Technical Field The present invention relates to batteries and, particularly, to a battery module and a battery pack comprising the battery module. In particular, but not exclusively, the present invention relates a battery module, and a battery pack for an electric vehicle.

Background

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

According to a first aspect of the invention there is provided a battery module comprising: at least one cell group, the cell group comprising an array of cells, the array having a major dimension and a minor dimension perpendicular to the major dimension, the array comprising one or more sub-groups of cells, each sub-group comprising a plurality of parallel-connected cells arranged spanning the major dimension; and a current collector for carrying current to or from the cell group, the current collector comprising an electrical conductor spanning the major dimension of the cell group and converging to at least one electrical contact for electrically coupling the battery module. Providing a current collector with at least one electrical contact may allow a reliable and simplified connection to be made between the battery module and a further battery module. This may also reduce the need for excess wiring or complex cable routing. The current collector spanning the major dimension allows the current collector to transfer current from across the cell group in a manner that maintains a balanced current flow distribution across the cell group.

The array may comprise a two-dimensional array. The current collector may comprise a current collector for carrying current to or from a sub-group of cells on the periphery of the cell group. The current collector may comprise an edge spanning the major dimension of the cell group, for example spanning a sub-group at the periphery of the cell group. The current collector may comprise a converging region converging to the at least one electrical contact. The electrical contact may, for example, comprise an electrical contact for electrically coupling the battery module to another battery module.

The current collector may converge to a plurality of electrical contacts.

This may allow multiple connections to be made between the battery module and a further battery module. Multiple connections may provide a level of redundancy in the event of a failure of one of the connections.

The current collector may comprise a plurality of converging regions, each converging to at least one electrical contact. This may allow multiple connections to be made between the battery module and a further battery module. Multiple connections may provide a level of redundancy in the event of a failure of one of the connections. The sub-groups in the array may be connected to one another in series and arranged so that an aggregate current flows across the cell group in a direction parallel to the minor dimension. Having the aggregate current flow in a direction parallel to the minor dimension allows busbars, used to transport current across the battery module, and the current collectors to be made from thinner material, thereby providing flexibility in the current collectors. Having at least partially flexible current collectors which connect between battery modules may provide a more reliable connection and increase resilience to torsional stresses. This may also increase the ease of manufacture as tolerances used in the manufacturing processes may be lower while still maintaining secure and reliable connections between battery modules via the current collectors.

The at least one cell group may comprise positive and negative terminals, wherein the positive and negative terminals are defined by a respective current collector.

For example, a first current collector may act as a positive terminal of the cell group and a second current collector may act as a negative terminal of the cell group. The battery module may comprise a positive current collector at one end of the cell group, and a negative current collector at a second opposite end of the cell group.

This may provide a simple single connection to be made to each of the positive and negative terminals, simplifying the manufacture and maintenance of the battery module. The current collector may be formed from a sheet of formable material, for example by shaping a sheet of formable material.

This may provide the current collector with at least some flexibility such that the connections between adjacent battery modules are secure and resilient to flexing. This may also reduce the tolerances requires during manufacturing and may utilize materials which cost less to manufacture.

The current collector may extend in a direction orthogonal to the major and minor dimensions.

This may allow the current collector to have an electrical connection point at a position which is readily connectable to other battery modules. The current collector may converge along a direction orthogonal to the maj or and minor dimensions.

As the current collector spans a length of the major dimension, having the current collector converge in a direction orthogonal to the major and minor dimensions may allow a contact point of the current collector to be smaller than the length of the major dimension while still allowing the current collector to transfer the aggregate current from across cell group, in a manner that maintains a balanced current flow distribution across the group of cells. The at least one electrical contact may comprise a tab protruding from the current collector.

A tab may provide a secure and reliable connection point onto which further tabs may be quickly connected or removed during manufacture or maintenance.

The tab may protrude in a direction parallel to the minor dimension.

In this way, the at least one electrical contact extends towards an adjacent cell group during assembly and so may be readily attached to or met by an opposing contact extending from the adjacent cell group. The at least one electrical contact may be offset from a central axis located in a centre of the array in the major dimension and orientated parallel to the minor dimension. This may allow cell groups on opposing sides of a support in the battery module to have electrical contacts which are readily accessible whilst maintaining electrical isolation from one another.

The battery module may comprise: a support, a first cell group comprising a first current collector mounted on a first face of the support, and a second cell group comprising a second current collector mounted on a second, opposing face of the support, wherein the at least one electrical contact of the first current collector is offset from the at least one electrical contact of the second current collector. The at least one electrical contact of the first current collector may be offset from the central axis in a first direction parallel to the major dimension, and the at least one electrical contact of the second current collector may be offset from the central axis in a second direction opposite to the first direction.

Having opposingly offset electrical contacts may provide a desired electrical contact having a suitable size whilst maintaining electrical isolation between the first cell group and the second cell group. This may also allow the current collectors used on both sides of the cell group to be the same and hence only one type of current collector may be manufactured. This may increase the scalability of the manufacturing process as fewer types of parts may be manufactured to produce the battery modules. Further, offset electrical contacts may also allow for other connections, such as structural connections for mounting a battery module to a frame within a battery pack, to be formed intermediate with the electrical connections, providing an efficient use of space.

The support may be planar, and each electrical contact may be offset from the support in a direction orthogonal to the plane of the support. This may prevent the electrical contacts from being located near the support. Where the support is constructed from an electrically conductive material, ensuring that the electrical contacts and the support do not come into physical contact may reduce the risk which is present during manufacture and maintenance of the battery modules.

The major dimension may be between two to four times longer than the minor dimension. This may allow the battery module to achieve a desired voltage while also reducing the thickness of the busbars to allow flexibility in the design and production cost savings.

The battery module may be for an electric vehicle. The battery module may be used in electric vehicles where reducing weight of components, providing a desired energy density, having modular components which may be removed and attached quickly are desired.

According to a second aspect of the invention there is provided a battery pack comprising a plurality of battery modules as described above.

A battery pack comprising a plurality of battery modules as described above may provide a battery pack with reduced weight, which is easier to manufacture, and has greater modularity of components for maintenance.

The battery modules may be arranged side-by-side such that the minor dimensions of the battery modules are aligned along a major dimension of the battery pack such that an aggregate current flows along the major dimension of the battery pack. Providing a battery pack where the aggregate current flows in a minor dimension across individual modules may allow thinner busbars to be used providing ease of manufacture as described above. Aligning the battery modules along a major dimension of the battery pack allows and connecting them in this was may allow a desired voltage to be generated across the battery pack to power an electric motor, for example an electric motor in an electric vehicle.

Each battery module of the battery pack may comprise: a support; a first cell group comprising a first current collector mounted on a first face of the support; and a second cell group comprising a second current collector mounted on a second, opposing face of the support, and wherein each array may comprise a central axis located in a centre of the array in the major dimension of the battery module and orientated parallel to the minor dimension of the battery module, wherein a cell group on the first face of each battery module is electrically connected to a corresponding cell group on the first face of an adjacent battery module via a respective first pair of current collectors, wherein a cell group on the second face of each battery module may be electrically connected to a corresponding cell group on the second face of an adjacent battery module via a respective second pair of current collectors, and wherein a common electrical connection point of each first pair of current collectors may be offset from a common electrical connection point of each second pair of current collectors. The common electrical connection point of each first pair of current collectors may be offset from the central axis of the array in a first direction parallel to the major dimension of the battery module, and a common electrical connection point of each second pair of current collectors may be offset from the central axis in a second direction, opposite the first direction.

In this way the battery pack may comprise a tightly arranged plurality of battery modules comprising cell groups which are connected in series along the first dimension of the battery pack. This efficient packing and connection strategy may provide an appropriate trade-off between energy density in the battery pack, secure electrical connection between adjacent cell groups, and the ability to remove or replace individual battery modules easily without having to replace and entire battery pack.

The battery pack may be an electric vehicle battery pack.

The battery pack, connected as described above, may provide electrical energy in a form which can be used to power electric motors for electric vehicles whilst also simplifying the routing of cables and positioning of terminals of the battery pack. According to a third aspect of the invention there is provided an electric vehicle comprising a battery module as described above.

According to a fourth aspect of the invention there is provided an electric vehicle comprising a battery pack as described above.

Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings. Brief Description of the Drawings

In order that the present invention may be more readily understood, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an illustrative view of an assembled battery pack, according to an example;

Figure 2 is an illustrative view of an arrangement of battery modules in the battery pack of Figure 1; Figure 3 is an illustrative view of a battery module of the battery pack of Figure i; Figure 4A is a first illustrative view of battery cells within the battery module of Figure 3;

Figure 4B is a second illustrative view of the battery cells of Figure 4A;

Figure 5 A is a top-down schematic view of a part of the battery module of Figure 3, showing battery cells and busbars;

Figure 5B is an illustrative perspective view of the battery module of Figure 5 A;

Figure 6A is an illustrative perspective view of an alternative example of a current collector;

Figure 6b is an illustrative perspective view of a second alternative example of a current collector;

Figure 7A is an illustrative perspective view of the battery module of Figure 3;

Figure 7B is a top-down schematic view of the battery module of Figure 7A;

Figure 8 is an illustrative view of current flow directions in the arrangement of battery modules of Figure 2; Figure 9A is an illustrative perspective view of a part of a battery module comprising a battery cell carrier, according to an example;

Figure 9B is an end-on schematic view of the battery cell carrier and bus bar of Figure 9 A;

Figure 10A is a side-on schematic view of a battery cell used in the battery module of Figure 9A;

Figure 1 OB is a top-down schematic view of the battery cell of Figure 10A;

Figure 11 is an illustrative perspective view of a battery cell carrier according to an example;

Figure 12A is a top-down schematic view of a battery cell carrier holding a plurality of cells according to an example;

Figure 12B is an illustrative perspective view of a portion of the battery cell carrier and cells according to Figure 12A;

Figure 13 is an illustrative view of an alternative, simplified battery cell carrier, according to an example; Figure 14 is an illustrative view of a battery module comprising a battery cell carrier according to Figure 13 and a plurality of cells, according to an example;

Figure 15 is a flow diagram of a method of assembling a battery module comprising a battery cell carrier and a plurality of cells, according to an example; Figure 16 is a side-on schematic view of an electric vehicle, according to an example; and

Figure 17 is a top-down schematic view of an underside of an electric vehicle, according to an example. Detailed Description

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 certain examples are set forth. Reference in the specification to "an 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 certain examples are described schematically with certain features omitted and/or necessarily simplified for ease of explanation and understanding of the concepts underlying the examples.

Certain examples described herein relate to a battery module comprising a plurality of battery cells. The battery module may be part of an arrangement of battery modules forming at least part of a battery pack. The following description of battery modules and battery packs is given with reference to the use of these elements in electric vehicles. However, it is to be understood that the elements described herein may be utilized in any kind of industrial, commercial, or domestic application, such as for energy storage and delivery, for example, in smart grids, home energy storage, electricity grid load balancing and the like. Certain examples described herein relate to components of a battery module including a battery cell carrier for securing and locating a plurality of battery cells and respective busbars. The battery cell carriers described herein may allow busbars to be accurately and efficiently located with respect to corresponding cells during an assembly of an associated battery module. In other examples, current collectors are provided to conduct current along a minor dimension of groups of cells comprised in the battery modules, thereby providing efficient and reliable connections between adjacent battery modules. For a given cross-sectional area, conducting current along the minor dimension of the groups of cells may also allow thinner busbars to be used to connect sub-groups of cells which decreases weight and manufacturing costs. A shorter length of current path may also reduce the resistance in in the busbars, leading to improved efficiency. Having thinner busbars may also provide increased flexibility, and hence may lead to higher reliability when manufacturing, for example by laser welding to make connections. Other examples described herein provide methods of construction of battery modules comprising a plurality of cells, battery cell carriers and/or busbars.

Figure 1 shows a battery pack 100 comprising an arrangement of battery modules 110a to 1 lOh. The battery pack 100 is suitable for an electric vehicle such as an electric car. In electric vehicles, battery packs may provide electrical energy to power one or more motors and may also provide at least some structural integrity to the vehicle. In this case, as will be described, having secure and reliable connections between battery modules 110a to llOh is desirable, so that the respective battery pack is resilient to stresses and can maintain secure operation and electrical connection to the motors in the electric vehicle during use.

As shown in Figure 1, the battery modules 110a to 1 lOh are fixed to a frame 120. The frame 120 holds the battery modules 110a to llOh in place in the arrangement. The battery modules 110a to 1 lOh may also be held in the arrangement by fixings between adjacent battery modules, for example, through the use of bolts or clasps. A similar arrangement of battery modules without the frame 120 is illustrated in Figure 2. The battery pack 100 has a first dimension 130 and second dimension 140, perpendicular to the first dimension. The first dimension 130 is greater than the second dimension 140. The first dimension 130 is parallel to a length of an electric vehicle comprising the battery pack 100 and the second dimension is parallel to a width of the electric vehicle. As will be described, the battery modules 110a to 11 Oh are arranged and connected such that an aggregate current flows in a direction parallel to the first dimension 130. Having the aggregate current flow parallel to the first 130, greater dimension allows the voltage to be summed across cell groups along a major dimension of the battery pack 100 to provide electrical power which may be used to drive an electric motor.

Referring to Figure 2, each battery module, such as battery module 110a, comprises a plurality of battery cells arranged into cell groups. The terms battery cell and cell are used interchangeably herein. The battery module 110a shown in Figure 2 has four cell groups 220a to 220d. However, battery modules more generally may have more or fewer cell groups than are shown in Figures 1 and 2. Actual battery cells are not shown in Figure 1 or Figure 2 but are shown later in Figures 4A to 8. The battery cells in each cell group 220a to 220d are electrically connected in a combination of series and parallel connections within their respective cell group, for example using busbars or other suitable electrical connection mechanisms, as will be described. More particularly, in the arrangement 200 of battery modules, each battery module 110a to 11 Oh is electrically connected to an adjacent battery module 110a to 1 lOh. In some examples, each cell group is electrically connected to at least one other cell group which is directly adjacent to the cell group on a directly adjacent battery module. For example, cell group 220a is electrically connected to a cell group 220e, and so on.

The arrangement 200 of battery modules shown in Figure 2 comprises eight battery modules. However, it is to be understood that the arrangement 200 may comprise any suitable number of battery modules. The exact number of battery modules in the arrangement 200 may depend on an intended use of the battery pack 100 as well as desired voltage and size (and capacity) of the cells and battery modules.

Figure 3 shows a view of a single battery module, for example battery module 110a of Figures 1 and 2, comprising a plurality of cell groups 220a to 220d. The battery module 110a comprises a support 320 having opposing first (upper) and second (lower) faces 320a, 320b on which, respectively, cell groups 220a/220b and cell groups 220c/220d are mounted. In the illustrative example of Figure 3, the support 320 is a cooling member comprising inlet and outlet ports 330a, 330b, fluidically coupled to respective ancillary inlet and outlet conduits 340a, 340b. The cooling member has internal ducts (not shown) through which cooling fluid can pass to cool the cooling member. The inlet 330a and outlet 330b ports are positioned conveniently in a channel on the upper face 320a of the cooling member between cell groups 220a and 220b. A corresponding channel is shown between cell groups 220c and 220d on the opposing, lower face 320b of the cooling member. In addition to providing a convenient location for the inlet and outlet ports 330a, 330b, the or each channel may be used for various functions including to mount the battery module 110a within a battery pack 100 and to route cables and other components connected to the battery module 110a. Where the battery module 110a is used in an electric vehicle, the or each channel may be used for the routing of components which may be used to operate an electric vehicle comprising the battery module 110a. Although referred to herein as a cooling member, it will be appreciated by a person skilled in the art that the support 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 support 320 can be thought of more generally as a heat transfer member. The support 320, irrespective of whether or not it performs the function of a cooling member, is constructed from a rigid material to carry the cell groups 220a to 220d. The support 320 may be made of any suitable material, for example, metallic materials such as aluminium, titanium, steel, or other suitably strong materials such as other carbon alloys or composites. The support 320 in this example is a planar member. In the present context, the support 320 may be referred to as ‘planar’ even if the surfaces of the faces 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 of the support. In the present example, the support 320 is also shown as being a generally regular, rectangular, plate-like member, supporting cuboid cell groups 220a to 220d. The cell groups 220a to 220d may be mounted to the support 320 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 support 320 may be formed to receive the cell groups 220a to 220d. For example, the support 320 may have at least one recess into which a cell or a cell group 220a to 220d may be received and mounted thereon. Cuboid cell groups as illustrated provide a desirable energy density in the cell group. However, in other examples, cell groups may have other shapes including regular or irregular polygons. In some examples, the shape of the cell groups may be dependent on a frame into which the battery modules are to be fitted, the shape of the frame being influenced, for example, by the shape and size of the respective vehicle in which the respective battery pack is to be used. The shape of the cell groups may not be the same for all cell groups. For example, some cell groups may be shaped such that they conform to the shape of adjacent cell groups when the battery module is held in the arrangement.

According to the present example, taking a battery module in isolation, the four cell groups 220a to 220d are electrically isolated from one another on the support 320. That is, there is no electrical connection between cell groups 220a to 220d in the battery module 110a. Electrical insulation may be disposed between each cell group 220a to 220d and the support 320 to electrically isolate the cell groups 220a to 220d. In other implementations, the support 320 itself may not be electrically conducting and may therefore naturally provide electrical isolation between cell groups 220a to 220d on opposing faces and between cell groups mounted on a common face.

Each cell group 220a to 220d comprises a positive terminal connection and a negative terminal connection. In Figure 3, the positive terminal connections 350a, 350b, 350d for respective cell groups 220a, 220b, and 220d can be seen. The negative terminal connections 360a, 360c, 360b for respective cell groups 220a, 220c and 220b can be seen. The positive 350a to 350d and negative terminal 360a to 360d connections are connectable to respective negative and positive terminal connections of adjacent battery modules. In the present disclosure, unless context dictates otherwise, references to positive and negative terminals may be reversed such that a current flow may be in the opposite direction to that which is described. In any case, terminal connections of adjacent battery modules are engaged physically and secured by appropriate means, such as bolts and/or any other suitable attachment mechanisms. In the present example, the positive and negative terminal connections 350a to 360d each comprise a tab, extending parallel to a plane of the support 320, to provide a convenient connection point for the respective cell groups 220a to 220d.

Figure 4A shows a simplified schematic diagram of an arrangement of battery cells 420 within a cell group, for example cell group 220a, according to an example. The cell group 220a comprises a two-dimensional array of battery cells 400. The array 400 has a major dimension, in the direction parallel to an x-axis in Figure 4A, and a minor dimension, in the direction parallel to a y-axis in Figure 4A. The minor dimension is perpendicular to and shorter than the major dimension. The array 400 comprises a plurality of sub-groups 410a to 41 Od of battery cells 420, each sub-group 410a to 41 Od in the array 400 comprising a plurality of parallel-connected cells arranged in a linear arrangement and spanning the major dimension. In Figure 4A, four sub-groups 410a to 410d are shown, although other numbers of sub-groups may be applied, such as six or more. The sub-groups 410a to 41 Od are distinguished from adj acent sub-groups 410a to 410d in Figure 4 A with the use of alternate white and hatched shading. The number of cells in each sub-group 410a to 41 Od may be identical across all sub-groups 410a to 410d or may differ. In some examples, a first set of the sub-groups of cells may comprise a first number of cells and a second set of the sub-groups of cells may comprise a second number of cells, wherein the first number of cells is different to the second number of cells. The sub-groups 410a to 41 Od are electrically connected to one another in series and arranged so that an aggregate current flows across the cell group 220a in a direction parallel to the minor dimension. Put another way, the battery cells 420 in a subgroup 410a to 41 Od are connected in parallel with the other battery cells 420 in the respective subgroup 410a to 41 Od and the subgroups 410a to 41 Od are connected in series with adjacent subgroups 410a to 410d. Having an aggregate current flow in a direction parallel to a minor dimension of the cell group 220a in a battery module 110a distributes the current across the length of the battery module.

Figure 4B shows the cell group 220a of Figure 4A in a perspective view where like reference numerals correspond to like features. The minor dimension, y, of the array of battery cells 400 in the cell group 220a is shorter than the major dimension, x, of the array of battery cells 400 in the cell group 410. The major dimension, x, of the array 400 is between two and four times greater than the minor dimension, y, of the array 400. For example, the major dimension, x, may be three times greater than the minor dimension, y. The battery cells 420 shown in Figure 4A and 4B are cylindrical in shape, however, the battery cells 420 in the battery module may be other suitable shapes. In some examples the battery cells 420 are elongate and may have any suitable cross section along the length. Figure 5 A shows a top-down view of cell group 220a, mounted on a support 320, which is part of battery module 110a. The cell group 220a is made up of sub-groups 410a to 410d. In this view, the arrangement also comprises a plurality of busbars 500a to 500c and current collectors 510a and 510b. The number of busbars will depend on the number of sub-groups 410a to 410d of cells and in some examples a battery module may comprise just one busbar. Each busbar 500a to 500c comprises a plurality of positive connection points (not shown), each connected to a respective positive terminal of a cell 420 in a first underlying sub-group, thereby to connect the cells of that subgroup in parallel. Each busbar 500a to 500c also comprises a plurality of negative connection points (not shown), each connected to a respective negative terminal of a cell 420 in a second underlying sub-group, which neighbours the first subgroup, thereby to connect the cells of that subgroup in parallel. In this way, each busbar connects the positive terminals of a first sub-group to the negative terminals of a second sub-group, such that the subgroups are connected in series with one another and such that an aggregate current flows in the respective battery module parallel to the minor axis of the cell group. Using a busbar to connect adjacent sub-groups of cells in this way provides a convenient and reliable way of electrically connecting adjacent sub-groups of cells. The current collectors 510a and 510b are for collecting current from a respective sub group 410a and 410d of cells that reside on a periphery of the cell group 220a. Each current collector 510a or 510b comprises an electrical conductor having an edge, acting as a busbar, spanning the major dimension of the respective cell group 220a, and comprises a plurality of connection points (not shown), each connected to a respective positive or negative terminal of a cell 420 in a respective underlying sub-group 410a or 410d, thereby to connect the cells of the subgroup 410a or 41 Od in parallel. Referring also to Figure 5B, the battery module 110a comprises first and second cell groups 220a, 220c, disposed on opposing faces of the support 320. First and second current collectors 510a, 510c are provided for collecting current from a sub-group of cells on a periphery of the respective first and second cell groups 220a, 220c. The current collectors 510a, 510c each comprise a converging region 530a and 530c which converges to a relatively narrower electrical contact 520a and 520c. In the example shown, the electrical contacts 520a and 520c each comprise a tab protruding from the respective current collector 510a and 510c, to provide a simple connection point with which electrical contacts of adjacent cell groups may be collocated and attached. The tabs may be attached to a further tab through the use of any suitable attachment mechanism. For example, bolts may be positioned through apertures (not shown) in the tabs, which may then be secured to a further tab of an adjacent cell group. The tab protrudes in a direction parallel to the minor dimension. In this way, the electrical contact 520a extends towards an adj acent cell group during assembly and so may be readily attached.

Each electrical contact 520a, 520b of the respective cell group 220a, one being a positive terminal and the other being a negative terminal, is used for electrically coupling the respective cell group 220a to another cell group or to an output of a battery module 110a or battery pack comprising the cell group 220a. In some examples, the converging region 530a may converge to more than one electrical contact, such as to two or even to three relatively narrower electrical contacts. Figure 6A shows a first alternative example of a current collector 600, comprising a converging region 610 which converges to three electrical contacts 620a, 620b, 620c. A second alternative current collector 630 is shown in Figure 6B, and comprises three converging regions 640,650,660, each with a respective electrical contact 670a, 670b, 670c. Such an arrangement may provide redundancy in the event of failure of one of the electrical contacts 670a, 670b, 670c, whilst still enabling the electrical contacts to extend across only a portion of the length of the current collector 630. Current collectors such as those described in relation to Figures 5A, 5B, 6A and 6B provide a reliable and secure way of electrically connecting adjacent cell groups of different battery modules to allow current to flow therebetween. Having the current collector 510a converge to a single electrical contact 520a, as shown in Figures 5a and 5b, simplifies the assembly of the battery module 110a and hence may increase the efficiency of production. Further, the single electrical contact 520a may increase the reliability of the connection between battery modules and reduce the number of potential points of failure. In the illustrative examples of Figures 5 A and 5B, the current collectors 510a and 510b on opposing peripheries of the cell group 220a are such that the respective battery module 110a can be electrically coupled to two battery modules, one on each side thereof. By connecting the cells 420 in this way, the thickness of the current collectors 510a and 510b may be reduced. Hence, current collectors 510a and 510b including the tabs may be at least partially flexible allowing manufacturing of the battery module 110a to be simpler while increasing resilience to torsional stresses. This may be of benefit when used in electric vehicles where these stresses may occur during operation of the vehicle due to factors such as uneven road conditions, high speeds, cornering, and other factors which may cause parts of the vehicle to flex. In the present example, the current collectors 510a and 510b are formed from a sheet of flexible and formable material such as, for example, copper. Returning to Figure 5B, each current collector 510a, 510b, and 510c extends in a direction orthogonal to the major and minor dimensions of the cell group. The orthogonal direction extends downwardly from an upper surface of the respective cell group 220a or upwardly from a lower surface of the respective cell group 220c. This may allow the current collectors 510a, 510b, and 510c, to have electrical connection points at positions which are readily connectable to other battery modules having similar and complementary connection points. The current collector 510a extends towards the support 320 in a direction orthogonal to the major and minor dimensions, x and y respectively. This allows the electrical contact 520a to be positioned close to a central plane of the battery module, defined by the support 320. This protects the electrical contact 520a of the current collector 510a when assembled and positions the electrical contact 520a in close proximity with the electrical contact 520c of the current collector 510c attached to the cell group 220c which is on the underside of the support 320. Such a symmetric arrangement, when applied to all battery modules and respective cell groups, simplifies the assembly process and, in particular, the connections and/or cable routing which may be performed between modules. In effect, cell groups (and respective battery modules carrying the cell groups) can be interconnected using a combination of busbars and current collectors largely without recourse to more-complex, and possibly less reliable, electrical connection schemes, such as, for example, comprising cables and wiring.

As each current collector 510a and 510b spans a length of the major dimension of a cell group 220a, having the current collectors 510a and 510b converge in a direction orthogonal to the major and minor dimensions of the cell group 220a allows contact points 520a and 520b of the current collectors 510a and 510b to be smaller than the length of the maj or dimension, while still allowing the current collectors 510a and 510b to transfer the aggregate current from across the major dimension to the electrical contacts 520a and 520b.

As shown in Figures 5 A and 5B, the electrical contacts 520a, 520b, 520c are offset from and either side of a central axis C located in a centre of the array of battery cells 400 parallel to the minor dimension thereof. Offsetting the positions of the electrical contacts 520a, 520b, and 520c allows the electrical contacts of adjacent cell groups, and cell groups on opposing faces, conveniently, to be electrically coupled to one another, or electrically isolated from one another, as the need dictates. In the example shown, the electrical contact 520a of the first current collector 510a is offset from the central axis C in a first direction (i.e. to the right of the central axis C as shown) parallel to the major dimension. The electrical contact 520c of the second current collector 510c is offset from the central axis in a second direction (i.e. to the left of the central axis C as shown), opposite to the first direction. Having opposing, offset electrical contacts 510a and 520c provides a desired electrical contact having a suitable size whilst maintaining electrical isolation between the first cell group 220a and the second cell group 220c. This also allows the current collectors 510a, 510b used on both sides of the cell group 220a to have the same form and hence only one type of current collector needs to be manufactured. This increases the scalability of the manufacturing process as fewer types of parts may be manufactured to produce the battery modules. Each electrical contact 520a, 520b, 520c may be offset from the support 320 in a direction orthogonal to the plane of the support 320. Alternatively, each electrical contact 520a, 520b 520c may be substantially coplanar with the support 620. In this way, adjacent battery modules may be attached with their respective supports being coplanar whilst providing a large contact area between adjacent electrical contacts.

In other examples, the current collectors 510a, 510b, and 510c do not comprise electrical contacts 520a, 520b, and 520c which extend from the respective current collector, 510a, 510b, and 510c respectively, but instead comprise a contact point. For example, there may be some other electrical attachment mechanism which may be used to connect adjacent cell groups. In some examples, electrical contacts on opposing current collectors attached to a single cell group may be different types of electrical connectors. For example a current collector, acting as a positive terminal, may comprise a male type connector, and a current collector acting as a negative terminal may comprise a female type connector, such that adjacent cell groups can be connected by attaching a respective negative terminal to a positive terminal of an adjacent cell group. This may also prevent the accidental connection of a positive terminal of a first cell group to a positive terminal of a second cell group.

Figures 7A and 7b are similar to the views of Figures 5A and 5B but show the full battery module 110a comprising two cell groups on each opposing face of a support 320. The arrangement is similar to the arrangement depicted in Figure 3, but without a battery cell housing.

Figure 8 shows a view of an arrangement 800 representing four banks of battery modules, such as the first four banks of battery modules 110a to 1 lOd of Figures 1 and 2. Figure 8 shows in more detail that the supports of the respective battery modules are coplanar, meaning in this case also that the upper and lower surfaces of the battery modules 110a to 1 lOd are co-planar. For clarity connections are omitted from Figure 8, although, as has been described, the cell groups are connected so that current flows (denoted by arrows P, Q, R and S) in a direction parallel to the minor dimension y of each cell group and along rows of neighbouring sub-groups parallel to the major dimension 130 of the battery pack. The connections are such that current flows in one direction, P, along the row of cell groups on the top and to the left of the support, and in the opposite direction, Q, along the row of cell groups below and to the left of the support. In this way, the rows of cell groups can be conveniently connected in series, via connections 830a, 830b, at the end of the battery pack 100. In other examples, the connections 830a, 830b may be located at the other end of the battery pack 100 as required. In the example shown, for instance, the upper left hand row of cell groups is connected in series with the lower left hand row of cell groups and the upper right hand row of cell groups is connected in series with the lower right hand row of cell groups. Alternatively, the upper left and right hand rows of cell groups may be connected in series with one another and the lower left and right hand rows of cell groups may be connected in series with one another. In either case, conveniently, all four rows of cell groups may be connected to one another in series.

Referring now to Figures 9A, 9B, 10A and 10B, Figure 9A shows a perspective view of at least part of a battery module 900 comprising a battery cell carrier 910, a plurality of battery cells 420 and a busbar 930 electrically connecting the plurality of battery cells 420. The battery cell carrier 910 comprises a plurality of openings, each opening accommodating a respective one of the plurality of cells 420.

As shown in Figures 10A and 10B, the plurality of battery cells 420 each comprise a first end 1010 and a second end 1020, with both a positive terminal 1040 and a negative terminal 1050 being located at the first end 1010. The openings in the battery cell carrier 910 are configured such that the first end 1010 of each cell 420 received in an opening is at least partially exposed through the battery cell carrier 910. This allows the positive 1040 and negative 1050 terminals of each battery cell to be connected to by respective busbars 930. In some examples, only a part of each of the positive 1040 and negative 1050 terminals of each cell 420 are exposed through the battery cell carrier 910 to prevent excess corrosion or dirt from affecting the cells 420. In other examples, the entire first ends of each of the battery cells 420 is exposed through the battery cell carrier 910 such that the busbar 930 can be readily connected to the terminals, using fixing features (as will be described) to locate the busbar 930. This allows the busbar 930 to be connected to the relevant cell terminals readily, reducing the risk of a poor connection. Having both the positive terminal 1040 and the negative terminal 1050 located on the first end 1010 of the cell simplifies construction of the battery module and requires busbars 930 to be located on only one side of the respective cell group.

The plurality of battery cells 420 in Figure 9A comprises first (depicted in white) and second (depicted hatched) parallel-connected banks of battery cells. The busbar 930 connects to the positive terminals of the first (white) parallel-connected bank of battery cells and to the negative terminals of the second (hatched) parallel-connected bank of battery cells.

Figure 9B shows schematically an end view (p, q) of the two parallel-connected banks of battery cells of Figure 9A. As shown in Figure 9B, the battery cell carrier 910 comprises at least one fixing feature 940 to locate the busbar 930 with respect to the battery cell carrier 910. While only one fixing feature 940 is visible, other examples may apply plural fixing features instead, for example spanning a major dimension of the battery cell carrier 910. The major dimension is defined in this example as a dimension of the battery module spanning the largest number of cells. Using a fixing feature 940 to locate the busbar 930 with respect to the battery cell carrier 910 ensures that the position of the busbar 930 is accurately defined relative to the location of the battery cells. The presence of the fixing feature 940 also means that the busbar 930 can be efficiently and accurately positioned for attaching the busbar 930 to the battery cells 420 during manufacture. The increased precision of the busbar location due to the presence of the fixing feature 940 in part also facilitates use of cells 420 which have both positive and negative terminals on a same end 1010 of the cell 420. Imprecise connections would invariably lead to short circuits occurring between the positive 1040 and negative 1050 terminals of individual cells 420. The fixing features 940 may comprise any suitable attachment mechanism for securing the busbar 930 and locating it with respect to the battery cell carrier 910. According to examples, fixing feature 940 comprises an upstanding projection on an outer surface of the battery cell carrier 910. The busbar 930 comprises a complementary fixing aperture 950, shown in broken lines in Figure 9B, to receive the fixing feature 940 and to facilitate alignment between the busbar 930 and battery cell carrier 910. Once assembled, the fixing feature 940 is deformed (for example using heat and/or pressure) and comprises a deformed part 960 (having an expanded width relative to the normal width of the fixing feature) to fix the busbar 930 and the battery cell carrier 910 together. Returning to Figures 10A and 10B, the battery cell 420 comprises an annular groove 1030 around an upper periphery of the battery cell 420 and the positive 1040 and negative 1050 terminals of the battery cell are coplanar. However, in other examples, one of the positive 1040 or negative 1050 terminals may be raised or recessed in comparison to the other of the positive or negative terminals, and busbars may be configured accordingly. In the example shown, the negative terminal 1050 forms a part of an outer casing of the battery cell 420. In other implementations, the terminals may be reversed such that the positive terminal forms a part of the outer casing of the cell 420. Alternatively, the outer casing of the cell 420 may comprise insulating material such that the positive 1040 and negative 1050 terminals are only exposed on a top side of the cell 420 at the first end 1010.

Figure 11 shows a perspective view of a portion of a battery cell carrier 1100, according to another example, which is suitable for use with cell groups of the kind that are illustrated in any of Figures 1 to 8. The battery cell carrier 1100 comprises a plurality of openings 1140, each opening for receiving a respective one of a plurality of battery cells. Fixing features, such as fixing features 1110a, 1110b, and 1110c, are included as upstanding projections on an upper surface 1120a of the battery cell carrier 1100. The upstanding projections engage with respective busbars as the battery modules are assembled, so as to align the busbars accurately with the battery cell carrier and hence with the battery cells 420, and to prevent the busbars from contacting incorrect terminals of the battery cells 420.

The upstanding projections 1110a, 1110b, 1110c are made from a deformable material and are deformable by the application of heat and/or pressure to secure the respective busbar to the battery cell carrier 1100. Once deformed, the upstanding projections 1110a to 1110c secure the busbars to the battery cell carrier 1100.

Deformable fixing features 940 may be made from suitable polymers or metallic materials. Alternatively, the fixing features 940 may comprise fasteners or other mechanisms which can attach to the busbar. The fixing features 940 may be made of semi-rigid or flexible material and may be shaped such that they provide a secure press fit when engaged with the busbar. For example, the fixing features 940 may have a hemispherical end and a cut away below the hemispherical end. Once the hemispherical end has been pressed into a corresponding fixing aperture 950 in the busbar, at least part of an underside of the hemispherical end may engage with a surface of the fixing aperture and prevent the busbar from being removed.

Returning to Figure 11, the battery cell carrier 1100 is for holding a plurality of battery cells 420 and comprises the upper surface 1120a and a lower surface 1120b. The battery cell carrier 1100 comprises a plurality of walls 1130 extending between the upper surface 1120a and the lower surface 1120b. Each of the plurality of walls 1130 at least partly defines an opening 1140 for receiving a respective one of the plurality of battery cells 420. Each opening 1140 in the battery cell carrier 1100 is configured to accommodate a respective cell 420 passing therethrough. Each of the plurality of walls 1130 is adapted to lie adjacent to a corresponding cell wall of a respective battery cell 420 when the cells 420 are received in the respective openings. A wall 1130 of each opening comprises an annular ridge 1150, at least partly defining the opening 1140, near to or at the lower surface 1120b. The annular ridge 1150 of each wall 1130 is configured to contact and hold a battery cell 420 received in the respective opening in use, so that the wall 1130 is spaced from the respective cell wall by an amount at least equal to the width of the annular ridge 1150.

The battery cell carrier 1100 comprises a rigid material which can provide support to the battery cells 420 which are mounted therein. The battery cell carrier 1100 may comprise a material which is softer than a surface material of the cells 420 such that, during manufacture and use, the risk of the battery cell carrier 1100 damaging the cells 420 is reduced. For example, the battery cell carrier 1100 may be made of a hardened plastic or any other suitable material. In some examples, the battery cell carrier 1100 is at least partially flexible and/or resilient such that, when a cell 420 is inserted into a respective one of the openings, a respective annular ridge 1150 engages with and deforms in accordance with the cell 420. The annular ridge 1150 is sufficiently rigid such that it continues to engage with the cell 420 and at least partially holds the cell 420 in place, for example by friction. The annular ridge 1150 provides a secure fit between a cell 420 accommodated in a respective one of the openings 1140 and the battery cell carrier 1100, thereby preventing slippage of the cell 420 and increasing the stability. According to the present example, the annular ridge 1150 circumscribes the respective opening 1140 and engages with an entire periphery of the cell 420.

In some examples, battery cells 420 may be secured within the battery cell carrier 1100 by the use of a suitable adhesive. Adhesive contained in the openings 1140 contacts cell walls of respective battery cells and holds the battery cells in the battery cell carrier 1100. In this case, the annular ridge 1150 conveniently prevents leakage of adhesive down the respective battery cell 420, below the lower surface 1120b of the cell carrier 1100 and towards the second end of the cell 420.

The battery cell carrier 1100 comprises recesses 1160 in the upper surface 1120a thereof for receiving adhesive. In the example shown, the battery cell carrier 1100 is planar and the lower surface 1120b is generally flat.

The walls 1130 comprise apertures between respective openings 1140 and the recesses 1160, such as aperture 1170. Each aperture 1170 fluidically links a respective one of the openings 1140 to the recess 1160, such that during adhesive insertion adhesive flows from the recess 1160, through the apertures 1170 and into the openings 1140.. The aperture 1170 has a boundary extending downwardly from the upper surface 1120a. Adhesive that flows into the opening 1140 flows around a cavity or region between the wall 1130 and the cell wall of a battery cell 420 that is received in the respective opening 1140. The adhesive fills the region from a lower bound defined by the annular ridge

1150 and penetrates the annular groove 1030 of the battery cell 420. The recess 1160 may be said to be in fluid communication with the cell wall of a battery cell 420 received in each respective opening in use. In the example shown in Figure 11, the recess 1160 is configured such that during adhesive introduction, the adhesive can flow through three apertures, including aperture 1170, and onto walls of three respective battery cells 420 accommodated in their respective openings in a hexagonal, close-packed arrangement. However, it will be appreciated that in other examples there may be only one aperture per recess. Where a single recess is configured to allow the flow of adhesive through a plurality of apertures, an adhesive application process may be simplified as fewer separate injection nozzles may be used to insert adhesive into the cell carrier 1100. This may increase the speed and efficiency of manufacturing. Having recesses 1160 and apertures 1170 arranged in this way, and given a sufficiently-free- flowing adhesive, allows gravity to introduce the adhesive and fix the cells 420 in the fixed arrangement, rather than requiring a more complex, pressure-injection process. In the present embodiment, the annular grooves 1030 of battery cells 420 are located such that they are at or below the level of the recess 1160. This may result in an increased flow rate of adhesive and/or improved bonding due to the extra surface area provided by the annular grooves 1030.

The formation of a cavity or region between the wall 1130 and the cell wall of a battery cell 420 provides a relatively large surface area of the battery cell 420 and cell carrier 1100 for adhesive to make contact with and hence securely fix the cell 420 within the battery cell carrier 1100. The ridge 1150, which is arranged to contain adhesive within the cavity, ensures that adhesive is not wasted by leakages and the cells 420 are not covered in excess adhesive, which may affect the thermal control and/or efficiency of the cells 420, and thereby reduces cost and weight.

As indicated, the adhesive, before setting, is in the form of a fluid such that the adhesive can be introduced into the recesses 1160 using a suitable applicator. The adhesive therefore flows under the force of gravity. Once applied, the adhesive begins to set and after a certain period the adhesive forms a solid, which fixes and/or secures parts of the cell carrier and cells 420 which are in contact with the adhesive. The adhesive may have other properties such as thermal conductivity or, alternatively, may provide thermal insulation. In some examples, when set, adhesive may be disposed within an opening 1140 as well as in a respective aperture 1170 and/or recess 1160.

In some examples, busbars (not shown), which may be affixed to the foregoing cell carrier 1100, may comprise at least one adhesive insertion aperture. The or each adhesive insertion aperture is aligned with a respective recess 1160, for example by the arrangement of fixing features 1110a to 1110c. This arrangement allows adhesive to be introduced into the recesses, to secure the cells 420 in the cell carrier 1100, once the busbar is located with and/or electrically connected to respective cells 420. The battery cell carrier 1100 may additionally comprise at least one mounting feature (not shown) for battery management system circuitry. Battery management system circuitry may be located with the battery module to which it relates and may monitor and/or control one or more parameters of the battery module, including for example, temperature, charge capacity, output current and/or voltage, or remaining charge. Battery management circuitry may comprise any number of sensors including but not limited to, thermometers, voltmeters, ammeters, ohmmeters, accelerometers, and any other suitable sensors. The battery management circuitry may also comprise at least one controller, comprising any suitable combination of hardware and software for controlling one or more parameters of the battery module. Figure 12A shows a top down view of an example battery cell carrier 1100 retaining or holding a plurality of cells 420 in their respective openings. In some implementations, at least one of the openings 1200 in the battery cell carrier 1100 is a dummy opening configured to obstruct the insertion of a cell 420 therethrough. The dummy opening 1200 is located adjacent to, and in fluid communication with, a recess. A dummy opening may be used to maintain consistent adhesive fluid characteristics during an adhesive injection process. The consistency and behaviour of the adhesive fluid may be tightly controlled and so in areas where the recesses are connected to fewer apertures, and hence in fluid communication with fewer cell walls, the flow dynamics of the adhesive may be negatively affected. Consequently, a dummy opening 1200 may be used to maintain adhesive flow characteristics in these regions.

Figure 12B shows a perspective view of the battery cell carrier 1100 and the plurality of cells 420 shown in Figure 12A. Figure 12B shows the fixing features, such as fixing feature 1110a. A further fixing feature 1210 is shown on a periphery of the cell carrier and is used for locating a current collector in relation to a respective subgroup of the cells 420.

Figure 13 shows a simplified schematic diagram of an alternative battery cell carrier 1300 according to an example. In this example, the battery cell carrier 1300 does not comprise fixing features for locating a busbar and recesses 1310 are only in fluid communication with two openings 1320, 1330 via respective apertures 1340, 1350 in the walls, such as wall 1360. Similarly to that shown in Figure 11, the battery cell carrier 1300 comprises an upper surface 1370 and a lower surface 1380, wherein the recess 1310 is in the upper surface.

Figure 14 shows the battery cell carrier of Figure 13 with a plurality of cells 420, for example cells 420, received in respective openings 1320. The annular grooves of the battery cells 420 (not shown in this Figure) are configured to hold adhesive inserted via the respective apertures 1340, 1350 in the walls 1360. When a battery cell 420 is inserted into an opening 1320 in the battery cell carrier 1300, the annular groove may be positioned above an annular ridge 1390 in the wall 1360, towards the aperture 1340. In this way, the adhesive may fill the annular groove 1030 which provides greater surface area on the surface of the cell 420 with which to bond. Additionally, in this and in other examples, the annular groove 1030 provides greater resiliency to loads imparted on the cell 420 or battery cell carrier 1300.

Figure 15 shows a flow chart of a method 1500 of assembling a battery module comprising a battery cell carrier and a plurality of battery cells 420 according to an example. The battery cell carrier is a battery cell carrier according to the examples described herein. At block 1510, the method 1500 comprises providing a plurality of battery cells 420. At block 1520, the method 1500 comprises providing a battery cell carrier.

At block 1530, the method 1500 comprises inserting each of the plurality of battery cells 420 into a respective one of the openings for accommodating the battery cell 420. At block 1540, the method 1500 comprises introducing adhesive to the recess so that the adhesive flows from the recess, through the apertures and into the openings, and such that, when set, the adhesive holds the plurality of cells 420 in the battery cell carrier. Any of the example battery modules described herein may be a battery module for an electric vehicle.

In an example, there is provided a battery pack comprising a plurality of battery modules according to any examples described herein. The battery pack may be a battery pack for an electric vehicle comprising a frame. The battery pack may form part of the shape and/or structure of the electric vehicle. In an example there is provided an electric vehicle. For example, Figure 16 shows a schematic side view of an electric vehicle 1600 comprising a battery pack 1610 disposed in the electric vehicle 1610. The battery pack 1610 is disposed towards a lower side of the electric vehicle 1600, for example, in order to lower a centre of mass of the electric vehicle 1600. Figure 17 shows a schematic, top-down, view an underside of an electric vehicle 1700 according to an example. The electric vehicle 1700 comprises a front electric drive unit 1710 and a rear electric drive unit 1720 for delivering power to at least one driving wheel 1730 of the electric vehicle 1720. The vehicle 1700 comprises a battery pack 1740, which is located between the front and rear electric drive units 1710, 1720. The front and rear electric drive units 1710, 1720 in this example comprise invertors for converting DC battery current into AC current to be delivered to traction motors. In the illustrated embodiment, the battery pack 1740 comprises an electrical connection 1750 for connecting the battery pack to the rear electric drive unit 1720. The battery pack 1740 may also have an electrical connection with the front drive unit 1730. In some examples, the battery pack 1740 is arranged such that a battery input/output 1760 is located towards the front electric drive unit 1710 of the electric vehicle 1700 and the electrical connection 1750 extends from the battery input/output 1760 and along a passage to the rear electric drive unit 1720. The electrical connection 1750 is connected to an inverter of the rear electric drive unit 1720. In other examples, an electrical connection connecting the input/output 1760 of the battery pack 1740 to the front electric drive unit 1710, or to a charging port of the electric vehicle 1700, may extend along a passage of the battery pack 1740. In further examples, the battery input/output 1760 may be located at any other location on the battery pack 1740, such as towards a rear electric drive unit 1720 of an electric vehicle 1700 in which it is employed.

The above embodiments are to be understood as illustrative examples of the invention. Further embodiments of the invention are envisaged. It is to be understood that any feature described in relation to any one embodiment 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 embodiments, or any combination of any other of the embodiments. 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.