Battery pack and thermal management control method thereof

Abstract

The application discloses a battery pack and a thermal management control method thereof. The battery pack comprises a box body, a plurality of battery cells, a cooling circulation system, a plurality of overflow ports, an information acquisition module and a controller. The bottom of the box body is formed with an immersion cavity. The battery cells are arranged in the box body, and the explosion-proof valves of the battery cells face downward and are directed to the immersion cavity. The cooling circulation system comprises a main circulating pump and a local flow control valve group corresponding to each battery cell. The overflow ports are respectively arranged below the explosion-proof valves of the battery cells and are communicated with the cooling circulation system. The information acquisition module comprises a temperature acquisition unit and a pressure fluctuation acquisition unit. The controller determines the thermal runaway evolution stage according to the temperature rise rate of the battery cells and the characteristic of the impact pressure wave in the cooling circulation system, and controls the rotating speed of the main circulating pump and the opening degree of the valve group. In the first mode, the pump is operated at a first rotating speed, and the valve group is closed. In the second mode, the pump is operated at a second rotating speed greater than the first rotating speed, and the valve group corresponding to the abnormal battery cell is opened, so that the cooling medium impacts the explosion-proof valve through the overflow port. The application greatly reduces the thermal runaway probability and the system energy consumption.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for energy storage batteries, and in particular to a battery pack and its thermal management control method. Background Technology

[0002] With the continuous improvement of cell energy density and the increasing capacity of energy storage systems, thermal management has become a key technical bottleneck restricting the safety and economy of lithium-ion battery energy storage systems.

[0003] Currently, immersion liquid cooling technology is gradually becoming an important development direction for thermal management of energy storage batteries due to its excellent heat exchange capacity and safety performance. Among existing immersion battery packs and their thermal management solutions, the following are some typical examples:

[0004] Firstly, the integrated cooling and fire protection cell-inverted energy storage box disclosed in CN223390628U employs an inverted cell structure. It utilizes a liquid accumulation chamber at the bottom of the box to immerse the explosion-proof valves and tabs on top of the cells, and sets guide strips between adjacent cells to form heat dissipation channels. Coolant flows through these channels to cool the sides of the cells. While this solution achieves partial immersion and cooling, its channel structure is complex, assembly is difficult, and it relies heavily on bottom liquid level control to ensure immersion effectiveness. Fluctuations in the liquid level may expose the tops of some cells, posing a risk of thermal runaway.

[0005] Secondly, as disclosed in CN222720506U, a novel submerged energy storage cooling module employs a fully submerged approach, placing the inverted battery cells completely within a tank filled with insulating oil, and installing a water-cooled plate on top of the tank for heat exchange. While this solution offers good sealing, it requires filling a large amount of expensive insulating coolant, resulting in high system cost and weight. Furthermore, heat must be conducted from the bottom battery cells to the top oil layer and then carried away by the water-cooled plate, resulting in a long heat transfer path, poor temperature uniformity, and difficulty in meeting the rapid heat dissipation requirements under high-rate charging and discharging conditions.

[0006] Third, as disclosed in CN115377591A, a battery pack with inverted cells and its assembly method mainly focuses on the mechanical fixing and assembly process after the cells are inverted. The cells are installed in reverse through specific brackets and clamping structures, but it does not involve efficient liquid cooling or immersion cooling structures. It mainly relies on air cooling or natural heat dissipation, which cannot meet the strict requirements of high-power energy storage systems for thermal management.

[0007] The aforementioned existing technologies generally employ a "static" or "integral" circulation strategy—the coolant flow rate and flow channel distribution remain unchanged under normal and abnormal operating conditions, and thermal management triggering is based on a fixed temperature threshold (e.g., 60°C). This single thermal management strategy has the following shortcomings:

[0008] First, the system cannot distinguish between the "early warning period" and the "out-of-control period." When individual cells show early abnormal temperature rise, it can only passively wait for the temperature to continue to rise or for thermal runaway to occur before activating the fire suppression system, thus missing the window for proactive intervention. The triggering mechanism, based on a fixed temperature threshold, may already show irreversible heat accumulation inside the cell when the temperature exceeds the limit, lacking predictive triggering capabilities based on early, weak signals such as temperature rise rate and pressure waves.

[0009] Secondly, in the global circulation mode, the pump group operates at constant power, and the power consumption of the thermal management subsystem accounts for 30% to 50% of the total power consumption of the auxiliary system, resulting in serious energy waste.

[0010] Furthermore, after thermal runaway occurs, existing solutions rely solely on explosion-proof valves for pressure relief and passive immersion, failing to actively alter the coolant flow pattern and flow rate to accelerate the quenching of the runaway battery cell. Additionally, high-temperature gas often mixes with coolant during ejection, posing a risk of secondary ignition. Summary of the Invention

[0011] To address the problems of existing immersion battery packs having a single thermal management strategy, being unable to proactively intervene in stages according to the evolution of thermal runaway, resulting in delayed response, high energy consumption, and susceptibility to secondary disasters, this invention proposes a battery pack and its thermal management control method.

[0012] The specific technical solution is as follows: A battery pack, comprising:

[0013] The housing has an immersion chamber at its bottom for containing the cooling medium;

[0014] Multiple battery cells are disposed inside the enclosure, with the explosion-proof valve of each battery cell facing downwards and toward the immersion chamber;

[0015] A cooling circulation system is connected to the immersion chamber. The cooling circulation system includes a main circulation pump and multiple local flow control valve groups, each of which is correspondingly set to each of the battery cells.

[0016] Multiple overflow ports are respectively located below the explosion-proof valve of each of the battery cells, and each of the overflow ports is connected to the cooling circulation system.

[0017] The information acquisition module includes at least a temperature acquisition unit and a pressure fluctuation acquisition unit installed in the cooling circulation system;

[0018] The controller is electrically connected to the information acquisition module, the main circulation pump, and each of the local flow control valve groups. The controller is configured to:

[0019] The temperature rise rate of each cell is calculated based on the collected temperature, and the collected pressure fluctuation signal is processed to extract the characteristics of the impact pressure wave.

[0020] The thermal runaway evolution stage is determined by combining the temperature rise rate and the characteristics of the shock pressure wave.

[0021] Controlling the rotational speed of the main circulation pump and the opening degree of the local flow control valve assembly according to the thermal runaway evolution stage includes at least:

[0022] In the first mode, the main circulation pump operates at a first speed, and each of the local flow control valve groups is closed;

[0023] In the second mode, the main circulation pump operates at a second speed greater than the first speed, and the local flow control valve group corresponding to the abnormal cell is opened, so that the cooling medium impacts the explosion-proof valve through the overflow port.

[0024] Furthermore, the thermal runaway evolution stage also includes a runaway stage;

[0025] The controller executes a third mode during the runaway phase: the main circulation pump operates at a third speed, which is 120% to 150% of the rated speed of the main circulation pump, and the abnormal battery cell and the local flow control valve group in the area adjacent to the abnormal battery cell are opened, so that the cooling medium completely submerges the abnormal battery cell and forms a liquid wall for isolation in the adjacent area.

[0026] Furthermore, when the abnormal cell temperature drops below a preset safe temperature threshold and there is no open flame, the controller executes a fourth mode: the main circulation pump operates at a fourth speed between the first speed and the second speed, and the local flow control valve group gradually closes.

[0027] Furthermore, each of the overflow ports is located directly below the corresponding explosion-proof valve, and the vertical distance between the overflow port and the explosion-proof valve is 10mm~20mm;

[0028] In the second mode, the controller controls the local flow control valve group to open and close in a pulse manner, so that the cooling medium pulses and impacts the explosion-proof valve area.

[0029] Furthermore, the bottom of the housing is also provided with an exhaust guide pipe and a pressure relief valve. One end of the exhaust guide pipe is connected to the upper space inside the housing, and the other end is connected to the pressure relief valve.

[0030] The exhaust guide pipe has a gas-liquid separation structure at one end inside the housing. The gas-liquid separation structure has a side air intake channel. Gas enters the exhaust guide pipe through the side air intake channel. The gas-liquid separation structure blocks liquid and solid particles from passing through.

[0031] Furthermore, the gas-liquid separation structure includes an upper umbrella-shaped baffle and a lower umbrella-shaped baffle arranged coaxially, both of which are arranged downwards, with a side air intake gap between them.

[0032] Furthermore, the immersion chamber is provided with a cell limiting boss, and each cell is fixed upright on the limiting boss, with the positive and negative terminals of each cell facing upwards; foam is provided between adjacent cells, and the expansion of the foam helps to fix the cells; the natural gap between adjacent cells forms a branch flow channel, and each overflow port is connected to the cooling circulation system through the branch flow channel.

[0033] Furthermore, the bottom of the housing is also integrated with an independent liquid cooling plate, and the battery pack also includes a coolant circuit independent of the cooling circulation system;

[0034] In the first mode, the controller only activates the coolant circuit; in the second or third mode, it simultaneously activates the coolant circuit and the cooling circulation system for coordinated cooling.

[0035] A battery pack thermal management control method, comprising:

[0036] Real-time acquisition of temperature of each battery cell and pressure fluctuation signals in the cooling circulation system;

[0037] The temperature rise rate of each cell is calculated, and the pressure fluctuation signal is processed to extract the characteristics of the impact pressure wave.

[0038] The current thermal runaway evolution stage is determined by combining the temperature rise rate and the characteristics of the shock pressure wave. The thermal runaway evolution stage includes at least a normal stage and a warning stage.

[0039] If the condition is determined to be in the normal phase, the cooling circulation system is controlled to operate at the first flow rate, and each local valve group is closed.

[0040] If the warning stage is determined, the cooling circulation system is controlled to operate at a second flow rate greater than the first flow rate, and the local valve group corresponding to the abnormal cell is opened, so that the cooling medium impacts the explosion-proof valve area of ​​the abnormal cell through the overflow port.

[0041] Furthermore, bandpass filtering and envelope analysis are performed on the pressure fluctuation signal to extract the characteristics of the impact pressure wave;

[0042] The sampling frequency of the pressure fluctuation signal is ≥100Hz, and the characteristic frequency of the impact pressure wave is 1kHz~10kHz.

[0043] The thermal runaway evolution stage also includes a runaway stage and a post-processing stage;

[0044] The determination of the runaway stage is also based on the voltage collapse rate, which is calculated based on the real-time collected voltage of each cell.

[0045] If the system is determined to be in the out-of-control stage, the cooling circulation system is controlled to operate at a third flow rate greater than the second flow rate, and the local valve group of the abnormal cell and the adjacent area is opened to temporarily and completely submerge the abnormal cell in the cooling medium.

[0046] If the process is determined to be in the post-processing stage, the cooling circulation system is controlled to operate at a fourth flow rate between the first flow rate and the second flow rate until the abnormal cell temperature drops below the safety threshold.

[0047] The above technical solution has the following advantages or technical effects:

[0048] 1. This invention achieves precise point-to-point impact spraying of cooling medium onto the explosion-proof valve area during the early warning stage by inverting the explosion-proof valve downward and placing it in the bottom immersion chamber, in conjunction with the overflow port directly below the explosion-proof valve and the local flow control valve group corresponding to each battery cell, thereby improving heat exchange efficiency.

[0049] 2. This invention collects cell temperature and pressure fluctuation signals in the cooling cycle system, calculates the temperature rise rate and extracts the characteristics of impact pressure waves, and comprehensively determines the stage of thermal runaway evolution. This enables early identification of early signs of thermal runaway. Compared with the traditional fixed temperature threshold triggering method, it upgrades the response mechanism from passive response to active defense, significantly reducing the probability of thermal runaway.

[0050] 3. This invention divides the thermal management process into four modes: normal, early warning, runaway, and post-processing. It implements a graded control strategy of low-energy temperature equalization, local pulse jet enhanced heat dissipation, temporary full immersion quenching at over-rated speed, and medium-speed passivation to prevent reignition, thereby achieving closed-loop management of thermal safety throughout the entire cycle. This reduces thermal management power consumption under normal operating conditions and completely blocks heat spread during runaway.

[0051] 4. This invention, by setting up a gas-liquid separation structure with a side air intake channel, utilizes the principles of inertial separation and gravity settling to achieve three-phase physical separation of gas, liquid, and solid, so that only non-flammable gas is discharged in the event of thermal runaway, thus solving the secondary disaster problem caused by "liquid-laden eruption" in traditional solutions. Moreover, this structure does not require external energy and remains reliable under extreme conditions. Attached Figure Description

[0052] Figure 1 This is an exploded schematic diagram of the square-shell battery pack of the present invention;

[0053] Figure 2 This is an exploded front view of the soft-pack battery pack of the present invention;

[0054] Figure 3 This is an exploded view of the soft-pack battery pack of the present invention;

[0055] Figure 4This is an exploded bottom view of the soft-pack battery pack of the present invention;

[0056] Figure 5 This is a front cross-sectional view of the soft-pack battery pack of the present invention;

[0057] Figure 6 This is the present invention. Figure 5 Enlarged view of a portion of point A in the middle;

[0058] Figure 7 This is a side cross-sectional view of the soft-pack battery pack of the present invention;

[0059] Figure 8 This is a partially enlarged schematic diagram of the double-umbrella-shaped structure of the present invention;

[0060] Figure 9 This is a front view of the overall structure of the battery pack of the present invention;

[0061] Figure 10 This is a side cross-sectional view of the overall structure of the battery pack of the present invention;

[0062] Figure 11 This is the present invention. Figure 10 Enlarged view of a portion of point B in the middle;

[0063] Figure 12 A schematic diagram of the overall process of the battery pack thermal management control method of the present invention. Detailed Implementation

[0064] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1

[0066] A semi-submerged battery pack with an inverted explosion-proof valve achieves physical isolation and quenching of the source of thermal runaway through the inverted explosion-proof valve and the bottom semi-submerged structure. Based on the intelligent identification of the thermal runaway evolution stage by the controller, the cooling system is driven to perform graded mode switching to achieve full-cycle thermal safety management from passive heat dissipation to active defense.

[0067] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the battery pack mainly includes: a housing 1, battery cells 2 (multiple battery cells 2 form a battery cell array), a cooling medium 3, a local flow control valve group 4, a controller 5, a branch flow channel 6, a cooling medium inlet 7, a cooling medium outlet 8, a pressure relief valve 9, a flow channel 10, an exhaust guide pipe 11, a double umbrella-shaped structure 11.1, a top cover 12, a battery cell explosion-proof valve 13, an overflow port 14, a battery cell fixing baffle 15, and a CCS16 (an integrated assembly of battery cell tab brackets, busbars, low-voltage acquisition harnesses, etc.).

[0068] The housing 1, serving as the main support for the battery pack, is located at the bottom of the battery pack. Its bottom has an immersion cavity (i.e., the bottom cavity of housing 1) for containing the cooling medium. Housing 1 is equipped with a cell-limiting boss 1.1, which supports the cells and creates a channel for the cooling medium to flow between the bottom of the cells and the housing. The bottom of housing 1 also has a cooling medium inlet 7 and a cooling medium outlet 8, which are connected to the outlet and inlet of an external heat exchange device, respectively. These outlets are used to re-inject the cooled cooling medium into the battery pack and to output the high-temperature cooling medium to the external heat exchange device for cooling.

[0069] Cell 2 (an array of multiple square-shell or pouch cells) adopts a CTP (Cell to Pack) modular design and is directly fixed to housing 1. The positive and negative terminals of each cell face upwards, and the cell explosion-proof valve 13 is located at the bottom of the cell and faces the immersion chamber. The bottom sides of the cell are fixed to the limiting bosses 1.1 on housing 1 using structural adhesive. Cell fixing baffles 15 are provided between the cells for auxiliary fixation; after the cells are stacked, the expansion of the foam between them initially secures them. The terminals, busbars (located in CCS16), and low-voltage acquisition harness of each cell are located in the gas phase space above the cooling medium liquid level.

[0070] The CCS16 includes components such as a plastic bracket, busbar, and low-voltage acquisition harness, which are integrated together through plastic parts and positioned above the battery cell array.

[0071] The top cover 12 is located on the top of the battery pack for protection and sealing.

[0072] Cooling medium 3 fills the flow channels of housing 1 and the lower half of the battery cell, forming a semi-immersed environment. The liquid level is set to submerge the explosion-proof valve 13 of the battery cell, while the battery cell's terminals, busbars, and low-voltage acquisition harness are above the liquid surface. The cooling medium can be a fluorinated liquid, natural ester insulating oil, synthetic ester insulating oil, or silicone oil, etc., which have insulating and thermally stable properties. The liquid level is 30% to 50% of the battery cell height.

[0073] The cell explosion-proof valve 13 is located at the bottom of each cell, upside down. When the internal pressure of the cell reaches the limit, the cell explosion-proof valve 13 automatically ruptures to release pressure and prevent the cell from exploding. Because the explosion-proof valve 13 is positioned downwards and submerged in the cooling medium, in the event of thermal runaway, the high-temperature ejected material is directly sprayed downwards into the cooling medium, where it absorbs heat and isolates oxygen, preventing it from igniting the busbars and wiring harnesses or other electrical components upwards.

[0074] The battery pack is equipped with a cooling circulation system, which is connected to the immersion chamber and is used to drive the circulation of the cooling medium. The cooling circulation system includes a main circulation pump (not shown separately in the figure) and multiple local flow control valve groups 4, each of which is configured corresponding to each battery cell 2.

[0075] like Figure 5 , Figure 6 As shown, the housing 1 is provided with a flow channel 10, which includes a main circulation flow channel and various branch flow channels 6. The main circulation flow channel is connected to the cooling medium inlet 7 and the cooling medium outlet 8, and the various branch flow channels 6 are connected to the main circulation flow channel, which are used to introduce the cooling medium into various areas of the battery pack housing.

[0076] Each battery cell has an overflow port 14 located directly below its explosion-proof valve 13. Each overflow port 14 is positioned directly below the corresponding explosion-proof valve 13, with a vertical distance of 10mm to 20mm between them. The overflow port 14 is connected to the cooling circulation system via a branch channel 6. Each branch channel 6 is equipped with an independent local flow control valve assembly 4, which can be independently opened, closed, or its flow rate adjusted. The 10mm to 20mm distance between the overflow port 14 and the area directly below the explosion-proof valve 13 ensures effective heat exchange while allowing the explosion-proof valve to open normally. The connection between each overflow port 14 and the cooling circulation system allows the cooling medium to be sprayed from the overflow port 14 through the branch channel 6 into the area of ​​the explosion-proof valve 13, achieving direct contact cooling.

[0077] In this embodiment, the geometric coupling structure between the overflow port 14 and the explosion-proof valve 13, located 10mm to 20mm directly below, allows the cooling medium to directly impact the explosion-proof valve area of ​​the battery cell in the warning mode. When the cooling medium is sprayed onto the surface of the explosion-proof valve 13 area through the overflow port 14, the jet impact generates forced convection heat transfer to remove heat; at the same time, the turbulence formed by the jet impact disrupts the boundary layer, increasing the heat transfer coefficient.

[0078] Under normal operating conditions, the cooling medium enters the main channel through the cooling medium inlet 7, and is distributed to various parts of the battery pack through the branch channels 6. After cooling the cells, it flows out through the cooling medium outlet 8 to the external heat exchange device for further cooling, thus completing the cycle.

[0079] The battery pack is equipped with an information acquisition module, which includes at least a temperature acquisition unit and a pressure fluctuation acquisition unit. The temperature acquisition unit collects the temperature of each cell 2, and can use temperature sensors such as thermocouples or thermistors, each installed on the surface of each cell. The pressure fluctuation acquisition unit is located in the cooling circulation system, installed on the pipeline at the cooling medium inlet 7 or cooling medium outlet 8, and is used to collect pressure fluctuation signals in the cooling circulation system. This pressure fluctuation acquisition unit is a high-frequency dynamic pressure sensor with a sampling rate ≥100Hz.

[0080] The controller 5 (i.e., the battery management system, BMS) is electrically connected to the information acquisition module, the main circulation pump, and each local flow control valve group 4. The controller 5 is used to calculate the temperature rise rate of each cell based on the acquired temperature, process the acquired pressure fluctuation signal to extract the characteristics of the impact pressure wave, determine the thermal runaway evolution stage by combining the temperature rise rate and the impact pressure wave characteristics, and control the speed of the main circulation pump and the opening degree of each local flow control valve group according to the thermal runaway evolution stage.

[0081] The controller 5 is pre-set with threshold parameters for each mode, including temperature thresholds T1 and T2, temperature rise rate thresholds V1, V2, and V3, temperature difference threshold ΔTmax, and safe temperature threshold T_safe. The controller 5 acquires the temperature Ti of each cell and the high-frequency pressure fluctuation signal in the cooling circulation pipeline in real time, with a sampling rate ≥100Hz. The controller 5 performs bandpass filtering and envelope analysis on the high-frequency pressure wave. If an impact pressure wave with an amplitude exceeding the threshold is detected, it is identified as an "early acoustic fingerprint of thermal runaway". The controller 5 integrates temperature, temperature rise rate, pressure wave, and voltage collapse rate, and outputs the current thermal runaway evolution stage through a decision tree or lightweight neural network.

[0082] Impulsive pressure waves are transient pressure pulse signals generated in the cooling medium when a micro-short circuit, lithium plating, or rapid release of localized gas occurs inside the battery cell. These pulses have a steep leading edge, wide bandwidth, and amplitude exceeding the ambient noise threshold. Their typical characteristic frequency range is 1 kHz to 10 kHz. This pressure wave signal propagates at the speed of sound in the cooling medium and can be captured by a high-frequency dynamic pressure sensor installed on the pipeline. The pressure wave signal appears 5 to 30 seconds before the temperature rises.

[0083] Controller 5 calculates the temperature rise rate dTi / dt for each cell. When the amplitude of the filtered signal envelope exceeds a preset threshold, controller 5 determines that an "early acoustic fingerprint of thermal runaway" has been detected.

[0084] This invention divides the battery pack thermal management process into four modes, which are automatically switched by the controller 5 based on real-time monitoring data.

[0085] Mode 1: Isotropic Equilibrium Mode

[0086] The triggering conditions are: the temperature of all cells is lower than the first temperature threshold T1 (45℃), and the temperature rise rate of all cells is lower than the first temperature rise rate threshold V1 (1℃ / s).

[0087] In the first mode, the main circulation pump operates at a first speed, which is 20% to 30% of the rated speed, and all local flow control valve groups 4 are closed. At this time, the cooling medium circulates slowly only through the bottom main channel. In this mode, thermal management power consumption is reduced, and natural temperature difference is eliminated.

[0088] Mode 2: Localized Enhanced Heat Dissipation Mode

[0089] The triggering conditions are: any cell meets one of the following conditions: exceeds the second temperature threshold T2 (55℃), the temperature rise rate exceeds the second temperature rise rate threshold V2 (2℃ / s), the temperature difference with the adjacent cell exceeds the temperature difference threshold ΔTmax (5℃), or an abnormal shock pressure wave is detected.

[0090] In mode two, controller 5 first identifies the number of the abnormal battery cell, then opens the corresponding local flow control valve group 4 to its maximum opening, and simultaneously increases the speed of the main circulation pump to the second speed, which is 60% to 80% of the rated speed. The cooling medium is pulsedly sprayed through overflow port 14 to the bottom explosion-proof valve 13 area of ​​the battery cell and the side of the shell, forming turbulent enhanced heat transfer.

[0091] In one implementation, the local flow control valve assembly 4 opens and closes in a pulsed manner, causing the cooling medium to impact the explosion-proof valve 13 area in a pulsed jet manner. Compared with continuous jetting, pulsed jetting can enhance the turbulence intensity formed by the jet impact. The duration of the pulse jetting can be dynamically adjusted according to the temperature rise rate of the abnormal battery cell until the temperature rise rate drops back to a safe range.

[0092] This mode actively suppresses heat accumulation 10 to 30 seconds before thermal runaway occurs. The early warning mechanism based on pressure waves and dT / dt allows this mode to be activated before the temperature reaches the danger threshold.

[0093] Mode 3: Runaway Quenching and Isolation Mode

[0094] The triggering conditions are: any cell meets one of the following conditions: the cell explosion-proof valve 13 is triggered by an action signal, the voltage collapse rate is greater than 0.5V / ms, or the temperature rise rate exceeds the third temperature rise rate threshold V3 (10℃ / s).

[0095] The voltage collapse rate is defined as |ΔU / Δt|, which is the voltage drop per unit time, measured in V / ms. When the voltage collapse rate of any cell exceeds 0.5V / ms, it indicates that a short circuit has occurred inside the cell, thermal runaway is irreversible, and the third mode is immediately initiated.

[0096] In Mode 3, all local flow control valve groups 4 in the area where the abnormal battery cell is located are fully open, and the main circulation pump is increased to the third speed, which is 120%~150% of the rated speed. Simultaneously, local flow control valve groups 4 in the adjacent areas of the abnormal battery cell are opened, forming a liquid wall isolation. In this mode, the liquid level in the area where the abnormal battery cell is located rises rapidly due to high-speed liquid injection, reaching a temporary full immersion state, submerging the runaway battery cell in the high-speed flowing cooling medium. Figure 7 , Figure 8As shown, the double umbrella-shaped structure 11.1 at the top of the exhaust guide pipe 11 ensures that high-temperature gas enters the pipe from the side, while the cooling medium droplets at the bottom are blocked and fall back by the lower umbrella, and the molten material at the top is blocked by the upper umbrella, thus achieving gas-liquid-solid three-phase separation, and only non-flammable gas is discharged through the pressure relief valve 9.

[0097] Complete immersion refers to the cooling medium level exceeding the top surface of the malfunctioning battery cell, causing the entire cell to be submerged in the cooling medium. This complete immersion state is temporary, lasting only during the third mode duration. After the runaway battery cell is quenched, the liquid level gradually returns to the half-immersion height.

[0098] Liquid barrier isolation refers to the process where, after the local flow control valve group 4 in the adjacent area is opened, the cooling medium is rapidly injected around the adjacent cells, causing the liquid level to rise quickly and forming a liquid barrier between the abnormal cell and the adjacent cells. This liquid barrier serves both to absorb heat and isolate oxygen, blocking heat radiation and the path of flame propagation.

[0099] Operating the main circulation pump at the third speed (120%~150% of the rated speed) is considered over-rated operation. This state is transient. At this speed, the output flow and head of the main circulation pump are both increased, which is sufficient to raise the liquid level in the abnormal cell area to a completely submerged state within a short period of time.

[0100] This mode immerses the runaway battery cell in a high-speed cooling medium for a short period of time, quenching the flame and blocking the transfer of heat to adjacent battery cells.

[0101] Mode 4: Safety Passivation and Exhaust Mode

[0102] The triggering condition is: the temperature of the abnormal battery cell drops below the preset safe temperature threshold T_safe (50℃) and there is no open flame.

[0103] In Mode 4, the main circulation pump maintains a fourth operating speed, which is 50% of the rated speed, continuously removing residual heat. The exhaust duct 11 continues to discharge non-combustible gas, while the cooling medium and solid particles are trapped by the double-umbrella structure 11.1. The local flow control valve group 4 gradually closes, and the system attempts to return to Mode 1. This mode prevents reignition.

[0104] The preset safe temperature threshold T_safe is determined based on the material system of the battery cell. In this embodiment, T_safe is set to 50°C.

[0105] The relationship between the first, second, third, and fourth rotational speeds is as follows: first rotational speed < fourth rotational speed < second rotational speed < third rotational speed.

[0106] Exhaust flow guide structure

[0107] The bottom of the battery pack housing is equipped with an exhaust pipe 11 and a pressure relief valve 9. One end of the exhaust pipe 11 connects to the upper interior space of the battery pack, and the other end connects to the pressure relief valve 9. The pressure relief valve 9 is installed at the bottom of the housing with its opening facing downwards to prevent external moisture from entering.

[0108] The top of the exhaust guide pipe 11 is provided with a gas-liquid separation structure (i.e., a double umbrella-shaped structure 11.1). The gas-liquid separation structure has a side air intake channel, through which gas enters the exhaust guide pipe 11, and the gas-liquid separation structure blocks liquid and solid particles from passing through.

[0109] In one implementation, the gas-liquid separation structure includes an upper umbrella-shaped baffle and a lower umbrella-shaped baffle (i.e., a double umbrella-shaped structure 11.1) arranged coaxially. Both the upper and lower umbrella-shaped baffles face downwards, with a side air intake gap between them. The double umbrella-shaped structure is made of a high-temperature resistant and flame-retardant material, which can withstand the high-temperature gas generated by thermal runaway without deformation.

[0110] The gas-liquid separation structure is fixed to the top of the exhaust guide pipe 11. The side air intake gap between the upper and lower umbrella-shaped baffles is determined based on the internal volume of the battery pack and the expected exhaust flow rate.

[0111] The double-umbrella structure 11.1 achieves the following multiple functions:

[0112] First, it prevents liquid backflow. The cooling medium in the bottom immersion chamber may splash due to pressure fluctuations or shaking. The lower umbrella blocks and pulls the splashed droplets back down, preventing liquid from entering the exhaust guide pipe 11. When the splashed droplets travel upward in a straight line, they encounter the lower umbrella-shaped baffle, are blocked by the umbrella surface, and fall back into the immersion chamber due to gravity.

[0113] Second, it prevents external intrusion. If there is liquid or hot molten material on the outside of the top cover, the top umbrella will block it, preventing foreign objects from falling into the pressure relief valve 9. This function ensures that, in a non-thermal runaway state, moisture or impurities in the external environment cannot enter the battery pack through the pressure relief valve.

[0114] Third, directional exhaust. In the event of thermal runaway, the high-pressure gas inside enters the exhaust guide pipe 11 through the side gap and then exits downwards through the pressure relief valve 9. As the gas enters the exhaust guide pipe 11, its flow direction changes from upwards to horizontal and then downwards. Cooling medium droplets and solid particles, due to inertia, cannot follow the gas in this directional change and are thrown out and fall back to the bottom of the casing; only the gas enters the guide pipe through the side air inlet gap. This design achieves gas-liquid-solid three-phase separation, ensuring that only non-flammable gases are discharged.

[0115] This invention employs a CTP (Computer-to-Pack) modular design. The immersion chamber of the housing 1 is equipped with a cell-limiting boss 1.1. Each cell 2 is upright fixed to the cell-limiting boss 1.1 using structural adhesive. Foam is placed between adjacent cells, and the expansion of the foam assists in fixing the cells. The structural adhesive serves both fixing and heat conduction functions, fixing the cells to the housing while conducting heat from the bottom of the cells to the housing. The structural adhesive can be applied by dispensing or coating. The foam is elastic foam, which is compressed after the cells are stacked, applying a compressive force to the cells through its rebound force.

[0116] The natural gaps between adjacent cells form branch channels 6 for the cooling medium, eliminating the need for additional intermediate connecting components such as guide bars or baffles. Each overflow port 14 connects to the cooling circulation system through the branch channels 6 formed by these natural gaps. This integrated molding channel has no sealing seams. By eliminating traditional guide bars, baffles, and other intermediate structures, the number of components is reduced, and the volumetric energy density is increased.

[0117] like Figure 9 , Figure 10 , Figure 11 In one alternative embodiment, the bottom plate of the housing 1 integrates an independent liquid cooling plate. The liquid cooling plate has a closed-loop coolant flow channel. The liquid cooling plate is isolated from the main body of the housing 1 by a heat insulation layer to prevent thermal crosstalk between the coolant circuit and the immersion fluid circuit. The battery pack in this embodiment also includes a coolant circuit independent of the aforementioned cooling circulation system.

[0118] The battery pack includes two independent cooling systems: one is an immersion fluid circulation system (i.e., the aforementioned cooling circulation system), and the other is a coolant circulation system. The immersion fluid circulation system includes components such as a main circulation pump, a local flow control valve assembly 4, branch flow channels 6, and an overflow port 14, used for direct contact cooling under abnormal operating conditions. The coolant circulation system includes components such as internal flow channels of the liquid cooling plate, an external circulation pump, and a heat exchanger, used for indirect cooling under normal operating conditions.

[0119] In the first mode (uniform temperature equilibrium mode), the immersion fluid circuit is completely shut off, all immersion fluid pumps and valve assemblies are de-energized, and only the coolant circuit operates at a low flow rate, with pump power at 10%~20% of rated power. Heat from the battery cells is conducted to the liquid cooling plate through solid-state conduction and carried away by the coolant. In this mode, coolant flow resistance is low, reducing pump energy consumption; the immersion fluid is stationary, preventing erosion and corrosion of the manifold and wiring harness; and the static immersion fluid acts as a heat sink, smoothing out short-term power fluctuations.

[0120] In Mode 2 (local enhanced heat dissipation mode), when the controller 5 detects the warning signal, it first increases the flow rate of the coolant circuit to 80%~100% of the rated flow rate. If the temperature rise still cannot be suppressed, it then starts the immersion liquid circuit, opens the corresponding local valve group, and uses the overflow port to pulse-jet the immersion liquid for direct contact enhanced heat dissipation.

[0121] In mode three (runaway quenching and isolation mode), once thermal runaway is detected, the immersion fluid circuit starts at full power (pump speed 120%~150%), while the coolant circuit maintains maximum flow rate, and the two work together to cool the battery. The immersion fluid quickly submerges the runaway cell to quench it, and the coolant continuously removes heat from the bottom through the liquid cooling plate.

[0122] In mode four (safe passivation and exhaust mode), after thermal runaway, the immersion fluid circuit is shut off first, and the cooling fluid circuit is used to continuously cool down the temperature. After the temperature drops below the safe threshold, the cooling fluid circuit is gradually shut off.

[0123] Under normal operating conditions, this optional implementation uses water-glycol or other coolants for indirect heat exchange through independent liquid cooling plates; the immersion liquid is only used for static storage; the coolant circuit is a closed system, eliminating the risk of contact with the battery cell terminals; the two independent cooling systems serve as backups for each other, so even if one fails, the other can still provide basic thermal management capabilities.

[0124] Example 2

[0125] like Figure 12 As shown, a battery pack thermal management control method includes the following steps:

[0126] Step S1: Initialization and parameter configuration.

[0127] Threshold parameters for each mode are set, including the first temperature threshold T1 (45℃), the second temperature threshold T2 (55℃), the first temperature rise rate threshold V1 (1℃ / s), the second temperature rise rate threshold V2 (2℃ / s), the third temperature rise rate threshold V3 (10℃ / s), the temperature difference threshold ΔTmax (5℃), the safe temperature threshold T_safe (50℃), and the voltage collapse rate threshold (0.5V / ms). Controller 5 begins real-time acquisition of the temperature Ti, voltage Ui, and high-frequency pressure fluctuation signals in the cooling circulation pipeline for each cell, with a sampling rate ≥100Hz.

[0128] Step S2: Identification of thermal runaway stage.

[0129] Controller 5 calculates the temperature rise rate (dTi / dt) and voltage collapse rate for each cell. Controller 5 performs bandpass filtering and envelope analysis on the high-frequency pressure wave; if an impact pressure wave with an amplitude exceeding a threshold is detected, it is identified as an "early acoustic fingerprint of thermal runaway." Controller 5 integrates temperature, temperature rise rate, pressure wave, and voltage collapse rate, and outputs the current thermal runaway evolution stage through a decision tree or lightweight neural network.

[0130] Step S3: Modality selection and execution.

[0131] Controller 5 executes the corresponding mode based on the determination result of step S2:

[0132] If all parameters are below the warning threshold, execute Mode 1: the main circulation pump operates at the first speed (20%~30% of rated speed), and all local valve groups are closed. The cooling medium circulates slowly only through the bottom main channel.

[0133] If any battery cell enters the warning zone (dT / dt>V2 or abnormal pressure wave or temperature difference>ΔTmax or temperature>T2), mode two is executed: Controller 5 identifies the abnormal battery cell number, opens the corresponding local valve group to its maximum opening, and the main circulation pump speeds up to the second speed (60%~80% of rated speed). Cooling medium is pulsedly sprayed through overflow port 14 to the explosion-proof valve 13 area at the bottom of the battery cell, forming turbulent enhanced heat transfer, reducing the temperature of the abnormal battery cell and suppressing heat accumulation within 10 to 30 seconds before thermal runaway occurs.

[0134] If any battery cell enters the runaway zone (explosion-proof valve activated, or dT / dt > V3, or voltage collapse rate > 0.5V / ms), mode three is executed: controller 5 sends an alarm to the vehicle or energy storage system via the CAN bus. All local valve groups in the area where the abnormal battery cell is located are fully opened, and the main circulation pump is increased to the third speed (rated 120%~150%). At the same time, the valve groups in adjacent areas are opened to form a liquid wall isolation. The liquid level in this area rises rapidly due to high-speed injection, reaching a temporary full immersion state, submerging the runaway battery cell in the high-speed flowing cooling medium. The double umbrella-shaped structure 11.1 at the top of the exhaust guide pipe 11 ensures that high-temperature gas enters the pipe from the side, and the cooling medium and solid particles are intercepted, with only non-flammable gas being discharged through the pressure relief valve 9.

[0135] Once the temperature of the runaway battery cell drops below T_safe and there is no open flame, mode four is executed: the main circulation pump is maintained at medium speed (50% of rated speed) to continuously remove residual heat. The exhaust pipe 11 continues to discharge non-flammable gas, while the cooling medium and solid particles are trapped by the double-umbrella structure 11.1. The local valve group gradually closes, and after a preset duration, attempts to return to mode one. This mode prevents reignition.

[0136] Step S4: Closed-loop feedback and modal exit.

[0137] During the execution of Mode 2 or Mode 3, controller 5 continuously monitors the temperature change rate of the abnormal cell. If the temperature drop rate exceeds the set value, the current action is maintained until the temperature drops to a safe range; if the temperature continues to rise, the system is upgraded to a higher mode.

[0138] In the above method, the correspondence between flow rate and rotational speed is as follows: the first flow rate corresponds to the circulation flow rate of the main circulation pump at the first rotational speed, the second flow rate corresponds to the circulation flow rate of the main circulation pump at the second rotational speed, the third flow rate corresponds to the circulation flow rate of the main circulation pump at the third rotational speed, and the fourth flow rate corresponds to the circulation flow rate of the main circulation pump at the fourth rotational speed. The magnitudes of the flow rates are: first flow rate < fourth flow rate < second flow rate < third flow rate.

[0139] The overall working principle of the present invention will be explained below.

[0140] Under normal operating conditions (Mode 1), all cells 2 are installed on the housing 1 with their positive and negative terminals facing upwards and the explosion-proof valve 13 facing downwards. The bottom of the cells is submerged in the cooling medium (the liquid level is 30% to 50% of the cell height), and the terminals, busbars, and wiring harnesses are above the liquid surface. The main circulation pump operates at a low speed of 20% to 30% of its rated speed, all local valve groups 4 are closed, and the cooling medium circulates slowly only through the bottom main channel to eliminate the natural temperature difference between the cells.

[0141] When controller 5 detects an abnormally high rate of temperature rise in a battery cell (dT / dt>V2) or captures characteristics of an impact pressure wave (frequency band 1kHz~10kHz, amplitude exceeding the threshold), it determines that it has entered the warning stage (mode two). Controller 5 identifies the abnormal battery cell number, opens the corresponding local valve group 4 to its maximum opening, accelerates the main circulation pump to 60%~80% of its rated speed, and sprays the cooling medium through overflow port 14 in a pulse manner into the explosion-proof valve 13 area. This pulsed jet impact disrupts the boundary layer, increases the heat transfer coefficient, and actively suppresses heat accumulation 10 to 30 seconds before thermal runaway occurs.

[0142] If the temperature of the abnormal battery cell continues to rise, triggering the explosion-proof valve 13, and the voltage collapse rate > 0.5V / ms or dT / dt > V3, it is determined that the system has entered the runaway stage (mode three). The main circulation pump is increased to above the rated speed (120%~150%), and all local valve groups 4 in the area where the abnormal battery cell is located and the adjacent areas are opened. The high-speed cooling medium submerges the abnormal battery cell and forms a liquid wall isolation in the adjacent areas. The runaway battery cell is temporarily fully immersed in the high-speed cooling medium, the flame is quenched, and the heat transfer to the adjacent battery cells is blocked. At the same time, the high-temperature and high-pressure gas in the battery pack enters the exhaust pipe 11 through the side air intake channel through the double umbrella-shaped structure 11.1 at the top of the exhaust pipe 11. The cooling medium droplets and solid particles are blocked and fall back due to inertial separation and gravity settling. Only non-flammable gas is discharged from the pressure relief valve 9.

[0143] When the temperature of the runaway battery cell drops below the safe temperature threshold and there is no open flame, the system is determined to enter the post-processing stage (Mode 4). The main circulation pump reduces its speed to 50% of its rated medium speed, and local valve groups are gradually closed to continuously remove residual heat and prevent reignition. After a preset time, the system attempts to return to Mode 1, completing the full-cycle thermal safety closed-loop management from normal operation to early warning, runaway, and post-processing.

[0144] This invention combines an inverted cell explosion-proof valve with a bottom semi-submerged structure, along with an overflow port directly below the explosion-proof valve and local flow control valve groups corresponding to each cell, to achieve graded identification and graded active intervention in the thermal runaway evolution stage. This solves the problems of slow response and high energy consumption in traditional solutions, and also solves the secondary disaster problem of liquid ejection through a double umbrella-shaped exhaust structure. At the same time, the modular design and semi-submerged structure of CTP reduce system cost and weight, and improve volumetric energy density.

[0145] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A battery pack, characterized by, include: The housing has an immersion chamber at its bottom for containing the cooling medium; Multiple battery cells are disposed inside the enclosure, with the explosion-proof valve of each battery cell facing downwards and toward the immersion chamber; A cooling circulation system is connected to the immersion chamber. The cooling circulation system includes a main circulation pump and multiple local flow control valve groups, each of which is correspondingly set to each of the battery cells. Multiple overflow ports are respectively located below the explosion-proof valve of each of the battery cells, and each of the overflow ports is connected to the cooling circulation system. The information acquisition module includes at least a temperature acquisition unit and a pressure fluctuation acquisition unit installed in the cooling circulation system; The controller is electrically connected to the information acquisition module, the main circulation pump, and each of the local flow control valve groups. The controller is configured to: The temperature rise rate of each cell is calculated based on the collected temperature, and the collected pressure fluctuation signal is processed to extract the characteristics of the impact pressure wave. The thermal runaway evolution stage is determined by combining the temperature rise rate and the characteristics of the shock pressure wave. Controlling the rotational speed of the main circulation pump and the opening degree of the local flow control valve assembly according to the thermal runaway evolution stage includes at least: In the first mode, the main circulation pump operates at a first speed, and each of the local flow control valve groups is closed; In the second mode, the main circulation pump operates at a second speed greater than the first speed, and the local flow control valve group corresponding to the abnormal cell is opened, so that the cooling medium impacts the explosion-proof valve through the overflow port.

2. The battery pack of claim 1, wherein, The thermal runaway evolution stage also includes a runaway stage; The controller executes a third mode during the runaway phase: the main circulation pump operates at a third speed, which is 120% to 150% of the rated speed of the main circulation pump, and the abnormal battery cell and the local flow control valve group in the area adjacent to the abnormal battery cell are opened, so that the cooling medium completely submerges the abnormal battery cell and forms a liquid wall for isolation in the adjacent area.

3. A battery pack according to claim 2, characterized in that, When the abnormal cell temperature drops below a preset safe temperature threshold and there is no open flame, the controller executes the fourth mode: the main circulation pump operates at a fourth speed between the first speed and the second speed, and the local flow control valve group gradually closes.

4. A battery pack according to claim 1, characterized in that, Each of the overflow ports is located directly below the corresponding explosion-proof valve, and the vertical distance between the overflow port and the explosion-proof valve is 10mm~20mm; In the second mode, the controller controls the local flow control valve group to open and close in a pulse manner, so that the cooling medium pulses and impacts the explosion-proof valve area.

5. A battery pack according to claim 1, characterized in that, The bottom of the box is also provided with an exhaust guide pipe and a pressure relief valve. One end of the exhaust guide pipe is connected to the upper space inside the box, and the other end is connected to the pressure relief valve. The exhaust guide pipe has a gas-liquid separation structure at one end inside the housing. The gas-liquid separation structure has a side air intake channel. Gas enters the exhaust guide pipe through the side air intake channel. The gas-liquid separation structure blocks liquid and solid particles from passing through.

6. A battery pack according to claim 5, characterized in that, The gas-liquid separation structure includes an upper umbrella-shaped baffle and a lower umbrella-shaped baffle arranged coaxially. Both the upper umbrella-shaped baffle and the lower umbrella-shaped baffle are arranged downwards, with a side air intake gap between them.

7. A battery pack according to claim 1, characterized in that, The immersion chamber is provided with a cell limiting boss, and each cell is fixed upright on the limiting boss with the positive and negative terminals of each cell facing upwards; foam is provided between adjacent cells, and the expansion of the foam helps to fix the cells; the natural gap between adjacent cells forms a branch flow channel, and each overflow port is connected to the cooling circulation system through the branch flow channel.

8. A battery pack according to claim 1, characterized in that, The bottom of the housing is also integrated with an independent liquid cooling plate, and the battery pack also includes a coolant circuit independent of the cooling circulation system. In the first mode, the controller only activates the coolant circuit; in the second or third mode, it simultaneously activates the coolant circuit and the cooling circulation system for coordinated cooling.

9. A battery pack thermal management control method, characterized in that, include: Real-time acquisition of temperature of each battery cell and pressure fluctuation signals in the cooling circulation system; The temperature rise rate of each cell is calculated, and the pressure fluctuation signal is processed to extract the characteristics of the impact pressure wave. The current thermal runaway evolution stage is determined by combining the temperature rise rate and the characteristics of the shock pressure wave. The thermal runaway evolution stage includes at least a normal stage and a warning stage. If the condition is determined to be in the normal phase, the cooling circulation system is controlled to operate at the first flow rate, and each local valve group is closed. If the warning stage is determined, the cooling circulation system is controlled to operate at a second flow rate greater than the first flow rate, and the local valve group corresponding to the abnormal cell is opened, so that the cooling medium impacts the explosion-proof valve area of ​​the abnormal cell through the overflow port.

10. A battery pack thermal management control method according to claim 9, characterized in that, Bandpass filtering and envelope analysis are performed on the pressure fluctuation signal to extract the characteristics of the impact pressure wave; The sampling frequency of the pressure fluctuation signal is ≥100Hz, and the characteristic frequency of the impact pressure wave is 1kHz~10kHz. The thermal runaway evolution stage also includes a runaway stage and a post-processing stage; The determination of the runaway stage is also based on the voltage collapse rate, which is calculated based on the real-time collected voltage of each cell. If the system is determined to be in the out-of-control stage, the cooling circulation system is controlled to operate at a third flow rate greater than the second flow rate, and the local valve group of the abnormal cell and the adjacent area is opened to temporarily and completely submerge the abnormal cell in the cooling medium. If the process is determined to be in the post-processing stage, the cooling circulation system is controlled to operate at a fourth flow rate between the first flow rate and the second flow rate until the abnormal cell temperature drops below the safety threshold.

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