Field of the Invention

The present invention relates to batteries and, particularly, to a battery module and a battery pack comprising the battery module. The battery module and the battery pack are suitable for an electric vehicle, among other uses.

Background of the Invention

Batteries are an integral part of electric vehicles. In some cases, battery packs including batteries and frames may form at least part of the structure of electric vehicles. Maintenance of electric vehicles, and in particular battery packs in electric vehicles, may be a regular occurrence and, due to the position of battery packs in electric vehicles, can be challenging. Therefore, there may be a desire to provide a practical and reliable battery pack for electric vehicles which is easily manufactured and maintained. Reducing weight of battery packs may also be a desire in the field of electric vehicles to increase performance.

Summary of the Invention

A first aspect of the present invention provides a battery pack comprising a plurality of battery modules mounted to a frame by one or more fasteners. Each battery module comprises a heat transfer member, and each heat transfer member cooperates with a heat transfer member of an adjacent battery module to at least partially define one or more apertures for receiving the fasteners. In this way, the heater transfer member may conveniently function as both a heat sink and a support, the support acting to support cell groups in a battery module and to mount the battery module in a battery pack frame. Providing a heat transfer member as part of a support may facilitate convenient insertion or removal of each battery module. Providing cooperating mounting features may reduce a number of fasteners required to secure the battery modules in the battery pack, thereby reducing cost and weight.

Each battery module having a respective heat transfer member, hereafter referred to as a cooling member, allows each battery module to be individually cooled. In other words, coolant, or cooling fluid, entering a cooling member to cool a battery module may be at the same temperature as coolant entering each other cooling member. In contrast, coolant flowing through a common cooling member may be heated and passed from one battery module to another. Thereby, a common battery pack cooling member may provide impaired cooling to each subsequent battery module in a sequence. Providing individual cooling members enables efficient cooling of each battery module. Providing multiple cooling members may provide modularity, while smaller cooling members may less cumbersome to handle and install.

Each cooling member may be a planar cooling plate. The cooling member may be elongate, such as generally rectangular. A planar cooling member may provide suitable support and efficient cooling of cell groups on either side of the cooling member whilst taking up little space in the battery pack.

Each cooling member may comprise one or more recesses at a periphery of the cooling member, and the recesses of adjacent cooling members may cooperate to at least partially define the one or more apertures. Providing mounting features, such as recesses, on a periphery of a cooling member enables the recesses to correspond with recesses on a periphery of an adjacent cooling member by aligning the cooling members side-by-side. Cooling members aligned as such may be coplanar.

Opposing sides of each cooling member may each comprise at least one recess. In this way, the cooling members can be arranged side-by-side in a battery module, and the at least one recess on one side of a cooling member may cooperate with a corresponding recess on the opposite side of an adjacent cooling member. Adjacent cooling members may define a plurality of apertures spaced along the peripheries of the cooling members. Electrical connections between adjacent battery modules may be formed intermediate pairs of apertures. For example, a single electrical connection may be formed between each pair of apertures. This may provide an efficient use of space, and may act to space apart electrical connections between adjacent battery modules thereby reducing the risk of failure in use.

Each cooling member may comprise at least one tab, and at least one recess may be formed in each tab. A tab may comprise a flat projection extending from the main body of the cooling member. The projection may be an elongate strip. Providing tabs enables a load on the cooling member to be distributed across the tab, in contrast to mounting the cooling member using point connections. The tabs and recesses may be configured such that no relative movement of adjacent cooling members is permitted when the cooling members are fastened in a battery pack frame. In this way, loads may be distributed between adjacent cooling members via cooperating tabs.

The recesses may be disposed on each cooling member such that the one or more apertures are defined for only a single orientation of adjacent cooling members. For example, there may only be a single possible alignment of adjacent cooling members in which the one or more apertures are defined. The cooling members may be asymmetric, and the cooling members may only be mounted in a battery pack in a single orientation. This provides a convenient way of ensuring battery modules are mounted in a desired orientation during manufacture of a battery pack.

Each cooling member may comprise a location feature for locating the cooling member relative to the frame. The frame may comprise a hole for receiving the one or more fasteners, and the location feature may be received in the hole. The location feature may thereby assist in seating the cooling member correctly in a frame before fastening the cooling member to the frame. The location feature may comprise a projection extending from the cooling member. The projection may be a straight or tapered projection, such as a conical or semi-conical projection. A straight or tapered projection may conveniently guide the cooling member into an appropriate position relative to a hole in a battery pack frame during manufacture. A tapered projection may conveniently direct a fastener through an aperture formed by corresponding mounting features. As such, a fastener may be inserted at an angle, leading to efficiencies during the manufacture of a battery pack.

Each cooling member may comprise a fluid inlet, a fluid outlet, and one or more flow paths for carrying fluid between the fluid inlet and the fluid outlet. The fluid inlet and fluid outlet may comprise a respective supply and return port fluidically coupled to a respective ancillary supply and return conduit. The inlet port and the outlet port may be configured to respectively receive and expel coolant, to facilitate a flow of coolant to/from a cooling system.

The cooling member may be generally hollow, and the flow paths may comprise flow channels within the cooling member. The flow paths may distribute fluid around the cooling member from a central inlet plenum which received fluid from the fluid inlet.

The cooling member may comprise opposing faces, and a first plurality of battery cells may be mounted on a first face of the cooling member and a second plurality of battery cells may be mounted on a second face of the cooling member. The battery cells may be split into cell groups, and a first plurality of cell groups may be mounted spaced apart on a first face of a cooling member, and a second plurality of cell groups may be mounted spaced apart on a second face of the cooling member. First and second channels may be formed between spaced apart cell groups on respective first and second faces.

Having battery cells, or cell groups comprising an arrangement or array of battery cells, disposed on either side of a cooling member may provide an efficient cooling arrangement. For instance, a cooling member arranged in this way may provide cooling to more cell groups than a similar cooling member arranged with cell groups on a single face.

The frame may comprise at least one lower support member, and the plurality of battery modules may be mounted to the lower support member by the one or more fasteners.

The frame may comprise at least one upper support member, and the at least one upper support member is secured to the at least one lower support member, such that the cooling member is located between the upper and lower support member. In this way, a cooling member may be clamped or gripped between upper and lower support members, thereby securely fixing a respective battery module in the frame.

Each battery module may be selectively removable from the battery pack independently of the other battery modules. This may be facilitated by the battery pack comprising a respective cooling member. Providing selectively removable battery modules permits the convenient removal or replacement of individual battery modules during maintenance or repair.

The battery pack may be an electric vehicle battery pack.

A second aspect of the present invention provides a battery module for a battery pack, the battery module comprising a cooling member, wherein the cooling member is configured to cooperate with a cooling member of another battery module in the battery pack to at least partially define one or more apertures for receiving fasteners for fastening the battery module in the battery pack. The battery module may comprise a cooling member as described hereinbefore with reference to the first aspect of the present invention.

The battery module may be an electric vehicle battery module. A third aspect of the present invention provides an electric vehicle comprising a battery pack according to the first aspect of the present invention, and/or a battery module according to the second aspect of the present invention. Brief Description of the Drawings

In order that the present invention may be more readily understood, examples of the invention will now be described, with reference to the accompanying drawings, in which: Figure l is a view of an assembled battery pack according to an example; Figure 2 is a view of an arrangement of battery modules of the battery pack of

Figure 1;

Figure 3 is a schematic view of a battery module of the battery pack of Figure 1; Figure 4 is a schematic view of the battery module of Figure 3, showing battery cells; Figure 5 is a top-down schematic view of a cell group within the battery module of Figure 4;

Figure 6 is a schematic view of current flow in the battery module of Figure 3; Figure 7 is a schematic view of current flow in the arrangement of battery modules of Figure 2; Figure 8 is a top-down schematic view of the arrangement of battery modules of

Figure 3, wherein the battery modules are connected to one another;

Figure 9 is a schematic view of magnetic fields generated in the battery pack of Figure 1;

Figure 10 is a perspective view of a cooling assembly according to an example; Figure 11 is a perspective view of cooling members in the cooling assembly of

Figure 10;

Figure 12 is a top-down schematic view of flow paths in a cooling member of Figure 11;

Figure 13 is a top-down perspective view of two adjacent cooling members of the cooling assembly of Figure 10; Figure 14 is an expanded schematic view of mounting features of the cooling members of Figure 13;

Figure 15 is a perspective view of a battery pack frame, suitable for the battery pack of Figure 1;

Figure 16 is a schematic side elevation view of an electric vehicle according to an example; and

Figure 17 is a schematic plan view of an underside of the electric vehicle of Figure

16.

Detailed Description of the Invention

Details of methods and systems according to examples will become apparent from the following description, with reference to the Figures. In this description, for the purpose of explanation, numerous specific details of an example are set forth. Reference in the specification to "the example" or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in at least that one example, but not necessarily in other examples. It should further be noted that the example illustrated in the figures is described in various different ways, and is described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the example.

In the following text, the terms “battery”, “cell” and “battery cell” may be used interchangeably and may refer to any of a variety of different battery cell types and configurations including, but not limited to, lithium ion, lithium ion polymer, nickel metal hydride, nickel cadmium, nickel hydrogen, alkaline, or other battery cell type/configuration.

An example of the invention will be described in the context of a battery module or a battery pack for an electric vehicle. A person skilled in the art will realise that the example is not limited to this purpose. For example, a battery module or a battery pack as herein described may instead be used to provide and store electrical energy for any kind of industrial, commercial, or domestic purposes, such as for energy storage and delivery, for example, in smart grids, home energy storage systems, electricity load balancing and the like.

The battery pack 10 of Figure 1 comprises an arrangement of battery modules 12a to 12h supported in a frame 50. The frame 50 holds the battery modules 12a to 12h in the arrangement. The battery pack 10 has a first dimension 25 and a second dimension 26, respectively, corresponding to a length and a width dimension of the battery pack. The first and second dimensions 25,26 may alternatively be referred to as ‘y’ and ‘x’ dimensions. A third dimension, which is also referred to herein as a ‘z’ dimension, is orthogonal to the first and second dimensions 25,26 and corresponds with a depth or height dimension of the battery pack. In the illustrated example, the first dimension 25 is also a major dimension of the battery pack 10. In other examples, the first dimension 25 may be a minor dimension of the battery pack 10, or the battery pack 10 may be equilateral. As used herein, the terms “major dimension” and “minor dimension” refer, respectively, to the longest and shortest spans or lengths of a structure. The major dimension is typically (as is the case herein), but not exclusively, perpendicular to the minor dimension.

The arrangement of battery modules 12a to 12h is also illustrated in Figure 2, while an individual battery module, for instance 12a, is also illustrated in different ways in Figures 3 and 4. Each battery module 12a to 12h according to the present example comprises a plurality of battery cells 14 arranged into four cell groups, 13a, 13b, 13c, 13d. Thatis, each battery module 12a to 12h comprises a first cell group 13a, a second cell group 13b, a third cell group 13c and a fourth cell group 13d. The cell groups 13a, 13b, 13c, 13d may instead be referred to as ‘groups of cells 13a, 13b, 13c, 13d’ or ‘groups of battery cells 13a, 13b, 13c, 13d’. The battery cells 14 that make up each cell group 13a, 13b, 13c, 13d are electrically connected in a combination of series and parallel connections, for example using busbars or other electrical connecting means. Each battery module 12a to 12h comprises a cooling member 31 having opposing first and second faces 32,33 on which the cell groups 13a, 13b, 13c, 13d are mounted. The cooling member 31 may be constructed from a rigid material to provide support for cell groups 13a, 13b, 13c, 13d that are disposed on the cooling member 31. The cooling member 31 is a planar member, with cell groups 13a, 13b, 13c, 13d mounted on both opposing faces 32,33. In the present context, the cooling member 31 may be referred to as “planar” even if the surfaces of the faces 32,33 are not entirely flat, for instance, due to accommodating one or more features which may be raised or depressed relative to an otherwise generally flat surface. In the present example, the cooling member 31 is also shown as being a generally regular, rectangular, plate-like member, comprising a major and a minor dimension, and supporting generally cuboidal cell groups 13 a, 13b, 13c, 13d. The cooling member 31 is fluid-cooled and includes internal cooling channels (not shown) to receive a flow of coolant. The coolant may be a liquid, for example water containing anti-corrosion and/or anti-freeze additives. In the context of an electric vehicle, the coolant may be circulated by a cooling system of the electric vehicle. As shown in the example of Figure 3, the cooling member 31 comprises inlet and outlet ports 34a, 34b fluidically coupled to respective ancillary supply and return conduits 35a, 35b to supply a flow of coolant. Such cooling features will be described hereinafter in more detail with reference to Figures 10 to 13. It will be understood from the following description that, in other examples, the cooling member 31 may not be fluid-cooled and may not, therefore, require coolant channels and inlet/outlet ports 34a, 34b.

Although referred to herein as a cooling member 31, it will be appreciated by a person skilled in the art that such a member may equally be utilised to heat battery cells, for example by heating coolant flowing through the cooling member in use. This may, for example, be particularly useful when it is desired to pre-condition battery cells, for example in the event of charging. Thus the cooling member 31 can be thought of more generally as a heat transfer member. The battery module 12a to 12h comprises four cell groups 13a, 13b, 13c, 13d arranged such that two cell groups 13a, 13c are mounted spaced apart on the first face 32 of the cooling member 31 and two cell groups 13b, 13d are mounted spaced apart on the second face 33 of the cooling member 31. The second cell group 13b may be thought of as being in a stacked configuration with respect to the first cell group 13a, and the fourth cell group 13d may be thought of as being in a stacked configuration with respect to the third cell group 13 c.

The individual battery cells 14 are not visible in Figures 1, 2 or 3, but are illustrated in Figure 4. In the illustrated example, the battery cells 14 are cylindrical. However, other formats of battery cell 14 are contemplated. For example, the battery cells 14 may be elongate and may have one or more of a polygonal, semi-polygonal or elliptical cross- section, for example a hexagonal or semi-cylindrical cross-section. Alternatively, the battery cells 14 may not be elongate and/or the cross-section may be some other shape. For example, the battery cells 14 may be substantially rectangular and planar, and, in that case, may be arranged in the cell group 13 in a stacked arrangement (for instance, stacked in the z-dimension), or arranged adjacent to one another in a row, such that a plane of each battery cell 14 is parallel to a plane of each other battery cell 14.

Referring again to the illustrated example, each of the battery cells 14 comprises a first end 46 and a second end 47, opposite to the first end 46. The second ends 47 of the battery cells 14 are secured, in this example, to a face of the cooling member 31, whereby the first ends 46 of the battery cells 14 are coplanar, residing in a plane that is parallel to the plane of the cooling member 31. Although not shown in detail herein, the first ends 46 of the battery cells comprise both positive 48 and negative 49 battery cell terminals. As such, the battery cell terminals 48,49 of each of the battery cells 14 are exposed on the first ends 46 of the battery cells 14, away from the cooling member 31. The battery cells 14 may be held in place relative to one another and to the cooling member 31 by an appropriate support structure (not shown). In other examples, the cell groups 13a, 13b, 13c, 13d may be mounted to the cooling member 31 by any suitable method, including but not limited to, the use of adhesive, fixing mechanisms such as clasps, clamps, braces, or any other suitable attachment mechanisms. The cooling member 31 may be formed to receive the cell groups 13a, 13b, 13c, 13d. For example, the cooling member 31 may have at least one recess into which a battery cell or a cell group may be received and mounted thereon. According to the present example, the mounting provides thermal conductivity between the cooling member 31 and the battery cells 14 in the cell groups 13a, 13b, 13c, 13d. Meanwhile, according to the present example, cell groups 13a, 13b, 13c, 13d are electrically insulated from the cooling member 31, particularly when the cooling member 31 is constructed from electrically conductive material.

In the example illustrated in Figure 3, the cell groups 13a, 13b, 13c, 13d on each face 32,33 of the cooling member 31 are spaced apart to form a first channel 16 between cell groups 13a, 13c on the first face 32 and a second channel 17 between cell groups 13b, 13d on the second, opposing face 33. Each channel 16,17 has a width which is greater than a maximal distance between adjacent battery cells 14 within each cell group. Additionally, the width of each channel 16,17 is greater than an average distance between adjacent battery cells 14 within each cell group 13a, 13b, 13c, 13d.

In the illustrated example of Figures 1, 2, 3 and 4, the first and second channels 16 are located centrally and parallel to a minor dimension and outer edges of the cooling member 31. The channels 16,17 are also perpendicular to the x-dimension and parallel with the y-dimension of a respective battery pack 10 in which the cooling member 31 may be supported. In the example shown, the first channel 16 overlies the second channel 17 and each channel is equidistant from the outer edges of the cooling member 31. In other examples, either of the first and second channels 16,17 may be offset from a centre of the cooling member, and/or the first and second channels 16,17 may not overlie one another. There may be more than two cell groups 13a, 13b, 13c, 13d on each face 32,33 and there may be more than one channel 16,17 on each face between cell groups. The battery modules 12a to 12h are arranged in the arrangement of Figures 1 and 2 side- by-side, width wise, adjacent to and coplanar with one another in the first dimension 25 such that the cell groups 13a, 13b, 13c, 13d of each battery module 12a to 12h are aligned with corresponding cell groups 13a, 13b, 13c, 13d of each other battery module 12a to 12h. In this way, the aligned cell groups 13a, 13b, 13c, 13d form rows 20a, 20b, 20c, 20d of cell groups 13a, 13b, 13c, 13d extending along the first dimension 25 of the battery pack 10. Each row 20a, 20b, 20c, 20d in this example is formed from one cell group 13a, 13b, 13c, 13d of each battery module 12a to 12h. In the example shown, upper and lower surfaces of the battery modules 12a to 12h are coplanar by virtue of the respective cooling members 31 being similarly coplanar.

The first and second channels 16,17 of each battery module 12a to 12h in the example shown are longitudinally aligned with corresponding first and second channels 16,17 of each other battery module 12a to 12h. The alignment of first channels 16 forms a first longitudinal passage 18 between cell groups 13a, 13c in the arrangement, and the alignment of second channels 17 forms a second longitudinal passage 19 between cell groups 13b, 13d in the arrangement. According to the present example, the first and second longitudinal passages 18,19 extend parallel with the first dimension 25 of the battery pack 10.

A length of each cell group 13a, 13b, 13c, 13d in the major dimension of the cell group 13a, 13b, 13c, 13d is generally between 2 and 4 times longer, such as three times longer, than the minor dimension of the cell group 13 a, 13b, 13c, 13d. In other examples, other aspect ratios, herein defined as a ratio between a length of the cell group 13 in the major dimension and a length of the cell group 13 in the minor dimension, are contemplated. The minor dimension of each cell group 13a, 13b, 13c, 13d is parallel with the minor dimension of the cooling member 31 on which it is mounted, and the first and second channels 16,17 of each battery module extend along the minor dimension of the cooling member 31. Furthermore, in the illustrated example, the battery modules 12a to 12h are arranged such that the minor dimensions of respective cooling members 31 and cell groups 13a, 13b, 13c, 13d are aligned with the first dimension 25 of the battery pack 10.

When a battery module 12a to 12h is connected with other battery modules 12a to 12h in a battery pack 10, certain cell groups 13a, 13b, 13c, 13d in the same battery module 12a to 12h are electrically connected in a circuit. However, until a battery module 12a to 12h is connected as such, cell groups 13a, 13b, 13c, 13d are electrically isolated from one another within the battery module 12a to 12h. That is, taking a battery module 12a to 12h in isolation, there are no electrical connections between groups of battery cells 13a, 13c on the first face 32 of the cooling member 31, or between groups of battery cells 13b, 13d on the second face 33 of the cooling member 31 . Similarly, taking a battery module 12 to 12h in isolation, there are no electrical connections between groups of battery cells 13a, 13b, 13c, 13d on opposing faces 32,33 of the cooling member 31. The electrical isolation of individual cell groups 13a, 13b, 13c, 13d within the battery module minimises the live voltage of each group of battery cells, which may lead to enhanced safety during handling and assembly.

Figure 4 shows a schematic cut-away drawing of a battery module 12, which can be employed according to examples herein. Figure 4 also illustrates battery cells 14 in a cell group 13c. Figure 5 illustrates a top-down schematic representation of a cell group 13, which is arranged as shown in Figure 4. The cell group 13 comprises a positive terminal connection 41 and a negative terminal connection 42. The cell group terminal connections 41,42 each connect to a bank (or sub-group) 43a, 43 e of parallel-connected battery cells 14, which are mounted on a periphery of the cell group 13. As will be described, the cell group terminal connections 41,42 are connectable to corresponding cell group terminal connections 41,42 of adjacent battery modules 12a to 12h to form an electrical circuit or current path along a row of cell groups. The cell group terminal connections 41,42 in the example shown each comprise a generally flat or planar tab, which extends, away from the cell group, parallel to a plane of the cooling member 31. In other examples, the cell group terminal connections 41,42 may alternatively, or in addition, comprise any other connection suitable for electrically connecting cell groups 13a, 13b, 13c, 13d of adjacent battery modules 12a to 12h, such as wires.

As illustrated in Figure 5, the battery cells 14 in the cell group 13 are arranged into a plurality of parallel-connected banks (or sub-groups) 43a to 43e of battery cells 14. For clarity, each of the banks 43a to 43e battery cells 14 in Figure 5 is filled white or hatched to distinguish the banks 43a to 43e of battery cells 14 from one another. As shown, each terminal connection 41,42 may be connected to a peripheral parallel-connected bank 43a, 43 e of battery cells 14 by an electrically conductive member acting as a current collector 44. The current collector 44 comprises a formed conductive sheet having a first edge spanning the bank 43a, 43e of battery cells 14 and a converging region, which converges downwardly from an upper surface of the cell group to the cell group terminal connection 41,42, which is relatively narrow compared to the length of the first edge. The current collector 44 is configured to conduct current between the peripheral, parallel-connected bank 43a, 43e of battery cells 14 and the cell group terminal connection 41,42.

The battery cells 14 in each bank 43a to 43e of battery cells 14 extend along the major dimension of the cell group 13 and are connected to one another in parallel by a respective busbar 45. In the present example, the busbar 45 may be an elongate electrically conducting wire, plate or rod with connections (not shown in detail) to respective positive or negative terminals 48,49 of the battery cells 14 along a bank 43a to 43e. Each busbar spans the major dimension of the cell group 13. With the exception of busbars 45 on a periphery of the cell group 13, each busbar 45 in the illustrated example is configured to connect the positive battery cell terminals 48 of each battery cell in one bank of battery cells 14 to the negative battery cell terminal 49 of each battery cell in an adjacent bank of battery cells 14. In this way, a single busbar 45 connects the battery cells 14 of a first bank 43a to 43e in parallel to one another and the battery cells 14 of a second bank 43a to 43e in parallel to one another, while also connecting the first bank in series with the second bank. Each busbar 45 on a periphery of the cell group 13 is configured to connect the battery cells 14 of a respective peripheral bank 43a, 43e of battery cells 14 in parallel to one another.

The illustrated example shows five sub-groups or banks 43a to 43e of parallel-connected battery cells 14, each sub-group 43a, 43b comprising six or seven battery cells 14; however, in other examples there may be any number of such sub-groups 43a to 43 e and any number of battery cells 14 in each sub-group 43. Furthermore, the illustrated sub groups 43a to 43 e span a length of the cell group 13 in the major dimension, and each sub-group is confined to a single row in the fixed arrangement 40. As illustrated, each sub-group 43a to 43e is generally a one-dimensional rectangular array. It will be understood that, in other examples, each bank or sub-group 43a to 43 e of parallel connected battery cells 14 may not span the entire length of the cell group 13 in the major dimension, and that the banks 43 a to 43 e may span multiple rows in the fixed arrangement 40, or may not be confined to such rows or rectangular arrays.

In the illustrated example, the banks 43a to 43e of battery cells 14 are connected such that current flows in series between banks in the minor dimension of the cell group 13. As such, the current flow in a cell group 13 may in the aggregate be perpendicular to busbars 45, which extend in the major dimension. The direction is said to be ‘in the aggregate’, or ‘on average’, as there may be some minor deviations in current flow direction, for instance, which may be determined by the particular arrangement of the battery cells 14 and/or the shape of the busbars 45 connecting the battery cells 14.

Figure 6 is a schematic view of a battery module 12 showing the aggregate direction of so-called cell group current paths 60, between banks 43a to 43e of battery cells 14, in each cell group 13a, 13b, 13c, 13d of the battery module . The current flowing in each cell group current path 60 is an aggregate of current flowing through at least the battery cells 14 and busbars 45 of the cell group 13. The current flow in a cell group current path 60 is spread across a length of the cell group 13 in the major dimension of the cell group 13 and flows in a direction parallel to the width of the cell group in the minor dimension of the cell group 13 width-wise through the elongate busbars 45.

Having elongate busbars 45 spanning the major dimension of a cell group, while having an aggregate current path 60 across the minor dimension of the cell group, enables the thickness of the busbars 45 to be reduced (compared with having busbars 45 spanning the minor dimension and having an aggregate current 60 path across the major dimension), whilst maintaining a desired cross-sectional area and current density. For example, the illustrated example comprises cell groups 13a, 13b, 13c, 13d having an aspect ratio of approximately 3:1 (that is, having a major dimension three times longer than a minor dimension). The cell groups 13a, 13b, 13c, 13d may therefore comprise busbars 45 which are in the order of three times thinner than those that would be required for a cell group 13 with an aspect ratio of 1:1, whilst providing the same current density in the busbars 45. Thus, busbars 45 may be thinner and lighter per unit area, which means they require less space per unit area and may be more easily formed, for instance, for the purposes of connecting to the terminals of individual battery cells. Furthermore, a shorter cell group current path 60 may lead to a reduced electrical resistance in the busbar 45, as resistance is proportional to the length of the current path.

As illustrated in Figure 6, the cell groups 13a, 13b, 13c, 13d in abattery module 12a to 12h are configured so that the current flow in each cell group current path 60 flows in an opposite direction to the current flow in each adjacent and each overlying/underlying cell group current path 60. In the illustrated example, adjacent current paths 60 are arranged parallel to one another in the same horizontal plane, for instance as defined by the ‘x’ and ‘y’ axes, whilst over and underlying current paths are arranged parallel to one another in horizontal planes spaced apart in the z-direction. The arrangement of battery cells and busbars in each cell group 13a, 13b, 13c, 13d is the same or similar, and the cell groups 13a, 13b, 13c, 13d are mounted on the cooling member 31 and connected in such a way that current flows across a cell group 13 in a direction opposite to that in corresponding adjacent and overlying/underlying cell groups 13 a, 13b, 13c, 13d. For example, the cell groups 13a, 13c on the first face 32 may be rotated 180 degrees relative to one another around an axis orthogonal to the major and minor dimensions of the cooling member 31, whilst corresponding cell groups 13a, 13b and 13c, 13d on respective opposing faces 32,33 may be rotated 180 degrees relative to one another around an axis parallel to the major dimension of the cooling member 31.

Figure 7 shows a portion of the arrangement of battery modules 12a to 12h as shown in Figures 1 and 2. In the example shown there are four rows 20a, 20b, 20c, 20d of cell groups 13 a, 13b, 13c, 13d. Each row 20a, 20b, 20c, 20d comprises a single cell group 13a, 13b, 13c, 13d from each battery module 12a to 12h. The rows 20a, 20b, 20c, 20d in the example shown may each also be considered as a layer or laminar arrangement of cell groups. In this context, a single row 20a, 20b, 20c, 20d of cell groups 13a, 13b, 13c, 13d can be considered as a laminar arrangement and, equally, two adjacent rows 20a, 20b, 20c, 20d that are supported on the same face of a cooling member 31 may also be considered as a laminar arrangement of cell groups 13 a, 13b, 13c, 13d. In other examples, the rows 20a, 20b, 20c, 20d may be any other laminar arrangement of cell groups 13 a, 13b, 13c, 13d. The cell groups 13a, 13b, 13c, 13d in a row 20a, 20b, 20c, 20d or a laminar arrangement according to the present example are also co-planar. In particular, according to the present example, upper and lower surfaces of the cell groups 13 a, 13b, 13c, 13d, in a row 20a, 20b, 20c, 20d or across adjacent rows 20a, 20b, 20c, 20d, share a common plane.

The longitudinal passage 18 separates rows 20a, 20c of cell groups 13a, 13c on the first faces 32 of respective cooling members 31, and the longitudinal passage 19 separates rows 20b, 20d of cell groups 13b, 13c on the second faces 33 of respective cooling members 31. The battery modules 12a to 12h are spaced apart along the first dimension 25 in the battery pack 10 arrangement to form a plurality of transverse passages 27 in the battery pack 10. The transverse passages 27 of the illustrated example extend in the second dimension 26 of the battery pack 10. The cell groups 13a, 13b, 13c, 13d in each row 20a, 20b, 20c, 20d are electrically connected in series via respective positive and negative cell group terminal connections 41,42 to form a plurality of so-called aggregate row current paths 61, each extending along the first dimension 25. In the example illustrated by Figures 6 and 7, the cell groups 13a, 13b, 13c, 13d in each row 20a, 20b, 20c, 20d are connected in series by respective cell group terminal connections 41,42 to define an aggregate row current path 61, or “aggregate current arm” 61, extending along the row 20a, 20b, 20c, 20d. In other words: the cell groups 13a in the first row 20a are electrically connected to define a first aggregate current arm 61a in the first row 20a of cell groups 13; the cell groups 13b in the second row 20b are electrically connected to define a second aggregate current arm 61b in the second row 20b of cell groups 13; the cell groups 13c in the third row 20c are electrically connected to define a third aggregate current arm 61c in the third row 20c of cell groups 13; and the cell groups 13d in the fourth row 20d are electrically connected to define a fourth aggregate current arm 61d in the fourth row 20d of cell groups 13 a, 13b, 13c, 13d. The current flowing in an aggregate current arm 61a,61b,61c,61d therefore comprises an aggregate of current flowing through each cell group 13a, 13b, 13c, 13d in a row 20a, 20b, 20c, 20d, and currents flowing between cell groups 13a, 13b, 13c, 13d via respective cell group terminal connections 41,42. In the illustrated example, the aggregate current arms 61a,61b,61c,61d are substantially parallel with one another in the arrangement of battery modules 12a to 12h.

As shown in Figure 7, the first aggregate current arm 61a is spaced apart from and adjacent to the third aggregate current arm 61c and the second aggregate current arm 61b is spaced apart from and adjacent to the fourth aggregate current arm 6 Id. Furthermore, the first, second third and fourth rows 20a, 20b, 20c, 20d are electrically connected such that: current in the second aggregate current arm 61b flows in an opposite direction to that in the first aggregate current arm 61a; current in the fourth aggregate current arm 61d flows in an opposite direction to that in the third aggregate current arm 61c; current in the third aggregate current arm 61c flows in an opposite direction to that in the first aggregate current arm 61a; and current in the fourth aggregate current arm 61d flows in an opposite direction to that in the second aggregate current arm 61b. In other words, the current flow in each aggregate current arm 61 flows in an opposite direction to that in each adjacent or overlying/underlying aggregate current arm 61.

Figure 8 illustrates a top-down schematic view of the arrangement of battery modules 12a to 12h in the battery pack 10. The cell group terminal connections 41,42 of respective cell groups 13a, 13b, 13c, 13d on one side of the battery modules 12a to 12h are located in respective transverse passages 27. The cell group terminal connections 41,42 of adjacent cell groups 13a, 13b, 13c, 13d in the arrangement are collocated in a respective transverse passage 27 to make efficient use of available space and to enable a mechanical and electrical connection to be accessed and reliably maintained. The cell group terminal connections 41,42 of cell groups 13a, 13b, 13c, 13d in the same row and in adjacent battery modules 12a to 12h are electrically coupled, for example by being fastened together, to create an electrical connection between the cell group terminal connections 41,42. The fastening may be achieved, for example, by bolting, gripping, or otherwise urging and securing the cell group terminal connections 41,42 together. In other examples, the cell group terminal connections 41,42 may, for instance, be adjacent to and/or spaced apart from one another, and/or they may not be coplanar. In such instances, the cell group terminal connections 41,42 may be connected by an appropriate connector.

In the illustrated example, the cell group terminal connections 41,42 are located in the transverse passages 27 and are offset in the x dimension from a central axis 28 of each cell group 13 a, 13b, 13c, 13 d, the central axis 28 being located in a midpoint of the cell group 13a, 13b, 13c, 13d in the major dimension of the cell group 13a, 13b, 13c, 13d and oriented parallel to the minor dimension of the cell group 13 a, 13b, 13c, 13d. In the illustrated example, the cell group terminal connections 41,42 are offset from a plane of the cooling member 31 in the z-direction. In other examples, the cell group terminal connections 41,42 may be coplanar with a plane of the cooling member 31. In the illustrated example, as shown in Figure 8, cell group terminal connections 41,42 of the first cell group 13a are offset from the central axis 28 in a first direction parallel to the second dimension 26 of the battery pack 10. Cell group terminal connections 41,42 of the second, underlying cell group 13b are offset in a second direction, opposite the first direction. The same is true for the cell group terminal connections 41,42 of the third and fourth cell groups 13c, 13d. In this way, the cell group terminal connections 41,42 of corresponding upper and lower cell groups 13a, 13b, 13c, 13d are not collocated or overlying/underlying. In other examples, the cell group terminal connections 41,42 may not be offset in the x dimension from a central axis 28, or cell group terminals 41,42 of corresponding overlying/underlying cell groups 13a, 13b, 13c, 13d may be offset in the same direction in the x dimension.

In the illustrated example as shown in Figures 7 and 8 the first and second rows 20a, 20b are electrically connected by a first connector 63a to form a first battery pack current path (or a “first circuit”) 62a, and the third and fourth rows 20c, 20d are electrically connected by a second connector 63b to form a second battery pack current path (or a “second circuit”) 62b. Therefore, each circuit 62a, 62b may be formed by one laminar arrangement or row 20a, 20c in a first plane and one laminar arrangement or row 20b, 20d in a second plane, spaced from and parallel to the first plane. In other examples, each circuit 62a, 62b may be formed by two laminar arrangements in one plane. The circuits 62a, 62b are spaced apart and adjacent to one another. The circuits 62a, 62b are illustrated in Figure 8, in which a solid line represents current flowing along respective rows 20a, 20c in the first plane, and a dashed line represents current flowing along respective rows 20b, 20d in the second plane (underlying the first plane).

In one example, the first and second connectors 63a, 63b comprise fuses and/or disconnects, such as isolation switches or plugs. The connectors 63 are located at common positions along the first dimension 25 of the battery pack 10. In the illustrated example, the connectors 63 are each located at a second end 55 of the battery pack 10. Each row 20a, 20b, 20d, 20c comprises a first end electrical connection terminal (herein a “first end terminal”) 64a, 64b, 64c, 64d located at a first end 66 of the row 20a, 20b, 20c, 20d parallel to the first dimension 25 and a second end electrical connection terminal (herein a “second end terminal”) 65a, 65b, 65c, 65d located at a second, opposite end 67 of the row 20a, 20b, 20d, 20c parallel to the first dimension 25. The first and second ends 66,67 of each row 20a, 20b, 20c, 20d are located at respective first and second ends 54,55 of the battery pack 10. The second end terminals 65a, 65b of the first and second rows 20a, 20b are connected by the first connector 63a and the second terminals 65c, 65d of the third and fourth rows 20c, 20d are connected by the second connector 63b. In the illustrated example, the first end terminal 64a of the first row 20a and the first end terminal 64d of the fourth row 20d each comprise a positive terminal, and the first end terminal 64b of the second row 20b and the first end terminal 64c of the third row 20c each comprise a negative terminal. In this way, current flows through the first circuit 62a in an opposite direction to current flow in the second circuit 62b. The first terminals of each row may be connected in the battery pack such that the first circuit is connected in series or in parallel with the second circuit. In some examples, the connection of circuits 62a, 62b in series or parallel is configurable, so that an electrical energy input/output of the battery pack is also configurable.

An aggregate magnetic field may be generated by passing a current through an aggregate current arm 61. Figure 9 illustrates a frontal schematic view of aggregate magnetic fields 68a to 68d generated by current flowing through respective aggregate current arms 61a to 6 Id. The aggregate current arms 61a to 61d are shown as points and crosses in Figure 9, the points representing current flowing into (cross) and out of (point) the page. Having current flowing in opposite directions in adjacent and overlying/underlying aggregate current arms 61, as described, provides aggregate magnetic fields 68a-6d having opposite orientations. In the illustrated example, the aggregate magnetic fields 68a, 68d generated by current flowing along first and fourth aggregate current arms 61a,61d have the same orientation, which is opposite to that of the magnetic fields 68b, 68c generated by current flowing in the opposite direction along second and third aggregate current arms 61b, 63c. The aggregate magnetic fields 68a to 68d interact in a region between rows 20a to 20d. Particularly, the aggregate magnetic fields 68a to 68d interact such that a local magnetic field 69 in a central region between rows 20a to 20d is reduced. Figure 9 illustrates example magnetic field lines 69 of a local magnetic field in such a central region, highlighting a contribution from each of the aggregate magnetic fields 68a to 68d. Opposing contributions in the x- and z-dimensions are oriented in opposite directions, as shown by the local magnetic field lines 69, meaning that the aggregate magnetic fields 68a to 68d at least partially counteract one another in the central region. Hence, a region having a reduced magnetic field may be formed between rows 20a to 20d as a result of current flowing in opposite directions in each adjacent and overlying/underlying aggregate current arm 61a to 6 Id. In some examples, circuitry may be disposed in a low magnetic field region between rows, thereby reducing a level of potential magnetic interference with potentially sensitive components.

Figures 10 and 11 show a part of a cooling assembly 30 for cooling respective battery modules 12a to 12h in a battery pack 10. The cooling assembly 30 comprises cooling members 31 and ancillary supply and return conduits 35a, 35b as introduced with reference to Figures 1 to 4. The ancillary supply and return conduits 35a, 35b are fluidically coupled to respective inlet and outlet ports 34a, 34b of a respective cooling member 31 to supply a flow of coolant to the cooling member 31. The inlet and outlet ports 34a, 34b may be considered cooling member inlets and outlets 34a, 34b. The cooling assembly 30 further comprises common supply and return conduits 36a, 36b which interface with the ancillary supply and return conduits 35a, 35b of respective battery modules 12a to 12h via a plurality of tapped connections 37. Each tapped connection 37 of the common supply conduit 36a is fluidically coupled to the ancillary supply conduit 35a of a respective cooling member 31, and each tapped connection 37 of the common return conduit 36b is fluidically coupled to the ancillary return conduit 35b of a respective cooling member 31. In this way, the common supply and return conduits 36a, 36b are configured to carry fluid respectively to and from the cooling member 31 of each battery module 12a to 12h via coupled ancillary supply and return conduits 36a, 36b. It will be understood that the common supply and return conduits 36a, 36b and the ancillary supply and return conduits 35a, 35b may instead be referred to as common and ancillary inlet and outlet conduits, respectively.

In the illustrated example, the ancillary supply and return conduits 35a, 35b are each located in the first channel 16 of a respective battery module 12, and the common supply and return conduits 36a, 36b are each located in the second channels 17 of respective battery modules 12a to 12h. In this way, the ancillary supply and return conduits 35a, 35b are located conveniently in the first longitudinal passage 18 and the common supply and return conduits 36a, 36b are located conveniently in the second longitudinal passage 19. The common and ancillary conduits 35,36 are therefore connected across a plane defined by the cooling member 31. The connection may be, for instance, in a transverse passage 27 between battery modules 12a to 12h. Alternatively, or in addition, the ancillary supply and return conduits 35a, 35b may traverse the plane defined by the cooling member 31 to fluidically couple the common supply and return conduits 36a, 36b to respective fluid inlet and outlet ports 34a, 34b. In some examples, the ancillary and common conduits 35,36 may each be located in the same longitudinal passage 18,19, or they may be located in different longitudinal passages 18,19. In other examples, the ancillary supply and return conduits 35a, 35b may not be required, and the common supply and return conduits 36a, 36b may be fluidically coupled directly to the cooling member 31.

Figure 12 shows a top-down schematic view of an example cooling member 31. The cooling member 31 comprises an inlet plenum 38a and an outlet plenum 38b. The fluid inlet port 34a is configured to carry or pass fluid to the inlet plenum 38a and the fluid outlet port 34b is configured to carry or pass fluid to the outlet plenum 38b. The cooling member 31 comprises one or more flow paths 39 for carrying fluid between the inlet plenum 38a and the outlet plenum 38a. In one example, the cooling member 31 may be generally hollow and may comprise a plurality of channels within the cooling member 31 for carrying fluid in the cooling member 31. The cooling fluid may be a water/glycol mix or it may be any other mix of cooling fluid. In the illustrated example, the flow paths 39 extend along a major dimension of the cooling member 31. In other examples, the flow paths 39 may be winding, serpentine or tortuous.

Figure 13 shows two adjacent cooling members 31 according to an example. The cooling members 31 comprise mounting features 52 for mounting the respective battery module 12a to 12h in a battery pack 10. Figure 14 shows an expanded schematic view of an example mounting feature 52 of a cooling member 31. The mounting features 52 cooperate with corresponding mounting features 52 of an adjacent cooling member 31 to define one or more apertures 57, each aperture configured to receive a fastener 53 for fixing the cooling member 31 to a frame 50 of a battery pack 10. In the illustrated example, the mounting features 52 comprise peripheral tabs, each tab comprising at least one recess 58. Therefore, each cooling member 31 comprises one or more recesses 58 at a periphery of the cooling member. The recesses 58 of adjacent cooling members 31 cooperate to at least partially define, or delimit, the one or more apertures 57. The mounting features 52 and/or the recesses 58 are disposed on each cooling member 31 such that the one or more apertures 57 are defined for only a single orientation of adjacent cooling members 31. That is, in the example shown, the cooling members 31 are not symmetric, and battery modules 12a to 12h may only be mounted in a battery pack 10 in a single, correct orientation. This provides a convenient way of ensuring cell groups 13a, 13b, 13c, 13d are mounted in a desired orientation during manufacture and assembly of a battery pack 10. In other examples, the mounting features 52 may not comprise tabs, and the recesses 58 may instead be defined on a periphery of a main body of the cooling member 31.

As shown in Figure 14, a mounting feature 52 may comprise a location feature 59 for locating the cooling member relative to a frame 50. The frame 50 comprises at least one hole for receiving a respective one or more of the fasteners 53, and the location feature 59 is received in the at least one hole. In the illustrated example, the location feature 59 comprises a projection extending from the cooling member. The or each projection may be a tapered projection, such as a conical, or semi-conical projection as in the illustrated example. In other examples, the projection may be any other shape of projection, such as a straight projection or a rounded projection.

Figure 15 shows an example frame 50 of a battery pack 10. The frame 50 comprises at least one lower support member 70 and at least one upper support member 71. A plurality ofbattery modules 12a to 12h (not shown in Figure 15) in the battery pack lO are mounted to the lower support member in the arrangement via respective cooling members 31. The lower support member 70 comprises a hole or an aperture for receiving a location feature 59 of a cooling member 31, and/or for receiving a fastener 53 for fastening the cooling member 31 to the lower support member 70. The upper support member 71 is secured to the lower support member 70, and a cooling member 31 is located between the lower and upper support members 70,71. In some examples, the cooling member 31 may be clamped and held in place by the lower and upper support members 70,71. The frame 50 comprises at least one cut-out 72 configured to cooperate with the first and/or the second longitudinal passage 18,19. In this way, the common supply and return conduits 36a, 36b may be disposed in a respective longitudinal passage 18,19 and in the cut-out 72. In the illustrated example, the cut-out 72 is disposed in the at least one lower support member 70. In other examples, the cut-out may be disposed in the at least one upper support member 72, or in both of the lower and upper support members 70,71.

In some examples, the battery pack 10 and/or the battery module 12a to 12h may be suitable for an electric vehicle. Figure 16 shows a schematic side elevation of an electric vehicle 80 comprising a battery pack 10 disposed in the electric vehicle 80. The battery pack 10 may be disposed towards a lower side of the electric vehicle 80 in order to lower a centre of mass of the electric vehicle 80.

Figure 17 shows a schematic view of an underside of an electric vehicle 80. The electric vehicle 80 may comprise a front electric drive unit 81 and a rear electric drive unit 82 for delivering power to driving wheels 83 of the electric vehicle 80. The battery pack 10 may be located between the front and rear electric drive units 81 ,82. The front and rear electric drive units 81,82 may comprise invertors for converting DC battery current into AC current to be delivered to traction motors. In the illustrated example, the battery pack 10 comprises an electrical connection 85 for connecting the battery pack 10 to the rear electric drive unit 82. The electrical connection 85 extends along at least one of the longitudinal passages 18,19 of the battery pack. In some examples, the battery pack 10 is arranged such that a battery input/output 86 is located towards the front electric drive unit 81 of the electric vehicle and the electrical connection 85 extends from the battery input/output 86 and along a longitudinal passage 18,19 to the rear electric drive unit 81. The rear electric drive unit 82 may comprise an inverter, and the electrical connection 85 may be connected to the inverter. In other examples, an electrical connection connecting the input/output 86 of the battery pack to the front electric drive unit 81, or to a charging port of the electric vehicle 80, may extend along a longitudinal passage 18,19 of the battery pack 10. In further examples, the battery input/output may be located at any other location on the battery pack 10, such as towards a rear electric drive unit 82 of an electric vehicle 80 to which it is employed.

In the illustrated example, the battery pack 10 comprises eight battery modules 12, each comprising four cell groups 13a, 13b, 13c, 13d. In some examples, there may be more than or fewer than eight battery modules 12a to 12h in a battery pack 10, and/or more than or fewer than four cell groups 13a, 13b, 13c, 13d in a battery module 12a to 12h. In one example, the battery pack 10 is configured so that each aggregate current arm 6 la-6 Id delivers a maximum of 201.6 Volts (V), with a nominal voltage of around 175V. As such, each of the first and second circuits 62a, 62b, each comprising a respective two of the aggregate current arms 61a to 6 Id, are configured to deliver a maximum of around 400 V. The battery pack 10 input/output 86 may be connected to circuitry for controlling the configuration of the battery pack 10 so that the first and second circuits 62a, 62b may be connected in series or in parallel. A description of such control circuitry is outside the scope of the present disclosure. The battery pack 10 may thereby be operable at around 800 V when the first and second circuits 62a, 62b are connected in series, and/or around 400 V when the first and second circuits 62a, 62b are connected in parallel. Operating the battery pack 10 at a particular voltage may comprise charging or delivering energy at that voltage.

The aggregate current arms 61a,61b,61c,61d have one terminal at the first end 54 of the battery pack 10, and one terminal at the second end 55 of the battery pack 10. In this way, the connectors 63 a, 63b provide a convenient means of physically separating the battery pack into lower voltage sub-packs for safety and handling. Furthermore, locating first and second end terminals 64,65 at opposite ends 54,55 of the battery pack 10 means that, during handling, it may be difficult to make contact with both of the first and second end terminals 64,65 at once. This is particularly relevant if a length of the battery pack 10 in the first dimension 25 is longer than a typical human arm span, which may be the case in some examples. The connections 63a, 63b are located at the second end 55 of the battery pack, adjacent to the second end terminals 65a, 65b, 65c, 65d. The connections 63a, 63b and the second end terminals 65a, 65b, 65c, 65d may therefore be accessed through a common hatch at the second end 55 of the battery pack 10.

It will be understood that, in some examples, the battery pack 10 and the current paths or circuits comprised therein may be configured to operate at voltages other than those described. For example, a battery pack 10 configured for use in a home energy storage system or may operate at voltages lower than 400 V, while a battery pack 10 configured for industrial use may operate at higher voltage than 800V.

In the illustrated example, the battery pack 10 comprises a battery management system (“BMS”) 84 configured to control the charging/discharging and general operation of the battery pack 10. The BMS may comprise the input/output 86 of the battery pack 10 and/or circuitry for monitoring information relating to the operation of the battery pack 10, among other things. In the illustrated example, the BMS 84 comprises a main circuit board located at the first end of the battery pack 10 and circuitry located in the channels 16,17 of respective battery modules 12a to 12h or the longitudinal passages 18,19 of the battery pack 10. BMS 84 circuitry may be located in a region of the battery pack 10 having a low magnetic field strength.

The above examples are to be understood as illustrative examples of the invention. Further examples of the invention are envisaged. For example, a battery pack 10 or a battery module 12a to 12h may instead be used to provide and store electrical energy for any kind of industrial, commercial, or domestic purposes, such as for energy storage and delivery, for example, in smart grids, home energy storage systems, electricity load balancing and the like. A battery pack 10 may comprise any number of battery modules 12, and the cell groups 13a, 13b, 13c, 13d may comprise any number of battery cells 14.

It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.