measurement results into real and imaginary components of a complex voltage and complex current, respectively.

[0082] This makes it possible to measure the complex impedance of the secondary battery with high accuracy using a simple circuit configuration.

[0083] Here, the battery management circuit 105 includes a clock generating unit 113 that generates a synchronized sampling clock signal at a frequency higher than the first reference frequency signal, and the voltage measuring unit 115 and the current measuring unit 112 may perform sampling using the sampling clock signal generated by the clock generating unit 113.

[0084] The clock generating unit 113 may generate one or more sampling clock signals.

[0085] Furthermore, the multiple sampling clock signals may or may not be synchronized with the first reference frequency signal. Even if the sampling clock signals are not synchronized with the first reference frequency signal, as long as the frequencies of the sampling clock signals are sufficiently higher than the first reference frequency signal, the voltage measurement unit 115 and the current measurement unit 112 can measure the voltage and current with high accuracy.

[0086] The voltage measurement unit 115 and the current measurement unit 112 may use the same sampling clock signal or different sampling clock signals. In other words, the sampling signals for voltage measurement and current measurement may be the same sampling clock signal or different sampling clock signals. Even if the sampling clock signals are different, as long as they have a sufficiently higher frequency than the first reference frequency signal, the same measurement as when the same sampling clock signal is used is possible.

[0087] Here, the voltage measurement unit 115 and the current measurement unit 112 repeatedly measure the voltage and current of the secondary battery, and the battery management circuit 105 may include an integration unit 118c that averages the real and imaginary components of the complex voltage and complex current corresponding to the repeated measurements.

[0088] According to this, the resolution of voltage measurement and current measurement can be increased by averaging, and the measurement accuracy can be improved. If the measurement accuracy of complex voltage can be improved, the magnitude of the applied AC current can be reduced, facilitating the measurement of secondary batteries with large capacity and small internal complex impedance.

[0089] Here, the voltage measurement unit 115 may include one or more analog-digital converters for measuring the voltage of the secondary battery, the current measurement unit 112 may include an analog-digital converter for measuring the current of the secondary battery, and the battery management circuit 105 may include a reference voltage circuit 117 that supplies a common reference voltage to the one or more analog-digital converters of the voltage measurement unit 115 and the analog-digital converter of the current measurement unit 112.

[0090] For example, even with an analog-digital converter with a small number of bits (such as about 16 bits), it is possible to obtain complex impedance measurement results with 20 to 24 bits of accuracy. In addition, since the same reference voltage is used for voltage measurement and current measurement, the absolute error of the reference voltage appears in both the numerator and denominator and is cancelled out when calculating complex impedance, i.e., dividing the measured voltage by the measured current. This makes it possible to measure complex impedance with high accuracy.

[0091] Here, the battery pack 101, which is a secondary battery, has multiple battery cells connected in series, and the voltage measurement unit 115 may include one or more analog-to-digital converters, the number of which is the same as the number of battery cells, and measure the voltage of each of the multiple battery cells.

[0092] According to this, the voltage and current measurements of a plurality of battery cells can be performed simultaneously in parallel using the same number of analog-to-digital converters as the number of battery cells, allowing accurate measurements to be made even when there are rapid temperature changes.

[0093] Here, the battery management circuit 105 may be a single semiconductor integrated circuit (BMIC).

[0094] According to this, by implementing the battery management device 100 as an IC, costs can be easily reduced.

[0095] Moreover, the battery management system 200 according to the first embodiment includes the above-mentioned battery management circuit 105 and an integrated control unit 201 that specifies the frequency of the first reference frequency signal to the battery management circuit 100, and the battery management circuit 100 transmits the real and imaginary components of the complex voltage and complex current to the integrated control unit 201, and the integrated control unit 201 calculates the complex impedance of the specified frequency from the real and imaginary components of the transmitted complex voltage and complex current.

[0096] Here, the battery management system 200 includes at least one battery management circuit 105 and a communication line 132 that daisy-chains the integrated control unit 201 and the at least one battery management circuit 105, and the integrated control unit 201 may collect real part components and imaginary part components from the at least one battery management circuit 105 via the communication line 132.

[0097] According to this, the integrated control unit 201 is a higher-level system that manages the entire battery pack, and calculates the complex impedance using the complex voltage and complex current measured by the battery management circuit 105. This simplifies the circuit configuration of the battery management circuit 105 in complex impedance measurement, making it possible to realize it at low cost. In addition, by having the integrated control unit 201 collect the complex voltage and complex current, it becomes easy to perform more advanced correction for measurement errors, measurement temperature variations, and the like.

[0098] Here, the integrated control unit 201 may specify the frequency of the first reference frequency signal multiple times while changing it, and calculate the change in complex impedance corresponding to the change in the specified frequency.

[0099] According to this, it is possible to calculate a change in complex impedance corresponding to a change in frequency under the control of the integrated control unit 201.

[0100] Here, the integrated control unit 201 may generate plot data showing a Cole-Cole plot in which the complex impedance is plotted as a locus on a complex plane.

[0101] Here, the integrated control unit 201 may generate drawing data showing a Bode diagram in which the complex impedance is converted into magnitude and phase.

[0102] According to this, the state (such as the state of deterioration) of a battery cell can be easily estimated using a Cole-Cole plot or Bode plot of a secondary battery.

[0103] Here, the integrated control unit 201 may obtain the temperature of the secondary battery, and convert the complex impedance according to the obtained temperature into a complex impedance corresponding to a predetermined temperature.

[0104] This can reduce the influence of the temperature dependency of the complex impedance of the secondary battery.

[0105] Here, the integrated control unit 201 may estimate the temperature of the secondary battery at the time of measurement from the calculated complex impedance, a complex impedance previously converted, and information indicating the temperature of the secondary battery.

[0106] This makes it possible to estimate the temperature of the secondary battery at the time of measurement even in a battery management device that does not have a temperature sensor.

[0107] Here, the integrated control unit 201 may calculate element constants of circuit elements constituting an equivalent circuit model representing the secondary battery, based on the complex impedance corresponding to a predetermined temperature.

[0108] This enables state estimation using an equivalent circuit model of the secondary battery.

[0109] Here, the integrated control unit 201 may add identification information for identifying the secondary battery to the measurement information including the calculated complex impedance, and transmit the measurement information with the added identification information to a server device via a network.

[0110] This allows the battery management system 200 to manage the batteries in cooperation with a server device (battery management server 301).

[0111] Here, the integrated control unit 201 may receive battery information including a result of estimating the state of the secondary battery based on the measurement information from the server device.

[0112] (Embodiment 2) Next, a configuration example of a battery management network in which the battery management server 301 is a so-called cloud server device will be described.

[0113] 7 is a block diagram showing an example of the configuration of a battery management network according to an embodiment. The battery management network in the figure includes an automobile 400 and a cloud system 300.

[0114] The automobile 400 includes a battery management system 200 and a motor 401 .

[0115] The battery management system 200 has already been described in the first embodiment. The integrated control unit 201 in Fig. 7 communicates with a server device of the cloud system 300 via a wireless circuit 34. Note that a relay device may be interposed between the wireless circuit 34 and the server device 301.

[0116] The cloud system 300 is a group of server devices on a network including a server device 301. The battery management server 301 is a server device that is located at a location separate from the battery management system 200. The server device 301 is a so-called cloud server.

[0117] FIG. 8 is a sequence diagram illustrating an example of a process performed by the battery management network according to the embodiment.

[0118] In embodiment 1, the battery management system 200 of the automobile 400 adds identification information for identifying the secondary battery to the measurement information including the calculated complex impedance, and transmits the measurement information with the added identification information as battery status data to the server device 301 via the network (S21).

[0119] The battery management server 301 estimates the state of the secondary battery based on the battery state data (S22), and generates battery information including the estimation result. The state of the secondary battery includes, for example, the battery's charge state, degradation state, operation history, etc. Furthermore, the server device 301 transmits the battery information, which is the result of the state estimation, to the automobile 400 (S23).

[0120] Furthermore, the battery management system 200 performs block issuing to transmit block data including the measurement information or the battery information to the server device 301 (S24).

[0121] The battery management server 301 performs a sharing process to share the issued block data with the cloud server device group (S25). The sharing process may be, for example, a process called a mining process. The cloud server device group shares a collection of block data as a blockchain, and performs a process (i.e., a mining process) to link the block data issued by the automobile 400 to the blockchain, thereby performing state estimation and deterioration diagnosis.

[0122] After completing the process of linking to the blockchain, the battery management server 301 transmits data indicating block approval to the automobile 400 (S26).

[0123] As described above, the server device 301 according to the second embodiment is included in the group of server devices that share battery information on a network.

[0124] This makes it possible to implement cloud battery telematics. Here, cloud battery telematics refers to battery management as part of an information service that makes various information available, using a cloud server system and a battery management system 200 that is installed in an automobile and can be connected to a network.

[0125] Here, the integrated control unit 201 may transmit block data including the measurement information or the battery information to a server device, thereby causing a collection of block data to be shared by a group of server devices.

[0126] According to this, block data including measurement information or battery information can be shared and managed by a group of server devices. For example, if the group of server devices manages the block data using blockchain technology, the battery information can be managed securely.

[0127] (Modification) Next, a modification of the battery management systems 200 according to the first and second embodiments will be described.

[0128] FIG. 9 is a block diagram showing a configuration example of a battery management system and a battery management server according to a modified example.

[0129] This figure differs from FIG. 1 in that it includes a battery management circuit 105A (first semiconductor integrated circuit) and a battery management circuit 105B (second semiconductor integrated circuit) instead of the battery management circuit 105. The following mainly describes the differences. The battery management circuit 105, which is a one-chip semiconductor integrated circuit, is divided into two semiconductor integrated circuits. Furthermore, the circuit configurations of the current measurement unit 112 and the voltage measurement unit 115 are simplified.

[0130] The battery management circuit 105A differs from the battery management device 100 mainly in that it has a measurement unit 122 that measures voltage, a first reference signal generating unit that is the reference signal generating unit 109, and a first signal synchronizing unit 119.

[0131] The battery management circuit 105B includes a current measurement unit 112, a first signal synchronization unit 119, a second reference signal generation unit equivalent to the reference signal generation unit 109, and a second synchronization unit 119.

[0132] The first signal synchronizer controls the first reference signal generator so as to match the phase of the first reference frequency signal in the battery management circuit 105A with the phase of the first reference frequency signal in the battery management circuit 105B.

[0133] The second signal synchronizer controls the second reference signal generator so as to match the phase of the first reference frequency signal in the battery management circuit 105A with the phase of the first reference frequency signal in the battery management circuit 105B.

[0134] The measurement unit 122 includes a multiplexer (MUX) that selects one battery cell from the multiple battery cells, an analog-to-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-to-digital converter. The measurement unit 122 sequentially selects one battery cell from the multiple battery cells and measures its voltage. The measurement unit 122 also measures the temperature.

[0135] As described above, in the battery management system 200 according to 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 the plurality of battery cells, and the one or more analog-digital converters of the voltage measurement unit 115 are a single analog-digital converter that measures the voltage of the battery cell selected by the multiplexer.

[0136] According to this, a single analog-to-digital converter can sequentially measure the voltages and currents of a plurality of battery cells, making it possible to simplify the circuit configuration.

[0137] Here, the battery management circuit is composed 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 has a voltage measurement unit 115, a first reference signal generating unit which is reference signal generating unit 109, and a first signal synchronization unit 119, the second semiconductor integrated circuit has a current measurement unit 112, the first signal synchronization unit 119, a second reference signal generating unit equivalent to reference signal generating unit 109, and the second signal synchronization unit 119, the first signal synchronization unit controls the first reference signal generating unit so as to align the phase of a first reference frequency signal inside the first semiconductor integrated circuit with that inside the second semiconductor integrated circuit, and the second signal synchronization unit may control the second reference signal generating unit so as to align the phase of a first reference frequency signal inside the first semiconductor integrated circuit with that inside the second semiconductor integrated circuit.

[0138] According to this, if the entire battery management system 200 is provided with only one second semiconductor integrated circuit, current measurement can be performed at one location in common to the multiple assembled batteries 101. In other words, since there is no need to measure current individually for the multiple assembled batteries 101, the circuit configuration can be simplified. Moreover, the first and second signal synchronizers align the phase of the first reference frequency signal in the first semiconductor integrated circuit and the first reference frequency signal in the second semiconductor integrated circuit, so that measurement can be performed with high accuracy.

[0139] (Other embodiments) Although the embodiments have been described above, the present disclosure is not limited to the above-described embodiments.

[0140] For example, in the above embodiment, a battery management system that manages batteries used in automobiles such as EVs has been described, but the battery management system may manage batteries for any purpose.

[0141] In addition, the circuit configurations described in the above embodiments are merely examples, and the present disclosure is not limited to the above circuit configurations. In other words, the present disclosure also includes circuits that can realize the characteristic functions of the present disclosure, similar to the above circuit configurations. For example, the present disclosure also includes a circuit in which an element such as a switching element (transistor), a resistive element, or a capacitive element is connected in series or parallel to a certain element, as long as the circuit configuration can realize the same functions as the above circuit configuration.

[0142] In the above embodiment, the components included in the integrated circuit are realized by hardware. However, some of the components included in the integrated circuit may be realized by executing a software program suitable for the components. Some of the components included in the integrated circuit may be realized by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

[0143] In the above-described embodiment, the process executed by a specific processing unit may be executed by another processing unit. In the operations described in the above-described embodiment, the order of multiple processes may be changed, or multiple processes may be performed in parallel.

[0144] In addition, the present disclosure also includes forms obtained by applying various modifications to each embodiment that a person skilled in the art may conceive, or forms realized by arbitrarily combining the components and functions of each embodiment within the scope that does not deviate from the spirit of the present disclosure. [Industrial Applicability]

[0145] The present disclosure is applicable to a battery management circuit, a battery management system, and a battery management network that manages a secondary battery. [Explanation of symbols]

[0146] 31 CPU 32 Memory 33 Communication Circuits 34 Radio circuit 100, 100A, 100B battery management device 101 Battery pack 104 AC superposition section 105, 105A, 105B battery management circuit 106 Detector resistor 107 Temperature Sensor 109 Reference signal generator 110 Reference Frequency Generator 111 Phase shifter 112 Current measurement section 113 Clock Generation Unit 115 Voltage measurement section 117 Reference voltage generator 118b conversion unit 118c Integral section 118d Holding part 119 Synchronization Department 120 Temperature measurement section 121 Temperature calculation section 122 Measurement section 131 Communication interface section 132 Communication Line 200 Battery Management System 201 Integrated Control Unit 300 Cloud System 301 Battery Management Server 302 Communication Line 400 Automobiles 401 Motor B0~B5 Battery cells

Claims

1. A battery management circuit for managing a secondary battery, a reference signal generating unit that generates a first reference frequency signal and a second reference frequency signal having a phase different from that of the first reference frequency signal; an AC superposition unit that superposes an AC current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement unit that measures the voltage of the secondary battery by sampling at a frequency higher than the first reference frequency signal; a current measuring unit that measures a current of the secondary battery by sampling at a frequency higher than the first reference frequency signal; a conversion unit that converts the measurement results of the voltage measurement unit and the current measurement unit 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, the voltage measurement unit and the current measurement unit repeatedly measure the voltage and current of the secondary battery, The battery management circuit includes an integrator that averages real and imaginary components of the complex voltage and the complex current corresponding to repeated measurements. Battery management circuit.

2. the voltage measurement unit includes one or more analog-to-digital converters for measuring the voltage of the secondary battery; the current measurement unit includes an analog-to-digital converter for measuring a current of the secondary battery, The battery management circuit includes a reference voltage circuit that supplies a common reference voltage to the one or more analog-to-digital converters of the voltage measurement unit and the analog-to-digital converter of the current measurement unit.

2. The battery management circuit of claim 1.

3. the secondary battery has a plurality of battery cells connected in series; The voltage measurement unit includes, as the one or more analog-to-digital converters, the same number of analog-to-digital converters as the number of battery cells, and measures the voltage of each of the plurality of battery cells.

3. The battery management circuit of claim 2.

4. A battery management circuit for managing a secondary battery, a reference signal generating unit that generates a first reference frequency signal and a second reference frequency signal having a phase different from that of the first reference frequency signal; an AC superposition unit that superposes an AC current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measurement unit that measures the voltage of the secondary battery by sampling at a frequency higher than the first reference frequency signal; a current measuring unit that measures a current of the secondary battery by sampling at a frequency higher than the first reference frequency signal; a conversion unit that converts the measurement results of the voltage measurement unit and the current measurement unit 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, the secondary battery has a plurality of battery cells connected in series; the battery management circuit includes a multiplexer that selects one battery cell from the plurality of battery cells; the voltage measurement unit includes one or more analog-to-digital converters for measuring the voltage of the secondary battery; The one or more analog-to-digital converters of the voltage measurement unit are a single analog-to-digital converter that measures the voltage of the battery cell selected by the multiplexer. Battery management circuit.

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

6. the battery management circuit is composed of a first semiconductor integrated circuit and a second semiconductor integrated circuit; the first semiconductor integrated circuit includes the voltage measurement unit, a first reference signal generating unit that is the reference signal generating unit, and a first signal synchronizing unit, the second semiconductor integrated circuit includes the current measuring unit, a first signal synchronizing unit, a second reference signal generating unit equivalent to the reference signal generating unit, and a second signal synchronizing unit; the first signal synchronization unit controls the first reference signal generation unit so as to match a phase between the first reference frequency signal in the first semiconductor integrated circuit and the first reference frequency signal in the second semiconductor integrated circuit; The second signal synchronization unit controls the second reference signal generation unit so as to match the phase of the first reference frequency signal in the first semiconductor integrated circuit with the phase of the first reference frequency signal in the second semiconductor integrated circuit. The battery management circuit according to any one of claims 1 to 4.

7. The second reference frequency signal has a phase in quadrature with the first reference frequency signal. The battery management circuit according to any one of claims 1 to 6.

8. A battery management circuit according to any one of claims 1 to 7; an integrated control unit 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 the complex voltage and the complex current to the integrated control unit; The integrated control unit calculates a complex impedance at a specified frequency from real and imaginary components of the transmitted complex voltage and complex current. Battery management system.

9. At least one of the battery management circuits; a communication line that daisy-chains the integrated control unit and the at least one battery management circuit, The integrated control unit collects the real part component and the imaginary part component from the at least one battery management circuit via the communication line. The battery management system according to claim 8.

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

11. The integrated control unit generates plot data showing a Cole-Cole plot in which complex impedance is plotted as a locus on a complex plane. The battery management system of claim 10.

12. The integrated control unit generates drawing data showing a Bode diagram in which complex impedance is converted into magnitude and phase. The battery management system of claim 10.

13. The integrated control unit acquires a temperature of the secondary battery, and converts the complex impedance into a complex impedance corresponding to a predetermined temperature in accordance with the acquired temperature. The battery management system according to any one of claims 8 to 12.

14. a battery management circuit for managing a secondary battery, the battery management circuit comprising: a reference signal generating unit that generates a first reference frequency signal and a second reference frequency signal having a phase different from that of the first reference frequency signal; an AC superimposing unit that superimposes an AC current having a frequency component of the first reference frequency signal on the secondary battery; a voltage measuring unit that measures a voltage of the secondary battery by sampling at a frequency higher than that of the first reference frequency signal; a current measuring unit that measures a current of the secondary battery by sampling at a frequency higher than that of the first reference frequency signal; and a conversion unit that converts the measurement results into real and imaginary components of a complex voltage and a complex current by multiplying the measurement results of the voltage measuring unit and the current measuring unit by the first and second reference frequency signals; an integrated control unit 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 the complex voltage and the complex current to the integrated control unit; The integrated control unit calculates a complex impedance of a specified frequency from a real part component and an imaginary part component of each of the transmitted complex voltage and complex current, and estimates the temperature of the secondary battery at the time of measurement from the calculated complex impedance, a complex impedance previously converted, and information indicating the temperature of the secondary battery. Battery management system.

15. The integrated control unit calculates element constants of circuit elements constituting an equivalent circuit model representing the secondary battery based on the complex impedance corresponding to the predetermined temperature. The battery management system of claim 13.

16. The integrated control unit adds identification information for identifying the secondary battery to measurement information including the calculated complex impedance, and transmits the measurement information with the added identification information to a server device via a network. The battery management system according to any one of claims 8 to 15.

17. The integrated control unit receives battery information including a result of estimating a state of the secondary battery based on the measurement information from the server device. The battery management system of claim 16.

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

19. The integrated control unit transmits block data including the measurement information or the battery information to the server device, thereby causing the server device group to share the collection of block data. The battery management system of claim 18.

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

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