Immersed cooling system and method for traction battery pack system

Abstract

The present disclosure provides a submerged cooling system and method for a traction battery pack system. A submerged cooling system for managing thermal energy levels within a traction battery pack system is provided. An exemplary submerged cooling system may include a flow control valve configured to control a flow of a cooling fluid (e.g., a dielectric fluid) through a primary closed-loop cooling circuit or a secondary closed-loop cooling circuit of the submerged cooling system to thermally manage battery modules of a battery pack assembly. The control module may control a position of the flow control valve based at least on a temperature of the cooling fluid exiting the battery pack assembly. When the flow control valve directs cooling fluid through the auxiliary closed-loop cooling circuit, a portion of the main closed-loop cooling circuit is retained for providing a dedicated gas exit flow path for venting battery exhaust byproducts from the battery pack assembly.

Description

Technical Field

[0001] The present disclosure relates generally to electrified vehicle traction battery pack systems, and more particularly to an immersion cooling system capable of managing battery cell thermal energy levels under multiple operating conditions of the traction battery pack system. Background Art

[0002] Electrified vehicles include a traction battery pack for powering the vehicle's electric motor and other electrical loads. The traction battery pack includes multiple battery cells and various other battery internal components that support electric vehicle propulsion. Summary of the Invention

[0003] According to an exemplary aspect of the present disclosure, a traction battery pack system includes, inter alia: a battery pack assembly, the battery pack assembly including battery modules housed within a housing assembly; a primary closed-loop cooling circuit, the primary closed-loop cooling circuit establishing a first flow path of an immersion cooling system; an auxiliary closed-loop cooling circuit, the auxiliary closed-loop cooling circuit establishing a second flow path of the immersion cooling system; a flow control valve, the flow control valve being arranged to control the flow of a cooling fluid along the first flow path or the second flow path; and a control module programmed to control a position of the flow control valve based on a temperature of the cooling fluid exiting the battery pack assembly.

[0004] In a further non-limiting embodiment of the foregoing traction battery pack system, a temperature sensor is positioned within or near an outlet port of the battery pack assembly.

[0005] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the cooling fluid is a dielectric fluid.

[0006] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the control module is programmed to command the flow control valve to a first position to direct the cooling fluid along the first flow path when the temperature of the cooling fluid is less than or equal to a predefined temperature threshold, and is further programmed to command the flow control valve to a second position to direct the cooling fluid along the second flow path when the temperature of the cooling fluid is greater than the predefined temperature threshold.

[0007] In another non-limiting embodiment of any of the foregoing traction battery pack systems, the first flow path extends through both a first battery internal fluid channel and a second battery internal fluid channel of the battery pack assembly. The second flow path extends through the first battery internal fluid channel of the battery pack assembly but does not extend through the second battery internal fluid channel.

[0008] In another non-limiting embodiment of any of the foregoing traction battery pack systems, when the temperature of the cooling fluid is greater than the predefined temperature threshold, the second internal fluid passage establishes a dedicated gas exit flow path for exhausting battery exhaust byproducts from the battery pack assembly.

[0009] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the first battery internal fluid channel extends between a bottom side of the plurality of battery cells of the battery module and the housing tray of the housing assembly, and the second battery internal fluid channel extends between a top side of the plurality of battery cells of the battery module and the housing cover of the housing assembly.

[0010] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the primary closed-loop cooling circuit of the immersion cooling system includes a first inlet port, a first battery internal fluid passage, a first outlet port, a second inlet port, an external fluid passage connected between the first outlet port and the second inlet port, a second battery internal fluid passage, and a second outlet port.

[0011] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the auxiliary closed-loop cooling circuit of the immersion cooling system includes the first inlet port, the first battery internal fluid channel, the first outlet port, and a return line.

[0012] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the immersion cooling system further includes a reservoir fluidly connected to the first inlet port.

[0013] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the immersion cooling system further includes a pump disposed between the reservoir and the first inlet port.

[0014] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the reservoir is positioned on a side of the battery pack assembly opposite the flow control valve.

[0015] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, a first heat exchanger is fluidly connected to the external fluid passage, and a second heat exchanger is fluidly connected to the return line.

[0016] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the first position of the flow control valve is configured to divert the cooling fluid into the external fluid passage of the primary closed-loop cooling circuit, and the second position of the flow control valve is configured to divert the cooling fluid into the return line of the auxiliary closed-loop cooling circuit.

[0017] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the immersion cooling system further includes a liquid-gas separator fluidly connected to the second outlet port.

[0018] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the liquid-gas separator is positioned on a side of the battery pack assembly opposite the flow control valve.

[0019] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, a temperature sensor is positioned within or proximate to the second outlet port.

[0020] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the flow control valve is positioned external to the housing assembly of the battery pack assembly.

[0021] In a further non-limiting embodiment of any of the foregoing traction battery pack systems, the flow control valve is positioned between an outlet port of the battery pack assembly and a heat exchanger of the primary closed-loop cooling circuit.

[0022] A method according to another exemplary aspect of the present disclosure includes, inter alia, circulating a cooling fluid along a first flow path provided by a primary closed-loop cooling circuit of an immersion cooling system; monitoring a temperature of the cooling fluid as it travels along the first flow path; and, when the temperature exceeds a predefined temperature threshold, circulating the cooling fluid along a second flow path provided by a secondary closed-loop cooling circuit of the immersion cooling system. Circulating the cooling fluid along the second flow path includes preventing the cooling fluid from passing through a portion of the first flow path of the primary closed-loop cooling circuit.

[0023] The embodiments, examples and alternatives of the preceding paragraphs, claims or following description and drawings (including any of their various aspects or corresponding individual features) may be taken independently or in any combination. Features described in conjunction with one embodiment apply to all embodiments unless such features are incompatible.

[0024] The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description.The drawings that accompany the detailed description can be briefly described as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An electrified vehicle is schematically shown.

[0026] Figure 2 Schematic diagram of an immersion cooling system for a traction battery pack system.

[0027] Figure 3 Schematically shows Figure 2 The first operating mode of the immersion cooling system.

[0028] Figure 4 Schematically shows Figure 2 Second operating mode of the immersion cooling system. DETAILED DESCRIPTION

[0029] The present disclosure details an immersion cooling system for managing thermal energy levels within a traction battery pack system. An exemplary immersion cooling system may include a flow control valve configured to control the flow of a cooling fluid (e.g., a dielectric fluid) through a primary closed-loop cooling circuit or an auxiliary closed-loop cooling circuit of the immersion cooling system to thermally manage battery modules of a battery pack assembly. A control module may control the position of the flow control valve based at least on the temperature of the cooling fluid exiting the battery pack assembly. When the flow control valve directs the cooling fluid through the auxiliary closed-loop cooling circuit, a portion of the primary closed-loop cooling circuit is reserved for providing a dedicated gas exit flow path for exhausting battery exhaust byproducts from the battery pack assembly. These and other features are discussed in more detail in the following paragraphs of this specific embodiment.

[0030] Figure 1 An electrified vehicle 10 is schematically shown. The electrified vehicle 10 may include any type of electrified powertrain. In an embodiment, the electrified vehicle 10 is a battery electric vehicle (BEV). However, the concepts described herein are not limited to BEVs and may be extended to other electrified vehicles, including but not limited to hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles, and the like. Thus, although not specifically shown in the exemplary embodiment, the powertrain of the electrified vehicle 10 may be equipped with an internal combustion engine, which may be employed alone or in combination with other power sources to propel the electrified vehicle 10.

[0031] In the illustrated embodiment, the electrified vehicle 10 is depicted as an automobile. However, the electrified vehicle 10 may alternatively be a sport utility vehicle (SUV), a van, a pickup truck, or any other vehicle configuration. Although specific component relationships are shown in the figures of the present disclosure, the illustrations are not intended to limit the present disclosure. The placement and orientation of the various components of the electrified vehicle 10 are shown schematically and may vary within the scope of the present disclosure. In addition, the various figures accompanying the present disclosure are not necessarily drawn to scale, and some features may be exaggerated or minimized to emphasize certain details of a particular component or system.

[0032] In the illustrated embodiment, the electrified vehicle 10 is a pure electric vehicle that is propelled solely by electricity, such as by one or more electric machines 12, without assistance from an internal combustion engine. The electric machines 12 can operate as electric motors, generators, or both. The electric machines 12 receive electrical power and can convert the power into torque that is used to drive one or more wheels 14 of the electrified vehicle 10.

[0033] A voltage bus 16 electrically couples the electric machine 12 to a traction battery pack system 18. The traction battery pack system 18 is an exemplary electrified vehicle battery. The traction battery pack system 18 may include a high-voltage traction battery pack assembly comprising a plurality of battery cells capable of outputting electrical power to power the electric machine 12 and / or other electrical loads of the electrified vehicle 10. Other types of energy storage devices and / or output devices may alternatively or additionally be used to power the electrified vehicle 10.

[0034] The traction battery pack system 18 may be secured to an underbody 20 of the electrified vehicle 10. However, the traction battery pack system 18 may be located elsewhere on the electrified vehicle 10 within the scope of the present disclosure.

[0035] Figure 2 Shown with Figure 1 1 and 2. The traction battery pack system 18 of the electrified vehicle 10 may include one or more battery modules 22 (e.g., battery assemblies or groups of rechargeable battery cells 24) capable of outputting electrical power to power the electric machine 12 and / or other electrical loads of the electrified vehicle 10.

[0036] The battery cells 24 may be stacked side by side along a stack axis to form groups of battery cells 24 , sometimes referred to as “cell stacks.” The total number of battery modules 22 and battery cells 24 provided within the traction battery pack system 18 is not intended to limit the present disclosure.

[0037] In an embodiment, the battery cells 24 of each battery module 22 are prismatic lithium-ion cells. However, within the scope of the present disclosure, battery cells having other geometries (cylindrical, pouch, etc.), other chemistries (nickel metal hydride, lead acid, etc.), or both may alternatively be utilized.

[0038] The battery modules 22 and various other battery internal components (e.g., bus electrical center, battery electrical control module, wiring, connectors, etc.) may be housed within a housing assembly 28 of the traction battery pack system 18. The battery modules 22 and housing assembly 28 may together establish a battery pack assembly 25 of the traction battery pack system 18.

[0039] The battery modules 22 may be arranged in one or more rows within the housing assembly 28. Figure 2 Only a single battery module 22 having twelve battery cells 24 is shown, but other configurations are possible. Therefore, it should be understood that the traction battery pack system 18 may include a greater number of battery modules 22 and / or a greater or lesser number of battery cells 24 within the scope of the present disclosure.

[0040] Although shown schematically, the housing assembly 28 can embody a multi-piece design that includes a housing cover 26 and a housing tray 30 that combine to create an interior for housing the battery modules 22. The size, shape, and overall configuration of the housing assembly 28 are not intended to be limiting of the present disclosure. In an embodiment, the housing assembly 28 provides a sealed enclosure around the battery modules 22 and other internal battery components of the battery pack assembly 25.

[0041] The traction battery pack system 18 may further include an immersion cooling system 32. As described in further detail below, the immersion cooling system 32 may include a primary closed-loop cooling circuit 34 and an auxiliary closed-loop cooling circuit 36 ​​that are arranged to thermally manage the battery modules 22 and to manage battery exhaust gases and other byproducts during different operating conditions of the traction battery pack system 18. Although shown schematically, the various subcomponents of the immersion cooling system 32 may be fluidly interconnected by various conduits or channels, such as tubes, hoses, pipes, and the like.

[0042] The immersion cooling system 32 can be configured to directly contact various surfaces of the battery cells 24 by circulating a cooling fluid F along a flow path established by the primary closed-loop cooling circuit 34 or the auxiliary closed-loop cooling circuit 36. In an embodiment, the cooling fluid F is a dielectric fluid. However, other fluids may be utilized within the scope of the present disclosure.

[0043] The flow control valve 38 may be configured to control the flow of the cooling fluid F along the respective flow paths provided by the primary closed-loop cooling circuit 34 or the auxiliary closed-loop cooling circuit 36 ​​based on the current operating conditions of the traction battery pack system 18. The flow control valve 38 may be a multi-position solenoid valve (e.g., a three-way valve) or any other suitable type of electrically controlled valve.

[0044] The main closed-loop cooling circuit 34 of the immersion cooling system 32 may include a first inlet port 40, a first internal battery fluid passage 42, a first outlet port 44, a second inlet port 46, a second internal battery fluid passage 48, and a second outlet port 50. The first internal battery fluid passage 42 may extend between a bottom side 54 of the battery cells 24 of the battery module 22 and the housing tray 30, and the second internal battery fluid passage 48 may extend between a top side 52 of the battery cells 24 of the battery module 22 and the housing cover 26. An external fluid passage 56 may be connected between the first outlet port 44 and the second inlet port 46. The external fluid passage 56 may be fluidly connected to a flow control valve 38 and a first heat exchanger 58 (e.g., a first fluid-to-air heat exchanger), both of which are disposed outside the housing assembly 28 of the battery pack assembly 25.

[0045] The first inlet port 40 can be fluidly connected to a reservoir 60 configured to store cooling fluid F. A pump 62 can be operated to selectively circulate the cooling fluid F through the respective flow paths of the primary closed-loop cooling circuit 34 or the auxiliary closed-loop cooling circuit 36. In an embodiment, the pump 62 is located between the reservoir 60 and the first inlet port 40. However, it is within the scope of the present disclosure that the pump 62 can be located elsewhere. It is within the scope of the present disclosure that the pump 62 can be an electric fluid pump or another type of pump.

[0046] The reservoir 60 and pump 62 may both be located outside of the housing assembly 28 of the battery pack assembly 25. In an embodiment, the reservoir 60 and pump 62 are located on a side of the housing assembly 28 opposite the flow control valve 38 and the first heat exchanger 58.

[0047] The auxiliary closed-loop cooling circuit 36 ​​of the immersion cooling system 34 may include a first inlet port 40, a first battery internal fluid channel 42, a first outlet port 44, and a return line 72. Some paths of the immersion cooling system 34 (e.g., the first inlet port 40, the first battery internal fluid channel 42, and the first outlet port 44) are therefore shared as part of the main closed-loop cooling circuit 34 and the auxiliary closed-loop cooling circuit 36. The return line 72 can be connected between the flow control valve 38 and the reservoir 60. A second heat exchanger 74 (e.g., a second fluid-to-air heat exchanger) can be provided in the return line 72. Both the return line 72 and the second heat exchanger 74 are provided outside the housing assembly 28 of the battery pack assembly 25.

[0048] As the cooling fluid F circulates along the flow path provided by the primary closed-loop cooling circuit 34, the pump 62 can be operated to selectively force the cooling fluid F through the first inlet port 40 and then through the first internal battery fluid passage 42. As the cooling fluid F flows through the first internal battery fluid passage 42, the cooling fluid F can pick up heat from the battery cells 24 via convective heat transfer. The cooling fluid F can then exit the battery pack assembly 25 through the first outlet port 44. The flow control valve 38 can then direct the cooling fluid F into the external fluid passage 56. The cooling fluid F can then pass from within the external fluid passage 56 through the first heat exchanger 58. The thermal energy picked up from the battery cells 24 while passing through the first internal battery fluid passage 42 can be transferred from the cooling fluid F to ambient air within the first heat exchanger 58.

[0049] The cooling fluid F may then flow through the second inlet port 46 before entering the second battery internal fluid channel 48. As the cooling fluid F flows through the second battery internal fluid channel 48, the cooling fluid F may pick up additional heat from the battery cells 24 through convective heat transfer. The cooling fluid F may then exit the second battery internal fluid channel 48 through the second outlet port 50.

[0050] The second outlet port 50 can be fluidly connected to a gas-liquid separator 64. Gas can be separated from the cooling fluid F within the gas-liquid separator 64 and can be exhausted to the atmosphere through a gas outlet 66 as schematically shown at arrow 68. As schematically shown, the gas-liquid separator 64 can be located outside the housing assembly 28 of the battery pack assembly 25 and can be positioned on a side of the housing assembly 28 opposite the first heat exchanger 58 and the flow control valve 38. The degassed cooling fluid F can flow back to the reservoir 60 within a connecting line 70 that is fluidly connected to both the gas-liquid separator 64 and the reservoir 60.

[0051] As the cooling fluid F circulates along the flow path provided by the auxiliary closed-loop cooling circuit 36, the pump 62 can be operated to selectively force the cooling fluid F through the first inlet port 40 and then into the first internal battery fluid passage 42. As the cooling fluid F flows through the first internal battery fluid passage 42, the cooling fluid F can extract heat from the battery cells 24 via convective heat transfer. The cooling fluid F can exit the first internal battery fluid passage 42 through the first outlet port 44. The flow control valve 38 can then direct the cooling fluid F into the return line 72. From within the return line 72, the cooling fluid F can pass through the second heat exchanger 74. The thermal energy extracted from the battery cells 24 while passing through the first internal battery fluid passage 42 can be transferred from the cooling fluid F to the ambient air within the second heat exchanger 74 before returning the cooling fluid F to the reservoir 60. Notably, the cooling fluid F does not pass through the second internal battery fluid passage 48 while circulating through the auxiliary closed-loop cooling circuit 36.

[0052] The immersion cooling system 32 may also include one or more temperature sensors 76 and a control module 78. The temperature sensor 76 may be configured to sense the temperature of the cooling fluid F. In an embodiment, the temperature sensor 76 is disposed within or near the second outlet port 50. Thus, the temperature sensor 76 may be arranged to sense the temperature of the cooling fluid F exiting the housing assembly 28 of the battery pack assembly 25.

[0053] The control module 78 can be operably connected to the pump 62, the flow control valve 38, and the temperature sensor 76, and can be programmed to control the operation of the immersion cooling system 32 to thermally manage the battery modules 22 of the traction battery pack system 18. The control module 78 can include both hardware and software and can be part of an overall vehicle control system, such as a vehicle system controller (VSC), or alternatively, a standalone controller or set of controllers separate from the VSC. Therefore, it should be understood that within the scope of the present disclosure, the control module 78 and one or more additional controllers operably coupled thereto may be collectively referred to as a "control module."

[0054] The control module 78 can be programmed with executable instructions for interfacing with and commanding the operation of various components of the immersion cooling system 32 as part of a control strategy for controlling the flow path of the cooling fluid F. The control module 78 can include a processor 80 and non-transitory memory 82 for executing various control strategies and modes associated with the immersion cooling system 32. The processor 80 can be a custom or commercially available processor, a central processing unit (CPU), or generally any device for executing software instructions. The memory 82 can include any one or a combination of volatile memory elements and / or non-volatile memory elements. The processor 80 can be operably coupled to the memory 82 and can be configured to execute one or more programs stored in the memory 82 based on various inputs received from other devices associated with the immersion cooling system 32 (e.g., inputs from the temperature sensor 76).

[0055] The temperature sensor 76 can be configured to periodically provide an input signal to the control module 78 that is indicative of the temperature of the cooling fluid F exiting the battery pack assembly 25 through the second outlet port 50. In response to receiving the input signal, the control module 78 can control the position of the flow control valve 38 to direct the cooling fluid F along a desired flow path to thermally manage the battery cells 24 and / or respond to a thermal event that may occur within one or more of the battery cells 24. A battery thermal event may occur, for example, during an overcharge condition, an overdischarge condition, or other condition, and may cause one or more of the battery cells 24 to emit battery exhaust byproducts, which may include gases, effluent particulates, and / or other exhaust byproducts.

[0056] Figure 3 A first operating mode of the immersion cooling system 32, which can be controlled by the control module 78, is schematically illustrated. The first operating mode can be considered a default mode for the immersion cooling system 32 and can occur when the temperature input signal received from the temperature sensor 76 indicates that the temperature of the cooling fluid F is less than or equal to a predefined temperature threshold (e.g., approximately 150 degrees Celsius or some other suitable temperature selected based on design-specific factors). When this occurs, the control module 78 can command the flow control valve 38 to a first position to direct the cooling fluid F along a first flow path 99 provided by the primary closed-loop cooling circuit 34. Thus, the cooling fluid F can flow through both the first and second internal battery fluid channels 42, 48 to thermally manage the battery cells 24 of the battery module 22 during normal operating conditions of the traction battery pack system 18. Notably, during the first operating mode, the flow of the cooling fluid F into the return line 72 of the auxiliary closed-loop cooling circuit 36 ​​is prevented.

[0057] exist Figure 4Schematically illustrated in FIGURE 2 is a second operating mode of the immersion cooling system 32 that can be commanded by the control module 78. The second operating mode can be specifically adapted to respond to thermal events that may occur within one or more of the battery cells 24 of the battery module 22. For example, when the temperature input signal received from the temperature sensor 76 indicates a temperature greater than or equal to a predefined temperature threshold (e.g., approximately 150 degrees Celsius or some other suitable temperature selected based on design-specific factors), the control module 78 can command the flow control valve 38 to a second position for directing the cooling fluid F along a second flow path 199 provided by the auxiliary closed-loop cooling circuit 36. Thus, the cooling fluid F can flow only through the first internal battery fluid passage 42, and not through the second internal battery fluid passage 48, to thermally manage the battery cells 24. Notably, during the second operating mode, the flow control valve 38 prevents the flow of the cooling fluid F from entering the external fluid passage 56 of the primary closed-loop cooling circuit 34.

[0058] Because the cooling fluid F does not circulate through the second battery internal fluid passage 48 during the second operating mode, the second battery internal fluid passage 48 can provide a dedicated gas exit flow path 299 for exhausting battery exhaust byproducts V released from one or more of the battery cells 24 of the battery pack assembly 25 during a battery thermal event. Thus, during a battery thermal event that requires the immersion cooling system to operate in the second operating mode, excessive pressure buildup inside the housing assembly 28 of the battery pack assembly 25 can be prevented.

[0059] The cell exhaust byproducts V may travel from the second internal fluid passage 48 through the second outlet port 50. The cell exhaust byproducts V may be exhausted to the atmosphere through the gas outlet 66 of the liquid-gas separator 64, as schematically shown at arrow 84.

[0060] Once the battery exhaust byproducts V have been exhausted from the battery pack assembly 25 and the temperature sensed by the temperature sensor 76 drops to less than or equal to the predefined temperature threshold, the control module 78 can command the flow control valve 38 back to the first position for directing the cooling fluid F through the main closed-loop cooling circuit 34. Thus, normal operation of the immersion cooling system 32 can be reestablished after a battery thermal event.

[0061] The control module 78 can be programmed to control the immersion cooling system 32 in the second operating mode for a predefined amount of time (e.g., approximately 20 seconds or some other suitable amount of time selected based on design-specific factors). The predefined amount of time is sufficient to allow the battery exhaust byproducts V to be exhausted from the battery pack assembly 25 without creating an overpressure condition within the housing assembly 28.

[0062] An exemplary traction battery pack of the present disclosure includes an immersion cooling system for providing enhanced battery cell thermal management and exhaust gas management. The flow path of the cooling fluid used within the immersion cooling system can be controlled based on the temperature of the cooling fluid, thereby preserving the battery interior volume to provide a gas escape flow path for exhaust gases from the battery pack and maintaining thermal performance during battery thermal events.

[0063] Although different non-limiting embodiments are shown as having specific components or steps, the embodiments of the present disclosure are not limited to these specific combinations. Some components or features from any one of the non-limiting embodiments can be used in combination with features or components from any one of the other non-limiting embodiments.

[0064] It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings.It should be understood that although particular component arrangements are disclosed and shown in these exemplary embodiments, other arrangements may also benefit from the teachings of this disclosure.

[0065] The foregoing description should be interpreted as illustrative and not limiting. Those skilled in the art will appreciate that certain modifications may occur within the scope of this disclosure. For these reasons, the appended claims should be studied to determine the true scope and content of this disclosure.

Claims

1. A traction battery pack system comprising: a battery pack assembly, the battery pack assembly comprising a battery module housed within a housing assembly; a primary closed-loop cooling circuit establishing a first flow path of the immersion cooling system; an auxiliary closed-loop cooling circuit establishing a second flow path of the immersion cooling system; a flow control valve arranged to control the flow of cooling fluid along the first flow path or the second flow path; as well as A control module is programmed to control a position of the flow control valve based on a temperature of the cooling fluid exiting the battery pack assembly.

2. The traction battery pack system of claim 1 , comprising a temperature sensor positioned within or adjacent to an outlet port of the battery pack assembly.

3. The traction battery pack system according to claim 1 or 2, wherein the cooling fluid is a dielectric fluid.

4. The traction battery pack system of any preceding claim, wherein the control module is programmed to command the flow control valve to a first position to direct the cooling fluid along the first flow path when the temperature of the cooling fluid is less than or equal to a predefined temperature threshold, and is further programmed to command the flow control valve to a second position to direct the cooling fluid along the second flow path when the temperature of the cooling fluid is greater than the predefined temperature threshold.

5. The traction battery pack system of claim 4 , wherein the first flow path extends through both a first battery internal fluid channel and a second battery internal fluid channel of the battery pack assembly, and further, wherein the second flow path extends through the first battery internal fluid channel of the battery pack assembly but does not extend through the second battery internal fluid channel, and optionally, wherein the first battery internal fluid channel extends between a bottom side of the plurality of battery cells of the battery module and a housing tray of the housing assembly, and the second battery internal fluid channel extends between a top side of the plurality of battery cells of the battery module and a housing cover of the housing assembly.

6. The traction battery pack system of claim 5 , wherein when the temperature of the cooling fluid is greater than the predefined temperature threshold, the second internal fluid passage establishes a dedicated gas exit flow path for exhausting battery exhaust byproducts from the battery pack assembly.

7. The traction battery pack system according to any preceding claim, wherein the main closed-loop cooling circuit of the immersion cooling system comprises a first inlet port, a first battery internal fluid passage, a first outlet port, a second inlet port, an external fluid passage connected between the first outlet port and the second inlet port, a second battery internal fluid passage, and a second outlet port. 8 . The traction battery pack system of claim 7 , wherein the auxiliary closed-loop cooling circuit of the immersion cooling system comprises the first inlet port, the first battery internal fluid channel, the first outlet port, and a return line.

9. The traction battery pack system of claim 8, wherein the immersion cooling system further comprises a reservoir fluidly connected to the first inlet port, and optionally, wherein the reservoir is positioned on a side of the battery pack assembly opposite the flow control valve, and optionally, wherein the immersion cooling system further comprises a pump disposed between the reservoir and the first inlet port. 10 . The traction battery pack system of claim 8 , comprising a first heat exchanger fluidly connected to the external fluid passage and a second heat exchanger fluidly connected to the return line.

11. The traction battery pack system of claim 8 , wherein a first position of the flow control valve is configured to divert the cooling fluid into the external fluid passage of the primary closed-loop cooling circuit, and a second position of the flow control valve is configured to divert the cooling fluid into the return line of the auxiliary closed-loop cooling circuit.

12. The traction battery pack system of claim 7, wherein the immersion cooling system further comprises a liquid-gas separator fluidly connected to the second outlet port, and optionally, wherein the liquid-gas separator is positioned on a side of the battery pack assembly opposite the flow control valve.

13. The traction battery pack system of claim 7, comprising a temperature sensor positioned in or near the second outlet port.

14. A traction battery pack system according to any preceding claim, wherein the flow control valve is positioned external to the housing assembly of the battery pack assembly, and optionally wherein the flow control valve is positioned between an outlet port of the battery pack assembly and a heat exchanger of the primary closed-loop cooling circuit.

15. A method comprising: circulating a cooling fluid along a first flow path provided by a primary closed-loop cooling circuit of the immersion cooling system; monitoring a temperature of the cooling fluid as it travels along the first flow path; and circulate the cooling fluid along a second flow path provided by an auxiliary closed-loop cooling circuit of the immersion cooling system when the temperature exceeds a predefined temperature threshold, Wherein circulating the cooling fluid along the second flow path includes preventing the cooling fluid from passing through a portion of the first flow path of the main closed-loop cooling circuit.

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