BATTERY PACK VENT ASSEMBLY AND VENTILATION PROCEDURE

Abstract

A battery pack vent assembly includes a battery pack housing assembly providing a battery pack interior, and cell stacks within the battery pack interior. Each cell stack contains a plurality of battery cells. Module housing assemblies are also located within the battery pack interior. Each of the module housing assemblies houses one or more of the cell stacks. A vent channel extends through the battery pack housing assembly from the battery pack interior to an area outside the battery pack interior. Vent branches within the battery pack interior each extend from one of the module housing assemblies to the vent channel.

Description

FIELD OF TECHNOLOGYThis disclosure relates generally to draining vent byproducts from a traction battery pack.GENERAL STATE OF THE ARTElectrified vehicles are distinct from conventional motor vehicles because electrified vehicles are selectively propelled using one or more electric machines powered by a traction battery. The electric machines may propel the electrified vehicles instead of or in addition to an internal combustion engine. Example electrified vehicles include hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell vehicles (FCVs), and battery electric vehicles (BEVs).Referring to FIG. 1, a battery pack 2 according to the related art includes a plurality of battery cell arrays 4 disposed within an interior of a housing 6. If a battery cell in one of the groups 4 is vented, venting byproducts are released into an interior of the housing 6. Within the interior of the housing 6, the vent byproducts may flow adjacent to other battery cell arrays 4 before passing through a vent 8 to an area outside of the housing 6.SUMMARYIn some aspects, the techniques described herein relate to a battery pack venting assembly including: a battery pack housing assembly providing a battery pack interior; a plurality of cell stacks within the battery pack interior, each cell stack including a plurality of battery cells; a plurality of module housing assemblies within the battery pack interior, each of the module housing assemblies housing one or more of the cell stacks; a drain channel extending through the battery pack housing assembly from the battery pack interior to a region outside the battery pack interior; a plurality of drain branches within the battery pack interior, each of the drain branches extending from one of the module housing assemblies to the drain channel.In some aspects, the techniques described herein relate to a battery pack venting assembly wherein the discharge branches each open to the discharge passage within the battery pack interior.In some aspects, the techniques described herein relate to a battery pack venting assembly, wherein the exhaust branches are each configured to communicate venting byproducts directly from one of the module housing assemblies to the exhaust passage.In some aspects, the techniques described herein relate to a battery pack venting assembly, wherein the discharge channel is configured to communicate venting byproducts received from one or more of the discharge branches to the area outside of the battery pack venting assembly.In some aspects, the techniques described herein relate to a battery pack venting assembly, wherein the module housing assemblies, the discharge branches, and the discharge channel are sealed such that within the battery pack interior, venting byproducts are contained by the module housing assemblies, the discharge branches, and the discharge channel.In some aspects, the techniques described herein relate to a battery pack venting assembly wherein the cell stacks are immersion cooled.In some aspects, the techniques described herein relate to a battery pack venting assembly, further including a plurality of coolant inlet branches, each of the coolant inlet branches configured to communicate a liquid coolant to one of the module housing assemblies.In some aspects, the techniques described herein relate to a battery pack venting assembly further including a coolant inlet channel that communicates a liquid coolant to each of the plurality of coolant inlet branches.In some aspects, the techniques described herein relate to a battery pack venting assembly wherein the coolant inlet branches within the battery pack interior are directly connected to the coolant inlet channel.In some aspects, the techniques described herein relate to a battery pack venting assembly, wherein the plurality of discharge branches are configured to communicate liquid coolant and venting byproducts directly from one of the module housing assemblies to the discharge passage.In some aspects, the techniques described herein relate to a battery pack venting assembly, wherein the battery cells are each configured to be vented to a liquid coolant.In some aspects, the techniques described herein relate to a battery pack venting assembly further including a plurality of check valves that block backflow of venting byproducts from the drain passage through the drain branches.In some aspects, the techniques described herein relate to a method of venting from a battery pack, including: within a battery pack interior provided by a battery pack housing assembly, communicating venting byproducts from a battery module housing assembly into a discharge branch, wherein the venting byproducts are expelled from at least one battery cell within a cell stack housed within the battery pack interior; within the battery pack interior, communicating the venting byproducts through the discharge branch into a discharge channel; and communicating the venting byproducts through the discharge channel through the battery pack housing to an area outside the battery pack housing to discharge the venting byproducts from the battery pack housing.In some aspects, the techniques described herein relate to a method wherein the module housing assemblies, the exhaust branches, and the exhaust passage are sealed such that within the battery pack interior, venting byproducts are contained by the module housing assemblies, the exhaust branches, and the exhaust passage.In some aspects, the techniques described herein relate to a method wherein the battery module housing assembly is one of a plurality of battery module housing assemblies within the battery pack housing assembly.In some aspects, the techniques described herein relate to a method wherein each of the battery module housing assemblies includes at least one cell stack having a plurality of battery cells.In some aspects, the techniques described herein relate to a method wherein cell stacks each include a plurality of individual battery cells configured to be vented to a liquid coolant.In some aspects, the techniques described herein relate to a method further including managing thermal energy within the battery pack interior using an immersion thermal management system.In some aspects, the techniques described herein relate to a method further including communicating a liquid coolant through a coolant inlet channel into the battery pack interior and communicating the liquid coolant through one of a plurality of coolant inlet branches from the coolant inlet channel to one of the plurality of battery module housing assemblies.In some aspects, the techniques described herein relate to a method wherein the discharge branch is one of a plurality of discharge branches, each of the discharge branches connecting one of the battery housing modules to the discharge channel, and further including communicating both the venting byproducts and the liquid coolant through one of the discharge branches to the discharge channel.The embodiments, examples and alternatives of the preceding paragraphs, the claims or the following description and drawings, which include any of their various aspects or respective individual features, may be considered independently of one another or in any combination. Features described in connection with an embodiment are applicable to all embodiments, unless such features are incompatible.BRIEF DESCRIPTION OF THE FIGURESThe various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures attached to the detailed description may be briefly described as follows: FIG. 1 illustrates a schematic view of a battery pack according to the prior art. FIG. 2 illustrates a side view of an electrified vehicle having a traction battery pack. FIG. 3 illustrates a perspective and partially cut-away view of a battery pack according to an exemplary aspect of the present disclosure. FIG. 4 illustrates a schematic top view of the battery pack of FIG. 3. FIG. 5 illustrates a schematic top view of a battery pack according to another exemplary aspect of the present disclosure.DETAILED DESCRIPTIONThis disclosure relates generally to a traction battery pack for an electrified vehicle, and more particularly, to draining vent byproducts from an interior of the traction battery pack.Referring to FIG. 2, an electrified vehicle 10 includes a traction battery pack 12, an electric machine 14, and wheels 16. The battery pack 12 provides power to the electric machine 14 that can convert the electric power to torque to propel the wheels 16. The battery pack 12 is a traction battery pack because the battery pack 12 is used for propulsion.The battery pack 12 is secured to an underbody of the electrified vehicle 10 in the exemplary embodiment. The battery pack 12 could be elsewhere on the electrified vehicle 10 in other examples.The example vehicle 10 is a battery electric vehicle (BEV). In another example, the vehicle 10 could be another type of electrified vehicle, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a traditional vehicle. A hybrid electric vehicle selectively drives wheels using torque provided by an internal combustion engine instead of or in addition to an electric machine. In general, the electrified vehicle 10 could be any type of vehicle that includes a traction battery pack.Referring now to FIGS. 3 and 4, the battery pack 12 includes a battery pack housing assembly 18 and a plurality of battery modules 20 housed within an interior space 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.In this example, each of the module housing assemblies 32 accommodates a single cell stack 36. In other examples, the module housing assemblies 32 could hold more than one cell stack 36.Also disposed within the interior space 24 are a plurality of discharge branches 44 and a discharge channel 48. In other examples, two or more discharge branches 44 could be connected to each of the module housing assemblies 32. The module housing assemblies 32 are sealed such that the discharge branches 44 are the exclusive flow path from the module housing assemblies 32.If venting byproducts are released from one or more of the battery cells 40, the venting byproducts may be released from the battery cells 40 through a vent 52. Pressure increases within one of the battery cells 40 may result in the vent 52 ringing, thereby creating a way for the vent byproducts to be released from the interior of the battery cell 40.After the vent byproducts pass through the vent 52, the vent byproducts are initially contained within an interior of the module housing assembly 32. The vent byproducts may then extend from the module housing assembly 32 through the discharge branch 44 to move out of an interior of the module housing assembly 32. The discharge branches 44 each extend from one of the module housing assemblies 32 to the discharge channel 48 in this example.The discharge branch 44 discharges the vent byproducts from the module housing assembly 32 to the discharge passage 48. The exhaust branches 44 open to the exhaust passage 48 within the battery pack interior 24. the exhaust passage 48 communicates the vent byproducts received from the exhaust branches 44 through the battery pack vent assembly 18 to an area outside of the battery pack vent assembly 18.Thus, vent byproducts within the module housing assembly 32 having the one or more battery cells 40 that are vented, the discharge branch 44 connected to that module housing assembly 32, and the discharge channel 48 are contained until the vent byproducts are discharged or discharged from the battery pack 12. The vent byproducts are not released into other areas within the interior space 24 of the battery pack 12. This helps mitigate transfer of thermal energy to the battery modules 20 that are not vented.Within the interior 24, the discharge branches 44 are configured to discharge venting byproducts to the discharge passage 48. Each of the drain branches 44 may include a check valve 56 that blocks venting byproducts discharged from one of the battery modules 20 from flowing back through the drain branches 44 into the module housing assembly 32 of another battery module 20 that does not include battery cells 40 that are being vented.Introducing the vent byproducts into the discharge passage 48 within the battery pack vent assembly 18 may facilitate discharging the vent byproducts to the area outside of the battery pack vent assembly 18. For example, only a single outlet through the battery pack housing assembly 18 instead of an outlet for each exhaust branch 44.Referring now to FIG. 5, in a variation of the example disclosed above, a plurality of battery modules 120 are included within a battery pack housing assembly 118 of a battery pack 112. The thermal energy within the battery modules 120 is managed using an immersion thermal management system.In this example, a plurality of coolant inlet branches 160 are configured to communicate a liquid coolant from a coolant inlet channel 164 to a respective one of the battery modules 120. The liquid coolant may be used to manage thermal energy within the battery modules 120.If battery cells 140 of cell stacks 136 within the battery modules 120 begin to be vented, the venting byproducts are expelled from the battery cell 140, which is directly vented into the coolant within the module housing assembly 132 of the battery module 120 having the battery cell 140 being vented.A mixture of venting byproducts and coolant may then be communicated to a discharge passage 148 through an associated discharge branch 144. The discharge passage 148 discharges the mixture of venting byproducts and coolant to an area outside of the battery pack housing assembly 118. Check valves (not shown in FIG. 5 ) could be used to block flow of venting byproducts from the discharge branches 144 back into the module housing assemblies 132. Check valves could also be added to the coolant inlet branches 160, the coolant inlet channel 164, or both. These check valves could block gas / particulate / fluid backflow during cell venting, particularly during the initial pressure rise.In the example of FIG. 5, the liquid coolant within the module housing assemblies 132 moves along a flow path that is parallel to an orientation of the battery cells 140 within the cell stacks 136. In other examples, the flow path could be oriented differently, such as perpendicular to a longitudinal axis of the cell stack.Features of the disclosed examples substantially include sealing individual cell stacks within respective module housing assemblies disposed within a larger battery pack housing assembly. The individual module housing assemblies may contain venting byproducts from the cells within that module housing assembly and discharge these venting byproducts through discharge branches and a discharge channel to an area outside of a battery pack housing. Because the cell stacks are contained within module housing assemblies, the vent byproducts cannot freely move to positions adjacent to other battery modules within the battery pack.The foregoing description is exemplary and non-limiting in nature. Variations and modifications of the disclosed examples may occur to those skilled in the art that do not necessarily depart from the gist of this disclosure. Accordingly, the scope of protection afforded by this disclosure may be determined only by studying the following claims.

Claims

A battery pack venting assembly, comprising: a battery pack housing assembly providing a battery pack interior; a plurality of cell stacks within the battery pack interior, each cell stack including a plurality of battery cells; a plurality of module housing assemblies within the battery pack interior, each of the module housing assemblies housing one or more of the cell stacks; a drain channel extending through the battery pack housing assembly from the battery pack interior to a region outside the battery pack interior; and a plurality of drain branches within the battery pack interior, each of the drain branches extending from one of the module housing assemblies to the drain channel.The battery pack venting assembly of claim 1, wherein the discharge branches each open to the discharge channel within the battery pack interior.The battery pack venting assembly of claim 1, wherein the exhaust branches are each configured to communicate venting byproducts directly from one of the module housing assemblies to the exhaust passage.The battery pack venting assembly of claim 1, wherein the discharge channel is configured to communicate venting byproducts received from one or more of the discharge branches to the area outside of the battery pack venting assembly.The battery pack venting assembly of claim 1, wherein the module housing assemblies, the discharge branches, and the discharge channel are sealed such that within the battery pack interior, venting byproducts are contained by the module housing assemblies, the discharge branches, and the discharge channel.The battery pack venting assembly of claim 1, wherein the cell stacks are immersion cooled and optionally.The battery pack venting assembly of claim 1, further comprising a plurality of coolant inlet branches, wherein each of the coolant inlet branches is configured to communicate a liquid coolant to one of the module housing assemblies, and optionally wherein the plurality of discharge branches is configured to communicate liquid coolant and venting byproducts directly from one of the module housing assemblies to the discharge channel.The battery pack venting assembly of claim 7, further comprising a coolant inlet channel that communicates a liquid coolant to each of the plurality of coolant inlet branches, and optionally wherein the coolant inlet branches within the battery pack interior are directly connected to the coolant inlet channel.The battery pack venting assembly of claim 1, further comprising a plurality of check valves that block backflow of venting byproducts from the discharge passage through the discharge branches.A method of venting from a battery pack, comprising: within a battery pack interior provided by a battery pack housing assembly, communicating venting byproducts from a battery module housing assembly into a discharge branch, wherein the venting byproducts are expelled from at least one battery cell within a cell stack housed within the battery pack interior; within the battery pack interior, communicating the venting byproducts through the discharge branch into a discharge passage; and communicating the venting byproducts through the discharge passage through the battery pack housing to an area outside the battery pack housing to discharge the venting byproducts from the battery pack housing.The method of claim 10, wherein the module housing assemblies, the exhaust branches, and the exhaust passage are sealed such that within the battery pack interior, venting byproducts are contained by the module housing assemblies, the exhaust branches, and the exhaust passage.The method of claim 10, wherein the battery module housing assembly is one of a plurality of battery module housing assemblies within the battery pack housing assembly.The method of claim 12, wherein each of the battery module housing assemblies includes at least one cell stack having a plurality of individual battery cells, and optionally wherein cell stacks each include a plurality of battery cells configured to be vented to a liquid coolant.The method of claim 12, further comprising managing thermal energy within the battery pack interior using an immersion thermal management system.The method of claim 14, further comprising communicating a liquid coolant through a coolant inlet channel into the battery pack interior and communicating the liquid coolant through one of a plurality of coolant inlet branches from the coolant inlet channel to the plurality of battery module housing assemblies, and optionally wherein the discharge branch is one of a plurality of discharge branches, each of the discharge branches connecting one of the battery housing modules to the discharge channel, and further comprising communicating both the venting byproducts and the liquid coolant through one of the discharge branches to the discharge channel.

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