DETECTION DEVICE, ELECTRICITY STORAGE DEVICE, MOBILE BODY, AND METHOD FOR DETECTING INTERNAL SHORT CIRCUIT

Abstract

To provide a detection device capable of detecting internal short circuit of a power storage cell.SOLUTION: A CPU 121 measures vibration G of a battery pack 60 using a first sensor 116. A voltage detection unit 110 always measures a cell voltage V of each of secondary battery cells 62. An analysis unit 125 performs a fast Fourier transformation (FFT) on an output signal of the first sensor 116 and an output signal of the voltage detection unit 110, so as to respectively find a frequency spectrum of the vibration G of the battery pack 60 and a frequency spectrum of the cell voltage V of each of the secondary battery cells 62. The CPU 121 determines that, when the two frequency spectra have the same peak frequency, internal short circuit has occurred in the corresponding secondary battery cell 62 while determining that, when the two frequency spectra have different peak frequencies, internal short circuit has not occurred in the corresponding secondary battery cell 62.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a technique for detecting an internal short circuit in a power storage cell. [Background technology]

[0002] One of the failure modes of a power storage cell is an internal short circuit. As a means for detecting the occurrence of an internal short circuit, Patent Document 1 listed below discloses a method based on the amount of self-discharge.

[0003] Patent Document 2 below discloses that if the number of times the voltage difference between secondary batteries exceeds a threshold is equal to or exceeds a specified number of times within a predetermined period, the secondary battery with the lowest voltage is determined to have an internal short circuit. This method describes that it is possible to detect abnormal voltage drops caused by the phenomenon of positive and negative elements repeatedly coming into and out of contact, such as soft shorts caused by vibrations of a moving object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-018482

[0005] [Patent Document 2] Japanese Patent Publication No. 2020-020732 Summary of the Invention [Problem to be solved by the invention]

[0006] To measure the self-discharge rate, it is necessary to measure the cell voltage of the storage cell over a long period of time. Furthermore, to avoid changes in cell voltage due to factors other than self-discharge, the cell cannot be charged or discharged during the measurement period.

[0007] The present invention was completed in light of the above circumstances, and discloses a technique for detecting an internal short circuit in a storage cell without using the self-discharge amount of the storage cell. [Means for solving the problem]

[0008] The detection device for detecting an internal short circuit in a storage cell detects the presence or absence of an internal short circuit in the storage cell based on the vibration and cell voltage of the storage cell.

[0009] A detection device for detecting an internal short circuit in a storage cell detects the presence or absence of an internal short circuit in the storage cell based on the frequency spectrum of a cell voltage during a period in which the storage cell is vibrating.

[0010] The present invention can be applied to a power storage device, a mobile body equipped with a power storage device, a method for detecting an internal short circuit, and a program for detecting an internal short circuit. [Effects of the Invention]

[0011] According to the present invention, an internal short circuit in a storage cell can be detected without using the self-discharge amount of the storage cell. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a side view of a vehicle according to a first embodiment; [Figure 2] Exploded perspective view of the battery [Figure 3] Plan view of a secondary battery cell [Figure 4] Cross section of line AA in Figure 3 [Figure 5] Side view of the electrode body seen from the X direction in Figure 3 [Figure 6] Block diagram showing the electrical configuration of a vehicle [Figure 7] Block diagram showing the electrical configuration of the battery [Figure 8] Cross-section of a secondary battery cell [Figure 9] Graph showing changes in vibration over time [Figure 10] Graph showing changes in cell voltage over time [Figure 11] Vibration Frequency Spectrum [Figure 12] Cell voltage frequency spectrum [Figure 13] Internal short circuit detection flow [Figure 14] Diagram showing cell voltage and vibration detection timing DETAILED DESCRIPTION OF THE INVENTION

[0013] <Detection device overview> The detection device for detecting an internal short circuit in a storage cell detects the presence or absence of an internal short circuit in the storage cell based on the vibration and cell voltage of the storage cell.

[0014] In this configuration, the presence or absence of an internal short circuit in a storage cell is detected based on the vibration and cell voltage of the storage cell. Vibration and cell voltage can be measured in a shorter time than the amount of self-discharge. Therefore, detection of an internal short circuit based on vibration and cell voltage can be performed in a shorter time than detection of an internal short circuit based on the amount of self-discharge. By adding vibration to the factors for determining the presence or absence of an internal short circuit, the presence or absence of an internal short circuit is determined based on the relationship between cell voltage and vibration. By basing the determination on the relationship between cell voltage and vibration, it is possible to prevent voltage fluctuations that are not dependent on vibration, such as changes in cell voltage due to charging and discharging, from being mistakenly determined to be an internal short circuit. Therefore, the presence or absence of an internal short circuit can be detected with high accuracy.

[0015] The detection device may detect the presence or absence of an internal short circuit in the storage cell by comparing a frequency spectrum of the vibration of the storage cell with a frequency spectrum of a cell voltage of the storage cell.

[0016] By comparing the frequency spectrum of the vibration of the storage cell with that of the cell voltage, it is possible to detect fluctuation components of the cell voltage that fluctuate with the same period as the vibration or a period close to the vibration. This makes it possible to accurately determine whether the fluctuation of the cell voltage is dependent on the vibration, and improves the accuracy of detecting internal short circuits.

[0017] When the peak frequencies at which the signal strength is maximum in the frequency spectra of the vibration of the storage cell and the cell voltage match, it may be determined that an internal short circuit has occurred in the storage cell.

[0018] If the peak frequencies at which the signal strength is greatest in the frequency spectrum of the vibration and the cell voltage match, it can be determined that the fluctuations in the cell voltage of the storage cell depend on the vibration, and therefore that the storage cell is suffering from an internal short circuit.

[0019] A detection device for detecting an internal short circuit in a storage cell may detect the presence or absence of an internal short circuit in the storage cell based on the frequency spectrum of the cell voltage during a period in which the storage cell is vibrating. By obtaining the frequency spectrum, it is possible to determine whether the cell voltage contains the same frequency component as the vibration of the storage cell, and therefore it is possible to detect whether the storage cell has an internal short circuit.

[0020] The power storage device may include a power storage cell, a voltage detection unit that detects the voltage of the power storage cell, and the detection device. With this configuration, it is possible to detect the presence or absence of an internal short circuit in the power storage device without using a dedicated inspection device. It is possible to detect the presence or absence of an internal short circuit even after shipment.

[0021] The energy storage device may include a first sensor that detects vibration of the energy storage cell. In this configuration, the first sensor can directly measure the vibration of the energy storage cell, thereby enabling accurate detection of the vibration of the energy storage cell. This allows for more accurate determination of the presence or absence of an internal short circuit.

[0022] The first sensor may be a triaxial sensor. With this configuration, vibrations can be detected regardless of the direction of the vibrations applied to the power storage cell, thereby reducing detection omissions.

[0023] <Embodiment 1> 1. Battery Description Fig. 1 is a side view of automobile 10, and Fig. 2 is an exploded perspective view of battery 50. Automobile 10 is an engine-driven vehicle and is equipped with battery 50. Fig. 1 shows only automobile 10 and battery 50, and omits other components that make up automobile 10. Automobile 10 is an example of a "mobile body," and battery 50 is an example of an "electricity storage device."

[0024] The battery 50 includes a battery pack 60, a circuit board unit 65, and a housing 71.

[0025] As shown in Fig. 2, the housing 71 includes a main body 73 and a lid 74 made of a synthetic resin material. The main body 73 is cylindrical with a bottom. The main body 73 includes a bottom portion 75 and four side portions 76. An upper opening 77 is formed at the upper end portion by the four side portions 76. In the following description, the depth direction of the housing 71 is defined as the X direction, the width direction of the housing 71 is defined as the Y direction, and the height direction of the housing 71 is defined as the Z direction.

[0026] The container 71 houses the battery pack 60 and the circuit board unit 65. The battery pack 60 has 12 secondary battery cells 62. The 12 secondary battery cells 62 are connected in three parallel connections and four in series. The circuit board unit 65 is disposed on top of the battery pack 60. In the block diagram of FIG. 7, the three secondary battery cells 62 connected in parallel are represented by one battery symbol. The secondary battery cells 62 are an example of a "storage cell."

[0027] The lid 74 closes the upper opening 77 of the main body 73. An outer peripheral wall 78 is provided around the periphery of the lid 74. The lid 74 has a protruding portion 79 that is generally T-shaped in plan view. The positive electrode external terminal 51 is fixed to one corner of the front portion of the lid 74 (the front left side in FIG. 2 ), and the negative electrode external terminal 52 is fixed to the other corner.

[0028] 3 and 4, the secondary battery cell 62 is configured by housing an electrode assembly 83 together with a non-aqueous electrolyte in a rectangular parallelepiped case 82. The secondary battery cell 62 is, for example, a lithium-ion secondary battery. The case 82 has a case body 84 and a lid 85 that closes the upper opening.

[0029] 5, the electrode assembly 83 has a separator 83S made of a porous resin film disposed between a negative electrode element 83N, which is made of a copper foil substrate coated with an active material, and a positive electrode element 83P, which is made of an aluminum foil substrate coated with an active material. Both of these elements are strip-shaped, and are wound flat so as to be able to be housed in a case body 84, with the negative electrode element 83N and the positive electrode element 83P offset from each other on opposite sides in the width direction relative to the separator 83S.

[0030] A positive electrode terminal 87 is connected to the positive electrode element 83P via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode element 83N via a negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 each comprise a flat base portion 90 and legs 91 extending from the base portion 90. A through hole is formed in the base portion 90. The legs 91 are connected to the positive electrode element 83P or the negative electrode element 83N.

[0031] The positive electrode terminal 87 and the negative electrode terminal 89 each comprise a terminal body 92 and a shaft 93 that protrudes downward from the center of the lower surface of the terminal body 92. Of these, the terminal body 92 and shaft 93 of the positive electrode terminal 87 are integrally molded from aluminum (a single material). In the negative electrode terminal 89, the terminal body 92 is made of aluminum, and the shaft 93 is made of copper, and these are assembled together. The terminal bodies 92 of the positive electrode terminal 87 and the negative electrode terminal 89 are arranged on both ends of the lid 85 via gaskets 94 made of an insulating material, and are exposed to the outside from these gaskets 94.

[0032] The lid 85 has a pressure relief valve 95. As shown in Fig. 3, the pressure relief valve 95 is located between the positive electrode terminal 87 and the negative electrode terminal 89. The pressure relief valve 95 opens to reduce the internal pressure of the case 82 when the internal pressure of the case 82 exceeds a limit value.

[0033] FIG. 6 is a block diagram showing the electrical configuration of the automobile 10, and FIG. 7 is a block diagram showing the electrical configuration of the battery 50. As shown in FIG.

[0034] As shown in FIG. 6, the automobile 10 includes an engine 20 as a drive device, an engine control unit 21, an engine starting device 23, an alternator 25 as a vehicle generator, a general electrical load 27, a vehicle ECU (Electronic Control Unit) 30, a battery 50, and the like.

[0035] The battery 50 is connected to a power line 37. The battery 50 is connected to the engine starting device 23, the alternator 25, and the general electrical load 27 via the power line 37.

[0036] The engine starting device 23 is a starter motor. When the ignition switch 24 is turned on, a cranking current flows from the battery 50, driving the engine starting device 23. The driving of the engine starting device 23 rotates the crankshaft, allowing the engine 20 to start.

[0037] The general electrical loads 27 are electrical loads mounted on the automobile 10, excluding the engine starting device 23. The general electrical loads 27 are rated at 12V and include an air conditioner, audio equipment, car navigation system, auxiliary equipment, and the like.

[0038] The alternator 25 is a vehicle generator that generates electricity using the power of the engine 20. When the amount of electricity generated by the alternator 25 exceeds the electrical load of the automobile 10, the battery 50 is charged by the alternator 25. When the amount of electricity generated by the alternator 25 is less than the electrical load of the automobile 10, the battery 50 discharges to make up for the lack of electricity generation.

[0039] The vehicle ECU 30 is communicatively connected to the battery 50 via a communication line L1, and is communicatively connected to the alternator 25 via a communication line L2. The vehicle ECU 30 receives SOC (State of Charge) information from the battery 50 and controls the amount of power generated by the alternator 25, thereby controlling the SOC of the battery 50.

[0040] The vehicle ECU 30 is communicatively connected to the engine control unit 21 via a communication line L3. The engine control unit 21 is mounted on the automobile 10 and monitors the operating state of the engine 20. The engine control unit 21 monitors the running state of the automobile 10 from the measured values ​​of instruments such as a speedometer. The vehicle ECU 30 obtains from the engine control unit 21 information on whether the ignition switch 24 is turned on or off, information on the operating state of the engine 20, and information on the running state of the automobile 10 (driving, stopped, idling stop, etc.).

[0041] 7, the battery 50 includes a current interruption device 53, a battery pack 60, a current sensor 54, a management device 100, a temperature sensor 115, and a first sensor 116. The battery 50 is a rated 12V battery.

[0042] The current interruption device 53, the battery pack 60, and the current sensor 54 are connected in series via power lines 55P and 55N. The power line 55P connects the positive external terminal 51 to the positive electrode of the battery pack 60. The power line 55N connects the negative external terminal 52 to the negative electrode of the battery pack 60.

[0043] The current interruption device 53 is provided on the positive power line 55P, and the current sensor 54 is provided on the negative power line 55N.

[0044] The current interrupter 53 can be a contact switch (mechanical) such as a relay, or a semiconductor switch such as an FET. The current interrupter 53 is normally controlled to be in the closed state. If an abnormality occurs in the battery 50, the current interrupter 53 is opened to cut off the current, thereby protecting the battery 50.

[0045] The current sensor 54 measures the current I [A] of the battery pack 60 and outputs an output signal at a level corresponding to the current value to the control device 120. The temperature sensor 115 is of a contact or non-contact type and measures the temperature [°C] of the battery pack 60 and outputs an output signal at a level corresponding to the temperature to the control device 120.

[0046] The first sensor 116 is fixed to the outside of the battery pack 60. The first sensor 116 detects vibration G of the battery pack 60 and outputs an output signal according to the level of vibration G to the control device 120. Vibration G can be detected from acceleration, speed change, or position change. In this example, vibration G is detected from changes in acceleration. The first sensor 116 is a three-axis sensor and can separately detect acceleration in directions along the X, Y, and Z axes. The first sensor 116 can also appropriately combine and decompose the acceleration in each of the X, Y, and Z axes to detect only the vibration component in any direction.

[0047] The management device 100 is provided on the circuit board unit 65. The management device 100 includes a voltage detection unit 110 and a control device 120.

[0048] The voltage detection unit 110 is connected to both ends of each secondary battery cell 62 by a signal line, measures the cell voltage V [V] of each secondary battery cell 62, and outputs an output signal corresponding to the level of the cell voltage V of each secondary battery cell 62 to the control device 120.

[0049] The control device 120 includes a CPU 121 having a calculation function, a memory 123 serving as a storage unit, an analysis unit 125, and a communication unit 127.

[0050] The control device 120 monitors the current I measured by each of the sensors 54, 110, 115, and the voltage V and temperature of each secondary battery cell 62, to monitor the state of the battery 50.

[0051] The control device 120 communicates with the vehicle ECU 30 via the communication unit 127. The control device 120 obtains from the vehicle ECU 30 information about the state of the automobile 10, such as whether the automobile 10 is parked or moving.

[0052] The memory 123 is a non-volatile storage medium such as a flash memory, an EEPROM, etc. The memory 123 stores a program for monitoring the state of the battery pack 60, an execution program for a decision flow for determining whether or not an internal short circuit has occurred, and data required for executing the program.

[0053] 2. Internal short circuits and their detection principles 8, an internal short circuit is a phenomenon in which a short circuit occurs between the positive electrode element 83P and the negative electrode element 83N due to a short-circuiting object D penetrating a separator 83S inside a secondary battery cell 62. It is known that an internal short circuit can occur, for example, due to metal deposition during charging or the inclusion of metal pieces (foreign matter).

[0054] 9 and 10 show the results of applying vibration G to a secondary battery cell 62 for a certain period of time and analyzing the cell voltage V during that period, with Fig. 9 showing the vibration waveform of the secondary battery cell 62 and Fig. 10 showing the voltage waveform of the secondary battery cell 62. The dashed dotted line a shows the voltage waveform of a secondary battery cell 62 in which an internal short circuit has occurred, and the solid line b shows the voltage waveform of a secondary battery cell 62 in which an internal short circuit has not occurred.

[0055] When an internal short circuit occurs, the cell voltage V fluctuates, and when no internal short circuit occurs, the cell voltage V is constant and does not fluctuate.

[0056] The fluctuation in the cell voltage V is thought to be caused by the application of vibration G to the secondary battery cell 62, which causes the short-circuiting object D to alternate between contacting the electrode element 83 (internal short circuit) and not contacting it (non-internal short circuit), thereby causing a change in the resistance inside the battery. The change ΔV in the cell voltage V is given by the following equation (1):

[0057] ΔV=(Ri / Rs)×E (1) Ri is the internal resistance of the secondary battery cell 62, Rs is the resistance value when the short-circuiting object D is conductive, and E is the cell voltage V.

[0058] Since the short-circuiting object D vibrates at approximately the same period as the secondary battery cell 62, it is considered that the cell voltage V fluctuates at the same period as or a close period to the vibration G. Therefore, based on the vibration G and cell voltage V of the secondary battery cell 62, it is possible to determine whether or not there is an internal short circuit in the secondary battery cell 62.

[0059] Fig. 11 shows the frequency spectrum of the vibration G applied to the secondary battery cell 62, and Fig. 12 shows the frequency spectrum of the cell voltage V of the secondary battery cell 62. In Fig. 11 and Fig. 12, the vertical axis represents signal strength and the horizontal axis represents frequency. The frequency spectrum is an intensity distribution obtained by breaking down the strength of the signal to be analyzed into each frequency component contained therein, and can be obtained, for example, by subjecting the signal to Fourier transform or the like.

[0060] 12(a) shows the frequency spectrum when no internal short circuit occurs. When no internal short circuit occurs, the voltage V of the secondary battery cell 62 remains constant regardless of the presence or absence of vibration G, and therefore only the frequency f0 (zero Hz) of the DC component is detected, with almost no frequency components in other bands being detected.

[0061] The data in Figure 12(b) is a frequency spectrum when an internal short circuit occurs. When an internal short circuit occurs, not only the frequency f0 of the DC component but also other frequency components f1 to f11 are detected. The cell voltage V shows a tendency for signal strength to be high in the frequency band f5 to f7, which is the same as the frequency components of the vibration G applied to the secondary battery cell 62, and the two distributions generally coincide.

[0062] Therefore, by comparing the frequency spectrum of the vibration G of the secondary battery cell 62 with the frequency spectrum of the cell voltage V, it is possible to determine with high accuracy whether an internal short circuit has occurred.

[0063] For example, if the peak frequencies at which the signal strength is maximum in the frequency spectrum of the cell voltage V and the vibration G coincide in the band excluding the frequency f0 of the DC component, it can be determined that the fluctuation of the cell voltage V depends on the vibration G.

[0064] Therefore, if the peak frequency f matches in a band excluding the frequency f0 of the DC component, it can be determined that the secondary battery cell 62 is internally short-circuited.

[0065] In the example of the frequency spectrum shown in Figures 11 and 12, when the frequency spectrum of the cell voltage V of the short-circuited secondary battery cell 62 (Figure 12 (b)) is compared with the frequency spectrum of the vibration G (Figure 11) for the band excluding the frequency f0 of the DC component, both peak at "f6," and the peak frequencies are the same at "f6."

[0066] The control device 120 includes an analysis unit 125 in addition to a CPU 121 , a memory 123 , and a communication unit 127 .

[0067] The analysis unit 125 performs a fast Fourier transform (FFT) on the output signal of the voltage detection unit 110 and the output signal of the first sensor 116 to analyze the frequency spectrum of the cell voltage V of each secondary battery cell 62 and the frequency spectrum of the vibration G applied to the battery pack 60.

[0068] The control device 120 has a function of detecting an internal short circuit of the secondary battery cell 62 based on the analysis results of the frequency spectrum of the cell voltage V and the vibration G. The control device 120 is a detection device that detects an internal short circuit of the secondary battery cell 62.

[0069] An example of detecting an internal short circuit in a secondary battery cell 62 using vibrations G while the vehicle is running will be described below.

[0070] 3. Flow for determining internal short circuits using vibrations while driving 13 is a flow chart showing a determination flow of an internal short circuit using vibrations while the vehicle is running, and is made up of seven steps from step S10 to step S70. This determination flow is executed by the control device 120 periodically at a predetermined detection cycle (for example, every other day).

[0071] When the process starts, the CPU 121 determines the state of the automobile 10 (S10). Specifically, it determines whether the automobile 10 is running or parked through communication with the vehicle ECU 30. If the automobile 10 is parked (S10: NO), the automobile 10 enters a standby state.

[0072] When the automobile 10 transitions from being parked to being in motion, the vehicle ECU 30 notifies the control device 120 that "the automobile 10 is in motion."

[0073] When the CPU 121 receives the information that "the automobile 10 is running," it measures the vibration G of the battery pack 60 using the first sensor 116 (S20). While the automobile 10 is running, the vibration G caused by the rotation of the engine 20 and the rotation of the axles is continuously applied to the battery 50, causing the battery 50 to vibrate, and the vibration G is detected by the first sensor 116.

[0074] The voltage detection unit 110 constantly measures the cell voltage V of each secondary battery cell 62, regardless of the state of the automobile 10. Therefore, as shown in Fig. 14, after the start of measurement of vibration G, vibration measurement by the first sensor 116 and voltage measurement by the voltage detection unit 110 are performed in parallel, and the output signal of the first sensor 116 and the output signal of the voltage detection unit 110 are temporarily stored in the memory 123.

[0075] When a predetermined period Ts (e.g., several minutes) has elapsed since the start of measurement of vibration G, CPU 121 determines whether the fluctuation range of cell voltage V indicated by the output signal of voltage detection unit 110 is equal to or less than a predetermined threshold value (e.g., 10 mV). If the fluctuation range of cell voltage V is equal to or less than the threshold value, the output signal of first sensor 116 and the output signal of voltage detection unit 110 measured during the predetermined period Ts are output from memory 123 to analysis unit 125. On the other hand, if the fluctuation range of the voltage is greater than the threshold value, it is determined that noise has been added to the acquired cell voltage V, and the determination flow is terminated (S25).

[0076] The analysis unit 125 performs a fast Fourier transform (FFT) on the output signal of the first sensor 116 and the output signal of the voltage detection unit 110 to obtain the frequency spectrum of the vibration G of the battery pack 60 and the frequency spectrum of the cell voltage V of each secondary battery cell 62 (S30).

[0077] After completing the analysis of the frequency spectrum, the CPU 121 compares the frequency spectrum of the cell voltage V of each secondary battery cell 62 with the frequency spectrum of the vibration G (S40).

[0078] Then, the CPU 121 determines whether or not the peak frequencies match in the band excluding the frequency f0 of the DC component (S50).

[0079] If the peak frequencies of the two frequency spectra match, the CPU 121 determines that the secondary battery cell 62 has an internal short circuit, and if the peak frequencies do not match, it determines that the secondary battery cell 62 does not have an internal short circuit. The CPU 121 checks all secondary battery cells 62 for the presence or absence of an internal short circuit based on the peak frequencies.

[0080] If even one of all the secondary battery cells 62 is abnormal (internal short circuit), the CPU 121 determines that the battery pack 60 is "abnormal" (S60).

[0081] On the other hand, if all of the secondary battery cells 62 are normal (no internal short circuit), the battery pack 60 is determined to be "normal" (S70).

[0082] If it is determined to be "normal" (S70), the internal short-circuit determination flow ends. When a detection period (e.g., one day) has elapsed since the end of the determination flow, the internal short-circuit determination flow is executed again. Therefore, it is possible to periodically check whether the secondary battery cell 62 has an internal short-circuit.

[0083] If an internal short circuit occurs in any of the secondary battery cells 62, the battery pack 60 is determined to be abnormal when the internal short circuit determination flow is executed in the next cycle (S60).

[0084] If an abnormality in the battery pack 60 is detected, the CPU 121 notifies the user of the error. For example, the CPU 121 notifies the vehicle ECU 30 of the abnormality and displays a "message urging battery replacement" on the monitor of the automobile 10. By notifying the user of the error, it is possible to prompt the user to replace the battery 50 in which an internal short circuit has occurred.

[0085] 4.Effects In this configuration, the presence or absence of an internal short circuit in the secondary battery cell 62 is detected based on the vibration G and cell voltage V of the secondary battery cell 62. The vibration G and cell voltage V can be measured in a shorter time than the self-discharge amount, and the presence or absence of an internal short circuit in the secondary battery cell 62 can be detected in a shorter time.

[0086] By adding vibration G as well as cell voltage V to the factors for determining whether an internal short circuit exists, and determining whether an internal short circuit exists based on the relationship between cell voltage V and vibration G, it is possible to prevent voltage fluctuations that are not dependent on vibration G, such as changes in cell voltage V due to charging and discharging, from being mistakenly determined to be an internal short circuit.This makes it possible to detect whether an internal short circuit exists with high accuracy.

[0087] In this configuration, the frequency spectrum of the cell voltage V of the secondary battery cell 62 is compared with the frequency spectrum of the vibration G of the secondary battery cell 62 to detect whether or not an internal short circuit occurs in the secondary battery cell 62.

[0088] By comparing the frequency spectrum of the cell voltage V and the vibration G, it is possible to detect fluctuation components of the cell voltage V that fluctuate with the same period as or a similar period to the vibration G. This makes it possible to accurately determine whether fluctuations in the cell voltage V depend on the vibration G, thereby increasing the accuracy of detecting internal short circuits.

[0089] This configuration is suitable for detecting an internal short circuit (so-called soft short) in the early stage when the short-circuiting object D repeatedly becomes conductive and non-conductive due to the vibration G. Therefore, an internal short circuit in the secondary battery cell 62 can be detected at an early stage. In the lithium ion secondary battery cell 62, charging after over-discharging can cause lithium metal to precipitate, leading to an internal short circuit. By applying this configuration to the battery 50 that uses the lithium ion secondary battery cell 62 as the storage cell, an internal short circuit caused by lithium metal precipitation can be detected early.

[0090] This configuration has the advantage that it is possible to detect the presence or absence of an internal short circuit as long as the vibration G and cell voltage V applied to the secondary battery cell 62 can be measured, and that it is possible to detect the presence or absence of an internal short circuit regardless of the state of charge (SOC) or voltage characteristics (SOC-OCV characteristics) of the secondary battery cell 62.

[0091] In this configuration, the presence or absence of an internal short circuit is detected when the fluctuation range of the cell voltage V detected by the voltage detection unit 110 is equal to or less than a predetermined threshold value (e.g., 10 mV). In a secondary battery cell 62 used in an automobile 10 or the like, the cell voltage V fluctuates with charging and discharging even when an internal short circuit does not occur. The fluctuation range of the cell voltage V caused by an internal short circuit is on the order of μV to mV, whereas the fluctuation range of the voltage caused by charging and discharging is large, on the order of several tens of mV to V. If the fluctuation range of the cell voltage V is greater than the threshold value, it is determined that the fluctuation in the cell voltage V is caused by charging and discharging, not by an internal short circuit, and the determination flow ends (S25: NO).

[0092] As described above, the decision flow ends when the fluctuation range of the cell voltage V exceeds the threshold value (S25), but vibrations occur constantly while the vehicle is running, and the decision flow is executed multiple times while the vehicle is running. Therefore, even if the decision flow ends without making a final decision (matching / mismatching of peak frequencies), the next decision flow is executed immediately, and a decision result that excludes the effects of charging and discharging can be obtained.

[0093] In this configuration, the vibration G applied to the secondary battery cell 62 is measured by the first sensor 116, which is a triaxial sensor. By using the first sensor 116 as a triaxial sensor, the vibration G can be detected more reliably regardless of the direction of the vibration G applied to the secondary battery cell 62 or the orientation of the battery 50 (secondary battery cell 62) installed in the automobile 10.

[0094] <Embodiment 2> In the first embodiment, the presence or absence of an internal short circuit is detected by comparing the frequency spectrum of the vibration G of the secondary battery cell 62 with the frequency spectrum of the cell voltage V. Specifically, if the peak frequencies at which the signal strength is maximum in the frequency spectra of the vibration G and the cell voltage V match, it is determined that the secondary battery cell 62 has an internal short circuit.

[0095] In the second embodiment, the method of comparing the frequency spectrum of the vibration G with the frequency spectrum of the cell voltage V differs from that of the first embodiment, and the presence or absence of an internal short circuit is determined based on the overlap of bands with high signal strength. Specifically, as a result of comparing the two frequency spectra, if there is overlap in the bands with high signal strength (if there is at least partial overlap), it is determined that the secondary battery cell 62 has an internal short circuit, and if there is no overlap in the bands with high signal strength, it is determined that the secondary battery cell 62 does not have an internal short circuit.

[0096] The frequency spectrum of the vibration G shown in Fig. 11 has high signal strength in band H1. On the other hand, the frequency spectrum of the cell voltage V shown in Fig. 12(b) has high signal strength in band H2. If at least a portion of the two bands H1 and H2 overlap, the secondary battery cell 62 is determined to have an internal short circuit.

[0097] <Other embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings. For example, the following embodiments are also included within the technical scope of the present invention. Furthermore, various modifications other than those described below can be made without departing from the spirit of the present invention.

[0098] (1) In the above embodiment, the secondary battery cell 62 is exemplified as the power storage cell. The power storage cell is not limited to the secondary battery cell 62, but may be a capacitor. The secondary battery cell 62 is not limited to a lithium-ion secondary battery cell, but may be another non-aqueous electrolyte secondary battery cell. It may also be a lead-acid battery cell. The power storage cells are not limited to being connected in series or parallel, but may be connected in series or configured as a single cell.

[0099] (2) In the above embodiment, the battery 50 is for an automobile, but it may also be for a motorcycle. It may also be used for other moving objects such as ships, AGVs, and aircraft. If vibration G can be applied to the battery 50 from the outside, it may also be used for purposes other than moving objects, such as an uninterruptible power supply system or a power storage device for a solar power generation system.

[0100] (3) In the above embodiment, the control device 120 is provided inside the battery 50. However, the control device 120 may be provided outside the battery 50. In other words, the control device 120 provided outside the battery 50 may detect the presence or absence of an internal short circuit in the secondary battery cell 62. In this case, the control device 120 may acquire information on the cell voltage V and vibration G from the voltage detection unit 110 and the first sensor 116 provided inside the battery 50 via communication, and detect the presence or absence of an internal short circuit.

[0101] (4) In the above embodiment, the battery 50 includes the first sensor 116. However, the battery 50 does not necessarily have to include a vibration sensor. For example, a second sensor that detects vibrations applied to the body of the automobile 10 may be fixed to a location on the body other than the battery 50. An actual automobile 10 may include a sensor (second sensor) for detecting vibrations applied to the body, and this second sensor can be used. In this case, the output signal of the second sensor is received by the communication unit 127 and used in place of the detection signal of the vibration G of the battery pack 60.

[0102] The battery 50 is fixed to the body of the automobile 10, and when vibrations are applied to the body, vibrations in the same direction are simultaneously applied to the battery 50 and the secondary battery cell 62. Therefore, the vibrations detected by the second sensor can be used as a substitute for the vibrations G of the secondary battery cell 62. In this case, the sensor (first sensor 116) disposed inside the battery 50 becomes unnecessary, and the number of parts in the battery 50 can be reduced, thereby reducing the risk of failure, reducing costs, and reducing the diagnostic man-hours required for diagnosing sensor failures.

[0103] (5) The vibration G of the battery pack 60 or the vehicle body does not necessarily need to be measured in real time, and past data measured under the same conditions or data obtained through experiments may be used. For example, in the case of the same vehicle 10, it is thought that the frequency spectrum of the vibration G of the battery pack 60 or the vehicle 10 will not change significantly while the vehicle is running. Therefore, the frequency spectrum of the vibration G measured in the past may be stored in memory 123 as comparison data, and this may be compared with the frequency spectrum of the cell voltage V to detect the presence or absence of an internal short circuit.

[0104] (6) In the above embodiment, the first sensor 116 measures the vibration G acting on the battery pack 60 only for a predetermined period Ts while the vehicle is running. However, the measurement of the vibration G may be performed continuously. Regardless of whether the vehicle is running or not, if the measurement result detects the vibration G of the battery pack 60, the presence or absence of an internal short circuit may be detected based on the vibration G and cell voltage V of the secondary battery cells 62.

[0105] (7) In the above embodiment, the presence or absence of an internal short circuit in the secondary battery cell 62 is detected by comparing the frequency spectrum of the cell voltage V and the vibration G. However, it is not necessary to use the frequency spectrum as long as the presence or absence of an internal short circuit is detected based on the cell voltage V and the vibration G of the secondary battery cell 62. For example, the presence or absence of an internal short circuit may be detected based on whether the period during which the cell voltage V fluctuates (T1 in FIG. 9) and the period during which the vibration G occurs (T2 in FIG. 10) coincide with each other.

[0106] (8) In the above embodiment, the presence or absence of an internal short circuit is detected based on the cell voltage V and vibration G of the secondary battery cell 62. Alternatively, the presence or absence of an internal short circuit may be detected based on the frequency spectrum of the cell voltage V while the vehicle is running. That is, the presence or absence of an internal short circuit may be detected based only on the frequency spectrum of the cell voltage V during a period when vibration G is applied to the battery pack 60, such as while the vehicle is running, without using vibration G data. For example, the cell voltages V of the four secondary battery cells 62 are measured while the vehicle is running, and the frequency spectrum of each cell voltage V is analyzed. Then, the frequency spectra of the secondary battery cells 62 are compared. If the frequency spectrum of one secondary battery cell 62 is different from that of the other cells, for example, if it contains frequency components (e.g., f6, f7) with intensities not detected in the other cells, the secondary battery cell 62 may be determined to have an internal short circuit. The comparison target is not limited to the frequency spectra of the other cells, but may also be a past frequency spectrum of the own cell that does not have an internal short circuit.

[0107] (9) In the above embodiment, the first sensor 116 detected only the magnitude of acceleration from the vibration of the secondary battery cell 62, which includes components in all directions. Alternatively, the vibration sensor may detect the presence or absence of an internal short circuit based on acceleration in multiple directions, for example, the X, Y, and Z directions, and the cell voltage V. For example, if the cell voltage V fluctuates only during a period in which acceleration in the stacking direction of the electrode plates inside the secondary battery cell 62 (the Y direction in FIG. 5) is detected, it is possible to determine with higher accuracy that an internal short circuit has occurred in the secondary battery cell 62.

[0108] (10) In the above embodiment, the analysis of the frequency spectrum of the vibration G and the cell voltage V is performed by the analysis unit 125, but it may also be performed by the CPU 121.

[0109] (11) In the above embodiment, the vibration G generated while the vehicle is running is used to detect an internal short circuit in the secondary battery cell 62. The vibration applied to the secondary battery cell 62 is not limited to the vibration caused by the vehicle running. Vibration may be applied to the battery 50 by any method, such as a vibration generator.

[0110] (12) In the above embodiment, a three-axis sensor is used as the first sensor 116. However, a single-axis, two-axis, or other multi-axis sensor may be used as the first sensor 116 and the second sensor.

[0111] (13) In the above embodiment, the presence or absence of an internal short circuit is determined (S30 to S70) when the fluctuation range of the cell voltage V is equal to or less than the threshold value (S25: YES). However, the determination based on the threshold value is an additional process, and the presence or absence of an internal short circuit may be determined without taking the fluctuation range of the cell voltage V into consideration. [Explanation of symbols]

[0112] 10: Car (an example of a "mobile object") 50: Battery (an example of an "electricity storage device") 60: Battery pack 62: Secondary battery cell (an example of a "storage cell") 100: Management device (an example of a "control unit") 110: Voltage detection unit 116: First sensor 120: Processing section 121: CPU 123: Memory 127: Communications Department

Claims

1. A detection device for detecting an internal short circuit in a storage cell, The detection device detects the presence or absence of an internal short circuit in the storage cell by comparing a frequency spectrum of the vibration of the storage cell with a frequency spectrum of a cell voltage of the storage cell.

2. 2. The detection device according to claim 1, The detection device determines that the storage cell has an internal short circuit when a peak frequency at which the signal strength excluding a DC component is maximum in each frequency spectrum of the vibration of the storage cell and the cell voltage coincides.

3. A detection device for detecting an internal short circuit in a storage cell, The power storage device including the detection device has a plurality of the power storage cells, A detection device that detects the presence or absence of an internal short circuit in the storage cell by comparing frequency spectra of cell voltages of the storage cells while the storage device is vibrating.

4. A detection device as claimed in claim 3, The detection device determines that one of the storage cells has an internal short circuit when a frequency spectrum of the one of the storage cells is different from a frequency spectrum of the other of the storage cells.

5. The detection device according to any one of claims 1 to 4, A detection device that detects the presence or absence of an internal short circuit in the storage cell when a fluctuation range of the cell voltage is equal to or less than a threshold value.

6. A storage cell; A voltage detection unit that detects a voltage of the storage cell; A power storage device comprising: the detection device according to any one of claims 1 to 5.

7. A method for detecting an internal short circuit in a storage cell, comprising: A method for detecting an internal short circuit, comprising: detecting the presence or absence of an internal short circuit in the storage cell by comparing a frequency spectrum of the vibration of the storage cell with a frequency spectrum of a cell voltage of the storage cell.

8. A method for detecting an internal short circuit in a storage cell, comprising: A method for detecting an internal short circuit, comprising: detecting the presence or absence of an internal short circuit in the storage cell by comparing frequency spectra of cell voltages of the storage cells while the storage cells are vibrating.

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