Battery pack exhaust assembly and exhaust method

Abstract

The invention provides a battery pack venting assembly and a venting method. A method of venting a traction battery pack includes providing a manifold system fluidly coupling a plurality of battery modules to a battery pack vent. Each of the battery modules has a stack of cells. The manifold system communicates exhaust by-products discharged from each cell stack along a first path to the battery pack vent, and also communicates exhaust by-products discharged from each cell stack along a second path to the battery pack vent. When a cell stack exhausts an exhaust byproduct stream, the method directs a first percentage of the flow through the manifold system to a battery pack vent along the first path and a second percentage of the flow through the manifold system to the battery pack vent along the second path. The method then includes venting the first percentage and the second percentage through the battery pack vent.

Description

Technical Field

[0001] The present disclosure generally relates to exhausting exhaust byproducts from a traction battery pack. Background Art

[0002] Electrified vehicles differ from conventional motor vehicles in that they are selectively driven using one or more electric motors powered by a traction battery. The electric motors can replace or supplement an internal combustion engine to power an electrified vehicle. Exemplary electrified vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and battery electric vehicles (BEVs). Summary of the Invention

[0003] In some aspects, the technology described herein relates to a method of venting a traction battery pack, the method comprising: providing a manifold system that fluidly couples a plurality of battery modules to a battery pack vent, each of the battery modules having an associated battery cell stack, the manifold system being configured to convey exhaust byproducts exhausted from each battery cell stack to the battery pack vent along a first path, and also being configured to convey exhaust byproducts exhausted from each battery cell stack to the battery pack vent along a second path; when the battery stacks exhaust a flow of exhaust byproducts, directing a first percentage of the flow through the manifold system along the first path to the battery pack vent, and directing a second percentage of the flow through the manifold system along the second path to the battery pack vent; and venting the first percentage and the second percentage through the battery pack vent.

[0004] In some aspects, the technology described herein relates to a method further comprising: moving a pressure relief valve assembly from a closed position to an open position to allow a first percentage of the exhaust byproduct flow to move to the first path and a second percentage of the exhaust byproduct flow to move to the second path, the first percentage and the second percentage being dependent on the open position of the pressure relief valve assembly.

[0005] In some aspects, the technology described herein relates to a method wherein the traction battery pack includes a plurality of flow dividers, each flow divider within the plurality of flow dividers being associated with one of the battery modules within the plurality of battery modules, each flow divider dividing the exhaust byproduct flow from the associated battery cell stack into the first percentage and the second percentage, wherein the flow dividers within the plurality of flow dividers divide the exhaust byproduct flow differently from one another depending on a comparison of an amount of time the exhaust byproduct flow is contained within a manifold system while being transmitted along a first path to a battery pack exhaust outlet and an amount of time the exhaust byproduct flow is contained within the manifold system while being transmitted along a second path.

[0006] In some aspects, the technology described herein relates to a method wherein a first percentage of the exhaust byproduct flow is contained within the manifold system for a first amount of time when conveyed along the first path to the battery pack vent, and a second percentage of the exhaust byproduct flow is contained within the manifold system for a second amount of time when conveyed along the second path to the battery pack vent, the first amount of time being longer than the second amount of time.

[0007] In some aspects, the technology described herein relates to a method wherein a first amount of time and a second amount of time associated with exhaust byproducts from a first battery cell stack through a battery pack vent are further apart than a first amount of time and a second amount of time associated with exhaust byproducts from a second battery cell stack through a battery pack vent, wherein a shunt associated with the second battery cell stack is more evenly divided into the first percentage and the second percentage than a shunt associated with the first battery cell stack.

[0008] In some aspects, the technology described herein relates to a method wherein the first path from a first module having the first battery cell stack to the battery pack vent is a longer path than the second path from the first module to the battery pack vent.

[0009] In some aspects, the technology described herein relates to a method wherein the plurality of flow diverters are a plurality of pressure relief valve assemblies that move to an open position to allow exhaust byproduct flow to be discharged from an associated battery cell stack into a manifold system.

[0010] In some aspects, the technology described herein relates to a method wherein the pressure relief valve assemblies within the plurality of pressure relief valve assemblies each include a spring, and the method further comprises adjusting the first percentage and the second percentage of each of the pressure relief valve assemblies to thereby change a biasing force of the spring.

[0011] In some aspects, the technology described herein relates to a traction battery vent system comprising: a battery pack vent; a first battery module having a first battery cell stack; a second battery module having a second battery cell stack; a manifold system fluidly coupling the first battery module and the second battery module to the battery pack vent; a first flow diverter configured to divert exhaust byproducts exhausted from the first battery cell stack into the manifold system, the first flow diverter directing a first percentage of the exhaust byproducts exhausted from the first battery cell stack into the manifold system to flow along a first path to the battery pack vent, The first diverter guides a second percentage of the exhaust byproducts discharged from the first battery cell stack into the manifold system to flow to the battery pack exhaust port along a different second path; and a second diverter, the second diverter is configured to transfer the exhaust byproducts discharged from the second battery cell stack into the manifold system, the second diverter guides a first percentage of the exhaust byproducts discharged from the second battery cell stack into the manifold system to flow to the battery pack exhaust port along the first path, and the second diverter guides a second percentage of the exhaust byproducts discharged from the second battery cell stack into the manifold system to flow to the battery pack exhaust port along a different second path.

[0012] In some aspects, the technology described herein relates to a traction battery exhaust system wherein the first flow diverter is configured to direct more flow to the first path than to the second path.

[0013] In some aspects, the technology described herein relates to a traction battery exhaust system wherein the first flow divider is configured to direct more flow to the first path than to the second flow divider.

[0014] In some aspects, the technology described herein relates to a traction battery vent system wherein a first flow diverter is a first valve assembly having a first spring, and the second flow diverter is a second valve assembly having a second spring, wherein a spring constant of the first spring is different from a spring constant of the second spring such that an open position of the first valve assembly is different from an open position of the second valve assembly.

[0015] In some aspects, the technology described herein relates to a traction battery vent system, the traction battery vent system comprising: a plurality of battery modules, each having at least one battery cell stack; a battery pack vent; and a manifold system fluidly coupling the battery modules to the battery pack vent, the manifold system configured to route a first percentage of exhaust byproducts exhausted from one of the battery cell stacks to the battery pack vent along a first path and route a second percentage of exhaust byproducts exhausted from one of the battery cell stacks to the battery pack vent along a second path, the first path being longer than the second path.

[0016] In some aspects, the technology described herein relates to a traction battery exhaust system, the traction battery exhaust system also including a diverter system having a plurality of diverters, each diverter within the plurality of diverters being associated with one of the battery cell stacks within the plurality of battery cell stacks, each diverter within the plurality of diverters being configured to direct more exhaust byproduct flow to the first path than to the second path.

[0017] In some aspects, the technology described herein relates to a traction battery vent system wherein the plurality of flow diverters includes a plurality of pressure relief valve assemblies that transition to an open position in response to a pressure differential.

[0018] In some aspects, the technology described herein relates to a traction battery vent system wherein the plurality of pressure relief valve assemblies each include a biasing member having a biasing force that controls the open position, wherein the biasing force among the plurality of pressure relief valve assemblies varies to cause some of the pressure relief valve assemblies to direct more flow to the first path when in the open position than other pressure relief valve assemblies when in the open position.

[0019] In some aspects, the technology described herein relates to a traction battery exhaust system wherein the pressure relief valve assembly is configured to open to allow the exhaust byproducts to move from the respective battery cell stack to the manifold system, and the pressure relief valve assembly is configured to open by different amounts to direct more of the exhaust byproduct flow to the first path.

[0020] In some aspects, the technology described herein relates to a traction battery exhaust system wherein the manifold system surrounds the plurality of battery modules.

[0021] In some aspects, the technology described herein relates to a traction battery vent system wherein each of the cell stacks within the plurality of cell stacks is housed within a module housing assembly.

[0022] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The various features and advantages of the disclosed examples will become apparent to those skilled in the art based on the detailed description. The drawings accompanying the detailed description can be briefly described as follows:

[0024] Figure 1 Shown is a side view of an electrified vehicle with a traction battery pack.

[0025] Figure 2 A perspective and partially expanded view of a battery pack according to an exemplary aspect of the present disclosure is shown.

[0026] Figure 3 Shown Figure 2 Schematic top view of a battery pack as battery cells of the cell stack are discharging an exhaust byproduct stream.

[0027] Figure 4 Shown Figure 2 Schematic top view of a battery pack as another battery cell of another battery cell stack is discharging an exhaust byproduct stream.

[0028] Figure 5 Shown Figure 3 Close-up view of the area.

[0029] Figure 6 Shown Figure 4 Close-up view of the area. DETAILED DESCRIPTION

[0030] The present disclosure relates generally to a traction battery pack for an electrified vehicle, and particularly to exhausting exhaust byproducts from a traction battery pack.

[0031] refer to Figure 1 , electrified vehicle 10 includes a traction battery pack 12, an electric motor 14, and wheels 16. Battery pack 12 powers electric motor 14, which converts electrical energy into torque to drive wheels 16. Battery pack 12 is a traction battery pack because battery pack 12 is used for propulsion.

[0032] In the exemplary embodiment, the battery pack 12 is secured to the underbody of the electrified vehicle 10. In other examples, the battery pack 12 may be located elsewhere on the electrified vehicle 10.

[0033] Example vehicle 10 is a battery electric vehicle (BEV). In another example, vehicle 10 can be another type of electrified vehicle, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a conventional vehicle. A hybrid electric vehicle selectively drives the wheels using torque provided by an internal combustion engine (in place of or in addition to an electric motor). In general, electrified vehicle 10 can be any type of vehicle having a traction battery pack.

[0034] Now refer to Figures 2 to 4 The battery pack 12 includes a battery pack housing assembly 18 and a plurality of battery modules 20 housed within an interior 24 of the battery pack housing assembly 18. Each of the battery modules 20 includes a module housing assembly 32 and a cell stack 36 housed within the module housing assembly. The cell stack 36 includes a plurality of individual battery cells 40.

[0035] In this example, each of the module housing assemblies 32 houses a single battery cell stack 36. In other examples, the module housing assemblies 32 may house more than one battery cell stack 36.

[0036] At times, pressure and heat may increase within at least one of the battery cells 40 in the cell stack 36 of the battery pack 12. This may cause the battery cell 40 to expel a stream of exhaust byproducts V, which may include gases and debris. Figure 3 A flow of exhaust byproducts V is shown for one of the battery cells 40 in one of the battery modules 20A. Figure 4 A flow of exhaust byproducts V is shown being exhausted from one of the battery cells 40 in another of the battery modules 20B.

[0037] The exhaust byproducts V may be exhausted from the battery cell 40 through a designated cell vent 46 within the housing of the battery cell 40. The cell vent 46 may be a membrane that yields in response to increased pressure and heat energy within the battery cell 40. The cell vent 46 may also be a ruptured area of the associated battery cell 40.

[0038] The battery pack 12 also includes a manifold system 50 and a battery pack vent 54. In this example, the manifold system 50 is connected to each of the module housing assemblies 32 to fluidly couple each of the battery modules 20 to the battery pack vent 54. As needed, the manifold system 50 can transfer the exhaust byproduct V flow exhausted from one or more battery cells 40 within the cell stack 36 to the battery pack vent 54. At the battery pack vent 54, the exhaust byproduct V flow is exhausted from the battery pack 12 to the area around the battery pack vent 54. In this example, the manifold system 50 surrounds multiple battery modules 20. All twelve module housing assemblies 32 can lead to the manifold system 50.

[0039] In this example, after the exhaust byproducts V pass through the cell exhaust ports 46 , the exhaust byproducts V are initially contained within the interior of the module housing assembly 32 . The exhaust byproducts V may then flow to the manifold system 50 .

[0040] The manifold system 50 is configured to transmit the exhaust byproducts V to the battery pack exhaust port 54 along a corresponding first path P1 or to transmit the exhaust byproducts V to the battery pack exhaust port 54 along a corresponding second path P2. In this example, the first path is longer than the second path. In this example, the exhaust byproducts V transmitted to the battery pack exhaust port 54 along the first path will remain within the manifold system 50 for a longer time than the exhaust byproducts V transmitted to the battery pack exhaust port 54 along the second path.

[0041] In this example, each battery module 20 has its own first path P1 and its own second path P2. In this example, the length of the first path P1 and the length of the second path P2 depend on the position of the battery module 20 relative to the battery pack vent 54 to the manifold system 50. Figure 3 In , the first difference is the difference between the length of the first path P1 from the battery module 20A and the length of the second path P2 from the battery module 20A. Figure 4 , the second difference is the difference between the length of the first path P1 from the battery module 20B and the length of the second path P2 from the battery module 20B. The first difference is greater than the second difference.

[0042] As the flow of exhaust byproducts V is routed through the manifold system 50, heat energy within the flow of exhaust byproducts V is dissipated. With respect to the battery modules 20A and 20B, because the exhaust byproducts V routed to the battery pack exhaust port 54 along the first path P1 remain in the manifold system 50 for a longer time than the exhaust byproducts V routed to the battery pack exhaust port 54 along the second path P2, the exhaust byproducts V exhausted from the battery pack exhaust port 54 after being routed along the first path P1 contain less heat energy than the exhaust byproducts V exhausted from the battery pack exhaust port 54 after being routed along the second path P2.

[0043] Now refer to Figure 5 and Figure 6 And continue to refer to Figures 2 to 4 The example battery pack 12 includes a plurality of flow diverters 60, which in this example are pressure relief valve assemblies 64. One pressure relief valve assembly 64 is associated with each battery module 20. The pressure relief valve assembly 64 can transition between a closed position and an open position. The pressure relief valve assembly 64 is normally closed, but in this example, transitions to an open position in response to a pressure differential caused by an increase in pressure within the module housing assembly 32 of the corresponding battery module 20.

[0044] In the closed position, the pressure relief valve assembly 64 blocks flow between the manifold system 50 and the module housing assembly 32. This prevents exhaust byproducts V exhausted from the battery cells 40 within one of the battery modules 20 into the manifold system 50 from flowing into the module housing assembly 32 of another of the battery modules 20.

[0045] In the open position, the pressure relief valve assembly 64 allows exhaust byproducts V exhausted from the battery cells 40 of the associated battery module 20 to flow into the manifold system 50. The pressure relief valve assembly 64 may open in response to an increase in pressure within the associated battery module 20 due to one or more of the battery cells 40 of the associated battery module 20 exhausting a flow of exhaust byproducts V into the module housing assembly 32.

[0046] In this example, the pressure relief valve assembly 64 in the open position diverts flow by directing a first percentage of the exhaust byproduct V flow through the manifold system 50 along a first path to the battery pack vent 54, and by directing a second percentage of the exhaust byproduct V flow through the manifold system 50 along a second path to the battery pack vent 54. Each of the pressure relief valve assemblies 64 can be configured to divide the exhaust byproduct V flow between path P1 and path P2 in a different manner.

[0047] In this example, the pressure relief valve assembly 64 in the open position divides flow between the first path P1 and the second path P2. The amount of flow directed to the first path P1 and the second path P2 depends, among other things, on the open position of the pressure relief valve assembly 64.

[0048] The flow divider 60 , here a pressure relief valve assembly 64 , divides the exhaust byproduct V flow differently between the first path P1 and the second path P2 . The division may depend on a comparison of the amount of time the exhaust byproduct V flow is contained within the manifold system 50 while traveling along the respective first path P1 to the battery pack vent 54 , and the amount of time the exhaust byproduct V flow is contained within the manifold system 50 while traveling along the respective second path P2 . In other examples, even if the first path P1 is longer than the second path P2 , the flow rate through the first path P1 may be faster, and the exhaust byproducts may spend approximately the same amount of time within the manifold system while traveling along either the first path P1 or the second path P2 to the battery pack vent 54 .

[0049] As can be understood, when the battery module 20A ( Figure 3 ) will be contained in the manifold system 50 for a greater amount of time than when the exhaust byproduct V flow is transported from the battery module 20B ( Figure 4) is contained within the manifold system 50. Therefore, the flow diverter 60 associated with battery module 20A is configured to direct a greater percentage of the exhaust byproduct V flow to the first path P1, giving the flow time to dissipate thermal energy before being exhausted through the battery pack exhaust port 54. The first path P1 from battery module 20A is longer than the second path. The flow diverter 60 associated with battery module 20B has a different open position that more evenly divides the exhaust byproduct V flow between the first path P1 and the second path P2.

[0050] The example pressure relief valve assembly 64 is configured to direct a greater percentage of exhaust byproducts V along the first path P1 than along the second path P2. This can help reduce the heat energy in the exhaust byproduct V flow exhausted through the battery pack vent 54. In this example, the open position of the pressure relief valve assembly 64 controls the percentage of exhaust byproducts V directed along the first path P1 and the percentage of exhaust byproducts V directed along the second path P2.

[0051] At least some of the pressure relief valve assemblies 64 are configured to have different open positions at a given pressure. For example, a pressure of 5 kilopascals within battery module 20A may cause pressure relief valve assembly 64A to move to a first open position, and a pressure of 5 kilopascals within battery module 20B may cause pressure relief valve assembly 64B to move to a second open position that is different from the first open position.

[0052] In this example, the open position of the pressure relief valve assembly 64 associated with the battery module 20A is a first open position that directs 90 percent of the flow of the exhaust byproducts V from the battery module 20A into the manifold system 50 in a first direction D1 to flow along a first path P1, and directs the remaining 10 percent of the flow of the exhaust byproducts V into the manifold system 50 in a second direction D2 to flow along a second path P2. The open position of the pressure relief valve assembly 64 associated with the battery module 20B is a second open position that directs 55 percent of the flow of the exhaust byproducts V into the manifold system 50 in the first direction D1 to flow along the first path, and directs the remaining 45 percent of the flow of the exhaust byproducts V into the manifold system 50 in a second direction D2 to flow along the second path.

[0053] The example pressure relief valve assembly 64 is a disc valve having a valve disc 68 that rotates from a closed position to an open position. A biasing member, such as a torsion spring 72, biases the valve disc 68 to the closed position and resists rotation of the valve disc 68 due to an increase in pressure within the module housing assembly 32 of the associated battery module 20. In this example, the torsion spring 72 used for the pressure relief valve assembly 64 is selected at least in part based on its spring constant, and the open position of the pressure relief valve assembly 64 is established by the spring constant. Thus, in the example embodiment, the percentage of flow directed along the first path P1 and the percentage of flow directed along the second path P2 are controlled by the spring constant of the torsion spring 72. The percentage of flow directed along the first path P1 and the percentage of flow directed along the second path P2 can be adjusted by varying the biasing force of the torsion spring 72.

[0054] The spring constant of the torsion spring 72 associated with the battery module 20A may be smaller than the spring constant of the torsion spring 72 associated with the battery module 20B. This ensures that the valve disc 68 associated with the battery module 20A opens further than the valve disc 68 associated with the battery module 20B in response to a given pressure.

[0055] In other examples, flow divider 60 may be provided by a valve that opens but does not divert flow between the first and second paths. Conversely, downstream of the valve, a fixed flow divider may be positioned to direct a desired percentage of the exhaust byproduct flow V to the first path and a desired percentage of the exhaust byproduct flow V to the second path.

[0056] Features of the disclosed examples include dividing the exhaust byproduct flow to flow along more than one path to the battery pack vent to, inter alia, reduce thermal energy in the exhaust byproduct flow before exhausting the exhaust byproduct flow through the battery pack vent.

[0057] The foregoing description is illustrative rather than restrictive in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art, and such variations and modifications do not necessarily depart from the essence of the present disclosure. Therefore, the scope of protection afforded to the present disclosure should be determined solely by studying the appended claims.

[0058] According to the present invention, a traction battery exhaust system is provided, comprising: a battery pack exhaust port; a first battery module, the first battery module having a first battery cell stack; a second battery module, the second battery module having a second battery cell stack; a manifold system, the manifold system fluidly coupling the first battery module and the second battery module to the battery pack exhaust port; a first flow diverter, the first flow diverter being configured to divert exhaust byproducts exhausted from the first battery cell stack into the manifold system, the first flow diverter directing a first percentage of the exhaust byproducts exhausted from the first battery cell stack into the manifold system to flow along a first path to the battery pack exhaust port, the first flow diverter being configured to direct ... A diverter directs a second percentage of the exhaust byproducts discharged from the first battery cell stack into the manifold system to flow along a different second path to the battery pack exhaust port; and a second diverter, the second diverter being configured to transfer the exhaust byproducts discharged from the second battery cell stack into the manifold system, the second diverter directs a first percentage of the exhaust byproducts discharged from the second battery cell stack into the manifold system to flow along the first path to the battery pack exhaust port, and the second diverter directs a second percentage of the exhaust byproducts discharged from the second battery cell stack into the manifold system to flow along a different second path to the battery pack exhaust port.

[0059] According to an embodiment, the first flow splitter is configured to direct more flow to the first path than to the second path.

[0060] According to an embodiment, the first flow splitter is configured to direct more flow to the first path than to the second flow splitter.

[0061] According to an embodiment, the first flow diverter is a first valve assembly having a first spring, and the second flow diverter is a second valve assembly having a second spring, wherein a spring constant of the first spring is different from a spring constant of the second spring, so that an open position of the first valve assembly is different from an open position of the second valve assembly.

Claims

1. A method for venting a traction battery pack, comprising: providing a manifold system fluidly coupling a plurality of battery modules to a battery pack vent, each of the battery modules having an associated battery cell stack, the manifold system being configured to convey exhaust byproducts exhausted from each battery cell stack to the battery pack vent along a first path and further configured to convey exhaust byproducts exhausted from each battery cell stack to the battery pack vent along a second path; When the battery cell stack exhausts an exhaust byproduct flow, directing a first percentage of the flow through the manifold system along the first path to a battery pack exhaust port, and directing a second percentage of the flow through the manifold system along the second path to the battery pack exhaust port; as well as The first percentage and the second percentage are exhausted through the battery pack vent.

2. The method of claim 1, further comprising: Moving a pressure relief valve assembly from a closed position to an open position allows the first percentage of the exhaust byproduct flow to move to the first path and the second percentage of the exhaust byproduct flow to move to the second path, the first percentage and the second percentage being dependent on the open position of the pressure relief valve assembly.

3. The method of claim 1 , wherein the traction battery pack includes a plurality of flow dividers, each flow divider within the plurality of flow dividers being associated with one of the battery modules within the plurality of battery modules, each flow divider dividing the exhaust byproduct flow from the associated battery cell stack into the first percentage and the second percentage, wherein the flow splitters within the plurality of flow splitters divide the exhaust byproduct streams differently from one another depending on a comparison of an amount of time the exhaust byproduct streams are contained within the manifold system while being conveyed along the first path to the battery pack exhaust port and an amount of time the exhaust byproduct streams are contained within the manifold system while being conveyed along the second path.

4. The method of claim 3 , wherein a first percentage of the exhaust byproduct stream is contained within the manifold system for a first amount of time when conveyed along the first path to the battery pack vent, and a second percentage of the exhaust byproduct stream is contained within the manifold system for a second amount of time when conveyed along the second path to the battery pack vent, the first amount of time being longer than the second amount of time.

5. The method of claim 4 , wherein the first amount of time and the second amount of time associated with exhaust byproducts from a first battery cell stack through the battery pack vent are further apart than the first amount of time and the second amount of time associated with exhaust byproducts from a second battery cell stack through the battery pack vent, The current shunt associated with the second battery cell stack is divided more evenly into the first percentage and the second percentage than the current shunt associated with the first battery cell stack. 6 . The method of claim 5 , wherein the first path from a first module having the first battery cell stack to the battery pack vent is a longer path than the second path from the first module to the battery pack vent. 7 . The method of claim 6 , wherein the plurality of flow diverters are a plurality of pressure relief valve assemblies that move to an open position to allow the exhaust byproduct flow to be discharged from an associated battery cell stack into the manifold system.

8. The method of claim 7, wherein each of the pressure relief valve assemblies within the plurality of pressure relief valve assemblies includes a spring, and the method further comprises: The first percentage and the second percentage of each of the pressure relief valve assemblies are adjusted to change the biasing force of the spring.

9. A traction battery exhaust system comprising: a plurality of battery modules, each of the plurality of battery modules having at least one battery cell stack; Battery pack exhaust port; as well as a manifold system fluidly coupling the battery modules to the battery pack vent, the manifold system being configured to convey a first percentage of exhaust byproducts exhausted from one of the battery cell stacks to the battery pack vent along a first path and to convey a second percentage of the exhaust byproducts exhausted from the one of the battery cell stacks to the battery pack vent along a second path, the first path being longer than the second path.

10. The traction battery exhaust system of claim 9 , further comprising a diverter system having a plurality of diverters, each diverter within the plurality of diverters being associated with one of the battery cell stacks within the plurality of battery cell stacks, each diverter within the plurality of diverters being configured to direct more of the exhaust byproduct flow to the first path than to the second path.

11. The traction battery vent system of claim 10, wherein the plurality of flow diverters comprises a plurality of pressure relief valve assemblies that transition to an open position in response to a pressure differential.

12. The traction battery vent system of claim 11 , wherein each of the plurality of pressure relief valve assemblies includes a biasing member having a biasing force that controls the open position, wherein the biasing force among the plurality of pressure relief valve assemblies varies to cause some of the pressure relief valve assemblies to direct more flow to the first path when in the open position than other pressure relief valve assemblies when in the open position.

13. The traction battery exhaust system of claim 11 , wherein the pressure relief valve assembly is configured to open to allow the exhaust byproducts to move from the respective battery cell stack to the manifold system, and the pressure relief valve assembly is configured to open by different amounts to direct more of the exhaust byproduct flow to the first path.

14. The traction battery exhaust system of claim 9, wherein the manifold system surrounds the plurality of battery modules.

15. The traction battery exhaust system of claim 9, wherein each of the cell stacks within the plurality of cell stacks is housed within a module housing assembly.

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