Battery cell thermal runaway protection method, device, master control unit and system

Abstract

The application provides a battery cell thermal runaway protection method, device, main control unit and system, and is suitable for the technical field of battery cell thermal runaway. The method comprises the following steps: acquiring each monitoring parameter of the battery cell; each monitoring parameter comprises at least one of a resistance change rate, a temperature change rate and a shell expansion deformation; based on each monitoring parameter, a target early warning level of the battery cell is determined from multiple early warning levels; the multiple early warning levels are multiple levels set in sequence according to the thermal runaway degree of the battery cell; and based on the target early warning level of the battery cell, a protection strategy corresponding to the target early warning level is executed. The embodiments of the application can adopt the corresponding protection strategy according to the thermal runaway degree of the battery cell, and can timely take the corresponding protection strategy in the early stage of the thermal runaway of the battery cell, so that the problem of forced power-off directly due to slight abnormalities can be avoided through the multi-level progressive protection, and the continuity of the cycle life test of the battery cell is beneficial to be maintained.

Description

Technical Field

[0001] This application relates to the field of battery cell thermal runaway technology, and in particular to a method, device, main control unit and system for protecting against battery cell thermal runaway. Background Technology

[0002] Currently, when battery cells (e.g., single cylindrical cells) are independently charged and discharged, only basic voltage and current parameters are monitored. This makes it impossible to capture the early signs of thermal runaway inside the cell. The protection logic is also simple, with only hard cut-off for overvoltage / undervoltage / overcurrent. Minor abnormalities are directly forced to disconnect the power, which affects the continuity of cycle life testing. Summary of the Invention

[0003] In view of this, the present application provides a method for protecting against thermal runaway of battery cells, in order to solve the problems in the prior art that it is impossible to capture the precursory features of thermal runaway inside the battery cell or that the protection logic is too simple.

[0004] The first aspect of this application provides a method for protecting against thermal runaway of a battery cell, including: Acquire various monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: rate of change of resistance, rate of change of temperature, and expansion deformation of the casing. Based on various monitoring parameters, the target warning level for the battery cell is determined from the multi-level warning levels; the multi-level warning levels are multiple levels set sequentially according to the degree of thermal runaway of the battery cell. Based on the target warning level of the battery cell, the corresponding protection strategy is executed.

[0005] In one possible implementation, based on various monitoring parameters, the target early warning level for the battery cell is determined from a multi-level early warning system, including: If any monitoring parameter meets any of the preset early warning conditions, then based on the correspondence between the early warning level and the early warning condition, the target early warning level of the battery cell is determined from the multi-level early warning levels.

[0006] In one possible implementation, the monitoring parameters also include at least one of the following: temperature change value, temperature value, combustible gas detection concentration, and instantaneous voltage drop value.

[0007] In one possible implementation, the preset early warning conditions include Level 1, Level 2, Level 3, and Level 4 early warning conditions, and the multi-level early warning levels include Level 1, Level 2, Level 3, and Level 4 early warning levels; The first-level warning conditions include the warning conditions for the rate of change of resistance, the warning conditions for the rate of change of temperature, and the warning conditions for the expansion and deformation of the casing; the first-level warning conditions correspond to the first-level warning level, which is used to indicate that the cell has a slight abnormality and no safety risk. The secondary warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion deformation, and warning conditions for temperature change value; the secondary warning conditions correspond to the secondary warning level, which is used to indicate moderate abnormality or slight gas production risk of the battery cell; The three-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion and deformation, warning conditions for temperature value, and warning conditions for combustible gas detection concentration. The three-level warning conditions correspond to three-level warning levels, which are used to indicate severe cell abnormalities, large gas production risks, or the risk of explosion-proof valve opening. The four-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature value, warning conditions for shell expansion deformation, warning conditions for combustible gas detection concentration, and warning conditions for instantaneous voltage drop value. The four-level warning conditions correspond to four-level warning levels, which are used to indicate that the battery cell has reached the thermal runaway critical point or that the explosion-proof valve has opened or there is a risk of fire.

[0008] In one possible implementation, based on the target warning level of the battery cell, the protection strategy corresponding to the target warning level is executed, including: If the target warning level of the battery cell is Level 1, then at least one of the following protection strategies shall be executed: record the warning log, maintain the current charging and discharging current, or start the heat dissipation system. If the target warning level of the battery cell is Level 2, then at least one of the following protection strategies shall be implemented: reduce the charging and discharging current, increase the power of the heat dissipation system, extend the resting time in the charging and discharging cycle mode of the battery cell, and upgrade to Level 3 warning level after two charging and discharging cycles when the Level 2 warning level is met. If the target warning level of the battery cell is Level 3, then at least one of the following protection strategies shall be implemented: disconnect the constant current charging and discharging circuit, enter the static cooling stage, prohibit charging and discharging again, and lock the charging and discharging cycle program of the battery cell. If the target warning level for the battery cell is Level 4, then at least one of the following protection strategies shall be executed: disconnect the main circuit relay, start the spray cooling system, push alarm information, control the battery cell to move to the explosion-proof fire extinguishing chamber, and lock the test channel of the battery cell.

[0009] In one possible implementation, the rate of temperature change includes a first rate of temperature change, a second rate of temperature change, and a third rate of temperature change; The first temperature change rate is measured by the first temperature sensor located on the top of the explosion-proof valve of the battery cell; the second temperature change rate is measured by the second temperature sensor located in the middle of the steel shell of the battery cell; and the third temperature change rate is measured by the third temperature sensor located on the bottom negative electrode tab of the battery cell. The rate of change of resistance is obtained by detecting the voltage and charging / discharging current through sampling lines connected to the positive and negative terminals of the battery cell; The expansion deformation of the casing is obtained by measuring the distance at the middle of the side wall of the battery cell using a distance measuring sensor.

[0010] A second aspect of this application provides a protection device for thermal runaway of a battery cell, comprising: The acquisition module is used to acquire various monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation. The warning level determination module is used to determine the target warning level of the battery cell from multiple warning levels based on various monitoring parameters; the multiple warning levels are set sequentially according to the degree of thermal runaway of the battery cell. The protection execution module is used to execute the protection strategy corresponding to the target warning level based on the target warning level of the battery cell.

[0011] A third aspect of this application provides a master control unit, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method of the first aspect.

[0012] A fourth aspect of this application provides a battery management system, including: a data acquisition unit and a main control unit as described in the third aspect; The data acquisition unit is used to collect monitoring data of the battery cell during the charging and discharging process; The main control unit is used to obtain various monitoring parameters based on the monitoring data.

[0013] A fifth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the method of the first aspect.

[0014] Compared with the prior art, the embodiments of this application have at least the following technical effects: The cell thermal runaway protection method of this application embodiment can acquire various monitoring parameters of the cell, including at least one of the resistance change rate, temperature change rate, and shell expansion deformation. By using multiple different monitoring parameters, early signs of thermal runaway within the cell can be captured in a timely manner, avoiding direct judgment based solely on voltage and current, thus improving the accuracy of cell thermal runaway monitoring. Then, based on these monitoring parameters, a target warning level for the cell is determined from a multi-level warning system. This multi-level warning system consists of several levels sequentially set according to the degree of thermal runaway, enabling multi-level warnings. Based on the target warning level, the corresponding protection strategy is executed, achieving graded and progressive protection for different warning levels. Therefore, this application embodiment can adopt corresponding protection strategies according to the degree of thermal runaway of the cell, and can take timely action in the early stages of thermal runaway. Multi-level progressive protection avoids the problem of directly forcibly cutting off power for minor anomalies, which is beneficial for maintaining the continuity of cell cycle life testing.

[0015] It is understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a method for protecting against thermal runaway of a battery cell provided in an embodiment of this application; Figure 2 This is a flowchart of another method for protecting against thermal runaway of battery cells provided in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of a battery cell thermal runaway protection device provided in an embodiment of this application; Figure 4 This is a schematic diagram of the main control unit provided in the embodiments of this application. Detailed Implementation

[0018] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0019] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0020] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0021] In the description of this application, unless otherwise stated, the " / " used in this specification and appended claims indicates that the related objects are in an "or" relationship. For example, A / B can mean A or B. The "and / or" in this application merely describes the relationship between the related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone, where A and B can be singular or plural. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a and b, a and c, b and c, or a, b, and c. Here, a, b, and c can be single or multiple.

[0022] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0023] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0024] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0025] Research has found that cylindrical lithium-ion batteries are widely used in energy storage, power tools, consumer electronics, and single-cell testing of power battery packs. Existing battery protection solutions are mostly integrated into the BMS (Battery Management System), which has the following drawbacks when designed for the entire battery pack: When a single cylindrical cell is tested independently in a cycle, only the basic parameters of voltage and current are monitored, which cannot capture the early signs of thermal runaway inside the cell (e.g., temperature rise, temperature difference between the casing and the cell, gas expansion, sudden change in internal resistance). The protection logic is simplistic, relying solely on hard cutoff for overvoltage / undervoltage / overcurrent, lacking tiered warnings and progressive current limiting protection. Minor anomalies result in direct forced power-off, impacting the continuity of cycle life testing. The unique cylindrical cell structure—including the wound core, CID (Pressure Relief Vent / Current Interrupt Device) explosion-proof valve, and aluminum-plastic / steel shell seal—leads to internal gas generation during charging and discharging, causing shell deformation. Existing monitoring methods lack shell deformation detection, failing to identify the opening of the explosion-proof valve and internal short-circuit risks in advance. Conventional temperature acquisition relies on single-point temperature measurement of the outer shell, ignoring high-temperature hotspots in the tab and cap CID areas. The cap is the initial trigger point for thermal runaway, resulting in a high false alarm rate for single-point temperature measurements. A multi-dimensional fusion judgment model has not been established for the coupling characteristics of dynamic internal resistance, voltage hysteresis, and temperature rise rate during charge and discharge cycles. Early faults such as minor micro-short circuits, lithium plating, and electrolyte decomposition cannot be identified until leakage or fire occurs, triggering protection.

[0026] Existing technologies lack an integrated monitoring and protection method that is specific to a single cylindrical battery cell, simultaneously collects data from multiple physical fields, provides layered early warning, and offers gradient protection. This makes it impossible to balance the integrity of cyclic test data with proactive prevention of thermal runaway.

[0027] The battery cell thermal runaway protection method, device, main control unit and system provided in this application are intended to solve the above-mentioned technical problems of the prior art.

[0028] The technical solution of this application and how it solves the above-mentioned technical problems are described in detail below with specific embodiments. It should be noted that the following embodiments can be referenced, borrowed, or combined with each other, and the same terms, similar features, and similar implementation steps in different embodiments will not be described again.

[0029] See Figure 1 As shown, this application provides a flowchart of a method for protecting against thermal runaway of a battery cell. Figure 1 As shown, the method for protecting against thermal runaway of the battery cell includes steps S101 to S103.

[0030] S101. Acquire the monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation.

[0031] In some embodiments, the rate of temperature change includes a first rate of temperature change, a second rate of temperature change, and a third rate of temperature change. The first temperature change rate is measured by the first temperature sensor located on the top of the explosion-proof valve of the battery cell; the second temperature change rate is measured by the second temperature sensor located in the middle of the steel shell of the battery cell; and the third temperature change rate is measured by the third temperature sensor located on the bottom negative electrode tab of the battery cell. The rate of change of resistance is obtained by detecting the voltage and charging / discharging current through sampling lines connected to the positive and negative terminals of the battery cell; The expansion deformation of the casing is obtained by measuring the distance at the middle of the side wall of the battery cell using a distance measuring sensor.

[0032] Optionally, the battery cell is a single cylindrical lithium-ion battery. The method of this application embodiment is applicable to the charge-discharge cycle safety monitoring and protection method of a single cylindrical lithium-ion battery. It employs three-point temperature measurement: the top of the cell cap (CID), the middle steel shell of the cell, and the bottom negative electrode tab of the cell. This method is specifically designed to address the structural characteristics of the cylindrical cell cap, which is a high-heat point for thermal runaway. Then, combined with a lateral laser non-contact casing expansion detection using a distance sensor, it can detect early signs of gas bulging and the opening of the explosion-proof valve, overcoming the shortcomings of traditional solutions that completely ignore cell deformation and cap hotspot monitoring. Simultaneously, this application embodiment can also monitor the thermal runaway process of the cell based on the resistance change rate formed by the ratio of the current resistance to a preset resistance. The preset resistance is the resistance during the normal charge-discharge process of the cell.

[0033] In some embodiments, each monitoring parameter further includes at least one of temperature change value, temperature value, combustible gas detection concentration, and voltage instantaneous drop value.

[0034] The embodiments of this application can also monitor the degree of thermal runaway of the battery cell based on monitoring parameters such as temperature change value, temperature value, combustible gas detection concentration, and instantaneous voltage drop value.

[0035] S102. Based on various monitoring parameters, determine the target warning level of the battery cell from the multi-level warning levels; the multi-level warning levels are multiple levels set sequentially according to the degree of thermal runaway of the battery cell.

[0036] In some embodiments, based on various monitoring parameters, a target warning level for the battery cell is determined from a multi-level warning system, including: If any monitoring parameter meets any of the preset early warning conditions, then based on the correspondence between the early warning level and the early warning condition, the target early warning level of the battery cell is determined from the multi-level early warning levels.

[0037] Each warning level in this application embodiment is set with corresponding warning conditions. By matching each monitoring parameter with the warning conditions, the target warning level of the battery cell can be determined when any monitoring parameter meets any of the preset warning conditions.

[0038] Optionally, the preset warning conditions include Level 1 warning conditions, Level 2 warning conditions, Level 3 warning conditions, and Level 4 warning conditions, and the multi-level warning levels include Level 1 warning level, Level 2 warning level, Level 3 warning level, and Level 4 warning level.

[0039] The embodiments of this application can set four levels of early warning according to the degree of thermal runaway of the battery cell to achieve multi-level progressive protection.

[0040] S103. Based on the target warning level of the battery cell, execute the protection strategy corresponding to the target warning level.

[0041] In some embodiments, based on the target warning level of the battery cell, a protection strategy corresponding to the target warning level is executed, including: If the target warning level of the battery cell is Level 1, then at least one of the following protection strategies shall be executed: record the warning log, maintain the current charging and discharging current, or start the heat dissipation system. If the target warning level of the battery cell is Level 2, then at least one of the following protection strategies shall be implemented: reduce the charging and discharging current, increase the power of the heat dissipation system, extend the resting time in the charging and discharging cycle mode of the battery cell, and upgrade to Level 3 warning level after two charging and discharging cycles when the Level 2 warning level is met. If the target warning level of the battery cell is Level 3, then at least one of the following protection strategies shall be implemented: disconnect the constant current charging and discharging circuit, enter the static cooling stage, prohibit charging and discharging again, and lock the charging and discharging cycle program of the battery cell. If the target warning level for the battery cell is Level 4, then at least one of the following protection strategies shall be executed: disconnect the main circuit relay, start the spray cooling system, push alarm information, control the battery cell to move to the explosion-proof fire extinguishing chamber, and lock the test channel of the battery cell.

[0042] The embodiments of this application can implement different protection strategies according to different warning levels, and adopt graded and progressive protection to better ensure the charging and discharging process of the battery.

[0043] The cell thermal runaway protection method of this application embodiment can obtain various monitoring parameters of the cell, including at least one of resistance change rate, temperature change rate and shell expansion deformation. By using multiple different monitoring parameters, the early signs of thermal runaway inside the cell can be captured in time, avoiding direct judgment based solely on voltage and current, and improving the monitoring accuracy of cell thermal runaway.

[0044] Then, based on various monitoring parameters, the target warning level for the battery cell is determined from the multi-level warning levels. These multi-level warning levels are set sequentially according to the degree of thermal runaway of the battery cell, enabling multi-level warnings. Based on the target warning level of the battery cell, the corresponding protection strategy is executed, achieving graded and progressive protection for different warning levels. Therefore, the embodiments of this application can adopt corresponding protection strategies according to the degree of thermal runaway of the battery cell, and can take timely action in the early stages of thermal runaway. Multi-level progressive protection avoids the problem of directly forcibly cutting off power for minor anomalies, which is beneficial for maintaining the continuity of battery cell cycle life testing.

[0045] Optionally, the embodiments of this application specifically relate to the field of lithium-ion battery safety testing and energy storage protection technology, and can be a method for real-time safety monitoring and multiple protections during the charge and discharge cycle of a single cylindrical lithium-ion battery.

[0046] See Figure 2 As shown, this application provides a flowchart of another method for protecting against thermal runaway of battery cells. Figure 2 As shown, the method for protecting against thermal runaway of the battery cell includes steps S201 to S206.

[0047] S201. Obtain the monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation.

[0048] In some embodiments, each monitoring parameter further includes at least one of temperature change value, temperature value, combustible gas detection concentration, and voltage instantaneous drop value.

[0049] S202. If any monitoring parameter meets any of the preset early warning conditions, then based on the correspondence between the early warning level and the early warning condition, the target early warning level of the battery cell is determined from the multi-level early warning levels.

[0050] In some embodiments, the preset warning conditions include Level 1 warning conditions, Level 2 warning conditions, Level 3 warning conditions, and Level 4 warning conditions, and the multi-level warning levels include Level 1 warning level, Level 2 warning level, Level 3 warning level, and Level 4 warning level; The first-level warning conditions include the warning conditions for the rate of change of resistance, the warning conditions for the rate of change of temperature, and the warning conditions for the expansion and deformation of the casing; the first-level warning conditions correspond to the first-level warning level, which is used to indicate that the cell has a slight abnormality and no safety risk. The secondary warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion deformation, and warning conditions for temperature change value; the secondary warning conditions correspond to the secondary warning level, which is used to indicate moderate abnormality or slight gas production risk of the battery cell; The three-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion and deformation, warning conditions for temperature value, and warning conditions for combustible gas detection concentration. The three-level warning conditions correspond to three-level warning levels, which are used to indicate severe cell abnormalities, large gas production risks, or the risk of explosion-proof valve opening. The four-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature value, warning conditions for shell expansion deformation, warning conditions for combustible gas detection concentration, and warning conditions for instantaneous voltage drop value. The four-level warning conditions correspond to four-level warning levels, which are used to indicate that the battery cell has reached the thermal runaway critical point or that the explosion-proof valve has opened or there is a risk of fire.

[0051] S203. If the target warning level of the battery cell is Level 1, then at least one of the following protection strategies shall be executed: record the warning log, maintain the current charging and discharging current, or start the heat dissipation system.

[0052] S204. If the target warning level of the battery cell is Level 2, then at least one of the following protection strategies shall be implemented: reduce the charging and discharging current, increase the power of the heat dissipation system, extend the resting time in the charging and discharging cycle mode of the battery cell, and upgrade to Level 3 warning level after two charging and discharging cycle modes are executed if Level 2 warning level is met.

[0053] Optionally, the charge-discharge cycle mode includes a complete cycle process of constant current charging, constant voltage float charging, resting, constant current discharging, and resting, with all collected data stored synchronously in each cycle.

[0054] S205. If the target warning level of the battery cell is a level three warning level, then at least one of the following protection strategies shall be implemented: disconnect the constant current charging and discharging circuit, enter the static cooling stage, prohibit charging and discharging again, and lock the charging and discharging cycle program of the battery cell.

[0055] S206. If the target warning level of the battery cell is Level 4, then at least one of the following protection strategies shall be executed: disconnect the main circuit relay, start the spray cooling system, push alarm information, control the battery cell to move to the explosion-proof fire extinguishing chamber, and lock the test channel of the battery cell.

[0056] This application integrates features such as voltage, current, three-point temperature, temperature rise rate, shell expansion amount, expansion rate, dynamic internal resistance, internal resistance change, temperature difference, and combustible gas concentration. It adopts an AND / OR multi-level fusion threshold model, so minor disturbances will not trigger protection, and real internal faults can be stably identified. It balances monitoring accuracy and testing continuity, and solves the problem that existing technologies rely solely on voltage and current as single indicators to judge faults, which are easily subject to charging and discharging fluctuations and line voltage drop interference, resulting in false shutdowns.

[0057] Optionally, the first-level warning conditions include a resistance change rate that is not less than a first change rate and not greater than a second change rate, a temperature change rate that is not less than a first temperature change rate and lasts for a first predetermined duration, and a shell expansion deformation that is not less than a first deformation value.

[0058] The temperature change rate can be at least one of the first temperature change rate, the second temperature change rate, and the third temperature change rate.

[0059] Optionally, the secondary warning conditions include a resistance change rate greater than a second change rate but not greater than a third change rate, a temperature change rate not less than a second temperature change rate, a shell expansion deformation not less than a second deformation value, and a temperature change value greater than a first temperature change value.

[0060] The temperature change value can be at least one of a first temperature change value, a second temperature change value, and a third temperature change value. The first temperature change value, the second temperature change value, and the third temperature change value are obtained from the temperature values ​​detected by the first temperature sensor, the second temperature sensor, and the third temperature sensor, respectively.

[0061] Optionally, the three-level warning conditions include a resistance change rate greater than a third change rate, a temperature change rate not less than a third temperature change rate, a shell expansion deformation not less than a third deformation value, a temperature value greater than a first temperature value, and a combustible gas detection concentration greater than a first concentration value.

[0062] Optionally, the four-level warning conditions include a resistance change rate greater than the fourth change rate, a temperature value greater than the second temperature value, a shell expansion deformation not less than the fourth deformation value, a combustible gas detection concentration greater than the second concentration value, and a voltage instantaneous drop value greater than the first voltage.

[0063] In this embodiment, the parameter thresholds are set according to different warning levels. The warning levels from Level 1 to Level 4 are set sequentially according to the severity of thermal runaway of the battery cell, and the parameter thresholds gradually increase in different warning levels.

[0064] As an example, this application provides a four-level fault threshold fusion judgment model. This application sets four security levels and employs multi-parameter "OR + AND" fusion logic to avoid false triggering by a single parameter.

[0065] (1) Level 1 warning (minor anomaly, no safety risk) The following conditions must be met: ① 1.1 ≤ resistance change rate k ≤ 1.2; ② temperature change rate ΔT / Δt ≥ 0.5℃ / min and last for 30s; ③ shell expansion deformation ΔL ≥ 0.1mm; Protection strategy: The host computer pops up a warning log, does not cut off the circuit, maintains the original charging and discharging current, starts low-speed air cooling, and continues to execute the cycle.

[0066] (2) Level II warning (moderate anomaly, with a risk of lithium plating / slight gas production) The following conditions must be met: ① 1.2 < k ≤ 1.5; ② ΔT / Δt ≥ 1℃ / min; ③ ΔL ≥ 0.2mm; ④ Temperature change ΔT ≥ 8℃. Protection strategies: Halve the charging and discharging current, increase the power of the heat dissipation system, extend the resting time, upload data at high frequency in real time, and upgrade to the third-level warning level if the system fails to recover after two consecutive charging and discharging cycles.

[0067] (3) Level 3 warning (severe anomaly, internal micro-short circuit, risk of large-scale gas production, risk of explosion-proof valve opening) The following conditions must be met: ① k > 1.5; ② ΔT / Δt ≥ 2℃ / min; ③ ΔL ≥ 0.35mm; ④ T1 ≥ 55℃; ⑤ A trace amount of combustible gas is detected, and the detected concentration of combustible gas is greater than the first concentration value; T1 is the temperature value detected by the first temperature sensor. Protection strategy: Immediately disconnect the constant current charging and discharging circuit, enter the static cooling stage, prohibit recharging, lock the charging and discharging cycle program of the battery cell in the host computer, and manually check the status of the battery cell.

[0068] (4) Level IV warning level (critical thermal runaway, explosion-proof valve opening, fire risk) If any of the following conditions are met: ①T1≥70℃; ②ΔL≥0.5mm; ③Internal resistance increases by more than 3 times; ④The concentration of combustible gas detected is greater than the second concentration value, and the concentration exceeds the standard; ⑤The voltage drops by more than 0.5V instantaneously. Protection strategy: The main circuit relay quickly disconnects, completely cutting off the charging and discharging power supply; the forced water cooling / spray cooling system is activated; an audible and visual alarm is pushed along with a remote APP alarm; a mechanical pusher pushes the battery cell to an independent explosion-proof fire extinguishing chamber to isolate oxygen and release pressure; the test channel is locked to prevent power-on again.

[0069] The embodiments of this application can perform real-time monitoring of key safety parameters (temperature, voltage, current, gas, pressure) of a single cylindrical lithium-ion battery during charge-discharge cycles, conduct collaborative analysis and early warning, and achieve rapid response and safety protection when an anomaly is detected.

[0070] This application's embodiments can be specifically designed for single cylindrical battery cell structures, adding cap CID hotspot temperature measurement and shell expansion laser detection to capture the unique gas bulging and cap high-temperature failure precursors of cylindrical battery cells, which is far superior to traditional single-point temperature measurement solutions; a multi-physics field fusion judgment model avoids false protection by single voltage / current, and the graded protection mechanism takes into account the data continuity of laboratory cyclic testing, ensuring that minor anomalies do not interrupt the cycle; four-level gradient protection intervenes step by step, from early warning, current limiting, shutdown to isolation and fire extinguishing, intervening in the incipient stage of thermal runaway, significantly reducing the risk of fire and explosion.

[0071] This application embodiment can also be equipped with a fault tracing function, automatically locate the fault SOC (System on Chip) range, analyze lithium, micro short circuit, and electrolyte decomposition faults, and provide quantitative data for the optimization of cylindrical cell materials and processes.

[0072] This application provides a battery management system, including: a data acquisition unit and a main control unit according to this application embodiment; the data acquisition unit is used to acquire monitoring data of the battery cell during the charging and discharging process; the main control unit is used to obtain various monitoring parameters based on the monitoring data.

[0073] Optionally, the main control unit is a microcontroller unit (MCU). The acquisition unit includes a first temperature sensor, a second temperature sensor, a third temperature sensor, a ranging sensor, a combustible gas concentration sensor, and sampling lines connected to the positive and negative terminals of the battery cell.

[0074] Optionally, the battery management system includes a main control MCU, a charging / discharging power circuit, a data acquisition unit, an execution protection module, and a host computer recording unit. Five types of data acquisition points are set for a single cylindrical cell: Electrical parameter acquisition: Real-time acquisition of terminal voltage V and charging / discharging current I via the cell's positive and negative electrode sampling lines, sampled every 10ms; Multi-point temperature acquisition: Three NTC thermistors: ① Temperature measurement point T1 on top of the CID explosion-proof valve cap; ② Temperature measurement point T2 in the middle of the cell's steel shell; ③ Temperature measurement point T3 on the bottom of the cell's negative electrode tab; Shell expansion and deformation acquisition: A distance sensor uses a laser to align with the middle of the cell's sidewall to acquire real-time shell expansion and deformation ΔL; AC internal resistance acquisition: Real-time dynamic internal resistance R using the AC four-wire method, updated every 1s; Environmental auxiliary acquisition: Cavity ambient temperature T0, and a combustible gas concentration sensor (monitoring the volatile gases from electrolyte decomposition and detecting combustible gas concentration). Optionally, the main control unit inputs rated parameters according to the cell model (18650 / 21700, etc.): rated capacity C, nominal voltage Vn, charging cut-off voltage Vmax, discharging cut-off voltage Vmin, maximum charging / discharging current Imax, standard internal resistance R0 (as a preset resistor), standard operating temperature range, and maximum allowable expansion threshold Lmax of the casing. The charge / discharge cycle mode includes a complete cycle process of constant current charging, constant voltage float charging, resting, constant current discharging, and resting, and all collected data are stored synchronously in each cycle.

[0075] As an example, the cell assembly and multi-physics field monitoring point layout: a single cylindrical lithium-ion cell is fixed to an insulating clamp, and electrical parameter acquisition points, three-point temperature acquisition points, shell laser deformation acquisition points, dynamic internal resistance acquisition points, and combustible gas acquisition points are arranged. Temperature acquisition points are set at the top of the CID explosion-proof valve on the battery cell cover, the middle of the steel shell of the battery cell, and the bottom negative electrode tab of the battery cell. The rated parameters of the battery cell are pre-calibrated and the charging and discharging cycle standard system is entered. Voltage, current, three-channel temperature, shell expansion deformation, dynamic AC internal resistance, and cavity combustible gas concentration are collected synchronously throughout the charging and discharging cycle. The temperature rise rate, shell expansion rate, resistance change rate, and fault characteristic quantity of the temperature difference between the cover and the shell are calculated. A four-level fault fusion judgment model is established, and four warning levels are divided into level one warning, level two current limiting, level three shutdown, and level four emergency thermal runaway protection based on the threshold of multi-feature parameter combination. The corresponding graded protection strategy is executed according to the judgment warning level. After a single charging and discharging cycle is completed, the multi-parameter change curve is fitted and compared with the historical normal cycle curve to complete the fault source tracing. According to the fault level, the battery cell is automatically restored to cycle, restarted after manual re-inspection, or directly scrapped.

[0076] See Figure 3 As shown, this application provides a schematic diagram of the structure of a battery cell thermal runaway protection device 30. Figure 3 As shown, the cell thermal runaway protection device 30 includes: an acquisition module 301, an early warning level determination module 302, and a protection execution module 303.

[0077] The acquisition module 301 is used to acquire various monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation. The warning level determination module 302 is used to determine the target warning level of the battery cell from multiple warning levels based on various monitoring parameters; the multiple warning levels are multiple warning levels set sequentially according to the degree of thermal runaway of the battery cell. The protection execution module 303 is used to execute the protection strategy corresponding to the target warning level based on the battery cell target warning level.

[0078] Optionally, if any monitoring parameter meets any of the preset warning conditions, the warning level determination module 302 determines the target warning level of the battery cell from the multi-level warning levels based on the correspondence between the warning level and the warning conditions.

[0079] Optionally, each monitoring parameter may also include at least one of the following: temperature change value, temperature value, combustible gas detection concentration, and voltage instantaneous drop value.

[0080] Optionally, the preset warning conditions include Level 1 warning conditions, Level 2 warning conditions, Level 3 warning conditions, and Level 4 warning conditions, and the multi-level warning levels include Level 1 warning level, Level 2 warning level, Level 3 warning level, and Level 4 warning level; The first-level warning conditions include the warning conditions for the rate of change of resistance, the warning conditions for the rate of change of temperature, and the warning conditions for the expansion and deformation of the casing; the first-level warning conditions correspond to the first-level warning level, which is used to indicate that the cell has a slight abnormality and no safety risk. The secondary warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion deformation, and warning conditions for temperature change value; the secondary warning conditions correspond to the secondary warning level, which is used to indicate moderate abnormality or slight gas production risk of the battery cell; The three-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature change rate, warning conditions for shell expansion and deformation, warning conditions for temperature value, and warning conditions for combustible gas detection concentration. The three-level warning conditions correspond to three-level warning levels, which are used to indicate severe cell abnormalities, large gas production risks, or the risk of explosion-proof valve opening. The four-level warning conditions include warning conditions for resistance change rate, warning conditions for temperature value, warning conditions for shell expansion deformation, warning conditions for combustible gas detection concentration, and warning conditions for instantaneous voltage drop value. The four-level warning conditions correspond to four-level warning levels, which are used to indicate that the battery cell has reached the thermal runaway critical point or that the explosion-proof valve has opened or there is a risk of fire.

[0081] Optionally, the protection execution module 303 is used to execute at least one of the following protection strategies if the target warning level of the battery cell is a level one warning level: record the warning log, maintain the current charging and discharging current, and start the heat dissipation system. If the target warning level of the battery cell is Level 2, then at least one of the following protection strategies shall be implemented: reduce the charging and discharging current, increase the power of the heat dissipation system, extend the resting time in the charging and discharging cycle mode of the battery cell, and upgrade to Level 3 warning level after two charging and discharging cycles when the Level 2 warning level is met. If the target warning level of the battery cell is Level 3, then at least one of the following protection strategies shall be implemented: disconnect the constant current charging and discharging circuit, enter the static cooling stage, prohibit charging and discharging again, and lock the charging and discharging cycle program of the battery cell. If the target warning level for the battery cell is Level 4, then at least one of the following protection strategies shall be executed: disconnect the main circuit relay, start the spray cooling system, push alarm information, control the battery cell to move to the explosion-proof fire extinguishing chamber, and lock the test channel of the battery cell.

[0082] Optionally, the temperature change rate includes a first temperature change rate, a second temperature change rate, and a third temperature change rate; The first temperature change rate is measured by the first temperature sensor located on the top of the explosion-proof valve of the battery cell; the second temperature change rate is measured by the second temperature sensor located in the middle of the steel shell of the battery cell; and the third temperature change rate is measured by the third temperature sensor located on the bottom negative electrode tab of the battery cell. The rate of change of resistance is obtained by detecting the voltage and charging / discharging current through sampling lines connected to the positive and negative terminals of the battery cell; The expansion deformation of the casing is obtained by measuring the distance at the middle of the side wall of the battery cell using a distance measuring sensor.

[0083] In applications, the modules in the cell thermal runaway protection device 30 can be software program modules, or they can be implemented through different logic circuits integrated in the processor, or they can be implemented through multiple distributed processors.

[0084] The cell thermal runaway protection device 30 of this application embodiment can execute the method provided in this application embodiment. The implementation principle is similar. The actions performed by each module in the cell thermal runaway protection device 30 of each embodiment of this application correspond to the steps in the method of each embodiment of this application. For detailed functional descriptions of each module of the cell thermal runaway protection device 30, please refer to the descriptions in the corresponding methods shown above, which will not be repeated here.

[0085] This application provides a main control unit, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the method of this application.

[0086] See Figure 4 As shown in the diagram, this application provides a schematic diagram of the structure of a main control unit 40. Figure 4 As shown, the main control unit 40 of this application embodiment includes: a memory 42, a processor 41, and a computer program 43 stored in the memory 42 and executable on the processor 41. When the processor 41 executes the computer program, it implements the steps of the methods of the various embodiments of this application.

[0087] The main control unit 40 may include, but is not limited to, a processor 41 and a memory 42. Those skilled in the art will understand that the main control unit 40 may also include more or fewer components, or combinations of certain components, or different components, such as input / output devices, network access devices, etc.

[0088] The processor 41 can be a Central Processing Unit (CPU), but it can also be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0089] In some embodiments, memory 42 may be an internal storage unit, such as a hard disk or RAM. Memory 42 may be a removable / non-removable, volatile / non-volatile computer system storage medium; for example, memory 42 may be a non-volatile memory used for reading and writing non-volatile magnetic media. In other embodiments, memory 42 may be an external storage device, such as a pluggable hard disk on the main control unit 40, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Memory 42 is used to store the operating system, applications, bootloader, data, and other programs, such as program code for computer programs. Memory 42 may also be used to temporarily store data that has been output or will be output.

[0090] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0091] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0092] This application also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps in the above-described method embodiments.

[0093] If the integrated units described above are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include at least: any entity or device capable of carrying computer program code to a device / terminal equipment, a recording medium, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium. Examples include USB flash drives, portable hard drives, magnetic disks, or optical disks.

[0094] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc. The storage medium can also include combinations of the above types of memory.

[0095] This application provides a computer program product that, when run on a processor, enables the processor to execute the steps described in the various method embodiments above.

[0096] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0097] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0098] In the embodiments provided in this application, it should be understood that the disclosed apparatus / network devices and methods can be implemented in other ways. For example, the apparatus / network device embodiments described above are merely illustrative. For instance, the division of modules or units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0099] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0100] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for protecting against thermal runaway in battery cells, characterized in that, include: Acquire various monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation. Based on the monitoring parameters, the target warning level for the battery cell is determined from the multi-level warning levels; The multi-level early warning system consists of multiple levels set sequentially according to the degree of thermal runaway of the battery cell. Based on the target warning level of the battery cell, the protection strategy corresponding to the target warning level is executed.

2. The method for protecting against thermal runaway of a battery cell according to claim 1, characterized in that, The determination of the target warning level for the battery cell from multiple warning levels based on the monitoring parameters includes: If any of the monitoring parameters meets any of the preset warning conditions, then based on the correspondence between the warning level and the warning conditions, the target warning level of the battery cell is determined from the multi-level warning levels.

3. The method for protecting against thermal runaway of a battery cell according to claim 2, characterized in that, Each of the monitoring parameters also includes at least one of the following: temperature change value, temperature value, combustible gas detection concentration, and instantaneous voltage drop value.

4. The method for protecting against thermal runaway of a battery cell according to claim 3, characterized in that, The preset early warning conditions include Level 1, Level 2, Level 3, and Level 4 early warning conditions, and the multi-level early warning levels include Level 1, Level 2, Level 3, and Level 4 early warning levels; The first-level warning conditions include the warning conditions for the resistance change rate, the warning conditions for the temperature change rate, and the warning conditions for the shell expansion deformation; the first-level warning conditions correspond to the first-level warning level, which is used to indicate that the battery cell has a slight abnormality and no safety risk. The secondary warning conditions include warning conditions for the resistance change rate, warning conditions for the temperature change rate, warning conditions for the shell expansion deformation, and warning conditions for the temperature change value. The secondary warning condition corresponds to the secondary warning level, which is used to indicate that the battery cell has a moderate abnormality or a slight risk of gas production. The three-level early warning conditions include the early warning conditions for the resistance change rate, the early warning conditions for the temperature change rate, the early warning conditions for the shell expansion deformation, the early warning conditions for the temperature value, and the early warning conditions for the combustible gas detection concentration. The three-level warning conditions correspond to the three-level warning levels, and the three-level warning levels are used to indicate that the battery cell is severely abnormal or there is a risk of large-scale gas production or that the explosion-proof valve is at risk of opening. The four-level early warning conditions include the early warning conditions for the resistance change rate, the early warning conditions for the temperature value, the early warning conditions for the shell expansion deformation, the early warning conditions for the combustible gas detection concentration, and the early warning conditions for the instantaneous voltage drop value. The four-level warning conditions correspond to the four-level warning levels, which are used to indicate that the battery cell has reached the thermal runaway critical point or that the explosion-proof valve has been opened or there is a risk of fire.

5. The method for protecting against thermal runaway of a battery cell according to claim 4, characterized in that, The method of executing the protection strategy corresponding to the target warning level based on the battery cell includes: If the target warning level of the battery cell is Level 1, then at least one of the following protection strategies shall be executed: record the warning log, maintain the current charging and discharging current, and start the heat dissipation system; If the target warning level of the battery cell is a level 2 warning level, then at least one of the following protection strategies shall be implemented: reduce the charging and discharging current, increase the power of the heat dissipation system, extend the resting time in the charging and discharging cycle mode of the battery cell, and upgrade to a level 3 warning level when the level 2 warning level is met after executing two charging and discharging cycle modes. If the target warning level of the battery cell is a level three warning level, then at least one of the following protection strategies shall be executed: cut off the constant current charging and discharging circuit, enter the static cooling stage, prohibit charging and discharging again, and lock the charging and discharging cycle program of the battery cell. If the target warning level of the battery cell is level four, then at least one of the following protection strategies shall be executed: disconnect the main circuit relay, start the spray cooling system, push alarm information, control the battery cell to move to the explosion-proof fire extinguishing chamber, and lock the test channel of the battery cell.

6. The method for protecting against thermal runaway of a battery cell according to any one of claims 1-5, characterized in that, The temperature change rate includes a first temperature change rate, a second temperature change rate, and a third temperature change rate; The first temperature change rate is measured by a first temperature sensor located on the top of the explosion-proof valve of the battery cell; the second temperature change rate is measured by a second temperature sensor located in the middle of the steel shell of the battery cell; and the third temperature change rate is measured by a third temperature sensor located on the bottom negative electrode tab of the battery cell. The resistance change rate is obtained by detecting the voltage and charging / discharging current through sampling lines connected to the positive and negative terminals of the battery cell; The expansion deformation of the casing is obtained by measuring the distance at the middle of the side wall of the battery cell using a distance measuring sensor.

7. A protective device for thermal runaway of a battery cell, characterized in that, include: The acquisition module is used to acquire various monitoring parameters of the battery cell; each monitoring parameter includes at least one of the following: resistance change rate, temperature change rate, and casing expansion deformation. The early warning level determination module is used to determine the target early warning level of the battery cell from multiple early warning levels based on the monitoring parameters. The multi-level warning levels are multiple warning levels set sequentially according to the degree of thermal runaway of the battery cell; The protection execution module is used to execute the protection strategy corresponding to the target warning level based on the target warning level of the battery cell.

8. A main control unit, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 6.

9. A battery management system, characterized in that, include: The acquisition unit and the main control unit as described in claim 8; The acquisition unit is used to collect monitoring data of the battery cell during the charging and discharging process; The main control unit is used to obtain each of the monitoring parameters based on the monitoring data.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 6.

Images