A busbar and a battery module comprising the same

Abstract

A busbar for electrically connecting a plurality of cells of a battery module, the busbar being unitarily formed from a sheet of metal and comprising a first contact portion and a second contact portion that are substantially co-planar with one another and are joined to one another by a thermal expansion portion, which is co-planar with the first and second contact portions and is defined by a plurality of cutouts.

Description

The present disclosure relates to a busbar, which comprises a thermal expansion mechanism, and is suitable for electrically connecting a plurality of cells of a battery module. The present disclosure further relates to a battery module comprising the busbar. Busbars are used in battery packs to facilitate the flow of electric current between individual cells within battery modules. Busbars are typically conductive metal strips or bars that connect the positive and negative terminals of adjacent battery cells. As electric current passes through the busbars, they experience resistive heating due to their finite electrical resistance, which causes thermal expansion. It is necessary to accommodate such thermal expansion. Prior art busbars have typically been formed with joggles between adjacent connected cells, which are formed by bending the busbar. Most commonly, such joggles take the form of an inverted II. Whilst effectively allowing for the required thermal expansion, the use of the joggles adds cost and complexity, since additional tooling is required to form the joggles, and stresses in the bent busbars causes complications in assembly. The present invention arose in a bid to provide an improved busbar, obviating some of the shortcomings of prior art busbars. Representative features are set out in the following clauses, which stand alone or may be combined, in any combination, with one or more features disclosed in the text and / or drawings of the specification. According to the present invention in a first aspect, there is provided a busbar for electrically connecting a plurality of cells of a battery module, the busbar being unitarily formed from a sheet of metal and comprising a first contact portion and a second contact portion that are substantially co-planar with one another and are joined to one another by a thermal expansion portion, which is co-planar with the first and second contact portions and is defined by a plurality of cutouts. By virtue of such an arrangement, there is no stress in the busbar. The busbar is substantially planar in a region that extends between the contact points of the first and second contact portions with the respective contacts of adjacent cells that are connected by the busbar. The elimination of stress makes assembly easier, when compared to prior art busbar arrangements. For example, welding of the busbar to the contacts of the cells is made easier. Moreover, the busbar may be formed by simply cutting a sheet, such that no additional tooling is required, which reduces manufacturing costs. Furthermore, the co-planar thermal expansion portion may act as a fuse. The thermal expansion portion preferably comprises one or more ribs that extend between the first and second contact portions. When a plurality of ribs is provided, the ribs are preferably parallel to one another. Preferably, the thermal expansion portion extends along a longitudinal axis and one or more or all of the ribs comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion, wherein the first and second ends are either offset from one another along the longitudinal axis or are aligned with one another along the longitudinal axis. The ribs may be straight or may have a non-linear profile. When non-linear, the ribs may have a bent, a curved, a zig-zagged or a wavy profile. A width of each of the ribs may may be constant along its length. A with of each of the ribs may vary along its length. Each of the ribs may have a reduced width portion. Preferably, each of the first and second contact portions comprises a hole for alignment with the terminal of a cell. The busbar may comprise three, four or more of the contact portions and a plurality of the thermal expansion portions, wherein between each adjacent pair of the contact portions there is provided one of the thermal expansion portions. Two or more of the thermal expansion portions may extend parallel to one another. Two or more of the thermal expansion portions extend at an angle to one another, in which case the thermal expansion portions may be arranged perpendicular to one another. The thermal expansion portions may meet at an opening provided in the busbar. The busbar may be substantially planar or may be non-planar. According to the present invention in a further aspect, there is provided a battery module comprising a plurality of cells and one or more busbars as detailed above. Further, preferable, features will be apparent from the dependent claims. Non-limiting embodiments of the invention will now be discussed with reference to the following drawings: Figure 1 shows a plan view of a busbar according to a first arrangement; Figure 2 shows a plan view of a busbar according to a second arrangement; Figure 3 shows a plan view of a busbar according to a third arrangement; Figure 4 shows a plan view of a busbar according to a fourth arrangement; Figure 5 shows a plan view of a busbar according to a fifth arrangement; Figure 6 shows a perspective view of a busbar according to a sixth arrangement; Figure 7 shows an exemplary battery module, which includes busbars as shown in Figures 3, 4 and 6; and Figure 8 shows an alternative exemplary battery module, which includes busbars as shown in Figure 5. With reference to the Figure 1, there is shown a busbar 1 for electrically connecting a plurality of cells of a battery module, according to a first non-limiting exemplary arrangement. The busbar 1 is unitarily formed from a sheet of metal. It comprises a first contact portion 2 and a second contact portion 3 that are substantially co-planar with one another and are joined to one another by a thermal expansion portion 4, which is co-planar with the first and second contact portions 2, 3 and is defined by a plurality of cutouts 5. The thermal expansion portion 4 preferably comprises a plurality of ribs 6 that extend between the first and second contact portions 2, 3. The ribs 6 may be parallel to one another, as shown. In alternative arrangements they may be nonparallel or there may be a combination of parallel and non-parallel ribs. Moreover, there may be other members provided in the thermal expansion portion 4 in addition to the ribs 6, irrespective of the specific arrangement of ribs. Preferably, one or more of the ribs 6 comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion. In the present arrangement, every one of the ribs 6 has its first end joined to the first contact portion 2 and its second end joined to the second contact portion 3. In alternative arrangements, including those with other members as noted above, this may not be the case. The thermal expansion portion 4 preferably extends along a longitudinal axis, as shown. In Figure 1, the longitudinal axis of the thermal expansion portion extends vertically. The first and second ends of the ribs 6 may be offset from one another along the longitudinal axis, as seen in Figure 1. It should be appreciated, however, that this need not be the case in alternative arrangements. For example, the first and second ends may be aligned with one another along the longitudinal axis. Whilst the ribs may be straight along their lengths, it is preferable that they have a profile that is non-linear. They may have a bent profile, a curved profile, a wavy profile, a zig-zag profile, or otherwise. In the arrangement of Figure 1, the ribs have a wavy profile, as seen. The wavy profile may be formed by a series of interconnected straight portions. The wavy profile may otherwise be formed by one or more curved portions, or may have a combination of straight and curved portions. In the present arrangement, by way of non-limiting example only, the ribs have straight parallel end portions that are joined by a straight middle portion that extends at an oblique angle relative to the end portions. In the present arrangement, the ribs have a constant width along their lengths, as clearly shown. This need not be the case. The ribs may have widths that vary along their lengths. For example, the ribs may comprise a reduced width portion at a point along their lengths. This may be of particular benefit for fusing purposes, wherein the reduced width portion will melt through to provide the fuse. It may equally aid in accommodating thermal expansion of the cells. The first and second contact portions 2, 3, preferably each comprise a hole for alignment with the terminal of a respective cell. The provision of a hole 7 may aid with the welding of the terminals of the cells to the contact portions 2, 3 during assembly of a battery module. The busbar 1 may be formed, for example, by cutting or stamping. The busbar may be substantially entirely planar, however, this need not be the case, as will be apparent from the discussion below in respect of the arrangement of Figure 6. The busbar 1 will nevertheless, by virtue of the substantially co-planar first contact portion 2, second contact portion 3 and thermal expansion portion 4, be substantially planar in a region that extends between the contact points of the busbar 1 with adjacent cells to which it is joined, which, as discussed above, makes assembly easier, when compared to prior art busbar arrangements. The busbar 1, by way of non-limiting example only, has a 1P configuration, consisting of the first contact portion 2, second contact portion 3 and thermal expansion portion 4 only. As will be appreciated, any of the described features may be applied to busbars having numerous alternative configurations, in particular to busbars comprising additional contact portions and / or having substantially planar or non-planar forms. With reference to Figures 2 to 6, consideration will be given to some nonlimiting, exemplary, alternative arrangements. It should be noted that the discussion below will focus on the differences in these arrangements as compared to the arrangement of Figure 1. It should further be noted, as will be readily appreciated by those skilled in the art, that any of the features described in respect of any one of the described arrangements may be incorporated into any of the other described arrangements. Figure 2 shows a busbar 10, which again, by way of non-limiting example only, has a 1P configuration. The busbar 10 has a very similar from to the busbar of Figure 1. The busbar 10 differs with regard to the form of the thermal expansion portion 4. The thermal expansion portion 4 comprises one or more holes (or openings) 8 for receiving mounting clips. In the present arrangement there are two holes 8 provided. In alternative arrangements, there may be more or less holes 8 provided, or they may be omitted. The holes 8 are shown to be of circular form. They may have different profiles in dependence on the form of clip to be received. The clips to be received may comprise mounting clips that are comprised by a battery module. The cutouts 5 of the thermal expansion portion are adapted to form the holes 8. The Whilst the thermal expansion portion 4 could have a substantially uniform width along its length, as with the arrangement of Figure 1, it may, as shown, comprise a non-uniform width along its length. The thermal expansion portion has a wider portion at one end. It could have a wider portion at both ends in an alternative arrangement. Figure 3 shows a busbar 11, which, by way of non-limiting example only, has a square 2P configuration. In this configuration two additional contact portions 2, 3 are introduced, as compared to the 1P configurations of Figures 1 and 2. Between each adjacent pair of contact portions 2, 3, there is provided a thermal expansion portion 4. The thermal expansion portions 4 are arranged in a cross formation. A central opening 9 is provided adjacent the inner ends of all of the thermal expansion portions 4. The thermal expansion portions may be considered to meet at the central opening 9. Figure 4 shows a busbar 12, which, by way of non-limiting example only, has an inline 2P configuration. In this configuration, again, two additional contact portions 2, 3 are introduced, as compared to the 1P configurations of Figures 1 and 2. However, in contrast to the square 2P configuration of Figure 3, the contact portions 2, 3 and the thermal expansion portions 4 are in line with one another. Between each adjacent pair of contact portions 2, 3, there is provided a thermal expansion portion 4. Figure 5 shows a busbar 13, which, by way of non-limiting example only, has an inline 2P configuration in the manner of the busbar 12 of Figure 4. The dimensions and shape of the busbar 13 differ to that of the busbar 12, purely by way of example. A busbar of any particular configuration may be varied in size and shape to suit the requirements of any battery module that, as will be readily appreciated. An additional optional feature is also shown. The contact portions 2, 3 are provided with indentations 15 in their side edges for receiving mounting clips. In the present arrangement there is an indentation 15 provided in each side of the side edges of the contact portions 2, 3. In alternative arrangements, there may be more or less indentations 15 provided, or they may be omitted. The indentations 5 are shown to be of square form. They may have different profiles in dependence on the form of clip to be received. The clips to be received may comprise mounting clips that are comprised by a battery module. As should be appreciated, indentations 15 may be provided in any of the other described bus bar arrangements herein, they are not limited to use with any particular form of busbar. Figure 6 shows, by way of non-limiting example only, a non-planar (or bent) busbar 14. The arrangement of Figure 6 is provided to demonstrate how non-planar busbars may incorporate a first contact portion 2 and a second contact portion 3 that are substantially co-planar with one another and are joined to one another by a thermal expansion portion 4, which is co-planar with the first and second contact portions 2, 3 and is defined by a plurality of cutouts 5. In the depicted arrangement, there are first and second pairs of first and second contact portions 2, 3, which are parallel to one another and are joined by a central portion 16, which extends substantially perpendicular to the first and second pairs of first and second contact portions 2, 3. The first and second pairs of first and second contact portions 2, 3 may be non-parallel in alternative arrangements. The busbar 14 is, again, unitarily formed. It may be formed by any conventional means, such as cutting or stamping and bending, or simply stamping. The central portion 16 is shown to be non-planar although it could be substantially planar. Additional thermal expansion portions are formed in the central portion 16 although these could alternatively be omitted. It should be appreciated that numerous forms of non-planar busbar could be provided, to suit the particular connection needs of any battery / battery module. With reference now to Figures 7 and 8, by way of non-limiting example only, two alternative forms of battery module 17,18 are shown. Each of the battery modules 17, 18 comprises a plurality of cells 19 that are received by an enclosure 20. The contacts of the battery cells 19 are connected to one another using busbars in accordance with those described above. In the arrangement of Figure 7, busbars 11,12 and 14 are used. In the arrangement of Figure 8, busbars 13 are used. As must be appreciated by those skilled in the art, numerous forms of battery module will be possible, each requiring a different array of busbars of common or differing form. Numerous alternative arrangements and modifications to the embodiments as described herein will be readily appreciated by those skilled in the art within the scope of the appended claims. In particular, features of the described embodiments may be readily combined. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof. Although certain example embodiments of the invention have been described, the scope of the appended claims is not intended to be limited solely to these embodiments. The claims are to be construed literally, purposively, and / or to encompass equivalents. REPRESENTATIVE FEATURES 1. A busbar for electrically connecting a plurality of cells of a battery module, the busbar being unitarily formed from a sheet of metal and comprising a first contact portion and a second contact portion that are substantially co-planar with one another and are joined to one another by a thermal expansion portion, which is coplanar with the first and second contact portions and is defined by a plurality of cutouts. 2. A busbar according to Clause 1, wherein the thermal expansion portion comprises a plurality of ribs that extend between the first and second contact portions. 3.    A busbar according to Clause 2, wherein the ribs are parallel to one another. 4.    A busbar according to Clause 2 or 3, wherein the thermal expansion portion extends along a longitudinal axis and one or more or all of the ribs comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion, wherein the first and second ends are offset from one another along the longitudinal axis. 5. A busbar according to Clause 2 or 3, wherein the thermal expansion portion extends along a longitudinal axis and one or more or all of the ribs comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion, wherein the first and second ends are aligned with one another along the longitudinal axis. 6. A busbar according to any of Clauses 2 to 5, wherein one or more or all of the ribs is straight. 7. A busbar according to any of Clauses 2 to 5, wherein one or more or all of the ribs has a non-linear profile. 8. A busbar according to Clause 7, wherein the non-linear profile is bent, curved, zig-zagged or wavy. 9. A busbar according to any of Clauses 2 to 8, wherein a width of each of the ribs varies along its length. 10. A busbar according to any of Clauses 2 to 9, wherein each of the ribs has one or more reduced width portions. 11. A busbar according to any preceding clause, wherein the first and second contact portions each comprise a hole for alignment with the terminal of a cell. 12. A busbar according to any preceding clause, which comprises three, four or more of the contact portions and a plurality of the thermal expansion portions, wherein between each adjacent pair of the contact portions there is provided one of the thermal expansion portions. 13. A busbar according to Clause 12, wherein two or more of the thermal expansion portions extend parallel to one another. 14. A busbar according to Clause 12 or 13, wherein two or more of the thermal expansion portions extend at an angle to one another. 15. A busbar according to Clause 14, wherein the thermal expansion portions are arranged perpendicular to one another. 16. A busbar according to Clause 14 or 15, wherein the thermal expansion portions meet at an opening provided in the busbar. 17. A busbar according to any preceding clause, which is non-planar. 18. A battery module comprising a plurality of cells and one or more busbars according to any preceding clause.

Claims

1. A busbar for electrically connecting a plurality of cells of a battery module, the busbar being unitarily formed from a sheet of metal and comprising a first contact portion and a second contact portion that are substantially co-planar with one another and are joined to one another by a thermal expansion portion, which is coplanar with the first and second contact portions and is defined by a plurality of cutouts, wherein the thermal expansion portion comprises a plurality of ribs that extend between the first and second contact portions and have non-linear profiles.

2. A busbar as claimed in Claim 1, wherein the ribs are parallel to one another.

3. A busbar as claimed in Claim 1 or 2, wherein the thermal expansion portionextends along a longitudinal axis and one or more or all of the ribs comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion, wherein the first and second ends are offset from one another along the longitudinal axis.

4. A busbar as claimed in Claim 1 or 2, wherein the thermal expansion portion extends along a longitudinal axis and one or more or all of the ribs comprises a first end that is joined to the first contact portion and a second end that is joined to the second contact portion, wherein the first and second ends are aligned with one another along the longitudinal axis.

5. A busbar as claimed in any preceding claim, wherein the non-linear profile is bent, curved, zig-zagged or wavy.

6. A busbar as claimed in any preceding claim, wherein a width of each of the ribs varies along its length.

7. A busbar as claimed in any preceding claim, wherein each of the ribs has one or more reduced width portions.

8. A busbar as claimed in any preceding claim, wherein the first and second contact portions each comprise a hole for alignment with the terminal of a cell.

9. A busbar as claimed in any preceding claim, which comprises three, four or more of the contact portions and a plurality of the thermal expansion portions, wherein between each adjacent pair of the contact portions there is provided one of the thermal expansion portions.

10. A busbar as claimed in Claim 9, wherein two or more of the thermal expansion portions extend parallel to one another.

11. A busbar as claimed in Claim 9 or 10, wherein two or more of the thermal expansion portions extend at an angle to one another.

12. A busbar as claimed in Claim 11, wherein the thermal expansion portions are arranged perpendicular to one another.

13. A busbar as claimed in Claim 11 or 12, wherein the thermal expansion portions meet at an opening provided in the busbar.

14. A busbar as claimed in any preceding claim, which is non-planar.

15. A battery module comprising a plurality of cells and one or more busbars as claimed in any preceding claim.

Images