Methods for detecting abnormalities in storage batteries
Calculating deformation thresholds in storage batteries addresses peeling and short circuit risks in heat conductive materials, eliminating the need for physical sensors and reducing device size and cost.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2025-01-15
- Publication Date
- 2026-07-28
AI Technical Summary
Deformation of the bottom surface of a storage battery case due to cell expansion can lead to peeling of the heat conductive material and potential short circuits, increasing device size and cost when detected using physical sensors.
Calculate initial and deformation amounts of the case bottom surface and stacking direction based on manufacturing and usage data to determine when thresholds are exceeded, outputting alerts for peeling and short circuit risks without physical sensors.
Accurately detects abnormalities without the need for physical sensors, reducing device size and cost by using data-driven methods to monitor deformation-related issues.
Smart Images
Figure 2026122283000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a method for detecting an abnormality in a storage battery, particularly in a storage battery in which a laminate of a plurality of rectangular cells is adhered to a base plate by a heat conductive material.
Background Art
[0002] Patent Document 1 discloses a technique for detecting a change in internal pressure or electrode swelling of a sealed secondary battery by a monitoring sensor.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In a storage battery in which a laminate of a plurality of rectangular cells is adhered to a base plate by a heat conductive material, one of the abnormalities to be detected is deformation of the bottom surface of the case due to expansion of the cells. Deformation of the case bottom surface may cause peeling of the heat conductive material from the case bottom surface. And when the deformation further progresses, there is also a risk of causing a short circuit due to contact between the case and the internal electrode body. As a method for detecting such an abnormality, a method using a monitoring sensor as in the above prior art can be considered. However, the method using a monitoring sensor for detecting deformation of the case bottom surface causes an increase in the size and cost of the power storage device.
Means for Solving the Problems
[0005] A method according to one embodiment of the present disclosure is a method for detecting an abnormality in a storage battery comprising a laminate of a plurality of prismatic cells bonded to a base plate with a thermal conductive material, and includes: calculating the initial constraint deformation amount of a prismatic cell of interest in the laminate based on process data acquired in the manufacturing process; calculating the deformation amount of the bottom surface of the case of the prismatic cell of interest based on the initial constraint deformation amount and usage history data; and outputting a first alert when the deformation amount exceeds a predetermined first threshold. [Effects of the Invention]
[0006] According to this disclosure, the amount of deformation of the bottom surface of the rectangular cell case can be determined by calculations based on data, so there is no need to provide a sensor that physically detects deformation in order to detect abnormalities caused by deformation of the bottom surface of the rectangular cell case. [Brief explanation of the drawing]
[0007] [Figure 1] This diagram illustrates the configuration of a battery comprising a stack of multiple prismatic cells and explains abnormalities caused by deformation of the prismatic cells. [Figure 2] This figure shows an example of how the amount of deformation of the bottom surface of a rectangular cell case changes due to repeated charging and discharging. [Figure 3] This flowchart shows a method for detecting abnormalities caused by deformation of the bottom surface of a rectangular cell case. [Figure 4] This figure shows an example of how the amount of deformation in the stacking direction of a prismatic cell changes due to repeated charging and discharging. [Figure 5] This flowchart shows a method for detecting abnormalities caused by deformation in the stacking direction of rectangular cells. [Modes for carrying out the invention]
[0008] 1. Overview of Battery Malfunctions Figure 1 illustrates the configuration of a battery comprising a stack of multiple prismatic cells and the abnormalities caused by deformation of the prismatic cells. As an example of a battery used in battery electric vehicles (BEVs), a battery pack is known in which multiple prismatic cells are stacked to form modules, and multiple modules are packed together.
[0009] As shown in Figure 1A, in modularization, a stack of multiple rectangular cells 10 is fitted between end plates 40 in a constrained and compressed state in the stacking direction. The stack of multiple rectangular cells 10 is then bonded to a base plate 30 with a thermal conductive material 20, more specifically, a thermally conductive adhesive. The base plate 30 may also have a cooling function.
[0010] Even after being fitted between the end plates 40, the restraining load remains, and each rectangular cell 10 deforms due to the restraining load. Here, the restraining load remaining on the rectangular cell 10 at the time of shipment of the battery pack, that is, the restraining load in the initial state, is called the initial restraining load. The deformation due to the initial restraining load includes deformation in the height direction of the rectangular cell 10. Figure 1B shows the cross-sectional shape of the rectangular cell 10 in the initial state. In the initial state, the bottom surface 10b of the case of the rectangular cell 10 is deformed downwards and convex due to the initial restraining load.
[0011] The prismatic cell 10 gradually expands in the stacking direction due to charging and discharging. For example, as shown in Figure 1C, the expansion of the prismatic cell 10 begins from the first charge, and as the prismatic cell 10 expands in the stacking direction, the bottom surface 10b of the case deforms upward into a concave shape. Then, as shown in Figure 1D, as degradation progresses with repeated charging and discharging, the expansion of the prismatic cell 10 in the stacking direction during charging increases, and consequently, the amount of deformation in the upward concave direction, i.e., inward direction, of the bottom surface 10b of the case increases. As the bottom surface 10b deforms upward into a concave shape, tensile stress acts between the bottom surface 10b of the case and the thermal conductive material 20.
[0012] The tensile stress acting between the case bottom surface 10b and the thermal conductive material 20 can cause the thermal conductive material 20 to peel off from the case bottom surface 10b. If the deformation of the case bottom surface 10b progresses further, a short circuit may occur due to contact between the case and the internal electrode body. In other words, the deformation of the case bottom surface 10b caused by repeated charging and discharging may lead to the abnormality of the thermal conductive material 20 peeling off from the case bottom surface 10b, and furthermore, it may lead to the abnormality of a short circuit due to contact between the case and the internal electrode body.
[0013] Furthermore, the deformation due to the initial restraining load includes deformation of the rectangular cells 10 in the stacking direction. The amount of deformation of the rectangular cells 10 in the stacking direction increases as the rectangular cells 10 expand due to repeated charging and discharging. Due to this expansion, as shown by the white arrow lines in Figure 1E, the stacked rectangular cells 10 are pushed sequentially from the center toward the end plate 40. Since the bottom surface 10b of the case is bonded to the base plate 30 by the thermal conductive material 20, a shear stress acts between the bottom surface 10b of the case and the thermal conductive material 20, as shown by the black arrow lines.
[0014] Shear stress acting between the case bottom surface 10b and the thermal conductive material 20 can cause the thermal conductive material 20 to peel off from the case bottom surface 10b. In other words, deformation in the stacking direction of the rectangular cell 10 caused by repeated charging and discharging may lead to the abnormality of the thermal conductive material 20 peeling off from the case bottom surface 10b.
[0015] 2. Method for detecting abnormalities caused by deformation of the bottom surface of a rectangular cell case. The deformation of the case bottom surface 10b of the rectangular cell 10 increases with repeated charging and discharging. Figure 2 shows an example of the change in the amount of deformation of the case bottom surface 10b due to repeated charging and discharging. As shown in Figure 2, the amount of deformation S of the case bottom surface increases and decreases repeatedly as charging and discharging are repeated, but overall it gradually increases. When the amount of deformation S of the case bottom surface exceeds a predetermined first threshold Th1, peeling due to tensile stress of the thermal conductive material 20 may occur. Furthermore, when the amount of deformation of the case bottom surface exceeds a predetermined second threshold Th2 which is greater than the first threshold Th1, a short circuit may occur due to contact between the case and the internal electrode body. Hereinafter, the first threshold Th1 will be called the thermal conductive material tensile peeling threshold, and the second threshold Th2 will be called the case short circuit threshold. The specific values of the thermal conductive material tensile peeling threshold and the case short circuit threshold are determined by the specifications of the storage battery and can be identified, for example, by testing or simulation.
[0016] Figure 3 shows a flowchart of a method for detecting abnormalities caused by deformation of the case bottom surface 10b of the rectangular cell 10. A key feature of this method is that, rather than physically detecting the deformation of the case bottom surface 10b with a sensor, the amount of deformation is calculated. This method can be executed by computer.
[0017] The calculation of the case bottom deformation is performed for the prismatic cell of interest among the multiple prismatic cells 10 that make up the battery pack. In this embodiment, the prismatic cell of interest is the thinnest prismatic cell in the battery pack. The thinnest prismatic cell is the prismatic cell in which the deformation of the case bottom 10b is greatest when expansion occurs in the stacking direction, that is, the prismatic cell in which tensile peeling or short circuits of the thermal conductive material 20 are most likely to occur. However, the prismatic cell of interest may be determined arbitrarily. The prismatic cell of interest may be one prismatic cell, multiple prismatic cells, or all prismatic cells.
[0018] In the flowchart shown in FIG. 3, the processes of steps S11 to S14 are preparation processes that are performed only once, for example, before shipping the battery pack or before shipping the BEV equipped with the battery pack. In step S11, the traceability data of the battery pack to be subject to abnormality detection is acquired. The traceability data includes the process data acquired in the manufacturing process of the battery pack. In step S12, the thinnest rectangular cell is specified based on the traceability data, and the thickness of the thinnest rectangular cell is calculated. In step S13, the initial restraint load of the thinnest rectangular cell is calculated based on the thickness of the thinnest rectangular cell and the traceability data. Then, in step S14, the initial restraint deformation amount of the thinnest rectangular cell, specifically, the initial value of the case bottom surface deformation amount is calculated based on the thickness of the thinnest rectangular cell and the initial restraint load. The initial value of the case bottom surface deformation amount calculated in step S14 is stored in the memory of the computer.
[0019] In the flowchart shown in FIG. 3, the processes of steps S101 to S108 are processes that are repeatedly performed every time the BEV equipped with the battery pack is driven after shipping the BEV. In step S101, it is determined whether the ignition (IG) is turned on. While the IG is off, the subsequent processes are skipped, and when the IG is turned on, the processes after step S102 are executed.
[0020] In step S102, the estimated expansion amount of the thinnest rectangular cell is acquired. There is no limitation on the method for estimating the expansion amount. Assuming that the expansion amounts of all rectangular cells are substantially equal, the average estimated expansion amount of the rectangular cells in the entire battery pack may be used as the estimated expansion amount of the thinnest rectangular cell. For estimating the expansion amount, for example, a known method such as the method described in Japanese Patent Laid-Open No. 2023-11289 can be used.
[0021] In step S103, the estimated internal pressure of the thinnest rectangular cell is obtained. There is no limitation on the method for estimating the internal pressure. Assuming that the internal pressures of all rectangular cells are approximately equal, the estimated internal pressure of the average rectangular cell in the entire battery pack may be used as the estimated internal pressure of the thinnest rectangular cell. For the estimation of the internal pressure, for example, a known method such as the method described in Japanese Patent Application Laid-Open No. 2019-118216 can be used. Note that the processing of step S103 may be interchanged with the processing of step S102, or they may be executed simultaneously.
[0022] In step S104, based on the initial value of the case bottom surface deformation amount calculated in step S14 and stored in the memory, the estimated expansion amount obtained in step S102, and the estimated internal pressure obtained in step S103, the case bottom surface deformation amount of the thinnest rectangular cell is calculated. The estimated expansion amount and the estimated internal pressure are used for calculating the change amount from the initial value of the case bottom surface deformation amount. The relationship between the case bottom surface deformation amount, the expansion amount, and the internal pressure is defined by a physical model or a map.
[0023] In step S105, the case bottom surface deformation amount S obtained in step S104 is compared with the thermal conductive material tensile peeling threshold Th1, and it is determined whether the case bottom surface deformation amount S has increased to the extent that tensile peeling of the thermal conductive material 20 occurs. If the case bottom surface deformation amount S is less than or equal to the thermal conductive material tensile peeling threshold Th1, the subsequent processing is skipped. When the case bottom surface deformation amount S exceeds the thermal conductive material tensile peeling threshold Th1, in step S106, diagnostic code 1 is output. Diagnostic code 1 is an alert that notifies the risk of tensile peeling of the thermal conductive material 20.
[0024] If diagnostic code 1 is output, the determination in step S107 is performed. In step S107, the case bottom deformation amount S obtained in step S104 is compared with the case short-circuit threshold Th2 to determine whether the case bottom deformation amount S has increased to the point where a short circuit may occur. If the case bottom deformation amount S is less than or equal to the case short-circuit threshold Th2, the subsequent processing is skipped. If the case bottom deformation amount S exceeds the case short-circuit threshold Th2, diagnostic code 2 is output in step S108. Diagnostic code 2 is an alert indicating the risk of a short circuit. The alert corresponding to diagnostic code 1 is called the first alert, and the alert corresponding to diagnostic code 2 is called the second alert.
[0025] 3. Method for detecting abnormalities caused by deformation in the stacking direction of rectangular cells The deformation of the prismatic cells 10 in the stacking direction increases with repeated charging and discharging. Figure 4 shows an example of the change in the amount of deformation in the stacking direction due to repeated charging and discharging. As shown in Figure 4, the amount of deformation SS in the stacking direction increases and decreases repeatedly as charging and discharging are repeated, but overall it gradually increases. When the amount of deformation SS in the stacking direction exceeds a predetermined third threshold Th3, delamination due to shear stress in the thermal conductive material 20 may occur. Hereinafter, the third threshold Th3 will be referred to as the thermal conductive material shear delamination threshold. The specific value of the thermal conductive material shear delamination threshold is determined by the specifications of the storage battery and can be identified, for example, by testing or simulation.
[0026] Figure 5 shows a flowchart of a method for detecting abnormalities caused by deformation in the stacking direction of the rectangular cell 10. A key feature of this method is that, rather than physically detecting the deformation in the stacking direction of the rectangular cell 10 with a sensor, the amount of deformation in the stacking direction is calculated. This method can be executed by computer.
[0027] The calculation of deformation in the stacking direction is performed for a particular prismatic cell among the multiple prismatic cells 10 that make up the battery pack. In this embodiment, the prismatic cell of interest is the prismatic cell closest to the end plate 40 in the module, i.e., the outermost prismatic cell. The outermost prismatic cell is the prismatic cell in which the shear stress is greatest when expansion occurs in the stacking direction, i.e., the prismatic cell in which shear delamination of the thermal conductive material 20 is most likely to occur. However, the prismatic cell of interest may be determined arbitrarily. The prismatic cell of interest may be one prismatic cell, multiple prismatic cells, or all prismatic cells.
[0028] In the flowchart shown in Figure 5, steps S21 to S24 are preparatory processes performed only once, for example, before the shipment of a battery pack or before the shipment of a BEV equipped with a battery pack. In step S21, traceability data of the battery pack subject to anomaly detection is acquired. The traceability data includes process data acquired during the manufacturing process of the battery pack. In step S22, the thickness of each rectangular cell and the thickness of the insulation material between the rectangular cells are calculated based on the traceability data. In step S23, the initial constraint load of the battery pack is calculated based on the traceability data. Then, in step S24, the initial constraint deformation amount of the outermost rectangular cell, specifically the initial value of the stacking direction deformation amount, is calculated based on the thickness of each rectangular cell and insulation material and the initial constraint load. The initial value of the stacking direction deformation amount calculated in step S24 is stored in the computer's memory.
[0029] In the flowchart shown in Figure 5, steps S201 to S205 are processes that are repeated each time a BEV is operated after the BEV equipped with a battery pack has been shipped. In step S201, it is determined whether the ignition (IG) is turned on. While the IG is off, the subsequent processes are skipped, and once the IG is turned on, the processes from step S202 onwards are executed.
[0030] In step S202, the estimated expansion amount of the outermost rectangular cell is obtained. There are no limitations on the method of estimating the expansion amount. It is also possible to assume that the expansion amounts of all rectangular cells are approximately equal and use the average estimated expansion amount of the rectangular cells for the entire battery pack as the estimated expansion amount of the outermost rectangular cell.
[0031] In step S203, the stacking direction deformation amount of the outermost corner cell is calculated based on the initial value of the stacking direction deformation amount calculated in step S24 and stored in memory, and the estimated expansion amount obtained in step S202. The estimated expansion amount is used to calculate the change from the initial value of the stacking direction deformation amount. The relationship between the stacking direction deformation amount and the expansion amount is defined by a physical model or map.
[0032] In step S204, the stacking direction deformation amount SS obtained in step S203 is compared with the thermal conductive material shear delamination threshold Th3 to determine whether the stacking direction deformation amount SS has increased to the extent that shear delamination of the thermal conductive material 20 may occur. If the stacking direction deformation amount SS is less than or equal to the thermal conductive material shear delamination threshold Th3, the subsequent processing is skipped. If the stacking direction deformation amount SS exceeds the thermal conductive material shear delamination threshold Th3, diagnostic code 3 is output in step S205. Diagnostic code 3 is an alert indicating the risk of shear delamination of the thermal conductive material 20. The alert corresponding to diagnostic code 3 is called the third alert.
[0033] 4. Effects According to the method for detecting abnormalities due to deformation of the case bottom surface of a rectangular cell according to this embodiment, the amount of deformation of the case bottom surface can be determined by calculation based on data, so there is no need to provide a sensor that physically detects deformation in order to detect abnormalities due to deformation of the case bottom surface 10b of the rectangular cell 10. Furthermore, according to the method for detecting abnormalities due to deformation in the stacking direction of a rectangular cell according to this embodiment, the amount of deformation in the stacking direction can be determined by calculation based on data, so there is no need to provide a sensor that physically detects deformation in order to detect abnormalities due to deformation in the stacking direction of the rectangular cell 10. By having a computer execute each of the above methods, the user can be notified by a first alert of the risk of tensile peeling of the thermal conductive material 20, by a second alert of the risk of short circuit, and by a third alert of the risk of shear peeling of the thermal conductive material 20.
[0034] The method for detecting abnormalities due to deformation of the bottom surface of the case of the rectangular cell according to this embodiment and the method for detecting abnormalities due to deformation in the stacking direction of the rectangular cell according to this embodiment can be used in combination as described above, or only one of them can be used. However, by using two methods with different logics in combination, the accuracy of detecting peeling of the thermal conductive material 20 can be improved. [Explanation of Symbols]
[0035] 10 Rectangular cell, 10b Case bottom, 20 Thermal conductive material, 30 Base plate, 40 End plate
Claims
1. A method for detecting an abnormality in a storage battery comprising a stack of multiple prismatic cells bonded to a base plate by a thermal conductive material, Based on process data obtained during the manufacturing process, the initial constraint deformation amount of a particular rectangular cell in the laminate is calculated, Based on the initial constraint deformation amount and usage history data, the deformation amount of the bottom surface of the case of the rectangular cell of interest is calculated, This includes outputting a first alert when the amount of deformation exceeds a predetermined first threshold. A method for detecting abnormalities in a storage battery, characterized by the following:
2. In the method for detecting an abnormality in a storage battery according to claim 1, Calculating the deformation amount based on the initial constraint deformation amount and the usage history data includes using the initial constraint deformation amount as the initial value of the deformation amount, and calculating the change from the initial value based on the expansion amount and internal pressure of the rectangular cell of interest estimated based on the usage history data. A method for detecting abnormalities in a storage battery, characterized by the following:
3. In the method for detecting an abnormality in a storage battery according to claim 1, The aforementioned rectangular cell of interest is the thinnest rectangular cell in the laminate. A method for detecting abnormalities in a storage battery, characterized by the following:
4. In the method for detecting an abnormality in a storage battery according to claim 1, The first threshold is set to a value at which tensile peeling of the thermal conductive material from the bottom surface can occur. A method for detecting abnormalities in a storage battery, characterized by the following:
5. A method for detecting an abnormality in a storage battery according to any one of claims 1 to 5, The system further includes outputting a second alert when the amount of deformation exceeds a predetermined second threshold that is greater than the first threshold. A method for detecting abnormalities in a storage battery, characterized by the following:
6. In the method for detecting an abnormality in a storage battery according to claim 5, The second threshold value is set to a value at which a short circuit may occur due to contact between the case and the internal electrode body. A method for detecting abnormalities in a storage battery, characterized by the following: