Patent Description:
Battery electric (BEV) and hybrid-electric (HEV) vehicles require significant electrical energy storage if they are to become usable by the broader population. In parallel with the development of cell chemistries that will give higher power and higher energy capability, the configuration of the "non-cell" components and systems should be optimised, thus reducing the mass and packaging impact to vehicles during the switch to electrical energy storage.

Small format cylindrical battery cells (e.g. <NUM>, <NUM> or <NUM> format cells) have some disadvantages, particularly the large quantity required to achieve high capacity. This leads to a large number of mechanical and electrical connections, and complex containment strategies.

Such small format cells also have significant advantages, such as the packaging adaptability and the flexibility to achieve the required system voltage and capacity by choosing the size of the "parallel" groups and the length of the "series strings" to give the desired configuration.

It has been observed that each supplier's manufacturing process drives differing tolerances into these "standard" formats, such that an <NUM> cell that should nominally be <NUM> diameter and <NUM> long may in reality be a slightly different length or diameter.

There is a desire for a cell mounting system that maintains the flexibility offered by the choice of small-format cylindrical cells whilst also decreasing the "overhead" associated with their use, giving a smaller, lighter and less expensive solution for their containment into a battery pack.

Very limited prior art exists for the application of these smaller-format cylindrical cells into batteries of large capacity, with the most relevant being that of Tesla Inc. That application uses an <NUM> cell within a "sandwich" type construction of mouldings above and below. It does not allow for the degree of flexibility required (within the detail of the cell support) if cells from a range of manufacturers are to be accommodated. An example of a Tesla Inc. battery support arrangement may be found in, for example, <CIT>. The documents <CIT>, <CIT> and <CIT> disclose modular battery carriers.

According to the present invention there is provided a carrier element for a plurality of cylindrical battery cells, the carrier element comprising a base and at least one upstanding wall located on an edge of the base; said at least one wall extending generally perpendicularly with respect to the base; wherein the base is provided with a plurality of open bottomed wells each configured to receive a single cylindrical battery cell, wherein each well is provided with first and second resilient alignment means arranged to bias a cell located within a well in mutually perpendicular directions.

The alignment means, in use, act to locate a battery cell within a well. The battery cell is both axially and radially located within the well, and thus manufacturing tolerances in the battery cell dimensions can be compensated for. The alignment means can also compensate for differences between the battery cell dimensions of different manufacturers products. The open bottom of each well permits access, in use to the anode or cathode of a battery cell. The alignment means are non-conductive and thus do not form electrical connections with battery cells received within the open bottomed wells.

The first resilient alignment means may be arranged to bias a cell in a direction substantially perpendicular to the plane of the base, and the second resilient alignment means may be arranged to bias a cell in a direction substantially parallel to the plane of the base.

The first resilient alignment means may be formed integrally with the carrier element. In one embodiment of the invention the first resilient alignment means may comprise a sprung finger located within the open bottom of the well. More preferably the first resilient alignment means may comprise a plurality of sprung fingers located within the open bottom of the well. The or each sprung finger may include a contact projection which in use, contacts an end of a cell located within the well. In one embodiment of the invention, each well is provided with two sprung fingers which are positioned on opposing sides of the open bottom of the well. In such an embodiment it will be understood that the fingers, in use, contact radially outer region of the end of a cylindrical battery cell. It will thus be appreciated that the radially inner region of the end of the cylindrical battery cell, corresponding to the positive or negative terminals of the battery, are readily accessible and not covered or occluded by the fingers.

The second resilient alignment means may be formed integrally with the carrier element. More specifically the second resilient alignment means may comprise a sprung finger located at the side of the well. More preferably second resilient alignment means may comprise a plurality of sprung fingers located at the side of the well. The or each sprung finger may include a contact projection which in use, contacts a side of a cell located within the well.

The carrier element may be provided with formations configured to permit the adjacent connection of like carrier elements. Multiple carrier elements may thus be connected together in order to accommodate a desired number of battery cells.

The formations may include a barbed projection of a well of the carrier element and a complementary engagement surface of another well of the carrier element. The barbed projection is preferably resilient.

The formations may further include interengageable projections and recesses of the base of the carrier element. More specifically the projections and recesses of the base may have a dovetail configuration.

The formations may further include interengageable projections and recesses of the walls of the carrier element.

The base of the carrier element may include an aperture configured to receive a thermistor and thermistor wiring there through. The base may further include a projection for the mounting of a thermistor. Such a projection may be positioned between adjacent wells of the base.

The ends of the walls which are distal to the base are preferably configured to engage walls of a like carrier element when said like carrier element is inverted and mated to the carrier element. In such an embodiment one of the walls may be provided with a ledge against which a wall of an inverted carrier element can abut, in use.

The carrier element may be of unitary construction and formed from plastic by injection moulding.

According to another aspect of the present invention there is provided a carrier for a plurality of cylindrical battery cells, the carrier comprising first and second carrier elements as described above wherein the first and second carrier elements are arranged such that the distal ends of the walls of the carriers abut one another.

The distal ends of the walls of the first and second carrier elements may at least partially overlap.

According to another aspect of the present invention there is provided a battery arrangement comprising a carrier as described above and a plurality of cylindrical battery cells, wherein the cylindrical battery cells are located between opposing wells of the first and second carrier elements.

The first and second carrier elements are preferably fixed to one another in a non-separable manner. The first and second carrier elements are preferably connected to one another at the overlap of the walls, for example by welding. The walls may be provided with recesses configured to receive welding apparatus for the purpose of welding the first and second carrier elements to one another.

The battery arrangement may optionally be provided with a battery cooling arrangement. Such a battery cooling arrangement may comprise at least one flexible bladder passing around at least some of the battery cells, said bladder being in fluid communication with manifold means provided at opposing ends of the bladder. In an alternative embodiment cell cooling may be achieved by the circulation of air between the cells.

The battery arrangement may further include electrical connection means which overlie the bases of the first and second carrier elements and contact the ends of the battery cells through the open bottoms of the wells. The electrical connection means may comprise a substantially planar electrically conductive member having a plurality of sprung projections which, in use, are aligned with and extend into the open bottoms of the battery cell wells.

The invention gives a very flexible approach to the support of small-format cylindrical cells whereby they can be used in virtually any series-parallel arrangement and a module containing the cells can be used in any orientation (horizontal or vertical), whether actively cooled (air or liquid) or not.

This invention specifically allows for the assembly of multiple cylindrical cells into a common carrier, whereas much of the prior art found describes carrier mouldings for a single cell (which is wasteful of time in assembly, space and weight).

Embodiments of the present invention will now be described with reference to the accompanying figures in which:.

Referring firstly to <FIG> there is shown a carrier element generally designated <NUM>. The carrier element <NUM> includes a generally planar base <NUM> and opposing side walls <NUM>,<NUM> which extend substantially perpendicularly from the plane of the base <NUM>.

The base <NUM> is provided with a plurality of wells <NUM> into which, in use, cylindrical battery cells are receivable. In the embodiment shown the carrier element <NUM> is provided with ten wells <NUM> which are arranged in a <NUM> cell by <NUM> row array. The carrier <NUM> is thus able to accommodate ten battery cells. The adjacent pairs of wells <NUM> are offset so as to minimise the space required for the ten cells. It will be appreciated that the <NUM> cell by <NUM> row array is shown by way of illustrative example only and alternative layouts for the wells <NUM> are possible. For example, the carrier element <NUM> may be provided with a <NUM> cell by <NUM> row array, a <NUM> cell by <NUM> row array or a <NUM> cell by <NUM> row array.

The wells <NUM> are open bottomed and include an aperture <NUM> which allows access to the interior of a well <NUM> from the opposing side of the base <NUM>.

Each well <NUM> is provided with a first alignment means comprising pair of fingers <NUM> which extend at least partially across the aperture <NUM> of the well <NUM> from opposing sides of the aperture <NUM> of the well. Each finger <NUM> is inclined with respect to the plane of the base <NUM> and into the well <NUM>. Each finger <NUM> is provided, at the end which is distal to the side of the well <NUM> from which the finger <NUM> projects, with a projection <NUM>. The projections <NUM> are, in use, positioned to contact the end of a battery cell located within the well <NUM>. The spacing of the fingers <NUM> is such that, in use, the projections <NUM> contact the radially outer region of the end of the battery cell and thus leave the radially inner region of the end of the battery cell freely accessible. This can be readily seen in, for example, <FIG>.

Each well <NUM> is further provided with a second alignment means comprising a second pair of fingers <NUM> which extend in a direction substantially perpendicular to the plane of the base <NUM>. Each second finger <NUM> is provided with a projection <NUM> which, in use, are positioned to contact the side of a battery cell located within the well <NUM>.

In the embodiment described in the figures the carrier element <NUM> is of a unitary construction and may be formed from plastic, for example, by injection moulding. In an alternative embodiment, the carrier <NUM> may be of a multipart construction that requires assembly. In such an embodiment the base <NUM> may be separate from the walls <NUM>,<NUM> and the carrier element <NUM> may thus require assembly before the fitment of battery cells thereto. The base <NUM> and walls <NUM>,<NUM> may be formed from plastic by a moulding operation. Assembly may require connection of the base <NUM> and walls <NUM>,<NUM> by, for example, adhesive or welding.

The carrier element <NUM> is configured so as to be connectable to an adjacent carrier element 10a as illustrated in <FIG>. Connection of adjacent carrier elements <NUM>,10a is achieved by the provision of a plurality of complementary connection formations.

<FIG> illustrate a first of the aforementioned connection formations. The central three wells <NUM> on one side of the carrier element <NUM> are provided with barbed projections <NUM>. The central three wells <NUM> on the other side of the carrier element <NUM> are each provided with a complementarily shaped cut out <NUM> against which the barbed projections <NUM> can abut. Depending upon the configuration of the carrier <NUM>, for example the number of cells it is intended to carry it will be under stood that a different number and combination of wells <NUM> may be utilised for the connection formations.

<FIG> show a second of the aforementioned connection formations. The central and outer two wells on one side of the carrier element <NUM> are provided with dovetail projections <NUM>. The central and outer two wells on the other side of the carrier element <NUM> are provided with complementarily shaped dovetail recesses <NUM>. Depending upon the configuration of the carrier <NUM>, for example the number of cells it is intended to carry it will be under stood that a different number and combination of wells <NUM> may be utilised for these connection formations.

<FIG> show a third of the aforementioned connection formations. Each wall <NUM>,<NUM> on one side of the carrier element <NUM> is provided with a cylindrical projection <NUM>. The walls <NUM>,<NUM> on the opposing side of the carrier element <NUM> are provided with a complementarily shaped recess <NUM>.

The connection formations may be utilised to connect multiple carrier elements <NUM> to form a channel or tray <NUM> as shown in <FIG>.

Once the desired length of tray <NUM> has been assembled, then appropriately configured end pieces <NUM>,<NUM> can be fitted (<FIG>). The end pieces <NUM>,<NUM> have appropriately configured features which connect to the previously described connection formations. As shown in <FIG>, the end pieces <NUM>,<NUM> further include connection apertures <NUM> for a battery cell cooling arrangement (described below) and captive metal inserts <NUM> to allow mounting of the tray <NUM> to, for example, other trays <NUM>. It will be appreciated that other features may be used in addition to, or as an alternative to, the captive metal inserts <NUM> to enable mounting of the trays <NUM>.

In an alternative embodiment, the end pieces <NUM>,<NUM> may be incorporated into carrier elements <NUM> so as to form end carrier elements.

After fitment of the end pieces <NUM>,<NUM>, then a plurality of cylindrical battery cells <NUM> can be fitted to the wells <NUM> as shown in <FIG> and <FIG>. In the embodiment shown, half of the cells <NUM> have their cathode uppermost and the other half of the cells have their anode uppermost. This configuration is not intended to be limiting and it will be appreciated that other cell configurations are possible.

Once the cells <NUM> have been inserted into the wells <NUM> then, optionally, a cell cooling arrangement <NUM> may be fitted. The cell cooling arrangement comprises a pair of cooling fluid manifolds <NUM> between which are connected a plurality of flexible bladders <NUM>. The bladders <NUM> are fitted between the cells <NUM> and the manifolds <NUM> mounted to the connection apertures <NUM> of the end pieces <NUM>,<NUM>. In use, liquid can be circulated through the manifolds <NUM> and bladders in order to regulate the temperature of the cells <NUM>.

Whether the cell cooling arrangement <NUM> is included or not, the cells <NUM> are encapsulated between a second tray <NUM> of carrier elements <NUM> as shown in <FIG>.

The trays <NUM>, <NUM> thereafter require connection to one another to define a battery cell carrier generally designated <NUM>. Connection of the trays <NUM>,<NUM> may be effected by a number of means including, for example, adhesive, mechanical fasteners and straps. More preferably the trays <NUM>, <NUM> may be connected by ultrasonic welding. To assist with such welding, the ends of the walls <NUM>, <NUM> which are distal to the base <NUM> of each carrier element <NUM> are configured to overlap as shown in <FIG> and <FIG>. As can be seen from <FIG> and <FIG>, one of the walls <NUM> is provided with a ledge <NUM> against which the distal most edge <NUM> of the other of the walls <NUM> abuts when two carrier elements <NUM>, or trays <NUM>, <NUM>, are positioned relative to one another so as to encapsulate a plurality of cells <NUM>. Due to the different configuration of the distal ends of each wall <NUM>, <NUM>, it will be appreciated that the aforementioned overlap occurs on both sides of the carrier element <NUM> and tray <NUM>,<NUM> pairs.

The wall <NUM> having the ledge <NUM> is provided with additional features which assist in the provision of an ultrasonic weld between overlapping carrier elements <NUM>. The wall <NUM> is provided on the side that is opposite to the wells <NUM> with a blind recess <NUM> which is sized to receive the end of an ultrasonic welding apparatus. The ledge <NUM> is further provided with a plurality of spaced projections <NUM> which resist movement of the distal most edge <NUM> of the other of the walls <NUM> away from the ledge <NUM> when force is applied to the recess <NUM> by an ultrasonic welding apparatus.

Electrical connection of the cells <NUM> within the battery cell carrier <NUM> is achieved by the provision of external bus bars <NUM>,<NUM>,<NUM>. Each bus bar <NUM>,<NUM>,<NUM> is formed from a planar member <NUM> of electrically conductive material. Each planar member <NUM> is provided with a plurality of projections <NUM> which align with the apertures <NUM> in each well <NUM>. The projections are configured to contact either the anode or cathode of a battery cell <NUM> located within a well <NUM>. The projections <NUM> of each bus bar <NUM>,<NUM> may be formed integrally with each planar member <NUM>. As noted above, the location of the sprung fingers <NUM> in each well <NUM> ensures that the projections <NUM> can readily contact the anodes and cathodes of the battery cells.

In an alternative embodiment each bus bar <NUM>,<NUM>,<NUM> may be of a laminated construction. In such an embodiment each bus bar <NUM>,<NUM>,<NUM> may comprise a first substantially planar member of an electrically conductive material having the projections <NUM> and a second planar member of an electrically conductive material overlying the first. The first planar member may have a thickness that is less than that of the second planar member so as to assist with formation of the projections <NUM>. The lesser thickness of the first planar member further enables the projections <NUM> to be formed with a degree of flexibility and resilience. This flexibility and resilience ensures that each projection <NUM> reliably contacts the anode or cathode of an underlying battery cell <NUM>.

Where the bus bars <NUM>,<NUM>,<NUM> are of a laminated construction, then members forming the laminated structure may be connected together, for example by welding.

The projections <NUM> of the bus bars <NUM>,<NUM>,<NUM> may each, in use, be fixed in an electrically conductive manner to the anode or cathode of an underlying battery cell <NUM>. The fixing of the projections <NUM> may be achieved, for example, by pulsed arc welding or laser welding.

To effect connection of the bus bars <NUM>,<NUM>,<NUM> to the battery cell carrier <NUM>, the bus bars <NUM>,<NUM>,<NUM> are provided with a plurality of apertures <NUM> which align with corresponding apertures <NUM> of the base of each carrier element <NUM>. Mechanical fasteners <NUM> can then be located through the aligned apertures <NUM>,<NUM> in order to connect the bus bars <NUM>,<NUM>,<NUM> to the battery cell carrier <NUM>.

The base <NUM> of each carrier element <NUM> is further provided with an aperture <NUM> through which a temperature sensor (not shown) can be routed. The temperature sensor may be located against a cell <NUM> or, alternatively, mounted to a dedicated projection <NUM> of the carrier element <NUM>.

Referring now to <FIG> there is shown an alternative embodiment of a carrier element generally designated <NUM>. Features common to the embodiment of the invention described with reference to <FIG> are identified with like reference numerals prefixed with "<NUM>". The carrier element <NUM> has a broadly similar configuration to the carrier element <NUM> described with reference to <FIG>. More specifically, the manner in which battery cells are positioned and retained in a carrier element <NUM>, and the manner in which adjacent and opposing carrier elements <NUM> can be fitted together and connected to one another is equivalent to that described with reference to <FIG>. The following description of <FIG> thus focuses upon features which differ from the carrier element <NUM> of <FIG>.

Reference is first made to <FIG> and <FIG>. As before, the carrier element <NUM> includes a base <NUM> having a plurality of wells <NUM> and opposing side walls <NUM>,<NUM>. Whereas in the carrier element <NUM> of <FIG> is provided with opposing walls <NUM>,<NUM> of substantially equal height and width, the walls <NUM>,<NUM> are dissimilar in size and configuration. The carrier element <NUM> is provided with a first wall <NUM> which extends for substantially the entire width of two wells <NUM> the base <NUM> and a second wall <NUM> which has a width that is less than that of the base <NUM> and first wall <NUM>. The second wall <NUM> is located at the interface of two wells <NUM> of the base <NUM>. Furthermore, the first wall <NUM> extends from the base <NUM> to a significantly greater height than that of the second wall <NUM>.

The end <NUM> of the first wall <NUM> which is distal to the base <NUM> is provided with a slot <NUM> which is surrounded by a recess <NUM>. The recess <NUM> is sized and shaped to accommodate the second wall <NUM> of another carrier element <NUM>. The depth of recess <NUM> is approximately equal to the thickness of the second wall <NUM>. The second wall <NUM> when received in the recess <NUM> of a first wall <NUM> lies flush with the first wall <NUM> (see <FIG>).

As can be seen in <FIG>, the second wall <NUM> is provided with a rib <NUM> which is connected to a flange <NUM>. The rib <NUM> extends substantially perpendicular to the plane of the second wall <NUM>. The flange <NUM> is aligned so as to lie substantially parallel to the plane of the second wall <NUM>. The rib <NUM> of the second wall <NUM> is received in the slot <NUM> of the first wall <NUM> when two carrier elements <NUM> are fitted together (see <FIG>). The second wall <NUM> is provided with a plurality of blind recess <NUM> which, in a similar manner to that described above, are configured to receive the end of an ultrasonic welding apparatus.

The arrangement of rib <NUM> and recess <NUM> ensures that, when two carrier members <NUM> are fitted together as shown in <FIG>, relative axial movement between the carrier members <NUM> is prevented.

Referring now to <FIG>, there is shown an additional alignment feature of the carrier element <NUM> which is utilised when adjacent carrier elements <NUM> are fitted together. On opposing sides of each wall <NUM>,<NUM> the base <NUM> is provided with an integrally formed pin <NUM> and a projection <NUM> having a complementarily shaped hole <NUM>. As can be seen in <FIG> the pin <NUM> is received in the hole <NUM> when two adjacent carrier elements <NUM> are fitted together.

Referring now to <FIG> a feature of the base <NUM> of the carrier element <NUM> is shown. Provided on the opposing side of the base <NUM> to wells <NUM> there are integrally formed a plurality of pins <NUM> which, in use, are utilised to locate and connect a bus bar <NUM> to the carrier element <NUM>. In use, the pins <NUM> are received in corresponding apertures <NUM> of the bus bar <NUM>. The length of each pin <NUM> is greater than the thickness of the bus bar <NUM>, with the result that the ends of the pins <NUM> stand proud of the bus bar <NUM> (see <FIG>). The ends of the pins <NUM> can thereafter be deformed to connect the bus bar <NUM> to the carrier element <NUM> (see <FIG>).

<FIG> shows further detail of the first wall <NUM> of the carrier element. More specifically, <FIG> illustrates the presence of through apertures <NUM>,<NUM> in the first wall <NUM>. The larger diameter aperture <NUM> is configured to receive a mounting stud (not shown) of a structure (for example a vehicle chassis or subassembly) to which a cell carrier formed from a plurality of carrier elements <NUM> is intended to be mounted. The smaller diameter apertures <NUM> are configured to receive upstands of one or more printed circuit boards (both not shown).

<FIG> shows a further detail of the base <NUM> of the carrier element <NUM>. A lateral extension <NUM> is provided on each well <NUM> of the base <NUM>. The extension <NUM> is provided with an aperture <NUM> which, in use, can be used to locate a cable retention device (such as a cable tie) to the base <NUM>.

Referring now to <FIG>, <FIG>, features of the end pieces <NUM>, <NUM> will now be described. In addition to the features described above in relation to the end pieces <NUM>,<NUM> described with reference to <FIG>, the end pieces <NUM>, <NUM> are provided with integrally moulded polarity symbols <NUM>, <NUM>.

The base <NUM> of each end piece <NUM>,<NUM> is provided at opposite sides with a foot <NUM>. Each foot <NUM> is provided with an aperture <NUM> which, in use, can receive a mounting stud <NUM> of a surface <NUM> to which the end piece <NUM>,<NUM> is intended to be mounted (see <FIG>).

Each foot <NUM> is additionally configured to receive and locate a nut <NUM> adjacent the aperture <NUM>. The foot <NUM> is provided with facing surfaces <NUM>,<NUM> which align with corresponding faces of the nut <NUM> to prevent rotation thereof relative to the end piece <NUM>,<NUM>.

Each end piece <NUM>,<NUM> is additionally provided with a flange <NUM> which extends from the base <NUM>. The flange <NUM> is provided with a pair of slots <NUM>. The flanges <NUM> are provided so as to assist with the retention and location of a cell cooling arrangement <NUM>. As can be seen in, for example, <FIG> and <FIG>, the manifolds <NUM> of the cell cooling arrangement <NUM> are provided with barbed projections <NUM>. In use, the barbed projections <NUM> are received in the slots <NUM> of the flanges <NUM> - see <FIG>.

It will be understood by the skilled person that features of the carrier element <NUM> described with reference to <FIG> may be utilised in connection with the carrier element <NUM> described with reference to <FIG>. Such utilisation may be either in addition to described features of the carrier element <NUM> or in substitution for one or more features of the carrier element <NUM>. Similarly, it will be understood by the skilled person that features of the carrier element <NUM> described with reference to <FIG> may be utilised in connection with the carrier element <NUM> described with reference to <FIG>. Such utilisation may be either in addition to described features of the carrier element <NUM> or in substitution for one or more features of the carrier element <NUM>.

The present invention provides a carrier system, which advantageously may be formed from moulded plastic, that supports and locates multiple small-format cylindrical cells. The cells can be inserted into the carrier in either orientation - anode upwards or cathode upwards - thus permitting any series-parallel configuration, as necessary according to the application.

A carrier for the cells is realised using two identical "clam shell" mouldings or carrier elements that are brought together around the cells and joined to one another to form a substantially closed housing or carrier. Joining of the carrier elements may be achieved by multiple means including ultrasonic welding. Once the two carrier elements are brought together and joined, the resulting carrier is strong and rigid, and gives mechanical support to the battery cells without adhesive or other fasteners.

Into the ends of the carrier are incorporated mounting bosses with metallic inserts. This enables the carrier to require minimum of additional mechanical support when installing it into its final application.

The system of the present invention accommodates a wide variety of cell configurations, and alignment features within the carrier are also designed to accommodate cells from a range of manufacturers - even cells of the notionally "standard" <NUM> format have dimensional inconsistencies across the supply chain. The cells are arranged in a package-efficient fashion, but allow for the passage of coolant between them.

The present invention further provides a modular carrier system that can be manufactured in smaller pieces that clip together, giving increased flexibility and faster adaptation to different applications at lower cost. The system utilises a common configuration of carrier element <NUM>,<NUM> that can be connected to similar carrier elements to produce a carrier tray having a desired number of wells to receive battery cells <NUM>.

The splits between the parts are chosen such that the number of unique parts is reduced to a minimum, reducing tooling cost and allowing for re-use of the same "base" parts in a range of configurations for different applications.

The current embodiment allows for <NUM> cells to be fitted into each carrier piece (<NUM> cells x <NUM> rows), so modules with any multiple of <NUM> cells is already achievable (up to a limit of probably <NUM> cells). The principle is scalable however, and a carrier holding <NUM> cells (<NUM> cells x <NUM> rows), <NUM> cells (<NUM> cells x <NUM> rows), <NUM> cells (<NUM> cells x <NUM> rows) or virtually any other combination is achievable. It will be appreciated that rows defined in the carrier element <NUM> are staggered so as to reduce the space between adjacent rows of battery cells <NUM>, in use.

Claim 1:
A modular carrier element for a plurality of cylindrical battery cells, the carrier element comprising a base and at least one upstanding wall located on an edge of the base; said at least one wall extending generally perpendicularly with respect to the base; wherein the base is provided with a plurality of open bottomed wells each configured to receive a single cylindrical battery cell, wherein each well is provided with first and second resilient alignment means arranged to bias a cell located within a well in mutually perpendicular directions.