BATTERY ELECTRONICS CONTROL UNIT CALIBRATION PROCEDURE

Abstract

A calibration procedure for a battery electronic control unit (ECU) according to the present disclosure uses a test apparatus. The battery ECU has a first radio frequency signal supply unit that delivers a first radio frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery, and a first sensing unit that detects a value of a real part of the AC impedance from the lithium-ion secondary battery to which the first radio frequency signal has been delivered. The test apparatus can detect the value of the real part of the AC impedance from the lithium-ion secondary battery with higher precision than the battery ECU. In the battery ECU calibration procedure, an ECU impedance measurement is obtained during a shipping test process of the lithium-ion secondary battery by detecting the value of the real part of the AC impedance of the lithium-ion secondary battery using the battery ECU.

Description

BACKGROUND OF THE INVENTION 1. Field of the invention The present disclosure relates to a calibration method for a battery electronic control unit (ECU). 2. Description of the state of the art There is a need to suppress the deposition of metallic lithium (Li) (hereinafter referred to as "Li deposits") in lithium-ion secondary batteries to prevent a deterioration in the performance of these batteries. However, no non-destructive method for detecting Li deposits in lithium-ion secondary batteries was known. To solve this problem, the inventors developed a technique for detecting a real part of the AC impedance of a lithium-ion secondary battery using high-frequency signals and for calculating a quantity of Li in the lithium-ion secondary battery based on a difference between a current value and an initial value of the real part of the AC impedance, as apparently disclosed in Japanese patent application No. 7347451 (JP 7347451 B ). OVERVIEW OF THE INVENTION Nowadays, lithium-ion secondary batteries include components such as built-in sensors, wiring harnesses, and so on. There have been concerns that variations between such components could reduce the precision of impedance measurements. The present disclosure was made taking into account the above-mentioned problem and provides a calibration procedure for a battery ECU which can suppress the risk of a reduction in the precision of the impedance measurement. A calibration method for calibrating a battery ECU according to the present disclosure is a calibration method for calibrating the battery ECU using a test apparatus in which the battery ECU has a first radio frequency signal supply unit that supplies a first radio frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery, and a first sensing unit that detects a value of a real part of an AC impedance from the lithium-ion secondary battery to which the first radio frequency signal has been supplied, and the test apparatus detects the value of the real part of the AC impedance from the lithium-ion secondary battery with higher precision than the battery ECU, wherein the calibration method comprises detecting an ECU impedance measurement in a shipping test process of the lithium-ion secondary battery using the battery ECU.to acquire the value of the real part of the AC impedance of the lithium-ion secondary battery, Acquire a test device impedance measurement using the test device to acquire the value of the real part of the AC impedance of the lithium-ion secondary battery, Notify the battery ECU of the test device impedance measurement, and Calibrate the first acquisition unit using a difference between the ECU impedance measurement and the test device impedance measurement as the calibration value. In the calibration procedure described above, the first high-frequency signal supply unit can deliver the first high-frequency signal of 0.5 MHz or higher to the lithium-ion secondary battery. In the calibration procedure described above, the lithium-ion secondary battery can have a plurality of battery cells, and the calibration procedure can further include: acquiring the ECU impedance measurement using the battery ECU in the shipping test process for the lithium-ion secondary battery, by having the first radio frequency signal supply unit deliver the first radio frequency signal to at least one battery cell among the battery cells, and by having the first sensing unit acquire the value of the real part of the AC impedance of the at least one battery cell; and acquiring the test device impedance measurement using the test device, by sensing the value of the real part of the AC impedance of the at least one battery cell. In the calibration procedure described above, the lithium-ion secondary battery can comprise a plurality of battery cells, and the calibration procedure can further include acquiring the test fixture impedance measurement value using the test fixture in the shipping test process for the lithium-ion secondary battery by acquiring the ECU impedance measurement value using the battery ECU by applying current to the battery cells such that a voltage value of the battery cells is within a predetermined range. The calibration procedure described above may further include capturing the ECU impedance measurement value during the shipping test process for the lithium-ion secondary battery by supplying an AC signal, which is a test signal generated by a three-phase inverter, to the lithium-ion secondary battery according to a specific switching pattern for supplying to the lithium-ion secondary battery, while the battery ECU is used to capture the value of the real part of the AC impedance of the lithium-ion secondary battery. According to the present disclosure, the risk of a reduction in impedance measurement precision can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS Features, advantages, and technical and industrial significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, in which identical symbols denote identical elements, and wherein: Fig. 1 is a block diagram representing a configuration example of a battery calibration system according to a first embodiment; Fig. 2 is a diagram relating to the state of health (SOH) of a secondary battery and the amount of change in a real part Z of the AC impedance when a 1 MHz radio frequency signal is supplied to the secondary battery; Fig. 3 is a diagram relating to a relationship between the frequency of an AC signal supplied to the secondary battery and the real part of the AC impedance detected from the secondary battery; Fig.Figure 4 is a diagram relating to the relationship between the frequency of the AC signal supplied to the secondary battery and the real part of the AC impedance detected by the secondary battery; Figure 5 is a diagram showing a specific configuration example of an impedance detection unit provided in the battery calibration system according to the first embodiment; Figure 6 is a diagram showing the attenuation characteristics of a radio frequency signal supplied to a secondary battery by a radio frequency signal supply unit when calculating the amount of Li deposition; Figure 7 is a time diagram describing the detection error of the peak voltage Vo due to variations between the components of the secondary battery; and Figure 8 is a flowchart showing a calibration procedure for a battery electronic control unit (ECU) according to the first embodiment. DETAILED DESCRIPTION OF THE EXECUTION FORMS Specific embodiments to which the present invention is applied are described in detail below with reference to the drawings. It should be noted, however, that the present invention is not limited to the following embodiments. The following description and the drawings have been simplified accordingly for clarity. First embodiment Fig. 1 is a block diagram illustrating a configuration example of a battery calibration system according to a first embodiment. As shown in Fig. 1, a battery calibration system 100 comprises a battery electronic control unit (ECU) 10, a secondary battery 20, and a test device 30. The battery ECU 10 manages the secondary battery 20. The battery ECU 10 and the secondary battery 20 can be installed in a vehicle, which is omitted from the illustration. The test device 30 examines the secondary battery 20 as its object and is preferably designed to be removable from the secondary battery 20. The battery calibration system 100 further comprises a three-phase inverter 40, which is powered by current from the secondary battery 20. Fig. 1 also shows a motor 50, which is driven by the three-phase inverter 40. The three-phase inverter 40 can supply alternating current or signals to the secondary battery 20. Secondary battery configuration 20 First, the secondary battery 20 is described. The secondary battery 20 is a lithium-ion secondary battery and consists of a cell stack made up of a multitude of battery cells 21 arranged in layers, and a housing that accommodates the cell stack. Each of the battery cells includes a cathode, an anode, and an ion transfer medium provided between the cathode and the anode, which conducts carrier ions. A separator may also be provided between the cathode and the anode. A resin such as polyethylene, polypropylene, or the like is used for the separator. The secondary battery 20 also includes components such as a built-in sensor, a wiring harness, and the like. A cathode active material is, for example, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like. In particular, the cathode active material uses a lithium-manganese compound oxide with a basic composition formula such as Li(1-x)MnO2 (where 0 < x < 1), Li(1-x)Mn2O4, or the like; a lithium-cobalt compound oxide with a basic composition formula such as Li(1-x)CoO2, or the like; a lithium-nickel compound oxide with a basic composition formula such as Li(1-x)NiO2, or the like; a lithium-nickel-cobalt-manganese compound oxide with a basic composition formula such as Li(1-x)NiaCobMncO2 (where a + b + c = 1), or the like, etc. It should be noted that a substance with the above-mentioned basic composition formula containing other elements can be used for the cathode active material.Aluminium (Al) or similar materials are used, for example, for a current collector of the cathode. The active material for the anode is, for example, a composite oxide containing lithium, a carbon material, or similar. Specifically, the active material of the anode can be an inorganic compound such as lithium, a lithium alloy, a tin compound, or similar; a carbon material capable of intercalating lithium ions; a composite oxide containing a variety of elements; a conductive polymer; or similar. Examples of carbon materials used for the anode active material include coke, glassy carbons, graphite, non-graphitizable carbons, pyrolytic carbons, carbon fibers, etc., with graphites such as synthetic graphite and natural graphite being preferred. Examples of composite oxides used for the anode active material include lithium-titanium composite oxides and lithium-vanadium composite oxides, etc.For example, copper (Cu) or similar materials are used for the current collector of the anode. An ionically conductive medium is used as the electrolyte solution, for example, when a carrier salt is dissolved. A lithium salt such as LiPF6, LiBF4, or the like is used as the carrier salt. The solvent for the electrolyte solution is, for example, one of the carbonates, esters, ethers, nitriles, furans, sulfolanes, and dioxolanes, or a mixture of several of these. Examples of carbonates include cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, etc., and linear carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl n-butyl carbonate, methyl tert-butyl carbonate, di-i-propyl carbonate, tert-butyl i-propyl carbonate, etc.Alternatively, a solid ionically conductive polymer, an inorganic solid electrolyte, a mixture of an organic polymer electrolyte and an inorganic solid electrolyte, an inorganic solid powder bound by an organic binder, or the like can be used as the ionically conductive medium. Now, in the secondary battery 20, metallic lithium is deposited on the electrode surfaces of each of the battery cells 21 through repeated charging. The lithium deposition progresses further with increasing charging power to increase the charging speed and leads to a deterioration of the state of health (SOH) of the secondary battery 20. It should be noted that the SOH of secondary battery 20 refers to the percentage of the current fully charged capacity of secondary battery 20 when the initial fully charged capacity is 100%. Battery ECU configuration 10 Next, the battery ECU 10, which manages the secondary battery 20, will be described. As shown in Fig. 1, the battery ECU 10 comprises a first high-frequency signal supply unit 11, a first sensing unit 12, a computing unit 13, a control unit 14, a storage unit 15, a communication unit 16, and a calibration unit 17, and manages the charging and discharging of the secondary battery 20 to be managed. The battery ECU 10 calculates the amount of Li stored in the secondary battery 20. The battery-ECU 10 comprises, as hardware, a processing unit (not shown in the figure), such as a central processing unit (CPU) or similar, in addition to a storage unit 15, such as random access memory (RAM), read-only memory (ROM), or similar, in which various types of programs and data, etc., are stored. That is to say, the battery-ECU 10 functions as a computer and performs various types of processing based on the aforementioned different types of programs and the like. Accordingly, the functional blocks of the first high-frequency signal supply unit 11, the first acquisition unit 12, the processing unit 13, the control unit 14, the storage unit 15, and the communication unit 16, which together form the battery-ECU 10 in Fig. 1, can be configured in terms of hardware using a CPU, memory, and other circuitry, and in terms of software using a program loaded into memory or the like. That is to say, each of the aforementioned functional blocks can be implemented in different configurations using computer hardware, software, or a combination thereof. The first high-frequency signal supply unit 11 delivers high-frequency signals to the secondary battery 20 for measuring the amount of Li deposits. In particular, the first high-frequency signal supply unit 11 delivers a first high-frequency signal of 0.1 MHz or higher to the battery cells 21 of the secondary battery 20. More precisely, the first high-frequency signal supply unit 11 delivers the first high-frequency signal of 0.1 MHz or higher to a battery cell 21a. The first high-frequency signal is preferably a high-frequency signal in which the value of the real part of the measured AC impedance is ten times or more greater, due to the skin effect, than the value of a real part Z of the AC impedance measured when a 1 kHz AC signal is delivered to the secondary battery 20. In particular, the frequency of the first high-frequency signal is preferably 0.5 MHz or higher. When the first high-frequency signal is delivered to the secondary battery 20, the diffusion, reaction, and movement of lithium ions in the individual battery cells 21 of the secondary battery 20 cannot keep pace. Consequently, due to the skin effect, the current of the first high-frequency signal flows across the electrode surfaces of the individual battery cells 21, where lithium readily deposits. The smaller the amount of lithium deposited, the lower the electrical conductivity of the electrode surface of each of the battery cells 21, and therefore the larger the value of the real part Z of the AC impedance. Conversely, the electrical conductivity of the electrode surfaces of each of the battery cells 21 increases with the amount of lithium deposited, and consequently, the value of the real part Z of the AC impedance decreases. A large current is then concentrated on the highly electrically conductive lithium metal, and consequently, the magnetic fields around the lithium deposited areas change, generating eddy currents. These eddy currents cause losses in the conductive sections of the current collector plates and electrodes, but reduce the overall losses in the battery.Accordingly, the change in the magnetic field is greater the larger the amount of Li deposit, and the eddy currents become correspondingly larger, thus decreasing the value of the real part Z. Therefore, the amount of Li deposit in the secondary battery 20 can be calculated from the magnitude of the change in the real part Z of the AC impedance (difference between the measured value and the initial value) measured from the secondary battery 20 supplied with the first radio frequency signal. Furthermore, the state of health (SOH) of the secondary battery 20 can also be estimated based on the amount of Li deposit. Fig. 2 is a diagram relating to the relationship between the SOH of the secondary battery 20 and the amount of the real part Z of the AC impedance (difference between the detected value and the initial value) when the 1 MHz high-frequency signal is supplied to the secondary battery 20. As indicated by the triangular markings in Fig. 2, under normal charging conditions with low charging power, the amount of Li deposits is small even with repeated charging. Consequently, the rate of change of the real part Z of the AC impedance remains small even if the deterioration of the state of health (SOH) progresses due to another factor. That is, the measured value of the real part Z of the AC impedance is maintained at a high value. On the other hand, as indicated by the circles in Fig. 2, in the case of fast charging with a high charging power, the amount of lithium deposition increases with repeated charging, and accordingly, the deterioration of the state of health (SOH) progresses accordingly, and the rate of change of the real part Z of the AC impedance becomes large. That is, the measured value of the real part Z of the AC impedance is low. It should be noted that if lithium deposition is a predominant cause of battery deterioration, the amount of lithium deposition can be derived from the SOH. Alternatively, the SOH can be derived from the amount of lithium deposition. Figures 3 and 4 are diagrams relating to the relationship between the frequency of the AC signal supplied to the secondary battery 20 and the real part of the AC impedance detected by the secondary battery 20. Figure 3 shows the value of the real part Z of the AC impedance when AC signals in the range of 1 kHz to 100 kHz are supplied to the secondary battery 20. Figure 4 shows the value of the real part Z of the AC impedance when AC signals in the range of 100 kHz to 100 MHz are supplied to the secondary battery 20. As shown in Fig. 3, the value of the real part Z of the AC impedance is minimal when an AC signal of approximately 1 kHz is supplied to the secondary battery 20. This impedance component represents an ohmic resistance component. As further shown in Figs. 3 and 4, due to the skin effect, the current flow concentrates on the electrode surface of each of the cells as the frequency of the AC signal supplied to the secondary battery 20 increases, thereby increasing the value of the real part Z of the AC impedance. Accordingly, the first high-frequency signal supply unit 11 provides the secondary battery 20 with an alternating current signal (i.e., the first high-frequency signal) with a frequency high enough to detect the value of the real part Z of the alternating current impedance, which is sufficiently high compared to the ohmic resistance component. The first sensing unit 12 acquires an ECU impedance measurement Ze from the secondary battery 20, which is supplied with the first radio frequency signal. The ECU impedance measurement Ze is the value of the real part Z of the AC impedance. As described above, the current of the first radio frequency signal, supplied to the secondary battery 20 by the first radio frequency signal supply unit 11, flows across the electrode surface (Li deposition area) of each of the battery cells 21 of the secondary battery 20 due to the skin effect. Furthermore, when the Li metal is electrically separated from the anode after Li deposition and is in a floating state, the current continues to flow across the Li metal due to inductive and capacitive coupling. Accordingly, the first sensing unit 12 can acquire the real part Z of the AC impedance corresponding to the amount of Li deposited. The processing unit 13 calculates the amount of lithium deposition in the secondary battery 20 based on the difference between the current value of the real part Z of the AC impedance, as detected by the first detection unit 12, and the initial value of the real part Z of the AC impedance of the secondary battery 20. Specifically, the larger the detected value of the real part Z of the AC impedance and the smaller the difference between the detected value and the initial value, the smaller the amount of lithium deposition calculated by the processing unit 13. Conversely, the smaller the detected value of the real part Z of the AC impedance and the larger the difference between the detected value and the initial value, the larger the amount of lithium calculated by the processing unit 13. It should be noted that, for example, an initial value of the real part Z of the AC impedance of the secondary battery 20 is stored in the memory unit 15. Furthermore, the memory unit 15 can store map information relating to a relationship between a difference (quantity) between the current value (detected value) and the initial value of the real part Z of the AC impedance of each type of secondary battery and the quantity of Li-ion. It is advantageous if the memory unit 15 stores the ECU impedance measurement Ze. This map information is information obtained in advance, for example through experiments or similar methods, but can also be updated, if necessary, using information acquired from the secondary battery 20, such as the ECU impedance measurement Ze and a test device impedance measurement Zi, which are described below. Using the map information, the processing unit 13 extracts the amount of Li-ion that corresponds to the value of the real part Z of the AC impedance acquired by the first acquisition unit 12 from the map information stored in the storage unit 15. The communication unit 16 acquires the test device impedance measurement value Zi from a communication unit 36 ​​(described later) of the test device 30 via a vehicle network. The storage unit 15 can store the test device impedance measurement value Zi. The calibration unit 17 calibrates the first detection unit 12 using the difference between the ECU impedance measurement Ze and the test device impedance measurement Zi as the calibration value. Configuration of the test device 30 Next, test device 30 will be described. As shown in Fig. 1, the test device 30 comprises a second high-frequency signal supply unit 31, a second acquisition unit 32, a computing unit 33, a control unit 34, a storage unit 35, and a communication unit 36. The test device 30 can acquire the value of the real part Z of the AC impedance from the secondary battery 20 with higher precision compared to the battery ECU 10. In this case, the test device 30, in addition to the storage unit 35, for example a RAM, a ROM or the like, which stores various types of programs and data, etc., includes as hardware a processing unit, not shown in the figure, for example a CPU or the like. That is to say, the test device 30 functions as a computer and performs various types of processing based on the aforementioned different types of programs and the like. Accordingly, the functional blocks of the second high-frequency signal supply unit 31, the second detection unit 32, the control unit 34, the storage unit 35, and the communication unit 36, which form the test device 30 in Fig. 1, can be configured with respect to the hardware using a CPU, memory, and other circuits, and can be implemented with respect to the software using a program loaded into memory or the like. That is, each of the aforementioned functional blocks can be implemented in various forms using computer hardware, software, or a combination thereof. The second high-frequency signal supply unit 31 provides the secondary battery 20 with a high-frequency signal for sensing the amount of deposited Li, similar to the first high-frequency signal supply unit 11. Specifically, the second high-frequency signal supply unit 31 provides a second high-frequency signal of 0.1 MHz or higher to the battery cells 21 of the secondary battery 20. More precisely, the second high-frequency signal supply unit 31 provides a second high-frequency signal of 0.1 MHz or higher to battery cell 21a. The second high-frequency signal is preferably a high-frequency signal in which the value of the real part of the AC impedance being sensed is, due to the skin effect, ten times or more greater than the value of the real part Z of the AC impedance being sensed when an AC signal of 1 kHz is supplied to the secondary battery 20.In particular, the frequency of the second high-frequency signal is preferably 0.5 MHz or higher. Furthermore, the second high-frequency signal supply unit 31 preferably provides the second high-frequency signal according to a specific switching pattern. The second sensing unit 32 detects the value of the real part Z of the AC impedance from the secondary battery 20, to which the second radio frequency signal is supplied, with higher precision than the first sensing unit 12. The second sensing unit 32 can have the same configuration as the first sensing unit 12, except for the detection precision of the value of the real part Z of the AC impedance. The current of the second radio frequency signal is similar to the current of the first radio frequency signal described above. That is, the current of the second radio frequency signal flows across the electrode surface (Li deposition area) of each of the battery cells 21 of the secondary battery 20 due to the skin effect. Furthermore, when the Li metal is electrically separated from the anode after Li deposition and is in a floating state, the current continues to flow across the Li metal due to inductive and capacitive coupling.Accordingly, the second detection unit 32 can detect the real part Z of the AC impedance according to the amount of deposited Li. The storage unit 35 can store the initial value of the real part Z of the AC impedance of the secondary battery 20 and the map information described above, similarly to the storage unit 15. The processing unit 33 can calculate the amount of deposited Li from the real part Z of the AC impedance detected by the second detection unit 32, similarly to the processing unit 13. The control unit 34 transmits the test device impedance measurement value Zi via the communication unit 36 ​​over the vehicle network to the communication unit 16 of the battery ECU 10. The test device impedance measurement value Zi includes, for example, the real part Z of the AC impedance detected by the second detection unit 32. Now, due to variance and the like in components of the secondary battery 20, an error may occur in the detected value of the real part Z of the AC impedance, which is detected by the first detection unit 12. Accordingly, in the battery ECU 10 according to the present embodiment, the detected error is calibrated, for example, during a shipping inspection process by the calibration unit 17. This allows the battery ECU 10 according to the present embodiment to reduce the risk of a decrease in the impedance measurement precision of the secondary battery 20. The following section first describes a specific example for configuring the first acquisition unit 12, and then describes errors that can occur in the first acquisition unit 12, as well as its calibration by the calibration unit 17. Specific example of the configuration of the first acquisition unit 12 Fig. 5 is a diagram showing a specific configuration example of the first sensing unit 12 provided in the battery ECU 10. The secondary battery 20 is also shown in Fig. 5. Fig. 6 is a diagram showing the attenuation characteristics of the first radio frequency signal supplied by the first radio frequency signal supply unit 11 to the secondary battery 20 when calculating the amount of deposited Li. It should be noted that the second sensing unit 32 can have the same configuration as the specific example shown in Fig. 5 for the configuration of the first sensing unit 12, except for the sensing precision. As shown in Fig. 5, the first detection unit 12 comprises a resonant circuit 121, a trigger signal output circuit 122, and a peak value storage circuit 123. The first detection unit 12 is further referred to as the impedance detection circuit. The resonant circuit 121 corresponds to the first high-frequency signal supply unit 11. The resonant circuit 121 is a circuit that oscillates in resonance at a high frequency (frequency of the high-frequency signal from the first high-frequency signal supply unit 11). In particular, the resonant circuit 121 comprises an inductor L1, a capacitor C1, a resistor R1, and a switch SW1. The resistor R1 is connected in parallel with the capacitor C1. The inductor L1, the capacitor C1, and the switch SW1 are connected in series between the cathode and the anode of the secondary battery 20. The trigger signal output circuit 122, for example, activates a trigger signal at the instruction of the control unit 14, which temporarily turns on the switch SW1. When the switch SW1 is turned on, the resonant circuit 121 begins to oscillate at a high frequency. The peak holding circuit 123 detects the value of the real part Z of the AC impedance of the secondary battery 20 based on the damping characteristics of the high-frequency signal supplied to the secondary battery 20. In particular, the peak-hold circuit 123 comprises an inductor L2, resistors R2 to R6, amplifiers A1 to A3, and switches SW2 to SW4. Inductor L2 is magnetically coupled to inductor L1 and receives the high-frequency signal flowing through inductor L1. Resistor R2 is connected between one end of inductor L2 and an inverting terminal of amplifier A1. Resistor R3 is connected between the other end of inductor L2 and a non-inverting terminal of amplifier A1. Resistor R4 is connected between an output terminal and the inverting input terminal of amplifier A1. Resistor R5 is connected between the non-inverting input terminal of amplifier A1 and ground.The amplifier A1 amplifies the high-frequency signal received by inductor L2 from inductor L1 and outputs the amplified signal as output voltage Vm. The amplifier (hereinafter referred to as the "comparator") A2 compares the output voltage Vm of amplifier A1 (amplified voltage of the high-frequency signal) with the output voltage Vo of amplifier A3 (output voltage of the peak-level memory circuit 123) and outputs a comparison result S1. For example, if the output voltage Vm of amplifier A1 is lower than the output voltage Vo of amplifier A3, the comparator A2 outputs a low-level comparison result S1, and if the output voltage Vm of amplifier A1 is equal to or greater than the output voltage Vo of amplifier A3, it outputs a high-level comparison result S1. Switch SW2 is located between an output terminal of amplifier A2 and a control terminal of switch SW3 and is controlled to be off during initialization and on otherwise. However, it should be noted that if signals of a large number of different frequencies are input for different time periods and only the amplitude of a signal of a specific frequency is to be recorded, switch SW2 can be controlled to be on only during the period in which the signal of that specific frequency is input, and off otherwise. Switch SW3 is connected between a supply voltage terminal, to which a supply voltage is applied, and node N1. Switch SW4 is connected between node N1 and ground. Resistor R6 is connected between node N1 and a non-inverting input terminal of amplifier A3. An output terminal and an inverting input terminal of amplifier A3 are connected together. Capacitor C2 is connected between the non-inverting terminal of amplifier A3 and ground. Switch SW3 is turned off when the low-level comparison result S1 of amplifier A2 is supplied via switch SW2, and turned on when the high-level comparison result S1 of amplifier A2 is supplied via switch SW2.The switch SW4 is controlled so that it is switched on when the charge stored in capacitor C2 is to be discharged to ground during initialization, and is switched off otherwise. For example, if the output voltage Vm of amplifier A1 is lower than the output voltage Vo of amplifier A3, switch SW3 remains off, and consequently, no additional charge is stored in capacitor C2. Thus, amplifier A3 maintains the output voltage Vo at its current value. Conversely, if the output voltage Vm of amplifier A1 is equal to or higher than the output voltage Vo of amplifier A3, switch SW3 turns on, and consequently, additional charge is stored in capacitor C2 for the duration that switch SW3 is turned on. This causes amplifier A3 to increase the output voltage Vo by a value corresponding to the increase in charge. By repeating this process, the output voltage Vo gradually approaches the peak voltage of the high-frequency signal and eventually reaches the peak voltage of the high-frequency signal or a voltage equivalent to it.Thus, the peak holding circuit 123 detects the peak voltage (Vo) of the high-frequency signal. It should be noted that the peak-hold circuit 123 detects the attenuation characteristics of the high-frequency signal based on the peak voltages of the high-frequency signal at two or more points and the detection intervals of these peak voltages. That is, the peak-hold circuit 123 detects the attenuation characteristics of the high-frequency signal based on the rate of change of the peak voltage Vo per unit of time. It should be noted that the calculation of the attenuation characteristics of the high-frequency signal can be performed in the processing unit 13. Peak voltage Vo measurement error due to deviations between the components of the secondary battery 20 Fig. 7 is a time diagram illustrating the detection error of the peak voltage Vo caused by variations between the components of the secondary battery 20. It should be noted that Fig. 7 shows one of the signal waveforms, which is convex in the positive direction, derived from the high-frequency signals represented by the voltage Vm. As shown in Fig. 7, the variance between the components of the secondary battery 20 can lead to fluctuations in the peak voltage Vm. In the example of Fig. 7, the voltage Vm10 detected by the battery ECU 10 includes an error ΔVerr compared to the voltage Vm30 detected by the test device 30. The voltage Vm includes the error ΔVErr, and furthermore, the voltage Vo naturally includes the error ΔVErr. Accordingly, the calibration unit 17 corrects the output voltage Vo of the peak-hold circuit 123 to eliminate the error voltage ΔVerr. Thus, the calibration unit 17 extracts the error voltage ΔVerr from the storage unit 15 and adds it to the output voltage Vo of the peak-hold circuit 123. This suppresses the detection error in the peak voltage Vo due to deviations between the components of the secondary battery 20. A different fault voltage ΔVerr can be stored in the storage unit 15 for each type of secondary battery 20 or for each individual product. The following describes a method for recording the fault voltage ΔVerr stored in the storage unit 15. First, the control unit 34 of the test device 30, in a test mode (which includes a normal operating mode and a test mode), causes the three-phase inverter 40 to generate an AC signal. This test signal has an amplitude and a cycle (pulse width) corresponding to the test parameters. The test signal is an AC signal with a frequency approximately equal to that of the high-frequency signal generated by the first high-frequency signal supply unit 11. This test signal generated by the three-phase inverter 40 is supplied to the secondary battery 20. Furthermore, the control unit 14 switches on switch SW1. The processing unit 13 then extracts the difference (e.g., fault voltage ΔVerr) between the peak voltage Vo of the test signal detected by the first detection unit 12 and the peak voltage Vo of the test signal detected by the second detection unit 32. Information about the extracted fault voltage ΔVerr is stored in the storage unit 15. It should be noted that the peak voltage Vo of the test signal detected by the second detection unit 32 has a higher accuracy than the peak voltage Vo of the test signal detected by the first detection unit 12. The control unit 34 instructs the three-phase inverter 40 to deliver a variety of test signals with different types of cycles and amplitudes to the secondary battery 20. The processing unit 13 extracts the difference (e.g., fault voltage ΔVerr) between the peak voltage Vo of each of the test signals detected by the first sensing unit 12 and the peak voltage Vo of the corresponding test signal detected by the second sensing unit 32, and stores this difference in the storage unit 15. Thus, the storage unit 15 stores a variety of combinations of second high-frequency signals with different waveform patterns and the corresponding fault voltages ΔVerr. This allows the battery ECU 10 to correct the detection error of the second detection unit 32 with high precision, even if the amplitude and cycle of the high-frequency signal differ. This enables the amount of Li stored in the secondary battery 20 to be detected with high precision. Calibration procedure Next, a calibration procedure according to the present embodiment, i.e., the operation of the battery calibration system 100, is described with reference to Fig. 8. Fig. 8 is a flowchart showing the calibration procedure according to the first embodiment. The calibration procedure according to the present embodiment can be used in the shipping inspection process of the secondary battery 20. First, the battery calibration system 100 acquires the value of the real part of the AC impedance of the secondary battery 20, using the battery ECU 10 to acquire the ECU impedance measurement Ze (step S101). The first radio frequency signal supply unit 11 can supply a first radio frequency signal to at least one battery cell 21, and the first acquisition unit 12 can acquire the value of the real part of the AC impedance of the at least one battery cell 21. In particular, the first radio frequency signal supply unit 11 supplies a first radio frequency signal to battery cell 21a, and the first acquisition unit 12 acquires the value of the real part of the AC impedance of the secondary battery 20 from battery cell 21a. The control unit 14 stores the value of the real part of the AC impedance of this secondary battery 20, which is detected, in the storage unit 15 as ECU impedance measurement value Ze. Next, the battery calibration system 100 acquires the value of the real part of the AC impedance of the secondary battery 20 using the test device 30 to acquire the test device impedance measurement Zi (step S102). The second acquisition unit 32 can acquire the value of the real part of the AC impedance of at least one battery cell 21. The second acquisition unit 32 preferably acquires the value of the real part of the AC impedance of the battery cell 21 that was acquired by the first acquisition unit 12 in step S101. In other words, the battery cell 21 acquired by the first acquisition unit 12 in step S101 and the battery cell 21 acquired by the second acquisition unit 32 in this step S102 are preferably identical.In particular, the second high-frequency signal supply unit 31 delivers a second high-frequency signal to battery cell 21a, and the second sensing unit 32 detects the value of the real part of the AC impedance of the secondary battery 20 from battery cell 21a. The control unit 34 stores the detected value of the real part of the AC impedance of the secondary battery 20 in the storage unit 35 as the test device impedance measurement value Zi. Furthermore, the three-phase inverter 40 can deliver a second high-frequency signal with the same frequency as the first high-frequency signal delivered in step S101. The three-phase inverter 40 also preferably delivers test signals according to a specific switching pattern. In step S102, the three-phase inverter 40 can deliver alternating current to battery cell 21a of the secondary battery 20. Next, the battery calibration system 100 communicates the test device impedance measurement Zi to the battery ECU 10 (step S103). Specifically, the control unit 34 of the test device 30 instructs the communication unit 36, and the communication unit 36 ​​transmits the test device impedance measurement Zi to the communication unit 16 of the battery ECU 10. The control unit 14 stores the test device impedance measurement Zi, acquired by the communication unit 16, in the memory unit 35. Finally, the battery calibration system 100 calibrates the first sensing unit 12 using the difference between the ECU impedance measurement Ze and the test device impedance measurement Zi as the calibration value (step S104). Specifically, the computing unit 13 increases or decreases the value of the real part of the AC impedance measured by the first sensing unit 12 to resolve the difference between the ECU impedance measurement Ze and the test device impedance measurement Zi. As described above, the test device 30 measures the value of the real part of the AC impedance from the secondary battery 20 with higher precision than the battery ECU 10. Thus, the computing unit 13 can calculate the amount of deposited Li with high precision by using the value of the real part of the AC impedance, which is measured with high precision. In this way, the battery ECU 10 can be calibrated by the battery ECU 10 by acquiring the calibration value of the first sensing unit 12. This can suppress the risk of a reduction in impedance measurement accuracy due to deviations between the components of the secondary battery 20, such as built-in sensors and wiring harnesses. Furthermore, the battery cell 21a detected by the first detection unit 12 in step S101 is the same as the battery cell 21a detected by the second detection unit 32 in this step S102. This allows the battery ECU 10 and the test device 30 to detect impedance measurements from the same battery cell 21a. Furthermore, in step S101, the three-phase inverter 40 applies current to the battery cells 21 so that the voltage values ​​of the battery cells 21 are within a predetermined range, thereby acquiring the ECU impedance measurement Ze using the battery ECU 10. Furthermore, in step S102, the test device 30 is used to acquire the test device impedance measurement Zi. This allows the effects of the voltage value of the battery cell 21 on the impedance to be suppressed. Furthermore, in step S102, the three-phase inverter 40 supplies test signals to the secondary battery 20 according to a specific switching pattern. Accordingly, impedance measurements can be recorded according to different switching patterns and highly precise calibration values ​​for the second acquisition unit 32 can be acquired. It should be noted that the present invention is not limited to the embodiments mentioned above and can be modified accordingly without altering its spirit and scope. Furthermore, the present invention can be carried out by a suitable combination of the embodiments and examples mentioned above. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature JP 7347451

[0003] JP 7347451 B

[0003]

Claims

Calibration method for calibrating a battery electronic control unit (ECU) using a test apparatus, wherein the battery ECU comprises a first radio frequency signal supply unit that supplies a first radio frequency signal of 0.1 MHz or higher to a lithium-ion secondary battery, and a first sensing unit that senses a value of a real part of an AC impedance from the lithium-ion secondary battery to which the first radio frequency signal has been supplied, and the test apparatus senses the value of the real part of the AC impedance from the lithium-ion secondary battery with higher precision than the battery ECU, wherein the calibration method comprises: sensing an ECU impedance measurement in a shipping test process of the lithium-ion secondary battery using the battery ECU to sense the value of the real part of the AC impedance of the lithium-ion secondary battery.Acquiring a test fixture impedance measurement using the test fixture to acquire the value of the real part of the AC impedance of the lithium-ion secondary battery, notifying the battery ECU of the test fixture impedance measurement, and calibrating the first sensing unit using a difference between the ECU impedance measurement and the test fixture impedance measurement as the calibration value. Calibration method according to claim 1, wherein the first high-frequency signal supply unit supplies the first high-frequency signal of 0.5 MHz or higher to the lithium-ion secondary battery. Calibration method according to claim 1 or 2, wherein the lithium-ion secondary battery comprises a plurality of battery cells, the calibration method further comprising: acquiring the ECU impedance measurement using the battery ECU in the shipping test process for the lithium-ion secondary battery, wherein the first radio frequency signal supply unit delivers the first radio frequency signal to at least one battery cell among the battery cells and the first sensing unit acquires the value of the real part of the AC impedance of the at least one battery cell, and acquiring the test device impedance measurement using the test device, wherein the value of the real part of the AC impedance of the at least one battery cell is acquired. Calibration method according to claim 1 or 2, wherein the lithium-ion secondary battery comprises a plurality of battery cells, wherein the calibration method further comprises: capturing the test device impedance measurement value using the test device in the shipping test process for the lithium-ion secondary battery, by capturing the ECU impedance measurement value using the battery ECU by applying current to the battery cells such that a voltage value of the battery cells is within a predetermined range. Calibration method according to claim 1 or 2, further comprising: capturing the ECU impedance measurement value in the shipping test process for the lithium-ion secondary battery by supplying an AC signal, which is a test signal generated by a three-phase inverter, to the lithium-ion secondary battery according to a specific switching pattern for supplying to the lithium-ion secondary battery, while the battery ECU is used to capture the value of the real part of the AC impedance of the lithium-ion secondary battery.

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