Impedance measurement system

Abstract

We provide a small, lightweight, and low-loss impedance measurement system. [Solution] An impedance measurement system 100 for measuring the internal impedance 1102 of a battery 11 comprises a power supply microcontroller 141, a drive transistor 144, a measuring device 2, and a discharge load. The power supply microcontroller 141 generates a current waveform based on frequency and current information for generating an AC current for measurement. The drive transistor 144 is driven by the current waveform generated by the power supply microcontroller 141 and outputs an AC current for measurement. The measuring device 2 determines the internal impedance 1102 of the battery 11 based on the AC current for measurement and the voltage drop caused by flowing the AC current for measurement through the battery 11. The discharge load consumes current from the battery 11 when the measuring device 2 determines the internal impedance 1102 of the battery 11.

Description

[Technical Field]

[0001] This invention relates to an impedance measurement system. [Background technology]

[0002] In automobiles that use secondary batteries as a power source, there is a known technique for managing the battery's condition, such as remaining charge, degradation rate, and presence of abnormalities, using the measured impedance value of the secondary battery. For example, Patent Document 1 discloses a technique for accurately measuring the complex impedance of a secondary battery using EIS (Electrochemical Impedance Spectroscopy). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020-261799 [Overview of the project] [Problems that the invention aims to solve]

[0004] EIS measurement is a measurement method that involves passing a measurement-grade alternating current through a secondary battery under measurement and simultaneously measuring the alternating voltage between the electrodes of the secondary battery, as well as determining the impedance of the secondary battery based on the applied alternating current. The technology disclosed in Patent Document 1 uses a transformer method in which the measurement-grade alternating current applied to the secondary battery is generated using a transformer.

[0005] Since EIS measurement is an established method, it would be beneficial to mount an EIS measurement device in a vehicle to continuously monitor the status of the drive battery. However, when mounting a measurement device in a vehicle, it is necessary to ensure that the measurement device conforms to EMC (Electromagnetic Compatibility) standards for electromagnetic environment and performance requirements to prevent adverse effects such as noise or signal phase shifts from equipment placed around the device. However, making a transformer EMC compliant requires additional work and parts, posing a significant cost challenge. Furthermore, depending on the frequency band of the AC current used for measurement, the transformer may become larger, potentially leading to a larger measurement device that takes up valuable space inside the vehicle. With the recent demand for lighter and more compact vehicles, mounting large and heavy measurement devices in vehicles is difficult. Moreover, even if space could be secured to mount a large transformer, large transformers consume a lot of power, resulting in significant power loss.

[0006] This invention has been made in view of the above circumstances, and aims to provide a small, lightweight, and low-loss impedance measurement system. [Means for solving the problem]

[0007] To achieve the above objective, the impedance measurement system according to the present invention is an impedance measurement system for measuring the internal impedance of a battery. The impedance measurement system comprises: a power supply microcontroller that generates a current waveform based on frequency and current information for generating an AC current for measurement; a drive transistor that is driven by the current waveform generated by the power supply microcontroller and outputs an AC current for measurement; a measuring device that determines the internal impedance of a battery based on the AC current for measurement and the voltage drop caused by flowing the AC current for measurement through the battery; and a discharge load that consumes current from the battery when the measuring device determines the internal impedance of the battery. [Effects of the Invention]

[0008] According to the present invention, the impedance measurement system can be configured to be small, lightweight, and have low loss.

Brief Description of Drawings

[0009] [Figure 1] (A) is a circuit diagram showing the configuration of an EIS measurement device that does not use a transformer in EIS measurement, (B) is a circuit diagram showing a modified configuration of the EIS measurement device shown in (A), and (C) is a circuit diagram showing a configuration in which a current control circuit is arranged instead of the AC current source of the EIS measurement device shown in (A). [Figure 2] (A) is an explanatory diagram for explaining the pulse wave generated by the current control circuit shown in FIG. 1(C), and (B) is an explanatory diagram for explaining a half-wave pulse wave. [Figure 3] It is a circuit diagram showing the configuration of the impedance measurement system according to Embodiment 1. [Figure 4] (A) is a waveform diagram showing the signal in the energization device of the impedance measurement system shown in FIG. 3, and (B) is a flowchart showing the operation flow of the measurement device and the energization device. [Figure 5] It is an example of a table storing the combination of the frequency and waveform of the AC current input to the energization device of the impedance measurement system shown in FIG. 3. [Figure 6] It is a sequence diagram showing the operation of the impedance measurement system according to Embodiment 1. [Figure 7] It is a flowchart showing the energization process of the energization device according to Embodiment 1. [Figure 8] It is a circuit diagram showing the configuration of the impedance measurement system according to Embodiment 2. [Figure 9] It is a waveform diagram showing the signal in the energization device shown in FIG. 8. [Figure 10] It is a circuit diagram showing the configuration of the impedance measurement system according to Embodiment 3.

Modes for Carrying Out the Invention

[0011] (Embodiment 1) As an EIS measurement device that does not use a transformer, the circuit configuration shown in Fig. 1(A) is assumed. In this configuration, the EIS measurement device includes a current sensor 111, a current limiting resistor 112, an alternating current source 113, and a voltage sensor 114. The current sensor 111 is connected in series to the secondary battery SBT to be measured. A series circuit of the current limiting resistor 112 and the alternating current source 113 is connected in parallel to the series circuit of the secondary battery SBT and the current sensor 111. The current sensor 111 measures the alternating current Is flowing through the secondary battery SBT, and the voltage sensor 114 measures the voltage Vss between the electrodes of the secondary battery SBT. The internal impedance of the secondary battery SBT can be obtained from Vss / Is.

[0012] However, in the case of this circuit configuration, current flows from the secondary battery SBT to the current limiting resistor 112, resulting in power loss due to heat generation. For example, secondary batteries used as vehicle power sources often have a high voltage of several hundred volts. Assuming that the current flowing from the secondary battery is 1 ampere, heat generation of several hundred watts occurs in the discharge load. Therefore, heat dissipation treatment becomes an issue.

[0013] As shown in Fig. 1(B), a configuration in which a coupling capacitor 115 for cutting off the direct current component is arranged in series with the current limiting resistor 112 is also conceivable. However, in this configuration, although the loss due to the current flowing from the secondary battery SBT to the current limiting resistor 112 can be suppressed, the cost increases due to the arrangement of the coupling capacitor 115, the device size becomes larger, and new problems such as the shorter life of the coupling capacitor 115 compared to other components occur.

[0014] Furthermore, to simplify the circuit configuration, as shown in Figure 1(C), a current control circuit 116 can be placed in place of the AC current source 113. As shown in Figure 2(A), the current control circuit 116 controls the magnitude of the current flowing from the secondary battery SBT to the current limiting resistor 112, thereby generating an effective AC current (pulsating current), and this pulsating current can be used to measure the impedance of the secondary battery SBT. However, even with this configuration, the problem of large current flowing through the current limiting resistor 112 and resulting losses remains.

[0015] If R is the resistance of the current-limiting resistor 112 and I is the current due to the discharge of the secondary battery SBT, then the power loss Ps across the current-limiting resistor 112 is Ps = I 2 *It can be expressed as R. Also, if the current is halved, the power loss Ps = (1 / 2I) 2* R = 1 / 4I 2 *R. In other words, reducing the current caused by the discharge of the secondary battery SBT can significantly reduce power loss Ps.

[0016] More specifically, if the alternating current component to be supplied to the secondary battery SBT is a sine wave with a peak value of 0 to AC amperes, and the measurement time (supply time) is tm and the frequency is f, then the current is I(tm) = AC(1 + sin(2πf*tm). If the peak value (amplitude) of the sine wave is halved, the current becomes (AC / 2)*(1 + sin(2πf)*tm), and the current can be reduced. However, reducing the current used for measurement worsens the signal-to-noise ratio (SNR) due to rebound, which may reduce the accuracy of detecting the state of the secondary battery SBT.

[0017] Therefore, in this embodiment 1, as a countermeasure against rebound, the AC current source is provided with a mechanism that switches the waveform and energizing time according to the frequency and the temperature of the discharge load, without reducing the peak value (amplitude). Furthermore, the insufficient signal-to-noise ratio is compensated by the number of multiple averaging operations (length of measurement time).

[0018] For example, if the alternating current output from an alternating current source is a half-wave with a peak value of 0 to AC amperes, when the period for outputting the half-wave is T, the interval time for suspending energization is Ti, and the measurement time is tm, the current amount is I(tm) = AC * sin(2πf * tm - α) [0 ≤ tm < T / 2, α = 90 deg], or 0 [T / 2 ≤ tm < T]. Without reducing the peak value (amplitude), it becomes possible to substantially halve the current amount. As a result, the current I due to the discharge of the secondary battery can be halved, so the power loss in the discharge load can be reduced to 1 / 4. Furthermore, by offset-adjusting T and Ti, it is possible to adjust the heat generation amount and the heat dissipation amount to prevent the current limiting resistor 112 from heating up.

[0019] If the voltage of the secondary battery SBT is 400 volts and the current flowing from the secondary battery SBT to the current limiting resistor 112 is decreased from 1 ampere to 0.5 amperes, which is half, the power loss in the discharge load decreases from 400 watts to 100 watts. If the power consumption is about 100 watts, an in-vehicle resistor such as a battery heater can be used as the discharge load without providing a dedicated current limiting resistor 112. Therefore, in the first embodiment, the battery heater is also used as the discharge load. As a result, the number of parts can be increased without increasing, and additional costs and the weight of the vehicle can be suppressed. Hereinafter, specifically, the first embodiment will be described.

[0020] Figure 3 is a configuration diagram showing the configuration of the impedance measurement system 100 according to this embodiment 1. The impedance measurement system 100 includes a battery pack 1, a measuring device 2, and a BMS (Battery Management System) 3. The battery pack 1 includes a battery 11, a battery heater 12, a temperature sensor 13, a power supply device 14, a relay 15, and a shunt resistor 16. The battery 11 is made up of a rechargeable battery such as a lithium-ion battery. In Figure 3, the battery 11 is represented by an equivalent circuit divided into electromotive force 1101 and internal impedance 1102. The internal impedance 1102 will have a different value than when the battery 11 is degraded or when an abnormality occurs. Therefore, the degradation of the battery 11, the occurrence of an abnormality, etc. can be determined by the change in the measured value of the internal impedance 1102.

[0021] The battery heater 12 is a resistor that serves as a heat source for warming the battery 11. The temperature sensor 13 is a sensor that measures the temperature of the battery heater 12. When measuring the internal impedance 1102 of the battery 11, the power supply device 14 controls the output of the AC current for measurement according to instructions from the measurement microcontroller of the measurement device 2, which will be described later. The power supply device 14 also controls the output of the AC current for measurement according to the heater temperature of the battery heater 12 measured by the temperature sensor 13. The power supply device 14 includes a power supply microcontroller 141, a D / A converter 142, a drive amplifier 143, and a discharge drive transistor 144.

[0022] The power supply microcontroller 141 is equipped with a processor and memory, and executes a program according to parameters. By changing these parameters, the frequency and amplitude of the AC current, the number of repetitions, the application period, the pause period, etc., can be adjusted. The power supply microcontroller 141 obtains the heater temperature of the battery heater 12 from the temperature sensor 13 and controls whether or not to supply AC current to the battery 11 according to the heater temperature. The D / A converter 142 operates according to instructions from the power supply microcontroller 141 and converts digital data for generating the AC current to be measured into analog data (voltage signal). The drive amplifier 143 amplifies the voltage signal converted by the D / A converter 142 and supplies it to the discharge drive transistor 144. The discharge drive transistor 144 operates according to the supplied voltage signal and outputs a current signal that is in phase and has the same waveform as the voltage signal.

[0023] Relay 15 is a switch that controls the power supply to the battery heater 12 when the battery heater 12 is used as a heat source to warm the battery 11. Relay 15 is connected to the BMS 3 and turns on / off according to instructions from the BMS 3. Shunt resistor 16 is a resistor used to measure the alternating current output from the energizing device 14 and functions as a current measuring instrument.

[0024] The measuring device 2 is a device for measuring the internal impedance 1102 of the battery 11 of the battery pack 1. The measuring device 2 includes differential amplifiers 21 and 26, bandpass filters 22 and 27, amplification amplifiers 23 and 28, A / D converters 24 and 29, and a measuring microcontroller 25. The measuring microcontroller 25 has a processor and memory and operates by executing a program. The measuring microcontroller 25 is connected to the BMS3 and, in response to instructions from the BMS3, measures the AC voltage generated in the battery 11 by the AC current output from the power supply device 14 of the battery pack 1 (voltage drop due to the internal impedance 1102 of the battery 11) and the AC voltage generated in the shunt resistor 16 with a known resistance value r (voltage drop due to the shunt resistor 16). The measuring microcontroller 25 divides the AC voltage of the shunt resistor 16 by the resistance value r to obtain the current flowing through the shunt resistor 16, i.e., the AC current flowing through the battery 11. The measuring microcontroller 25 calculates the internal impedance 1102 by dividing the measured AC voltage (voltage drop due to the internal impedance 1102 of the battery 11) by the measured AC current (AC current flowing through the battery 11).

[0025] More specifically, the differential amplifier 21 differentially amplifies the voltage across the battery 11 and outputs it. The bandpass filter 22 removes high-frequency components such as noise and low-frequency components such as DC components from the differentially amplified voltage signal, allowing only a specific frequency band to pass through. The amplification amplifier 23 amplifies the signal that has passed through the bandpass filter 22 and supplies it to the A / D converter 24. The A / D converter 24 converts the amplified analog signal into digital data and supplies it to the measurement microcontroller 25.

[0026] Furthermore, the differential amplifier 26 differentially amplifies the voltage across the shunt resistor 16 and outputs it. The bandpass filter 27 removes high-frequency components such as noise and low-frequency components such as DC components from the differentially amplified voltage signal, allowing only a specific frequency band to pass through. The amplification amplifier 28 amplifies the signal that has passed through the bandpass filter 27 and supplies it to the A / D converter 29. The A / D converter 29 converts the amplified analog signal into digital data and supplies it to the measurement microcontroller 25.

[0027] The measuring microcontroller 25 determines the voltage drop across the shunt resistor 16 from the digital data supplied from the A / D converter 29, and calculates the current flowing through the shunt resistor 16 by dividing the voltage drop by the known resistance value r of the shunt resistor 16. The measuring microcontroller 25 calculates the value of the internal impedance 1102 by dividing the AC voltage generated in the battery 11, as indicated by the data supplied from the A / D converter 24, by the value of the current flowing through the shunt resistor 16, and provides this value to the BMS3. The BMS3 then uses the value of the internal impedance 1102 at the specified measurement frequency to diagnose the state of the battery 11.

[0028] The BMS3 is a system that monitors the remaining charge, degradation status, and presence of abnormalities of the battery 11, and controls it to ensure that the battery 11 can be used safely for a long period of time. The BMS3 is connected to the VCU (Vehicle Control Unit), which centrally manages power supply equipment, drive equipment, etc., installed in the vehicle, and the BMS3 instructs the measuring device 2 to measure the status of the battery 11 of the battery pack 1 based on instructions from the VCU. When the BMS3 receives an instruction from the VCU to check the status of the battery 11 of the battery pack 1, it transmits digital data of frequency f to the measuring microcontroller 25 of the measuring device 2 to generate the AC current for measurement.

[0029] Furthermore, the measurement microcontroller 25 receives the frequency received from the BMS 3 and transmits digital data of the amplitude value (peak value) I of the AC current corresponding to the measurement frequency, which is pre-recorded in memory, and the number of repetitions (periods Tm) or the application period (time tm) to the power supply device 14 of the battery pack 1. Based on the received frequency f, amplitude value (peak value) I, and number of repetitions (periods Tm) or application period (time tm), the power supply device 14 determines the pause interval Ti by referring to a table (for example, Figure 5) pre-recorded in memory, and together with the received frequency, etc., AC current generation parameters for measurement are created, and according to these parameters, a digital code for AC current generation is sent from the power supply microcontroller to the DA converter. An example of this is shown in Figure 4(A). The left side of the double dashed line in the center shows the waveform when full-wave power is applied, and the right side shows the waveform when half-wave power is applied. The continuous hexagons on the output lines of the powered microcontroller represent the amplitude digital code for one conversion (e.g., 16 bits). When the microcontroller is fully powered, the digital code is output continuously in the time axis (horizontal direction). In contrast, when the microcontroller is half-powered, all the amplitude digital codes become zero (0 output) during the pause period, so the changes in the digital code appear discontinuous. Note that in Figure 4, the changes in the digital code are depicted as being minimal for illustrative purposes, but in reality, the output is dense in the time axis (horizontal direction).

[0030] Next, the operation of the impedance measurement system having the above configuration will be explained with reference to the flowchart shown in Figure 4(B). In Figure 4(B), the vertical axis shows the processing of the measurement microcontroller 25 and the power supply device 14 of the battery pack 1, and the heater temperature of the battery heater 12, while the horizontal axis shows the passage of time t.

[0031] First, the operation of the power supply device 14 and the measuring device 2 will be described. Assume that at time t1, a command for internal impedance measurement is issued from the BMS3 to the measuring microcontroller 25 of the measuring device 2. This command includes specifying the AC component of the current to be supplied to the battery 11 (hereinafter simply referred to as the frequency and amplitude of the AC current). The measuring microcontroller 25 notifies the power supply microcontroller 141 of the power supply device 14 of the frequency and amplitude of the AC current, the number of repetitions (number of periods Tm), or the application period (time tm). In response to the notification, the power supply microcontroller 141 sets the D / A converter 142 to an initial value of the amplitude, for example, 0 amperes. The power supply microcontroller 141 also obtains the temperature of the battery heater 12 from the temperature sensor 13.

[0032] At time t2, the measurement microcontroller 25 sends a power-on request to the power-on microcontroller 141 of the power supply device 14. The power-on microcontroller 141 turns on the D / A converter 142 in response to the power-on request, determines the pause interval Ti based on the frequency, amplitude, number of repetitions (period number Tm), or application period (time tm) received at t1, generates digital data for D / A conversion, and starts transmitting it to the D / A converter 142 at a predetermined conversion period (sampling). In addition, as a response to the AC current output command, the D / A converter 142 sends a power-on trigger signal to the measurement microcontroller 25 of the measurement device 2 to inform it of the actual power-on period. This power-on trigger signal is also used by the measurement microcontroller to diagnose whether the power supply device is functioning normally, and serves as a useful monitor signal as a reference signal for noise reduction such as synchronous detection.

[0033] The D / A converter 142 receives an AC voltage signal v corresponding to the digital code from the powered microcontroller 141. da It is sequentially converted to this. Here, the AC voltage signal v da This is a half-wave AC voltage. The D / A converter 142 receives the AC voltage signal v da The AC voltage signal v is input to the drive amplifier 143. The drive amplifier 143 receives the AC voltage signal v da The drive AC voltage v is amplified to drive the discharge drive transistor 144. trOutput. The discharge driving transistor 144 is, for example, an N-channel MOSFET. Since the discharge driving transistor 144 has the battery 11 connected to the drain as the power supply and the battery heater 12 connected as the load, an alternating current i tr with the same phase and waveform shape as the driving alternating voltage v s flows into the source. Here, a half-wave current flows as the alternating current i s . The measurement microcomputer 25 of the measuring device 2 measures the alternating current and alternating voltage when the alternating current i s is applied to the shunt resistor 16 and the battery 11, and calculates the internal impedance 1102 of the battery 11 from the measurement results.

[0034] During the measurement of the internal impedance 1102 of the battery 11, current flows from the battery 11 to the battery heater 12, and power is consumed in the battery heater 12 to generate heat. The energization microcomputer 141 continues to supply the alternating current i h to the shunt resistor 16 and the battery 11 while the heater temperature of the battery heater 12 measured by the temperature sensor 13 does not exceed the upper limit value T s . When the heater temperature of the battery heater 12 for measuring the internal impedance 1102 exceeds the upper limit value T h , at time t3, the energization microcomputer 141 instructs the D / A converter 142 to pause. The D / A converter 142 pauses the transmission of the energization trigger signal. When the transmission of the energization trigger signal pauses, the measurement microcomputer 25 of the measuring device 2 pauses the measurement. Thereafter, at time t4, when the energization microcomputer 141 confirms that the heater temperature of the battery heater 12 is lower than the upper limit value T h , the output of the D / A converter 142 is resumed, and accordingly, the transmission of the energization trigger signal is also resumed. When the transmission of the energization trigger signal resumes, the measurement microcomputer 25 of the measuring device 2 resumes the measurement of the internal impedance 1102 of the battery 11.

[0035] When measuring the internal impedance 1102 of the battery 11, it is desirable to reduce the total heat generated (total power loss) of the battery heater 12 during the measurement period as much as possible. Therefore, by using a half-wave AC current instead of a full-wave AC current when measuring the internal impedance 1102, the amount of current used for measurement can be reduced, thereby suppressing the total heat generated (total power loss) of the battery heater 12 during the measurement period.

[0036] Figure 5 shows an example of frequency and waveform combinations for the AC current used for measurement in this embodiment 1. In the table shown in Figure 5, the frequencies are listed in descending order from highest to lowest. The energizing time for each frequency can be arbitrarily determined, taking into account the balance between heating of the battery heater 12 by energizing and heat dissipation during the energizing pause interval. In this embodiment 1, it is desirable that the AC current waveform be a half-wave waveform in order to suppress the total heat generation of the battery heater 12. However, if there is sufficient heat generation capacity in the battery heater 12, it is also possible to energize with a full-wave waveform. In particular, when using high frequencies in measurements, energizing with a full-wave waveform can improve the signal-to-noise ratio of the measurement.

[0037] For example, if the amount of heat dissipated is greater than the heat capacity of the battery heater 12 body, the energizing time T m and rest interval T i By keeping the measurement time the same, the temperature rise can be kept constant, and as a result, the cumulative temperature rise can be suppressed. Also, since the energizing time is longer at low frequencies than at high frequencies, it is desirable to reduce the current by using a half-wave waveform at low frequencies. Furthermore, in the case of nearly DC frequencies such as 0.1 Hz, the waveform is halved and the current value is reduced. For example, at a frequency of 0.1 Hz, if the current value is half that of other frequencies (0.5 A in Figure 3), the power consumption becomes 1 / 4 and the heat generation can also be suppressed to 1 / 4. In addition, at low frequencies, the rest interval (waiting time) between measurements at the next frequency should be set to be longer. For example, it should be the same amount as the measurement time (= period number Tm).

[0038] Furthermore, by measuring frequencies in descending order from high frequencies (1,000 Hz to 0.1 Hz in Figure 5), the temperature rise of the battery heater 12 can be further suppressed. Since measurement is temporarily paused when the temperature of the battery heater 12 exceeds the upper limit of the heater temperature, suppressing the temperature rise of the battery heater 12 reduces the number of times measurement is paused, allowing the measurement to be completed more quickly.

[0039] The BMS3 stores data on combinations of AC current frequencies for measurement, and when measuring the internal impedance 1102 of the battery 11, it uses this data to instruct the measurement microcontroller 25 of the measurement device 2 to use the measurement frequency.

[0040] Next, the operation sequence of the impedance measurement system 100 will be explained with reference to the timing chart shown in Figure 6. It is desirable to measure the internal impedance 1102 of the battery 11 of the battery pack 1 after a certain period of time has elapsed since the vehicle stopped (after charging) when the ion concentration distribution inside the battery 11 has become uniform. Therefore, in Figure 6, the measurement is performed while the vehicle is stopped. First, while the vehicle is stopped, the VCU, which manages the entire vehicle, starts supplying power (timer start) to the power supply device 14, the measuring device 2, and the BMS3 of the battery pack 1 (step 1). This starts the BMS3, the power supply device 14, and the measuring device 2 (step 2). At this time, the BMS3 checks whether the relay 15 of the power supply device 14 should be turned on (i.e., whether the battery heater needs to be turned on). If the relay 15 needs to be turned on, the BMS3 maintains the on state, notifies the VCU that measurement is not possible because the battery heater 12 is in normal use, and does not issue an internal impedance measurement command to the measuring device 2.

[0041] Next, the power supply microcontroller 141 of the power supply device 14 activates the temperature sensor 13 that measures the temperature of the battery heater 12 (step 3). The VCU issues a diagnostic command for the battery 11 of the battery pack 1 to the BMS 3. In response, the BMS 3 transmits the measurement frequency Freq1 to the measurement microcontroller 25 of the measurement device 2 (step 4).

[0042] The measurement microcontroller 25 of the measurement device 2 transmits an energization command to the power supply device 14 of the battery pack 1, and sets the frequency Freq1 and the AC current value AC1 to period T. m1 The device transmits the following. The power supply device 14 generates a current for measurement based on the frequency Freq1 and the AC current value AC1 and outputs it to the battery 11 (step 5). The measurement microcontroller 25 of the measurement device 2 measures the AC voltage generated in the battery 11 and the current for measurement (step 6). The measurement microcontroller 25 of the measurement device 2 transmits the measurement results to the BMS3. The BMS3 diagnoses the State of Health (SOH) of the battery 11, such as deterioration or abnormalities, based on the measurement results (step 7). When the BMS3 finishes the diagnosis based on frequency Freq1, it returns to step 4. After the BMS3 finishes the diagnosis based on frequency Freq1, a pause interval T occurs. i1 Determine whether or not time has elapsed. i1 If the interval has not elapsed, BMS3 waits until it has elapsed. Once the interval has elapsed, BMS3 begins diagnosis using frequency Freq2. After the diagnosis using frequency Freq2 is complete, BMS3 enters a rest interval T. i2 After the specified time has elapsed, the command at frequency Freq3 will be executed.

[0043] Once the command for frequency Freq3 has been executed, BMS3 transmits the overall diagnostic results from SOH at each frequency to VCU. VCU retrieves the diagnostic results and performs predetermined recording processing (writing to non-volatile memory, etc., or sending to a cloud server). VCU stops the power supply and puts the power supply device 14 of the battery pack 1, the measuring device 2, and BMS3 into sleep mode. In conjunction with the power supply device going into sleep mode, the temperature sensor 13 also stops (step 8).

[0044] Furthermore, in step 5 of the timing chart described above, the power supply device 14 of the battery pack 1 performs the power supply process shown in Figure 7 and outputs an AC current to be applied to the battery 11. The power supply microcontroller 141 of the power supply device 14 determines whether or not there is a power supply instruction from the measurement microcontroller 25 of the measurement device 2 (step S1). If there is no power supply instruction (step S1; NO), the power supply microcontroller 141 repeats step S1. If there is a power supply instruction (step S1; YES), the power supply microcontroller 141 determines whether or not the heater temperature of the battery heater 12 measured by the temperature sensor 13 is below the upper limit (step S2). If the heater temperature exceeds the upper limit (step S2; NO), the power supply microcontroller 141 repeats step S2. If the heater temperature is below the upper limit (step S2; YES), the power supply microcontroller 141 receives the frequency Freq1 and the AC current value AC1 (digital data of amplitude width) from the measurement microcontroller 25 of the measurement device 2 (step S3).

[0045] The D / A converter 142 and discharge drive transistor 144 of the power supply device 14 generate and output an alternating current (step 4). The power supply microcontroller 141 determines whether the heater temperature of the battery heater 12, measured by the temperature sensor 13, is below the upper limit (step S5). If the heater temperature is below the upper limit (step S2; YES), the power supply microcontroller 141 then determines whether the entire vehicle system has stopped (step S6). This step is inserted, for example, as a response when a diagnostic command is issued while the user is using the vehicle. If the user turns off the key at this time, i.e., the entire vehicle system has stopped (step S6; YES), the power supply microcontroller 141 terminates the power supply process. If the entire vehicle system has not stopped (step S6; NO), the power supply microcontroller 141 returns to step S1 and executes steps S1 and beyond.

[0046] Furthermore, in step S5, if the heater temperature of the battery heater 12 exceeds the upper limit (step S5; NO), the energizing microcontroller 141 instructs the D / A converter 142 to pause and stops the output of AC current (step S7). This prevents the battery heater 12 from overheating. Note that this is shared with the BMS3, and a process for interrupting the diagnosis of the battery 11 may be executed, for example, by temporarily suspending the diagnosis and continuing at the next diagnostic timing.

[0047] The power-on microcontroller 141 determines whether the heater temperature of the battery heater 12, as measured by the temperature sensor 13, is below the upper limit (step S8). If the heater temperature exceeds the upper limit (step S8; NO), the power-on microcontroller 141 repeats step S8. If the heater temperature is below the upper limit (step S8; YES), the power-on microcontroller 141 resumes outputting the AC current (step S9). The power-on microcontroller 141 returns to step S1 and executes steps S1 and beyond.

[0048] As described above, in Embodiment 1, the frequency, waveform, and energization interval of the AC current for measurement can be controlled by the energizing device 14, allowing the existing on-board resistor, the battery heater 12, to also be used as a discharge load. This makes it possible to obtain an AC current for diagnosing the state of the battery 11 without being constrained by other on-board electrical units, while suppressing additional costs and weight increases, thus enabling the implementation of a small, lightweight, and low-loss impedance measurement system 100 in a vehicle.

[0049] Furthermore, the energizing device 14 according to Embodiment 1 can control the output of the AC current according to the heater temperature of the battery heater 12 measured by the temperature sensor 13. This makes it possible to prevent overheating of the battery heater 12 and avoid performing the diagnosis under inappropriate conditions, even when using a vehicle in a tropical region, or when it becomes necessary to diagnose the battery 11 immediately after high-load operation or rapid charging. Therefore, the reliability of the diagnosis results can be improved.

[0050] (Embodiment 2) In Embodiment 1, the battery heater 12 was used as the discharge load, but some small cars may not be equipped with a battery heater 12. Therefore, in Embodiment 2, a cabin heater used to heat the inside of the vehicle's cabin is used as the discharge load. This makes it possible to implement the impedance measurement system in the vehicle in the same way as in Embodiment 1, even in vehicles that are not equipped with a battery heater 12.

[0051] Figure 8 is a configuration diagram showing the configuration of the impedance measurement system 100A according to this embodiment 2. The impedance measurement system 100A includes a battery pack 1A, a measuring device 2, a BMS 3, a heater controller 7, and a cabin heater 8. The battery pack 1A includes a battery 11, a power supply device 14A, a relay 1407, and a shunt resistor 16. The power supply device 14A includes a power supply microcontroller 1401, a DC / DC power supply 1402, a bootstrap diode 1403, a bootstrap capacitor 1404, a drive amplifier 1405, a drive transistor 1406, and a relay 1407.

[0052] The power supply microcontroller 1401 is bidirectionally connected to the measurement microcontroller 25 of the measurement device 2. The power supply microcontroller 1401 receives the heater temperature of the cabin heater 8 from the heater controller 7 and determines whether or not it is below a predetermined upper limit of heater temperature. If the determination result is below the upper limit, the power supply microcontroller 1401 outputs AC current from the power supply device 14A. If the determination result exceeds the upper limit, the power supply microcontroller 1401 stops outputting AC current and transmits the determination result to the measurement microcontroller 25 of the measurement device 2.

[0053] The power supply microcontroller 1401 has a function to modulate the current waveform into pulse width (PWM), creating a constant cycle of on and off pulse trains and generating a waveform in which the on time width is changed according to the amplitude of the current waveform. When measuring the internal impedance 1102 of the battery 11 of the battery pack 1, the measurement microcontroller 25 of the measurement device 2 receives frequency and current information from the BMS 3 to generate the AC current for measurement. The measurement microcontroller 25 of the measurement device 2 transmits the received frequency and current information to the power supply microcontroller 1401 of the battery pack 1A. The power supply microcontroller 1401 generates a current waveform from the received frequency and current information and modulates it into pulse width, for example, as shown in Figure 9. In Figure 9, the left side of the double dashed line in the center shows the waveform when full-wave power is applied, and the right side shows the waveform when half-wave power is applied.

[0054] In the configuration shown in Figure 8, the heater controller 7 and cabin heater 8 are connected as loads to the source side of the drive transistor 1406. Therefore, when AC current flows through the load, the source potential Vs fluctuates, and it is necessary to supply a corresponding gate voltage to the drive transistor 1406. A useful solution is to create the power supply voltage Vbs of the drive amplifier 1405 by bootstrapping. Here, the DC / DC power supply 1402 of the energizing device 14A receives a DC voltage from a DC power source in the vehicle (e.g., a 12V battery), and connects it to the bootstrap capacitor 1404 via the bootstrap diode 1403 while electrically isolated from the battery 11, which is the drive power supply. The bootstrap capacitor 1404 stores the applied DC voltage. As a result, the power supply voltage Vbs of the drive amplifier 1405 is maintained at a predetermined voltage with reference to the source potential Vs of the drive transistor 1406. In other words, when alternating current flows, the cabin heater 8 generates heat for the first time, and as the resistance value of the cabin heater 8 changes, the predetermined voltage can be kept constant even if the source potential Vs changes, and consequently, the gate voltage of the drive transistor 1406 can also be kept constant.

[0055] In this way, a pulse signal is input to the gate of the drive transistor 1406 from the drive amplifier 1405. By using the pulse signal, the gate of the drive transistor 1406 can be efficiently switched on and off (switched), causing current to flow between the drain and source. Due to the parasitic reactance of the wiring and components in the circuit, the current flowing between the drain and source becomes an AC current waveform, which is the result of smoothing the pulse signal. For example, it takes the shape of the AC current waveform shown in Figure 9. The energizing device 14 outputs the AC current waveform, which is the result of smoothing the pulse signal, as an AC current for measuring the internal impedance 1102 of the battery 11 of the battery pack 1.

[0056] The alternating current output from the power supply device 14 flows to the shunt resistor 16 and the battery 11. Current from the battery 11 flows to the cabin heater 8 via the heater controller 7, causing the cabin heater 8 to generate heat. When the cabin heater 8 is used for heating the cabin rather than as a discharge load, the power supply microcontroller 1401 turns on the relay 1407 in response to instructions from the VCU. This hands over control of the cabin heater 8 to the heater controller 7. Therefore, the power supply control by the power supply device 14 is disabled. However, this occurs when the vehicle is in use and is not normally a suitable situation for battery diagnosis, so it does not hinder the effectiveness of this embodiment 2.

[0057] As described above, according to Embodiment 2, even in vehicles that do not have a battery heater 12, the impedance measurement system 100A can be implemented in the vehicle in the same way as in Embodiment 1. Furthermore, in Embodiment 2, the energizing microcontroller 1401 modulates the current waveform into a pulse signal and inputs it to the drive transistor 1406, thereby reducing the power loss of the drive transistor 1406. This makes it possible to further miniaturize and reduce the cost of the impedance measurement system 100A.

[0058] (Embodiment 3) In Embodiment 1, a battery heater 12 was used as the discharge load, and in Embodiment 2, a cabin heater 8 for warming the vehicle's cabin was used as the discharge load. However, in the case of vehicles, especially small cars, a battery heater 12 may not be installed, and the heater capacity (power consumption) of the cabin heater 8 may be small or unavailable. Therefore, in Embodiment 3, the internal resistance of a low-voltage battery is used as the discharge load. This allows the impedance measurement system to be implemented in the vehicle in the same way as in Embodiments 1 and 2, even if a battery heater 12 is not installed, and the heater capacity of the cabin heater 8 is small or unavailable.

[0059] Figure 10 is a configuration diagram showing the configuration of the impedance measurement system 100B according to this embodiment 3. The impedance measurement system 100B includes a battery pack 1B, a measuring device 2, a BMS 3, and a low-voltage battery 9. The battery pack 1B includes a battery 11, a power supply device 14B, and a shunt resistor 16. The power supply device 14B includes a power supply microcontroller 1411, a step-down converter 1412, a drive amplifier 1413, and a drive transistor 1414. The low-voltage battery 9 includes a low-voltage battery BMS 91 and a low-voltage battery temperature sensor 92. The low-voltage battery 9 is connected to the output of the step-down converter 1412.

[0060] The power supply microcontroller 1411 of the power supply device 14B is bidirectionally connected to the measurement microcontroller 25 of the measurement device 2. The power supply microcontroller 1411 is connected to the low-voltage battery BMS 91 of the low-voltage battery 9 and also receives the temperature of the low-voltage battery 9 measured by the low-voltage battery temperature sensor 92. The power supply microcontroller 1411 controls the output of the measurement current based on the low-voltage battery protection function information of the low-voltage battery BMS 91 and the measurement value of the low-voltage battery temperature sensor 92. Specifically, the power supply microcontroller 1411 determines whether the temperature of the low-voltage battery 9 is below a predetermined upper temperature limit and / or whether it is rechargeable according to the battery protection function information. If the determination result is below the upper limit and it is rechargeable, the power supply device 14B outputs the measurement current. If the determination result exceeds the upper limit or it is not rechargeable, the output of the measurement current is stopped and the determination result is transmitted to the measurement microcontroller 25 of the measurement device 2.

[0061] When measuring the internal impedance 1102 of the battery 11 of the battery pack 1, the measurement microcontroller 25 of the measurement device 2 receives frequency and current information from the BMS 3 to generate the measurement current. The measurement microcontroller 25 of the measurement device 2 transmits the received frequency and current information to the power supply microcontroller 1411 of the battery pack 1B. The power supply microcontroller 1411 has a PWM function and generates a pulse signal (voltage signal) based on the received frequency and current information.

[0062] The step-down converter 1412 operates by stepping down the voltage supplied from the battery 11 by the drive transistor 1406 and supplying power (charging) to the electrically isolated low-voltage battery 9.

[0063] When a pulse signal is supplied to the gate of the drive transistor 1414 from the drive amplifier 1413, the gate of the drive transistor 1414 is switched on, and current flows between the drain and source. Due to the parasitic reactance of the wiring and components in the circuit, the current flowing between the drain and source becomes a pulse wave, which is a smoothed version of the pulse signal. The energizing device 14 outputs the pulse wave as a current to measure the internal impedance 1102 of the battery 11 of the battery pack 1. The current is supplied to the shunt resistor 16 and the battery 11. The measuring microcontroller 25 of the measuring device 2 measures the current flowing through the shunt resistor 16 and the voltage drop across the battery 11, and calculates the internal impedance 1102 of the battery 11. The measuring microcontroller 25 transmits the calculated internal impedance 1102 to the BMS3. The BMS3 diagnoses the state of the battery 11 based on the received internal impedance 1102.

[0064] As described above, according to Embodiment 3, even in vehicles that do not have a battery heater 12 and whose cabin heater 8 has a small or unavailable heater capacity, the impedance measurement system 100B can be implemented in the vehicle in the same way as in Embodiments 1 and 2.

[0065] (modified version) The present invention is not limited to the embodiments described above, and various modifications are, of course, possible without departing from the spirit of the invention.

[0066] In the above embodiment 1, the power supply microcontroller 141 of the power supply device 14 controls the analog AC current i in Although it is stated that this will be generated, it may also be modulated to pulse width using PWM. Furthermore, in the energizing device 14A of Embodiment 2 and the energizing device 14B of Embodiment 3, the AC current is modulated to pulse width using PWM, but the analog AC current i in It may also be used to generate [something].

[0067] Furthermore, the power supply device 14 of Embodiment 1, the power supply device 14A of Embodiment 2, and the power supply device 14B of Embodiment 3 may be used interchangeably.

[0068] The present invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the embodiments described above are for illustrative purposes only and do not limit the scope of the invention. In other words, the scope of the invention is indicated by the claims, not by the embodiments. Various modifications made within the scope of the claims and the equivalent significance of disclosure are considered to be within the scope of the invention. [Explanation of symbols]

[0069] 1, 1A, 1B…Battery pack, 2…Measuring device, 3…BMS, 7…Heater controller, 8…Cabin heater, 9…Low-voltage battery, 11…Battery, 12…Battery heater, 13…Temperature sensor, 14, 14A, 14B…Power supply device, 15, 1407…Relay, 16…Shunt resistor, 21, 26…Differential amplifier, 22, 27…Bandpass filter, 23, 28…Amplifier, 24, 29, 142…Converter, 25…Measurement microcontroller, 91…Low-voltage battery BMS, 92…Low-voltage battery temperature sensor, 100, 100A, 100B…Impedance measurement system M, 111...Current sensor, 112...Current limiting resistor, 113...AC current source, 114...Voltage sensor, 115...Coupling capacitor, 116...Current control circuit, 141, 1401, 1411...Power supply microcontroller, 143, 1405, 1413...Drive amplifier, 144...Discharge drive transistor, 145...Protection resistor, 1101...Electromotive force, 1102...Internal impedance, 1402...DC / DC power supply, 1403...Bootstrap diode, 1404...Bootstrap capacitor, 1406, 1414...Drive transistor, 1412...Step-down converter.

Claims

1. An impedance measurement system for measuring the internal impedance of a battery, A power supply microcontroller that generates a current waveform based on frequency and current information for generating AC current for measurement, A drive transistor that is driven by the current waveform generated by the power supply microcontroller and outputs the AC current for measurement, A measuring device for determining the internal impedance of a battery based on the AC current for measurement and the voltage drop generated by flowing the AC current for measurement through the battery, When the measuring device determines the internal impedance of the battery, it uses a discharge load that consumes current from the battery, Equipped with, Impedance measurement system.

2. The discharge load is one of the following: a battery heater for warming the battery, a cabin heater for warming the cabin, or the internal resistance of a low-voltage battery. The impedance measurement system according to claim 1.

3. The system further includes a temperature sensor for measuring the temperature of the discharge load, The power supply microcontroller controls the output of the AC current for measurement from the drive transistor according to the measurement result from the temperature sensor. The impedance measurement system according to claim 1.

4. The current waveform generated by the aforementioned power-conducting microcontroller is either a full-wave waveform or a half-wave waveform. An impedance measurement system according to any one of claims 1 to 3.

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