Patent Publication Number: US-2023140898-A1

Title: Battery for use in a watercraft

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/079,826 filed Sep. 17, 2020 and U.S. Provisional Application No. 63/014,014 filed Apr. 22, 2020, which are incorporated herein by reference in their entirety. The related U.S. application Ser. No. 17/077,784 filed Oct. 22, 2020, now issued as U.S. Pat. No. 10,946,939; U.S. application Ser. No. 17/162,918 filed Jan. 29, 2021; U.S. application Ser. No. 17/077,949 filed Oct. 22, 2020; the application titled “PROPULSION POD FOR AN ELECTRIC WATERCRAFT” filed concurrently herewith on Apr. 22, 2021 as U.S. Application Number TBD; and the application titled “WATERCRAFT DEVICE WITH HYDROFOIL AND ELECTRIC PROPULSION SYSTEM” filed concurrently herewith on Apr. 22, 2021 as U.S. Application Number TBD are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     This disclosure relates to rechargeable battery modules and, in particular, to rechargeable battery modules for use in electric hydrofoiling watercraft. 
     BACKGROUND 
     Batteries powering watercraft face extreme conditions, particularly for personal watercraft. Due to the wet environment in which watercraft operate, batteries and associated electronics must be sealed or housed within watertight compartments. Some watercraft may operate in harsh environments, such as shore-break, where typical waterproofing methods are prone to fail. On watercraft such as electric surfboards jet ski devices, the watercraft is exposed to salt spray, shock and vibration, rapid temperature changes and transient electrical loading. These conditions can lead to battery pack failures, which are particularly undesirable for personal watercraft because they could strand the operator of the watercraft. Battery fires are also known to occur in some existing rechargeable battery systems. 
     Rechargeable batteries currently require a significant charging time, making it desirable to provide a modular battery unit that can be swapped out of the watercraft during charging. The use of modular battery units, however makes it more difficult to provide adequate sealing or watertight compartments, because the battery unit is expected to be removed and replaced frequently. 
     The challenges described above are especially applicable in electrically powered hydrofoiling watercraft. An example prior art embodiment is illustrated in  FIG.  20   . Such devices typically include a board  1000  with a watertight compartment (cavity  1020  with cover  1010 ) that contains electrical components such as electronic motor control components  1022 , electrical connectors  1024 , and the battery (not shown) that powers the watercraft. Electrical components such as the motor controller  1022  and connectors  1024  within the cavity  1020  of the board are easily accessible to the user, which is undesirable. For example, when inserting the battery into or removing the battery from the board cavity  1020 , the user may inadvertently or accidentally move or damage electrical components ( 1022  and  1024 ) and cooling lines  1028  housed within the board cavity  1020 . 
     In the known design, the board includes electrical wiring/electrical conduits within the interior body of the board. For example, electrical conduits may be needed within the interior body of the board for transmitting electrical signals between the electronic speed controller components (for example  1022  shown in  FIG.  20   ) and the motor (mounted on a strut below the board). In another example, U.S. application Ser. No. 15/700,658, filed on Sep. 11, 2017 and issued as U.S. Pat. No. 10,597,118 illustrates a design with two wells on a top surface of the board, and a trough for cables running between the two wells. 
     The known design presents mechanical challenges as well. In the example shown in  FIG.  20   , the cover  1010  of board cavity must be designed to provide sufficient structural support for supporting weight of rider standing on cover. The board cavity  1020  and cover  1010  are required to be designed to include additional water sealing components/features, for example the thick sealing ring  1026 , to prevent water ingress into the board cavity when the cover is in its closed position. This adds weight and complexity to the board design. The battery (not shown) must also be secured within the compartment  1020 , for example, using strap  1027  and clip  1025 . Both the strap  1027  and clip  1025  are secured to the board, which requires structural reinforcement of the board  1000 . 
     Inserting the battery into or removing the battery from board cavity  1020  necessarily requires the user to open cover  1010 , which exposes sensitive electronic components such as the motor controller  1022  housed within the cavity  1020  to undesirable external environmental elements (e.g., while cover is open). These elements could include, for example sand, rain, seawater, etc. Any water able to ingress into the board cavity  1020  may cause a variety of damage to the electronic components housed in the cavity, including, for example, short-circuiting of electrical components, corrosion of electrical components. In view of the problems described above an improved modular battery unit and watercraft system are desirable. 
     SUMMARY 
     Generally speaking and pursuant to these various embodiments, a self-contained battery assembly is provided that is configured to be removably coupled to a watercraft. The battery assembly comprises a waterproof housing including a top portion and a bottom portion that houses a plurality of battery modules. The battery assembly includes a plurality of battery separators manufactured from a material to provide passive protection against thermal event propagation and an electronics module. Each of the battery modules is surrounded on four sides by the one or more of the plurality of battery separators. The plurality of battery separators are disposed within the housing and in physical contact with the top portion and the bottom portion. 
     In some embodiments, the self-contained battery assembly further comprises a deck pad disposed on an outer surface of the top portion of the housing, such that the self-contained battery assembly is configured to serve as part of a top surface of the watercraft when coupled to the watercraft. In one example, the self-contained battery assembly is configured to serve as part of a top surface of the watercraft when coupled to the watercraft with the battery separators forming a structural element such that the battery module is configured to support an operator of the watercraft. 
     In some embodiments, the plurality of battery separators includes a plurality of flat sheets forming elongate rectangular separators, with each of the flat sheets having at least one slot such that the plurality of flat sheets slot together to form a lattice. In some embodiments, the self-contained battery assembly further comprises at least one tray with two or more pockets to receive a corresponding two or more of the plurality of battery modules. The at least one tray has a plurality of slots to receive two or more of the plurality of battery separators. The self-contained battery assembly further may include an electrically insulative sheet configured to isolate the tray from an inside surface of the waterproof housing. In some embodiments, the self-contained battery assembly floats in water. 
     In some embodiments, the self-contained battery assembly further includes a carrying handle pivotally coupled to the housing with at least one arcuate slot formed in the carrying handle. The self-contained battery assembly is configured to be mechanically coupled to the watercraft by engagement of the at least one arcuate slot of the carrying handle with at least one latching pin disposed on the watercraft. 
     In some embodiments, the self-contained battery assembly further comprises at least one printed circuit board with a plurality of fuses with one or more fuses from the plurality of fuses corresponding to each of the plurality of battery modules. The self-contained battery assembly further comprises an electronics module with first circuitry configured to detect fusing of one or more of the plurality of fuses and second circuitry configured to detect at least one error condition and disconnect the self-contained battery assembly. In some embodiments, the electronics module reports a status of fusing of one or more of the plurality of fuses. In some embodiments, the self-contained battery assembly further comprises a temperature sensor mounted to the at least one printed circuit board, the temperature sensor being configured to monitor a temperature within the housing. In some embodiments, self-contained battery assembly further comprises sensors configured to detect water or humidity inside the housing. 
     In some embodiments, the electronics module of the self-contained battery assembly contains an inertial measurement unit configured to identify large transient accelerations. In some forms, the inertial measurement unit is configured to remain active when the self-contained battery assembly is not coupled to the watercraft. 
     An intelligent power unit is provided that is configured to be removably coupled to a watercraft. The intelligent power unit comprises a waterproof housing and a plurality of battery modules disposed within the housing. The intelligent power unit further includes a plug disposed on the housing that is configured to be removably coupled to the watercraft. The intelligent power unit includes an electronic module disposed within the housing. The electronic module includes a wireless transceiver configured to communicate via a protocol selected from the list consisting of Bluetooth, Wi-Fi, and cellular data. The electronic module is configured to report a status data of one or more of the battery modules to a remote location. 
     In some embodiments, the intelligent power unit further comprises a GPS unit communicatively coupled to the electronic module, the GPS unit being configured to capture a position of the intelligent power unit. The electronic module is configured to report the position of the intelligent power unit with the status data. 
     In some embodiments, the intelligent power unit comprises at least one accelerometer communicatively coupled to the electronic module. The intelligent power unit further includes drop detection circuitry on the electronic module that is configured to detect large transient accelerations. The electronic module includes a low power mode in which the drop detection circuitry is configured to remain active when the self-contained battery assembly is not coupled to the watercraft. 
     An intelligent power unit is provided that is configured to be removably coupled to a watercraft. The intelligent power unit includes a waterproof housing and a plurality of battery modules disposed within the housing. The intelligent power unit further includes a plug disposed on the housing that is configured to be removably coupled to the watercraft. The intelligent power unit includes an electronics module that is configured to monitor a digital signal, passive resistance, or capacitance to determine whether the intelligent power unit is connected to the watercraft. The electronics module includes circuitry to disconnect power from one or more pins of the plug of the battery unit upon determining that the intelligent power unit is not connected to the watercraft. 
     In some embodiments, the intelligent power unit further comprises an inertial measurement unit communicatively coupled to the electronics module, where the inertial measurement unit is configured to determine an orientation of the intelligent power unit. The electronics module is configured to disconnect power to the plug when the orientation is not within a predetermined range of values associated with operational use of the watercraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a top perspective view of an electrically powered hydrofoiling surfboard. 
         FIG.  2    is an exploded top perspective view of the of an electrically powered hydrofoiling surfboard of  FIG.  1   . 
         FIG.  3    is a top perspective view of a container housing battery cells and electronics. 
         FIG.  4    is a bottom perspective view of a container housing battery cells and electronics. 
         FIG.  5    is an exploded top perspective view of a container housing battery cells and electronics. 
         FIG.  6    is an exploded bottom perspective view of a container housing battery cells and electronics. 
         FIG.  7    is a bottom perspective view of a top portion of a container for housing battery cells and electronics. 
         FIG.  8    is top perspective view of a bottom portion of a container for housing battery cells and electronics. 
         FIG.  9 A  is an exploded bottom perspective view of a container for housing battery cells and electronics. 
         FIG.  9 B  is an exploded top perspective view of the container illustrated in  FIG.  9 A . 
         FIG.  10    is a cutaway side view, bisecting a container for housing battery cells and electronics along a longitudinal plane. 
         FIG.  11    is a top perspective view of a cassette including battery cells and associated electronics. 
         FIG.  12 A  is an exploded top perspective view of a cassette including battery cells and associated electronics. 
         FIG.  12 B  is an exploded front elevation of the cassette illustrated in  FIG.  12 A . 
         FIG.  13 A  is a top perspective view of a tray designed to receive battery cells and associated fuse circuits. 
         FIG.  13 B  is a bottom perspective view of the tray illustrated in  FIG.  13 A . 
         FIG.  14    is an exploded top perspective view of a cassette including battery cells and associated electronics, omitting the top tray and fuse circuitry. 
         FIG.  15    is a top plan view of a cassette including battery cells and associated electronics. 
         FIG.  16    is a block diagram illustrating components included within an intelligent power unit. 
         FIGS.  17 A-D  show a side partial cutaway view of a container including a handle used to attach the socket of the container to the plug of the watercraft. 
         FIGS.  18 A-D  show a side partial cutaway view of a container including a handle used to remove the socket of the container from the plug of the watercraft. 
         FIGS.  19 A-D  show a side partial cutaway view of a container including a handle used to install the socket of the container into the plug of the watercraft. 
         FIG.  20    is a top rear perspective view of a prior art watercraft having a compartment for housing a battery and electronics. 
     
    
    
     DETAILED DESCRIPTION 
     A modular battery unit disclosed herein provides a watertight container that can be connected and disconnected from a personal watercraft in wet, sandy, muddy, or otherwise harsh environments. The modular battery unit&#39;s watertight container is designed to prevent water, humidity, or other environmental contaminants from entering the housing. The modular battery unit may include passive safety features designed to enhance safety of the battery unit when used in harsh conditions. These safety features may include battery separators designed to insulate neighboring cells if a given battery cell experiences a thermal runaway. To reduce the risk of exploding the housing, the housing may include pressure relief regions designed to release high pressure air from the housing away from an operator of the personal watercraft. 
     In a preferred embodiment illustrated in the block diagram shown in  FIG.  16   , the modular battery unit  302  is an intelligent power unit that includes electronics such as processor  614  and memory  612  for managing the battery cells and controlling the watercraft. The intelligent power unit includes active safety systems including an electronically resettable battery cutoff  616  that disables the battery unit in the event one or more of the battery cells malfunctions. The intelligent power unit preferably includes sensors such as a temperature sensor  628 , humidity sensor  622 , and water sensor  621  to identify undesirable operating conditions within the battery unit. An inertial measurement unit  627  or accelerometers can detect large transient accelerations such as those caused when the intelligent power unit is dropped and strikes a hard surface. Such a drop could damage the watertight housing or the internal components of the intelligent power unit, and therefore is used as a trigger to disable the intelligent power unit using the battery cutoff  616  until the intelligent power unit can be evaluated by a qualified technician. Alternative embodiments may include a pressure sensor to detect a breach of the watertight container  302 , as discussed below. Alternative embodiments may include a smoke sensor to detect fire within the container  302 , e.g., caused by thermal runaway of a battery cell or other malfunction within the battery unit. 
     The intelligent power unit may also include sensors to detect the presence of an operator, such as a sensor  624  that detects a magnetic interlock device, which disables the watercraft if the operator falls overboard. Alternative embodiments may detect the operator using a strain gauge  626  on the intelligent power unit, an upward-facing radar  623 , or a pressure plate  625 . The intelligent power unit may include global navigation satellite system (GNSS) receiver circuitry  630  to determine the position of the watercraft or the intelligent power unit. The intelligent power unit may also include transceivers  640  for sending and receiving data at the watercraft, using known protocols such as Bluetooth, Wi-Fi, or cellular data modems. These and other active safety features of the preferred intelligent power unit are described below. 
     A watercraft  300  is shown in  FIGS.  1  and  2   , particularly an electrically powered hydrofoiling surfboard device  300  including a board or flotation portion  305 , a strut  308 , a propulsion unit  310  including an electric motor and propeller attached to the strut  308 , and hydrofoils  311  attached to the strut  308 . The watercraft  300  is similar in some aspects to the jetfoiler devices described in U.S. Pat. No. 10,597,118 and U.S. patent application Ser. No. 16/543,447, the contents of which are incorporated by reference herein in their entirety. In the illustrated example, the board  305  is made of a material or is sealed such that it has a sufficiently low density that it floats in water or is buoyant. The board  305  may prevent the watercraft  300  from sinking where the other components of the watercraft do not otherwise float. The upper surface of the flotation portion  305  is a deck  306  that may support a rider or user of the watercraft  300 . The deck  306  is preferably covered with a deck pad  307 , which provides a resilient surface allowing an operator of the watercraft to comfortably sit, kneel, or stand on the deck  306  of the board. In preferred embodiments, the deck pad  307  is an expanded rubber mat adhered to the board  305 . 
     The watercraft illustrated in  FIGS.  1  and  2    differs from previously described electric hydrofoiling surfboards such as the jetfoiler device. As described above, prior devices utilized a water-tight compartment to enclose batteries and other sensitive electronics. In contrast, the watercraft  300  includes an open cavity  312  within the flotation portion  305  sized to receive container  302 . In the illustrated device, the upper surface  314  of the container  302  forms a portion of the deck  306  of the watercraft  300  when inserted into the cavity  312 . For example, the upper surface  314  of the container  302  is substantially coplanar with the top surface or deck  306  of the flotation portion  305 , such that the top surface of the container  302  effectively forms a part of the deck  306  or the top surface of the flotation portion. A person standing on the deck  306  should notice little difference between the upper surface  314  of the container  302  and the deck  306  of the flotation portion  305  when, for example, their foot is partially on the deck  306  of the flotation portion  305  and partially on the upper surface  314  surface of the container  302 . In preferred embodiments, the upper surface  314  of the container  302  is covered with deck pad  307  to match the remainder of the deck  306 . 
     The design of the watercraft  300  benefits in several aspects from the design of the container  302 . The strut  308  is designed, for example to allow water into an internal cavity of the strut where electrical wires are located. This “wet strut” concept is beneficial for battery cooling, because it uses power wires running to the motor  310  to conduct heat away from battery. The electrical wires in strut (connected to the container  302 ) can be used to conduct internal heat from the battery away from the container, and the wires are cooled by the surrounding water (e.g., ocean water). In preferred embodiments, the electrical wires are insulated with PTFE (teflon) rather than rubber insulating materials. The use of PTFE reduces an outer diameter of the cable jacket to provide better heat transfer. Using PTFE, a cable jacket thickness can be less than 1 mm, whereas conventional jacket materials are typically 2× thicker (or more). In addition, PTFE has a higher melting point that rubber insulating materials that are typically used. 
     The container  302  is designed to be watertight and may be formed of a resilient and tough material, such as a plastic or carbon composite to support a rider. Because the battery unit  302  generates heat when the enclosed battery cells  550  (illustrated in  FIGS.  12  and  14   ) charge or discharge, the container  302  is preferably designed with heat transfer surfaces (not shown) to conduct heat away from the battery cells. Because the container  302  is watertight, it is preferably designed with a rupture disc and tortuous exhaust pathway (not shown), allowing pressure to dissipate safely from the container  302  in the event of a temperature increase caused by thermal runaway within the battery cells  550 . For example, a weak spot or rupture plate in the top housing portion  370  or bottom housing portion  380  can deliberately rupture in the event of an internal battery malfunction or thermal runaway, directing any expelled material away from an operator of the watercraft  300 . In alternative embodiments Gore vents may be used in addition to the rupture plates to dissipate pressure without compromising watertightness of the container  302 . 
     The disclosed design thus advantageously eliminates the need for a separate watertight compartment. In the illustrated device  300 , the container  302  is rigidly coupled to a strut  308 . This approach avoids several engineering challenges present in prior devices, where batteries were stowed in a water-tight compartment and electrically connected to a motor affixed to the strut via flexible cables running through the board. The present design advantageously eliminates the need for a cable harness within the board  305  and therefore simplifies manufacture of the board. Instead of running through cables within the board  305 , electrical power from a battery or other power source and communication signals from a transceiver are transmitted directly from the container  302  through the socket  100  to the plug  200  and through wires within the strut  308 . A motor and transceiver in the propulsion unit  310  receives the necessary electrical power and communication signals. 
     In addition, the disclosed design reduces the need for structural components and mechanical connections integrated within the board  305 , which simplifies manufacture of the board. Prior devices required substantial layup around structural elements such that a board could connect first to the strut and second to form a watertight compartment for a battery. In the design illustrated in  FIGS.  1  and  2   , the flotation portion  305  is sandwiched between the upper portion  309  of the strut  308  and the container  302 . This distributes stress throughout a larger area of the board and therefore reduces the need for carbon fiber or fiberglass layup to incorporate metallic or other rigid structural members within the board. Further, the disclosed design reduces the need for close dimensional tolerances in the board  305 . The illustrated design is also advantageous for disassembly and transport of the watercraft  300 . For transport of the device  300 , detaching the strut  308  from the board  305  is desirable. Many quick-release designs, however, require incorporating tight dimensional tolerances in the board. In the disclosed design, the container  302  is quickly and securely connected directly to the rigid structures of the strut  308 , which may compress the board  305  to form a tight connection between the strut  308 , the container  302 , and the board  305 . 
     Although not illustrated, other embodiments incorporate a cavity in a bottom surface or rear surface of the flotation portion  305 . Although these bottom or rear loading embodiments beneficially reduce the need for a cable harness within the flotation portion  305 , they do not necessarily provide the structural advantages described above. Other aspects of the illustrated watercraft  300  remain substantially the same, specifically including the manner in which the connector  50  directly connects the container  302  to the strut  308 . Preferably in these embodiments, an outside surface of the container is substantially coplanar with the outside surface of the flotation portion  305 , which additionally serves to reduce complexity in the flotation portion  305  by eliminating the need for a compartment door hatch. 
     The watercraft may also be a boat, an electric surfboard, a jet ski, or any device for use on the water that includes a battery and/or other electrical equipment, with similar benefits. While the example application above shows the container  302  within the deck  307  of the hydrofoiling device, the container  302  may similarly be inserted into the deck of another watercraft  300 , for example, a boat. In other examples, the container  302  similarly attaches to another surface of the watercraft  300 , for example, the upper surface  302  forms a portion of an internal wall or the exterior surface of the watercraft (e.g., a jetski). In some embodiments, the upper surface  314  is not planar but matches the contour of the surface to which it is attached. For example, where the container  302  is attached to a cavity in a curved surface, the upper surface  314  of the container  302  may match the curvature of the curved surface, such that the presence of the container  302  is discrete. 
       FIGS.  3 - 4    provide external views of the container  302 . The container  302  is a watertight container that may house a rechargeable battery and associated safety features. In the embodiment shown, a socket  100  is located within an end  322  of the container  302 . A corresponding plug  200  is attached to the upper end  309  of the strut  308 , as illustrated in  FIG.  2   . The contact pins within the plug  200  are electrically coupled to an electric motor (e.g., of the propulsion unit  310 ) and an electronic speed controller attached to the strut  308 . The contact pins of the plug  200  are configured to contact the pin connectors of the socket  100  when the plug  200  is inserted into the socket  100  of the container  302 . The pin connectors of the socket  100  are electrically coupled to the battery and electronics housed within the container  302 . The components of the socket  100  and plug  200  are discussed in detail in U.S. patent application Ser. No. 17/077,784, filed on Oct. 22, 2020, and now issued as U.S. Pat. No. 10,946,939, which is hereby incorporated by reference in its entirety. 
     In use, the container  302  may be positioned within the cavity  312  of the watercraft such that the socket  100  receives the plug  200 . This provides one or more electrical pathways between the container  302  and the strut  308 . An electrical pathway may extend from the battery within the container  302  to the electric motor of the propulsion unit  310  attached to the strut  308 . Another electrical pathway may extend between the transceiver of the container  302  and a transceiver associated with an electronic speed controller attached to or enclosed within the strut  308 . In one form, the plug  200  is attached via holes  280  such that the plug  200  may pivot slightly to aid in inserting the plug  200  into the socket  100 . When the battery of the container  302  needs to be removed (e.g., to be recharged or replaced) the container  302  is removed from the cavity  312  of the watercraft  300 , disconnecting the socket  100  from the plug  100 . Because both the socket  100  and the plug  200  include seals to prevent fluid from passing through the socket  100  or plug  200  even when the plug  200  is not inserted into the socket  100 , the container  302  may be removed even in wet environments, for example, when the watercraft  300  is still within the water. 
       FIGS.  5  and  6    illustrates external components of the container  302  in the preferred embodiment, including bottom housing portion  380  and top housing portion  370 . The container  302  includes user interface features, including a battery charge indicator  362 , mounted within a battery indicator cavity adjacent to the handle  330 . In the preferred embodiment, the battery charge indicator  362  includes a row of LED lights  154  mounted on a connector circuit board  150 . When all lights  154  are lit the indicator  362  communicates to the operator that the battery is fully charged. As charge in the battery depletes, an increasing number of the lights  154  will turn off. In some examples, the lights  154  flash or light with different colors to indicate low charge. 
     Magnetic connection points  360  retain a magnetic interlock key. A sensor is located within the container beneath the magnetic connection point to detect presence of a magnetic interlock key that is configured to be attached via a tether to the operator while riding the watercraft. If the operator falls off the watercraft, the tether pulls the magnetic interlock key free from the magnetic connection point, causing circuitry in the container  302  to disable the watercraft. 
     A pivoting handle  330  allows the operator to remove the container  302  from the watercraft. The bar  337  is assembled into the hole  376  in the top housing portion  370 . The bar  337  provides the pivot axis for the handle  330 . Both the bar  337  and the handle grip  332  are attached to side panels  334  using fasteners such as the screws and washers  338  (shown in  FIG.  6   ). By pulling on the handle grip  332 , the operator rotates the handle upwards and disengages the container  302  from the watercraft. Operation of the handle  330  is described in greater detail below. 
     The socket  100  includes pins  116  that are soldered to pads (e.g.,  156 ) in the connector circuit board  150 . The pins  116  are fixed within the socket, as discussed in U.S. patent application Ser. No. 17/077,784. Separate external pins ( 142  in  FIG.  10   ) receive plug pins when the container  302  is affixed to the watercraft  300 . The socket  100  mounts within the bottom housing portion  380  and forms a watertight seal between the socket  100  and the lower housing portion  380 . 
       FIG.  6    illustrates additional features of the container  302 . The top housing portion  370  includes a series of transverse ridges  374  and longitudinal ridges  372 . These ridges allow the external surface (i.e., top  314 ) of the container  302  to support heavy weight, for example operators up to 300 lbs. standing on top of the container  302  while riding the watercraft  300 . The longitudinal ridges  372  and transverse ridges  374  transfer weight to the battery cassette  500  (shown in  FIG.  9   ) and more specifically to the vertical fire suppressors barriers  530  and  540  (shown in  FIGS.  12  and  14   ), providing even distribution of weight. In this way, the container  302  is a structural battery box, capable of supporting loads applied to the deck  306  of the watercraft  300 . 
     The bottom housing portion  380  includes a series of channels  381  configured to receive isolation strips  387  (shown in  FIG.  9   ). In the preferred embodiment, the isolation strips  387  are rubber, selected to dampen and isolate vibration between the flotation portion  305  and the container  302 . The isolation strips  387  are designed to act as dampers for the mass at the top of the strut  308 , in addition to protection of the battery components and protection of the board cavity  312 . 
     The top housing portion  370  is preferably a thin-walled structure having a substantially uniform wall thickness suitable for injection molding from plastic or composite materials, as illustrated in  FIG.  7   . A pair of wings  378  extends outward from the top surface  314  on either side of the pivot hole  376 . The wings  378  reduce the chance an operator of the watercraft  300  could step on or otherwise accidently push down on the sides  334  to open the handle  330 . A series of holes (e.g.,  379 ) are placed around the perimeter on the underside of the top housing portion  370 . Fasteners  388  (shown in  FIG.  9   ) extend through complementary holes (e.g.,  389  shown in  FIG.  8   ) in the bottom housing portion  380  and are threaded into the holes  379  to fasten the top housing portion  370  to the bottom housing portion  380  and form a continuous watertight seal around the perimeter of the housing. 
     The bottom housing portion  370  is preferably a thin-walled structure having a substantially uniform wall thickness suitable for injection molding from plastic or composite materials, as illustrated in  FIG.  8   . The bottom housing portion  380  includes a shallow transverse ridge  384  and longitudinal ridges  382 . As discussed above, channels  381  are disposed on the bottom housing portion. The broad ridges  386  are the projection of the channels  381  into the interior space of the bottom housing portion  380 . The transverse ridge  384 , longitudinal ridges  382 , and broad ridges  386  provide structural rigidity and are a surface for the battery cassette  500  (shown in  FIG.  9   ) to rest upon. 
       FIGS.  9 A and  9 B  illustrate the components of the container  302 . The deck pad  307  is affixed to the top housing portion  370 . A resilient seal  371  is disposed between the top housing portion  370  and the bottom housing portion  380 . A battery cassette  500  is sandwiched between the top housing portion  370  and the bottom housing portion  380 , and fully enclosed within the container  302 . While one cassette  500  is shown, in other embodiments, several battery cassettes  500  may be disposed within the container  302  and electrically connected to one another. The container is preferably fully sealed, with a positive pressure (relative to atmosphere) to reduce the likelihood of water ingress. In alternate embodiments, Gore vents in the container  302  may allow internal the container pressure to be equalized to external pressure without allowing water ingress. 
     The battery cassette  500  includes top insulator  504  and bottom insulator  502 , both of which are constructed from a sheet of fiber reinforced fire resistant sheet. The top insulator  504  and bottom insulator  502  protect the battery cassette  500  from electrical shorts and provide thermal protection between the cells  550  (shown in  FIG.  12   , for example) and the outer housing portions  370  and  380 . 
     A top battery management system  525  mounts to the top surface of the battery cassette  500 . The top battery management system  525  includes sensing inputs for each parallel bank of battery cells  550 , and includes bank-level fusing to protect the battery cells from shorts or other cell malfunctions at the module level. 
     The top housing portion  370  is fastened to the bottom housing portion  380  using screws  388 , which pass through holes  389  in the bottom housing portion  380  and thread into threaded inserts  381  disposed in the holes  379  in the top housing portion  370 . The threaded inserts  381  can either be molded into the top housing portion  370  or installed after molding. 
     Isolation strips  387  are disposed in channels provided in the lower housing portion  380 , as discussed above. The socket  100  receives pins  116  (labeled in  FIG.  5   ) and mounts to the connector board  150  as discussed above. Handle  330  pivots within the hole  376  (labeled in  FIG.  5   ), within the top housing portion  370  as discussed above. 
       FIG.  10    illustrates how the components of the container  302  fit together when assembled. The resilient seal  371  is illustrated in cross-section between the top housing portion  370  and the bottom housing portion  380 . One of the fasteners  389  is also illustrated, passing through a boss located at the perimeter of the bottom housing portion  380 , and threaded into the top housing portion  370 . 
     The battery cells  550  are substantially cylindrical. The anode end  551  and the cathode end  552  of each battery cell  550  are received in a top or bottom tray  520 / 560 . Top cell connection boards  510  are stacked on top of the top tray  520 , and bottom cell connection boards  570  are beneath the bottom tray  560 . In the preferred embodiment, the top cell connection boards  510  are printed circuit boards (PCBs) that include a nickel tab  512  and a fuse  513  for each battery cell  550 , and the bottom cell connection boards  570  are printed circuit boards (PCBs) that include a nickel tab  572  and a fuse (not shown) for each battery cell  550 . In the preferred embodiment, a separate fuse is provided for each battery cell  550 , for example fuses  513  and corresponding fuses (not shown) mounted on a bottom cell connection boards  570 . In alternative embodiments, the nickel tabs  512  and  572  may have a shape such that the tabs  512  and  572  function as a fuse. 
     The connector pins  116  are illustrated in cross-section, attached to the connector board  150 . Within the socket  100 , a first end of the external connectors  142  receive the connector pins  116 . A second end of the external connectors  142  are configured to receive pins from a plug mounted on the top of the strut  308 . 
       FIG.  11    illustrates the cassette  500 , with top insulator  504  removed. The top tray  520  and the bottom tray  560  provide a rigid structure that contains the battery cells  550 , as discussed further below. 
       FIGS.  12 A and  12 B  illustrate the components of the battery cassette  500  in greater detail. The top cell connection boards  510  are designed to nest within the top battery tray  520 . The battery cells  550  are square packed, leaving space for transverse fire barriers  530  and longitudinal fire barriers  540 . Cell spacing and FR4 fire isolators preferably isolate each battery cell  550  from its neighbors to prevent thermal propagation. The fire barriers  530  and  540  are cut from rigid fiber reinforced, fire resistant sheet preferably a fire retardant fiberglass board, for example 3M™ TuFR Hybrid Organic/Inorganic Paper board. The fire barriers  530  and  540  are preferably constructed from phase changing composite (PCC) materials to protect against thermal runaway. For example, a resin in the PCC sheeting comprising the fire barriers  530  and  540  may be selected to melt at temperatures present during a thermal runaway, causing fibers in the fire barriers  530  and  540  to expand and thermally insulate the malfunctioning battery cell from neighboring cells. Similarly, in preferred embodiments, phase changing materials (e.g., wax) are disposed in the container and used to absorb energy (e.g., heat from battery) via material phase change (e.g., solid to liquid). Alternative materials are also available for the fire barriers  530  and  540  and may provide a lighter weight structure. Alternative arrangements of the battery cells  550  and fire barriers  530  and  540  could also be employed, including triangular or hexagonal packing. In preferred embodiments, each battery cell  550  is wholly isolated from its neighboring cells. This reduces the chance that thermal runaway in a given battery cell  550  can propagate to neighboring cells. A preferred embodiment of the container was burn tested 3000° C. for 5 seconds, has been UL4 V0 rated, and has a maximum continuous service temperature of 140° C. 
     In addition to reducing the chance of thermal runaway, the fire barriers  530  and  540  provide a rigid structure that supports at least part of any load placed on a top surface  314  of the container  302 . The height of the fire barriers  530  and  540  fills the distance between the top tray  520  and bottom tray  560  The fire barriers  530  and  540  provide a stiff structure, and reduce the load placed on the battery cells  550 . Reducing the load on placed on the battery cells  550  aids to mitigate the degree of flexing between the battery cells  550  and printed circuit boards  580  and  585  to which the battery cells  550  are mounted. This reduces the stress experienced by a connection point (e.g., soldering) of the battery cells  550  to the printed circuit boards  580  and  585 , which could otherwise result in the battery cell  550  becoming disconnected from the circuit boards  580  or  585 . 
     Printed circuit boards  580  and  585  are located peripheral to the battery cells. The printed circuit boards  580  and  585  include battery management system circuitry, circuitry that provides active safety features, GPS, IMU, storage memory, and communication circuitry, as discussed above with respect to  FIG.  16   . Sensors for temperature, pressure, smoke, water, humidity, and inertial measurement may be provided on printed circuit boards  580  and  585 . In a preferred embodiment, high temperature sensing is used to disable the battery unit  302 . High temperature can indicate improper operating environment and/or malfunction of battery cells  550 . As discussed above, in preferred embodiments the container  302  is pressurized above atmospheric pressure. Pressure sensors in the container  302  are configured to detect a drop in pressure that might indicate a breach of the watertight container  302 . The battery unit  302  can be disabled until a trained technician inspects it. In some embodiments, a smoke sensor disposed within the container  302  can detect fire caused by thermal runaway, allowing the battery management system to disable the battery unit  302 . In a preferred embodiment, water and humidity detection are performed by using two wire leads and monitoring the resistance between the two wires. When the resistance drops due to humidity or water fouling, the system is designed to disable the battery. 
     GNSS and communication circuitry may also be provided on printed circuit boards  580  and  585 . Communication circuitry preferably includes a CAN-bus controller or transceiver for communicating with an electronic speed controller mounted in close proximity to the motor  310  of the watercraft  300 . Communication circuitry preferably also includes a transceiver for external communications, for transmitting data to a remote server via Wi-Fi, Bluetooth, or cellular data as would be known to an ordinarily skilled circuit designer. GNSS circuitry may also be provided on printed circuit boards  580  and  585 , for capturing the location of the container  302 . The GNSS circuitry may also be used to capture telemetry data of the watercraft, including location, speed, and heading. 
     Printed circuit boards  580  and  585  may also include safety features designed to protect the battery cells  550  from the harsh shorebreak environment. In preferred embodiments, all safety systems for the battery cells  550  are included in the container  302 , making it a modular device. A preferred embodiment includes a three-tiered fusing structure. Three types of fuses are provided, designed to provide synchronized action across three levels: individual cell-level (25 A), bank level (implemented as a 0 Ohm resistor), pack level (150 A). At the pack level, an analog short circuit detection device (not shown) is provided, having a 10 μs response time. The short circuit detection device is resettable and prevents permanent system-level damage. Individual cell-level fuses are capable of isolating a malfunctioning cell and enable use of the battery even if some cells fail. The printed circuit boards  580  and  585  include circuits for monitoring the status of each individual fuse and identifying fuses that have blown. Fuse blow timing characteristics across the fuse tiers are matched to the profile of failure to avoid premature triggering. 
     A solid-state switch, fuse or contactor (not shown) is preferably used to disconnect the main power pins of the connector when it is disconnected from the watercraft  300 . The solid-state switch may comprise high power MOSFETs for switching the power to the pins of the connector on and off. The battery management system may use one of several mechanisms for detecting that it is disconnected from the watercraft  300 . In one example, the fuse disconnects when communication signals are not present. Electrical characteristics, including inductance, resistance, or capacitance can be measured and used to detect disconnection. In a preferred embodiment, a capacitance associated with bulk capacitors located in the electronic speed controller is used to detect when the container  302  is either connected or disconnected from the watercraft  300 . Other mechanisms may also be used, including a pin interlock or proximity sensor relying upon a magnet or other means as would be known to a person having ordinary skill in the art. The power may also be disconnected from the power pins of the connector in response to detecting a short within the battery. In one example, the battery management system includes an analog short circuit detection circuitry that is configured to detect a short within the battery. Upon detecting a short, the battery management system, or the analog short circuit detection circuitry, may be configured to quickly switch the solid-state switch to disconnect the power to the power pins before the high current does damage to any electronics. 
       FIGS.  13 A and  13 B  illustrate a top tray  520 . In preferred embodiments, the top tray  520  and bottom tray  560  are identical, designed symmetrically to fit together and sandwich the battery cells  550  and fire barriers  530  and  540 . In alternative embodiments, the top tray  520  and bottom tray  560  differ slightly, but both the top tray  520  and the bottom tray  560  will include the features discussed below. Accordingly, the illustrations in  FIGS.  13 A and  13 B  apply to both the top tray  520  and bottom tray  560  even though only the top tray  520  is discussed.  FIG.  13 A  shows an outside surface of the tray  520 . Raised cylindrical projections  522  are placed between the battery cells  550 . The cylindrical projections are weight-bearing surfaces, designed to support, for example, the top housing portion  370  of the container  302 . In preferred embodiments, an insulator  504  is placed between the tray  520  and the top housing portion  370 . Weight applied to the top surface  314  of the container  302  is transmitted through the top housing portion  370  to the insulator  504 , and then through the raised cylindrical projections  522  and the perimeter top surface  521 . Top cell connection boards  510  are nested between the cylindrical projections  522 , such that the boards  510  and components mounted thereon are not subject to the weight applied to the container  302 . 
       FIG.  13 B  shows an inside surface of the tray  520 . Cylindrical pockets  524  are provided that are designed to receive a top or bottom end of each battery cell  550 . In a preferred embodiment, the battery cells  550  are standard 18650 lithium ion cells. Other similar cells may be used, or the container may be designed for non-standard cells. The tray  520  includes a substantially flat surface  525  designed to interface with the fire barriers  530  and  540  located between each battery cell. When assembled as part of battery cassette  500 , the substantially flat surface  525  transmits weight from the tray  520  to the fire barriers  530  and  540 , such that the fire barriers support weight placed on the top surface  314  of the container  302 . Posts  535  are received within the tray  520  and serve to align the top tray  520  and bottom tray  560  when joined together. The posts  535  also include slots to align and hold the fire barriers  530  and  540  together. Each post  535  includes a hole on the top end into which a fastener (e.g., a screw) may be inserted to join the top tray  520  to the post  535  and a hole on the bottom end into which a fastener (e.g., a screw) may be inserted to join the bottom tray  560  to the post  535 . The posts  535  thus attach the top tray  520  to the bottom tray  560 . 
       FIG.  14    shows the internal components of the battery cassette  500 , without the top insulator  504 , top cell connection boards  510 , and top tray  520 . The transverse fire barriers  530  each have series of slots  532 . Each slot  532  corresponds and mates with one of the longitudinal fire barriers  540 . The longitudinal fire barriers  540  each have a series of slots  542 . Each slot  542  corresponds and mates with one of the transverse fire barriers  530 . When assembled, the fire barriers  530  and  540  form a lattice with a pocket for each battery cell  550 . When assembled within the battery cassette  500 , the top edge of each fire barrier  530  and  540  is in close contact with an inside surface  525  of the top tray  520 . Likewise, the bottom edge of each fire barrier  530  and  540  is in close contact with an inside surface of the bottom tray  560 . Each battery cell  550  has an anode (positively charged) end  551  and a cathode (negatively charged) end  552 . Pockets  564  in the bottom tray  560  are designed to receive the respective anode end  551  and cathode end  552  of the battery cells  550 . A fuse  572  is provided for each battery cell  550  to individually protect each battery cell  550 . 
       FIG.  15    illustrates the top battery tray, showing the top cell connection boards  510  nested among the circular projections  522 . A nickel tab  512  is mounted on each of the top cell connection boards  510 , at the interface between each battery cell  550  and its respective top cell connection board  510 . A fuse  513  is mounted on the top connection boards  510  adjacent to and corresponding to each of the nickel tab  512  for each cell  550 . The fuse configuration illustrated in  FIG.  15    for top cell connection boards  510  is duplicated for the bottom cell connection boards  570 . As illustrated, the preferred embodiment includes eight separate top cell connection boards  510 A- 510 H. Boards  510 A,  510 D,  510 E, and  510 H each support  16  battery cells  550 . Boards  510 B,  510 C,  510 F, and  510 G each support  32  battery cells  550 . The cells are organized into modules of battery cells  550  for management and higher-level fuse protection. 
     With reference now to  FIGS.  17 A-D , the images show container  302  being removed according to an embodiment. As shown, the container  302  includes a cavity  316  for housing the battery cassette  550  as described above. The socket  100  is attached at an end  322  of the container  302 , with the socket  100  facing downward or away from the upper surface  314  of the container  302 . In  FIG.  17 A , the plug  200  of the watercraft  300  is shown fully inserted into the socket  100 . To remove the socket  100  from the plug  200 , the end  322  of the container  302  may be moved in the upward direction, away from the plug  200  and out of the cavity  312  of the watercraft  300 . With reference to  FIGS.  17 B-D  the end  322  of the container  302  having the socket  100  is shown progressively moving away from the plug  200 . The container  302  is shown pivoting about an end  324  of the container opposite the socket  100 , until the socket  100  is no longer in contact with the plug  200  as shown in  FIG.  17 D . The container  302  may then be removed from the cavity  312  of the watercraft  300 . 
     To insert the container  302  into the cavity  312  of the watercraft  300  and connect the plug  200  of the watercraft  300  to the socket  100  of the container  302 , the steps for removing the container  302  may be reversed. With reference to  FIG.  17 D , the end  324  of the container  302  opposite the socket  100  may be positioned within the cavity  312 . The end  324  may be brought near or into contact with the end  326  of the cavity  312  opposite the plug  200 . Then, as shown progressively from  FIG.  17 C  to  FIG.  17 A , the socket end  322  of the container is pivoted about the end  324  opposite the socket  100  to bring the socket  100  into contact with the plug  200  of the watercraft  300 . As the socket  100  contacts the plug  200 , the plug  200  may pivot slightly to align with the socket  100 . The pins of the plug  200  may also pivot or move slightly to align with the pin connectors  142  of the socket  100 . The end  322  of the container  302  may be forced downward and into the cavity  312  until the plug  200  is fully received within the socket  100 . This may occur when the upper surface  314  of the container  302  is horizontal and/or substantially coplanar with the deck  306  of the watercraft  300 . 
     As shown in  FIGS.  17 A-D , the container  302  includes a handle  330  attached to the end  322  of the container  302  including the socket  100 . The handle  330  may be used to pivot the container  302  about the end  324  opposite the socket  100  to connect and disconnect the socket  100  from the plug  200 . The handle  330  may provide additional leverage to the user in inserting or extracting the container  302  from the cavity  312  of the watercraft  300 . 
     In some embodiments, the deck  306  of the watercraft  300  may include a tongue  320  that extends over the upper surface of the cavity  312 . The end  324  of the container opposite the socket  100  may extend underneath the tongue  320  when fully inserted into the cavity  312 . During insertion, when the end  324  of the container is positioned within the cavity, a portion of the upper surface  314  at end  324  of the container  302  may be brought into contact with the tongue  320 . For example, an installer may slide the container  302  along the cavity  312  until the upper surface  314  contacts the tongue  320 . As the end  322  of the container  302  including the socket  100  is pivoted toward the plug  200  and into the cavity  312 , the container  302  may pivot about the point of contact between the container  302  and the tongue  320 . As the end  322  of the container  302  nears the plug  200 , the bottom surface of the container  302  may slide or translate along the bottom of the cavity  312  in the direction opposite the plug  200 . Once the socket  100  contacts or engages the plug  200 , the container  302  no longer slides or translates, but rotates about the point of contact between the container  302  and the bottom surface of the cavity  312  until the plug  200  is fully inserted into the socket  100 . This design, where the translation of the container  302  occurs before the socket  100  engages the plug  200 , reduces the amount of stress and strain applied to the plug  200  in connecting the socket  100  to the plug  200 . Since the container  302  is substantially only rotating about the point of contact of the container  302  and the bottom surface when the plug  200  and the socket  100  interconnect, the plug  200  only needs to pivot slightly to align with the socket  100 . Further, the lateral forces on the plug  200  are minimized because, at the point where the plug  200  contacts the socket  100 , the container  302  lacks freedom to translate within the cavity  312 . This may reduce the risk of damage to the plug  200  during insertion and removal of the container  302 . 
     The distance between the tongue  320  and the bottom of the cavity  312  may be the same or slightly smaller than the height of the container  302 . Thus, when the container  302  is positioned within the cavity  312  with a portion of the container  302  between the tongue  320  and the bottom surface of the cavity  312 , the end  324  of the container  302  is held firmly in place by watercraft  300 , being slightly compressed by the tongue  320  and the bottom of the cavity  312 . The resilient isolation strips  387  described above may compress as the container  302  locks into place within the cavity. The isolation strips  387  advantageously reduce the need for tight tolerances when forming the cavity  312  within the board  305 . 
     In yet another embodiment, shown in  FIGS.  18 A-D  and  119 A-D, the handle  330  is rotatably attached to the container  302 . The handle  330  includes a gripping portion  332  having two ends, each end attached to an arm  334 . The arm  334  extends from the gripping portion  332  to the attachment point  336  at the end of the arm  334  opposite the gripping portion  332 . The arm  334  is rotatably attached to the container  302  by the bar  337  (illustrated in  FIGS.  5  and  6   ), allowing the gripping portion  332  of the handle  330  to rotate about the attachment point  336 . Each arm  334  further includes a slot  338  for receiving pins  340  affixed to the upper end  309  of the strut  308  of the watercraft  300 . As shown the pins  340  extend from the attachment structure  342  at the upper end  309  of the strut  308  to which the plug  200  is attached. In other embodiments, the pins  340  may protrude from a surface of the cavity  312  or the plug  200 . Each slot  338  includes a mouth  344  for receiving the pin  340 . The slots  338  include a lower cam surface  346  and an upper cam surface  348  that the pins  340  engage as the pins  340  move along the slot  338 . The lower cam surface  346  includes an inner detent  350  and an outer detent  352  for receiving the pin  340 . When the pin  340  is within a detent  350 ,  352  the pin  340 , the handle  330  does not move substantially relative to the pin  340  without the application of force on the handle  330 . 
     In operation, when inserting the container  302 , the end  324  of the container  302  opposite the socket  100  is positioned within the cavity  312  of the watercraft  300 , for example as described above in regard to  FIGS.  17 A-D . As the socket  100  of the container  302  is pivoted towards the plug  200 , the handle  330  is in an upward position, causing the mouths  344  of the slots  338  to be near pins  340 . The handle  330  may be rotated downward, causing the pins  340  to enter the slots  338  via the mouths  344 , for example, as shown in  FIG.  18 B . An installer may rotate the handle  330  by moving the gripping portion  332  about the attachment point  336 . The pins  340  may slide along the lower cam surface  346  of the slot  338  during insertion. The handle  330  is further rotated about the attachment point  336 , causing the lower cam surface  346  of the handle  332  to apply a force to the pin  340  and move the plug  200  further into the slot  100 . As the pin  340  is moved along the lower cam surface  346  by rotation of the handle  330 , the pin  340  enters the outer detent  352 , as shown in  FIG.  18 C . To move the pin  340  beyond the outer detent  350  may require increased force to cause the plug  200  to be fully inserted into the socket  100  of the container  302 . Providing the outer detent  352  along the slot  338  provides tactile feedback to the installer, providing the opportunity to ensure that the plug  200  is properly aligned with the socket  100  before fully inserting the plug  200  into the socket  100 . With this tactile feedback, the installer may be able to determine whether the plug  200  is properly entering the socket  100  or whether debris is interfering or whether the connectors are misaligned. To fully insert the plug  200  into the socket  100 , an additional downward force must be applied to the gripping portion  332  of the handle  330  to cause the pin  340  to move from the outer detent  352  to the inner detent  350  of the slot  338  as shown in  FIG.  18 D . Once the pin  340  is resting in the inner detent  350  of the slot  338 , the plug  200  is fully inserted within the socket  100 . The gripping portion  332  and a top surface of the arms  334  may be substantially horizontal and even co-planar with the deck  306  of the watercraft  300 . Resilient components within the connector (e.g., socket boots and plug boots and the air compressed within the sealed space) provide a force that would drive the plug  200  apart from the connector  100 , but for the pin  340  engaged in the slots  338 . This upward force tends to keep the pin  340  within the detent  350  and prevents the handle  330  from rotating upward. Thus, providing an inner detent  350  at the point of where the plug  200  is fully inserted into the socket  100  requires additional force to be applied to the handle to remove the socket  100  from the plug  200 , and otherwise retains the handle  330  at the fully inserted position. 
     With reference to  FIGS.  19 A-D , when removing the container  302  from the watercraft  300 , the gripping portion  332  of the handle  330  is rotated upward. This causes the upper cam surface  348  of the slot  338  to engage the pin  340 . The upper cam surface  348  applies a force to the pin  340  to force the socket  100  upward and away from the plug  200 . The upper cam surface  348  of the slot  338  may be a smooth curved surface with no detents. This allows the handle  332  to be smoothly moved from the position where the plug  200  is fully inserted into the socket  100  to the position where the plug  200  is removed from the socket  100  with an approximately constant force. Once the pin  340  is no longer within the slot  338  of the handle  330 , the handle  330  may be used to pull the end  322  of the container  302  upward and away from the plug  200 . Once the plug  200  is fully removed from the socket  100 , the container  302  may be pivoted, slid, and removed from the container, for example, as described in regard to the embodiment of  FIG.  17 A-D . 
     Uses of singular terms such as “a,” “an,” are intended to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms. It is intended that the phrase “at least one of” as used herein be interpreted in the disjunctive sense. For example, the phrase “at least one of A and B” is intended to encompass A, B, or both A and B. 
     While there have been illustrated and described particular embodiments of the present invention, those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the scope of the invention, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept.