The present disclosure relates generally to the field of batteries and battery modules. More specifically, the present disclosure relates to water management features for Lithium-ion (Li-ion) battery modules.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A vehicle that uses one or more battery systems for providing all or a portion of the motive power for the vehicle can be referred to as an xEV, where the term “xEV” is defined herein to include all of the following vehicles, or any variations or combinations thereof, that use electric power for all or a portion of their vehicular motive force. For example, xEVs include electric vehicles (EVs) that utilize electric power for all motive force. As will be appreciated by those skilled in the art, hybrid electric vehicles (HEVs), also considered xEVs, combine an internal combustion engine propulsion system and a battery-powered electric propulsion system, such as 48 Volt (V) or 130V systems. The term HEV may include any variation of a hybrid electric vehicle. For example, full hybrid systems (FHEVs) may provide motive and other electrical power to the vehicle using one or more electric motors, using only an internal combustion engine, or using both. In contrast, mild hybrid systems (MHEVs) disable the internal combustion engine when the vehicle is idling and utilize a battery system to continue powering the air conditioning unit, radio, or other electronics, as well as to restart the engine when propulsion is desired. The mild hybrid system may also apply some level of power assist, during acceleration for example, to supplement the internal combustion engine. Mild hybrids are typically 96V to 130V and recover braking energy through a belt or crank integrated starter generator. Further, a micro-hybrid electric vehicle (mHEV) also uses a “Stop-Start” system similar to the mild hybrids, but the micro-hybrid systems of a mHEV may or may not supply power assist to the internal combustion engine and operates at a voltage below 60V. For the purposes of the present discussion, it should be noted that mHEVs typically do not technically use electric power provided directly to the crankshaft or transmission for any portion of the motive force of the vehicle, but an mHEV may still be considered as an xEV since it does use electric power to supplement a vehicle's power needs when the vehicle is idling with internal combustion engine disabled and recovers braking energy through an integrated starter generator. In addition, a plug-in electric vehicle (PEV) is any vehicle that can be charged from an external source of electricity, such as wall sockets, and the energy stored in the rechargeable battery packs drives or contributes to drive the wheels. PEVs are a subcategory of EVs that include all-electric or battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicle conversions of hybrid electric vehicles and conventional internal combustion engine vehicles.
xEVs as described above may provide a number of advantages as compared to more traditional gas-powered vehicles using only internal combustion engines and traditional electrical systems, which are typically 12V systems powered by a lead acid battery. For example, xEVs may produce fewer undesirable emission products and may exhibit greater fuel efficiency as compared to traditional internal combustion vehicles and, in some cases, such xEVs may eliminate the use of gasoline entirely, as is the case of certain types of EVs or PEVs.
As technology continues to evolve, there is a need to provide improved power sources, particularly battery modules, for such vehicles. For example, traditional battery modules are susceptible to condensation, water, or other fluids gathering inside a housing of the battery module, which may negatively affect components (e.g., electrical components) of the battery module and electrochemical cells thereof.
A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.
The present disclosure relates to a battery module having a housing configured to receive one or more electrochemical cells. The housing includes a bottom internal surface and a recessed portion disposed in the bottom internal surface and proximate to a low point on the bottom internal surface, wherein the recessed portion defines an airspace configured to retain fluid within the housing away from the one or more electrochemical cells.
The present disclosure also relates to a housing configured to house a plurality of electrochemical cells. The housing includes a bottom side having a bottom internal surface. The housing also includes an opening extending through the bottom side and disposed at a low point on the bottom internal surface such that fluid is gravity fed from the bottom internal surface toward the opening. The opening is configured to drain the fluid through the bottom side of the housing.
The present disclosure further relates to a battery module having a housing configured to house a plurality of electrochemical cells. The housing includes a bottom internal surface on a bottom side of the housing. The housing also includes an opening extending through the bottom side from the bottom internal surface to a bottom external surface and disposed at a low point on the bottom internal surface, such that fluid is gravity fed from the bottom internal surface toward the opening. The opening is configured to selectively drain the fluid from an inside of the housing to an outside of the housing and the opening comprises a self-sealing port having a plunger seal or a pressure relief seal.
Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which:
One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.
The battery systems described herein may be used to provide power to various types of electric vehicles (xEVs) and other high voltage energy storage/expending applications (e.g., electrical grid power storage systems). Such battery systems may include one or more battery modules, each battery module having a housing and a number of battery cells (e.g., Lithium-ion (Li-ion) electrochemical cells) arranged within the housing to provide particular voltages and/or currents useful to power, for example, one or more components of an xEV. As another example, battery modules in accordance with present embodiments may be incorporated with or provide power to stationary power systems (e.g., non-automotive systems).
Battery modules in accordance with the present disclosure may be susceptible to ingress of water or other fluids into the housing of the battery module. For example, the battery module may include thermal management features configured to route a coolant proximate to the housing of the battery module. The coolant may be liquid or vaporized water and may, for example, be capable of leaking (e.g., ingressing) into the housing. Furthermore, condensation may occur within a battery module due to temperature gradients and atmospheric conditions.
Accordingly, battery modules in accordance with the present disclosure include certain fluid management features (e.g., water management features) configured to gather fluid in a safe portion of the housing of the battery module. For example, a channel or recess (e.g., recessed portion) may be disposed on a bottom internal surface of the housing at or proximate to a low or lowest point on the bottom internal surface, such that fluid gathers within the channel or recess away from the electrochemical cells stored in the housing and away from other electrical components that may be disposed within, or extend into, an inside of the housing. Additionally or alternatively, the battery module may include certain fluid management features (e.g., water management features) configured to drain the fluid from the housing of the battery module. For example, a pinhole, a self-sealing port, a plunger seal, and/or a pressure relief seal may be disposed on the bottom internal surface of the battery module at or proximate to the low or lowest point on the bottom internal surface, such that fluid gathers proximate the pinhole, self-sealing port, or pressure relief seal and the pinhole, self-sealing port, or pressure relief seal drains the water (e.g., due at least in part to gravity) from the inside of the housing. The water management feature(s) are generally disposed proximate to the low or lowest point on the bottom internal surface of the housing to enable the fluid to be gravity fed toward and/or into the water management feature(s).
To help illustrate,
As discussed above, it would be desirable for a battery system 12 to be largely compatible with traditional vehicle designs. Accordingly, the battery system 12 may be placed in a location in the vehicle 10 that would have housed a traditional battery system. For example, as illustrated, the vehicle 10 may include the battery system 12 positioned similarly to a lead-acid battery of a typical combustion-engine vehicle (e.g., under the hood of the vehicle 10). Furthermore, as will be described in more detail below, the battery system 12 may be positioned to facilitate managing temperature of the battery system 12. For example, in some embodiments, positioning a battery system 12 under the hood of the vehicle 10 may enable an air duct to channel airflow over the battery system 12 and cool the battery system 12.
A more detailed view of the battery system 12 is described in
In other words, the battery system 12 may supply power to components of the vehicle's electrical system, which may include radiator cooling fans, climate control systems, electric power steering systems, active suspension systems, auto park systems, electric oil pumps, electric super/turbochargers, electric water pumps, heated windscreen/defrosters, window lift motors, vanity lights, tire pressure monitoring systems, sunroof motor controls, power seats, alarm systems, infotainment systems, navigation features, lane departure warning systems, electric parking brakes, external lights, or any combination thereof. Illustratively, in the depicted embodiment, the energy storage component 13 supplies power to the vehicle console 16 and the ignition system 14, which may be used to start (e.g., crank) the internal combustion engine 18.
Additionally, the energy storage component 13 may capture electrical energy generated by the alternator 15 and/or the electric motor 17. In some embodiments, the alternator 15 may generate electrical energy while the internal combustion engine 18 is running. More specifically, the alternator 15 may convert the mechanical energy produced by the rotation of the internal combustion engine 18 into electrical energy. Additionally or alternatively, when the vehicle 10 includes an electric motor 17, the electric motor 17 may generate electrical energy by converting mechanical energy produced by the movement of the vehicle 10 (e.g., rotation of the wheels) into electrical energy. Thus, in some embodiments, the energy storage component 13 may capture electrical energy generated by the alternator 15 and/or the electric motor 17 during regenerative braking. As such, the alternator 15 and/or the electric motor 17 are generally referred to herein as a regenerative braking system.
To facilitate capturing and supplying electric energy, the energy storage component 13 may be electrically coupled to the vehicle's electric system via a bus 19. For example, the bus 19 may enable the energy storage component 13 to receive electrical energy generated by the alternator 15 and/or the electric motor 17. Additionally, the bus 19 may enable the energy storage component 13 to output electrical energy to the ignition system 14 and/or the vehicle console 16. Accordingly, when a 12 volt battery system 12 is used, the bus 19 may carry electrical power typically between 8-18 volts.
Additionally, as depicted, the energy storage component 13 may include multiple battery modules. For example, in the depicted embodiment, the energy storage component 13 includes a lithium ion (e.g., a first) battery module 20 and a lead-acid (e.g., a second) battery module 22, which each includes one or more battery cells. In other embodiments, the energy storage component 13 may include any number of battery modules. Additionally, although the lithium ion battery module 20 and lead-acid battery module 22 are depicted adjacent to one another, they may be positioned in different areas around the vehicle. For example, the lead-acid battery module 22 may be positioned in or about the interior of the vehicle 10 while the lithium ion battery module 20 may be positioned under the hood of the vehicle 10.
In some embodiments, the energy storage component 13 may include multiple battery modules to utilize multiple different battery chemistries. For example, when the lithium ion battery module 20 is used, performance of the battery system 12 may be improved since the lithium ion battery chemistry generally has a higher coulombic efficiency and/or a higher power charge acceptance rate (e.g., higher maximum charge current or charge voltage) than the lead-acid battery chemistry. As such, the capture, storage, and/or distribution efficiency of the battery system 12 may be improved.
To facilitate controlling the capturing and storing of electrical energy, the battery system 12 may additionally include a control module 24. More specifically, the control module 24 may control operations of components in the battery system 12, such as relays (e.g., switches) within energy storage component 13, the alternator 15, and/or the electric motor 17. For example, the control module 24 may regulate amount of electrical energy captured/supplied by each battery module 20 or 22 (e.g., to de-rate and re-rate the battery system 12), perform load balancing between the battery modules 20 and 22, determine a state of charge of each battery module 20 or 22, determine temperature of each battery module 20 or 22, control voltage output by the alternator 15 and/or the electric motor 17, and the like.
Accordingly, the control unit 24 may include one or more processor 26 and one or more memory 28. More specifically, the one or more processor 26 may include one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more general purpose processors, or any combination thereof. Additionally, the one or more memory 28 may include volatile memory, such as random access memory (RAM), and/or non-volatile memory, such as read-only memory (ROM), optical drives, hard disc drives, or solid-state drives. In some embodiments, the control unit 24 may include portions of a vehicle control unit (VCU) and/or a separate battery control module.
Indeed, a partially exploded perspective view of one exemplary battery module 20 in accordance with the present disclosure is shown in
It should be noted that presently disclosed embodiments may be applicable to any battery module having the same or different configurations and/or orientations described above and in detail below. One of ordinary skill in the art would recognize that the components and examples used to describe battery modules in accordance with the present disclosure should not be construed to limit the present disclosure to those components and examples alone. Rather, the disclosed examples are merely intended to serve as non-limiting examples to facilitate discussion of the present disclosure.
In accordance with the present disclosure, the battery module 20 in
In the illustrated embodiment, the battery module 20 includes two columns of electrochemical cells 30 separated by a partition 65. Each column of electrochemical cells 30 may include one recessed portion 64 disposed below the column on the bottom internal surface 62 of the base structure 39 of the housing 31, below the electrochemical cells 30. Alternatively, in some embodiments, only one recessed portion 64 on the bottom internal surface 62 is included for the entire battery module 20. In some embodiments, recessed portions may be included on multiple internal surfaces (e.g., right, left, front, back, bottom) to accommodate variable battery orientations relative to gravity. In the illustrated embodiment, the recessed portion 64 extends from the open front side 40 of the base structure 39 toward the back side 42, in direction 66. It should be noted that the recessed portion(s) 64 may extend an entire length 68 of the bottom internal surface 62 (e.g., from the open front side 40 to the back side 62), or the recessed portion 64 may extend only a portion of the entire length 68 of the bottom internal surface 62. For example, the recessed portion 64 may extend approximately one quarter, approximately one half, or approximately three quarters of the entire length 68 of the bottom internal surface 62. Further, the recessed portion 64 may extend from the open front side 40 toward the back side 42 of the base structure 39, from the back side 42 toward the open front side 40, or otherwise between the open front side 40 and the back side 42.
The size, shape, and/or location of the recessed portion 64 may depend on a number of factors and may vary depending on the embodiment. For example, the size of the recessed portion 64 may depend on an amount of fluid expected to be in the inside 60 of the base structure 39 of the housing 31. Further, the location of the recessed portion 64 may depend on where the fluid is expected to gather. In general, the recessed portion 64 (or portions) is disposed at or proximate to a low or lowest point 70 on the bottom internal surface 62 (e.g., with respect to gravity), such that the fluid is gravity fed into the airspace defined by the recessed portion 64. In some embodiments, the lowest point 70 may be a lowest point of a particular region of the bottom internal surface 62. For example, the bottom internal surface 62 may include multiple regions, each having a lowest point 70. The battery module 20 may be disposed into the vehicle 10 in a particular orientation such that the recessed portion 64 is proximate the lowest point 70 of the bottom internal surface 62 (with respect to gravity), which enables the fluid to be gravity fed into the airspace defined by the recessed portion 64. The recessed portion 64 may include curved or beveled portions that cooperate to function as a funnel. Further, in some embodiments, the recessed portion 64 may be defined, in part, by a substantially flat surface disposed below the bottom internal surface 62, with sloped or angled surfaces extending between the bottom internal surface 62 and the substantially flat surface of the recessed portion 64. The sloped or angled surfaces may enable the fluid on the inside 60 of the housing 31 to travel toward the substantially flat surface of the recessed portion 64 and into the airspace defined by the recessed portion 64.
It should also be noted that, in some embodiments, the recessed portion 64, (and the airspace thereof) may retain fluid within the inside 60 of the base structure 39 of the housing 31 only temporarily. For example, during operation of the battery module 20, the inside 60 of the base structure 39 may become hot and may temporarily vaporize fluid gathered in the airspace of the recessed portion 64, such that the vaporized fluid may be present anywhere in the inside 60 of the base structure 39. When the battery module 20 is not operating, the fluid may condense and again gather in the airspace defined by the recessed portion 64 of the bottom internal surface 62. During the lifecycle of the battery module 20, more and more fluid may ingress into the inside 60 of the base structure 39 of the housing 31. Eventually, a volume of the fluid in the inside 60 of the base structure 39 may exceed a volume of the airspace defined by the recessed portion 64 on the bottom internal surface 62 of the base structure 39. Thus, during maintenance intervals, the snap on e-carrier 43 (See FIG. 3), or some other portion of the housing 31, may be temporarily removed for accessing the inside 60 of the housing 31 (or the base structure 39 thereof), such that the fluid may be removed from the airspace defined by the recessed portion 64. Indeed, in certain embodiments, a humidity sensor 72 may be disposed on the inside 60 of the base structure 39 and may alert an operator if humidity exceeds a pre-defined tolerance level. Additionally or alternatively, some other type of sensor (e.g., a water pressure sensor) may be used for determining if and when fluid levels exceed a tolerated amount on the inside 60 of the base structure 39. In some embodiments, one or more absorbent features (e.g., sponges) may be disposed in the recessed portion 64 to manage liquid distribution.
Further, in some embodiments, the battery module 20 may include water management features in addition to, or as an alternate for, the recessed portion 64 (and airspace thereof) described above. For example, a perspective view of a portion of the housing 31 of the battery module 20 of
In the illustrated embodiment, the opening 80 is disposed at or proximate to the low or lowest point 70 of the bottom internal surface 62 (or one region thereof, as previously described). For example, in some embodiments, the bottom internal surface 62 may be sloped slightly toward the opening 80. Thus, fluid on the inside 60 of the housing 31 is gravity fed toward the opening 80 and gravity fed through the opening 80. Further, depending on the embodiment, the housing 31 may include both the opening 80 and the recessed portion 64 (e.g., with the opening 80 disposed in the recessed portion 64), such that the fluid is gravity fed into the airspace defined by the recessed portion 64 and gravity fed through the opening 80. In other embodiments, the base structure 39 may only include the opening 80, as described above.
Further, in some embodiments, the housing 31 (e.g., the base structure 39 of the housing 31) may include some type of seal, sealing mechanism, or sealing assembly (e.g., self-sealing port) for selectively sealing the opening 80. For example, a bottom perspective view of a portion of the housing 31 of the battery module 20 of
Generally, the multiple holes 96 disposed annularly through the extension 94 and about the central opening 98 (and, thus, around the stem 100 and the protruding head 102 of the plunger device 90) fluidly couple the inside 60 of the housing 31 (e.g., through the multiple holes 96) with a cavity 104 of the opening 80. The cavity 104 is configured to receive fluid from the inside 60 of the base structure 39 of the housing 31 and to retain the fluid as the fluid presses against a flexible plunger head 106 of the plunger device 90. The flexible plunger head 106 includes an annular ridge 108 configured to contact the bottom external surface 84 of the bottom side 34 of the base structure 39 of the housing 31. The annular ridge 108 seals the cavity 104 from the external area 86 outside of the housing 31 (or base structure 39 thereof). However, as more fluid gathers within the cavity 104, a fluid pressure against the flexible plunger head 106 increases. Once the fluid pressure exceeds a tolerance of the flexible plunger head 106, the flexible plunger head 106 will flex open, causing the annular ridge 108 to be separated from the bottom external surface 84. While the flexible plunger head 106 is flexed open in an open position (e.g., with the annular ridge 108 separated from the bottom external surface 84), the fluid drains from the cavity 104. As the fluid drains from the cavity 104, the fluid pressure against the flexible plunger head 106 decreases. Once the tolerance of the flexible plunger head 106 exceeds the fluid pressure of the fluid in the cavity 104 against the flexible plunger head 106, the flexible plunger head 106 flexes back into a closed position, causing the annular ridge 108 to contact, and seal against, the bottom external surface 84 of the bottom side 34 (e.g., bottom wall) of the base structure 39.
A cross-sectional side view of the opening 80 having the plunger device 90 of
In some embodiments, the plunger device 90 may include some other flexible member configured to be calibrated to respond to a fluid pressure (e.g., to drain the fluid) within the cavity 104 of the opening 80. For example, in
It should be noted that the plunger device 90 and the corresponding opening 80 may be configured in a manner other than what is shown in
For example, a cross-sectional perspective view of an embodiment of the base structure 39 (e.g., of the housing 31) of the battery module 20 of
The pressure relief seal assembly 120 includes a pressure ball 127 disposed in the cross-wise segment 124 of the opening 80. The pressure ball 127 is configured to selectively seal the first segment 122 from the second segment 126, thus selectively sealing the inside 60 of the housing 31 from the external area 86 outside of the housing 31. For example, a spring 128 is disposed in the cross-wise segment 124 and exerts a biasing force against the pressure ball 127 in direction 130, as indicated by arrow 132. However, as fluid gathers on the inside 60 of the base structure 39 of the housing 31, the fluid drains into the first segment 122 and the right side of the cross-wise segment 124 in the illustrated embodiment. The fluid exerts a fluid pressure against the pressure ball 127 opposite to direction 130, as indicated by arrow 134. If the fluid pressure (arrow 134) exceeds the biasing force (arrow 132) of the spring 128, the pressure ball 127 will move opposite to direction 130. As the pressure ball 127 moves over and beyond at least a portion of the second segment 126 (e.g., opposite to direction 130), the fluid is enabled to drain through the first segment 124, through the cross-wise segment 124, and through the second segment 126 to the external area 86 outside of the base structure 39 of the housing 31. As the fluid drains from the inside 60 of base structure 39 to the external area 86 outside of the housing 31, the fluid pressure against the pressure ball 127 decreases, and the biasing force of the spring 128 may eventually overcome or exceed the fluid pressure. Thus, the pressure ball 127 moves in direction 130 until the pressure ball 127 selectively seals the first segment 122 from the second segment 126, as previously described.
It should be noted that the pressure ball 127, in the illustrated embodiment, may be some other shape disposed within the cross-wise segment 124. For example, in the illustrated embodiment, the pressure ball 127 is shown as a sphere. However, in another embodiment, the pressure ball 127 may be any shape capable of sealing the first segment 122 from the second segment 126 within the cross-wise segment 124. For example, the pressure ball 127 may be a pressure cylinder with circular faces facing in direction 130 and opposite to direction 130, or any other shape capable of sealing within the cross-wise segment 124. Further, in the illustrated embodiment, to block the biasing force of the spring 128 from causing the pressure ball 127 to move too far in direction 130 (e.g., up to and beyond at least a portion of the first segment 122), a lip or seat 142 is disposed in the cross-wise segment 124. The seat 142 restricts a cross-sectional area of the cross-wise segment 124 such that the pressure ball 127 contacts the seat 142 and is blocked from moving in direction 130 up to or beyond the first segment 122. This contact also provides a seal.
It should also be noted that the first segment 122 (e.g., first vertical segment), the cross-wise segment 124 (e.g., intervening segment, transverse segment, horizontal segment), and the second segment 126 (e.g., second vertical segment) may be otherwise oriented. For example, the first segment 122 may be angled with respect to direction 143, the cross-wise segment 124 may be angled with respect to direction 130, and the second segment 126 may be angled with respect to direction 143. In general, the segments 122, 124, 126 are configured to utilize gravity and fluid pressure to drain the fluid from the inside 60 of the base structure 39 of the housing 31. Any angles for the segments 122, 124, 126 capable of gravity feeding the fluid through the segments 122, 124, 126 by utilizing fluid pressure against the pressure seat 127 is in accordance with the present disclosure. For example, embodiments of the present disclosure having a pressure relief seal assembly 120 with segments oriented in various directions and/or configurations are shown in
One or more of the disclosed embodiments, alone or in combination, may provide one or more technical effects useful in the manufacture of battery modules, and portions of battery modules. In general, the disclosed battery modules (and housings/base structures thereof) include water management features generally disposed at a low or lowest point in a bottom internal surface of a bottom end of the housing. The water management features are configured to receive gravity fed fluid from inside of the housing, such that the water management features may retain and/or drain the fluid safely away from electrochemical cells and other components of the battery module. The water management features generally provide safe retention and draining of fluid from the inside of the housing of the battery module such that the fluid does not interfere with, for example, electrical components of the battery module and electrochemical cells thereof. The water management features are configured to be substantially contained within a bottom side of the base structure of the housing of the battery module, such that the housing (and water management features thereof) is compact and the water management features do not excessively contribute to an increased volume (and thus, a decreased energy density) of the battery module. The technical effects and technical problems in the specification are exemplary and are not limiting. It should be noted that the embodiments described in the specification may have other technical effects and can solve other technical problems.
While only certain features and embodiments have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the disclosed subject matter. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation.