Battery monitoring system and battery monitoring method

Abstract

A battery monitoring system (100) comprises: a drive control unit (23) that applies a first pulse current to a battery (B1) and applies a second pulse current in the direction opposite from the first pulse current to a battery (B2); a voltage measurement unit (20) that measures a first complex voltage of the battery (B1) and a second complex voltage of the battery (B2); a current measurement unit (21) that measures a first complex current flowing through the battery (B1) and a second complex current flowing through the battery (B2); an impedance computation unit (201) that measures a first complex impedance of the battery (B1) on the basis of the first complex current and the first complex voltage, and measures a second complex impedance of the battery (B2) on the basis of the second complex current and the second complex voltage; and an AC detection unit (22) that calculates a complex current flowing through a load (3) on the basis of the first complex voltage and the second complex voltage.

Description

Battery Monitoring System and Battery Monitoring Method

[0001] The present disclosure relates to a battery monitoring system and a battery monitoring method for monitoring the states such as voltage, current, and temperature of secondary batteries such as lithium-ion batteries.

[0002] In Patent Document 1, an alternating current is supplied to a battery pack composed of a plurality of batteries, and the voltages and currents of the plurality of batteries to which the alternating current is supplied are multiplied and integrated by sine waves and cosine waves having a phase difference of 90° from each other to be converted into complex numbers, and complex voltages and complex currents are measured, that is, a technique for measuring the complex impedance of a battery is disclosed.

[0003] International Publication No. 2020 / 003841

[0004] Since the load current flowing from the battery pack to the load is a large current, in an in-vehicle system, generally, the resistance value of the current detection resistor for detecting the load current is about 10 to 100 μΩ. On the other hand, the resistance value of the current detection resistor for measuring the complex impedance is about 100 mΩ, which is sufficiently large with respect to the current for measuring the complex impedance in order to ensure the measurement accuracy. Since the voltage drop and heat generation in the current detection resistor for measuring the complex impedance are large, as in the technique disclosed in Patent Document 1, the current detection resistor is arranged in a path different from the path through which the load current flows. When the electric vehicle is stopped, no load current flows and the measurement result of the complex impedance is not affected by the load current. However, when the electric vehicle is running or charging, a load current flows, and the measurement result of the complex impedance is the result of adding the voltage due to the load current having the same frequency component as the measurement frequency, and an error occurs in the measurement result of the complex impedance.

[0005] Therefore, the present disclosure provides a battery monitoring system and the like that can suppress the occurrence of an error in the measurement result of the complex impedance.

[0006] The battery monitoring system according to this disclosure is a battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; and a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack. The system includes a current measuring unit, a first current measuring unit that measures a first complex current based on the detection result of the first current detector, a second current measuring unit that measures a second complex current based on the detection result of the second current detector, an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage, and a load current detection unit that calculates the complex current flowing to a load to which power is supplied from the first battery pack and the second battery pack based on the first complex voltage and the second complex voltage.

[0007] The battery monitoring system according to this disclosure is a battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that selectively applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measuring unit for measuring the first complex current based on the output of the first current detector; and the second The system includes: a second current measuring unit that measures a second complex current based on the output of a current detector; an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection unit that calculates the complex current flowing to a load supplied with power from the first and second battery packs based on the second complex voltage when the first pulse current is applied to the first battery pack by the current application circuit, and calculates the complex current flowing to the load based on the first complex voltage when the second pulse current is applied to the second battery pack by the current application circuit.

[0008] The battery monitoring system according to this disclosure is a battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and, based on the detection result of the first current detector, the first The system includes: a first current measuring unit for measuring a complex current; a second current measuring unit for measuring a second complex current based on the detection result of the second current detector; an impedance calculation unit for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and for measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection unit for calculating the error in the first complex voltage caused by the complex current flowing through a load to which power is supplied from the first and second battery packs, based on the second complex voltage, and for calculating the error in the second complex voltage caused by the complex current flowing through the load, based on the first complex voltage.

[0009] The battery monitoring method according to this disclosure is a battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and applying a second pulse current of the same predetermined measurement frequency to the second battery pack in the opposite direction to the first pulse current; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; and a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack. The method includes: a constant step; a first current measurement step for measuring a first complex current based on the detection result in the first current detection step; a second current measurement step for measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step for calculating the complex current flowing to a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

[0010] The battery monitoring method according to this disclosure is a battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, and comprises: a current application step of selectively applying a first pulse current of a predetermined measurement frequency to the first battery pack and applying a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and a first current measurement step of measuring a first complex current based on the detection result in the first current detection step. The method includes: a constant step; a second current measurement step for measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step for calculating the complex current flowing through a load to which power is supplied from the first and second battery packs based on the second complex voltage when the first pulse current is applied to the first battery pack in the current application step, and calculating the complex current flowing through the load based on the first complex voltage when the second pulse current is applied to the second battery pack in the current application step.

[0011] The battery monitoring method according to this disclosure is a battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and applying a second pulse current of the same predetermined measurement frequency to the second battery pack in the opposite direction to the first pulse current; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and based on the detection result in the first current detection step The method includes: a first current measurement step for measuring a first complex current; a second current measurement step for measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and for measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection step for calculating the error in the first complex voltage caused by the complex current flowing through the load to which power is supplied from the first battery pack and the second battery pack, based on the second complex voltage, and for calculating the error in the second complex voltage caused by the complex current flowing through the load, based on the first complex voltage.

[0012] These comprehensive or specific embodiments may be implemented as a system, method, integrated circuit, computer program, or recording medium such as a computer-readable CD-ROM, or as any combination of a system, method, integrated circuit, computer program, and recording medium.

[0013] According to one aspect of this disclosure, a battery monitoring system, etc., can suppress errors in the measurement results of complex impedance.

[0014] This is a configuration diagram showing an example of a battery monitoring system according to Embodiment 1. This is a circuit configuration diagram showing an example of a voltage measurement unit, current measurement unit, and AC detection unit of a battery monitoring system according to Embodiment 1. This is a circuit configuration diagram showing an example of a drive control unit according to Embodiment 1. This is a timing chart showing an example of the operation of the drive control unit according to Embodiment 1. This is a flowchart showing an example of the operation of a battery monitoring system according to Embodiment 1. This is a configuration diagram showing an example of a battery monitoring system according to Embodiment 2. This is a flowchart showing an example of the operation of a battery monitoring system according to Embodiment 2. This is a flowchart showing an example of a battery monitoring method according to another embodiment

[0015] The embodiments will be described in detail below with reference to the drawings.

[0016] The embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure.

[0017] (Embodiment 1) The battery monitoring system according to Embodiment 1 will be described below.

[0018] Figure 1 is a configuration diagram showing an example of a battery monitoring system 100 according to Embodiment 1. In addition to the battery monitoring system 100, Figure 1 also shows batteries B1 and B2 and a load 3.

[0019] The battery monitoring system 100 includes an impedance measuring device 1 and a higher-level system 200. The impedance measuring device 1 is a device that measures the complex impedance of batteries B1 and B2 connected in series using EIS (Electrochemical Impedance Spectroscopy). Battery B1 is an example of a first battery pack, and battery B2 is an example of a second battery pack. As shown in Figure 2, which will be described later, batteries B1 and B2 are battery packs composed of multiple batteries connected in series, respectively. For example, batteries B1 and B2 are rechargeable secondary batteries such as lithium-ion batteries, and battery B1 is located on the higher potential side than battery B2. The higher-level system 200 includes an impedance calculation unit 201, which has the function of calculating complex impedance.

[0020] Load 3 is a load that receives power from batteries B1 and B2, and changes the input and output currents of batteries B1 and B2. For example, load 3 is an inverter circuit that controls a motor driven by batteries B1 and B2, installed in an electric vehicle, or a charger that supplies charging current to batteries B1 and B2.

[0021] The impedance measuring device 1 includes an inductor 14 that stores or releases electrical energy, a switching circuit consisting of a plurality of switching elements that intermittently transfer electrical energy between battery B1 and battery B2 via the inductor 14, a current detection means for detecting the current of battery B1 and the current of battery B2, and a drive measurement circuit 2. The drive measurement circuit 2 may be provided separately from the impedance measuring device 1. Similarly, in each embodiment described later, the impedance measuring device and the drive measurement circuit may be provided separately.

[0022] The switching circuit includes a first switching element 11 that forms a first loop with the battery B1 and the inductor 14, and a second switching element 12 that forms a second loop with the battery B2 and the inductor 14. For example, the switching circuit includes a current interruption means 13 connected in series with the inductor 14. For example, the current detection means includes a detection resistor 15 connected between the battery B1 and the first switching element 11, and a detection resistor 16 connected between the battery B2 and the second switching element 12. The detection resistor 15 is an example of a first current detector that detects the current flowing through the battery B1, and the detection resistor 16 is an example of a second current detector that detects the current flowing through the battery B2. By detecting the current flowing through the detection resistor 15, the current of the battery B1 can be detected, and by detecting the current flowing through the detection resistor 16, the current of the battery B2 can be detected.

[0023] The first switching element 11 and the second switching element 12 are, for example, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The drain of the first switching element 11 is connected to the positive terminal of battery B1, the source of the first switching element 11 is connected to the drain of the second switching element 12, and the source of the second switching element 12 is connected to the negative terminal of battery B2. The series circuit of the current interruption means 13 and the inductor 14 is connected between the connection point between battery B1 and battery B2 and the connection point between the first switching element 11 and the second switching element 12. For example, the detection resistor 15 is connected between the positive terminal of battery B1 and the drain of the first switching element 11 to detect the charge / discharge current I1 of battery B1. For example, the detection resistor 16 is connected between the negative terminal of battery B2 and the source of the second switching element 12 to detect the charge / discharge current I2 of battery B2.

[0024] The first switching element 11 and the second switching element 12 are switching elements that conduct current when a voltage is applied to the control terminal (gate), and conduct current in the reverse direction (opposite to the arrows of currents I1 and I2 shown in Figure 1) by, for example, a body diode, and are represented as field-effect transistors as an example. In addition, the current interruption means 13 conducts and interrupts current in both directions, and is usually configured by connecting two field-effect transistors facing each other, but to avoid making the diagram complicated, it is represented as a switch circuit symbol.

[0025] The drive measurement circuit 2 is a circuit for controlling the impedance measuring device 1 (specifically, the switching circuit provided by the impedance measuring device 1), and includes a voltage measurement unit 20, a current measurement unit 21, an AC detection unit 22, and a drive control unit 23.

[0026] The voltage measurement unit 20 measures the voltage of battery B1 and the voltage of battery B2. Specifically, the voltage measurement unit 20 measures the first complex voltage of each of the multiple first batteries constituting battery B1, and measures the second complex voltage of each of the multiple second batteries constituting battery B2. The voltage measurement unit 20 is an example of a first voltage measurement unit and a second voltage measurement unit. Note that the battery voltage measured by the voltage measurement unit 20 may be the busbar voltage.

[0027] The current measuring unit 21 measures the current of battery B1 and the current of battery B2. Specifically, the current measuring unit 21 measures a first complex current based on the detection result of the detection resistor 15, and measures a second complex current based on the detection result of the detection resistor 16. The current measuring unit 21 is an example of the first current measuring unit and the second current measuring unit. The current measuring unit 21 measures the current I1 flowing from battery B1 based on the detection voltage Vc1 of the detection resistor 15, and measures the current I2 flowing from battery B2 based on the detection voltage Vc2 of the detection resistor 16.

[0028] The AC detection unit 22 receives a measurement instruction signal containing measurement frequency information from the higher-level system 200. According to the measurement instruction signal, it transmits an enable signal EN and a control signal Vs to the drive control unit 23, and also transmits information necessary for calculating the complex impedance (voltage information from the voltage measurement unit 20 and current information from the current measurement unit 21) to the higher-level system 200. Furthermore, the AC detection unit 22 calculates the complex current flowing through the load 3 based on the first and second complex voltages. The AC detection unit 22 is an example of a load current detection unit. Details of the AC detection unit 22 will be described later.

[0029] The drive control unit 23 drives the first switching element 11 and the second switching element 12 based on the enable signal EN and control signal Vs from the AC detection unit 22. Details of the drive control unit 23 will be described later.

[0030] The impedance calculation unit 201 measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage.

[0031] The higher-level system 200 only needs to have computing capabilities such as a CPU, for example, an MCU (Micro Control Unit) or an ECU (Electronic Control Unit).

[0032] Next, we will explain the details of the configuration of the AC detection unit 22.

[0033] Figure 2 is a circuit diagram showing an example of a voltage measurement unit 20, a current measurement unit 21, and an AC detection unit 22 of a battery monitoring system 100 according to Embodiment 1. Figure 2 mainly shows the internal configuration of the voltage measurement unit 20, the current measurement unit 21, and the AC detection unit 22. In Figure 2, battery B1 consists of a series configuration of multiple first batteries, battery B2 consists of a series configuration of multiple second batteries, and the voltage measurement unit 20 is shown to measure the voltage of each individual battery. Both the voltage measurement unit 20 and the current measurement unit 21 have an analog-to-digital converter (hereinafter abbreviated as ADC) that converts the detected voltage into a digital signal, and the voltage information from the voltage measurement unit 20 and the current information from the current measurement unit 21 are transmitted to the AC detection unit 22 as digital values. Each ADC measures the voltage and current of batteries B1 and B2 at the sampling frequency of the clock signal CK, which will be described later.

[0034] As shown in Figure 2, for example, the AC detection unit 22 includes a signal generation unit 220, a conversion unit 221, an integration unit 222, a holding unit 223, and a communication unit 224.

[0035] The signal generation unit 220 outputs a first reference frequency signal with frequency f according to a measurement command from the higher-level system 200, a second reference frequency signal having a phase orthogonal to the first reference frequency signal, and a clock signal CK to the ADCs of the voltage measurement unit 20 and the current measurement unit 21. The first reference frequency signal is a sine wave sin, and the second reference frequency signal is a cosine wave cos. The clock signal CK is a signal with a higher frequency than the first reference frequency signal and is synchronized with the first reference frequency signal.

[0036] The conversion unit 221 has a multiplier pair corresponding to each ADC, and each multiplier pair multiplies each digital value from each ADC by a first reference frequency signal sin and a second reference frequency signal cos, thereby converting each digital value into the real and imaginary components of a complex voltage and a complex current, respectively. The result of multiplication with the first reference frequency signal sin shows the real component when the sampled voltage is expressed as a complex voltage. The result of multiplication with the second reference frequency signal cos shows the imaginary component when the sampled voltage is expressed as a complex voltage.

[0037] The integrating unit 222 is equipped with the same number of averaging circuit pairs as the multiplier pairs of the conversion unit 221, and averages the real and imaginary components of the complex voltage and complex current, which are repeatedly measured and converted by the conversion unit 221. This averaging reduces the measurement error of the complex voltage and complex current, and oversampling improves the resolution (measurement accuracy). As a result, even with an ADC with a small number of bits (for example, around 16 bits), it becomes possible to obtain measurement results of complex impedance with an accuracy of 20 to 24 bits.

[0038] The holding unit 223 holds the real and imaginary components of the complex voltage and complex current after the averaging process. Each register pair for holding the complex voltage consists of a register Re that holds the real component of the complex voltage and complex current of the corresponding battery cell, and a register Im that holds the imaginary component.

[0039] The communication unit 224 is a communication circuit for communicating with the higher-level system 200. It transmits data stored in the holding unit 223 to the higher-level system 200 and is used to receive measurement instruction signals from the higher-level system 200 (operation instructions to the drive control unit 23 and information on the frequency f of the first reference frequency signal). The communication performed by the communication unit 224 may be wireless communication or wired communication, and there are no particular limitations on the communication standard.

[0040] Next, we will describe the details of the configuration of the drive control unit 23.

[0041] Figure 3 is a circuit diagram showing an example of a drive control unit 23 according to Embodiment 1. Figure 3 shows the internal configuration of the drive control unit 23.

[0042] As shown in Figure 3, the oscillator 230 outputs a reference clock CK0 that sets the switching period, and a clock CK1 that is delayed by the maximum ON period of the first switching element 11 and the second switching element 12 from the reference clock CK0. Embodiment 1 shows an example in which these clock signals are generated by the oscillator 230 of the drive control unit 23, but these clock signals may be received from a higher-level system 200 or the like, or the clock signal CK of the AC detection unit 22 may be used, or these clock signals may be signals synchronized with the clock signal CK.

[0043] Reference voltage source 231 generates a threshold voltage Vr1, reference voltage source 232 generates a threshold voltage Vr2, comparator 233 compares the detected voltage Vc1 with the threshold voltage Vr1, and comparator 234 compares the detected voltage Vc2 with the reference voltage Vr2. In this disclosure, an example is shown in which these threshold voltages are generated inside the drive control unit 23, but these threshold voltages may be supplied from a higher-level system 200 or the like, or these threshold voltages may be made variable by instructions from the higher-level system 200 as described later.

[0044] The clock CK1, the output of comparator 233, and the output of comparator 234 are input to OR circuit 235. The reference clock CK0 sets SR latch 236, and the output of OR circuit 235 resets SR latch 236. The outputs Q and NQ of SR latch 236 are input to switch circuits 237 and 238. The control signal Vs from AC detection unit 22 is a signal that switches between high and low depending on the phase of the first reference frequency signal. Since the first reference frequency signal is a signal of a predetermined measurement frequency (frequency f) according to a measurement command from the higher-level system 200, the control signal Vs is a signal of frequency f. When the control signal Vs is at a high level, switch circuit 237 selects and outputs output Q of SR latch 236, and switch circuit 238 selects and outputs output NQ. When the control signal Vs is at a low level, switch circuit 237 selects and outputs output NQ of SR latch 236, and switch circuit 238 selects and outputs output Q. The output of switch circuit 237 becomes a signal to drive the first switching element 11, and the output of switch circuit 238 becomes a signal to drive the second switching element 12.

[0045] Since the abnormality detection circuit 239 is not the gist of the present application, detailed description and illustration thereof are omitted. However, when the current value or voltage value of each battery detected by the AC detection unit 22, or the temperature of each battery detected by a temperature sensor (not shown) shows an abnormal value, the abnormality detection circuit 239 outputs an abnormal signal Fail of H level. The abnormal signal Fail is logically inverted by the inverter 240 and input to the AND circuit 241 together with the enable signal EN. The output of the AND circuit 241 is the drive signal V13 of the current blocking means 13. When the drive signal V13 is at H level, the current blocking means 13 conducts, and when it is at L level, it blocks. The output of the switch circuit 237 and the drive signal V13 are input to the AND circuit 242, and the drive signal Vg1 is output from the AND circuit 242. The output of the switch circuit 238 and the drive signal V13 are input to the AND circuit 243, and the drive signal Vg2 is output from the AND circuit 243. That is, if there is no abnormality and there is a measurement instruction from the upper system 200, the drive signal V13 conducts the current blocking means 13 to electrically connect the inductor 14 to the first switching element 11 and the second switching element 12, and the first switching element 11 and the second switching element 12 are alternately driven on and off.

[0046] In addition, in order that the first switching element 11 and the second switching element 12 are not in the on state at the same time, a dead time in which the normal drive signal Vg1 and the drive signal Vg2 are both off at the same time is provided. Although not shown, it is assumed here that a delay time corresponding to the dead time is provided at the rising edge of each drive signal.

[0047] Next, the details of the operation of the drive control unit 23 will be described.

[0048] FIG. 4 is a timing chart showing an example of the operation of the impedance measurement device 1 according to the first embodiment. FIG. 4 is a timing chart showing the operation of the main part of the drive control unit 23, and shows a reference clock CK0, a clock CK1, a control signal Vs, a drive signal Vg1, a detection voltage Vc1, a drive signal Vg2, and a detection voltage Vc2. Although not shown, the enable signal EN is at the H level and the abnormal signal Fail is at the L level. The detection voltage Vc1 corresponds to the current I1 flowing through the battery B1 and the first switching element 11, and the detection voltage Vc2 corresponds to the current I2 flowing through the battery B2 and the second switching element 12. For example, the threshold voltage Vr1 and the threshold voltage Vr2 may be the same voltage, and in FIG. 4, the threshold voltages Vr1 and Vr2 are shown as the threshold voltage Vr. Hereinafter, using FIG. 4, the operation in which a high-frequency current pulse flows through the batteries B1 and B2 with high efficiency by the drive control unit 23 of the impedance measurement device 1 according to the first embodiment will be described.

[0049] First, as shown on the left side of FIG. 4, the operation of the drive control unit 23 at times t0 to t2 when the control signal Vs is at the H level will be described. At times t0 to t2, since the control signal Vs is at the H level, the output Q of the SR latch 236 is output as the drive signal Vg1 of the first switching element 11, and the output NQ of the SR latch 236 is output as the drive signal Vg2 of the second switching element 12.

[0050] At time t0, when the reference clock CK0 rises, the SR latch 236 is set, the output Q, that is, the drive signal Vg1 rises, and the output NQ, that is, the drive signal Vg2 falls. The first switching element 11 is turned on and conducts by the drive signal Vg1, and the current I1 flows through the first loop from the positive electrode of the battery B1 to the negative electrode of the battery B1 via the first switching element 11, the inductor 14, and the current blocking means 13. On the other hand, the drive signal Vg2 becomes the L level, the second switching element 12 is turned off, the current I2 does not flow, and the detection voltage Vc2 also becomes zero. The current I1 increases at a rate determined by the voltage of the battery B1 and the inductance of the inductor 14, and the detection voltage Vc1 also increases in proportion to the current I1.

[0051] At time t1, when the detected voltage Vc1 reaches the threshold voltage Vr1, the output of the comparator 233 inverts to a high level, resetting the SR latch 236 via the OR circuit 235. The reset of the SR latch 236 causes the output Q, i.e., the drive signal Vg1, to fall, and the output NQ, i.e., the drive signal Vg2, to rise. The first switching element 11 turns off, and the voltage across the inductor 14 inverts. The body diode of the second switching element 12 conducts, and after a dead time, the second switching element 12 turns on. Note that the dead time is a very short period and is therefore not shown in the diagram; the conduction of the body diode of the second switching element 12 and the turn-on of the second switching element 12 are shown as occurring simultaneously at time t1. The current in the inductor 14 is maintained, and the current I2 flows through the second loop from the negative terminal of the battery B2 to the positive terminal of the battery B2 via the second switching element 12, the inductor 14, and the current interruption means 13. This is a negative current opposite in direction to the current I2 shown in the diagram. Starting with a current value whose absolute value corresponds to the threshold voltage Vr1, it increases in the positive direction with a slope determined by the voltage of battery B2 and the inductance of inductor 14.

[0052] Eventually, at time t2, the reference clock CK0 starts up, and the operation from time t0 is repeated. In this repetition, a pulsed current flows with a peak value corresponding to the threshold voltage Vr1 as the current I1 in the direction of discharging battery B1, and a pulsed current flows with a peak value corresponding to the threshold voltage Vr1 as the current I2 in the direction of charging battery B2.

[0053] Next, at time t3, when the control signal Vs reaches the L level, switch circuit 237 switches to select and output output NQ of SR latch 236, and switch circuit 238 switches to select and output output Q of SR latch 236. As a result, the rising timing of the drive signals Vg1 and Vg2 are also swapped. Specifically, the drive signal Vg2 reaches the H level when the reference clock CK0 rises, and becomes L level when the detection voltage Vc2 reaches the threshold voltage Vr2 or when the clock CK1 rises. From time t3 onwards, the current I2 continues to flow, and the current I2 increases.

[0054] At time t4, when the ON state of the second switching element 12 reaches its maximum ON period, the clock CK1 rises, the SR latch 236 is reset via the OR circuit 235, the drive signal Vg2 falls, and the second switching element 12 turns off. At this time, assuming that the increasing current I2 has reached the positive direction, the voltage across the inductor 14 reverses. The body diode of the first switching element 11 conducts, and after a dead time, the first switching element 11 turns ON.

[0055] At time t5, the reference clock CK0 rises, the SR latch 236 is set, output Q, i.e., the drive signal Vg2 rises, and output NQ, i.e., the drive signal Vg1 falls. The drive signal Vg2 turns on the second switching element 12 and conducts, and current I2 flows through the second loop from the positive terminal of battery B2 to the negative terminal of battery B2 via the current interruption means 13, inductor 14, and second switching element 12. Meanwhile, the drive signal Vg1 becomes L level, the first switching element 11 turns off, current I1 does not flow, and the detected voltage Vc1 also becomes zero. Current I2 increases with a slope determined by the voltage of battery B2 and the inductance of inductor 14, and the detected voltage Vc2 also increases proportionally to the current I2. From here on, the operation from time t3, when the second switching element 12 switches during its maximum on period, is repeated. With this repetition, the peak value of current I2 increases.

[0056] At time t6, when the detected voltage Vc2 of the current I2 reaches the threshold voltage Vr2, the output of the comparator 234 inverts to a high level, resetting the SR latch 236 via the OR circuit 235. The reset of the SR latch 236 causes the output Q, i.e., the drive signal Vg2, to fall, and the output NQ, i.e., the drive signal Vg1, to rise. The second switching element 12 turns off, and the voltage across the inductor 14 inverts. The body diode of the first switching element 11 conducts, and after a dead time, the first switching element 11 turns on. The current in the inductor 14 is maintained, and the current I1 flows through the first loop from the negative terminal of the battery B1 to the positive terminal of the battery B1 via the current interruption means 13, the inductor 14, and the first switching element 11. This is a negative current opposite in direction to the current I1 shown in the diagram. Starting with a current value whose absolute value corresponds to the threshold voltage Vr2, it increases in the positive direction with a slope determined by the voltage of battery B1 and the inductance of inductor 14.

[0057] Eventually, at time t7, the reference clock CK0 starts up, and the operation from time t5 is repeated. In this repetition, a pulsed current flows with a peak value corresponding to the threshold voltage Vr2 as the current I2 in the direction of discharging battery B2, and a pulsed current flows with a peak value corresponding to the threshold voltage Vr2 as the current I1 in the direction of charging battery B1.

[0058] Next, at time t8, when the control signal Vs reaches the H level, switch circuit 237 switches to select and output output Q of SR latch 236, and switch circuit 238 switches to select and output output NQ of SR latch 236. As a result, the rising timing of drive signals Vg1 and Vg2 is also reversed. Specifically, drive signal Vg1 reaches the H level on the rising edge of the reference clock CK0, and becomes L level when the detection voltage Vc2 reaches the threshold voltage Vr2 or when clock CK1 rises. From time t8 onwards, current I1 continues to flow, and the current I1 increases.

[0059] Subsequently, the switching operation of the first switching element 11 during its maximum on-period causes current I1 to increase and current I2 to decrease. Eventually, the peak value of current I1 becomes a current value corresponding to the threshold voltage Vr1, and the operation from time t0 onward is performed again.

[0060] As described above, in accordance with the control signal Vs, the batteries B1 and B2 are repeatedly charged and discharged with a predetermined peak value pulse current with low loss. The charge / discharge current I1 is converted to a detection voltage Vc1 by the detection resistor 15, and the current I2 is converted to a detection voltage Vc2 by the detection resistor 16, and both are input to the current measurement unit 21. During the measurement of complex impedance, the impedance measuring device 1 regenerates energy drawn from battery B1 to battery B2 during the H-level period of the control signal Vs, and regenerates energy drawn from battery B2 to battery B1 during the L-level period of the control signal Vs. Therefore, if the H-level period and the L-level period of the control signal Vs are equal, and the threshold voltages Vr1 and Vr2 are equal, the charge and discharge charges of batteries B1 and B2 will also be equal, thus suppressing increases and decreases in battery voltage and changes in charge capacity SOC (State of Charge).

[0061] Conversely, energy can be transferred from battery B1 to battery B2, or from battery B2 to battery B1, by making threshold voltages Vr1 and Vr2 different, or by changing the high-low period ratio of the control signal Vs. For example, when transferring energy from battery B1 to battery B2, it is advisable to make threshold voltage Vr1 higher than threshold voltage Vr2, or to make the high-level period of the control signal Vs longer than the low-level period. Although not the essence of this disclosure, since the voltage of each battery is also monitored, this energy transfer can also be applied to maintaining the voltage balance of the batteries.

[0062] As described above, the AC detection unit 22 receives a measurement instruction signal containing information on a predetermined measurement frequency from a higher-level system 200 which has a function to calculate complex impedance. Based on the measurement results of the voltage measurement unit 20 and the current measurement unit 21, it measures the AC voltage and AC current corresponding to the predetermined measurement frequency and outputs them to the higher-level system 200. The drive control unit 23 drives the first switching element 11 and the second switching element 12 to periodically change the state of electrical energy transfer through the inductor 14 according to the predetermined measurement frequency. In other words, the drive control unit 23 applies a first pulse current of a predetermined measurement frequency to battery B1 and applies a second pulse current of the opposite direction to the first pulse current of a predetermined measurement frequency to battery B2. The drive control unit 23 is an example of a current application circuit.

[0063] This allows the transfer of electrical energy between battery B1 and battery B2 to be periodically changed according to a predetermined measurement frequency, thereby enabling the measurement of AC voltage and AC current corresponding to the predetermined measurement frequency, and enabling the measurement of the complex impedance of batteries B1 and B2.

[0064] The voltage measurement unit 20 may also measure the voltage of two or more batteries simultaneously. This allows the voltage of battery B1 and battery B2 to be measured in a short time.

[0065] Furthermore, as shown in Figure 4, the drive control unit 23 may alternately turn on the first switching element 11 and the second switching element 12 at a frequency higher than the predetermined measurement frequency. This shortens the time during which current flows through the inductor 14 at once. In other words, since a large current is less likely to flow through the inductor 14, the inductor 14 can be miniaturized, and consequently, the impedance measuring device 1 can be miniaturized.

[0066] Furthermore, the drive control unit 23 may control the on-time of the first switching element 11 and the on-time of the second switching element 12 so as to repeat, at a period corresponding to a predetermined measurement frequency, a first energy transfer state (from time t0 to time t4 in Figure 4) in which a discharge current is supplied from the battery B1 when the first switching element 11 is turned on and a charging current is supplied to the battery B2 when the second switching element 12 is turned on, and a second energy transfer state (from time t4 to time t8 in Figure 4) in which a discharge current is supplied from the battery B2 when the second switching element 12 is turned on and a charging current is supplied to the battery B1 when the first switching element 11 is turned on.

[0067] As a result, as shown from time t3 to time t4 in Figure 4, by increasing the on time of the second switching element 12, a discharge current can be started to flow from the battery B2, and as a result, it is possible to switch from the first energy transfer state to the second energy transfer state. Also, as shown from time t8 onwards in Figure 4, by increasing the on time of the first switching element 11, a discharge current can be started to flow from the battery B1, and as a result, it is possible to switch from the second energy transfer state to the first energy transfer state.

[0068] Furthermore, the drive control unit 23 may limit the peak value of the discharge current from battery B1 to a predetermined value (a value corresponding to the threshold voltage Vr1) in the first energy transfer state, and limit the peak value of the discharge current from battery B2 to a predetermined value (a value corresponding to the threshold voltage Vr2) in the second energy transfer state. This allows the discharge current from battery B1 and battery B2 to be limited, thereby suppressing switching losses that occur during switching.

[0069] Furthermore, the switching circuit may also have a current interruption means 13 connected in series with the inductor 14, and the drive control unit 23 may interrupt the current flowing to the current interruption means 13 when the detection results of the detection resistors 15 and 16 exceed a predetermined amount. This allows the current to be interrupted when an overcurrent flows.

[0070] Next, the operation of the battery monitoring system 100 when calculating the complex current flowing through load 3 will be explained in detail using Figure 5.

[0071] Figure 5 is a flowchart showing an example of the operation of the battery monitoring system 100 according to Embodiment 1.

[0072] First, the impedance calculation unit 201 measures the complex impedance while the electric vehicle is stationary and no current is flowing through the load 3 (step S101). In other words, the impedance calculation unit 201 measures the complex impedance that is not affected by the load current when the electric vehicle is stationary.

[0073] Next, the process from step S102 is performed after the electric vehicle starts moving.

[0074] The voltage measuring unit 20 and the current measuring unit 21 measure the complex voltage and complex current (step S102). Specifically, the voltage measuring unit 20 measures the first complex voltage of each of the multiple first batteries constituting battery B1, and measures the second complex voltage of each of the multiple second batteries constituting battery B2. The current measuring unit 21 measures the first complex current flowing through battery B1 and measures the second complex current flowing through battery B2.

[0075] Next, the AC detection unit 22 calculates the complex current flowing through the load 3 using the previous measurement results (step S103). Let V1 be the first complex voltage, V2 be the second complex voltage, I1 be the first complex current, and I2 be the second complex current. Let Z1 be the first complex impedance of battery B1 measured in the past, and Z2 be the second complex impedance of battery B2 measured in the past. Let ΔZ1 be the variation of the current first complex impedance from the first complex impedance measured in the past (for example, due to temperature changes), and let ΔZ2 be the variation of the current second complex impedance from the second complex impedance measured in the past. Let Iload be the complex current flowing through the load 3. Note that these values ​​are values ​​at a predetermined measurement frequency of the EIS.

[0076] At this time, the following equations 1 and 2 can be established for the complex current of load 3. Note that all calculations in the following formulas are complex number operations, not scalar value operations.

[0077] Iload+I1=V1 / (Z1+ΔZ1) (Formula 1) Iload+I2=V2 / (Z2+ΔZ2) (Formula 2)

[0078] Here, if Z1 >> ΔZ1 and Z2 >> ΔZ2, the complex current of load 3 is calculated based on equations 1 and 2 above, as shown in equation 3 below.

[0079] Iload=(V1 / Z1+V2 / Z2-I1-I2) / 2 (Formula 3)

[0080] Due to the energy transfer between batteries B1 and B2, which are balanced to have nearly the same voltage, I1 ≈ -I2, and therefore the complex current of load 3 is expressed by the following equation 4.

[0081] Iload=(V1 / Z1+V2 / Z2) / 2 (Formula 4)

[0082] In this way, the AC detection unit 22 calculates the complex current flowing through the load 3 based on the first complex voltage, the second complex voltage, the first complex impedance measured in the past, and the second complex impedance measured in the past. For example, the complex current flowing through the load 3 is calculated based on the sum of the first complex voltages for each of the multiple first batteries constituting battery B1 and the sum of the first complex impedances for each of the multiple first batteries constituting battery B1 measured in the past, as well as the sum of the second complex voltages for each of the multiple second batteries constituting battery B2 and the sum of the second complex impedances for each of the multiple second batteries constituting battery B2 measured in the past. Note that since Z1 >> ΔZ1 and Z2 >> ΔZ2, the complex current of the load 3 calculated by the above equation 4 includes an error corresponding to the impedance fluctuation ratios ΔZ1 / Z1 and ΔZ2 / Z2.

[0083] Next, the impedance calculation unit 201 determines whether the complex current flowing through the load 3 is below a threshold (step S104). For example, if the impedance fluctuation ratio is a maximum of 10%, the error included in the complex current of the load 3 calculated by the above formula 4 will be about 10%. Furthermore, if the complex current flowing through the load 3 is 10% or less of the first complex current and the second complex current, the calculation error of the current first complex impedance and the current second complex impedance will be about 1% or less, and the measurement result can be judged to be acceptable. For this reason, the threshold is set to a value such that the measurement results of the current first complex impedance and the current second complex impedance can be judged to be acceptable.

[0084] If the impedance calculation unit 201 determines that the complex current flowing through the load 3 exceeds a threshold (No in step S104), it does not correct the first complex impedance and the second complex impedance, and the process from step S102 is repeated.

[0085] If the impedance calculation unit 201 determines that the calculated complex current flowing through the load 3 is below a threshold (Yes in step S104), it corrects the first complex impedance and the second complex impedance based on the calculated complex current flowing through the load 3 (step S105). If the current first complex impedance is Z1' and the current second complex impedance is Z2', the impedance calculation unit 201 calculates the current first complex impedance as shown in equation 5 below and the current second complex impedance as shown in equation 6 below.

[0086] Z1'=V1 / (Iload+I1) (Formula 5) Z2'=V2 / (Iload+I2) (Formula 6)

[0087] Specifically, by substituting Equation 4 into Iload in Equations 5 and 6 above, the current first complex impedance and the current second complex impedance are calculated.

[0088] Since Z1' = Z1 + ΔZ1, calculating the current first complex impedance using equation 5 above is equivalent to adding the fluctuation to the first complex impedance, and thus means correcting the first complex impedance. Similarly, since Z2' = Z2 + ΔZ2, calculating the current second complex impedance using equation 6 above is equivalent to adding the fluctuation to the second complex impedance, and thus means correcting the second complex impedance.

[0089] Furthermore, even if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 201 may correct the first complex impedance and the second complex impedance based on the calculated complex current flowing through the load 3. However, if the complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 201 will determine that the corrected first complex impedance and the second complex impedance are abnormal, or will discard the corrected first complex impedance and the second complex impedance.

[0090] In this way, by correcting the complex impedance based on the calculated complex current flowing through load 3, errors in the measurement results of the complex impedance can be suppressed. Furthermore, when the calculated complex current flowing through load 3 is large, the complex impedance is not corrected, or the corrected complex impedance is judged as abnormal, or the corrected complex impedance is discarded, and the complex impedance is measured when the calculated complex current flowing through load 3 is small, thereby suppressing errors in the measurement results of the complex impedance.

[0091] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 201 may change the predetermined measurement frequency to a different frequency and measure the first complex impedance and the second complex impedance. When the calculated complex current flowing through the load 3 is large, the measurement result of the complex impedance measured at the predetermined measurement frequency is affected by the load current. Therefore, by measuring the complex impedance again at a different frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0092] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 201 may measure the first complex impedance and the second complex impedance at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, and interpolate the first complex impedance and the second complex impedance at the predetermined measurement frequency based on the first complex impedance and the second complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency. When the calculated complex current flowing through the load 3 is large, the measurement result of the complex impedance at the predetermined measurement frequency is affected by the load current. Therefore, by interpolating the complex impedance at the predetermined measurement frequency from the complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0093] The battery monitoring system 100 then determines whether the electric vehicle is stationary and no current is flowing to the load 3 (step S106).

[0094] If the electric vehicle is not stationary (No in step S106), the process from step S102 is performed. In this case, in step S103, the complex impedance corrected in step S105 as the previous measurement result is used. In other words, the previously corrected complex impedance is used when calculating the complex current flowing through load 3 this time.

[0095] If the electric vehicle is stationary (Yes in step S106), the process from step S101 is performed again, and the complex impedance is measured again while the electric vehicle is stationary. Then, in step S103, the complex impedance measured in step S101 is used as the previous measurement result. In other words, the complex impedance measured again while the electric vehicle is stationary is used when calculating the complex current flowing through load 3 this time. Since the complex impedance corrected in step S105 may contain errors, if the current complex impedance is repeatedly corrected using the previous complex impedance which may contain errors, the measurement results may drift. Therefore, by measuring the accurate complex impedance when the electric vehicle is stationary and using that measurement result as the previous measurement result, it is possible to suppress the drift of the measurement results. Note that the process in step S106 is not required.

[0096] In step S103, the AC detection unit 22 may calculate the complex current flowing through the load 3 based on the sum of the first complex voltage and the second complex voltage. In this case, the complex current of the load 3 is expressed by the following equation 7.

[0097] Iload=(V1+V2) / (Z1+Z2) (Formula 7)

[0098] Furthermore, in step S103, the AC detection unit 22 may calculate a first estimated complex current based on the first complex voltage and the first complex impedance measured in the past, calculate a second estimated complex current based on the second complex voltage and the second complex impedance measured in the past, and calculate the complex current flowing through the load 3 based on the first estimated complex current and the second estimated complex current. If the first estimated complex current is I1est and the second estimated complex current is I2est, the first estimated complex current is expressed by the following equation 8, the second estimated complex current is expressed by the following equation 9, and the complex current flowing through the load 3 is expressed by the following equation 10.

[0099] I1est=V1 / Z1 (Formula 8) I2est=V2 / Z2 (Formula 9) Iload=(I1est+I2est) / 2 (Formula 10)

[0100] As explained above, when a first pulse current is applied to battery B1 and a second pulse current opposite to the first pulse current is applied to battery B2, the complex current flowing through load 3 can be calculated based on the first complex voltage of battery B1 and the second complex voltage of battery B2. Therefore, by correcting the complex impedance based on the calculated complex current flowing through load 3, errors in the measurement results of the complex impedance can be suppressed. Alternatively, by measuring the complex impedance when the calculated complex current flowing through load 3 is small, errors in the measurement results of the complex impedance can be suppressed.

[0101] Although an example was described in which the sum of the complex impedances of multiple batteries is corrected using the estimated complex current of load 3, the complex impedance of each of the multiple batteries can also be corrected using the estimated complex current of load 3. Furthermore, the calculation of the complex current of load 3 does not necessarily require the sum of the complex voltages and complex impedances of the multiple batteries; the complex voltage and complex impedance of each of the multiple batteries may be used instead. This is also true in subsequent embodiments.

[0102] (Embodiment 2) Next, a battery monitoring system according to Embodiment 2 will be described.

[0103] Figure 6 is a configuration diagram showing an example of a battery monitoring system 100a according to Embodiment 2. In addition to the battery monitoring system 100a, Figure 6 also shows batteries B1 and B2 and a load 3.

[0104] The battery monitoring system 100a differs from the battery monitoring system 100 according to Embodiment 1 in that it includes an impedance measuring device 1a instead of the impedance measuring device 1, and a higher-level system 200a instead of the higher-level system 200. Furthermore, the impedance measuring device 1a differs from the impedance measuring device 1 according to Embodiment 1 in that it includes a drive measuring circuit 2a instead of the drive measuring circuit 2, the drive measuring circuit 2a includes an AC detection unit 22a instead of the AC detection unit 22, and a drive control unit 23a instead of the drive control unit 23. Also, the higher-level system 200a differs from the higher-level system 200 according to Embodiment 1 in that it includes an impedance calculation unit 202 instead of the impedance calculation unit 201. Other points are the same as in Embodiment 1, so their explanation will be omitted, and the following will focus on the differences from Embodiment 1.

[0105] The circuit configuration of the drive control unit 23a is the same as that of the drive control unit 23, but its function is different. Specifically, the drive control unit 23a selectively applies a first pulse current of a predetermined measurement frequency to battery B1 and a second pulse current of a predetermined measurement frequency to battery B2. In other words, when the drive control unit 23a applies the first pulse current to battery B1, it does not apply the second pulse current to battery B2, and when the second pulse current is applied to battery B2, it does not apply the first pulse current to battery B1. The drive control unit 23a is an example of a current application circuit. For example, the drive control unit 23a controls the first switching element 11 and the second switching element 12 to generate heat and dissipate it in the load resistors 17 and 18, and to supply a complex current containing an AC component to batteries B1 and B2.

[0106] The circuit configuration of the AC detection unit 22a is the same as that of the AC detection unit 22, but its function is different. Specifically, when a first pulse current is applied to battery B1 by the drive control unit 23a, the AC detection unit 22a calculates the complex current flowing to load 3 based on the second complex voltage of battery B2, and when a second pulse current is applied to battery B2 by the drive control unit 23a, it calculates the complex current flowing to load 3 based on the first complex voltage of battery B1. In other words, when a pulse current is applied to either battery B1 or B2, the AC detection unit 22a calculates the complex current flowing to load 3 based on the complex voltage of the battery to which no pulse current is applied.

[0107] The impedance calculation unit 202 has essentially the same function as the impedance calculation unit 201. Based on a first complex current and a first complex voltage, it measures the first complex impedance of each of the multiple first batteries, and based on a second complex current and a second complex voltage, it measures the second complex impedance of each of the multiple second batteries. The function for correcting complex impedance differs between the impedance calculation unit 202 and the impedance calculation unit 201.

[0108] Next, the operation of the battery monitoring system 100a when calculating the complex current flowing through load 3 will be explained in detail using Figure 7.

[0109] Figure 7 is a flowchart showing an example of the operation of the battery monitoring system 100a according to Embodiment 2.

[0110] First, the impedance calculation unit 202 measures the first complex impedance of battery B1 (first battery pack) and the second complex impedance of battery B2 (second battery pack) while the electric vehicle is stationary and no current is flowing through the load 3 (step S201). In other words, the impedance calculation unit 202 measures the complex impedance that is not affected by the load current when the electric vehicle is stationary.

[0111] Next, the process from step S202 is performed after the electric vehicle starts moving.

[0112] The drive control unit 23a supplies a measurement current (i.e., a first pulse current) to battery B1, the voltage measurement unit 20 measures the first complex voltage of each of the multiple first batteries constituting battery B1, and measures the second complex voltage of each of the multiple second batteries constituting battery B2, and the current measurement unit 21 measures the first complex current flowing through battery B1 and measures the second complex current flowing through battery B2 (step S202).

[0113] Next, the AC detection unit 22 calculates the complex current flowing through the load 3 from the second complex voltage and second complex current of battery B2 and the previously measured second complex impedance (step S203). Let the first complex voltage be V1, the second complex voltage be V2, the first complex current be I1, and the second complex current be I2. Also, let Z1 be the first complex impedance of battery B1 measured in the past, and Z2 be the second complex impedance of battery B2 measured in the past. Furthermore, let ΔZ1 be the variation of the current first complex impedance from the first complex impedance measured in the past (for example, variation due to temperature changes), and let ΔZ2 be the variation of the current second complex impedance from the second complex impedance measured in the past. Also, let Iload be the complex current flowing through the load 3. Note that these values ​​are values ​​at a predetermined measurement frequency of the EIS.

[0114] At this time, the following equations 11 and 12 can be established for the complex current of load 3.

[0115] Iload+I1=V1 / (Z1+ΔZ1) (Formula 11) Iload=V2 / (Z2+ΔZ2) (Formula 12)

[0116] Here, if Z2 >> ΔZ2, the complex current of load 3 is calculated based on equation 12 above, as shown in equation 13 below.

[0117] Iload=V2 / Z2 (Formula 13)

[0118] Thus, when the AC detection unit 22 applies a first pulse current to the battery B1 by the drive control unit 23a, it calculates the complex current flowing through the load 3 based on the second complex voltage. For example, the complex current flowing through the load 3 is calculated based on the sum of the second complex voltages for each of the multiple second batteries constituting the battery B2 and the sum of the second complex impedances for each of the multiple second batteries constituting the battery B2 that have been measured in the past. Since Z2 >> ΔZ2, the complex current of the load 3 calculated by the above equation 13 includes an error corresponding to the impedance fluctuation ratio ΔZ2 / Z2.

[0119] Next, the impedance calculation unit 202 determines whether the complex current flowing through the load 3 is below a threshold (step S204). For example, if the impedance fluctuation ratio is a maximum of 10%, the error included in the complex current of the load 3 calculated by the above formula 13 will be about 10%. Furthermore, if the complex current flowing through the load 3 is 10% or less of the first complex current, the calculation error of the current first complex impedance and the current second complex impedance will be about 1% or less, and the measurement result can be judged to be acceptable. For this reason, the threshold is set to a value such that the measurement results of the current first complex impedance and the current second complex impedance can be judged to be acceptable.

[0120] If the impedance calculation unit 202 determines that the complex current flowing through the load 3 exceeds a threshold (No in step S204), it does not correct the first complex impedance and repeats the process from step S202.

[0121] If the impedance calculation unit 202 determines that the complex current flowing through the calculated load 3 is below a threshold (Yes in step S204), it corrects the first complex impedance of the battery B1 based on the calculated complex current flowing through the load 3 (step S205). If the current first complex impedance is Z1', the impedance calculation unit 202 calculates the current first complex impedance as shown in the following equation 14.

[0122] Z1'=V1 / (Iload+I1) (Formula 14)

[0123] Specifically, the current first complex impedance is calculated by substituting Equation 13 into Iload in Equation 14 above.

[0124] Since Z1' = Z1 + ΔZ1, calculating the current first complex impedance using equation 14 above is equivalent to adding the fluctuation to the first complex impedance, and thus means correcting the first complex impedance.

[0125] Furthermore, the impedance calculation unit 202 may correct the first complex impedance based on the calculated complex current flowing through the load 3, even if the calculated complex current flowing through the load 3 exceeds a threshold. However, if the complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 will determine the corrected first complex impedance to be abnormal, or discard the corrected first complex impedance.

[0126] In this way, by correcting the first complex impedance based on the calculated complex current flowing through load 3, errors in the measurement results of the first complex impedance can be suppressed. Furthermore, when the calculated complex current flowing through load 3 is large, the first complex impedance is not corrected, or the corrected first complex impedance is judged as abnormal, or the corrected first complex impedance is discarded, and the first complex impedance is measured when the calculated complex current flowing through load 3 is small, thereby suppressing errors in the measurement results of the first complex impedance.

[0127] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 may change the predetermined measurement frequency to a different frequency and measure the first complex impedance. When the calculated complex current flowing through the load 3 is large, the measurement result of the first complex impedance measured at the predetermined measurement frequency is affected by the load current. Therefore, by measuring the first complex impedance again at a different frequency, it is possible to suppress errors in the measurement result of the first complex impedance.

[0128] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 may measure the first complex impedance at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, and interpolate the first complex impedance at a predetermined measurement frequency based on the first complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency. When the calculated complex current flowing through the load 3 is large, the measurement result of the first complex impedance at a predetermined measurement frequency is affected by the load current. Therefore, by interpolating the first complex impedance at a predetermined measurement frequency from the first complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, errors in the measurement result of the first complex impedance can be suppressed.

[0129] Next, the drive control unit 23a supplies a measurement current (i.e., a second pulse current) to the battery B2, the voltage measurement unit 20 measures the first complex voltage of each of the multiple first batteries constituting the battery B1, and measures the second complex voltage of each of the multiple second batteries constituting the battery B2, the current measurement unit 21 measures the first complex current flowing through the battery B1, and measures the second complex current flowing through the battery B2 (step S206).

[0130] Next, the AC detection unit 22 calculates the complex current flowing to the load 3 from the first complex voltage and first complex current of the battery B1 and the first complex impedance from the previous step (step S207).

[0131] At this time, the following equations 15 and 16 can be established for the complex current of load 3.

[0132] Iload=V1 / (Z1+ΔZ1) (Formula 15) Iload+I2=V2 / (Z2+ΔZ2) (Formula 16)

[0133] Here, if Z1 >> ΔZ1, the complex current of load 3 is calculated based on equation 15 above, as shown in equation 17 below.

[0134] Iload=V1 / Z1 (Formula 17)

[0135] Thus, when a second pulse current is applied to the battery B2 by the drive control unit 23a, the AC detection unit 22 calculates the complex current flowing through the load 3 based on the first complex voltage. For example, the complex current flowing through the load 3 is calculated based on the sum of the first complex voltages for each of the multiple first batteries constituting the battery B1 and the sum of the first complex impedances for each of the multiple first batteries constituting the battery B1 that have been measured in the past. Since Z1 >> ΔZ1, the complex current of the load 3 calculated by the above equation 17 includes an error corresponding to the impedance fluctuation ratio ΔZ1 / Z1.

[0136] Next, the impedance calculation unit 202 determines whether the complex current flowing through the load 3 is below a threshold (step S208). For example, if the impedance fluctuation ratio is a maximum of 10%, the error included in the complex current of the load 3 calculated by the above formula 17 will be about 10%. Furthermore, if the complex current flowing through the load 3 is 10% or less of the second complex current, the calculation error of the current first complex impedance and the current second complex impedance will be about 1% or less, and the measurement result can be judged to be acceptable. For this reason, the threshold is set to a value such that the measurement results of the current first complex impedance and the current second complex impedance can be judged to be acceptable.

[0137] If the impedance calculation unit 202 determines that the complex current flowing through the load 3 exceeds a threshold (No in step S208), it does not correct the second complex impedance and the process from step S206 is repeated.

[0138] If the impedance calculation unit 202 determines that the calculated complex current flowing through the load 3 is below a threshold (Yes in step S208), it corrects the second complex impedance of the battery B2 based on the calculated complex current flowing through the load 3 (step S209). If the current second complex impedance is Z2', the impedance calculation unit 202 calculates the current second complex impedance as shown in the following equation 18.

[0139] Z2'=V2 / (Iload+I2) (Formula 18)

[0140] Specifically, the current second complex impedance is calculated by substituting Equation 17 into Iload in Equation 18.

[0141] Since Z2' = Z2 + ΔZ2, calculating the current second complex impedance using equation 18 above is equivalent to adding the fluctuation to the second complex impedance, and thus means correcting the second complex impedance.

[0142] Furthermore, the impedance calculation unit 202 may correct the second complex impedance based on the calculated complex current flowing through the load 3, even if the calculated complex current flowing through the load 3 exceeds a threshold. However, if the complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 will determine the corrected second complex impedance to be abnormal, or discard the corrected second complex impedance.

[0143] In this way, by correcting the second complex impedance based on the calculated complex current flowing through load 3, errors in the measurement results of the second complex impedance can be suppressed. Furthermore, when the calculated complex current flowing through load 3 is large, the second complex impedance is not corrected, or the corrected second complex impedance is judged as abnormal, or the corrected second complex impedance is discarded, and the second complex impedance is measured when the calculated complex current flowing through load 3 is small, thereby suppressing errors in the measurement results of the second complex impedance.

[0144] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 may change the predetermined measurement frequency to a different frequency and measure the second complex impedance. When the calculated complex current flowing through the load 3 is large, the measurement result of the second complex impedance measured at the predetermined measurement frequency is affected by the load current. Therefore, by measuring the second complex impedance again at a different frequency, it is possible to suppress errors in the measurement result of the second complex impedance.

[0145] Furthermore, if the calculated complex current flowing through the load 3 exceeds a threshold, the impedance calculation unit 202 may measure the second complex impedance at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, and interpolate the second complex impedance at the predetermined measurement frequency based on the second complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency. When the calculated complex current flowing through the load 3 is large, the measurement result of the second complex impedance at the predetermined measurement frequency is affected by the load current. Therefore, by interpolating the second complex impedance at the predetermined measurement frequency from the second complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, it is possible to suppress errors in the measurement result of the second complex impedance.

[0146] The battery monitoring system 100 then determines whether the electric vehicle is stationary and no current is flowing to the load 3 (step S210).

[0147] If the electric vehicle is not stationary (No in step S210), the process from step S202 is performed. In this case, in step S203, the second complex impedance corrected in step S209 is used as the previous second complex impedance. In other words, the previously corrected second complex impedance is used in step S203 when calculating the complex current flowing through load 3. Also, in step S207, the first complex impedance corrected in step S205 is used as the previous first complex impedance. In other words, the previously corrected first complex impedance is used in step S207 when calculating the complex current flowing through load 3.

[0148] If the electric vehicle is stationary (Yes in step S210), the process from step S201 is performed, and the complex impedance is measured again while the electric vehicle is stationary. Then, in step S203, the second complex impedance measured in step S201 is used as the previous second complex impedance, and in step S207, the first complex impedance measured in step S201 is used as the previous first complex impedance. In other words, the complex impedance measured again while the electric vehicle is stationary is used when calculating the complex current flowing through load 3 this time. Since the complex impedance corrected in steps S205 and S209 may contain errors, repeatedly correcting the complex impedance using the previous complex impedance which may contain errors may cause the measurement results to drift. Therefore, by measuring the accurate complex impedance when the electric vehicle is stationary and using that measurement result as the previous measurement result, it is possible to suppress the drift of the measurement results. Note that the process in step S210 is not required.

[0149] Furthermore, steps S202 to S205 may be performed after steps S206 to S209 have been completed.

[0150] As explained above, the complex current flowing through load 3 can be calculated based on the second complex voltage of battery B2 when the first pulse current is applied to battery B1, and the complex current flowing through load 3 can be calculated based on the first complex voltage of battery B1 when the second pulse current is applied to battery B2. Therefore, by correcting the complex impedance based on the calculated complex current flowing through load 3, errors in the measurement results of the complex impedance can be suppressed. Alternatively, by measuring the complex impedance when the calculated complex current flowing through load 3 is small, errors in the measurement results of the complex impedance can be suppressed.

[0151] (Other Embodiments) Embodiments have been described above as examples of the technology relating to this disclosure. However, the technology relating to this disclosure is not limited thereto and can be applied to embodiments that are modified, replaced, added to, or omitted as appropriate. For example, the following modified examples are also included in one embodiment of this disclosure.

[0152] For example, in step S103 of the above embodiment 1, the AC detection unit 22 may calculate the error of the first complex voltage caused by the complex current flowing through the load 3 based on the second complex voltage, and calculate the error of the second complex voltage caused by the complex current flowing through the load 3 based on the first complex voltage. In this case, the AC detection unit 22 is an example of an error detection unit.

[0153] Let V1err be the error of the first complex voltage, and V2err be the error of the second complex voltage. For the complex current of load 3, the equations 1 and 2 above can be established, and if Z1 >> ΔZ1 and Z2 >> ΔZ2, then the error of the first complex voltage is calculated as shown in equation 19 below based on equation 2 above, and the error of the second complex voltage is calculated as shown in equation 20 below based on equation 1 above.

[0154] V1err = Z1・Iload = Z1 / (V2 / Z2 - I2) (Equation 19) V2err = Z2・Iload = Z2 / (V1 / Z1 - I1) (Equation 20)

[0155] For example, the error in the first complex voltage is calculated based on the sum of the second complex voltages for each of the multiple second batteries constituting battery B2 and the sum of the second complex impedances for each of the multiple second batteries constituting battery B2 that have been measured in the past. Similarly, the error in the second complex voltage is calculated based on the sum of the first complex voltages for each of the multiple first batteries constituting battery B1 and the sum of the first complex impedances for each of the multiple first batteries constituting battery B1 that have been measured in the past. Since Z2 >> ΔZ2, the error in the first complex voltage calculated in equation 19 above includes an error corresponding to the impedance fluctuation ratio ΔZ2 / Z2. Also, since Z1 >> ΔZ1, the error in the second complex voltage calculated in equation 20 above includes an error corresponding to the impedance fluctuation ratio ΔZ1 / Z1.

[0156] The impedance calculation unit 201 then corrects the first complex impedance based on the error in the calculated first complex voltage, and corrects the second complex impedance based on the error in the calculated second complex voltage. The impedance calculation unit 201 calculates the current first complex impedance as shown in equation 21 below, and calculates the current second complex impedance as shown in equation 22 below.

[0157] Z1'=(V1-V1err) / I1 (Formula 21) Z2'=(V2-V2err) / I2 (Formula 22)

[0158] Specifically, by substituting equation 19 into V1err in equation 21, the current first complex impedance is calculated, and by substituting equation 20 into V2err in equation 22, the current second complex impedance is calculated.

[0159] Since Z1' = Z1 + ΔZ1, calculating the current first complex impedance using equation 21 above is equivalent to adding the fluctuation to the first complex impedance, and thus means correcting the first complex impedance. Similarly, since Z2' = Z2 + ΔZ2, calculating the current second complex impedance using equation 22 above is equivalent to adding the fluctuation to the second complex impedance, and thus means correcting the second complex impedance.

[0160] The impedance calculation unit 201 may also determine whether the error of the first complex voltage and the error of the second complex voltage are below a threshold. For example, if the error of the first complex voltage and the error of the second complex voltage are within 10% of the first complex voltage and the error of the second complex voltage, respectively, it can be determined that the measurement results of the current first complex impedance and the current second complex impedance are acceptable. For this reason, the threshold is set to a value that allows the measurement results of the current first complex impedance and the current second complex impedance to be deemed acceptable.

[0161] If the impedance calculation unit 201 determines that the error in the first complex voltage or the error in the second complex voltage exceeds a threshold, it will either not correct the first complex impedance and the second complex impedance, determine that the corrected first complex impedance and the second complex impedance are abnormal, or discard the corrected first complex impedance and the second complex impedance.

[0162] In this way, by correcting the complex impedance based on the error in the calculated complex voltage, errors in the measurement results of the complex impedance can be suppressed. Furthermore, when the error in the calculated complex voltage is large, the complex impedance can be not corrected, or the corrected complex impedance can be judged as abnormal, or the corrected complex impedance can be discarded, and the complex impedance can be measured when the error in the calculated complex voltage is small, thereby suppressing errors in the measurement results of the complex impedance.

[0163] Furthermore, if the error in the calculated complex voltage exceeds a threshold, the impedance calculation unit 201 may change the predetermined measurement frequency to a different frequency and measure the first complex impedance and the second complex impedance. When the error in the calculated complex voltage is large, the measurement result of the complex impedance measured at the predetermined measurement frequency is affected by the load current. Therefore, by measuring the complex impedance again at another frequency, it is possible to suppress the occurrence of errors in the measurement result of the complex impedance.

[0164] Furthermore, if the error in the calculated complex voltage exceeds a threshold, the impedance calculation unit 201 may measure the first complex impedance and the second complex impedance at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, and interpolate the first complex impedance and the second complex impedance at the predetermined measurement frequency based on the first complex impedance and the second complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency. When the error in the calculated complex voltage is large, the measurement result of the complex impedance at the predetermined measurement frequency is affected by the load current. Therefore, by interpolating the complex impedance at the predetermined measurement frequency from the complex impedance measured at frequencies higher than a predetermined measurement frequency and frequencies lower than a predetermined measurement frequency, it is possible to suppress the occurrence of errors in the measurement result of the complex impedance.

[0165] As explained above, when a first pulse current is applied to battery B1 and a second pulse current opposite to the first pulse current is applied to battery B2, the error in the first complex voltage of battery B1 caused by the complex current flowing through load 3 can be calculated based on the second complex voltage of battery B2, and the error in the second complex voltage of battery B2 caused by the complex current flowing through load 3 can be calculated based on the first complex voltage of battery B1. Therefore, by correcting the complex impedance based on each calculated error, it is possible to suppress errors in the measurement results of the complex impedance. Alternatively, by measuring the complex impedance when each calculated error is small, it is possible to suppress errors in the measurement results of the complex impedance.

[0166] For example, this disclosure can be implemented not only as a battery monitoring system, but also as a battery monitoring method that includes steps (processes) performed by the components constituting the battery monitoring system.

[0167] Figures 8 to 10 are flowcharts showing an example of a battery monitoring method according to another embodiment.

[0168] The battery monitoring method is performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, and as shown in Figure 8, the method includes: a current application step (step S11) in which a first pulse current of a predetermined measurement frequency is applied to the first battery pack and a second pulse current of a predetermined measurement frequency and in the opposite direction to the first pulse current is applied to the second battery pack; a first current detection step for detecting the current flowing through the first battery pack; a second current detection step for detecting the current flowing through the second battery pack; a first voltage measurement step for measuring the first complex voltage of each of the multiple first batteries constituting the first battery pack; and a second voltage measurement step for measuring the second complex voltage of each of the multiple second batteries constituting the second battery pack. The method includes: a first current measurement step (step S12) for measuring a first complex current based on the detection result in the first current detection step; a second current measurement step (step S12) for measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step (step S13) for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and for measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step (step S14) for calculating the complex current flowing through a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

[0169] Furthermore, the battery monitoring method is a battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, and as shown in Figure 9, the method includes: a current application step (step S21) which selectively applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of a predetermined measurement frequency to the second battery pack; a first current detection step which detects the current flowing through the first battery pack; a second current detection step which detects the current flowing through the second battery pack; a first voltage measurement step which measures the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step which measures the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measurement step which measures the first complex current based on the detection result in the first current detection step; and the second current detection step The method includes: a second current measurement step (step S22) for measuring a second complex current based on the detection result; an impedance calculation step (step S23) for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and for measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step (steps S25 and S26) for calculating the complex current flowing through a load supplied with power from the first and second battery packs based on the second complex voltage when a first pulse current is applied to the first battery pack in the current application step (first pulse current application in step S24), and for calculating the complex current flowing through the load based on the first complex voltage when a second pulse current is applied to the second battery pack in the current application step (second pulse current application in step S24).

[0170] Furthermore, the battery monitoring method is a battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, and as shown in Figure 10, the method includes: a current application step (step S31) in which a first pulse current of a predetermined measurement frequency is applied to the first battery pack and a second pulse current of the opposite direction to the first pulse current of a predetermined measurement frequency is applied to the second battery pack; a first current detection step for detecting the current flowing through the first battery pack; a second current detection step for detecting the current flowing through the second battery pack; a first voltage measurement step for measuring the first complex voltage of each of the multiple first batteries constituting the first battery pack; a second voltage measurement step for measuring the second complex voltage of each of the multiple second batteries constituting the second battery pack; and the detection result in the first current detection step. Based on this, the method includes: a first current measurement step for measuring a first complex current; a second current measurement step (step S32) for measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step (step S33) for measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and for measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection step (step S34) for calculating the error in the first complex voltage caused by the complex current flowing to a load supplied with power from the first and second battery packs based on the second complex voltage, and for calculating the error in the second complex voltage caused by the complex current flowing to the load based on the first complex voltage.

[0171] For example, this disclosure can be implemented as a program that causes a computer (processor) to execute the steps included in the battery monitoring method. Furthermore, this disclosure can be implemented as a non-temporary computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0172] For example, if this disclosure is implemented in a program (software), each step is executed by the program using hardware resources such as the computer's CPU, memory, and input / output circuits. In other words, each step is executed by the CPU obtaining data from memory or input / output circuits, performing calculations, and outputting the calculation results to memory or input / output circuits.

[0173] In the above embodiment, each component included in the battery monitoring system may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may also be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0174] Some or all of the functions of the battery monitoring system according to the above embodiment are typically implemented as an LSI, which is an integrated circuit. These may be individually integrated onto a single chip, or some or all of them may be integrated onto a single chip. Furthermore, the implementation is not limited to an LSI, but may also be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connections and settings of the circuit cells inside the LSI may also be used.

[0175] Furthermore, if advances in semiconductor technology or other derived technologies lead to the emergence of integrated circuit technologies that can replace LSIs, then naturally, those technologies may be used to integrate each component included in the battery monitoring system.

[0176] Furthermore, this disclosure also includes forms obtained by applying various modifications to the embodiments that a person skilled in the art could conceive, and forms realized by arbitrarily combining the components and functions of each embodiment without departing from the spirit of this disclosure.

[0177] (Note) The above description of embodiments discloses the following technology.

[0178] (Technology 1) A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and the first current A battery monitoring system comprising: a first current measuring unit that measures a first complex current based on the detection result of a current detector; a second current measuring unit that measures a second complex current based on the detection result of a second current detector; an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection unit that calculates the complex current flowing to a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

[0179] According to this method, when a first pulsed current is applied to the first battery pack and a second pulsed current (opposite to the first pulsed current) is applied to the second battery pack, the complex current flowing through the load can be calculated based on the first complex voltage of the first battery pack and the second complex voltage of the second battery pack. Therefore, by correcting the complex impedance based on the calculated complex current flowing through the load, errors in the measurement results of the complex impedance can be suppressed. Alternatively, by measuring the complex impedance when the calculated complex current flowing through the load is small, errors in the measurement results of the complex impedance can be suppressed.

[0180] (Technology 2) The battery monitoring system according to Technology 1, wherein the load current detection unit calculates the complex current flowing through the load based on the sum of the first complex voltage and the second complex voltage.

[0181] According to this, as shown in equation 7 above, the complex current flowing through the load can be calculated based on the sum of the first complex voltage and the second complex voltage.

[0182] (Technology 3) The battery monitoring system according to Technology 1, wherein the load current detection unit calculates the complex current flowing through the load based on the first complex voltage, the second complex voltage, the first complex impedance measured in the past, and the second complex impedance measured in the past.

[0183] According to this, as shown in Equation 4 above, the complex current flowing through the load can be calculated based on the first complex voltage, the second complex voltage, the first complex impedance measured in the past, and the second complex impedance measured in the past.

[0184] (Technical 4) The battery monitoring system according to Technical 1, wherein the load current detection unit calculates a first estimated complex current based on the first complex voltage and the first complex impedance measured in the past, calculates a second estimated complex current based on the second complex voltage and the second complex impedance measured in the past, and calculates the complex current flowing through the load based on the first estimated complex current and the second estimated complex current.

[0185] According to this, as shown in equation 10 above, the complex current flowing through the load can be calculated based on the first estimated complex current and the second estimated complex current.

[0186] (Technical 5) The battery monitoring system according to any one of Technical 1 to 4, wherein the impedance calculation unit corrects the first complex impedance and the second complex impedance based on the complex current flowing through the load.

[0187] According to this method, by correcting the complex impedance based on the calculated complex current flowing through the load, it is possible to suppress errors in the measurement results of the complex impedance.

[0188] (Technical 6) The battery monitoring system according to any one of Technical 1 to 5, wherein the impedance calculation unit does not correct the first complex impedance and the second complex impedance when the complex current flowing through the load exceeds a threshold, or determines that the corrected first complex impedance and the second complex impedance are abnormal, or discards the corrected first complex impedance and the second complex impedance.

[0189] According to this method, when the complex current flowing through the calculated load is large, the complex impedance is not corrected, or the corrected complex impedance is judged as abnormal, or the corrected complex impedance is discarded. By measuring the complex impedance when the complex current flowing through the calculated load is small, it is possible to suppress errors in the measurement results of the complex impedance.

[0190] (Technical 7) The battery monitoring system according to any one of Technical 1 to 6, wherein the impedance calculation unit changes the predetermined measurement frequency to a different frequency when the complex current flowing through the load exceeds a threshold, and measures the first complex impedance and the second complex impedance.

[0191] According to this, when the complex current flowing through the calculated load is large, the measurement result of the complex impedance measured at a predetermined measurement frequency is affected by the load current. Therefore, by measuring the complex impedance again at a different frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0192] (Technical 8) The battery monitoring system according to any one of Technical 1 to 7, wherein the impedance calculation unit measures the first complex impedance and the second complex impedance at a frequency higher than the predetermined measurement frequency and at a frequency lower than the predetermined measurement frequency when the complex current flowing through the load exceeds a threshold, and interpolates the first complex impedance and the second complex impedance at the predetermined measurement frequency based on the first complex impedance and the second complex impedance measured at a frequency higher than the predetermined measurement frequency and at a frequency lower than the predetermined measurement frequency.

[0193] According to this method, when the complex current flowing through the calculated load is large, the measurement result of the complex impedance at a predetermined measurement frequency is affected by the load current. Therefore, by interpolating the complex impedance at the predetermined measurement frequency from the complex impedance measured at frequencies higher and lower than the predetermined measurement frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0194] (Technical 9) A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that selectively applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measuring unit for measuring a first complex current based on the output of the first current detector; and the output of the second current detector A battery monitoring system comprising: a second current measuring unit that measures a second complex current based on the above; an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection unit that, when the first pulse current is applied to the first battery pack by the current application circuit, calculates the complex current flowing to the load supplied with power from the first battery pack and the second battery pack based on the second complex voltage, and when the second pulse current is applied to the second battery pack by the current application circuit, calculates the complex current flowing to the load based on the first complex voltage.

[0195] According to this, the complex current flowing through the load can be calculated based on the second complex voltage of the second battery pack when the first pulse current is applied to the first battery pack, and the complex current flowing through the load can be calculated based on the first complex voltage of the first battery pack when the second pulse current is applied to the second battery pack. Therefore, by correcting the complex impedance based on the calculated complex current flowing through the load, errors in the measurement results of the complex impedance can be suppressed. Alternatively, by measuring the complex impedance when the calculated complex current flowing through the load is small, errors in the measurement results of the complex impedance can be suppressed.

[0196] (Technical 10) The battery monitoring system according to Technical 9, wherein the impedance calculation unit corrects the first complex impedance based on the complex current flowing through the load calculated based on the second complex voltage, and corrects the second complex impedance based on the complex current flowing through the load calculated based on the first complex voltage.

[0197] According to this method, by correcting the complex impedance based on the calculated complex current flowing through the load, it is possible to suppress errors in the measurement results of the complex impedance.

[0198] (Technical 11) The battery monitoring system according to Technical 9 or 10, wherein the impedance calculation unit, when the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, does not correct the first complex impedance, or determines the corrected first complex impedance to be abnormal, or discards the corrected first complex impedance, and when the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold, does not correct the second complex impedance, or determines the corrected second complex impedance to be abnormal, or discards the corrected second complex impedance.

[0199] According to this method, when the complex current flowing through the calculated load is large, the complex impedance is not corrected, or the corrected complex impedance is judged as abnormal, or the corrected complex impedance is discarded. By measuring the complex impedance when the complex current flowing through the calculated load is small, it is possible to suppress errors in the measurement results of the complex impedance.

[0200] (Technical 12) A battery monitoring system according to any one of Technical 9 to 11, wherein the impedance calculation unit measures the first complex impedance by changing the predetermined measurement frequency to a different frequency if the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, and measures the second complex impedance by changing the predetermined measurement frequency to a different frequency if the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold.

[0201] According to this, when the complex current flowing through the calculated load is large, the measurement result of the complex impedance measured at a predetermined measurement frequency is affected by the load current. Therefore, by measuring the complex impedance again at a different frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0202] (Technical 13) A battery monitoring system according to any one of Technical 9 to 12, wherein the impedance calculation unit measures the first complex impedance at a frequency higher than the predetermined measurement frequency and a frequency lower than the predetermined measurement frequency when the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, interpolates the first complex impedance at the predetermined measurement frequency based on the first complex impedance measured at the frequency higher than the predetermined measurement frequency and the frequency lower than the predetermined measurement frequency, and measures the second complex impedance at the predetermined measurement frequency at a frequency higher than the predetermined measurement frequency and a frequency lower than the predetermined measurement frequency when the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold, and interpolates the second complex impedance at the predetermined measurement frequency based on the second complex impedance measured at the frequency higher than the predetermined measurement frequency and the frequency lower than the predetermined measurement frequency.

[0203] According to this method, when the complex current flowing through the calculated load is large, the measurement result of the complex impedance at a predetermined measurement frequency is affected by the load current. Therefore, by interpolating the complex impedance at the predetermined measurement frequency from the complex impedance measured at frequencies higher and lower than the predetermined measurement frequency, it is possible to suppress errors in the measurement result of the complex impedance.

[0204] (Technical 14) A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite direction to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and a first complex current measuring unit based on the detection result of the first current detector. A battery monitoring system comprising: a current measuring unit; a second current measuring unit that measures a second complex current based on the detection result of the second current detector; an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; an error detection unit that calculates the error in the first complex voltage caused by the complex current flowing to a load supplied with power from the first battery pack and the second battery pack, and calculates the error in the second complex voltage caused by the complex current flowing to the load, based on the first complex voltage.

[0205] According to this, when a first pulse current is applied to the first battery pack and a second pulse current opposite to the first pulse current is applied to the second battery pack, the error in the first complex voltage of the first battery pack caused by the complex current flowing through the load can be calculated based on the second complex voltage of the second battery pack, and the error in the second complex voltage of the second battery pack caused by the complex current flowing through the load can be calculated based on the first complex voltage of the first battery pack. Therefore, by correcting the complex impedance based on each calculated error, it is possible to suppress errors in the measurement results of the complex impedance. Alternatively, by measuring the complex impedance when each calculated error is small, it is possible to suppress errors in the measurement results of the complex impedance.

[0206] (Technical 15) A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency to the second battery pack in the opposite direction to the first pulse current; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; and a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack. A battery monitoring method comprising: a first current measurement step of measuring a first complex current based on the detection result in the first current detection step; a second current measurement step of measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step of calculating the complex current flowing to a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

[0207] This provides a battery monitoring method that can suppress errors in the measurement results of complex impedance.

[0208] (Technical 16) A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of selectively applying a first pulse current of a predetermined measurement frequency to the first battery pack and applying a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and a first current measurement step of measuring a first complex current based on the detection result in the first current detection step. A battery monitoring method comprising: a second current measurement step of measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step of calculating the complex current flowing through a load to which power is supplied from the first and second battery packs based on the second complex voltage when the first pulse current is applied to the first battery pack in the current application step, and calculating the complex current flowing through the load based on the first complex voltage when the second pulse current is applied to the second battery pack in the current application step.

[0209] This provides a battery monitoring method that can suppress errors in the measurement results of complex impedance.

[0210] (Technical 17) A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite to the first pulse current to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; and, based on the detection result in the first current detection step, A battery monitoring method comprising: a first current measurement step of measuring a complex current; a second current measurement step of measuring a second complex current based on the detection result in the second current detection step; an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection step of calculating the error in the first complex voltage caused by the complex current flowing to a load supplied with power from the first battery pack and the second battery pack, based on the second complex voltage, and calculating the error in the second complex voltage caused by the complex current flowing to the load, based on the first complex voltage.

[0211] This provides a battery monitoring method that can suppress errors in the measurement results of complex impedance.

[0212] This disclosure is useful as a system for diagnosing battery degradation.

[0213] 1, 1a Impedance measuring device 2, 2a Drive measuring circuit 3 Load 11 First switching element 12 Second switching element 13 Current interruption means 14 Inductor 15, 16 Detection resistor 17, 18 Load resistor 20 Voltage measuring unit 21 Current measuring unit 22, 22a AC detection unit 23, 23a Drive control unit 100, 100a Battery monitoring system 200, 200a Higher-level system 201, 202 Impedance calculation unit 220 Signal generation unit 221 Conversion unit 222 Integration unit 223 Holding unit 224 Communication unit 230 Oscillator 231, 232 Reference voltage source 233, 234 Comparator 235 OR circuit 236 SR latch 237, 238 Switch circuit 239 Anomaly detection circuit 240 Inverter 241, 242, 243 AND circuit B1, B2 Battery

Claims

1. A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite direction to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measuring unit for measuring a first complex current based on the detection result of the first current detector; and a second current measuring unit for measuring a second complex current based on the detection result of the second current detector. A battery monitoring system comprising: an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection unit that calculates the complex current flowing to a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

2. The battery monitoring system according to claim 1, wherein the load current detection unit calculates the complex current flowing through the load based on the sum of the first complex voltage and the second complex voltage.

3. The battery monitoring system according to claim 1, wherein the load current detection unit calculates the complex current flowing through the load based on the first complex voltage, the second complex voltage, the first complex impedance measured in the past, and the second complex impedance measured in the past.

4. The battery monitoring system according to claim 1, wherein the load current detection unit calculates a first estimated complex current based on the first complex voltage and the first complex impedance measured in the past, calculates a second estimated complex current based on the second complex voltage and the second complex impedance measured in the past, and calculates the complex current flowing to the load based on the first estimated complex current and the second estimated complex current.

5. The battery monitoring system according to any one of claims 1 to 4, wherein the impedance calculation unit corrects the first complex impedance and the second complex impedance based on the complex current flowing through the load.

6. The battery monitoring system according to any one of claims 1 to 5, wherein the impedance calculation unit, when the complex current flowing through the load exceeds a threshold, does not correct the first complex impedance and the second complex impedance, or determines that the corrected first complex impedance and the second complex impedance are abnormal, or discards the corrected first complex impedance and the second complex impedance.

7. The battery monitoring system according to any one of claims 1 to 6, wherein the impedance calculation unit, when the complex current flowing through the load exceeds a threshold, changes the predetermined measurement frequency to a different frequency and measures the first complex impedance and the second complex impedance.

8. The battery monitoring system according to any one of claims 1 to 7, wherein the impedance calculation unit measures the first complex impedance and the second complex impedance at a frequency higher than the predetermined measurement frequency and at a frequency lower than the predetermined measurement frequency when the complex current flowing through the load exceeds a threshold, and interpolates the first complex impedance and the second complex impedance at the predetermined measurement frequency based on the first complex impedance and the second complex impedance measured at the frequency higher than the predetermined measurement frequency and at a frequency lower than the predetermined measurement frequency.

9. A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that selectively applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measuring unit for measuring a first complex current based on the output of the first current detector; and a second current measuring unit for measuring a second complex current based on the output of the second current detector. A battery monitoring system comprising: an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection unit that, when the first pulse current is applied to the first battery pack by the current application circuit, calculates the complex current flowing to a load supplied with power from the first battery pack and the second battery pack based on the second complex voltage, and when the second pulse current is applied to the second battery pack by the current application circuit, calculates the complex current flowing to the load based on the first complex voltage.

10. The battery monitoring system according to claim 9, wherein the impedance calculation unit corrects the first complex impedance based on the complex current flowing through the load calculated based on the second complex voltage, and corrects the second complex impedance based on the complex current flowing through the load calculated based on the first complex voltage.

11. The battery monitoring system according to claim 9 or 10, wherein the impedance calculation unit, if the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, does not correct the first complex impedance, or determines the corrected first complex impedance to be abnormal, or discards the corrected first complex impedance; and if the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold, does not correct the second complex impedance, or determines the corrected second complex impedance to be abnormal, or discards the corrected second complex impedance.

12. The battery monitoring system according to any one of claims 9 to 11, wherein the impedance calculation unit measures the first complex impedance by changing the predetermined measurement frequency to a different frequency if the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, and measures the second complex impedance by changing the predetermined measurement frequency to a different frequency if the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold.

13. The battery monitoring system according to any one of claims 9 to 12, wherein the impedance calculation unit measures the first complex impedance at a frequency higher than the predetermined measurement frequency and a frequency lower than the predetermined measurement frequency if the complex current flowing through the load calculated based on the second complex voltage exceeds a threshold, and interpolates the first complex impedance at the predetermined measurement frequency based on the first complex impedance measured at the frequency higher than the predetermined measurement frequency and the frequency lower than the predetermined measurement frequency; and measures the second complex impedance at the predetermined measurement frequency at a frequency higher than the predetermined measurement frequency and a frequency lower than the predetermined measurement frequency if the complex current flowing through the load calculated based on the first complex voltage exceeds a threshold, and interpolates the second complex impedance at the predetermined measurement frequency based on the second complex impedance measured at the frequency higher than the predetermined measurement frequency and the frequency lower than the predetermined measurement frequency.

14. A battery monitoring system for measuring the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application circuit that applies a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite direction to the first pulse current to the second battery pack; a first current detector for detecting the current flowing through the first battery pack; a second current detector for detecting the current flowing through the second battery pack; a first voltage measuring unit for measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measuring unit for measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measuring unit for measuring a first complex current based on the detection result of the first current detector; and a second current measuring unit for measuring a second complex current based on the detection result of the second current detector. A battery monitoring system comprising: an impedance calculation unit that measures the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measures the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection unit that calculates the error in the first complex voltage caused by the complex current flowing to a load supplied with power from the first and second battery packs based on the second complex voltage, and calculates the error in the second complex voltage caused by the complex current flowing to the load based on the first complex voltage.

15. A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the opposite direction to the first pulse current of the predetermined measurement frequency to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measurement step of measuring a first complex current based on the detection result in the first current detection step; and a second current measurement step of measuring a second complex current based on the detection result in the second current detection step. A battery monitoring method comprising: an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step of calculating the complex current flowing through a load to which power is supplied from the first battery pack and the second battery pack, based on the first complex voltage and the second complex voltage.

16. A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of selectively applying a first pulse current of a predetermined measurement frequency to the first battery pack and applying a second pulse current of the predetermined measurement frequency to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measurement step of measuring a first complex current based on the detection result in the first current detection step; and a second current measurement step of measuring a second complex current based on the detection result in the second current detection step. A battery monitoring method comprising: an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and a load current detection step of calculating the complex current flowing through a load to which power is supplied from the first and second battery packs based on the second complex voltage when the first pulse current is applied to the first battery pack in the current application step, and calculating the complex current flowing through the load based on the first complex voltage when the second pulse current is applied to the second battery pack in the current application step.

17. A battery monitoring method performed by a battery monitoring system that measures the complex impedance of a first battery pack and a second battery pack connected in series, comprising: a current application step of applying a first pulse current of a predetermined measurement frequency to the first battery pack and a second pulse current of the same predetermined measurement frequency and opposite to the first pulse current to the second battery pack; a first current detection step of detecting the current flowing through the first battery pack; a second current detection step of detecting the current flowing through the second battery pack; a first voltage measurement step of measuring the first complex voltage of each of the plurality of first batteries constituting the first battery pack; a second voltage measurement step of measuring the second complex voltage of each of the plurality of second batteries constituting the second battery pack; a first current measurement step of measuring a first complex current based on the detection result in the first current detection step; and a second current measurement step of measuring a second complex current based on the detection result in the second current detection step. A battery monitoring method comprising: an impedance calculation step of measuring the first complex impedance of each of the plurality of first batteries based on the first complex current and the first complex voltage, and measuring the second complex impedance of each of the plurality of second batteries based on the second complex current and the second complex voltage; and an error detection step of calculating the error in the first complex voltage caused by the complex current flowing through a load supplied with power from the first and second battery packs based on the second complex voltage, and calculating the error in the second complex voltage caused by the complex current flowing through the load based on the first complex voltage.

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