Temperature management method for liquid-cooled battery pack

Abstract

The present invention relates to the field of battery technology, and specifically provides a temperature management method for a liquid-cooled battery pack, the method comprising the following steps: judging the working state of a battery cell in a liquid-cooled battery pack, and acquiring the highest temperature of the battery cell; when the battery cell is in a charging or discharging state, executing a first cooling strategy according to the highest temperature of the battery cell; when the battery cell is in a state to be charged or discharged, executing a second cooling strategy according to the highest temperature of the battery cell, wherein the second cooling strategy is different from the first cooling strategy; when the battery cell is in a state to be charged, executing a first heating strategy according to the highest temperature of the battery cell; when the battery cell is in a state to be discharged, executing a second heating strategy according to the highest temperature of the battery cell, wherein the second heating strategy is different from the first heating strategy. Thus, different temperature management strategies are adopted in different states of the battery cell, which facilitates the realization of multi-dimensional temperature management, can improve heat dissipation and heating efficiency, and avoid excessive waste of energy.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a temperature management method for a liquid-cooled battery pack. Background Art

[0002] Battery pack liquid cooling technology is mainly divided into cold plate type and immersion type. Cold plate liquid cooling is to contact one side of the battery cell with the liquid cold plate, and the coolant flows through the flow channel in the liquid cold plate, and removes the heat generated by the battery cell by contact heat conduction, repeating the cycle. Immersion liquid cooling is to immerse the battery cell or module directly in the coolant to achieve the purpose of full contact between the battery cell and the coolant, directly remove the heat generated by the battery cell by circulating the coolant, or use a heat conduction device to extract the heat of the coolant from the combined liquid-cooled battery pack, and indirectly remove the heat generated by the battery cell by not circulating the coolant.

[0003] At present, the temperature management of liquid-cooled battery packs is only a single battery cell temperature target control, which is difficult to adjust and has low energy utilization, especially in the heating situation. Because the coolant is heated, long-term continuous heating is required to meet the temperature for charging and discharging the battery cell. Summary of the invention

[0004] In order to solve one of the above-mentioned technical problems, the present invention proposes the following technical solution.

[0005] The first aspect of the present invention provides a temperature management method for a liquid-cooled battery pack, comprising the following steps: determining the working state of a battery cell in the liquid-cooled battery pack, and acquiring the maximum temperature of the battery cell; when the battery cell is in a charging or discharging state, executing a first cooling strategy according to the maximum temperature of the battery cell; when the battery cell is in a state to be charged or discharged, executing a second cooling strategy according to the maximum temperature of the battery cell, wherein the second cooling strategy is different from the first cooling strategy; when the battery cell is in a state to be charged, executing a first heating strategy according to the maximum temperature of the battery cell; when the battery cell is in a state to be discharged, executing a second heating strategy according to the maximum temperature of the battery cell, wherein the second heating strategy is different from the first heating strategy.

[0006] In addition, the temperature management method of the liquid-cooled battery pack according to the above embodiment of the present invention may also have the following additional technical features.

[0007] According to one embodiment of the present invention, the liquid-cooled battery pack includes a cold plate liquid cooling structure and an immersion liquid cooling structure.

[0008] According to one embodiment of the present invention, a first cooling strategy is executed according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell rises to a first control temperature, first turning on the cold plate liquid cooling structure to perform cold plate liquid cooling; when the maximum temperature of the battery cell rises to a second control temperature, maintaining the cold plate liquid cooling and turning on the immersion liquid cooling structure to perform immersion liquid cooling, so as to perform hybrid cooling, wherein the second control temperature is greater than the first control temperature; during the hybrid cooling process, when the maximum temperature of the battery cell drops back to the first drop-back temperature, first turning off the cold plate liquid cooling structure and maintaining the immersion liquid cooling; when the maximum temperature of the battery cell drops back to the second drop-back temperature, turning off the immersion liquid cooling structure to stop cooling, wherein the second drop-back temperature is lower than the first drop-back temperature.

[0009] According to one embodiment of the present invention, a second cooling strategy is executed according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is greater than a first preset temperature and less than or equal to a second preset temperature, turning on the cold plate liquid cooling structure for cold plate liquid cooling, wherein the second preset temperature is greater than the first preset temperature, and when the maximum temperature of the battery cell drops back to a third drop temperature, turning off the cold plate liquid cooling structure; when the maximum temperature of the battery cell is greater than the second preset temperature, turning on the cold plate liquid cooling structure and the immersion liquid cooling structure to perform hybrid cooling, and when the maximum temperature of the battery cell drops back to the third drop temperature, turning off the cold plate liquid cooling structure and the immersion cooling structure to stop cooling.

[0010] According to one embodiment of the present invention, a first heating strategy is executed according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is lower than the first charging temperature, first starting the cold plate liquid cooling structure heating mode to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first charging temperature and lower than the second charging temperature, then starting the immersion liquid cooling structure heating mode to heat the battery cell; until the maximum temperature of the battery cell reaches the second charging temperature, the heating is stopped, wherein the second charging temperature is higher than the first charging temperature.

[0011] According to one embodiment of the present invention, a second heating strategy is executed according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is lower than the first discharge temperature, first starting the cold plate liquid cooling structure heating mode to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and lower than the second discharge temperature, then starting the immersion liquid cooling structure heating mode to heat the battery cell, until the maximum temperature of the battery cell reaches the second discharge temperature, then stopping the heating, wherein the second discharge temperature is greater than the first discharge temperature; when the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and lower than the second discharge temperature, first starting the immersion liquid cooling heating mode to heat the battery cell, then starting the cold plate liquid cooling structure heating mode to heat the battery cell, until the maximum temperature of the battery cell reaches the second discharge temperature, then stopping the heating.

[0012] According to one embodiment of the present invention, the immersion liquid cooling structure includes multiple flow equalizing layers, the battery modules in the battery pack include multiple layers, each of the flow equalizing layers is located between the battery modules of adjacent layers, the flow equalizing layers are provided with openings, the diameters of the openings of the flow equalizing layers are equal or decrease successively from bottom to top, the water inlet of the immersion liquid of the immersion liquid cooling structure is located above the uppermost flow equalizing layer, and the water outlet of the immersion liquid is located below the lowermost flow equalizing layer.

[0013] According to an embodiment of the present invention, a heating module for heating the immersion liquid is installed on the back of the flow balancing layer.

[0014] According to one embodiment of the present invention, the immersion liquid cooling structure further includes an isolation zone disposed between adjacent battery cells.

[0015] According to one embodiment of the present invention, the cold plate liquid cooling structure includes a liquid cooling plate and a thermal pad disposed at the bottom of the liquid-cooled battery pack.

[0016] The technical solution of the embodiment of the present invention adopts different temperature management strategies under different states of the battery cell, which is convenient for realizing multi-dimensional temperature management, can improve heat dissipation and heating efficiency, and avoid excessive waste of energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a battery module according to an example of the present invention.

[0018] Figure 2 The figure is a schematic diagram of the structure of an FPC acquisition board of an example of the present invention.

[0019] Figure 3 The figure is a schematic diagram of the structure of a flow balancing layer and a heating module according to an example of the present invention.

[0020] Figure 4This is a schematic diagram of the structure inside a combined liquid-cooled battery pack of an example of the present invention.

[0021] Figure 5 A schematic diagram of the external structure of a combined liquid-cooled battery pack according to an example of the present invention.

[0022] Figure 6 Flow chart of a temperature management method for a liquid-cooled battery pack according to an embodiment of the present invention.

[0023] Figure 7 This is a flow chart of a first cooling strategy according to an example of the present invention.

[0024] Figure 8 This is a flow chart of a second cooling strategy according to an example of the present invention.

[0025] Fig. 9 This is a flow chart of a first heating strategy according to an example of the present invention.

[0026] Fig.10 This is a flow chart of a second heating strategy according to an example of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In order to achieve cooling effect and temperature uniformity between cells, the existing cold plate liquid cooling technology often requires complex design and multiple simulations and experimental verifications for the internal cooling pipelines. The bottom cold plate liquid cooling cannot solve the large temperature difference between the upper and lower temperatures of a single cell, and the side-cooling liquid cooling cannot contact the cell surface well and greatly increases the complexity of the structure, resulting in increased costs. The combination of bottom cooling and side cooling, such as the "Immersed High-efficiency Liquid-Cooled Heat Exchange Battery PACK Structure" with authorization number CN219534652U, can solve the problem of temperature uniformity, but it causes an increase in complexity and cost.

[0029] The existing immersion liquid cooling technology is still in its early stages. The immersion fluids used (such as fluorinated and mineral-based) are quite different from the existing immersion fluids (ethylene glycol aqueous solutions), requiring the redevelopment of liquid coolers and systems, and resulting in a significant increase in circulation volume.

[0030] The existing method for collecting the voltage and temperature of the battery cell is to use a wiring harness or FPC to collect the voltage and temperature of the external pole of the battery cell.

[0031] To this end, an embodiment of the present invention proposes a temperature management method for a liquid-cooled battery pack, wherein the liquid-cooled battery pack includes a battery cell, a cold plate liquid cooling structure and an immersion liquid cooling structure. The immersion liquid cooling structure includes an immersion liquid and a plurality of flow equalizing layers. The battery module in the liquid-cooled battery pack includes multiple layers, each flow equalizing layer is located between the battery modules of adjacent layers, and the flow equalizing layer is provided with openings. The diameters of the openings of each flow equalizing layer are equal or decrease successively from bottom to top. The water inlet of the immersion liquid is located above the flow equalizing layer of the uppermost layer, and the water outlet of the immersion liquid is located below the flow equalizing layer of the lowermost layer.

[0032] A heating module for heating the immersion liquid is installed on the back of the flow-distributing layer.

[0033] The immersion liquid cooling structure also includes an isolation zone arranged between adjacent battery cells, so that the immersion liquid can flow over the surface of the battery cells.

[0034] The cold plate type liquid cooling structure comprises a liquid cooling plate and a thermal pad arranged at the bottom of the liquid-cooled battery pack.

[0035] Specifically, the present invention adopts a hybrid liquid cooling method, combining the advantages of cold plate liquid cooling and immersion liquid cooling, and at the same time solves the problems of single-cell temperature uniformity and high structural complexity of cold plate liquid cooling, solves the problem of large circulation volume and usage of immersion liquid cooling that requires redesign of the liquid cooling system, and the problem of distortion of cell temperature monitoring in immersion liquid cooling.

[0036] The embodiment of the present invention re-layouts and designs the existing liquid-cooled battery pack. The immersion coolant can be directly injected into the battery pack to immerse the module, which greatly improves the temperature consistency of the upper and lower parts of the single battery cell. The bottom of the liquid-cooled battery pack still adopts the existing cold plate design, but the flow channel design can be greatly simplified to make the cold plate simpler, the heat exchange effect is higher, and the power consumption is reduced. By adopting the EIS (Electrochemical Impedance Spectroscopy) technology of a single battery cell, the internal temperature of the battery cell can be monitored online, so that it is not affected by the external coolant, and the monitored temperature is more accurate, making it possible to manage the temperature in detail, and it is safer to monitor the thermal runaway battery cell in advance. At the same time, the safety advantage of the immersion type is retained, and fire protection is simplified.

[0037] The design and temperature management of the energy storage system in which the liquid-cooled battery pack is located in the embodiment of the present invention includes the following steps: (1) Complete the assembly of the battery module in the existing way, fix the FPC (Flexible Printed Circuit) collection board on it, complete the welding, and connect the battery cells in series and parallel, such as Figure 1As shown, the battery module includes end plates, battery cells, isolation strips between battery cells, and CCS (Cells Contact System, electrical connection structural parts) components, such as Figure 2 As shown, the FPC acquisition board has acquisition contacts and acquisition chips; (2) Reference Figure 1 , an isolation tape is pasted between adjacent cells or an isolation pad with pores or channels is used to allow the immersion liquid to flow over the surface of the cell; (3) Lay a heat-conducting pad on the bottom plate of the liquid-cooled battery pack to allow the coolant to flow freely; (4) Place the assembled battery module in the liquid-cooled battery pack as designed and secure it; (5) If Figure 3 As shown, taking two flow balancing layers as an example, the first flow balancing layer is placed and fixed, and the second flow balancing layer is placed and assembled with the first flow balancing layer and then fixed; both the first and second flow balancing layers have openings, and the hole diameter of the first flow balancing layer is greater than or equal to the hole diameter of the second flow balancing layer; the first flow balancing layer and the second flow balancing layer are tightly combined with the battery modules and the battery pack box to divide the battery pack into three layers; a gradient difference in flow velocity is formed between the three layers, so that when the immersion coolant is circulated, the immersion liquid in each part of the battery pack can flow evenly to avoid the formation of a fluid "short circuit" or "dead zone", so that the temperature in each part of the battery pack is uniform; (6) Reference Figure 3 A heating module for heating the immersion liquid is installed on the back of the first and second flow balancing layers; (7) Connect the modules and the total positive and negative wires in the package; (8) Install a liquid level sensor in the bag to monitor the liquid level in the bag, such as Figure 4 As shown; (9) Complete the connection of each communication harness; (10) Complete the connection of each pipeline. The water inlet of the immersion liquid is located above the second flow-balancing layer, and the water outlet of the immersion liquid is located below the first flow-balancing layer. The positions of the water inlet and outlet are as follows: Figure 5 As shown; (11) Install the completed battery pack on the cluster rack of the energy storage system; (12) Complete the connection of power cables and communication cables; (13) Complete the filling of coolant for each battery pack and ensure there is no leakage; (14) Complete the filling of the cold plate liquid cooling coolant and ensure there is no leakage; (15) Complete the installation and commissioning of the energy storage system.

[0038] (16) The relationship between the internal resistance of the EIS test and the internal temperature of all battery cells and the changes in the EIS spectrum during thermal runaway are obtained through the test method and imported into the BMS management system to monitor the internal temperature of the battery cells and warn of thermal runaway.

[0039] (17) The temperature management method of the embodiment of the present invention is used to implement a temperature management strategy for the battery cell: a first cooling strategy, a second cooling strategy, a first heating strategy, or a second heating strategy, and all strategies are different.

[0040] Figure 6 Flow chart of a temperature management method for a liquid-cooled battery pack according to an embodiment of the present invention.

[0041] like Figure 6 As shown, the temperature management method of the liquid-cooled battery pack includes the following steps S1 to S5, and the method can be applied to Figures 1 to 5 The structure shown.

[0042] S1, determine the working status of the battery cells in the liquid-cooled battery pack and collect the maximum temperature of the battery cells.

[0043] The working state of the battery cell includes charging, discharging or standby (to be charged or to be discharged) state.

[0044] Specifically, when the temperature of the battery cell needs to be managed through a liquid cooling structure, such as heat dissipation, cooling or heating, the current working status of the battery cell is first determined, and the EIS indirect temperature measurement method is used to obtain the internal temperature of the battery cell, and the highest temperature is selected as the maximum temperature of the battery cell.

[0045] S2, when the battery cell is in a charging or discharging state, executing a first cooling strategy according to the maximum temperature of the battery cell.

[0046] S3, when the battery cell is in a state to be charged or discharged, executing a second cooling strategy according to the highest temperature of the battery cell, wherein the second cooling strategy is different from the first cooling strategy.

[0047] Specifically, when the battery cell needs to be cooled and the battery cell is in a charging or discharging state, a first cooling strategy is executed according to the relationship between the maximum temperature of the battery cell and multiple temperatures, so as to perform cold plate liquid cooling and / or immersion liquid cooling; when cooling is needed and the battery cell is in a standby state, a second cooling strategy different from the first cooling strategy is executed according to the relationship between the maximum temperature of the battery cell and multiple temperatures, so as to perform cold plate liquid cooling and / or immersion liquid cooling. The temperature dimensions corresponding to the two cooling strategies can be different, so as to achieve cooling of battery cells in different states from multiple temperature dimensions.

[0048] S4, when the battery cell is in a state to be charged, executing a first heating strategy according to the highest temperature of the battery cell.

[0049] S5, when the battery cell is in a state to be discharged, executing a second heating strategy according to the highest temperature of the battery cell, wherein the second heating strategy is different from the first heating strategy.

[0050] Specifically, when the battery cell needs to be heated and the battery cell is in a state to be charged, a first heating strategy is executed according to the relationship between the highest temperature of the battery cell and multiple temperatures, so that the battery cell is heated by a cold plate liquid cooling structure and / or an immersion liquid cooling structure; when heating is required and the battery cell is in a state to be discharged, a second heating strategy different from the first heating strategy is executed according to the relationship between the highest temperature of the battery cell and multiple temperatures, so that the battery cell is heated by a cold plate liquid cooling structure and / or an immersion liquid cooling structure. The temperature dimensions corresponding to the two heating strategies can be different, thereby realizing the heating of battery cells in different states from multiple temperature dimensions.

[0051] Compared with the prior art, the embodiments of the present invention adopt different multi-dimensional temperature management strategies for battery cells in different states, which is easy to adjust and improves energy utilization and temperature management efficiency.

[0052] Therefore, the temperature management method of the liquid-cooled battery pack of the embodiment of the present invention adopts different temperature management strategies under different states of the battery cell, which is convenient for realizing multi-dimensional temperature management, can improve heat dissipation and heating efficiency, and avoid excessive waste of energy.

[0053] In one embodiment of the present invention, the liquid-cooled battery pack includes a cold plate liquid cooling structure for implementing cold plate liquid cooling and an immersion liquid cooling structure for implementing immersion liquid cooling.

[0054] In one example, step S2 executes a first cooling strategy according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell rises to a first control temperature, first turning on a cold plate liquid cooling structure for cold plate liquid cooling; when the maximum temperature of the battery cell rises to a second control temperature, maintaining the cold plate liquid cooling and turning on an immersion liquid cooling structure for immersion liquid cooling, so as to perform hybrid cooling, wherein the second control temperature is greater than the first control temperature; during the hybrid cooling process, when the maximum temperature of the battery cell drops back to the first drop-back temperature, first turning off the cold plate liquid cooling structure and maintaining the immersion liquid cooling; when the maximum temperature of the battery cell drops back to the second drop-back temperature, turning off the immersion liquid cooling structure to stop cooling, wherein the second drop-back temperature is lower than the first drop-back temperature.

[0055] The first control temperature and the second control temperature are the temperatures set in advance according to actual needs for cooling the battery cell in the working state. The first drop temperature and the second drop temperature refer to the temperatures set in advance according to actual needs for cooling the battery cell in the working state.

[0056] It should be noted that, in addition to the two in the present invention, the number of the control temperature and the fall temperature may also be three, four, etc., which can be set according to actual needs.

[0057] Specifically, if Figure 7 As shown, when the battery cell needs to be cooled, the working state of the battery cell is first determined, and the following first cooling strategy is executed when the battery cell is in the charging or discharging state. b Reach the first control temperature T 1 When the cold plate liquid cooling structure is turned on, the cold plate liquid cooling structure is turned on first. During the cold plate liquid cooling process, the cell temperature is collected in real time. When the highest temperature T b Continue to rise to the second control temperature T 2 When the temperature T b Gradually fall back to the first fall temperature T 3 , the second fall temperature T 4 Then, the cold plate type liquid cooling structure and the immersion type liquid cooling structure are closed in sequence to stop cooling.

[0058] In one example, step S3 executes a second cooling strategy according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is greater than a first preset temperature and less than or equal to a second preset temperature, turning on a cold plate liquid cooling structure for cold plate liquid cooling, wherein the second preset temperature is greater than the first preset temperature, and when the maximum temperature of the battery cell drops to a third drop temperature, turning off the cold plate liquid cooling structure; when the maximum temperature of the battery cell is greater than the second preset temperature, turning on the cold plate liquid cooling structure and the immersion liquid cooling structure for hybrid cooling, and when the maximum temperature of the battery cell drops to the third drop temperature, turning off the cold plate liquid cooling structure and the immersion cooling structure.

[0059] The first preset temperature and the second preset temperature are the temperatures for cooling the battery cell in the standby state set in advance according to actual needs. The third drop temperature refers to the temperature at which the battery cell drops during the cooling process of the battery cell in the standby state set according to actual needs. The third drop temperature may be different from the first and second drop temperatures.

[0060] Specifically, if Figure 8 As shown, when cooling is required and the battery cell is in standby mode, when the maximum temperature T b Greater than the first preset temperature T r and is less than or equal to the second preset temperature T k When the temperature T b Greater than the second preset temperature T kWhen the temperature T b Fall back to the third fall temperature T f Stop cooling when the temperature drops below 0.1°C.

[0061] In one example, step S4 executes a first heating strategy according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is lower than the first charging temperature, first starting the cold plate liquid cooling structure heating mode to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first charging temperature and lower than the second charging temperature, then starting the immersion liquid cooling structure heating mode to heat the battery cell; until the maximum temperature of the battery cell reaches the second charging temperature, the heating is stopped, wherein the second charging temperature is higher than the first charging temperature.

[0062] The first charging temperature and the second charging temperature are the temperatures set in advance according to actual needs for heating the battery cell in the state to be charged. The first charging temperature and the second charging temperature can be the temperatures at which the battery cell allows low rate charging and normal rate charging, respectively.

[0063] Among them, the cold plate liquid cooling structure heating mode refers to a mode of heating the coolant of the cold plate liquid cooling structure, and the immersion liquid cooling structure heating mode refers to a mode of heating the immersion liquid of the immersion liquid cooling structure.

[0064] Specifically, in a low temperature environment, the system needs to be preheated, such as Fig. 9 As shown, if it is in the state of waiting to be charged, it draws power from the external power grid. When the maximum temperature of the battery cell T b Less than the first charging temperature T c1 (the lowest temperature that the battery cell allows for low-rate charging), first start the cold plate liquid cooling structure heating mode to heat the battery cell. During the heating process, collect the battery cell temperature in real time. When T b Greater than or equal to the first charging temperature T c1 and is less than the second charging temperature T c2 When the temperature of the battery cell is charged at a normal rate, the heating module in the battery pack is started to heat the immersion liquid while the battery cell is charged at a low rate. The temperature reaches T quickly through multi-element heating and self-heating of the battery cell. c2 After that, normal charging is carried out, and then the cold plate heating and heating module heating can be turned off as needed.

[0065] In one example, step S5 executes a second heating strategy according to the maximum temperature of the battery cell, including: when the maximum temperature of the battery cell is lower than the first discharge temperature, first starting the cold plate liquid cooling structure heating mode to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and lower than the second discharge temperature, then starting the immersion liquid cooling structure heating mode to heat the battery cell, until the maximum temperature of the battery cell reaches the second discharge temperature, then stopping the heating, wherein the second discharge temperature is greater than the first discharge temperature; when the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and lower than the second discharge temperature, first starting the immersion liquid cooling heating mode to heat the battery cell, then starting the cold plate liquid cooling structure heating mode to heat the battery cell, until the maximum temperature of the battery cell reaches the second discharge temperature, then stopping the heating.

[0066] The first discharge temperature and the second discharge temperature are the temperatures set in advance according to actual needs to control the heating of the battery cell in the state to be discharged. The first discharge temperature and the second discharge temperature can be the temperatures at which the battery cell allows low rate discharge and normal rate discharge, respectively.

[0067] Specifically, in a low temperature environment, the system needs to be preheated, such as Fig.10 As shown, if it is in the state of waiting to be discharged, when the maximum temperature of the battery cell T b Less than the first discharge temperature T d1 (the lowest temperature that the battery cell allows for low-rate discharge), the cold plate liquid cooling structure heating mode is started by external power supply, and the temperature rises to the first discharge temperature T d1 and has not reached the second discharge temperature T d2 (normal discharge rate temperature allowed by the battery cell), the heating module in the battery pack is started to heat the immersion liquid (powered by the discharge of the battery cell at this time), until the second discharge temperature is reached, and then the heating is stopped; when the battery cell is in the state of waiting to be discharged, when the highest temperature T b Between the first discharge temperature T d1 and the second discharge temperature T d2 When the temperature of the battery cell reaches the second discharge temperature T d2 Then stop heating as needed.

[0068] Compared with the existing hybrid cooling technology, the present invention mainly solves the following technical problems: Eliminating the heat dissipation fins saves product complexity, reduces internal space, and improves space utilization; increasing the circulation of immersion coolant in the liquid-cooled battery pack and improving its flow uniformity, making the temperature in the liquid-cooled battery pack more uniform and the battery cells more consistent; combining the internal circulation of the liquid-cooled battery pack with the external circulation, taking into account the high efficiency and uniformity of heat dissipation as well as the convenience of maintenance, and allowing for separate maintenance of a single liquid-cooled battery pack; adding a heating module for heating the immersion liquid to make the heating more efficient, and combining the self-heating of the battery cell and the heating of the circulating coolant to more quickly reach full power operating conditions at extremely low temperatures, saving energy; adopting a multi-dimensional temperature management strategy to achieve higher heat dissipation and heating efficiency and avoid excessive energy waste.

[0069] The following is a specific example to illustrate the liquid-cooled battery pack and the temperature management method thereof according to an embodiment of the present invention.

[0070] (1) Assemble a module consisting of 13 314Ah cells in the existing manner ( Figure 1 ), put the FPC acquisition board ( Figure 2 ) are fixed on it and welding is completed to connect the cells in series and parallel; (2) Three isolation strips are used between adjacent cells to allow the immersion cooling liquid to flow through the cell surface; (3) Lay a heat-conducting pad on the bottom plate of the liquid-cooled battery pack to allow the coolant to flow freely; (4) Place the four modules assembled above into the liquid-cooled battery pack according to the design and fix them; (5) Reference Figure 3 , taking two flow balancing layers as an example, the first flow balancing layer is placed and fixed, the second flow balancing layer is placed and assembled with the first flow balancing layer and then fixed; both the first and second flow balancing layers have openings, and the hole diameter of the first flow balancing layer is greater than or equal to the hole diameter of the second flow balancing layer; the first flow balancing layer and the second flow balancing layer are tightly combined with the battery modules and the battery pack box to divide the battery pack into three layers; a gradient difference in flow velocity is formed between the three layers, so that when the immersion coolant is circulated, the immersion liquid in each part of the battery pack can flow evenly to avoid the formation of a fluid "short circuit" or "dead zone", so that the temperature in each part of the battery pack is uniform; (6) Reference Figure 3 A heating module for heating the immersion liquid is installed on the back of the first and second flow balancing layers; (7) Connect the modules and the total positive and negative wires in the package; (8) Install the liquid level sensor in the bag to monitor the liquid level in the bag ( Figure 4 ); (9) Complete the connection of each communication harness and assemble it into a combined liquid-cooled battery pack; (10) Complete the connection of each pipeline. The water inlet of the immersion liquid is located above the second flow-balancing layer, and the water outlet of the immersion liquid is located below the first flow-balancing layer. The water inlet and outlet are as follows: Figure 5 As shown; (11) Install the 8 completed battery packs on the cluster rack of the energy storage system; (12) Complete the connection of power cables and communication cables; (13) Complete the filling of coolant for each battery pack and ensure there is no leakage; (14) Complete the filling of the cold plate liquid cooling coolant and ensure there is no leakage; (15) Complete the installation and commissioning of the energy storage system; (16) The relationship between the internal resistance of the EIS (Electrochemical Impedance Spectroscopy) test and the internal temperature of all battery cells and the changes in the EIS spectrum during thermal runaway are obtained through testing methods and imported into the BMS management system to monitor the internal temperature of the battery cells and provide early warning of thermal runaway; (17) The temperature management method according to the embodiment of the present invention executes a temperature management strategy: a first cooling strategy, a second cooling strategy, a first heating strategy or a second heating strategy, where the strategies are different.

[0071] First cooling strategy: When the cell has the highest temperature T b Reach T 1 =27℃, first turn on the liquid cooler to cool through the liquid cooling plate. When the temperature continues to rise to T 2 =32℃, then turn on the battery pack external circulation to cool and equalize the temperature through immersion liquid. When the temperature gradually drops to T 3 =30℃、T 4 =25℃, then turn off the liquid cooler and battery pack external circulation in turn.

[0072] Second cooling strategy: When the maximum temperature of the battery cell is greater than the temperature T in standby mode r =30℃, turn on the liquid cooling plate for cooling. When the maximum cell temperature T b Greater than T k =35℃, then turn on the battery pack external circulation cooling and temperature equalization. When the maximum temperature of the battery cell drops to T f = Below 27℃, turn off cooling.

[0073] The first heating strategy: If the battery is in the charging state, it will be powered from the external power grid. When the battery cell temperature is lower than the first preset temperature T c1 =0℃ (the lowest temperature that the battery cell allows for low-rate charging), the cold plate liquid cooling structure heating mode is started to heat the battery cell; when it exceeds T c1 And less than T c2=10℃ (the temperature of the battery cell when it is charged at a normal rate), the heating module in the battery pack is activated while the battery cell is charged at a low rate, and the temperature reaches T quickly through multi-element heating and self-heating of the battery cell. c2 =18℃, normal charging is carried out, and then the cold plate heating and heating module heating can be turned off as needed.

[0074] Second heating strategy: If it is in the state of waiting to discharge, when the maximum temperature of the battery cell is less than T d1 = -30℃, the cold plate heating mode is started by external power supply, and the temperature rises to the lowest temperature T that the battery cell allows for low-rate discharge. d1 = -30℃, then start the heating module in the liquid-cooled battery to heat the immersion liquid (at this time, the battery cell is discharged for power); when the maximum temperature of the battery cell is between T d1 and T d2 = -20℃ (normal discharge rate temperature allowed by the battery cell), first start the heating module to heat the immersion liquid, then start the cold plate heating. At this time, the power is supplied by the battery cell discharge. When the battery cell temperature reaches T d2 After that, stop heating as needed and operate normally.

[0075] In summary, the temperature management method proposed in the embodiment of the present invention has the following advantages: Different multi-dimensional temperature management strategies are adopted under different states of the battery cell, which is easy to adjust and improves energy utilization and temperature management efficiency; the method of combining immersion liquid cooling and cold plate liquid cooling retains the advantages of high cooling efficiency and uniform temperature, and the immersion coolant does not circulate, avoiding the problem of redesigning the cooling system and high complexity; the method of combining immersion liquid cooling and cold plate liquid cooling utilizes the existing mature cold plate liquid cooling circulation cooling system, while solving the problem of uneven temperature of cold plate single battery cells, while improving cooling efficiency and reducing energy consumption; the use of internal equal flow design of the battery pack and external circulation of the immersion liquid solves the problem of internal temperature unevenness caused by the lack of immersion liquid flow The problem of high temperature in the whole battery pack or a certain position; the heating module is used to directly heat the immersion liquid, which is different from the continuous heating of the cold plate or the auxiliary heating inside the battery cell. It can heat all the battery cells efficiently and evenly, especially those that need to operate in off-grid mode and cooperate with the low-rate discharge of the battery cell to quickly increase the temperature of the battery cell to the normal discharge condition, saving electricity loss; simplifying fire protection, the high safety characteristics of immersion liquid cooling make it unnecessary to have a complex fire protection plan at the battery pack level like the existing solution, only a simple cabinet-level fire protection is required, which greatly reduces the complexity and difficulty of fire protection; the use of combined liquid cooling can achieve efficient heat dissipation and simplify the system, while the battery pack and the system are simpler and more compact, smaller in size, and occupy less space.

[0076] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limitations on the present invention, and those of ordinary skill in the art can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A temperature management method for a liquid-cooled battery pack, characterized in that: The following steps are involved: Determine the working state of the battery cells in the liquid-cooled battery pack and collect the maximum temperature of the battery cells; When the battery cell is in a charging or discharging state, executing a first cooling strategy according to a maximum temperature of the battery cell; When the battery cell is in a state to be charged or discharged, executing a second cooling strategy according to the highest temperature of the battery cell, wherein the second cooling strategy is different from the first cooling strategy; When the battery cell is in a state to be charged, executing a first heating strategy according to the highest temperature of the battery cell; When the battery cell is in a state to be discharged, a second heating strategy is executed according to a maximum temperature of the battery cell, wherein the second heating strategy is different from the first heating strategy.

2. The temperature management method of a liquid-cooled battery pack according to claim 1, characterized in that: The liquid-cooled battery pack includes a cold plate liquid cooling structure and an immersion liquid cooling structure.

3. The temperature management method of a liquid-cooled battery pack according to claim 2, characterized in that: Executing a first cooling strategy according to the maximum temperature of the battery cell includes: When the highest temperature of the battery core rises to a first control temperature, the cold plate liquid cooling structure is first turned on for cold plate liquid cooling; when the highest temperature of the battery core rises to a second control temperature, the cold plate liquid cooling is maintained and the immersion liquid cooling structure is turned on for immersion liquid cooling, so as to perform hybrid cooling, wherein the second control temperature is greater than the first control temperature; During the hybrid cooling process, when the maximum temperature of the battery cell drops back to a first drop-back temperature, the cold plate liquid cooling structure is first closed and the immersion liquid cooling is maintained; when the maximum temperature of the battery cell drops back to a second drop-back temperature, the immersion liquid cooling structure is closed to stop cooling, wherein the second drop-back temperature is lower than the first drop-back temperature.

4. The temperature management method of a liquid-cooled battery pack according to claim 2, characterized in that: Executing a second cooling strategy according to the maximum temperature of the battery cell includes: When the maximum temperature of the battery cell is greater than a first preset temperature and less than or equal to a second preset temperature, the cold plate liquid cooling structure is turned on for cold plate liquid cooling, wherein the second preset temperature is greater than the first preset temperature, and when the maximum temperature of the battery cell drops back to a third drop temperature, the cold plate liquid cooling structure is turned off; When the maximum temperature of the battery cell is greater than the second preset temperature, the cold plate liquid cooling structure and the immersion liquid cooling structure are turned on to perform hybrid cooling. When the maximum temperature of the battery cell drops back to the third drop temperature, the cold plate liquid cooling structure and the immersion cooling structure are turned off to stop cooling.

5. The temperature management method of a liquid-cooled battery pack according to claim 2, characterized in that: Executing a first heating strategy according to the maximum temperature of the battery cell includes: When the maximum temperature of the battery cell is lower than the first charging temperature, the cold plate liquid cooling structure heating mode is first started to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first charging temperature and lower than the second charging temperature, the immersion liquid cooling structure heating mode is started to heat the battery cell; the heating is stopped when the maximum temperature of the battery cell reaches the second charging temperature, wherein the second charging temperature is higher than the first charging temperature.

6. The temperature management method of a liquid-cooled battery pack according to claim 2, characterized in that: Executing a second heating strategy according to the maximum temperature of the battery cell includes: When the maximum temperature of the battery cell is lower than the first discharge temperature, the cold plate liquid cooling structure heating mode is first started to heat the battery cell; when the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and lower than the second discharge temperature, the immersion liquid cooling structure heating mode is started to heat the battery cell until the maximum temperature of the battery cell reaches the second discharge temperature, and the heating is stopped, wherein the second discharge temperature is higher than the first discharge temperature; When the maximum temperature of the battery cell is greater than or equal to the first discharge temperature and less than the second discharge temperature, the immersion liquid cooling heating mode is first started to heat the battery cell, and then the cold plate liquid cooling structure heating mode is started to heat the battery cell until the maximum temperature of the battery cell reaches the second discharge temperature, and then the heating is stopped.

7. The temperature management method of a liquid-cooled battery pack according to claim 2, characterized in that: The immersion liquid cooling structure includes multiple flow equalizing layers, the battery modules in the battery pack include multiple layers, each of the flow equalizing layers is located between the battery modules in adjacent layers, the flow equalizing layers are provided with openings, the diameters of the openings in the flow equalizing layers are equal or decrease sequentially from bottom to top, the water inlet of the immersion liquid in the immersion liquid cooling structure is located above the uppermost flow equalizing layer, and the water outlet of the immersion liquid is located below the lowermost flow equalizing layer.

8. The temperature management method of a liquid-cooled battery pack according to claim 7, characterized in that: A heating module for heating the immersion liquid is installed at the back of the flow-distributing layer.

9. The temperature management method of a liquid-cooled battery pack according to claim 7, characterized in that: The immersion liquid cooling structure also includes an isolation zone arranged between adjacent battery cells.

10. The temperature management method of a liquid-cooled battery pack according to claim 2 or 7, characterized in that: The cold plate type liquid cooling structure includes a liquid cooling plate and a thermal pad arranged at the bottom of the liquid-cooled battery pack.

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