Patent Publication Number: US-2023147841-A1

Title: Battery cassette

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/906,931, filed Sep. 27, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of this disclosure relate to battery systems. 
     BACKGROUND 
     An electric vehicle (EV), also referred to as an electric drive vehicle, uses an electric motor for propulsion. Electric vehicles may include all-electric vehicles where the electric motor is the sole source of power, and hybrid electric vehicles that include an auxiliary power source in addition to the electric motor. In an electric vehicle, energy may be stored in a rechargeable battery system that includes multiple battery cells to power the electric motor. The battery system typically includes a plurality of battery packs that each include a plurality of battery modules. Each battery module includes multiple battery cells. Standard battery packs use fixed size modules to create battery packs. 
     Battery modules are the base building blocks of a battery pack. A battery module includes multiple battery cells connected together in parallel and series. Typically, a battery module is not sub-dividable and is not easy to scale up or down in size. For example, existing battery module designs include a fixed amount of battery cells and voltages where changing either parameter would require major, structural changes. Further, current battery module designs may not adequately protect their battery cells from neighboring cell side ruptures or from exterior impacts. Moreover, existing battery modules may not protect battery cells well against convective, conductive, and/or radiation heat transfer in the case of thermal runaway. 
     Embodiments of the current disclosure disclose battery cassettes that address some of the above-described limitations. In some embodiments, the disclosed battery cassette includes a protective frame for mounting battery cells in a rigid assembly. The disclosed battery cassette may include a seal to protect battery cells from hot gases and a hard plastic frame to protect battery cells from exterior damage/impacts. In some embodiments, the disclosed battery cassette may include features that allow multiple battery cassettes to easily connect in integer numbers to create larger/smaller battery modules. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem. 
     SUMMARY 
     Embodiments of the present disclosure relate to, among other things, battery systems for electric vehicles. Each of the embodiments disclosed herein may include one or more of the features described in connection with any of the other disclosed embodiments. 
     In one embodiment, a battery cassette is disclosed. The battery cassette may include: a frame including one or more hollow tubes; and a seal component having one or more hollow tubes aligned with the hollow tubes of the frame, wherein the frame and the seal component are configured to receive one or more battery cells in the aligned hollow tubes of the frame and the seal component. 
     In another embodiment, a battery cassette is disclosed. The battery cassette may include: a frame including one or more hollow tubes; a seal component having one or more hollow tubes aligned with the hollow tubes of the frame, the hollow tubes of the frame and the seal component configured to receive one or more battery cells, wherein the battery cassette circumferentially surrounds each battery cell along substantially an entire length of each battery cell. 
     In another embodiment, a battery cassette is disclosed. The battery cassette may include: a frame including one or more hollow tubes, the frame including a first material, wherein the hollow tubes are configured to receive one or more battery cells and the frame circumferentially surrounds each battery cell along substantially an entire length of each battery cell; a seal component having one or more hollow tubes aligned with the hollow tubes of the frame, the seal component including a second material different than the first material, wherein the hollow tubes of the seal component are configured to secure the one or more battery cells in the battery cassette; a tongue located at a first end of the battery cassette, wherein the tongue is configured to mate with a corresponding groove of a different battery cassette; and a groove located at a second end of the battery cassette, wherein the groove is configured to mate with a corresponding tongue of the different battery cassette. 
     In yet another embodiment, a battery cassette is disclosed. The battery cassette may include: a frame configured to support a plurality of similarly oriented cylindrical battery cells therein, wherein an external surface of the frame includes, (a) one or more first mating features configured to engage with corresponding mating features on the frame of a second battery cassette to removably couple the battery cassette to the second battery cassette, and (b) one or more second mating features configured to engage with corresponding mating features on an electrically conductive plate that is configured to electrically couple the battery cassette to the second battery cassette. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the present disclosure and together with the description, serve to explain the principles of the disclosure. Each of the embodiments disclosed herein may include one or more of the features described in connection with any of the other disclosed embodiments. 
         FIG.  1 A  is a perspective view of an exemplary battery block having battery cassettes according to some embodiments of the present disclosure. 
         FIG.  1 B  is an exploded view of the battery block of  FIG.  1 A . 
         FIG.  2 A  is a perspective view of a single battery cassette isolated from the battery block of  FIG.  1   . 
         FIG.  2 B  is an exploded view of the battery cassette of  FIG.  2 A . 
         FIGS.  3 A- 3 F  are different views of the battery cassette of  FIG.  2 A . 
         FIG.  4 A  is a cross-sectional view of a single tube of the battery cassette along line  4 - 4  in  FIG.  3 A . 
         FIG.  4 B  is an enlarged detailed view of a section of the battery cassette along line  4 B of  FIG.  4 A . 
         FIGS.  5 A- 5 B  are different enlarged views of the battery cassette of  FIG.  2 A . 
         FIG.  6 A  is a perspective view of the battery cassette of  FIG.  2 A  with battery cells mounted therein. 
         FIG.  6 B  is a bottom side view of the battery cassette of  FIG.  6 A . 
         FIGS.  7 A- 7 C  pictorially illustrate the method of assembling a battery block by building up an array of battery cassettes. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure describes the battery cassette for a battery system of an electric vehicle. While principles of the current disclosure are described with reference to a battery cassette of an electric vehicle, it should be understood that the disclosure is not limited thereto. Rather, the battery cassettes of the present disclosure may be used in any application (electric machine, electric tool, electric appliance, etc.). In this disclosure, relative terms, such as “about,” “substantially,” “slightly,” or “approximately” are used to indicate a possible variation of ±10% in the stated value. Any implementation described herein as exemplary is not to be construed as preferred or advantageous over other implementations. Rather, the term “exemplary” is used in the sense of example or illustrative. 
       FIGS.  1 A and  1 B  illustrate an exemplary battery block  102  having cassettes  202  (“cassette  202 ”) according to one embodiment of the present disclosure.  FIG.  1 A  shows a perspective view of battery block  102 , and  FIG.  1 B  shows an exploded view. In the discussion that follows, reference will be made to both  FIGS.  1 A and  1 B . Battery block  102  may include multiple cassettes  202  (e.g., removably coupled) together. Each cassette  202  may include a plurality of battery cells mounted therein. Battery block  102  may form a part of a battery system used in, for example, an electric bus. Although an electric bus is referred to herein, battery block  102  (and cassette  202 ) may be included in any electric vehicle, energy storage device, or another application. In some embodiments, one or more battery blocks  102  may form a battery module of the battery system. Multiple battery modules (each including one or more battery blocks  102  with multiple cassettes  202  coupled together) may form a battery pack. The battery system (of the electric bus or other application) may include multiple battery packs electrically connected together to provide power. The multiple battery cells of battery block  102  may be electrically connected together in parallel and/or in series. In some embodiments, the battery cells of one or more cassettes  202  (of block  102 ) may be electrically connected together in parallel to form a parallel-connected set (or brick) of battery cassettes. Battery block  102  may include multiple such parallel-connected sets of battery cassettes. The multiple parallel-connected sets may be electrically connected together in series to form battery block  102 . The battery cells may be rechargeable cylindrical battery cells having any chemistry (lithium-ion, nickel cadmium, etc.). As would be recognized by persons skilled in the art, packaging of cylindrical battery cells include unique challenges that are not present in packaging other configurations (e.g., prismatic, pouch-type, etc.) battery cells. 
     Battery block  102  includes a positive exterior conductive plate (ECP)  104 , a negative ECP  106 , one or more pairs of spanner ECPs  108 A,  108 B, a cassette array  110  including one or more cassettes  202  containing battery cells, one or more positive conductive foils  112 , and one or more negative conductive foils  114 . As can be seen in  FIG.  1 B , the positive and negative conductive plates  104 ,  106  may be a C-shaped component that includes an end surface that contacts an end surface of the cassette array  110  and side surfaces (e.g., wedge-shaped surfaces in  FIG.  1 B ) that contact a portion of the side surfaces of the array  110 . In some embodiments, the positive and negative conductive plates  104 ,  106  may be substantially similarly (or identically) shaped. The spanner ECPs  108 A,  108 B may also be identically shaped and may contact portions of the side surface of cassette array  110 . In some embodiments, the positive and negative conductive foils  112 ,  114  may be used to electrically connect the battery cells of the one or more cassettes  202  that form a parallel-connected set in parallel. And, the electrically conductive plates may be used to connect the parallel-connected sets in series. It is understood that the positive ECP  104 , negative ECP  106 , and spanner ECPs  108 A,  108 B may include any shape, size, and/or number of components as desired. 
     As indicated in  FIG.  1 B , a pair of each spanner ECPs  108 A,  108 B may be positioned on opposite side surfaces of the battery block  102 . In the context of the current disclosure and for ease of explanation, the positive exterior collective plate (ECP)  104 , negative ECP  106 , and the one or more pairs of spanner ECPs  108 A,  108 B will be collectively referred to as the “exterior collector plates” or ECPs. ECPs may, in general, be made of any electrically conductive material, such as, for example, aluminum. As will be described later with reference to  FIGS.  5 A- 5 B , cassettes  202  of block  102  may include features that engage with corresponding features (slots, etc.) of the ECPs to attach the ECPs to the block  102 . Cassettes  202  may also include features that engage with corresponding features of positive and negative electrically conductive foils  112 ,  114  to attach these foils  112 ,  114  to the block  102 . As will be described in more detail later, the ECPs connect groups of parallel-connected cassettes  202  of the cassette array  110  electrically in series. 
       FIGS.  2 A and  2 B  illustrate an exemplary cassette  202  isolated from the battery block  102 .  FIG.  2 A  shows a perspective view of the cassette  202 , and  FIG.  2 B  shows an exploded view. Although not a requirement, as evident from these figures, in some embodiments, cassette  202  may be shaped generally like a rectangular prism. Cassette  202  may include a top end  10  and a bottom end  12  opposite the top end  10 . Bottom end  12  may be substantially parallel with top end  10 . Cassette  202  may also include a first side  14 , a second side  16  opposite first side  14 , a third side  18 , and a fourth side  20  opposite third side  18 . First, second, third, and fourth sides  14 ,  16 ,  18 ,  20  may be substantially orthogonal (e.g., perpendicular) to both the top end  10  and bottom end  12  and may each extend between top end  10  and bottom end  12 . First and second sides  14 ,  16  may be substantially parallel to other, but substantially orthogonal to third and fourth sides  18 ,  20 . Similarly, third and fourth sides  18 ,  20  may be substantially parallel to each other, but substantially orthogonal to first and second sides  14 ,  16 . Cassette  202  may include a length L, a width W, and a height H. 
     As shown in  FIGS.  2 A and  2 B , cassette  202  may include a rigid frame  204  and a seal component  206 . Frame  204  may include a generally rectangular (or rectangular prism) shape having one or more hollow tubes  208 . It is noted that only one tube  208  is labelled in  FIGS.  2 A and  2 B  for clarity. The one or more tubes  208  may include a generally cylindrical shape and may generally correspond to the external shape of battery cells  300  that are positioned in tubes  208 , as detailed below with reference to  FIGS.  6 A and  6 B . An outer surface of the tubes  208  may form first and second side  14 ,  16  walls  209 A,  209 B of frame  204 . Frame  204  may also include third and fourth side  18 ,  20  walls  209 C,  209 D. As shown in  FIG.  2 B , in some embodiments, the third and fourth side  18 ,  20  walls  209 C,  209 D may include a height H greater than a height of the tubes  208 . For example, the third and fourth side  18 ,  20  walls  209 C,  209 D may extend beyond a top end  10  and/or a bottom end  12  of tubes  208 . Accordingly, seal component  206  may be mounted on a top end  10  of tubes  208  such that a top end  10  of seal component  206  is flush with a top end  10  of third and fourth side  18 ,  20  walls  209 C,  209 D. Frame  204  may also include one or more ribs  211  for providing additional structural support. For example, ribs  211  may enable a reduction in material and weight of frame  204  (and thus, cassette  202 ), while maintaining structural integrity of frame  204 . Any number of ribs  211  may be included on frame  204  and the ribs  211  may be located at any position on frame  204 . 
     In some embodiments, frame  204  may include one or more plastic materials. The material of frame  204  may include, for example, thermoset plastics, thermoplastics, crystalline plastics, glass filled plastics, amorphous plastics, non-lubricated plastics, and/or any combination thereof. In one embodiment, the material of frame  204  may include glass-filled (GF), flame retardant (FR), non-conductive plastic. For example, frame  204  may include a crystalline plastic including glass fibers and metal hydroxides. Accordingly, the material of frame  204  may maintain its form when exposed to high temperatures (e.g., when a battery cell  300  positioned in frame  204  experiences a thermal event or rupture). In some embodiments, the frame  204  may be made of one or more amorphous or semi-crystalline thermoplastic materials (e.g., polyamide, polyphenylene oxide, polybutylene terephthalate, etc.). In some embodiments, the frame  204  may be made of a blend of multiple thermoplastic materials. The material makeup of frame  204  preferably includes low density, medium-high stiffness, high temperature, dimensionally accurate/stable, and/or medium-high surface energy materials. It is understood that frame  204  may include any material as desired, such as, but not limited to, metals, composites, fibers, ceramics, or any other material. In some embodiments, frame  204  may be opaque (e.g., black) to minimize or prevent radiant (e.g., infrared) heat transfer. For example, frame  204  may include a colored resin, such as a black resin, to help reduce radiation heat transfer between the battery cells and neighboring cells. However, it is understood that frame  204  may also be substantially clear (e.g., transparent) and/or may include any gradient of opaqueness and/or any color. As will be described below, frame  204  may include features, such as one or more apertures  210 A,  210 B, that engage with corresponding features (e.g., flanges  214 A,  214 B) of seal component  206  to attach the seal component  206  to frame  204 . 
     Seal component  206  may include a shape generally corresponding to the shape of frame  204 . For example, seal component  206  may include a generally rectangular shape. Seal component  206  may include one or more hollow tubes  212  that may include a shape generally corresponding to the shape of tubes  208  of frame  204 . It is noted that only one tube  212  is labelled in  FIGS.  2 A and  2 B  for clarity. Tubes  212  may include, for example, a generally cylindrical shape for receiving battery cells  300 , as detailed below. An outer surface of the tubes  212  may form first and second side  14 ,  16  walls  213 A,  213 B of seal component  206 . Seal component  206  may also include third and fourth side  18 ,  20  walls  213 C,  213 D. Seal component  206  may be mounted on the top end  10  of tubes  208  such that the top end  10  of seal component  206  is flush with a top end  10  of third and fourth side  18 ,  20  walls  209 C,  209 D. Further, when seal component  206  is mounted on frame  204 , first and second side  18 ,  20  walls  213 A,  213 B of seal component  206  may be flush with first and second side  18 ,  20  walls  209 A,  209 B of frame  204 . 
     Seal component  206  may also include one or more features, such as flanges  214 A,  214 B that engage with the one or more apertures  210 A,  210 B of frame  204 . The flanges  214 A and apertures  210 A may be located on the first and second sides  14 ,  16  of cassette  202  (e.g., first and second side  14 ,  16  walls  213 A,  213 B of seal component  206 ). Flanges  214 B and apertures  210 B may be located on the third and fourth sides  18 ,  20  of cassette  202  (e.g., third and fourth side  18 ,  20  walls  213 C,  213 D of seal component  206 ). Further, flanges  214 A may include one or more cutouts  216  for engaging with one or more protrusions  218  of frame  204 . The protrusions  218  may extend from frame  204  at a location adjacent to the one or more apertures  210 A. Accordingly, flanges  214 A and cutouts  216  may engage with apertures  210 A and protrusions  218 , and flanges  214 B may engage with apertures  210 B to mount seal component  206  to frame  204 . 
     Seal component  206  may include any compliant material. In one embodiment, the material of seal component  206  may be different than the material of frame  204 . However, it is understood that the material of seal component  206  may be the same as the material of frame  204 . In some embodiments, seal component  206  may include one or more materials, such as elastomers, that can maintain structural integrity in high temperatures and include a low density. In some embodiments, the material of seal component  206  may include, for example, rubbers, thermoplastic elastomers, thermoplastic copolyesters, or any other elastomer material, and/or combinations thereof. In some embodiments, seal component  206  may include liquid silicone rubber, thermoplastic copolyesters (TPE-C), and/or another high temperature elastomer. Such materials may help to prevent, or reduce, convective heat transfer between the battery cells and seal component  206 . Seal component  206  may further include flame retardant materials, such as metal hydroxides or the like. The material used for seal component  206  may have any density (and other material properties). In some embodiments, the density of the material of seal component  206  may be in the range of 0.8 g/cm 3  to 2.00 g/cm 3 , for example, 1.21 g/cm 3 . However, as explained above, in general, the material of seal component  206  may have any density as desired. The material of seal component  206  may include materials that include high temperature resistance, amorphous, thermoset, low density materials. For example, the material of seal component  206  may maintain structural integrity when exposed to temperatures of at least 200 degrees Celsius or greater. In some embodiments, seal component  206  may be opaque for prevention of radiation (e.g., infrared) heat transfer. For example, seal component  206  may include a colored resin, such as a black resin, to help reduce radiation heat transfer between the battery cells and seal component  206 . However, it is understood that seal component  206  may also be substantially clear (e.g., transparent) and/or may include any gradient of opaqueness and/or any color. 
     Cassette  202  may be manufactured or formed through molding, casting, machining, joining, or any other manufacturing process (e.g., 3D printing). Frame  204  may be manufactured by, for example, injection molding, or the like. Further, seal component  206  may be manufactured by injection molding, compression molding, or the like. In some embodiments, frame  204  and seal component  206  may be formed by overmolding. As used herein, overmolding is a process in which a single part (e.g., cassette  202 ) is created using two or more different materials in combination. Overmolding may include a first material, such as the material of frame  204 , being partially or fully covered by a second material, such as the material of seal component  206  during the manufacturing process. Accordingly, overmolding may enable seal component  206  to bond to frame  204 . Additionally, or alternatively, an adhesive bond, such as epoxy or the like, may be used to bond seal component  206  to frame  204 . Thus, cassette  202  may include a two-piece construction (e.g., frame  204  and seal component  206 ) for securing battery cells  300 , as detailed further below. In some embodiments, frame  204  and seal component  206  may be manufactured together as a single component such that cassette  202  includes a single component. 
     The side walls  209 A,  209 B,  209 C,  209 D of frame  204  and the side walls  213 A,  213 B,  213 C,  213 D of seal component  206  may define the length L, height H, and width W of cassette  202 . For example, a length of side walls  209 A,  209 B including a length of side walls  209 C,  209 D may define the overall length L of cassette  202 . The length L is defined by the number of tubes  208 ,  212  included on cassette  202 . Further, a height and width of side walls  209 C,  209 D may define the overall height H and width W of cassette  202 , respectively. The dimensions (L×H×W) of cassette  202  may correspond to an overall size of the battery modules and may be chosen accordingly. In one embodiment, the length L may be 145.65 mm (5.73 in), the height H may be 73.25 mm (2.88 in), including protrusions  502 B, or 69.75 mm (2.746 in) when protrusions  502 B are not included, and the width W may be 40.7 mm (1.602 in). However, the dimensions of cassette  202  may include a range of dimensions. For example, the length L may be in a range from 21.5 mm (0.846 in) to 1000 mm (39.370 in). The height H may be in a range from 11 mm (0.433 in) to a total height of battery cells  300 , for example, 69.75 mm (2.746 in). The width W may be in a range from 21.5 mm (0.846 in) (e.g., when only a single row  220 A of tubes  208 ,  212  is included) to 1000 mm (39.370 in). Further, an overall weight of cassette  202  may be 0.097 kg (0.214 lbs). However, the weight of cassette  202  may be in a range from 0.04 kg (0.0881 lbs) to 0.3 kg (0.661 lbs). It is understood that cassette  202  may include any size, dimensions, and/or weight, as desired. 
       FIG.  3 A  is a top end  10  view of an exemplary embodiment of cassette  202  of  FIG.  2 A .  FIG.  3 B  is a bottom end  12  view of the exemplary cassette  202  of  FIG.  2 A . As shown in  FIGS.  3 A and  3 B , in some embodiments, cassette  202  may include twelve hollow tubes  208 ,  212 . For example, frame  204  may include twelve tubes  208  and seal component  206  may include twelve tubes  212 , accordingly. The tubes  208 ,  212  may be aligned in one or more rows. For example, cassette  202  may include a first row  220 A and a second row  220 B of tubes  208 ,  212 . Each row  220 A,  220 B may include six tubes  208 ,  212 . The rows  220 A,  220 B may be offset such that the tubes  208 ,  212  of the adjacent rows  220 A,  220 B are not aligned perpendicularly. Accordingly, the tubes  208 ,  212  may be tightly nested to enable a greater number of tubes  208 ,  212  while minimizing an overall size of cassette  202 . It is understood that cassette  202  may include any number of tubes  208 ,  212  and any number of rows  220 A,  220 B as desired. Further, frame  204  may include a thickness t 1  between tubes  208 . The thickness t 1  between tubes  208  of frame  204  may be defined by a distance between tubes  208 . In one embodiment, the thickness t 1  may be less than 1 mm (0.0394 in), and preferably may be 0.80 mm (0.0315 in). As detailed below, an inner diameter of tubes  208  may taper from the top end  10  to the bottom end  12 . Accordingly, the thickness t 1  between tubes  208  may vary from the top end  10  to the bottom end  12 . Thus, the thickness t 1  may be in a range from 0.25 mm (0.00984 in) at the top end  10  to 0.8 mm (0.0315 in) at the bottom end  12 . 
       FIG.  4 A  is a cross-sectional view of a single tube  208 ,  212  along line  4 - 4  of the cassette  202  of  FIG.  3 A .  FIG.  4 B  is a detailed view of the circled portion of the single tube  208 ,  212  of  FIG.  4 A . As shown in  FIGS.  4 A and  4 B , tube  208  of frame  212  may include a varying inner diameter. For example, tube  208  may include a first diameter d 1  and a second diameter d 2 . In some embodiments, diameter d 1  may be greater than the diameter d 2 . In some embodiments, the inner diameter of tube  208  of frame  204  may taper from the top end  10  (e.g., from diameter d 2 ) to the bottom end  12  (e.g., diameter d 1 ) along a length of tube  208  such that the inner diameter of tube  208  varies from the top end  10  towards the bottom end  12 . Diameter d 2  may be slightly larger than, slightly smaller than, or substantially equal to, a diameter d 5  of battery cells  300 , as detailed further below. In one embodiment, diameter dl may be 21.46 mm (0.845 in) and diameter d 2  may be 21 mm (0.827 in). It is understood that diameter dl and diameter d 2  may be any size and/or dimension as desired. 
     Tube  212  of seal component  202  may include a third inner diameter d 3 . Diameter d 3  may be the same, or substantially similar, to diameter d 2  of tube  208 . For example, diameter d 3  may be 21 mm (0.827 in). In some embodiments, the inner diameter of tube  212  may be substantially constant along a length of tube  212 . However, in some embodiments, the inner diameter of tube  212  may taper along the length of tube  212 . As best seen in  FIG.  4 B , tube  212  of seal component  206  may include a circumferential lip or protrusion  222  that protrudes from a sidewall of the tube  212  into the tube cavity. The protrusion  222  may extend around an inner circumference of tube  212  such that the protrusion  222  is internal of seal component  206 . Protrusion  222  may extend radially in from a radially inner wall of tube  212  such that tube  212  may include a fourth inner diameter d 4 . Diameter d 4  may be less than diameter d 3  and/or diameter d 2 . In one embodiment, diameter d 4  may be 20.1 mm (0.791 in). The protrusion  222  may correspond to a groove  302  (shown in  FIG.  7 A ) on the cylindrical sidewall of battery cell  300  such that the groove  302  of battery cell  300  receives protrusion  222  when battery cell  300  is mounted in tubes  208 ,  212 , as detailed further below. In some embodiments, tubes  212  of seal component  206  may include a circumferential lip or protrusion (not shown) at the top end  10  (e.g., located longitudinally above protrusion  222 ) to thermally and electrically insulate a shoulder of battery cell  300 , while also providing a location stop during battery cell  300  installation. For example, the circumferential lip of each tube  212  may be at, or adjacent, a top end  10  surface of seal component  206  and may extend radially in from the radially inner wall of tube  212 . Accordingly, the circumferential lip may radially cover a portion of battery cell  300 . The circumferential lip at the top end  10  may enable use of unwrapped cylindrical battery cells  300  by provided additional thermal and electrical insulation. 
       FIG.  6 A  shows a perspective view of cassette  202  with battery cells  300  mounted therein.  FIG.  6 B  shows a bottom end  12  view of the cassette  202  with a detailed view of the battery cells  300  mounted therein. As shown in  FIG.  6 B , battery cells  300  may include an outer diameter d 5 . Diameter d 5  may be smaller than diameter d 1  and diameter d 2  and may be larger than diameter d 3  and diameter d 4 . Accordingly, battery cells  300  can be inserted into cassette  202 , as detailed below with respect to  FIG.  5 A . In one embodiment, diameter d 5  may be, for example, 21.1 mm (0.831 in). It is understood that any type of battery cell  300  may be used that includes any size, shape, and/or voltage as desired. In some embodiments, the maximum diameter of the battery cell  300  may be slightly larger than the inner diameter of the plastic tube at the top end (d 3 ), e.g., if the tolerances of the parts stack worst case. However, typically, the maximum diameter of the battery cell  300  is slightly smaller than the inner diameter of the plastic tube at the top end. 
     Each battery cell  300  includes a current interrupt device (CID) positioned inside its casing proximate its positive terminal. The CID is typically employed to provide protection against any excessive internal pressure increase in the battery cell by interrupting the current path from the battery cell when pressure inside its casing is greater than a predetermined value. The CID typically includes first and second conductive plates in electrical communication with each other. The first and second conductive plates are, in turn, in electrical communication with an electrode and a terminal of the battery cell, respectively. The second conductive plate separates from (e.g., deforms away or is detached from) the first conductive plate of the CID when pressure inside the battery is greater than a predetermined value, whereby a current flow between the electrode and the terminal is interrupted. The gap between the first and second conductive plates also allows the high pressure gases from inside the casing of the battery cell to vent or escape to the outside. In some cases, the first and second conductive plates of the CID are formed of different materials that expand differently when heated to cause the two plates to separate from each other. For example, when the temperature of the battery cell exceeds a threshold (for example, due to a defect in the battery cell), the bi-metallic conductive plates of the CID deflects or bends (e.g., due to different thermal expansions of the materials of the bi-metallic disc) and cuts the battery cell off from the circuit. 
     When mounted in cassette  202 , battery cells  300  may be flush with the top end  10  of seal component  206  at a positive terminal  300 A end of battery cell  300 . Frame  204  may circumferentially surround each battery cell  300 . Further, battery cell  300  may extend beyond the bottom end  12  of frame  204  at a negative terminal  300 B end of battery cell  300 . As such, cassette  202  may circumferentially surround each battery cell  300  along substantially an entire length of each battery cell  300 . The groove  302  ( FIG.  7 A ) of battery cells  300  may receive protrusion  222  of seal component  206  such that seal component  206  may secure battery cells  300  in cassette  202 . Further, battery cells  300  may be secured in cassette  202  by an interference fit with tubes  212  of seal component  202  due to outer diameter d 5  of battery cells  300  being smaller than inner diameter d 3  of tube  212 . The seal component  206  also allows the cells  300  to vent via their CID proximate the positive charge end  300 A. 
     As further shown in  FIG.  6 B , a circumferential gap  224  may be formed between battery cell  300  and tube  208  of frame  204  when battery cells  300  are mounted in cassette  202 . The circumferential gap  224  may be formed due to outer diameter d 5  of battery cells  300  being smaller than inner diameter d 1  of tubes  208 . Accordingly, due to the difference between outer diameter d 5  and inner diameter d 1 , battery cells  300  may be inserted into cassette  202  from the bottom end  12  of cassette  202 . The circumferential gap  224  may also allow a column of air between frame  204  and cells  300  to help prevent conductive heat transfer between the cells  300  and frame  204 . 
       FIG.  3 C  is a first side  14  view of cassette  202 ,  FIG.  3 D  is a second side  16  view of cassette  202 ,  FIG.  3 E  is a third side  18  view of cassette  202 , and  FIG.  3 F  is a fourth side  20  view of cassette  202 . As shown in  FIGS.  3 C- 3 F , cassette  202  may include one or more mating features, such as a tongue  402 A,  402 B and groove  404 A,  404 B configuration, for mating multiple cassettes  202  together, as detailed further below with respect to  FIGS.  7 A- 7 C . For example, first side  14  of cassette  202  may include a first tongue  402 A and a first groove  404 A located on frame  204 . Tongue  402 A may be located at a first end (e.g., at third side  18 ) of frame  204  and groove  404 A may be located at a second opposite end (e.g., at fourth side  20 ) of frame  204  on the first side  14 . Second side  16  of cassette  202  may include a second tongue  402 B and a second groove  404 B located on frame  204 . Tongue  402 B may be located at the second end (e.g., at fourth side  20 ) of frame  204  and groove  404 B may be located at the first end (e.g., at third side  18 ) of frame  204  on the second side  16 . 
     As shown in  FIGS.  3 C and  3 D , tongues  402 A,  402 B and grooves  404 A,  404 B may extend substantially an entire height H of cassette  202  (e.g., frame  204  of cassette  202 ). Tongue  402 A may include a shape corresponding to a shape of groove  404 B such that tongue  402 A may be fitted (e.g., slid) into groove  404 B of another cassette  202 . Likewise, tongue  402 B may include a shape corresponding to a shape of groove  404 A such that tongue  402 B may be fitted (e.g., slid) into groove  404 A of another cassette  202 . 
     Tongues  402 A,  402 B and grooves  404 A,  404 B may be oriented such that tongues  402 A,  402 B may slide (e.g., mate) into grooves  404 A,  404 B. For example, tongue  402 A may be oriented in a first direction and groove  404 B may be oriented in the first direction such that the bottom end  12  of tongue  402 A may slide into the top end  10  of groove  404 B. Likewise, tongue  402 B may be oriented in a second direction and groove  404 A may be oriented in the second direction such that the top end  10  of tongue  402 B may slide into the bottom end  12  of groove  404 A. Accordingly, tongue  402 A and groove  404 A of cassette  202  may slide onto and mate with tongue  402 B and groove  404 B of an adjacent cassette  202  to removably couple the two cassettes together. 
     As shown in  FIGS.  3 A- 3 D , cassette  202  may also include mating and datum features  405  at an end of the tongue  402 A,  402 B and groove  404 A,  404 B features to control tolerance stack of the block  102 . For example, the datum features  405 A,  405 B may include 2-way datum and/or a 4-way datum. As used herein, a 2-way datum is a datum feature  405  that restricts movement along one (1) axis (i.e., in two directions along one axis). Further, a 4-way datum is a datum feature  405  that restricts movement along two (2) axes. The datum features  405  may include, for example, a pin  405 A and a corresponding hole  405 B for receiving the pin  405 A. The hole  405 B may include a shape corresponding to a shape of the pin  405 A. For example, the pin  405 A may include a generally cylindrical shape and the hole  405 B may include a generally circular shape. The pins  405 A may be located on tongues  402 A,  402 B, respectively, and the holes  405 B may be located in grooves  404 A,  404 B, respectively. 
     As further shown in  FIGS.  3 C- 3 F , cassette  202  may also include one or more snap-fit features for locking cassettes  202  together after two cassettes  202  have been mated. The snap-fit features may include a male snap components  406 A and female snap components  406 B. Male snap components  406 A may include one or more protrusions that correspond to a snap-in area of the female snap components  406 B. Accordingly, the female snap components  406 B may receive the male snap components  406 A and lock, or restrict, the male snap components  406 A in place. The snap features may also include a lever  408 , or pin, for undoing the snap-fit of the male and female snap components  406 A,  406 B. For example, the lever  408  may be pushed such that the male component  406 A is no longer restricted by the female component  406 B. When the lever  408  is pushed, the male component  406 A may be moved beyond the female component  406 B to undo the snap-fit. While the exemplary embodiments of the mating features described herein include tongue and groove and snap-fit features, it is understood that the mating features may include any type of mating feature for mating two or more components together. For example, the mating features may include one or more fasteners (e.g., bolts, screws, etc.), adhesive, or the like. Further, the mating features may be located on any side  10 ,  12 ,  14 ,  16 ,  28 ,  20  of cassette  202  and in any location, and may include any number and/or combination of mating features. 
       FIG.  5 A  shows an enlarged perspective view of a portion of the top end  10  of cassette  202 .  FIG.  5 B  shows an enlarged perspective view of a portion of the bottom end  12  of cassette  202 . With reference to  FIGS.  2 A- 2 B,  3 A- 3 F, and  5 A- 5 B , cassette  202  may further include features to attach to the positive and negative conductive foils and/or the ECPs to form block  102 . In some embodiments, the features may include keying, alignment and locking features  502 A,  502 B,  502 C, etc. on the frame  204  of cassette  202  that engage with corresponding features (slots, etc.) on ECPs and/or the foils to couple the ECPs and/or the foils to the cassette array. For example, features  502 A and  502 B may include protrusions, or pins, on cassette  202  (e.g., on frame  204  of cassette  202 ) that may engage with (or fit into) slots or cavities in the ECPs and/or the foils to couple the ECPs and/or the foils to the cassette array. These protrusions and slots may be configured or shaped such that the ECPs and/or the foils are oriented in the desired manner on cassette array. Further, features  502 C may include a snap-fit feature that includes a male component for engaging with a corresponding slot of the ECPs and/or foils. Accordingly, the ECPs and/or foils may be secured to the cassette array  110 . 
     In one embodiment, protrusions  502 A and snap feature  502 C may be located on the third side  18  and fourth side  20  of frame  204 . For example, each side  18 ,  20  may include two (2) protrusions  502 A and two (2) snaps  502 C. A first protrusion  502 A and a first snap  502 C may be located at a top end  10  of each side  18 ,  20  and a second protrusion  502 A and a second snap  502 C may be located at a bottom end  12  of each side  18 ,  20 . Further, protrusions  502 B may be located on a top end  10  and a bottom end  12  of frame  204 . For example, a first protrusion  502 B and a second protrusion  502 B may be located on top and bottom ends  10 ,  12 , respectively, at third side  18 . Likewise, a third protrusion  502 B and fourth protrusion  502 B may be located on top and bottom ends  10 ,  12 , respectively, at fourth side  20 . It is understood that cassette  202  may include any number and arrangement of features  502 A- 502 C and features  502 A- 502 C may be located at any location on frame  204  and/or seal component  206 . 
       FIGS.  7 A- 7 C  depict the assembly of the exemplary battery cassette array  110  of block  102  (see  FIG.  1 B ) according to some embodiments. As noted above, battery cassette array  110  may include one or more battery cassettes  202  coupled together.  FIG.  7 A  depicts a plurality of battery cells  300  being inserted into the exemplary cassette  202 . For example, the battery cells  300  may be inserted into tubes  208 ,  212  from the bottom end  12  of cassette  202 . When inserted and mounted, the battery cells  300  are oriented such that the positive terminal  300 A of each battery cell  300  is aligned in the same direction. Accordingly, the negative terminal  300 B of the battery cells  300  are also aligned in the same direction. The aligned battery cells  300  are then inserted into cassette  202  (e.g., frame  204  of cassette  202 ) to securely hold the battery cells  300  in place and form a cassette  202 . 
       FIG.  7 B  shows two cassettes  202 A,  202 B being coupled together, according to an embodiment of the present disclosure. As shown in  FIGS.  2 A- 2 B and  7 B , the exterior surface of the cassettes  202 A,  202 B are contoured, or include features, to enable one cassette  202 A to mate, engage, and couple with (e.g., removably couple with) another cassette  202 B. For example, the exterior surface of the frame  204  and seal component  206  of one cassette  202 A may include grooves, or other features, that correspond with features on the exterior surface of frame  204  and seal component  206  of a second cassette  202 B. These mating features allow the two cassettes  202 A,  202 B to align and couple with each other such that a battery block  102  (see  FIG.  7 C ) is formed with the battery cells  300  in the cassettes  202  oriented and aligned as desired. In some embodiments, the cassettes  202 A,  202 B slide together in the tongue  402 A,  402 B and groove  404 A,  404 B configuration with snap-fit final engagement, as detailed above. For example, tongue  402 A of cassette  202 B may be slid into groove  404 B of cassette  202 A. Likewise, groove  404 A of cassette  202 B may be slid into tongue  402 B of cassette  202 A. The cassettes  202 A,  202 B are removably coupled to each other such that they can be coupled to each other and separated from each other using their mating engagement features. Multiple cassettes  202  are joined together in a similar manner to form battery cassette array  110 , as shown in  FIG.  7 C . In the embodiment illustrated in  FIG.  7 C , ten (10) cassettes  202 , with twelve (12) battery cells  300  each, are joined together to form cassette array  110 . However, this is only exemplary. In general, a cassette  202  may support any number of battery cells  300 , and any number of cassettes  202  may be coupled together (as described above) to form blocks  102  with different energy capacities. Adding additional cassettes  202  to array  110  increases the energy capacity of the cassette array  110 . The voltage output (and consequently the current output) of a cassette array  110  can also be varied independent of its energy capacity by changing the number of cassettes  202  that are connected together in parallel, and the number of parallel-connected cassettes  202  connected together in series. 
     As can be seen in  FIG.  7 C , the positive terminal  300 A of each battery cell  300  of block  110  is oriented in the same direction thus enabling the opposite negative terminal  300 B (not seen in  FIG.  7 C ) of the cells  300  to contact a cooling plate (not shown). The ability to easily add on multiple cassettes  202  to form battery cassette array  110  (and add additional cassettes  202  to the array  110  to extend the block  102 ) enables the energy and voltage of a battery module (formed from block  102 ) to be scaled in a flexible manner. After the cassette array  110  with the desired number of cassettes  202  is formed, a block  102  (see  FIG.  1 A and  1 B ) may be formed by assembling the positive and negative conductive foils  112 ,  114  and the ECPs  104 ,  106 ,  108 A,  108 B, etc. with the cassette array  110 . The number of ECPs, specifically the number of inner spanner ECPs  108 A,  108 B, etc. may be adjusted according to the number of cassettes  202  included in the battery block  110  and the desired energy and voltage. 
     As shown in the embodiments above, the voltage and energy provided by the battery blocks  110  may be independently scaled as desired. For example, the voltage provided by the battery block  110  shown in  FIG.  1 A  may be scaled from 12V to 36V simply by providing a different configuration for ECPs (and foils). Further, the positive and negative foils may be provided based on the configuration of ECPs. As is well known, more battery cells indicate more energy. As such, if a certain voltage is required, yet a high level of energy is not necessary, several cassettes  202  may be removed from the battery block  110 . In such instances, the appropriate exterior collector plates, in addition to the appropriate positive and negative foils, may be applied to the obtained battery cassette array  110  for required voltage at the desired energy level. Thus, with the described architecture, the battery modules and battery packs are both scalable in voltage and energy independently. Being able to scale at both levels (voltage and energy) allows for the battery pack size to be tailored to the application and available space in the chassis for mounting batteries. 
     The ability to scale the battery pack and battery module independently for energy and voltage allows for the pack size to be more easily tailored to the application and available space in the chassis for mounting batteries. For example, while a heavy duty vehicle (such as a bus) may need a battery pack with a low output voltage relative to the energy storage needs (to provide the required range), a lighter vehicle (e.g., a light truck, car, etc.) may need a battery pack with a higher output voltage relative to the energy storage needs to meet the required range. The disclosed cassette  202  can enable these different applications by sub-dividing the battery module (using different ECPs and foils) into different number and size of bricks (i.e., the number of cassettes  202  that are connected together in parallel) to provide the needed voltage. The ability to easily reconfigure a battery pack for different applications using the same base building blocks increases operational and engineering efficiency while reducing time to market and saving money on validation and capital equipment costs. 
     Further, the cassette  202  of the present disclosure may enable the battery cells  300  to be safely packaged together. For example, the tubes  208  of frame  204  may provide separation between adjacent battery cells  300 . Accordingly, if a battery cell  300  experiences a thermal runaway event, ruptures, or otherwise fails, frame  204  may provide protection to the other battery cells  300  to help prevent the damage from spreading and causing other battery cells  300  in the cassette  202  from failing. The tubes  208  of frame  204  may provide separation between adjacent battery cells  300 . The materials, colors, and design of frame  204  and seal component  206  may also help prevent, or otherwise reduce, conductive, convective, and/or radiation heat transfer. For example, the gap  222  between tubes  208  of frame  204  and the battery cells  300  may allow a thermally-insulating column of air for preventing or reducing conduction heat transfer. The seal component  206  (e.g., silicone or other elastomers) may help to prevent or reduce convective heat transfer by forming a gas-tight seal with battery cells  300 . Further, opaque materials of the frame  204  and/or the seal component  206  may help to prevent or reduce radiation heat transfer. 
     A number of features of cassette  202  may also help to reduce overall size and weight of cassette  202 . For example, ribs  211  may enable less material to be used while maintaining structural support of cassette  202 . Further, material selection (e.g., thermoplastics and elastomers) may also help to reduce weight. 
     While principles of the present disclosure are described herein with reference to an exemplary design of a cassette  202 , a person of ordinary skill in the art would readily recognize that many variations can be made to the design of the cassette  202 . For example, the cassettes of the current disclosure may support any number and type of battery cells. Any number of cassettes  202  may be coupled together to form a battery module. And, any type of mating features may be used to couple adjacent cassettes  202  together. Further, although the battery system of an electric bus is described, it should be understood that the disclosure is not limited thereto. Rather, the systems described herein may be employed in the batteries of any application. Also, those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, embodiments, and substitution of equivalents all fall within the scope of the embodiments described herein. Accordingly, the disclosure is not to be considered as limited by the foregoing description. For example, while certain features have been described in connection with various embodiments, it is to be understood that any feature described in conjunction with any embodiment disclosed herein may be used with any other embodiment disclosed herein.