A thermal propagation control system of a BBU lithium battery module

Abstract

The application provides a thermal propagation control system of a BBU lithium battery module, which comprises at least two sub-modules, the sub-modules comprise a plurality of parallelly arranged battery cells, the sub-modules are connected through a connecting mechanism, a thermistor is attached on the positive electrode lug of each battery cell through a heat-conducting adhesive, a voltage detection circuit comprises a multiplexing analog-to-digital converter, the analog-to-digital converter is used for collecting the voltage of each battery cell, a microcontroller collects the temperature and voltage at a fixed sampling period, a non-transient memory stores a lookup table, the lookup table associates the charging state, the discharging state and the standby state with corresponding threshold correction coefficients respectively, the threshold correction coefficients are 0.8-1.5, and a fire extinguishing actuator is arranged within 3-5 millimeters of the positive electrode lug of each battery cell, the thermal propagation control is realized through dynamic threshold matching and targeted execution, the intelligent control of the thermal propagation of the BBU lithium battery module is realized, and the identification accuracy and control matching degree are improved.

Description

Technical Field

[0001] This application relates to the field of lithium battery control technology, and more specifically, to a thermal propagation control system for a BBU lithium battery module. Background Technology

[0002] The BBU (Backup Battery Unit) lithium battery module is the main backup power source for base stations. Since BBU lithium battery modules consist of multiple individual cells connected in parallel, they present significant thermal safety risks. Traditional methods for assessing and controlling the thermal spread of BBU lithium battery modules primarily evaluate the heat dissipation of individual cells and employ passive isolation. These methods lack precise identification and targeted control, are susceptible to environmental changes, and lack the ability to predict early signs of thermal runaway. Traditional methods for preventing thermal runaway often involve module-level overall fire suppression, global power outages, or large-area isolation, which consume significant installation space within the module or involve excessive measures. Therefore, there is an urgent need for a control method that can achieve early prediction, precise intervention, and coordinated suppression of thermal runaway.

[0003] Effective technical solutions are urgently needed to address the above problems. Summary of the Invention

[0004] The purpose of this application is to provide a thermal spread control system for BBU lithium battery modules. This system can achieve intelligent control of thermal spread of BBU lithium battery modules by comprehensively judging voltage and temperature, dynamically matching thresholds, intelligently classifying early warning levels, and performing targeted thermal spread control, thereby improving the accuracy of identification and the degree of control matching.

[0005] The thermal propagation control system for the BBU lithium battery module provided in this application includes: At least two sub-modules, each sub-module comprising multiple cells arranged in parallel, and the sub-modules are connected to each other by a connecting mechanism; Thermistors are attached to the positive electrode tabs of each battery cell using thermally conductive adhesive. A voltage detection circuit, comprising a multiplexed analog-to-digital converter, which is used to acquire the voltage of each cell; A microcontroller that acquires temperature and voltage at a fixed sampling period; The non-transitory memory stores a lookup table that associates the charging state, discharging state, and standby state with the corresponding threshold correction coefficients, which range from 0.8 to 1.5. A fire extinguishing actuator, wherein the fire extinguishing actuator is disposed within 3-5 mm of the positive electrode tab of each battery cell; The microcontroller is used for: (a) Calculate the temperature rise rate of a single cell using two sets of continuous sampling data with a fixed sampling period; (b) Calculate the voltage deviation rate between cells; (c) Use the threshold correction coefficients obtained from the lookup table to generate the corrected temperature threshold and the corrected voltage threshold; (d) Determine whether the conditions for thermal runaway propagation have been triggered. (e) If the thermal runaway propagation condition is triggered, a control signal is output, the fuse connection mechanism is broken to achieve electrical isolation, and the fire extinguishing actuator is activated to release the fire extinguishing medium directly to the positive electrode tab.

[0006] Preferably, the connection mechanism is a fusible connecting wire, with adjacent cells in the same column connected in parallel by a single fusible connecting wire, and cells in the same row connected in series by at least three fusible connecting wires.

[0007] Preferably, the fusible connecting wire includes a copper core, which is coated with a low-melting-point alloy with a melting point of 130℃±10℃.

[0008] Preferably, the thickness of the thermally conductive adhesive is 0.1~0.5 mm. Preferably, the sampling period is 200 ms ± 20 ms. Preferably, the fire extinguishing actuator is a perfluorohexanone microcapsule that ruptures during operation, releasing the fire extinguishing medium directly to the positive electrode tab.

[0009] Preferably, the formula for calculating the temperature rise rate of a single battery cell is: (T2) T1) / ΔT; T1 is the temperature of the previous sampling period; T2 is the temperature of the next sampling period; ΔT is the time difference between the two temperature measurements. Preferably, the formula for calculating the inter-cell voltage deviation rate is: |Vcell Vavg| / Vavg; Vcell is the cell voltage value, and Vavg is the average voltage of all cells.

[0010] Preferably, the thermal runaway propagation conditions are as follows: The temperature rise rate is greater than or equal to 0.15±0.02, and the voltage deviation rate is greater than or equal to 0.08±0.01, and the above two conditions are sustained for at least 15 sampling cycles.

[0011] Preferably, the fusible connection mechanism provides electrical isolation from the moment thermal runaway propagation conditions are detected, and the fire extinguishing actuator is activated within 100 milliseconds ± 20 milliseconds.

[0012] Preferably, the non-transitory memory stores a preset threshold library and a heat spread control strategy library. The preset threshold library includes thresholds for single cell temperature rise warning, cell-to-cell voltage deviation warning, module total voltage fluctuation warning, and single cell voltage drop warning. The heat spread control strategy library includes low heat spread control strategies, medium heat spread control strategies, and high heat spread control strategies.

[0013] Preferably, the single cell temperature rise rate, cell-to-cell voltage deviation rate, module total voltage fluctuation rate, and single cell voltage drop rate are compared with the corresponding single cell temperature rise warning threshold, cell-to-cell voltage deviation warning threshold, module total voltage fluctuation warning threshold, and single cell voltage drop warning threshold to obtain a thermal propagation control strategy.

[0014] Preferably, the single-cell temperature rise warning threshold includes a first single-cell temperature rise warning threshold, a second single-cell temperature rise warning threshold, and a third single-cell temperature rise warning threshold. If the single cell temperature rise rate is less than the first single cell temperature rise warning threshold, the cell voltage deviation rate is less than the cell voltage deviation warning threshold, the single cell voltage drop rate is less than the single cell voltage drop warning threshold, and the module total voltage fluctuation rate is less than the module total voltage fluctuation warning threshold, then the heat spread prediction level is determined to be no heat spread. If the single cell temperature rise rate is greater than or equal to the first single cell temperature rise warning threshold and less than the second single cell temperature rise warning threshold, or the cell voltage deviation rate is greater than or equal to the cell voltage deviation warning threshold, then the heat spread prediction level is determined to be low heat spread. If the single cell temperature rise rate is greater than or equal to the second single cell temperature rise warning threshold and less than the third single cell temperature rise warning threshold, or the single cell voltage drop rate is greater than or equal to the single cell voltage drop warning threshold, then the heat spread prediction level is determined to be medium heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, or the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then the heat spread prediction level is determined to be high heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, and the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then a warning response is output.

[0015] As can be seen from the above, the thermal spread control system for the BBU lithium battery module provided in this application achieves intelligent control of thermal spread of the BBU lithium battery module by comprehensively judging voltage and temperature and dynamically matching thresholds, thereby improving the accuracy of identification and the degree of control matching.

[0016] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing embodiments of this application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the external structure of the thermal spread control system of the BBU lithium battery module provided in the embodiments of this application; Figure 2 This is a schematic diagram of the internal structure of the thermal spread control system of the BBU lithium battery module provided in the embodiments of this application; Figure 3 A schematic diagram of the cell distribution of the thermal spread control system of this BBU lithium battery module provided in the embodiments of this application; Figure 4 A flowchart illustrating the control method for the thermal spread control system of this BBU lithium battery module provided in an embodiment of this application; Figure 5 A flowchart illustrating the rate of change of operation monitoring when the thermal spread control system of the BBU lithium battery module provided in this application executes the control method; Figure 6 A flowchart illustrating the process of obtaining an operation monitoring and early warning optimization threshold when the thermal spread control system of the BBU lithium battery module provided in this embodiment of the application executes a control method; Figure 7 This is a high-level flowchart of the thermal propagation control system of a BBU lithium battery module, provided in an embodiment of this application, when executing a control method.

[0019] Figure 8 A block diagram of the thermal propagation control system for such a BBU lithium battery module provided in the embodiments of this application.

[0020] In the diagram, 1 is the outer isolator, 2 is the mounting fastener, 3 is the grid plate, 4 is the heat dissipation hole, 5 is the pressure relief hole, 6 is the heat-sensitive fire extinguishing mechanism, 7 is the inner isolator, 8 is the fire extinguishing box body, 9 is the battery cell, and 10 is the connecting mechanism. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0023] Please refer to Figures 1-3 The thermal propagation control system for a BBU lithium battery module disclosed in this embodiment includes an outer isolator 1 and an inner isolator 7. The inner spacer 7 is disposed inside the outer spacer 1, and one end of the inner spacer 7 is fixedly connected to the outer spacer 1; The other end of the inner isolator 7 is provided with a number of pressure relief holes 5, and the inner isolator 7 is provided with a fire extinguishing box 8 inside; The fire extinguishing box 8 contains several battery cells 9. Different battery cells 9 are electrically connected to each other through a connecting mechanism 10 in a preset manner. A heat-sensitive fire extinguishing mechanism 6 is provided at the positive terminal of any battery cell 9.

[0024] It should be noted that an air buffer layer is formed between the outer isolation component 1 and the inner isolation component 7, which can effectively block the heat from being transferred from the inside to the outside and prevent external fire sources from affecting the internal battery cell 9. When the battery cell 9 thermally runs away, a large amount of high-temperature and high-pressure gas will be generated instantly. The pressure relief hole 5 can release the high-temperature and high-pressure gas in a directional and controllable manner, avoiding the rapid increase in internal pressure that could lead to an explosion of the entire device, while also reducing the risk of flames shooting outward.

[0025] Specifically, the thermal extinguishing mechanism 6 includes a thermistor and an extinguishing actuator. The thermistor is attached to the positive electrode tab of each battery cell using a 0.1-0.5mm thick thermally conductive adhesive. The extinguishing actuator can be made of perfluorohexanone microcapsules, positioned within 3mm to 5mm of the positive electrode tab. During operation, the perfluorohexanone microcapsules rupture, releasing the extinguishing medium directly to the positive electrode tab. When the temperature of the battery cell 9 reaches a threshold (typically 120℃-180℃), the thermal extinguishing mechanism 6 automatically activates, releasing the extinguishing medium.

[0026] In this implementation, the heat-sensitive fire extinguishing mechanism 6 is placed close to the positive terminal of the battery cell 9 (the location where thermal runaway is most likely to occur), so it can accurately extinguish open flames in the early stages of a fire and nip the fire in the bud.

[0027] According to an embodiment of the present invention, the fire extinguishing box body 8 includes several sub-modules, each sub-module including multiple parallel-arranged battery cells 9, the battery cells 9 in adjacent sub-modules are arranged with the positive and negative poles reversed, and are connected in series through a connecting mechanism 10.

[0028] It should be noted that dividing a large number of battery cells 9 into multiple independent sub-modules, each of which is a relatively independent unit, can limit the fault to a single sub-module and prevent the spread of heat across sub-modules. The positive and negative poles of the battery cells 9 in adjacent sub-modules are arranged in opposite directions. This design not only makes the current path of the entire module shorter and more uniform, reducing local heat points, but also reduces the risk of electrical breakdown between adjacent sub-modules when a certain sub-module goes out of control.

[0029] According to an embodiment of the present invention, the connecting mechanism 10 is a fusible connecting wire. The preset method includes connecting the positive and negative poles of two adjacent sub-modules through a set of connecting mechanisms 10, connecting adjacent cells 9 in the same column in parallel through a single fusible connecting wire, and connecting cells 9 in the same row in series through at least three fusible connecting wires.

[0030] The fusible connector is designed with a copper core as the inner core, coated with a low-melting-point alloy with a melting point of 130℃±10℃. It will melt first when the temperature of cell 9 becomes too high.

[0031] Specifically, the cells 9 in the same column are connected in parallel with a single connecting wire. When a single cell 9 fails, only the parallel branch of that column will be cut off, without affecting the entire submodule.

[0032] Multiple connecting wires are used to connect the cells 9 in the same row, which can improve the redundancy of the circuit and prevent the entire module from losing power due to the accidental breakage of a single connecting wire.

[0033] The connecting wires that connect different sub-modules will melt first when the temperature of cell 9 is too high, completely cutting off the electrical connection between the faulty sub-module and other sub-modules, and preventing thermal runaway from being conducted through the circuit.

[0034] According to an embodiment of the present invention, the outer isolation member 1 is provided with a plurality of heat dissipation holes 4, a grid plate 3 is provided at one end of the outer isolation member 1, and a mounting fastener 2 is provided on one side of the grid plate 3.

[0035] It should be noted that the evenly distributed opening design can carry away the heat generated by the battery cell 9 in conjunction with the cooling airflow when the device is working normally, thus avoiding heat accumulation. The grid plate 3 further improves the heat dissipation efficiency at the end of the device while ensuring structural strength. The mounting fastener 2 allows the device to be quickly and securely installed on the rack of the BBU equipment, which is convenient for maintenance and replacement.

[0036] Reference Figure 8 The system disclosed in this embodiment also includes The voltage detection circuit includes a multiplexed analog-to-digital converter (ADC) used to acquire the voltage of each cell.

[0037] A microcontroller acquires temperature and voltage at a fixed sampling period; the sampling period is designed to be 200 ms ± 20 ms. The non-transitory memory stores a lookup table that associates the charging state, discharging state, and standby state with corresponding threshold correction coefficients, which range from 0.8 to 1.5.

[0038] The microcontroller is used for: (a) Calculate the temperature rise rate of a single cell using two sets of continuous sampling data with a fixed sampling period; (b) Calculate the voltage deviation rate between cells; (c) Use the threshold correction coefficients obtained from the lookup table to generate the corrected temperature threshold and the corrected voltage threshold; (d) Determine whether thermal runaway propagation conditions are triggered. If the temperature rise rate is greater than or equal to 0.15±0.02 and the voltage deviation rate is greater than or equal to 0.08±0.01, and the above two conditions are sustained for at least 15 sampling cycles, then thermal runaway propagation conditions are triggered.

[0039] (e) If the thermal runaway propagation condition is triggered, a control signal is output, the fusible connection mechanism achieves electrical isolation, and the fire extinguishing actuator is activated to directly release the extinguishing medium to the positive electrode tab. Furthermore, from the moment thermal runaway propagation conditions are detected, the fusible connection mechanism achieves electrical isolation, and the fire extinguishing actuator executes the action within 100 milliseconds ± 20 milliseconds.

[0040] The formula for calculating the temperature rise rate of a single battery cell is: (T2) T1) / ΔT; T1 is the temperature of the previous sampling period; T2 is the temperature of the next sampling period; ΔT is the time difference between the two temperature measurements.

[0041] The formula for calculating the voltage deviation rate between cells is: |Vcell Vavg| / Vavg; Vcell is the cell voltage value, and Vavg is the average voltage of all cells. Please refer to... Figure 4 , Figure 4 This is a flowchart illustrating a thermal spread control method for a BBU lithium battery system according to some embodiments of this application. This thermal spread control method for a BBU lithium battery module is used in terminal devices, such as computers and mobile phones. The system executes the thermal spread control method by including the following steps: S11. Obtain the working status characteristic data and operation monitoring data of the BBU lithium battery, process the operation monitoring data, and obtain the operation monitoring change rate. S12. Analyze and process the working status characteristic data in conjunction with the preset initial threshold for operation monitoring and early warning to obtain the optimized threshold for operation monitoring and early warning. S13. Compare the operation monitoring change rate with the operation monitoring early warning optimization threshold, and determine the heat spread prediction level based on the threshold comparison result. S14. Query the preset heat spread control strategy library according to the heat spread prediction level, obtain the corresponding heat spread control method, and perform heat spread control.

[0042] It should be noted that, in order to achieve accurate identification and precise control of thermal spread in BBU lithium batteries, firstly, temperature and voltage are monitored to assess the rate of change of temperature and voltage. Then, the comparison threshold is dynamically optimized based on the working state of the BBU lithium battery to make the judgment more accurate. Finally, a targeted thermal spread control strategy is obtained based on the predicted thermal spread level.

[0043] Please refer to Figure 5 , Figure 5 This is a flowchart illustrating the process of obtaining the rate of change of operation monitoring during the execution of a control method in a thermal propagation control system of a BBU lithium battery module according to some embodiments of this application. According to embodiments of the present invention, the step of acquiring the operating state characteristic data and operation monitoring data of the BBU lithium battery, and processing the operation monitoring data to obtain the rate of change of operation monitoring includes: S21. Obtain the working status characteristic data and operation monitoring data of the BBU lithium battery. The operation monitoring data includes single cell temperature, single cell voltage, total module voltage and average module cell voltage. S22. Process the single cell temperature, single cell voltage, total module voltage and average module cell voltage to obtain the operation monitoring change rate, which includes the single cell temperature rise rate, cell voltage deviation rate, total module voltage fluctuation rate and single cell voltage drop rate.

[0044] It should be noted that a miniature monitoring module is placed on top of the battery cell and fixed by a bracket matrix, which occupies little space. It is used to monitor voltage and temperature. The working state of the BBU lithium battery includes charging state, discharging state or standby state, and the working state characteristic data is represented by a unique identifier.

[0045] According to an embodiment of the present invention, the single cell temperature, single cell voltage, total module voltage, and average module cell voltage are processed to obtain the operational monitoring change rate. The operational monitoring change rate includes the single cell temperature rise rate, the inter-cell voltage deviation rate, the total module voltage fluctuation rate, and the single cell voltage drop rate, including: The temperature of a single battery cell is compared within a preset time period to obtain the temperature rise rate of the single battery cell. The voltage of a single cell and the average voltage of the cell in the module are compared to obtain the voltage deviation rate between cells. The total voltage of the module is compared within a preset time period to obtain the total voltage fluctuation rate of the module. The voltage of a single cell is compared within a preset time period to obtain the voltage drop rate of a single cell.

[0046] It should be noted that the single-cell temperature rise rate refers to the single-cell temperature at the next time point within a preset time period minus the single-cell temperature at the previous time point, and then divided by the single-cell temperature at the previous time point. If it is negative, it is recorded as 0. The inter-cell voltage deviation rate refers to the absolute value of the difference between the single-cell voltage and the average cell voltage of the module, and then divided by the average cell voltage of the module. The total module voltage fluctuation rate refers to the difference between the maximum and minimum total module voltages within a preset time period, and then divided by the average cell voltage of the module. The single-cell voltage drop rate refers to the single-cell voltage at the previous time point minus the single-cell voltage at the next time point within a preset time period, and then divided by the single-cell voltage at the previous time point. If it is positive, it means there is no voltage drop, and it is recorded as 0.

[0047] Please refer to Figure 6 , Figure 6 This is a flowchart illustrating the system execution control method for obtaining an optimized threshold for operation monitoring and early warning in some embodiments of this application. According to an embodiment of the present invention, the step of analyzing and processing the working state characteristic data in conjunction with a preset initial threshold for operation monitoring and early warning to obtain an optimized threshold for operation monitoring and early warning includes: S31. Based on the working status feature data, query the preset working status and early warning threshold correction coefficient mapping table to obtain the corresponding early warning threshold correction coefficient. S32. Based on the warning threshold correction coefficient and the preset operation monitoring warning initial threshold, the operation monitoring warning optimized threshold is obtained, including single cell temperature rise warning threshold, cell-to-cell voltage deviation warning threshold, module total voltage fluctuation warning threshold and single cell voltage drop warning threshold.

[0048] It should be noted that the degree of voltage and temperature fluctuation varies under different operating conditions. For example, the voltage fluctuation is relatively large when lithium batteries are charging. In order to avoid misjudgment, the warning threshold correction coefficient for single cell voltage drop rate was found to be 1.5. The single cell voltage drop warning threshold was optimized and adjusted from 0.1V to 0.15V. The mapping table between the preset operating conditions and the warning threshold correction coefficient was analyzed and constructed by those skilled in the art based on a large number of historical samples and can be dynamically adjusted according to specific applications.

[0049] According to an embodiment of the present invention, the step of comparing the rate of change of the operation monitoring with the operation monitoring early warning optimization threshold, and determining the heat spread prediction level based on the threshold comparison result, includes: The single cell temperature rise rate, cell-to-cell voltage deviation rate, module total voltage fluctuation rate, and single cell voltage drop rate are compared with the corresponding single cell temperature rise warning threshold, cell-to-cell voltage deviation warning threshold, module total voltage fluctuation warning threshold, and single cell voltage drop warning threshold to obtain the thermal spread prediction level. The single-cell temperature rise warning threshold includes a first single-cell temperature rise warning threshold, a second single-cell temperature rise warning threshold, and a third single-cell temperature rise warning threshold. If the single cell temperature rise rate is less than the first single cell temperature rise warning threshold, the cell voltage deviation rate is less than the cell voltage deviation warning threshold, the single cell voltage drop rate is less than the single cell voltage drop warning threshold, and the module total voltage fluctuation rate is less than the module total voltage fluctuation warning threshold, then the heat spread prediction level is determined to be no heat spread. If the single cell temperature rise rate is greater than or equal to the first single cell temperature rise warning threshold and less than the second single cell temperature rise warning threshold, or the cell voltage deviation rate is greater than or equal to the cell voltage deviation warning threshold, then the heat spread prediction level is determined to be low heat spread. If the single cell temperature rise rate is greater than or equal to the second single cell temperature rise warning threshold and less than the third single cell temperature rise warning threshold, or the single cell voltage drop rate is greater than or equal to the single cell voltage drop warning threshold, then the heat spread prediction level is determined to be medium heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, or the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then the heat spread prediction level is determined to be high heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, and the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then a warning response is output.

[0050] It should be noted that, in order to prevent misjudgment or omission of thermal spread in lithium batteries, a dual-layer threshold comparison judgment of temperature and voltage is performed. The first single-cell temperature rise warning threshold is lower than the second single-cell temperature rise warning threshold, and the second single-cell temperature rise warning threshold is lower than the third single-cell temperature rise warning threshold. When a warning is triggered, it indicates that the judgment of temperature and voltage is mismatched, and further identification by technicians is required.

[0051] According to an embodiment of the present invention, the step of determining the heat spread prediction level based on the threshold comparison result further includes: Obtain the duration of the warning indicating whether the heat spread is low-grade, medium-grade, or high-grade; The warning duration is compared with a preset warning duration threshold. If the duration of the warning is less than the preset warning duration threshold, then the low heat spread, medium heat spread or high heat spread is determined to be an invalid warning; If the duration of the warning is greater than or equal to the preset warning duration threshold, then low heat spread, medium heat spread, or high heat spread is determined to be a valid warning.

[0052] It should be noted that, in order to prevent misjudgment caused by instantaneous fluctuations, after determining whether the heat spread is low-temperature, medium-temperature, or high-temperature, the duration of the warning is statistically analyzed and the threshold is compared to determine whether the warning is effective.

[0053] According to an embodiment of the present invention, the step of querying a preset heat spread control strategy library based on the heat spread prediction level to obtain the corresponding heat spread control method and performing heat spread control includes: Based on the low heat spread, medium heat spread, or high heat spread, query the preset heat spread control strategy library to obtain the corresponding heat spread control method, including low heat spread control strategy, medium heat spread control strategy, or high heat spread control strategy. Thermal spread control is performed according to the low thermal spread control strategy, medium thermal spread control strategy, or high thermal spread control strategy.

[0054] It should be noted that the early warning system, based on both voltage and temperature, indicates the following: low thermal spread corresponds to abnormal heat generation with no immediate risk of thermal runaway; medium thermal spread indicates a precursor to thermal runaway; and high thermal spread indicates that thermal runaway has already occurred and requires timely intervention and emergency response. In this embodiment, the low thermal spread control strategy switches the adaptive thermal insulation layer to a heat dissipation mode, whereby the heat generated by the battery cell is conducted to the aluminum alloy casing of the module through the honeycomb thermal conductive frame, allowing for natural heat dissipation into the working environment, or simultaneously cooled by a pneumatically driven built-in micro cooling fan. The medium thermal spread control strategy involves disconnecting the electrical connections between the thermally runaway individual battery cell and other battery cells. To prevent the mutual charging effect between battery cells from exacerbating thermal runaway, a PTC material is used. When the material temperature rises to 120°C, the material resistance instantly increases from ≤5mΩ to over 1kΩ, thus cutting off the charging and discharging circuit of the thermally runaway battery cell. The high heat spread control strategy achieves rapid fire extinguishing and cooling, and exhausts the gas generated by heat spread. For example, the temperature of the heating wire instantly rises to about 200°C, melting the perfluorohexanone microcapsule for precise fire extinguishing. At the same time, the temperature rise causes the expandable graphite to expand rapidly and fill the gaps in the honeycomb thermally conductive skeleton, forming a dense heat insulation layer. The harmful gas is then exhausted by a negative pressure fan.

[0055] Please refer to Figure 7 , Figure 7 This is a high-level flowchart of the system control method in some embodiments of this application.

[0056] It is worth mentioning that, according to embodiments of the present invention, it further includes: S41. If it is determined that the single cell is experiencing moderate heat propagation, the single cell temperature rise warning threshold and the inter-cell voltage deviation warning threshold are corrected according to the preset descent gradient to obtain the single cell temperature rise warning correction threshold and the inter-cell voltage deviation warning correction threshold. S42. Compare the single cell temperature rise rate and inter-cell voltage deviation rate of adjacent cells with the corresponding single cell temperature rise warning correction threshold and inter-cell voltage deviation warning correction threshold. S43. If the temperature rise rate of a single cell in an adjacent cell is less than the temperature rise warning correction threshold for a single cell, and the voltage deviation rate between cells is less than the voltage deviation warning correction threshold between cells, then no action is taken. S44. Conversely, if the adjacent cell is determined to be of low predicted thermal spread, the corresponding predicted low thermal spread control method is obtained by querying the preset thermal spread control strategy library based on the predicted low thermal spread.

[0057] It should be noted that, in order to achieve predictive protection for adjacent cells, when a cell is determined to be in a state of medium heat spread, the corresponding threshold is adjusted downward again according to the preset gradient. The temperature rise rate of a single cell and the voltage deviation rate between cells of adjacent cells are compared with the threshold. If either exceeds the threshold, it is determined to be a predicted low heat spread, and it is about to enter the low heat spread stage. The predictive low heat spread control method is to put the adaptive heat insulation layer into a semi-isolation mode in advance, such as increasing the thickness by 1mm. This will not affect the normal heat dissipation of adjacent cells, but can quickly respond to subsequent isolation requirements.

[0058] This invention also discloses a thermal spread control system for a BBU lithium battery module, including a memory and a processor. The memory stores a program for a thermal spread control method for a BBU lithium battery module. When the processor executes the program for the thermal spread control method of the BBU lithium battery module, it performs the following steps: Acquire the working status characteristic data and operation monitoring data of the BBU lithium battery, process the operation monitoring data, and obtain the operation monitoring change rate; Based on the working status characteristic data and the preset initial threshold for operation monitoring and early warning, the optimized threshold for operation monitoring and early warning is obtained through analysis and processing. The rate of change in the operation monitoring is compared with the optimization threshold for early warning of the operation monitoring, and the heat spread prediction level is determined based on the threshold comparison result. Based on the predicted heat spread level, the system queries the preset heat spread control strategy library to obtain the corresponding heat spread control method and performs heat spread control.

[0059] It should be noted that, in order to accurately identify and precisely control the thermal spread of BBU lithium batteries, firstly, temperature and voltage are monitored and their rate of change is evaluated. Then, the comparison threshold is dynamically optimized based on the working state of the BBU lithium battery to make the judgment more accurate. Finally, a targeted thermal spread control strategy is obtained based on the predicted thermal spread level.

[0060] According to an embodiment of the present invention, the step of acquiring the operating state characteristic data and operation monitoring data of the BBU lithium battery, and processing the operation monitoring data to obtain the operation monitoring change rate includes: Acquire the working status characteristic data and operation monitoring data of BBU lithium battery. The operation monitoring data includes single cell temperature, single cell voltage, total module voltage and average cell voltage of module. The operating monitoring change rate is obtained by processing the individual cell temperature, individual cell voltage, total module voltage, and average cell voltage of the module. The operating monitoring change rate includes the individual cell temperature rise rate, cell-to-cell voltage deviation rate, total module voltage fluctuation rate, and individual cell voltage drop rate.

[0061] It should be noted that a miniature monitoring module is placed on top of the battery cell and fixed by a bracket matrix, which occupies little space. It is used to monitor voltage and temperature. The working state of the BBU lithium battery includes charging state, discharging state or standby state, and the working state characteristic data is represented by a unique identifier.

[0062] According to an embodiment of the present invention, the process of processing the single cell temperature, single cell voltage, and average cell voltage of the module to obtain the operation monitoring change rate includes the single cell temperature rise rate, the inter-cell voltage deviation rate, the total module voltage fluctuation rate, and the single cell voltage drop rate, including: The temperature of a single battery cell is compared within a preset time period to obtain the temperature rise rate of the single battery cell. The voltage of a single cell and the average voltage of the cell in the module are compared to obtain the voltage deviation rate between cells. The total voltage of the module is compared within a preset time period to obtain the total voltage fluctuation rate of the module. The voltage of a single cell is compared within a preset time period to obtain the voltage drop rate of a single cell.

[0063] It should be noted that the single-cell temperature rise rate refers to the single-cell temperature at the next time point within a preset time period minus the single-cell temperature at the previous time point, and then divided by the single-cell temperature at the previous time point. If it is negative, it is recorded as 0. The inter-cell voltage deviation rate refers to the absolute value of the difference between the single-cell voltage and the average cell voltage of the module, and then divided by the average cell voltage of the module. The total module voltage fluctuation rate refers to the difference between the maximum and minimum total module voltages within a preset time period, and then divided by the average cell voltage of the module. The single-cell voltage drop rate refers to the single-cell voltage at the previous time point minus the single-cell voltage at the next time point within a preset time period, and then divided by the single-cell voltage at the previous time point. If it is positive, it means there is no voltage drop, and it is recorded as 0.

[0064] According to an embodiment of the present invention, the step of analyzing and processing the working status feature data in conjunction with a preset initial threshold for operation monitoring and early warning to obtain an optimized threshold for operation monitoring and early warning includes: Based on the working status feature data, query the preset working status and early warning threshold correction coefficient mapping table to obtain the corresponding early warning threshold correction coefficient; The operation monitoring and early warning optimized thresholds are obtained by combining the early warning threshold correction coefficient with the preset operation monitoring early warning initial threshold. These include single cell temperature rise early warning threshold, cell-to-cell voltage deviation early warning threshold, module total voltage fluctuation early warning threshold, and single cell voltage drop early warning threshold.

[0065] It should be noted that the degree of voltage and temperature fluctuation varies under different operating conditions. For example, the voltage fluctuation is relatively large when lithium batteries are charging. In order to avoid misjudgment, the warning threshold correction coefficient for single cell voltage drop rate was found to be 1.5. The single cell voltage drop warning threshold was optimized and adjusted from 0.1V to 0.15V. The mapping table between the preset operating conditions and the warning threshold correction coefficient was analyzed and constructed by those skilled in the art based on a large number of historical samples and can be dynamically adjusted according to specific applications.

[0066] According to an embodiment of the present invention, the step of comparing the rate of change of the operation monitoring with the operation monitoring early warning optimization threshold, and determining the heat spread prediction level based on the threshold comparison result, includes: The single cell temperature rise rate, cell-to-cell voltage deviation rate, module total voltage fluctuation rate, and single cell voltage drop rate are compared with the corresponding single cell temperature rise warning threshold, cell-to-cell voltage deviation warning threshold, module total voltage fluctuation warning threshold, and single cell voltage drop warning threshold to obtain the thermal spread prediction level. The single-cell temperature rise warning threshold includes a first single-cell temperature rise warning threshold, a second single-cell temperature rise warning threshold, and a third single-cell temperature rise warning threshold. If the single cell temperature rise rate is less than the first single cell temperature rise warning threshold, the cell voltage deviation rate is less than the cell voltage deviation warning threshold, the single cell voltage drop rate is less than the single cell voltage drop warning threshold, and the module total voltage fluctuation rate is less than the module total voltage fluctuation warning threshold, then the heat spread prediction level is determined to be no heat spread. If the single cell temperature rise rate is greater than or equal to the first single cell temperature rise warning threshold and less than the second single cell temperature rise warning threshold, or the cell voltage deviation rate is greater than or equal to the cell voltage deviation warning threshold, then the heat spread prediction level is determined to be low heat spread. If the single cell temperature rise rate is greater than or equal to the second single cell temperature rise warning threshold and less than the third single cell temperature rise warning threshold, or the single cell voltage drop rate is greater than or equal to the single cell voltage drop warning threshold, then the heat spread prediction level is determined to be medium heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, or the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then the heat spread prediction level is determined to be high heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, and the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then a warning response is output.

[0067] It should be noted that, in order to prevent misjudgment or omission of thermal spread in lithium batteries, a dual-layer threshold comparison judgment of temperature and voltage is performed. The first single-cell temperature rise warning threshold is lower than the second single-cell temperature rise warning threshold, and the second single-cell temperature rise warning threshold is lower than the third single-cell temperature rise warning threshold. When a warning is triggered, it indicates that the judgment of temperature and voltage is mismatched, and further identification by technicians is required.

[0068] According to an embodiment of the present invention, the step of determining the heat spread prediction level based on the threshold comparison result further includes: Obtain the duration of the warning indicating whether the heat spread is low-grade, medium-grade, or high-grade; The warning duration is compared with a preset warning duration threshold. If the duration of the warning is less than the preset warning duration threshold, then the low heat spread, medium heat spread or high heat spread is determined to be an invalid warning; If the duration of the warning is greater than or equal to the preset warning duration threshold, then low heat spread, medium heat spread, or high heat spread is determined to be a valid warning.

[0069] It should be noted that, in order to prevent misjudgment caused by instantaneous fluctuations, after determining whether the heat spread is low-temperature, medium-temperature, or high-temperature, the duration of the warning is statistically analyzed and the threshold is compared to determine whether the warning is effective.

[0070] According to an embodiment of the present invention, the step of querying a preset heat spread control strategy library based on the heat spread prediction level to obtain the corresponding heat spread control method and performing heat spread control includes: Based on the low heat spread, medium heat spread, or high heat spread, query the preset heat spread control strategy library to obtain the corresponding heat spread control method, including low heat spread control strategy, medium heat spread control strategy, or high heat spread control strategy. Thermal spread control is performed according to the low thermal spread control strategy, medium thermal spread control strategy, or high thermal spread control strategy.

[0071] It should be noted that the early warning system, based on both voltage and temperature, indicates the following: low thermal spread corresponds to abnormal heat generation with no immediate risk of thermal runaway; medium thermal spread indicates a precursor to thermal runaway; and high thermal spread indicates that thermal runaway has already occurred and requires timely intervention and emergency response. In this embodiment, the low thermal spread control strategy switches the adaptive thermal insulation layer to a heat dissipation mode, whereby the heat generated by the battery cell is conducted to the aluminum alloy casing of the module through the honeycomb thermal conductive frame, allowing for natural heat dissipation into the working environment, or simultaneously cooled by a pneumatically driven built-in micro cooling fan. The medium thermal spread control strategy involves disconnecting the electrical connections between the thermally runaway individual battery cell and other battery cells. To prevent the mutual charging effect between battery cells from exacerbating thermal runaway, a PTC material is used. When the material temperature rises to 120°C, the material resistance instantly increases from ≤5mΩ to over 1kΩ, thus cutting off the charging and discharging circuit of the thermally runaway battery cell. The high heat spread control strategy achieves rapid fire extinguishing and cooling, and exhausts the gas generated by heat spread. For example, the temperature of the heating wire instantly rises to about 200°C, melting the perfluorohexanone microcapsule for precise fire extinguishing. At the same time, the temperature rise causes the expandable graphite to expand rapidly and fill the gaps in the honeycomb thermally conductive skeleton, forming a dense heat insulation layer. The harmful gas is then exhausted by a negative pressure fan.

[0072] It is worth mentioning that, according to embodiments of the present invention, it further includes: If it is determined that the single cell is experiencing moderate heat propagation, the single cell temperature rise warning threshold and the inter-cell voltage deviation warning threshold are corrected according to the preset descent gradient to obtain the single cell temperature rise warning correction threshold and the inter-cell voltage deviation warning correction threshold. The single-cell temperature rise rate and inter-cell voltage deviation rate of adjacent cells are compared with the corresponding single-cell temperature rise warning correction threshold and inter-cell voltage deviation warning correction threshold. If the temperature rise rate of a single cell in an adjacent cell is less than the temperature rise warning correction threshold for a single cell, and the voltage deviation rate between cells is less than the voltage deviation warning correction threshold between cells, then no action is taken. Conversely, if the adjacent cell is determined to be of low predicted thermal spread, the corresponding predicted low thermal spread control method is obtained by querying the preset thermal spread control strategy library based on the predicted low thermal spread.

[0073] It should be noted that, in order to achieve predictive protection for adjacent cells, when a cell is determined to be in a state of medium heat spread, the corresponding threshold is adjusted downward again according to a preset gradient. The temperature rise rate of a single cell and the voltage deviation rate between cells of adjacent cells are compared with the threshold. If either exceeds the threshold, it is determined to be a predicted low heat spread, and the cell is about to enter a low heat spread state. The predictive low heat spread control method is to put the adaptive thermal insulation layer into a semi-isolation mode in advance. For example, the expandable graphite is slightly expanded, and the thickness is increased to 1mm. This does not affect the normal heat dissipation of adjacent cells and can quickly respond to subsequent isolation requirements.

[0074] The present invention provides a readable storage medium storing a thermal spread control method program for a BBU lithium battery module. When the thermal spread control method program for a BBU lithium battery module is executed by a processor, it implements the steps of the thermal spread control method for a BBU lithium battery module as described in any of the preceding claims.

[0075] The thermal spread control system for a BBU lithium battery module disclosed in this invention achieves intelligent control of thermal spread in the BBU lithium battery module by comprehensively judging voltage and temperature, dynamic threshold matching, intelligent early warning level classification, and targeted execution of thermal spread control, thereby improving the accuracy of identification and the degree of control matching.

[0076] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0077] 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. They may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0078] In addition, in the various embodiments of the present invention, each functional unit can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0079] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0080] Alternatively, if the integrated units of this invention are implemented as software functional modules and sold or used as independent products, they can also be stored in a readable storage medium. Based on this understanding, the technical solutions of the embodiments of this invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROM, RAM, magnetic disks, or optical disks.

Claims

1. A thermal propagation control system for a BBU lithium battery module, characterized in that, The system includes: At least two sub-modules, each sub-module comprising multiple cells arranged in parallel, and the sub-modules are connected to each other by a connecting mechanism; Thermistors are attached to the positive electrode tabs of each battery cell using thermally conductive adhesive. A voltage detection circuit, comprising a multiplexed analog-to-digital converter, which is used to acquire the voltage of each cell; A microcontroller that acquires temperature and voltage at a fixed sampling period; The non-transitory memory stores a lookup table that associates the charging state, discharging state, and standby state with the corresponding threshold correction coefficients, which range from 0.8 to 1.

5. A fire extinguishing actuator, wherein the fire extinguishing actuator is disposed within 3-5 mm of the positive electrode tab of each battery cell; The microcontroller is used for: (a) Calculate the temperature rise rate of a single cell using two sets of continuous sampling data with a fixed sampling period; (b) Calculate the voltage deviation rate between cells; (c) Use the threshold correction coefficients obtained from the lookup table to generate the corrected temperature threshold and the corrected voltage threshold; (d) Determine whether the conditions for thermal runaway propagation have been triggered. (e) If the thermal runaway propagation condition is triggered, a control signal is output, the fuse connection mechanism is broken to achieve electrical isolation, and the fire extinguishing actuator is activated to release the fire extinguishing medium directly to the positive electrode tab.

2. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The connection mechanism is a fusible connecting wire. Adjacent cells in the same column are connected in parallel by a single fusible connecting wire, and cells in the same row are connected in series by at least three fusible connecting wires.

3. The thermal propagation control system for the BBU lithium battery module according to claim 2, characterized in that: The fusible connecting wire includes a copper core, which is coated with a low-melting-point alloy with a melting point of 130℃±10℃.

4. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The thickness of the thermally conductive adhesive is 0.1~0.5 mm.

5. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The sampling period is 200 ms ± 20 ms.

6. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The fire extinguishing actuator is a perfluorohexanone microcapsule. When in operation, the perfluorohexanone microcapsule ruptures, releasing the fire extinguishing medium directly to the positive electrode tab.

7. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The formula for calculating the temperature rise rate of a single battery cell is: (T2) T1) / ΔT; T1 is the temperature of the previous sampling period; T2 is the temperature of the next sampling period; ΔT is the time difference between the two temperature measurements.

8. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The formula for calculating the voltage deviation rate between battery cells is: |Vcell Vavg| / Vavg; Vcell is the cell voltage value, and Vavg is the average voltage of all cells.

9. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The conditions for the propagation of thermal runaway are: The temperature rise rate is greater than or equal to 0.15±0.02, and the voltage deviation rate is greater than or equal to 0.08±0.01, and the above two conditions are sustained for at least 15 sampling cycles.

10. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: Once thermal runaway propagation conditions are detected, the fusible connection mechanism provides electrical isolation, and the fire extinguishing actuator is activated within 100 milliseconds ± 20 milliseconds.

11. The thermal propagation control system for the BBU lithium battery module according to claim 1, characterized in that: The non-transitory memory stores a preset threshold library and a heat spread control strategy library. The preset threshold library includes warning thresholds for single cell temperature rise, cell-to-cell voltage deviation, module total voltage fluctuation, and single cell voltage drop. The heat spread control strategy library includes low heat spread control strategies, medium heat spread control strategies, and high heat spread control strategies.

12. The thermal propagation control system for the BBU lithium battery module according to claim 11, characterized in that: The single-cell temperature rise rate, inter-cell voltage deviation rate, total module voltage fluctuation rate, and single-cell voltage drop rate are compared with the corresponding single-cell temperature rise warning threshold, inter-cell voltage deviation warning threshold, total module voltage fluctuation warning threshold, and single-cell voltage drop warning threshold to obtain a thermal propagation control strategy.

13. The thermal propagation control system for the BBU lithium battery module according to claim 12, characterized in that: The single-cell temperature rise warning threshold includes a first single-cell temperature rise warning threshold, a second single-cell temperature rise warning threshold, and a third single-cell temperature rise warning threshold. If the single cell temperature rise rate is less than the first single cell temperature rise warning threshold, the cell voltage deviation rate is less than the cell voltage deviation warning threshold, the single cell voltage drop rate is less than the single cell voltage drop warning threshold, and the module total voltage fluctuation rate is less than the module total voltage fluctuation warning threshold, then the heat spread prediction level is determined to be no heat spread. If the single cell temperature rise rate is greater than or equal to the first single cell temperature rise warning threshold and less than the second single cell temperature rise warning threshold, or the cell voltage deviation rate is greater than or equal to the cell voltage deviation warning threshold, then the heat spread prediction level is determined to be low heat spread. If the single cell temperature rise rate is greater than or equal to the second single cell temperature rise warning threshold and less than the third single cell temperature rise warning threshold, or the single cell voltage drop rate is greater than or equal to the single cell voltage drop warning threshold, then the heat spread prediction level is determined to be medium heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, or the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then the heat spread prediction level is determined to be high heat spread. If the temperature rise rate of the single cell is greater than or equal to the third single cell temperature rise warning threshold, and the total voltage fluctuation rate of the module is greater than or equal to the total voltage fluctuation warning threshold of the module, then a warning response is output.

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