Patent Publication Number: US-2021184290-A1

Title: Battery pack for aerial vehicle

Description:
RELATED APPLICATION DATA 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/948,190 filed on Dec. 13, 2019 and U.S. Provisional Patent Application No. 62/706,611 filed on Aug. 28, 2020, the contents of which are hereby incorporated by reference in their entireties. 
    
    
     BACKGROUND 
     With the increased interest in electrically powered aerial vehicles, such as electric vertical takeoff and landing (eVTOL) aerial vehicles (AVs), a number of technical challenges have arisen with respect to the construction of battery packs for these aerial vehicles. For example, it is desirable to minimize the weight of battery packs in order to increase the range of electrically powered aerial vehicles. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. 
         FIG. 1  illustrates a battery pack in accordance with one example. 
         FIG. 2  illustrates aspects of the battery pack in accordance with one example. 
         FIG. 3  illustrates aspects of battery pack in accordance with one example. 
         FIG. 4  illustrates a cassette spine in accordance with one example. 
         FIG. 5  illustrates a battery cassette in accordance with one example. 
         FIG. 6  illustrates a battery cell interconnect arrangement in accordance with one example. 
         FIG. 7  illustrates aspects of a battery pack in accordance with one example. 
         FIG. 8  illustrates aspects of a battery pack in accordance with one example. 
         FIG. 9  illustrates a heat pipe configuration in accordance with one example. 
         FIG. 10  illustrates a battery pack temperature graph in accordance with one example. 
         FIG. 11A  illustrates a support structure in accordance with one example. 
         FIG. 11B  illustrates a support structure in accordance with one example. 
         FIG. 12  illustrates a cut away perspective view of a foot mounted to a bottom cover in accordance with one example. 
         FIG. 13  illustrates a bottom cover for a battery pack in accordance with one example. 
         FIG. 14  illustrates the bottom cover of  FIG. 13  in more detail. 
         FIG. 15  illustrates a perspective view of a foot mounted to a bottom cover in accordance with another example. 
         FIG. 16  illustrates exploded perspective views of a cassette spine in accordance with one example. 
         FIG. 17  illustrates an exploded perspective view of a battery cassette in accordance with one example. 
         FIG. 18  is a perspective view illustrating the electrical interconnections between battery groups in three adjacent battery cassettes in accordance with one example. 
         FIG. 19  illustrates an exploded perspective view of a plurality of battery cassettes showing how they are arranged to form a cassette stack accordance with one example. 
         FIG. 20A  is a perspective view of a top cell interconnect in one example. 
         FIG. 20B  is a partial perspective view of a cell monitoring module in accordance with one example. 
         FIG. 21  illustrates an exploded view of a battery pack in accordance with another example. 
         FIG. 22  illustrates a perspective view of a battery pack in accordance with one example. 
         FIG. 23  illustrates a vertical and longitudinal cross section through a battery pack in accordance with one example. 
         FIG. 24  illustrates a perspective view of a one-piece cassette chassis in accordance with one example. 
         FIG. 25  illustrates a perspective view of the one-piece cassette chassis of  FIG. 24 , partially filled with preassembled cell groups. 
         FIG. 26  illustrates an exploded perspective view of the cell group shown in  FIG. 25  in accordance with one example. 
         FIG. 27  is a perspective view illustrating the electrical interconnections between adjacent battery cell groups in accordance with one example. 
         FIG. 28  illustrates a battery temperature graph in accordance with one example. 
         FIG. 29  illustrates a battery pack in accordance with another example. 
         FIG. 30  illustrates a battery submodule in accordance with one example. 
         FIG. 31  illustrates a battery pack in accordance with an example. 
         FIG. 32  illustrates a perspective view of a spray cooler in accordance with one example. 
         FIG. 33  illustrates a perspective view of a cold plate in accordance with one example. 
         FIG. 34  illustrates a flowchart describing cooling of a battery pack in accordance with one example. 
         FIG. 35  illustrates an avionics system  3500  for an aerial vehicle  3600 , in accordance with some examples. 
         FIG. 36  is a diagrammatic representation of an autonomous aerial vehicle  3600 , in accordance with some examples. 
     
    
    
     DETAILED DESCRIPTION 
     According to some examples, there is provided a battery pack for an electrically powered aerial vehicle (AV) (e.g., a vertical takeoff and landing (VTOL) AV) having a fuselage, and a number of electric motors that power rotors of the AV, the electric motors being coupled to the battery pack. The battery pack, in turn, includes a cassette stack that includes a number of battery cell cassettes and a housing to receive and accommodate the cassette stacks. 
     Each battery cell cassette includes a collection of cylindrical battery cells secured by support structures, which are thermally attached to the housing so as to operationally provide a heat path from the battery cells to a surface of the housing. Operationally, the surface of the housing may be exposed to airflow during the flight of the aerial vehicle, and also to ground-based cooling systems when the aerial vehicle is docked at a base station. 
     The support structures and housing, in addition to providing the heat paths, may also provide electrical paths between battery cells in the battery cell cassette. 
     The support structures orient the cylindrical battery cells in an axially stacked configuration so that vents of the battery cells do not point towards each other, but instead point away from each other in diametrically opposite directions. 
     More specifically, in one example, disclosed is a support structure for a battery pack, comprising an electrically and thermally conductive frame to receive at least one battery cell having a first terminal and a second terminal, and a heat pipe. The first terminal is electrically coupled to the frame when the at least one battery cell is mounted in the frame. The heat pipe provides thermal conductivity between the frame and a cooling surface. 
     The frame may receive at least first and second battery cells in an axially stacked configuration with a vent of the at least first battery cell facing in an opposite direction to a vent of the at least second battery cell. The support structure may further comprise a first electrically-conductive structure to electrically couple the frame to a terminal of at least one battery cell in an adjacent frame, as well as a second electrically conductive structure to electrically couple the second terminal to an adjacent frame. The support structure may further comprise an electrically conductive structure to electrically couple the second terminal to an adjacent frame. 
     The support structure may also include least one foot to thermally couple the heat pipe to the cooling surface, the foot being electrically insulated from the cooling surface. Additionally, the frame may comprise at least a first cross member and a second cross member to receive the at least one battery cell, and at least one vertical member to connect the first and second cross members. The heat pipe, comprising a metal rod, may be located within the vertical member. 
     The support structure may further comprise at least one bridge to couple the frame to at least one other frame, the support structures being couplable one to another via the bridge. The at least one bridge may comprise a chassis. The support structure in use may be coupled to the at least one bridge via the at least one battery cell. The at least one bridge may also comprise a plurality of bridges to couple adjacent support structures one to another to form a battery cassette. The at least one bridge may be configured to couple adjacent support structures to each other so that the adjacent support structures face in opposite directions in a battery cassette. 
     The support structure may further comprise a first electrically-conductive structure to electrically couple the frame to a terminal of at least one battery cell in a first adjacent battery cassette, and a second electrically conductive structure to electrically couple the second terminal to an adjacent frame in a second adjacent battery cassette. The support structure may further comprise an electrically conductive structure to electrically couple the second terminal to an adjacent frame in an adjacent battery cassette. 
     Also disclosed is a battery pack including a cassette stack comprising a plurality of battery cell cassettes, each of the cassettes including a plurality of support structures. Each support structure comprises an electrically and thermally conductive frame for receiving at least one battery cell having a first terminal and a second terminal, and a heat pipe. The first terminal is electrically coupled to the frame when the at least one battery cell is mounted in the frame. The heat pipe provides thermal conductivity between the frame and a cooling surface. 
     The frame may receive at least first and second battery cells in an axially stacked configuration with a vent of the at least first battery cell facing in an opposite direction to a vent of the at least second battery cell. The support structure may include a first electrically-conductive structure to electrically couple the frame to a terminal of at least one battery cell in an adjacent frame, and a second electrically conductive structure to electrically couple the second terminal to an adjacent frame. The adjacent frame may be in an adjacent cassette. 
     Further, a method of cooling an electric vehicle including a battery pack comprises aligning the battery pack and a cooling structure, moving the cooling structure into contact with the electric vehicle, and circulating coolant through the cooling structure. 
     The cooling structure may comprise a trough having spray heads and the circulating of the coolant may include spraying the coolant against a surface of the battery pack or the electric vehicle. The trough may include a resilient seal along an upper perimeter of the trough. 
     The cooling structure may comprise a block having channels defined therein through which the coolant circulates, and the cooling structure may include a resilient pad that contacts the electric vehicle. 
     Additionally, a battery pack includes a cassette stack having multiple battery cell cassettes, each of the cassettes including a battery cassette spine to secure respective first and second pluralities of battery cells. A first plurality of battery cells is secured in a first orientation such that vents of each of the first plurality of battery cells are oriented in a first direction away from the second plurality of battery cells. A second plurality of battery cells is secured in a second orientation such that that vents of each of the second plurality of battery cells are oriented in a second direction away from the first plurality of battery cells. A housing receives the cassette stack, the housing including a first housing panel thermally coupled to the cassette stack, and to electrically insulate electrical paths between battery cells of the cassette stack. 
       FIG. 1  provides perspective views of a battery pack  100 , according to some examples, the battery pack  100  forming part of a collection of battery packs  100  accommodated within a fuselage  108  of an aerial vehicle  3600 . In the example provided in  FIG. 1 , five battery packs  100  are mounted under the fuselage  108 . Ducted airflows are provided, within the aerial vehicle  3600 , above the collection of battery packs  100 , while free airflow operationally provides cooling below the collection of battery packs  100  during flight of the aerial vehicle  3600 . Specifically, a battery cavity is provided within the fuselage  108  into which five battery packs  100  can be removably inserted and secured, with bottom covers of the battery packs  100  being exposed directly to airflow. 
     Each battery pack  100 , according to one example, comprises a cassette stack  102  (including battery cell cassettes) and a battery management system (BMS) module  104 , accommodated within a housing having top and bottom covers, a pair of end structures  106 , and a pair of cross structures  110 . The end structures  106  provide mechanical connections and live electrical connections on the short side of the battery pack  100 . 
     As will be described with reference to the drawings, the battery cell cassettes of the battery pack  100  include two layers of cylindrical battery cells which are stacked axially within the battery pack  100 , and that are secured within the battery pack  100  by support structures that conduct thermal energy from the battery cells to the top and bottom covers of the housing of the battery pack  100 . 
       FIG. 2  is a perspective view of a battery pack  100 , according to some examples, and shows further details regarding its structure. 
     Within the battery pack  100 , two layers of battery cells are stacked axially, with vents of battery cells of each layer pointing away from the other layer. 
       FIG. 3  is an exploded view of a battery pack  100 , which illustrates further details of an example structure. The battery pack  100  comprises a cassette stack  102 , which is contained within a housing. The cassette stack  102  is constructed of  25  battery cassettes  304 , each of which in turn includes  80  cylindrical battery cells secured within a collection of interconnected support structures  402 . 
     The housing includes a top cover  302 , a pair of end structures  106 , a pair of cross structures  110 , and a bottom cover  202 . These components are connected and welded together (or otherwise sealed together) to create an environmental seal around the cassette stack  102 . Each of the cross structures  110  attaches to the cassette stack  102 , and provides a load path to the pair of end structures  106 . 
     The end structures  106  are attached to the cross structures  110 , and provide a load path to mounts within the battery cavity of an aerial vehicle  3600 . 
     The bottom cover  202  has a series of longitudinally extending electrical insulators  306  defined on an inside surface thereof. The electrical insulators  306  provide electrically insulated thermal paths from the support structures  402 , and specifically heat pipes  406  that form part of the support structures  402  in each battery cassette  304 , to the bottom cover  202 . 
     The bottom cover  202  may be used to support from both active and passive heat extraction from the battery pack  100 . Specifically, the bottom cover  202  may be exposed as an outer surface of an aerial vehicle, and thus subject to high velocity airflow during flight of an aerial vehicle. This high velocity airflow is effective in passively extracting heat from the battery pack  100 . When the aerial vehicle is landed and docked, an active cooling system may furthermore thermally engage the bottom cover  202 , so as to actively extract thermal energy from the battery pack  100 . 
     The two layers of battery cells are secured within the battery pack  100  using multiple support structures  402  as shown in  FIG. 4 , which are connected in a series to form a cassette spine  400 . The support structures  402  are thermally connected to the battery cells, and conduct heat passively from the battery cells to the bottom cover  202  of the battery pack  100 . In alternative examples, the support structures  402  may also be thermally connected to other surfaces of the battery pack  100 , so as to channel thermal energy to these surfaces. In the example, lower ends of the support structures  402  are welded (or otherwise thermally connected) to the thermally conductive electrical insulators  306  that create a favorable thermal connection between battery cells and the bottom cover  202 , and that also electrically isolate battery cells that would otherwise cause a short circuit (e.g., between an adjacent group of ten battery cells in a battery cassette  304 ). 
       FIG. 4  provides exploded perspective views of a cassette spine  400 , according to some examples, which is constructed from a series of connected or bridged support structures  402 . Each support structure  402  includes a frame that has four cross members  408  supported by a pair of vertical members  410 . Each cross member  408  in turn includes three recesses on one side to accommodate a group of three cell batteries, and two recesses on the other side to accommodate a group of two cell batteries. In an example, a single support structure  402  is able to accommodate and hold ten cylindrical battery cells, five at the bottom and five at the top. The recesses are, as shown in  FIG. 4  are, semicircular in shape to accommodate cylindrical battery cells. 
     The arrangement of support structures  402  when assembled to form cassette spines  400  provides a cassette-based architecture for the battery pack  100 , with a series of support structures  402  each accommodating ten cylindrical battery cells and being connected in series to form cassette-based subassemblies (e.g. a battery cassette  304 ). 
     The support structure  402  is constructed of a material that is both a good thermal and electrical conductor, (e.g. aluminum or some other metal). 
     As will be described in further detail with respect to a subsequent figure, all five cells in an upper or lower group of five battery cells in the ten cylindrical battery cells that are mounted to a single support structure  402  are connected in parallel, so that the fives cells are all at the same electrical potential. This allows a group of ten mounted battery cells to be conveniently connected as discussed in more detail below. 
     Each vertical member  410  has a foot  412  to facilitate thermal and electrical coupling to an electrical insulator  306 . Each vertical member  410  also includes a longitudinally extending hollow chamber, into which is soldered a heat pipe  406 . In one example, the heat pipe  406  is a metal tube made out of copper and is bent at the bottom so as to be snugly accommodated within a foot  412  of a vertical member  410 , and to provide solid thermal coupling to a heat sink (e.g., an electrical insulator  306  thermally coupled to a bottom cover  202 ). The heat pipes  406  are conventional in nature and include an appropriate working fluid, (e.g. water) and internal wicking structure. Depending on the required heat flux and temperature range, heat pipes of various enclosure materials (i.e. aluminum, steel, titanium, copper, etc.) and working fluids (i.e. acetone, methanol, water, etc.) could be used. In another example, the hollow chamber in each of the vertical members  410  may be partially filled with water or another working fluid in order to partially establish a heat pipe. 
     In order to construct the cassette spine  400 , multiple support structures  402  are connected to each other using bridges  404 , which have respective tongues and grooves defined on opposite surfaces thereof to engage with corresponding tongues and grooves defined on a cross member  408  of a support structure  402 . As illustrated, the bridges  404  are bonded into the support structures  402  in order to physically couple, but electrically insulate, support structures  402  from each other. In order to provide electrical insulation, a bridge  404  is made of an electrically insulating material, such as an injection molded plastic. A series of eight support structures  402  may be connected in an alternating orientations to form the cassette spine  400 . Adjacent groups of ten cylindrical battery cells, mounted on respective support structures  402 , will operationally be at different electrical potentials, with the bridges  404  serving to electrically insulate these mounted battery cells and their support structures  402  from each other in order to prevent shorting. Each the group of ten cylindrical battery cells thereby constitutes a building element of a cassette stack  102 , with a dedicated thermal path from each group of battery cells to the bottom cover  202  or top cover  302  via an electrical insulator. 
     While further details will be provided below regarding the mounting of cylindrical battery cells to the support structure  402 , it should be noted that a first set of five battery cells are mounted to the top half of the support structure  402  in a first alignment. In this first alignment, the respective vents of each of these five battery cells are located at an upper end of the support structure  402 , so that the vents would discharge in an upward direction and away from a second set of five battery cells that are mounted to the bottom of the support structure  402 . Similarly, the second set of five battery cells are mounted to the bottom half of the support structure  402  in a second alignment with the respective vents of each of these five battery cells being located at a lower end of the support structure  402 , so that the vents would discharge in a downward direction and away from the first set of five battery cells. 
     A support structure  402 , incorporating a pair of heat pipes  406 , is effective to maintain an operational temperature difference between the first set of battery cells, mounted on the top half of the support structure  402 , and the second set of battery cells, mounted on the bottom half of the support structure  402  and closest to a heatsink, within a specific tolerance. Accordingly, the described arrangement is effective in addressing a geometric disadvantage of a top-mounted battery cell being further away from a heatsink. 
       FIG. 5  provides exploded perspective views of a battery cassette  500  and specifically how are various components are assembled into a cassette spine  400  shown in  FIG. 4   
     A first battery cell group  502 , with each of an upper pair and a lower pair of battery cells being vertically stacked in an opposing orientation, are attached to a first side of a support structure  402 . A second battery cell group  504 , with each of an upper three and a low three battery cells being vertically stacked in opposing directions, are attached to a second side of the support structure  402 . Specifically, each of the battery cell group  502  and battery cell group  504  are bonded to a respective support structure  402  by a thermally conductive epoxy, so as to thermally couple the battery cells to the support structure  402  so that the support structure  402  can operationally conduct thermal energy to a heatsink. 
     A top cell interconnect  506  is welded to the top ends (positive) of the upper five cylindrical battery cells, and also to the lower ends (also positive) of the lower five cylindrical battery cells. Similarly, a bottom cell interconnect  508  is welded to the negative ends of each of the battery cell group  502  and battery cell group  504 . Each bottom cell interconnect  508  has a pair of wings  510  that depend therefrom along the side of the battery cell group  504  and which, when the relevant set of three battery cells is inserted into a support structure  402 , are in electrical contact (e.g., through an electrically conductive weld) with the support structure  402 . Accordingly, each support structure  402  is electrically coupled to the negative terminals of a group of ten battery cells that are mounted to the support structure  402 , which effectively becomes a negative terminal for all of the ten cells mounted thereto. 
     Each top cell interconnect  506  and bottom cell interconnect  508  is constructed from aluminum and stamped to create a laminated bus between the respective positive or negative ends of a group of cells, upon assembly into the cassette spine  400 . 
     Further a gap filler  512 , comprising a plastic injection molded part, is inserted around and along the portion of each battery cell group  502 ,  504  adjacent to the positive ends of the cells of the battery group. The cell vents are located at the positive ends of the cells, so that if a cell vents then the gap filler prevents vent gas from flowing back into the cell matrix (e.g. in the direction of the negative terminals). 
       FIG. 6  is a perspective diagram, illustrating further details regarding the cell interconnects, such as the top cell interconnect  506  and bottom cell interconnect  508 , in a battery cell interconnect arrangement  600 .  FIG. 6  more clearly illustrates how a planar section of a bottom cell interconnect  508  is welded to the bottom (negative) ends of each  2  cell battery cell group  502  and the wings  510  of each bottom cell interconnect  508  are welded to a support structure  402  at location  602 . It will be appreciated that, upon assembly, the top cell interconnect  506  and bottom cell interconnect  508  form part of the support structure  402  regardless of whether or not they are first attached to a battery terminal before being attached to the support structure  402 . 
     Also shown is how a top cell interconnect  506  is welded to the top (positive) ends of a group of five upper (or lower) mounted battery cells, and to the foot of a neighboring support structure  402  at location  604 . In this way, the positive terminals of a group of five mounted battery cells are electrically coupled in parallel to a negative terminal, in the form of the support structure  402  itself, of a neighboring cell group. 
     Similarly, although not shown in  FIG. 6 , the positive terminals of a group of five upper-mounted battery cells is coupled in series with a negative terminal (e.g., the support structure  402  itself) of a neighboring cell group. Accordingly, the top cell interconnect  506  facilitates connections between neighboring cell groups. 
     Known cell arrangements typically provide exposure of both the positive and negative terminals of any cluster or group of batteries, so as to allow interconnection between terminals of respective clusters. The current example is advantageous in that it avoids a constraint of having both the negative and positive terminals of every cluster being exposed, by electrically coupling the negative terminals to a supporting support structure  402 , and extending the positive terminals of a first and second clusters or groups of cylindrical cells from one side of an assembly and into contact with the support structure  402  of a neighboring assembly. 
       FIG. 7  is a perspective illustration of a battery pack  100 , according to example, and illustrates a connection sequence between adjacent assemblies, with the arrow lines indicating a direction of series connection between the assemblies. As can be seen, current flows from a negative terminal  702  of the battery pack  100  from left to right (in the figure), from one battery cassette  304  to the next until it reaches the rightmost battery cassette  304 . An electrical interconnect then passes the current down (in the figure) to the next group of cells in the rightmost battery cassette  304 . 
     The current then flows in the opposite direction in the same manner as before, and this process repeats with the current passing back and forth and downward (in the figure) until the current reaches the positive terminal  704 . 
       FIG. 8  is a perspective diagram of a battery pack  100 , specifically illustrating free airflow  802  under the bottom cover  202  of the battery pack  100 , or under a fuselage with which the bottom cover  202  of the battery pack  100  is in thermal contact. Also, when an aerial vehicle is docked at a base (e.g., Skyport), a conductive cooling pad or other active cooling mechanism may be brought into thermal contact with the bottom cover  202  of the battery pack  100  in order to extract thermal energy. 
     In a further example, ducted airflow  804  may also be provided, within the fuselage of an aerial vehicle, over the top of the battery pack  100  in order to provide further cooling. 
       FIG. 9  is a perspective diagram, showing further details of a heat pipe configuration  900 . In particular,  FIG. 9  shows the thermal coupling between a support structure  402 , including heat pipes  406 , and a strip of electrical insulator  306  that is thermally conductive and coupled to a bottom cover  202  of a battery pack  100 . The support structure  402  is shown to provide a thermal path from a battery cell  902  via a pair of heat pipes  406 . Each heat pipe  406 , which is soldered into the support structure  402 , has a bent (or L-shaped) foot, as described above, which is coupled, using a thermal interface  904  (e.g., epoxy, gap pad etc.) to the electrical insulator  306 , which in turn is thermally coupled to the bottom cover  202  of the battery pack  100 . The bottom cover  202  accordingly acts as a heat sink with thermal energy traveling on the thermal path from the battery cell  902 , via the heat pipes  406 , and through the electrical insulator  306 . Each electrical insulator  306  may be constructed using a ceramic foil or a polymer which is thermally conductive, but electrically insulative so as to prevent shorting between support structures  402 , as these are at potential. 
       FIG. 10  shows a temperature graph  1000 , illustrating the effect of passive cooling as a result of airflow over a heat sink (e.g., bottom cover  202 ), described above, and active cooling, described below, through various operational states of the aerial vehicle  3600 . 
     As can be seen from the temperature graph  1000 , the battery pack  100  may for example be at a temperature of 55 deg C. at takeoff. During vertical takeoff, the temperature of the battery pack  100  may rise by for example 3 deg due to the relative lack of free airflow  802  and ducted airflow  804  over the battery pack  100  during takeoff. Once takeoff is complete, the aerial vehicle  3600  transitions to horizontal flight and the temperature of the battery pack  100  decreases by for example 7 deg as a result of passive cooling due to free airflow  802  and ducted airflow  804 . When the flight is complete, the aerial vehicle  3600  transitions to vertical flight for landing and the temperature of the battery pack  100  may rise by for example 6 deg due to the relative lack of free airflow  802  and ducted airflow  804  over the battery pack  100  during landing. After landing, the battery pack  100  may be actively cooled and charged, to return the battery pack  100  to an appropriate temperature and state of charge in preparation for the next flight. 
       FIG. 11A  and  FIG. 11B  illustrate two alternative examples of a support structure. 
     As shown in  FIG. 11A , provided is a separate foot  1102 , which is an aluminum extrusion that defines two downwardly facing channels  1104  that are sized to receive the lower ends of the heat pipes  406 . The heat pipes  406  are bonded into the support structure  1106  and the foot  1102  with thermally conductive epoxy. 
     It can also be seen that the frame of support structure  1106  of  FIG. 11A  has three cross members  1108  supported by four vertical members  410 . The support structure  1106  includes three semicircular recesses on one side to accommodate a group of three cell batteries, and two recesses on the other side to accommodate a group of two cell batteries. In an example, a single support structure  1106  is able to accommodate and hold ten cylindrical battery cells, five at the bottom and five at the top, as before. Each support structure  1106  is constructed of a material that is both a good thermal and electrical conductor, (e.g. aluminum or some other metal). 
     As shown in  FIG. 11B , also provided is an alternative example of a support structure  1116  with a separate foot  1112  made of extruded aluminum, which has two upwardly facing slots  1114  defined therein that are sized to receive the lower ends of the heat pipes  406 . The heat pipes  406  are bonded into support structure  1106  and the foot  1112  with thermally conductive epoxy. The foot  1112  may be anodized with type III anodization so that the heat pipes  406  are electrically insulated from the surface (e.g. bottom cover  202 ) to which the foot is mounted. The frame of support structure  1116  shown in  FIG. 11B  is a machined aluminum extrusion, in which mass has been reduced by eliminating two of the vertical members  1110  and the central cross member  1108  of the frame of support structure  1106  of  FIG. 11A . 
     While the support structure illustrated in  FIG. 11A  and  FIG. 11B  are shown as comprising three separate parts that are assembled together, it will be appreciated that the support structure may be formed as a single unitary item or one or more parts of the support structure may be combined into a single unitary structure. 
       FIG. 12  is a cut away perspective view of a foot  1102  mounted to a bottom cover  1202  in accordance with one example. In this example, the bottom cover  1202  is a solid titanium plate. There is a Kapton insulation layer  1204  located between the bottom cover  1202  and the foot  1102 , which serves to electrically insulate the foot  1102  (and thus the support structure  1106 ) from the bottom cover  1202 . A layer of thermal insulation  1206  is provided above the Kapton insulation layer  1204  and around each foot  1102 . A layer of thermal insulation  1208  is provided over each foot as shown. The thermal insulation  1206  and the thermal insulation  1208  direct heat away from the cassette stack  102  and to the exterior of the battery pack  100 .  FIG. 12  shows the various layers cut away for clarity. It will be appreciated that the various layers extend to provide appropriate coverage in each case. 
       FIG. 13  illustrates a bottom cover  1302  in accordance with one example. As shown in the figure, the bottom cover  1302  may be formed as an electrically insulating baseplate  1304  having thermally conductive pucks  1306  embedded therein. The pucks  1306  are exposed to the exterior and provide a conductive path to the outside for the heat generated by the cassette stack  102 . The mounting of a foot  1102  to a puck  1306  and the arrangement of insulation layers is the same as is shown and described with reference to  FIG. 12 . 
     The pucks  1306  may be made of any material having a high thermal conductivity, which is likely to be a metal and preferably a lightweight one, e.g. titanium, aluminum etc. The baseplate  1304  can be any suitable electrically insulating material (e.g. basalt composite, thermoplastic, etc.). The bottom cover  1302  provides a thermal path to the outside via the pucks  1306  but also has the benefit that the non-electrical conductive property of the baseplate  1304  acts as additional (and the most exterior) electrical isolation between the support structures  1106 . 
       FIG. 14  illustrates the bottom cover  1302  of  FIG. 13  in more detail. As can be seen, the baseplate  1304  has a plurality of apertures  1402  defined therein, each having a stepped perimeter  1406  as shown. Each puck  1306  (one shown inverted in  FIG. 14 ) has a corresponding stepped perimeter  1404  that engages with the perimeter  1406  defining the aperture  1402 , thereby to help position and secure the pucks  1306  when they are bonded in place in the bottom cover  1302 . 
       FIG. 15  illustrates a perspective view of a foot  1102  mounted to a bottom cover  1202  in an alternative example. In this example, the foot  1102  and at least part of the heat pipes  406  are powder coated to provide an additional layer of electrical insulation. The heat pipes  406  are assembled to the foot before powder coating. In one example, the entire subassembly  1502  of heat pipes  406  and foot  1102  may be powder coated. In another example, as shown for subassembly  1504 , the upper portion is masked prior to powder coating so that only the bottom portion is coated. 
     It will be appreciated that various combinations of the mounting arrangements described above with reference to  FIG. 12 ,  FIG. 13  and  FIG. 15  are possible. For example, the thermal insulation  1206  and thermal insulation  1208  of  FIG. 12  could also be provided in the example shown in  FIG. 15 . 
       FIG. 16  provides exploded perspective views of a cassette spine  1600 , according to example alternative examples, which is constructed from a series of connected or bridged support structures  1106 . 
     The arrangement of support structures  1106 , when assembled to form the cassette spine  1600 , provides a cassette-based architecture for the battery pack  100 , with a series of support structures  1106  each accommodating ten cylindrical battery cells to form cassette-based subassemblies (e.g. a battery cassette  304 ). 
     As will be described in further detail with respect to a subsequent figure, all five cells in an upper or lower group of five battery cells of the ten that are mounted to a single support structure  1106  are connected in parallel, so that the fives cells are all at the same electrical potential. This allows a group of ten mounted battery cells to be conveniently connected as discussed in more detail below. 
     As shown in more detail in  FIG. 11A , each support structure  1106  includes a foot  1102  to facilitate thermal coupling to the bottom cover  1202 . The two middle vertical members  1110  also each include a longitudinally extending hollow chamber, into which the heat pipes  406  are soldered or bonded. 
     Also provided in this example are aluminum ears  1604  that are welded to the support structures  1106  to form part of the electrical connection between the adjacent groups of battery cells as will be discussed in more detail below. 
     In order to construct the cassette spine  1600 , multiple support structures  1106  are connected to each other using bridges  1602 , which are shaped to receive the sides of adjacent support structures  1106 . The bridges  1602  are bonded to the support structures  1106  in order to physically couple, but electrically insulate, support structures  1106  from each other. In order to provide the electrical insulation, a bridge  1602  is made of an electrically insulating material, such as an injection molded plastic. A series of eight support structures  1106  may be connected in alternating orientations to form the cassette spine  1600 . End caps  1606 , made of the same material as the bridges  1602 , are shaped for engagement with the final support structure  1106  and are angled relative to the support structures  1106  to provide an exterior attachment surface  1608  at each end of the cassette spine  1600  that is parallel to the cross structures  110 . 
     The bridges  1602  thus serve to electrically insulate the mounted battery cells and their support structures  1106  from each other in order to prevent shorting. Each the group of ten cylindrical battery cells thereby constitutes a building element of a battery cassette  304 , which in turn constitutes a building block of a cassette stack  102 , with a dedicated thermal path from each group of battery cells to the bottom cover  202 . 
     As with the examples of  FIG. 5  and  FIG. 6 , a first set of five battery cells are mounted to the top half of the support structure  1106  in a first alignment. In this first alignment, the respective vents of each of these five battery cells are located at an upper end of the support structure  1106 , so that the vents would discharge in an upward direction and away from the second set of five battery cells that are mounted to the bottom of the support structure  1106 . Similarly, the second set of five battery cells are mounted to the bottom half of the support structure  1106  in a second alignment with the respective vents of each of these five battery cells being located at a lower end of the support structure  402 , so that the vents would discharge in a downward direction and away from the first set of five battery cells. 
     The assembled cassette spine  1600  serves a number of purposes. Firstly, it provides a support structure to which battery cells can be mounted. Secondly, it provides a thermal path, via support structures  1106 , that collects and directs heat away from the cells. Thirdly, it provides an electrically conductive path, via support structure  1106 , along which current can flow through the battery pack  100  as will be described further below. Finally, the cassette spine  1600  is also a structural element that transfers gravitational or g-force loads experienced by the battery cells to the cross structures  110 . 
       FIG. 17  provides an exploded perspective view of a battery cassette  1700  and shows specifically how the various components are assembled into the cassette spine  1600  shown in  FIG. 16 . 
     A first battery cell group  1702 , with each of an upper pair and a lower pair battery cells being vertically stacked in an opposing orientation, are attached to a first side of a support structure  1106  forming part of a cassette spine  1600 . A second battery cell group  1704 , with each of an upper three and a low three battery cells being vertically stacked in opposing directions, are attached to a second side of the support structure  1106 . Specifically, each of the battery cell group  1702  and battery cell group  1704  are bonded to a respective support structure  1106  by a thermally conductive epoxy, so as to thermally couple the battery cells to the support structure  1106  and so that the support structure  1106  can operationally conduct thermal energy to a heatsink. 
     A bottom cell interconnect  1706  is welded to the negative terminals of each of the battery cell group  1702  and battery cell group  1704  prior to the assembly of each battery group to the cassette spine  1600 . Each bottom cell interconnect  1706  has a pair of wings that depend therefrom along the side of the battery cell group and which, when the relevant set of battery cells is inserted into a support structure  1106 , are in electrical contact (e.g., through an electrically conductive weld) with the support structure  1106 . Accordingly, each support structure  1106  is electrically coupled to the negative terminals of a group of ten battery cells that are mounted to the support structure  1106 , which effectively becomes a negative terminal for all of the ten cells mounted thereto. After assembly of battery cell group  1702  and battery cell group  1704  to the cassette spine  1600 , a top cell interconnect  506  is welded to the top ends (positive terminals) of the upper five cylindrical battery cells, and also to the lower ends (also the positive terminals) of the lower five cylindrical battery cells. 
     Each bottom cell interconnect  1706  and top cell interconnect  1708  is constructed from aluminum and stamped to create a laminated bus between the respective positive ends of a groups of ten cells in one cassette spine  1600  and the negative terminals of a group of ten cells in an adjacent battery cassette  1700  (via the support structure  1106  and its ears  1604 ) upon insertion of the battery cassettes  1700  into a cassette stack  102 . 
     It should be noted that each group of ten cells attached to a support structure  1106  in one battery cassette  1700  faces in the opposite direction to any adjacent groups of ten cells attached to an adjacent support structure  1106  in the same battery cassette  1700 , due to adjacent support structures being assembled in opposite directions. This can clearly be seen since only four of the eight feet  1102  in the battery cassette  1700  are visible in  FIG. 17 . This allows for compact packaging since the numbers of cells along one upper or lower side of the  1400  alternate in number (e.g. 2-3-2-3-2-3-2-3) but more importantly, this arrangement means that, when battery cassettes  1700  are assembled into a battery cassettes  304 , current can flow between groups of cells in adjacent battery cassettes  1700  in alternating directions as shown in more detail in  FIG. 22 . 
       FIG. 18  is a perspective diagram illustrating the electrical interconnections between battery groups in three adjacent battery cassettes  1700 . Illustrated are three groups of battery cells, group one  1802 , group two  1804  and group three  1806 . As can be seen and referring to  FIG. 17 , current flows from the negative terminals  1808  of the cells in group one  1802 , through the bottom cell interconnects  1706  (see  FIG. 17 ) into the support structure  1106  as shown by arrows  1810 . The current then flows in either direction to ears  1604  as shown by arrows  1812 . From each ear  1604 , current flows to the corresponding top cell interconnect  1708  of group two  1804  as shown by arrows  1814 . The current then enters the positive terminals of the cells in group two  1804 . After passing through the cells in group two  1804 , the current then leaves the negative terminals of the cells in group two  1804  where it passes though the group two bottom cell interconnects  1706 , support structure  1106  (via ears  1604 ) and on to the group three top cell interconnects  1708 , and so on. 
     Known cell arrangements typically provide exposure of both the positive and negative terminals of any cluster or group of batteries, so as to allow interconnection between terminals of respective clusters. The current example is advantageous in that it avoids a constraint of having both the negative and positive terminals of every cluster being exposed, by electrically coupling the negative terminal to a supporting support structure  1106 , and extending the positive terminals of a first group of cylindrical cells from one side of a battery cassette  1700  and into contact with the support structure  1106  of a group of cells in a neighboring battery cassette  1700 . 
       FIG. 19  is an exploded perspective view of a plurality of battery cassettes  1700  showing how they are arranged side by side to form a cassette stack  1902  in the configuration found in the battery pack. Also shown in the example of  FIG. 19  are cell monitoring modules  1904  in the form of flexible PCB strips that monitor cell temperatures and voltages. Each cell monitoring module  1904  includes temperature sensors at intervals as well as electrical connections to some or all of the top cell interconnects  1708  along the upper surface of the battery groups, e.g. group one  1802 . The cell monitoring modules  1904  are connected to the battery management system (BMS) module  104  so that it can continuously monitor the state of the battery and take appropriate action in the event that a temperature or voltage problem is detected. The cell monitoring modules  1904  also facilitate battery balancing (during charging) of the attached cell groups via discharge resistors that are thermally coupled to the top cell interconnects  1708 . 
       FIG. 20A  is a perspective view of a top cell interconnect  1708 . The top cell interconnect  1708  includes three terminals  2002  that are welded in use to the positive terminals of the upper set of battery cell group  1704  and two legs  2004  that in use reach back to connect to ears  1604  (see  FIG. 16 ). The top cell interconnect  1708  also includes a tab  2006  that extends upwardly therefrom. 
       FIG. 20B  is a partial perspective view of the cell monitoring module  1904 , showing its relationship to a top cell interconnect  1708 . The cell monitoring module  1904  includes a PCB  2008  and a plurality of electrical components including a balancing discharge resistor  2010 . The tab  2006  of the top cell interconnect  1708  is received into a slot in the PCB  2008  adjacent to the resistor  2010 . The tab  2006  serves to position the cell monitoring module  1904  as well as to facilitate a thermal path for heat generated by the resistor  2010  to the support structure  1106  via the top cell interconnect  1708  and the ears  1604 . 
       FIG. 21  is an exploded view of a battery pack  2100  in accordance with another example. The battery pack  2100  comprises a cassette stack  1902 , which is contained within a housing. The cassette stack  1902  is constructed of 25 battery cassettes  1700 , each of which in turn includes 80 cylindrical battery cells secured within a collection of interconnected support structures  1106 . 
     The housing includes a top cover  2102 , an end plate  2104 , a BMS module  2108 , a pair of sidewalls  2106 , and a bottom cover  2110 . These components are connected and welded together (or otherwise sealed together) to create an environmental seal around the cassette stack  1902 . Each of the sidewalls  2106  is attached to the end caps  1606  of each battery cassette  1700 , and provides a load path from the cassette stack  1902  to a pair of mounting flanges  2112  located at the lower corners of each sidewall  2106 . The mounting flanges  2112  are used to mount the battery pack  2100  to complementary mounting structures in the battery cavity of aerial vehicle  3600 . 
     The BMS module  2108  and end plate  2104  are also attached to the sidewalls  2106 . The top cover  2102  is made of titanium sheet for flame and vent gas containment and includes a Kapton layer on its lower surface for electrical insulation. 
     The bottom cover  2110  is also made of titanium sheet for flame and vent gas containment and includes a Kapton layer on its upper surface for electrical insulation as discussed previously. The bottom cover  202  is the final component in the thermal path between the battery cells and the outside air that includes the support structures  1106 , the heat pipes  406  and the feet  412 . 
     The bottom cover  2110  may be used to support both active and passive heat extraction from the battery pack  2100 . Specifically, the bottom cover  2110  may be exposed as an outer surface of the aerial vehicle  3600 , and thus subject to high velocity airflow during flight. This high velocity airflow is effective in passively extracting heat from the battery pack  2100 . When the aerial vehicle is landed and docked, an active cooling system may furthermore thermally engage the bottom cover  2110 , so as to actively extract thermal energy from the battery pack  2100 . 
       FIG. 22  is a perspective view of a battery pack  2100 , according to one example, and illustrates the direction of current flow between adjacent battery cassettes  1700 , with the arrows indicating the direction of current flow within the battery pack  2100  and between the battery cassettes  1700  in operation of the battery pack  2100 . 
     Referring to both  FIG. 22  and  FIG. 18 , current returning to the battery pack  2100  enters the cassette stack  1902  at the positive terminal  2202  of the battery pack  2100  at the first (lowermost) group of cells (e.g. group one  1802  in  FIG. 18 ) in the battery cassette  1700  located next to the BMS module  2108 . As described above in more detail with reference to  FIG. 18 , current flows through the first group of cells from both upper and lower top cell interconnects  1708  to the ears  1604  and then to the upper and lower top cell interconnects  1708  in the group of cells (e.g. group two  1804 ) in the next battery cassette  1700 . The current passes in this manner along the lowermost row of groups of cells in the battery pack  2100  from right to left, from one battery cassette  1700  to the next until it reaches the lowermost group of cells in the battery cassette  1700  next to the end plate  2104 . An electrical interconnect then passes the current up (in the figure) to the next group of cells in the battery cassette  1700  next to the end plate  2104 . 
     The current then flows in the opposite direction in the same manner as before, and this process repeats with the current passing back and forth and upward (in the figure) until the current exits the battery pack  2100  at the negative terminal  2204 . Also provided, half way along the current path is a mid-pack fuse and disconnect block  2206  that may trip automatically or under control of the BMS module  2108  in case of a problem with the battery pack  2100 . 
       FIG. 23  is a vertical and longitudinal cross section through the battery pack  2100  to illustrate the venting path for any flame, vent gas, or other cell ejecta. Any such cell emissions from the top layer of cells are directed towards the top cover  2102  and any such cell emissions from the bottom layer of cells are directed towards the bottom cover  2110  by virtue of the upper and lower cells being mounted with their vents facing away from each other in opposite directions as discussed above. 
     The emissions are initially contained by the battery pack enclosure (top cover  2102 , bottom cover  2110  and sidewalls  2106 ) and are thus directed towards the BMS module  2108  and end plate  2104 , where they pass out of the battery pack  2100  through a number of umbrella valves  2302  located in the end plate  2104  and the wall of the BMS module  2108 . A gap (e.g. 15 mm) is provided between the cassette stack  1902  and the top cover  2102  for this purpose. Emissions directed towards the bottom cover  2110  flow below the individual cells and above the feet  1102  along the bottom cover  2110 . 
       FIG. 24  is a perspective view of a one-piece cassette chassis  2402  into which preassembled cell groups  2404  can be mounted, as an alternative to the cassette spines discussed above. The cassette chassis  2402  comprises a number of vertical dividers  2406  that separate and isolate adjacent cell groups  2404 , as well as end caps  2408  for use in mounting the cassette chassis  2402  to the sidewalls  2106 . 
     Upper and lower cross members  2410  separate the dividers  2406  from each other (and the end caps  2408  from the dividers  2406 ) to define spaces into which cell groups  2404  can be received. The cross members  2410  are shaped to conform to the external surface of a cell group  2404  on one side thereby to permit secure adhesive bonding of the cell groups  2404  into the cassette chassis  2402 . It will be appreciated that the cassette chassis  2402  can hold two rows of cell groups  2404  compared to the cassette spines discussed above with reference to  FIG. 4  and  FIG. 16 , which only comprise a single row of cell groups. The cassette chassis  2402  may be injection molded glass-filled PBT (Polybutylene Terephthalate). 
       FIG. 25  is a perspective view of the one-piece cassette chassis  2402  of  FIG. 24 , partially filled with preassembled cell groups  2404 . As can be seen from the figure, the illustrated cell groups  2404  are shown as being assembled into the cassette chassis  2402  with the side of each cell group  2404  having four cells facing towards the cassette chassis  2402 . Opposite each cell group  2404  placed into the cassette in this direction is a space (e.g. spaces  2502 ) that can receive a cell group  2404  with its six cell side facing towards the cassette chassis  2402 . Accordingly, a cassette stack formed by assembling cell groups  2404  to a cassette chassis  2402  will have twice as many cells as a cassette stack  102  or a cassette stack  1902 . 
     Forming the bridge or spine between cell groups as a cassette chassis  2402  reduces the number of parts and simplifies assembly of the cassette stack. 
       FIG. 26  is an exploded perspective view of the cell group  2404  shown in  FIG. 25 , which illustrates specifically how the various components are assembled to form the cell group  2404   
     A first battery cell group  2602 , with each of an upper pair and a lower pair battery cells being vertically stacked in an opposing orientation, are attached to a first side of a support structure  1116  including heat pipes  406  and a foot  1112 . A second battery cell group  2604 , with each of an upper three and a low three battery cells being vertically stacked in opposing directions, are attached to a second side of the support structure  1116 . Specifically, each of the first battery cell group  2602  and battery cell group  2304  are bonded to a respective support structure  1116  by a thermally conductive epoxy, so as to thermally couple the battery cells to the support structure  1116  and so that the support structure  1116  can operationally conduct thermal energy to a heatsink. 
     Prior to attaching the battery cell groups, a bottom cell interconnect  2606  is welded to the negative terminals of each of the second battery cell group  2604  and a bottom cell interconnect  2608  is welded to the negative terminals of each of the first battery cell group  2602  prior to the assembly of each battery group to the support structure  1116 . Each bottom cell interconnect  2606  and bottom cell interconnect  2608  has a pair of wings that depend therefrom along the side of the battery cell group and which, when the relevant set of battery cells is inserted into a support structure  1116 , are in electrical contact (e.g., through an electrically conductive weld) with, and form part of, the support structure  1116 . Accordingly, each support structure  1116  is electrically coupled to the negative terminals of a group of ten battery cells that are mounted to the support structure  11166 , which effectively becomes a negative terminal for all ten of the cells mounted thereto. 
     After assembly of second first battery cell group  2602  and second battery cell group  2604  to support structure  1116 , a top cell interconnect  1708  is welded to the top ends (positive terminals) of the upper five cylindrical battery cells, and also to the lower ends (also the positive terminals) of the lower five cylindrical battery cells. 
     Each of the top cell interconnects  1708 , bottom cell interconnect  2606  and bottom cell interconnect  2608  is constructed from aluminum and stamped to create a laminated bus between the respective positive ends of a groups of ten cells and the negative terminals of an adjacent group of ten cells in that are either in the same battery cassette or an adjacent battery cassette as discussed with reference to  FIG. 25 . 
       FIG. 27  is a perspective diagram illustrating the electrical interconnections between adjacent battery cell groups  2404 . Illustrated are three groups of battery cells, group one  2702 , group two  2704  and group three  2706 . As can be seen from the figure, and also referring to  FIG. 26 , current flows from the negative terminals  2708  of the cells in group one  2702 , through the bottom cell interconnects  2606  and the bottom cell interconnects  2608  into the support structure  1116  as shown by arrow  2712 . The current then flows in either direction along support structure  1116  toward the upper and lower top cell interconnects  2710  as shown by arrow  2714 . The current then flows through each top cell interconnect  2710  of group two  2704  as shown by arrow  2716  to the positive terminals of the cells in group two  2704 . After passing through the cells in group two  2704 , the current then leaves the negative terminals of the cells in group two  2704  where it passes though the group two  2704  bottom cell interconnects  2606 , bottom cell interconnects  2608 , support structure  1116  and on to the group three  2706  top cell interconnects  2710 , and so on. 
       FIG. 28  shows a temperature graph  2800 , illustrating the effect of passive cooling as a result of airflow over a heat sink (e.g., bottom cover  2110 ) and via ducting, described above, and active cooling, described below, through various operational states of the aerial vehicle  3600 . An example of the variation of the average temperature of a battery pack  2100  over repeated flights and recharge cycles is illustrated by temperature curve  2802 , which is preferably within an operational envelope defined by upper limit  2804  and lower limit  2806 . 
     At takeoff, the battery pack may for example have an average desired temperature of about 40 deg C. As the aerial vehicle  3600  performs a vertical takeoff, the average temperature will rise at  2808 , since there is not much flow of air over the bottom cover  2110  or through the ducting. In the absence of any convection, the power draw on the battery would result in an increase of about 25 deg C., but as the aerial vehicle  3600  transitions to horizontal flight, airflow over the bottom cover  2110  and ducted flow over the top cover  302  increase the heat transfer from the battery and the average temperature stabilizes as at  2810 . As the as the aerial vehicle  3600  transitions to vertical flight for landing, reduced airflow causes the average temperature to rise as at  2812 . Once the aerial vehicle  3600  has landed and is being recharged, ground-based cooling removes residual heat from the landing as well as additional heat generated by recharging the battery as at  2814 , with a goal of returning the average temperature to 40 deg. C. for the next flight as at  2816 . This temperature cycle then repeats throughout a typical day. 
       FIG. 29  is an exploded perspective view of a battery pack  2900 , according to a further example. The battery pack  2900  is constructed using a number of submodules, which are further illustrated in subsequent figures. At a high-level, the battery pack  2900  has a housing comprising a top cover  2902 , an enclosure  2906 , and a bottom cover  2910 . The enclosure  2906  defines upper and lower cavities, with a first battery module  2904  being located in the upper cavity, and a second battery module  2908  being in the lower cavity. The housing provides an environmental seal for each of the battery module  2904  and enclosure  2906 . The battery module  2904  and battery module  2908  differ from those described with respect to  FIG. 1 , in that they are only one cell in height. 
       FIG. 30  is an exploded perspective view of a battery submodule  3000 , according some examples, which may be used to construct each of the battery module  2904  and battery module  2908 . Specifically, each of the battery module  2904  and battery module  2908  may be constructed of a pair of battery submodules  3000 . 
     Each battery submodule  3000  is constructed using multiple battery cell assemblies, each battery cell assembly comprising a first cell group  3006  and a second cell group  3010 , which are mounted, in opposite orientation, to a support structure  3008 . For example, the battery cells of the first cell group  3006  may be oriented with their positive ends at an upper end of a cell assembly, and the battery cells of the second cell group  3010  may be oriented with their positive ends at a lower end of a cell assembly. A cell interconnect  3002  is positioned on top of the top ring cap  3004 . 
     Multiple cell assemblies are then sandwiched between a top ring cap  3004  and a bottom ring cap  3012 . 
       FIG. 31  shows further details regarding the battery pack  2900 , illustrating location of a firewall  3102  in the enclosure so as to create a split between the battery module  2904  and battery module  2908 . A thermal path  3104  passes through the firewall  3102 . 
       FIG. 32  is a perspective view of a spray cooler  3200  for use in ground-based cooling of one or more battery packs  3202  located on the underside of an aerial vehicle  3600 . 
     The spray cooler  3200  comprises a rectangular trough  3204  with a compliant seal  3206  around its upper periphery to make a rough seal against the battery packs  3202  and/or the underside of the aerial vehicle  3600 . The spray cooler  3200  also has a floor  3208  that is sloped from both ends of the spray cooler  3200  towards a drain  3210  located in the center of the spray cooler  3200 . The drain  3210  is connected to an outlet pipe  3212 , which returns warmer water to a chiller  3222  where it is cooled prior to return to the spray cooler  3200 . 
     Cold water from the chiller  3222  is fed to the trough through two inlet pipes  3214 , passing through a manifold  3216  into a series of pipes  3218  running underneath the spray cooler  3200 . The pipes  3218  feed an array of spray heads  3220  mounted to the floor of the spray cooler  3200  and that are arranged to spray cold water upwards to cool the one or more battery packs  3202 . 
     In use, the aerial vehicle  3600  is either positioned over the spray cooler  3200  or the spray cooler  3200  is positioned under the aerial vehicle  3600  (for example, the spray cooler  3200  may be mounted on a cart). The spray cooler  3200  is then raised by an appropriate mechanism until the seal  3206  engages the one or more battery packs  3202  or the underside of the aerial vehicle  3600 . Cold water is then sprayed against the underside of the one or more battery packs  3202  (e.g. against the bottom cover  2110  of each battery pack) or the underside of the aerial vehicle  3600  to transfer heat from the one or more battery packs  3202  to the water. 
     The trough  3204  collects the water and, after exiting the spray cooler  3200  via the drain  3210 , the warmer/hotter water returns to a chiller  3222  (e.g. a heat pump or refrigeration unit) to cool the water before returning it to the spray cooler  3200  via the inlet pipes  3214 . Additional necessary equipment is provided to ensure the proper functioning of the spray cooler  3200 , e.g. a pump  3224  to circulate the water, temperature sensors to monitor the water temperature, and an appropriate manual or automated control unit  3226  to turn on or shut off the spray cooler  3200  at an appropriate time or when appropriate conditions are detected, for example when the battery packs  3202  are charged and at the target temperature. 
     In one example, the water entering the  2900  is at 2.5 deg C., the water leaving the  2900  is at 7.5 deg C., to maintain the bottom of the battery pack  3202  at 10 deg C. 
       FIG. 33  is a perspective view of a cold plate  3300  for use in ground-based cooling of one or more battery packs, e.g. battery pack  3320  located on the underside of an aerial vehicle  3302 . 
     The cold plate  3300  comprises a rectangular block  3304  that has internal fluid channels formed therein through which a coolant (e.g. water) can be circulated to cool the block  3304 . The internal fluid channels are coupled to a cold inlet  3308  and a warm outlet  3310 . As can be seen from the schematic  3322 , in one example the coolant enters the block  3304  at the cold inlet  3308  and is distributed to a number of channels that run in parallel along the length of the block  3304  from a first end to a second end of the block  3304 . Each channel then returns in the opposite direction from the second end to the first end, where they are combined into a single channel that is coupled to the warm outlet  3310 . 
     Located on the upper surface of the block  3304  is a pad  3306  made of a material that is compliant and transfers heat efficiently. This permits the cold plate  3300 , to make reasonably intimate contact with the battery pack  3320  for efficient heat transfer from the battery pack and/or the underside of the aerial vehicle to the cold plate  3300 . 
     Additional necessary equipment is provided to ensure the proper functioning of the cold plate  3300  is provided, as discussed with reference to  FIG. 32 ., e.g. a chiller  3222  (a heat pump or refrigeration unit) to supply cold coolant to the cold inlet  3308  and receive warm/hotter coolant from the  3010 , a pump  3224  to circulate the coolant, temperature sensors to monitor the coolant temperature, and an appropriate manual or automated control unit  3226  to turn on or shut off circulation of coolant through the cold plate  3300  at an appropriate time or when appropriate conditions are detected, for example when the battery packs  3202  are charged and at the target temperature. 
     In use, the aerial vehicle  3302  is either positioned over the cold plate  3300  or the cold plate  3300  is positioned under the aerial vehicle  3600 . In the illustrated example, the cold plate  3300  is mounted on a cart  3312  that can be positioned under the aerial vehicle  3302  The cold plate  3300  is then raised by an appropriate lift mechanism  3314  until the pad  3306  engages the battery pack  3320  or the underside of the aerial vehicle  3600 . Coolant is then circulated through the cold plate  3300  to transfer heat from the battery pack  3320  (or one or more battery packs) to the coolant. Upon after exiting the cold plate  3300  via the warm outlet  3310 , the warmer/hotter coolant returns to the chiller  3222  to be cooled before being returned to the block  3304  via the cold inlet  3308 . 
     As can be seen from the figure, the cold plate  3300  can be adapted in size and shape for use with different battery packs, e.g. battery pack  3316  in an engine nacelle or battery pack  3318  in a wing. 
       FIG. 34  is a flowchart describing cooling of a battery pack in accordance with one example, using the cooling structures described above with reference to  FIG. 32  and  FIG. 33 . 
     The method commences at operation  3402  with the aerial vehicle  3600  and the cooling structure (e.g. spray cooler  3200  or cold plate  3300 ) being aligned. This can be accomplished by the aerial vehicle  3600  moving into position above or at the cooling structure, or by the cooling structure being moved into position under or at the aerial vehicle  3600 , or some combination of the two. The cooling structure may for example be located at a charging station for the aerial vehicle  3600 , and alignment may occur once the aerial vehicle  3600  is parked at the charging station. The alignment between the aerial vehicle  3600  and the cooling structure may be verified automatically, for example by having the control unit  3226  detect or recognize markings or features on the bottom cover of the battery pack or on the bottom of the aerial vehicle  3600 . 
     When the aerial vehicle  3600  and the cooling structure are aligned, the cooling structure is moved into contact with a heat transfer surface of the aerial vehicle  3600  or of the battery pack  100  at operation  3404  using a lift mechanism  3314  in one example. The cooling structure is then operated, as described for example with reference to  FIG. 32  or  FIG. 33 , to transfer heat from the heat transfer surface at operation  3406 . The movement and activation of the cooling structure may be performed by an operator actuating the lift mechanism  3314  and the control unit  3226 . Alternatively, the movement and activation of the cooling structure may be accomplished under computer control. For example, under control of one or more processors in the aerial vehicle  3600 , in a collocated charging station or in the control unit  3226 . 
     Computer control of the operation of the cooling structure will depend on a number of factors, including for example the state of charge or charging of the battery and the temperature of the battery pack. Appropriate direct or networked communications links will be established to, for example, permit instructions to be passed from the aerial vehicle  3600  to the control unit  3226 , or from the charging station to the control unit  3226 , or for the control unit  3226  to receive appropriate parameters from the aerial vehicle  3600  or the charging station. 
     For example, operation  3404  and operation  3404  could commence after the alignment of operation  3402  if the temperature of the battery pack  100  is above a certain value, or charging of the battery pack  100  has commenced. 
     Operation  3404  continues until the cooling cycle ends at operation  3408 . Ending of the cooling cycle can be determined manually or can be done under computer control. For example, the end of the cooling cycle can be detected when charging of the battery pack  100  ceases and the temperature of the battery pack  100  reaches a target minimum threshold. 
     In response to the cooling cycle ending, the cooling structure is moved away from the heat transfer surface at operation  3410  using, for example, the lift mechanism  3314 . Additionally, the operation of the cooling structure itself will typically end, either at the time the cooling cycle ends or shortly thereafter. Movement of the cooling structure away from the heat transfer surface and termination of operation of the cooling structure can be performed manually or under computer control after the end of the cooling cycle has been determined or signaled. 
       FIG. 35  is a block diagram illustrating an avionics system  3500 , including an aerial vehicle control system  3508 , an aerial vehicle autonomy system  3504 , an electric motor control system  3506  and tilt control system  3510 , located within the avionics bay  3502  of one of the aerial vehicles discussed herein. The battery unit  3532  or the battery unit  3532  may be constructed as described herein. 
     The avionics system  3500  may be primarily located within an avionics bay  3502  of an aerial vehicle. Turning to each of the respective components, the aerial vehicle autonomy system  3504  it is responsible for autonomous or semiautonomous operation of an aerial vehicle, and is communicatively coupled to the sensors  3512  of the relevant aerial vehicle. The sensors  3512  may include LIDAR sensors, radar sensors and cameras, merely for example. The aerial vehicle autonomy system  3504  it is communicatively coupled to the primary aerial vehicle control system  3508 , which is in turn coupled to the various pitch, yaw and throttle controllers of the aerial vehicle. The aerial vehicle control system  3508  may further control the electric motor control system  3506 . The electric motor control system  3506  in turn operationally controls electric motors of the aerial vehicle, including a number of rotors (or propulsors) of the aerial vehicle. These rotors include a fixed rotor  3514 , a fixed rotor  3516 , a right rear (or aft) tilt rotor  3522 , a left forward tilt rotor  3520  and a right forward tilt rotor  3518 . In the example, the fixed rotor  3514  and the fixed rotor  3516  are each mounted on a respective tilting outer wing sections of first and second wings of the aerial vehicle. The tilt rotor  3522  and tilt rotor  3520  are mounted respectively on a first engine nacelle and a second engine nacelle, these nacelles being tiltable. 
     The aerial vehicle control system  3508  is furthermore communicatively coupled to, and controls a tilt control system  3510 . The tilt control system  3510  is responsible for the tilting or rotation of various components of the aerial vehicle in order to provide enhanced control and flight stability of the aerial vehicle, as well as the implementation of countermeasures to mitigate the impact of an electrical or component failure of the aerial vehicle. To this end, the tilt control system  3510  is shown to be communicatively coupled to a tilt mechanism  3524  (e.g., which includes a rotator to rotate a rotor wing on which is mounted the fixed rotor  3514 ), a tilt mechanism  3526  (e.g., which includes a rotator to rotate a rotor wing on which is mounted the fixed rotor  3516 ), a tilt mechanism  3528  (e.g., which includes rotators to rotate forward tilt each of the left forward tilt rotor  3520 , the right to react tilt rotor  3522  and the right forward tilt rotator  116 . 
     The tilt control system  3510  is also communicatively coupled to, controls, a battery controller  3530  that is operatively able to move (e.g., rotate or laterally move) a battery unit  3532  and a battery unit  3534  of a battery system of the aerial vehicle. Further details regarding operations of the various systems and subsystems described in  FIG. 35  will be provided below. 
       FIG. 36  is a block diagram showing a system architecture of an aerial vehicle  3600 , according to example aspects of the present disclosure. The aerial vehicle  3600  can be, for example, be an autonomous or semi-autonomous aerial vehicle. The aerial vehicle  3600  includes one or more sensors  3512 , an aerial vehicle autonomy system  3504 , and one or more aerial vehicle control system  3508 . 
     The aerial vehicle autonomy system  3504  can be engaged to control the aerial vehicle  3600  or to assist in controlling the aerial vehicle  3600 . In particular, the aerial vehicle autonomy system  3504  receives sensor data from the sensors  3512 , attempts to comprehend the environment surrounding the aerial vehicle  3600  by performing various processing techniques on data collected by the sensors  3512  and generates an appropriate motion path through an environment. The aerial vehicle autonomy system  3504  can control the one or more aerial vehicle control system  3508  to operate the aerial vehicle  3600  according to the motion path. 
     The aerial vehicle autonomy system  3504  includes a perception system  3616 , a prediction system  3618 , a motion planning system  3622 , and a pose system  3620  that cooperate to perceive the surrounding environment of the aerial vehicle  3600  and determine a motion plan for controlling the motion of the aerial vehicle  3600  accordingly. 
     Various portions of the aerial vehicle autonomy system  3504  receive sensor data from the sensors  3512 . For example, the sensors  3512  may include remote-detection sensors as well as motion sensors such as an inertial measurement unit (IMU), one or more encoders, etc. The sensor data can include information that describes the location of objects within the surrounding environment of the aerial vehicle  3600 , information that describes the motion of the vehicle, etc. 
     The sensors  3512  may also include one or more remote-detection sensors or sensor systems, such as a LIDAR, a RADAR, one or more cameras, etc. As one example, a LIDAR system of the sensors  3512  generates sensor data (e.g., remote-detection sensor data) that includes the location (e.g., in three-dimensional space relative to the LIDAR system) of a number of points that correspond to objects that have reflected a ranging laser. For example, the LIDAR system can measure distances by measuring the Time of flight (TOF) that it takes a short laser pulse to travel from the sensor to an object and back, calculating the distance from the known speed of light. 
     As another example, for a RADAR system of the sensors  3512  generates sensor data (e.g., remote-detection sensor data) that includes the location (e.g., in three-dimensional space relative to the RADAR system) of a number of points that correspond to objects that have reflected ranging radio waves. For example, radio waves (e.g., pulsed or continuous) transmitted by the RADAR system can reflect off an object and return to a receiver of the RADAR system, giving information about the object&#39;s location and speed. Thus, a RADAR system can provide useful information about the current speed of an object. 
     As yet another example, one or more cameras of the sensors  3512  may generate sensor data (e.g., remote sensor data) including still or moving images. Various processing techniques (e.g., range imaging techniques such as, for example, structure from motion, structured light, stereo triangulation, and/or other techniques) can be performed to identify the location (e.g., in three-dimensional space relative to the one or more cameras) of a number of points that correspond to objects that are depicted in image or images captured by the one or more cameras. Other sensor systems can identify the location of points that correspond to objects as well. 
     As another example, the sensors  3512  can include a positioning system. The positioning system can determine a current position of the aerial vehicle  3600 . The positioning system can be any device or circuitry for analyzing the position of the aerial vehicle  3600 . For example, the positioning system can determine a position by using one or more of inertial sensors, a satellite positioning system such as a Global Positioning System (GPS), based on IP address, by using triangulation and/or proximity to network access points or other network components (e.g., cellular towers, WiFi access points, etc.) and/or other suitable techniques. The position of the aerial vehicle  36000  can be used by various systems of the aerial vehicle autonomy system  3504 . 
     Thus, the sensors  3512  can be used to collect sensor data that includes information that describes the location (e.g., in three-dimensional space relative to the aerial vehicle  3600 ) of points that correspond to objects within the surrounding environment of the aerial vehicle  3600 . In some implementations, the sensors  3512  can be located at various different locations on the aerial vehicle  3600 . 
     The pose system  3620  receives some or all of the sensor data from the sensors  3512  and generates vehicle poses for the aerial vehicle  3600 . A vehicle pose describes the position (including altitude) and attitude of the vehicle. The position of the aerial vehicle  3600  is a point in a three dimensional space. In some examples, the position is described by values for a set of Cartesian coordinates, although any other suitable coordinate system may be used. The attitude of the aerial vehicle  3600  generally describes the way in which the aerial vehicle  3600  is oriented at its position. In some examples, attitude is described by a yaw about the vertical axis, a pitch about a first horizontal axis and a roll about a second horizontal axis. In some examples, the pose system  3620  generates vehicle poses periodically (e.g., every second, every half second, etc.) The pose system  3620  appends time stamps to vehicle poses, where the time stamp for a pose indicates the point in time that is described by the pose. The pose system  3620  generates vehicle poses by comparing sensor data (e.g., remote sensor data) to map data  3614  describing the surrounding environment of the aerial vehicle  3600 . 
     In some examples, the pose system  3620  includes localizers and a pose filter. Localizers generate pose estimates by comparing remote sensor data (e.g., LIDAR, RADAR, etc.) to map data. The pose filter receives pose estimates from the one or more localizers as well as other sensor data such as, for example, motion sensor data from an IMU, encoder, odometer, etc. In some examples, the pose filter executes a Kalman filter or other machine learning algorithm to combine pose estimates from the one or more localizers with motion sensor data to generate vehicle poses. In some examples, localizers generate pose estimates at a frequency less than the frequency at which the pose system  3620  generates vehicle poses. Accordingly, the pose filter generates some vehicle poses by extrapolating from a previous pose estimates. 
     The perception system  3616  detects objects in the surrounding environment of the aerial vehicle  3600  based on the sensor data, the map data  3614  and/or vehicle poses provided by the pose system  3620 . The map data  3614 , for example, may provide detailed information about the surrounding environment of the aerial vehicle  3600 . The map data  3614  can provide information regarding: the identity and location of geographic entities, such as different roadways, segments of roadways, buildings, or other items or objects (e.g., lampposts, crosswalks, curbing, etc.); the location and directions of traffic lanes (e.g., the location and direction of a parking lane, a turning lane, a bicycle lane, or other lanes within a particular roadway; traffic control data (e.g., the location and instructions of signage, traffic lights, or other traffic control devices); and/or any other map data that provides information that assists the aerial vehicle autonomy system  3504  in comprehending and perceiving its surrounding environment and its relationship thereto. The perception prediction system  3618  uses vehicle poses provided by the pose system  3620  to place aerial vehicle  3600  environment. 
     In some examples, the perception system  3616  determines state data for objects in the surrounding environment of the aerial vehicle  3600 . State data may describe a current state of an object (also referred to as features of the object). The state data for each object describes, for example, an estimate of the object&#39;s: current location (also referred to as position); current speed (also referred to as velocity); current acceleration; current heading; current orientation; size/shape/footprint (e.g., as represented by a bounding shape such as a bounding polygon or polyhedron); type/class (e.g., vehicle versus pedestrian versus bicycle versus other); yaw rate; distance from the aerial vehicle  3600 ; minimum path to interaction with the aerial vehicle  3600 ; minimum time duration to interaction with the aerial vehicle  3600 ; and/or other state information. 
     In some implementations, the perception system  3616  can determine state data for each object over a number of iterations. In particular, the perception system  3616  can update the state data for each object at each iteration. Thus, the perception system  3616  can detect and track objects, such as vehicles, that are proximate to the aerial vehicle  3600  over time. 
     The prediction system  3618  is configured to predict future positions for an object or objects in the environment surrounding the aerial vehicle  3600  (e.g., an object or objects detected by the perception system  303 ). The prediction system  3618  can generate prediction data associated with objects detected by the perception system  3616 . In some examples, the prediction system  3618  generates prediction data describing each of the respective objects detected by the perception system  3616 . 
     Prediction data for an object can be indicative of one or more predicted future locations of the object. For example, the prediction system  3618  may predict where the object will be located within the next 5 seconds, 20 seconds, 200 seconds, etc. Prediction data for an object may indicate a predicted trajectory (e.g., predicted path) for the object within the surrounding environment of the aerial vehicle  3600 . For example, the predicted trajectory (e.g., path) can indicate a path along which the respective object is predicted to travel over time (and/or the speed at which the object is predicted to travel along the predicted path). The prediction system  3618  generates prediction data for an object, for example, based on state data generated by the perception system  3616 . In some examples, the prediction system  3618  also considers one or more vehicle poses generated by the pose system  3620  and/or the map data  3614 . 
     In some examples, the prediction system  3618  uses state data indicative of an object type or classification to predict a trajectory for the object. As an example, the prediction system  3618  can use state data provided by the perception system  3616  to determine that particular object (e.g., an object classified as a vehicle). The prediction system  3618  can provide the predicted trajectories associated with the object(s) to the motion planning system  3622 . 
     In some implementations, the prediction system  3618  is a goal-oriented prediction system that generates potential goals, selects the most likely potential goals, and develops trajectories by which the object can achieve the selected goals. For example, the prediction system  3618  can include a scenario generation system that generates and/or scores the goals for an object and a scenario development system that determines the trajectories by which the object can achieve the goals. In some implementations, the prediction system  3618  can include a machine-learned goal-scoring model, a machine-learned trajectory development model, and/or other machine-learned models. 
     The motion planning system  3622  determines a motion plan for the aerial vehicle  3600  based at least in part on the predicted trajectories associated with the objects within the surrounding environment of the aerial vehicle  3600 , the state data for the objects provided by the perception system  3616 , vehicle poses provided by the pose system  3620 , and/or the map data  3614 . Stated differently, given information about the current locations of objects and/or predicted trajectories of objects within the surrounding environment of the aerial vehicle  3600 , the motion planning system  3622  can determine a motion plan for the aerial vehicle  3600  that best navigates the aerial vehicle  3600  relative to the objects at such locations and their predicted trajectories on acceptable roadways. 
     In some implementations, the motion planning system  3622  can evaluate cost functions and/or one or more reward functions for each of one or more candidate motion plans for the aerial vehicle  3600 . For example, the cost function(s) can describe a cost (e.g., over time) of adhering to a particular candidate motion plan while the reward function(s) can describe a reward for adhering to the particular candidate motion plan. For example, the reward can be of opposite sign to the cost. 
     Thus, given information about the current locations and/or predicted future locations/trajectories of objects, the motion planning system  3622  can determine a total cost (e.g., a sum of the cost(s) and/or reward(s) provided by the cost function(s) and/or reward function(s)) of adhering to a particular candidate pathway. The motion planning system  3622  can select or determine a motion plan for the aerial vehicle  3600  based at least in part on the cost function(s) and the reward function(s). For example, the motion plan that minimizes the total cost can be selected or otherwise determined. The motion plan can be, for example, a path along which the aerial vehicle  3600  will travel in one or more forthcoming time periods. In some implementations, the motion planning system  3622  can be configured to iteratively update the motion plan for the aerial vehicle  3600  as new sensor data is obtained from the sensors  3512 . For example, as new sensor data is obtained from the sensors  3512 , the sensor data can be analyzed by the perception system  3616 , the prediction system  3618 , and the motion planning system  3622  to determine the motion plan. 
     Each of the perception system  3616 , the prediction system  3618 , the motion planning system  3622 , and the pose system  3620 , can be included in or otherwise a part of the aerial vehicle  3600  configured to determine a motion plan based on data obtained from the sensors  3512 . For example, data obtained by the sensors  3512  can be analyzed by each of the perception system  3616 , the prediction system  3618 , and the motion planning system  3622  in a consecutive fashion in order to develop the motion plan. While  FIG. 36  depicts elements suitable for use in a vehicle autonomy system according to example aspects of the present disclosure, one of ordinary skill in the art will recognize that other vehicle autonomy systems can be configured to determine a motion plan for an autonomous vehicle based on sensor data. 
     The motion planning system  3622  can provide the motion plan to aerial vehicle control system  3508  to execute the motion plan. For example, the aerial vehicle control system  3508  can include pitch control module  3624 , yaw control module  3626 , and a throttle control system  3628 , each of which can include various vehicle controls (e.g., actuators or other devices or motors that control power) to control the motion of the aerial vehicle  3600 . The various aerial vehicle control system  3508  can include one or more controllers, control devices, motors, and/or processors. 
     A throttle control system  3628  is configured to receive all or part of the motion plan and generate a throttle command. The throttle command is provided to an engine and/or engine controller, or other propulsion system component to control the engine or other propulsion system of the aerial vehicle  3600 . 
     The aerial vehicle autonomy system  3504  includes one or more computing devices, such as the computing device  3602  which may implement all or parts of the perception system  3616 , the prediction system  3618 , the motion planning system  3622  and/or the pose system  3620 . The example computing device  3602  can include one or more processors  3604  and one or more memory devices (collectively referred to as memory  3608 ). The processors  3604  can be any suitable processing device (e.g., a processor core, a microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a microcontroller, etc.) and can be one processor or a plurality of processors that are operatively connected. The memory  314  can include one or more non-transitory computer-readable storage mediums, such as Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), flash memory devices, magnetic disks, etc., and combinations thereof. The memory  3608  can store data  3612  and instructions  3610  which can be executed by the processors  3604  to cause the aerial vehicle autonomy system  3504  to perform operations. The computing device  3602  can also include a communications interface  3606 , which can allow the computing device  3602  to communicate with other components of the aerial vehicle  3600  or external computing systems, such as via one or more wired or wireless networks. Additional descriptions of hardware and software configurations for computing devices, such as the computing device  3602  are provided herein.