Battery cell leakage detection FFC line, monitoring system, battery pack and detection method
By setting a windowed area on the FFC line to fit the cell surface and using the electrolyte to change the electrical signal state, the problem of complex structure, high cost and real-time monitoring of existing cell leakage detection is solved. This achieves cell-level leakage detection and location, improving the safety and reliability of the battery pack.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JINGSHI ELECTRONICS TECH CO LTD SUZHOU
- Filing Date
- 2026-03-20
- Publication Date
- 2026-05-29
AI Technical Summary
Existing cell leakage detection methods suffer from problems such as complex structure, high cost, low integration, and inability to achieve real-time monitoring. In particular, they cannot independently monitor each cell and accurately locate the leakage position.
An open area is set on the FFC line to expose the internal conductor, allowing it to adhere to the cell surface. The electrolyte contacts the conductor, changing the electrical signal state. The battery management system monitors the changes in the electrical signal to determine leakage, achieving real-time detection at the cell level.
It achieves a simple, low-cost, and real-time cell leakage detection system, which can accurately locate the leaking cell, improve the safety and reliability of the battery pack, and avoid safety accidents.
Smart Images
Figure CN122108471A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery safety monitoring technology, specifically relating to a cell leakage detection FFC line, a monitoring system including the FFC line, a battery pack including the monitoring system, and a cell leakage detection method based on the system. Background Technology
[0002] With the rapid development of new energy vehicles and energy storage equipment, the energy density of battery packs is constantly increasing, and the requirements for their safety are becoming increasingly stringent. As the core component of the battery pack, the safety of the battery cell is directly related to the safe operation of the entire battery pack and even the application equipment.
[0003] Electrolyte leakage is a common safety hazard during battery pack use. Cells may leak electrolyte during prolonged use or after being subjected to external impact. Electrolyte is corrosive and conductive; once leaked, it can not only corrode the internal structure of the battery pack but also potentially cause short circuits, thermal runaway, or even fire and explosion. Therefore, timely and accurate detection of cell leakage is crucial for ensuring battery pack safety.
[0004] In existing technologies, cell leakage detection typically employs the following methods: one is to install independent liquid level or humidity sensors within the battery pack to detect the presence of electrolyte and determine if leakage has occurred; the other is to conduct regular manual inspections. However, these methods have significant drawbacks: independent sensors are costly and require additional installation space and wiring, increasing the structural complexity and manufacturing cost of the battery pack; manual inspections cannot achieve real-time monitoring and are difficult to detect potential leakage problems in a timely manner. Furthermore, existing detection methods cannot achieve independent monitoring of each cell, making it impossible to accurately locate the cell where leakage has occurred.
[0005] Flexible flat cables (FFCs) are widely used for information transmission within battery packs due to their advantages such as thinness, flexibility, and ease of wiring. However, existing FFCs are only used as signal transmission media and do not possess cell status sensing capabilities. How to endow FFCs with cell leakage sensing capabilities, enabling them to maintain their original signal transmission function while also incorporating leakage detection, has become a pressing technical problem to be solved in this field.
[0006] In view of this, developing a leakage detection scheme that is simple in structure, low in cost, can respond in real time, and can achieve cell-level monitoring has become a research direction for those skilled in the art. Summary of the Invention
[0007] The present invention aims to solve at least one technical problem existing in the prior art. Specifically, one objective of the present invention is to provide a cell leakage detection FFC line, which, while maintaining the original signal transmission function, can detect cell leakage and trigger an abnormal signal, thereby solving the technical problems of existing leakage detection solutions being complex in structure, high in cost, and low in integration.
[0008] Another object of the present invention is to provide a battery pack cell monitoring system including the above-mentioned FFC line.
[0009] Another object of the present invention is to provide a battery pack comprising the above-described monitoring system.
[0010] Another object of the present invention is to provide a cell leakage detection method based on the above system.
[0011] Technical solution To achieve the above objectives, the first aspect of the present invention provides a cell leakage detection FFC line, including an FFC body, wherein the FFC body is provided with at least one window area, the window area exposing an internal conductor, and the window area is used to be attached to the surface of the battery pack cell.
[0012] The exposed internal conductors in the windowed area are in a connected state for transmitting normal electrical signals.
[0013] One end of the FFC body is provided with a first connection terminal, and the other end is provided with a second connection terminal. The first connection terminal is used to connect with the battery management system to transmit the electrical signal. The adjacent second connection terminals are shorted by electronic wires to form a signal loop.
[0014] When the battery cell leaks electrolyte, the electrolyte comes into contact with the exposed conductor in the windowed area, changing the electrical signal state at the windowed area and triggering an abnormal signal.
[0015] Furthermore, the first connection terminal has an open copper structure for insertion with a connector, enabling a detachable electrical connection with the battery management system.
[0016] Furthermore, the windowed area has a punched window structure, exposing the internal conductor to the surface of the FFC body for direct contact with potential leakage areas of the battery cell.
[0017] Furthermore, the internal conductor is a metal foil conductor, preferably a copper foil conductor, used to cause a change in the electrical signal state when in contact with the electrolyte.
[0018] A second aspect of the present invention provides a battery pack cell leakage monitoring system, comprising: At least one cell leakage detection FFC line according to any one of the first aspects of the present invention, wherein the window area of the FFC line is attached to the surface of the cell. The battery management system is electrically connected to the first connection terminal of the FFC line and is used to monitor the electrical signal status of the FFC line and determine whether the corresponding cell has leaked based on the changes in the electrical signal status.
[0019] Furthermore, the FFC line is connected to the battery management system via a connector, and the end of the FFC line is provided with a connection terminal for insertion into the connector.
[0020] A third aspect of the present invention provides a battery pack, comprising: Multiple battery cells; The cell leakage detection FFC line according to any one of the first aspects of the present invention, wherein the window area of the FFC line is attached to the surface of the cell; The battery management system is electrically connected to the first connection terminal of the FFC line and is used to monitor the electrical signal status of the FFC line and determine the location of the cell where leakage has occurred based on the changes in the electrical signal status.
[0021] Furthermore, the FFC line is connected to the battery management system via a connector, and the end of the FFC line is provided with a connection terminal.
[0022] Furthermore, there are multiple FFC lines, each FFC line being disposed on the surface of one or more battery cells to achieve cell-level leakage monitoring.
[0023] A fourth aspect of the present invention provides a method for detecting cell leakage, applied to a battery pack cell monitoring system. The system includes an FFC line attached to the surface of the cell and a battery management system electrically connected to the FFC line. The FFC line has a windowed area exposing an internal conductor, which is in a connected state. One end of the FFC line has a first connection terminal connected to the battery management system, and the other end has a second connection terminal short-circuited by an electronic wire to form a signal loop. The method includes the following steps: The FFC line transmits normal electrical signals to the battery management system through the internal conductors exposed in its windowed area. When leakage occurs in the battery cell, the electrolyte comes into contact with the exposed conductor in the windowed area, changing the electrical signal state at the windowed area. The battery management system monitors the electrical signal status of the FFC line; When a change in the electrical signal status is detected, the battery management system determines that the corresponding cell has leaked.
[0024] Furthermore, the change in the electrical signal state includes one or more of the following: signal attenuation, signal interference, impedance change, or short circuit.
[0025] Furthermore, the method also includes the following step: the battery management system determines the location of the cell where leakage has occurred based on the FFC line where the electrical signal state changes.
[0026] The fifth aspect of this invention provides a method for manufacturing an FFC wire for detecting battery cell leakage, comprising the following steps: An FFC substrate is provided, the FFC substrate including an insulating layer and an internal conductor, the internal conductor being in a connected state; At least one window area is formed on the FFC substrate corresponding to the potential leakage area of the cell to expose the internal conductor, and the window area is configured to be attached to the surface of the cell. A first connection terminal is formed at one end of the FFC substrate, and a second connection terminal is formed at the other end. Adjacent second connection terminals are shorted by electronic wires to form a signal circuit. The FFC substrate is cut to a size suitable for bonding to the surface of the battery cell.
[0027] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: First, it has a simple structure and high integration. This invention integrates the leakage detection function directly into the FFC line itself, eliminating the need for additional independent sensor components, simplifying the internal structure of the battery pack, and saving installation space.
[0028] Secondly, it is low-cost. Utilizing the existing structure and manufacturing process of the FFC line, leakage detection can be achieved simply by opening a window, without the need for complex manufacturing processes or expensive materials, thus significantly reducing manufacturing costs.
[0029] Third, it has a fast response speed. When leakage occurs in the battery cell, the electrolyte directly contacts the exposed conductor, immediately changing the electrical signal state at the open area, achieving a real-time response and enabling timely detection of potential leakage.
[0030] Fourth, high detection reliability. The window area is directly attached to the surface of the battery cell, ensuring that the exposed conductor can be contacted immediately if the electrolyte leaks, avoiding detection delays or failures caused by distance or obstruction.
[0031] Fifth, it enables cell-level monitoring. Each FFC line can be installed on the surface of one or more cells. Combined with the signal processing of the battery management system, it can accurately locate the cell where leakage has occurred, facilitating subsequent maintenance and handling.
[0032] Sixth, it does not affect the original signal transmission function. The conductors exposed in the windowed area are in a connected state and can transmit electrical signals normally. The leakage detection function is an additional function based on the original signal transmission function, realizing functional integration.
[0033] Seventh, the detection method is simple and reliable. Leakage can be determined by monitoring changes in the electrical signal state of the FFC line, without the need for complex algorithms or additional detection equipment.
[0034] Eighth, improve the overall safety of the battery pack. By monitoring cell leakage in real time and providing timely warnings, safety accidents such as short circuits and thermal runaway caused by leakage can be effectively avoided, significantly improving the safety of the battery pack. Attached Figure Description
[0036] Figure 1 This is a schematic diagram of the structure of the cell leakage detection FFC line provided in an embodiment of the present invention.
[0037] Figure 2 This is a schematic diagram of the connection between the battery pack cells and the FFC line provided in an embodiment of the present invention.
[0038] Explanation of main component symbols 1-FFC body; 2-Windowed area; 3-Internal conductor; 4-First connecting terminal; 5-Battery cell; 6-Second connecting terminal; 7-Connector.
[0039] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation
[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute any limitation on the scope of protection of this invention. Example 1: FFC line for detecting cell leakage like Figure 1 As shown, this embodiment provides a cell leakage detection FFC cable, including an FFC body 1. The FFC body 1 is a flexible flat cable, including an insulation layer and an inner conductor 3. The inner conductor 3 is preferably a copper foil conductor, which has good conductivity. The insulation layer of the FFC body 1 is usually made of insulating materials such as polyester or polyimide, which is used to protect the inner conductor 3 and provide electrical insulation.
[0042] The FFC body 1 has at least one window area 2. The window area 2 is a punched window structure, formed by removing the insulation layer at the corresponding position, exposing the internal conductor 3 to the surface of the FFC body 1. The window area 2 is used to fit against the surface of the battery pack cell 5 and corresponds to the potential leakage area of the cell 5. The potential leakage area can be the explosion-proof valve area, the tab area, or other parts of the cell that are prone to leakage.
[0043] In this embodiment, the exposed internal conductor 3 in the windowed area 2 is in a connected state, meaning that the internal conductor 3 in the windowed area 2 is part of the normal signal transmission path of the FFC line and is used to transmit normal electrical signals. This means that the windowed area 2 does not cut off the conductor, but maintains the continuity of the conductor, allowing electrical signals to pass through the area normally.
[0044] One end of the FFC body 1 is provided with a first connection terminal 4, and the other end is provided with a second connection terminal 6. The first connection terminal 4 is used to connect with the battery management system to transmit electrical signals. Adjacent second connection terminals 6 are shorted by electronic wires to form a complete signal transmission loop. In this embodiment, the first connection terminal 4 has an exposed copper structure, that is, it is formed by removing the end insulation layer to expose the internal conductor 3, and is used to plug into the connector 7 to achieve a detachable electrical connection with the battery management system. The first connection terminal 4 can also take other forms, such as soldered terminals, pins, etc., as long as it can achieve an electrical connection with the battery management system.
[0045] The working principle of this embodiment is as follows: The windowed area 2 of the FFC line is attached to the surface of the cell 5. Under normal circumstances, the exposed internal conductor 3 of the windowed area 2 is in a connected state. As part of the FFC line, it transmits electrical signals normally through the circuit formed by the first connecting terminal 4, the electronic wire, and the second connecting terminal 6. The battery management system receives the normal electrical signals.
[0046] When cell 5 leaks electrolyte, the electrolyte leaks onto the surface of cell 5 and directly contacts the exposed internal conductor 3 in the window area 2. Because the electrolyte is conductive, its contact with the exposed conductor 3 alters the electrical signal state at the window area 2. Specifically, the contact of the electrolyte may cause various changes in the electrical signal state, including but not limited to: signal attenuation (the electrolyte absorbs or scatters some signal energy), signal interference (the electrolyte introduces additional capacitance or inductance effects), impedance changes (the electrolyte changes the dielectric constant between conductors or forms a parallel path), or short circuits (the electrolyte connects adjacent conductors to form a low-resistance path). These changes in the electrical signal state are transmitted through the FFC body 1 to the first connection terminal 4, and then through the connector 7 to the battery management system. By monitoring the changes in the electrical signal state, the battery management system can determine that the corresponding cell 5 has leaked electrolyte.
[0047] Example 2: Battery Pack Cell Leakage Monitoring System like Figure 1-2 As shown, this embodiment provides a battery pack cell leakage monitoring system, including the cell leakage detection FFC line and battery management system described in Embodiment 1.
[0048] The FFC wire's windowed area 2 is bonded to the surface of the battery cell 5. Specifically, the FFC wire is bonded to the surface of the battery cell 5 by adhesive or other fixing methods, ensuring that the windowed area 2 is in close contact with the surface of the battery cell 5. The bonding method can use double-sided tape, thermally conductive adhesive, structural adhesive, etc., to ensure both a firm bond and that the electrolyte can smoothly contact the windowed area 2 in the event of leakage from the battery cell.
[0049] The FFC line is connected to the battery management system via connector 7. The first terminal 4 at the end of the FFC line is inserted into connector 7, and connector 7 is connected to the battery management system via a wire. The battery management system monitors the electrical signal status of the FFC line and determines whether the corresponding cell 5 has leaked based on changes in the electrical signal status.
[0050] In this embodiment, the battery management system can connect to multiple FFC lines simultaneously, with each FFC line corresponding to one or more battery cells 5. Under normal circumstances, the battery management system receives normal electrical signals transmitted from each FFC line. When the electrical signal state of a certain FFC line changes, the battery management system can determine that the battery cell 5 corresponding to that FFC line has leaked, thus achieving cell-level positioning.
[0051] The battery management system may include a signal acquisition module, a processing module, and an alarm module. The signal acquisition module is used to acquire electrical signals from each FFC line in real time; the processing module is used to analyze changes in the electrical signal state to determine whether leakage has occurred; and the alarm module is used to issue an alarm signal or trigger corresponding safety protection measures when leakage is detected.
[0052] Example 3: Battery Pack like Figure 1-2 As shown, this embodiment provides a battery pack, including multiple battery cells 5, the battery cell leakage detection FFC line described in Embodiment 1, and a battery management system.
[0053] The window area 2 of the FFC line is attached to the surface of the cell 5. In this embodiment, there are multiple FFC lines, each corresponding to the surface of one cell 5, enabling independent monitoring of each cell 5. In other embodiments, one FFC line can also cover the surface of multiple cells 5 simultaneously to monitor leakage in multiple cells 5. In this case, a window area 2 needs to be set at the corresponding position of each cell 5.
[0054] The FFC lines are connected to the battery management system via connector 7. Multiple FFC lines can be connected to the same connector 7 or to different connectors 7 before being connected to the battery management system. Connector 7 is preferably a board-to-board connector or a wire-to-board connector for easy installation and maintenance.
[0055] The battery management system (BMS) monitors the electrical signal status of each FFC line. Under normal circumstances, the BMS receives normal electrical signals transmitted from each FFC line. When the electrical signal status of a certain FFC line changes, the BMS determines the location of the leaking cell based on this change and issues corresponding alarms or control commands, such as cutting off the corresponding circuit, activating cooling, or notifying maintenance personnel, to prevent safety accidents.
[0056] The battery pack in this embodiment can be a power battery pack for electric vehicles, a battery pack for energy storage power stations, or a battery pack for consumer electronics products. The number, layout, and location of the FFC lines can be optimized according to the specific structure of the battery pack and the arrangement of the cells.
[0057] Example 4: Cell Leakage Detection Method This embodiment provides a method for detecting cell leakage, applied to a battery pack cell monitoring system. The system includes an FFC line attached to the surface of the cell and a battery management system electrically connected to the FFC line. The FFC line has a windowed area that exposes an internal conductor, which is in a connected state.
[0058] The method includes the following steps: S1: Normal signal transmission procedure. The FFC line transmits normal electrical signals to the battery management system through the internal conductors exposed in its windowed area. In the absence of cell leakage, the exposed conductors in the windowed area serve as part of the FFC line signal transmission path, transmitting electrical signals normally, and the battery management system receives stable, expected electrical signals.
[0059] S2: Leakage-Induced Signal Change Step. When leakage occurs in the battery cell, the electrolyte leaks to the cell surface and directly contacts the exposed conductor in the windowed area. Due to the conductivity of the electrolyte, its contact with the exposed conductor alters the electrical signal state at the windowed area. This change in electrical signal state can be one or more of the following: signal attenuation, signal interference, impedance change, or short circuit, depending on the composition, quantity, and contact method of the electrolyte.
[0060] S3: Signal Monitoring Step. The battery management system monitors the electrical signal status of the FFC line in real time. Monitoring can be continuous or periodic. The battery management system can set a threshold range for normal signals; when the monitored signal exceeds this range, it is considered that the electrical signal status has changed.
[0061] S4: Leakage Detection Step. When the battery management system detects a change in the electrical signal state, it determines that a leakage has occurred in the corresponding cell. Since each FFC line corresponds to a specific cell or cell group, the battery management system can further determine the location of the leaking cell based on the FFC line where the signal change has occurred.
[0062] Furthermore, the method may also include S5: Alarm and Protection Steps. After determining that a leak has occurred, the battery management system issues an alarm signal and triggers corresponding safety protection measures, such as cutting off the corresponding circuit, activating the cooling system, and notifying the host computer or user.
[0063] The detection method in this embodiment is simple and reliable, requiring no complex sensors or algorithms, and can achieve real-time monitoring and location of cell leakage, effectively improving the safety of the battery pack.
[0064] Example 5: A method for manufacturing a cell leakage detection FFC line, comprising the following steps: An FFC substrate is provided, the FFC substrate including an insulating layer and an internal conductor, the internal conductor 3 being in a connected state; At least one window area 2 is formed on the FFC substrate corresponding to the potential leakage area of the cell to expose the internal conductor 3. The window area 2 is configured to be attached to the surface of the cell 5. A first connection terminal 4 is formed at one end of the FFC substrate, and a second connection terminal 6 is formed at the other end. The second connection terminal 6 is short-circuited by an electronic wire to form a signal circuit. The FFC substrate is cut to a size suitable for bonding to the surface of the battery cell.
[0065] Other implementation methods The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
[0066] For example, the shape, number, and location of the window area 2 can be adaptively adjusted according to the structure of the cell 5 and the leakage risk area. The window area 2 can be circular, square, strip-shaped, or other shapes, and can be single or multiple, and can be located in the middle or edge of the FFC line.
[0067] For example, in addition to copper foil, the internal conductor 3 can also be made of other conductive materials, such as aluminum foil, silver foil, alloy foil, etc., as long as it can cause a change in the electrical signal state when in contact with the electrolyte. The internal conductor 3 can be a single-layer or multi-layer structure.
[0068] For example, besides the exposed copper structure, the first connecting terminal 4 can also adopt other forms of electrical connection structure, such as soldered terminals, pins, gold fingers, etc. Connector 7 can also be selected according to actual needs.
[0069] Furthermore, the FFC line can be equipped with multiple open areas 2, each corresponding to a different cell 5 for leakage detection. In this case, the battery management system can distinguish the leakage status of different cells 5 based on the changes in the electrical signal state corresponding to different open areas 2.
[0070] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.
[0071] Industrial applicability The FFC line, monitoring system, battery pack, and detection method for cell leakage detection of this invention can be widely applied in various fields that use battery packs, such as electric vehicles, energy storage power stations, and consumer electronics. This invention features a simple structure, low cost, ease of manufacture and installation, and a reliable and efficient detection method, effectively improving the safety and reliability of battery packs. It has good industrial applicability and promotional value.
[0072] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. A cell leakage detection FFC line, characterized in that, include: The FFC body has at least one window area that exposes an internal conductor and is designed to be attached to the surface of a battery pack cell. The exposed internal conductors in the windowed area are in a connected state for transmitting normal electrical signals; One end of the FFC body is provided with a first connection terminal, and the other end is provided with a second connection terminal. The first connection terminal is used to connect with the battery management system to transmit the electrical signal. The adjacent second connection terminals are shorted by electronic wires to form a signal loop. When the battery cell leaks electrolyte, the electrolyte comes into contact with the exposed conductor in the windowed area, changing the electrical signal state at the windowed area and triggering an abnormal signal.
2. The cell leakage detection FFC line according to claim 1, characterized in that, The first connection terminal has an open copper structure for insertion with a connector to achieve a detachable electrical connection with the battery management system.
3. The cell leakage detection FFC line according to claim 1, characterized in that, The windowed area has a punched window structure, which exposes the internal conductor on the surface of the FFC body for direct contact with potential leakage areas of the cell.
4. A battery pack cell leakage monitoring system, characterized in that, include: At least one cell leakage detection FFC line as described in any one of claims 1 to 3, wherein the window area of the FFC line is attached to the surface of the cell; The battery management system is electrically connected to the first connection terminal of the FFC line and is used to monitor the electrical signal status of the FFC line and determine whether the corresponding cell has leaked based on the changes in the electrical signal status.
5. The system according to claim 4, characterized in that, The FFC line is connected to the battery management system via a connector.
6. A battery pack, characterized in that, include: Multiple battery cells; The cell leakage detection FFC line as described in any one of claims 1 to 3, wherein the window area of the FFC line is attached to the surface of the cell; The battery management system is electrically connected to the first connection terminal of the FFC line and is used to monitor the electrical signal status of the FFC line and determine the location of the cell where leakage has occurred based on the changes in the electrical signal status.
7. The battery pack according to claim 7, characterized in that, The number of FFC lines is multiple, and each FFC line is disposed on the surface of one or more battery cells to realize cell-level leakage monitoring.
8. A method for detecting cell leakage, applied to a battery pack cell monitoring system, the system comprising an FFC line attached to the surface of the cell and a battery management system electrically connected to the FFC line, wherein the FFC line has a windowed area exposing an internal conductor which is in a connected state, one end of the FFC line has a first connection terminal connected to the battery management system, and the other end has a second connection terminal short-circuited by an electronic wire to form a signal loop, characterized in that... The method includes the following steps: The FFC line transmits normal electrical signals to the battery management system through the internal conductors exposed in its windowed area. When leakage occurs in the battery cell, the electrolyte comes into contact with the exposed conductor in the windowed area, changing the electrical signal state at the windowed area. The battery management system monitors the electrical signal status of the FFC line. When a change in the electrical signal status is detected, it determines that the corresponding cell has leaked.
9. A method for manufacturing an FFC wire for detecting cell leakage, characterized in that, Includes the following steps: An FFC substrate is provided, the FFC substrate including an insulating layer and an internal conductor, the internal conductor being in a connected state; At least one window area is formed on the FFC substrate corresponding to the potential leakage area of the cell to expose the internal conductor, and the window area is configured to be attached to the surface of the cell. A first connection terminal is formed at one end of the FFC substrate, and a second connection terminal is formed at the other end. The second connection terminal is shorted by an electronic wire to form a signal circuit. The FFC substrate is cut to a size suitable for bonding to the surface of the battery cell.