Description:FIELD OF THE INVENTION

The present invention relates to battery management in electric vehicles. More particularly, the present invention relates to an assembly for connecting cells in a battery pack using electrically conductive interconnection elements.

BACKGROUND

An electric vehicle (EV) includes one or more battery packs as a power source which provides power to an electric motor of the EV for propulsion. Owing to their ease of operation and eco-friendliness of electric vehicles as compared to conventional ones (for example, internal-combustion engine-based vehicles), these vehicles have gained tremendous popularity in the recent years. As manufacturers of these vehicles are keen to take over the market in the near future, rigorous efforts are being made to improve the functionality of these vehicles. In particular, the focus is on enhancing the energy efficiency of the battery pack that powers these vehicles.
A battery pack is made up of a combination of smaller units such as battery cells or any energy storage system which provides power. Within a pack, battery cells are arranged in a specific series and parallel configuration which defines the voltage and current that the pack can deliver. There are mechanical and electrical systems inside the pack which interconnect the cells. While the mechanical system holds each cell in position, the electrical system taps out current from the cells by interconnecting them and providing a positive and a negative terminal.
The electrical system of cell interconnections through which current is discharged from the cells is known as Current Collector Assembly (CCA). The arrangement of cells in series and parallel connection determines the packing efficiency of the module or pack and hence the energy efficiency of the battery. Typically, in the arrangement of cells of the battery pack, there are multiple groups which have parallelly connected cells. The current is collected from each of the cells in the parallel group and the current flows from a first parallel group to a second parallel group which is connected in series with the first group.
Ideally, the current discharge from each cell of the parallel group should be equal, however it depends on the resistance of the path through the current collector assembly for each cell. However, it is difficult to maintain the resistance path identical, which may lead to different current discharges from cells in parallel and subsequent imbalance within the parallel group of cells. Similar effects take place in the second group of parallel cells which accepts the inflowing current. In the state of art, to make the resistance of the paths between the cells in series identical, the spacing or pitch of the cell arrangement is modified, which, in turn, affects the packing efficiency. A similar problem of uneven currents exists when the current is discharged from each cell in the parallel group at the terminals.
In the state of the art, the current collector assembly does not consider the current carrying efficiency of the path from one parallel group of cells to one or more parallel groups of cells. If cells within a parallel group discharge different currents, then after a while, a few cells will have greater amount of charge than the other cells within the same group. This causes voltage imbalances between the cells which drastically reduce the efficiency of the battery pack. One way in which this problem is handled in the state of the art is by increasing the cell spacing which gives more area for the CCA and thus reducing the overall resistance of the paths from one parallel group of cells to the next one. The layout of such a current collector assembly may be complex and wasteful in terms of material.
Therefore, in view of the problems mentioned above, it is advantageous to provide an efficient current collector assembly to overcome the limitations known in the state of the art.

SUMMARY

This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention nor is it intended for determining the scope of the invention.
To overcome or at least mitigate one of the problems mentioned above in the state of the art, an assembly for connecting cells in a battery pack and a method for achieving equal electrical resistances in the electrical paths is needed. In an embodiment of the present invention, an assembly for connecting cells in a battery pack using conductive interconnection elements is disclosed. The assembly includes a plurality of cells interconnected in series-parallel configuration. The cells are divided into plurality of groups and each group includes a predefined number of cells connected in a parallel configuration. The assembly includes a plurality of electrically conductive interconnection elements connected between the cells of two or more groups of cells. The conductive interconnection elements include a plurality of slits of different orientations to form plurality of paths of equal electrical resistance between the cells of two or more groups of cells for achieving substantially uniform charging and discharging currents of each battery cell.
In another embodiment of the present invention, a method for achieving substantially equal electrical resistances of a plurality of paths in an interconnection element in a battery pack is disclosed. The method includes identifying a first group of cells connected in parallel and a second group of cells connected in parallel among a plurality of groups of cells. The method includes identifying a path of least resistance between each cell of the first group and a corresponding chosen cell of the second group. The method includes estimating a resistance of the identified path based on a resistivity of the interconnecting element, length of the path, and a cross-sectional area of each path. The method further includes interconnecting the first group of cells connected in parallel and the second group of cells connected in parallel using the path of least resistance from one cell of the first group to a chosen cell of the second group.
To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Figure 1 illustrates an arrangement of cells in a battery pack which are interconnected using electrically conductive interconnection elements, according to an embodiment of the present invention;
Figure 2 illustrates a pictorial representation of the battery pack implemented with an embodiment of the disclosed assembly, according to an embodiment of the present invention;
Figure 3 illustrates an arrangement of cells in a battery pack which are interconnected in a pre-defined manner using electrically conductive interconnection elements, according to an embodiment of the present invention;
Figure 4A illustrates the schematic representation of the assembly in the battery pack with one option for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention;
Figure 4B illustrates an alternative representation of the assembly of Figure 5A, for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention;
Figure 5A illustrates the schematic representation of the assembly in the battery pack with another option for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention;
Figure 5B illustrates an alternative representation of the assembly in the battery pack with another option for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention;
Figure 5C illustrates the pictorial representation of the assembly in the battery pack with another option for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention;
Figure 6 illustrates the arrangement of twenty-four cells in current collector assembly, wherein (clockwise from top left) 8×3 arrangement (state-of-art CCA), 12×2 arrangement, 3×8 arrangement, and 6×4 arrangement (CCA of present invention);
Figure 7 illustrates a flowchart depicting a method for achieving equal electrical resistances of a plurality of paths in an interconnection element in a battery pack, according to an embodiment of the present invention;
Figure 8 illustrates the simulation results obtained for current densities in the CCA of the battery pack known in the state of the art; and
Figure 9 illustrates the simulation results for current densities obtained for the disclosed CCA of the battery pack of Figure 1.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
DETAILED DESCRIPTION OF FIGURES
For the purpose of promoting an understanding of the principles of the present invention, reference will now be made to the various embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the present invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the present invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the present invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the present invention and are not intended to be restrictive thereof.
Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature or element, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more…” or “one or more elements is required.”
Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements of the present invention. Some embodiments have been described for the purpose of explaining one or more of the potential ways in which the specific features and/or elements of the proposed invention fulfil the requirements of uniqueness, utility, and non-obviousness.
Use of the phrases and/or terms including, but not limited to, “a first embodiment,” “a further embodiment,” “an alternative embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or other variants thereof do not necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or in the context of more than one embodiment, or in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.
Any particular and all details set forth herein are used in the context of some embodiments and therefore should not necessarily be taken as limiting factors to the proposed invention.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by “comprises... a” does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
For the sake of clarity, the first digit of a reference numeral of each component of the present invention is indicative of the Figure number, in which the corresponding component is shown. For example, reference numerals starting with digit “1” are shown at least in Figure 1. Similarly, reference numerals starting with digit “2” are shown at least in Figure 2.
Figure 1 illustrates an arrangement of cells in a battery pack (100) which are interconnected using electrically conductive interconnection elements (102), according to an embodiment of the present invention.
The battery pack (100) in Figure 1 illustrates a top view of cylindrical cells (104A-H), wherein a current is discharged from each cell (104A-H) through a Current Collector Assembly (CCA) that includes the conductive interconnection element (102). The arrangement of cells (104A-H) in the battery pack (100) determines its packing efficiency and thereby the energy efficiency of the battery (100). The main components of the battery pack (100) are cells (104A-H) and the conductive interconnection element (102). The conductive interconnection element (101) is electrically conductive.
In one example, the cells (104A-H) are of cylindrical form factor having a positive and negative terminal. In one example, the conductive interconnection elements (102) are metal parts which are in a pattern that define the series and parallel configuration of a battery pack (100). These conductive interconnection elements (102) are current carrying components from the cell (104A-H) and thus are made of a material which has a low electrical resistivity.
The battery pack (100) includes a plurality of cells (104A-H) interconnected in series-parallel configuration. The cells (104A-H) are divided into a plurality of groups (106A-B). Each group (106A-B) includes a predefined number of cells (104A-H). The first group of cells (106A) and the second group of cells (106B) among the plurality of cells (104A-H) form a series connection.
Referring to Figure 1, in the arrangement shown, there are two groups for example, (106A) and (106B) which have parallelly connected cells (104A-H). The cells (104A-D) have their positive terminals connected with each other and hence are in parallel with each other. Similarly, the cells (104E-H) have their negative terminals connected with each other and hence are in parallel with each other. The cells (104A-D) form the first group of cells (106-A). The cells (104E-H) form the second group of cells (106-B). Now these two groups need to be connected in series with each other such that the current from positive terminal of cells of one group (106-A) flows to the negative terminal of the other group (106-B).
It is to be noted that, the two groups of cells (106A-B) are shown for the sake of simplicity, and the arrangement is not limited to only two groups of cells (106A-B) and the overall arrangement in a battery pack may include multiple such groups of cells. The conductive interconnection element (102) effecting the interconnection of cells (104A-H) from the two groups of cells (106A-B) is applicable to multiple groups of cells in parallel connection of predefined cell arrangement matrix.
Referring again to Figure 1, an example battery pack (100) with an arrangement, where two parallel groups of parallel cells is shown. In each group, four cells (104A-D) are connected electrically in parallel. The assembly of the battery pack (100) includes a plurality of conductive interconnection elements (102) connected between the cells (104A-H) of two or more groups of cells (106A-B). The conductive interconnection elements (102) include a plurality of slits (108) to form a plurality of paths of equal electrical resistance between the cells (104A-H) of at least two or more groups of cells (106A-B) for achieving substantially uniform charging and discharging currents of each cell (104A-H). The slits (108) provided in the conductive interconnection elements (102) form a plurality of paths of equal electrical resistance between positive terminals of each cell (104A-D) of the first group of cells (106A), connected in parallel, and negative terminals of each cell (104E-H) of the second group of cells (106B), connected in parallel.
The conductive interconnection element (102) is of predetermined uniform thickness, where the ratio of lengths and widths of each of the plurality of paths formed by the slits (108) are configured for achieving equal electrical resistances. The plurality of paths formed by the slits (108) are the paths of equal resistances between each cell (104A-D) of the first group (106A) and each cell (104E-H) of second group (106B) for uniform charging and discharging currents of each cell (104A-H).
For example, the cells (104A-D) have their positive terminal connected with each other. Similarly, cells (104E-H) have their negative terminal connected with each other. Now these two groups (106A-B) need to be connected in series with each other so that the current from the positive terminal group (106-A) can flow to the negative terminal group (106-B). If these two groups (106A-B) are directly connected through a shortest path, then the current flowing out of the positive terminal of cells of group (106-A) may be unequal between cells (104A-D) thus causing imbalance in that group (106-A). Thus, the series connection is effected in a such way that all cells (104A-D) provide equal current. The cells (104A-D) may only provide equal current, if the cells see equal resistance path to the cell belonging to the negative terminals of group (104E-F).
The cells (104A) and (104F) have a path (A) through which current flows from cells (104A) to (104F). As can be seen from Figure 1, the ‘path from cell (104A) to (104F) has roughly the length ‘LA’ and ‘WA is the width of the path. For the sake of clarity of the figure, only the length of path (A) and a person skilled in the art will be able to discern the lengths of the paths (B, C, and D), as meant in this invention. The conducting material thickness is constant throughout the metal sheet, to achieve a resistance value for the path. Similarly, cells (104B) and (104E) are connected directly, where the LB would be the path length and WB is the width. Now, to keep the resistance of this path (B) same as path (A), the ratios of ‘LA’ and ‘WA’, and ‘LB’ and ‘WB’ may be varied, as the path resistance is directly proportional to length of the path and inversely proportional to the width of the path, the thickness of the metal conductor for interconnecting the cells being the same.
The disclosed assembly of the current collector in the battery pack (100) solves the problem of imbalance due to unequal current discharges from the cells in parallel, while ensuring high packing efficiency of the cells (104A-H) in the battery pack (100). The disclosed assembly in the battery pack (100) achieves this by a simplified approach of using high conducting metal sheets and introducing the current paths between cells (104A-H) with the same electrical resistance by the use of slots. While the thickness of the metal sheet is the same throughout, the lengths and widths of the different paths are varied for different paths to achieve the same resistance for all paths between cells in the series connection.
Figure 2 shows a pictorial representation (200) of the battery pack (100) implemented with a disclosed assembly, according to an embodiment of the present invention. In particular, the assembly for connecting cells (104A-H) in the battery pack (100) includes using the conductive interconnection elements (102) in which metal conducting plates are used as conductive interconnection elements (102). The slits (108) are provided to redirect current along the paths of equal electrical resistance between the cells of the two parallel groups (106A-B). This allows an efficient use of space between the cells (104A-H) for conductive interconnection elements (102) thereby enhances packaging efficiency of the battery pack (100).
Figure 3 illustrates an arrangement of cells (300A) in the battery pack (100) which are interconnected in a predefined manner using electrically conductive interconnection elements (102), according to an embodiment of the present invention. In particular, the cells (104A-D) have their negative terminal connected with each other in parallel. All the cells (104A-D) in the group are further connected to a terminal out through a metal conductor. The cells (104B) and (104C) have the path of least resistance (shortest path) to the terminal out point and thus offer least resistance to the flow of current. This arrangement of cells results in more current being drawn by the terminal out from the cells (104B) and (104C) as compared to the cells (104A) and (104D). This leads to an imbalance in the amount of current in different branches which can be resolved by utilizing the assembly as disclosed in Figure 1, introducing slits (108) in between the path from each cell to the terminal out. Further, the ratio of the path length and width is maintained such as to achieve equal resistances for all four cells (104A-D) in the group. For clarity, the resistances between the four cells (104A-D) and between the cells (104A-D) and the terminal out point have been indicated in the schematic representation (300B) of Figure 3.
Figure 4A illustrates the schematic representation (400A) of the assembly in the battery pack (100) with one option for achieving equal electrical resistances of a plurality of paths, according to an embodiment of the present invention. An alternate representation (400B) of the same assembly in the battery pack (100) is shown in Figure 4B. Such an arrangement of cells as shown in Figures 4A and 4B forms a plurality of paths of equal electrical resistances between the cells in the battery pack (100). This arrangement as shown includes the disclosed assembly for connecting cells in the battery pack using conductive interconnection elements (102) for achieving equal electrical resistances in the electrical paths. Similarly, equal resistances of a plurality of paths between the cells in the battery pack (100) can also be achieved by another option of arrangement of cells (500A-C) in the assembly as shown in Figure 5A – 5C.
Figure 6 illustrates the arrangement of twenty-four cells in current collector assembly, wherein (clockwise from top left) 8s×3p arrangement (state-of-art CCA), 12s×2p arrangement, 3s×8p arrangement, and 6s×4p arrangement (CCA of present invention). Each of the three representations (600B), (600C) and (600D) as shown in Figure 6 indicate the way the twenty-four cells in the battery pack (100) are connected using the present concept.
Referring to the state of art current collector assembly, only an 8s×3p configuration is achievable where each group has 3 cells connected in parallel and there are 8 such groups which are connected in series as shown in (600A). Such configuration limits the voltage rating as it depends on the number of cells connected in series and limits the current output which depends on the number of cells connected in parallel.
In one embodiment, with the disclosed assembly for connecting cells in the battery pack (100) and by using conductive interconnection elements (102), different options of arranging cells is possible including 12s×2p, 3s×8p and 6s×4p as shown in (600B), (600C) and (600D) respectively. The advantage of having different possible options for assembling the cells in the battery pack provides flexibility to have different modules or pack configurations within the same packaging arrangement of cells.
Figure 7 illustrates a flowchart depicting a method (700) for achieving equal electrical resistances of a plurality of paths in an interconnection element (102) in a battery pack (100), according to an embodiment of the present invention. The order in which the method steps are described below is not intended to be construed as a limitation, and any number of the described method steps can be combined in any appropriate order to execute the method or an alternative method. Additionally, individual steps may be deleted from the method, without departing from the spirit and scope of the subject matter described herein.
The method (700) includes steps for achieving equal electrical resistances of a plurality of paths in an interconnection element (102) in a battery pack (100) as shown and described with reference to Figure 1.
At step (722), the method includes identifying a first group of cells (106A) connected in parallel and a second group of cells (106B) connected in parallel among a plurality of groups of cells (106A-B). In one example, the plurality of groups of cells may be 'n' group of cells.
At step (724), the method includes identifying a path of least resistance between each cell (104A-D) of the first group (106A) and a corresponding chosen cell of second group (106B). In one example, identifying a path of least resistance includes a step of using a predefined formula for calculating resistance using values of resistivity of the interconnecting element, length of the path and a cross-sectional area of each path. For example, the manner in which the path of least resistance is determined is shown with a formula below.
R=(Rho*L)/A; where A= width of the path * thickness of the path.
At step (726), the method includes estimating a resistance of the identified path based on a resistivity of the interconnecting element (102), length of the path and a cross-sectional area of each path.
At step (728), the method includes interconnecting the first group of cells (106A) connected in parallel and the second group of cells (106B) connected in parallel using the path of least resistance from one cell of the first group (106A) to a chosen cell of the second group (106B).
At step (730), the method includes achieving equal electrical resistances of a plurality of paths in an interconnection element (102) in a battery pack (100).
The first group of cells (106A) connected in parallel, and the second group of cells (106B) connected in parallel are interconnected using a conductive interconnection element (102) comprising a conductive metal plate. The conductive metal plate effecting an interconnection comprises slits (108) to form paths of equal electrical resistance between positive terminals of each cell of a first group of cells (106A) connected in parallel and negative terminals of each cell of a second group of cells (106B) connected in parallel. The equal electrical resistances are achieved by choosing lengths and widths of the paths formed by the slits (108).
The conductive interconnection element (102) includes a plurality of slits (108) to form a plurality of paths of equal electrical resistance between the cells (104A-H) of at least two or more groups of cells (106A-B) for achieving substantially uniform charging and discharging currents of each cell (104A-H). The slits (108) provided in the conductive interconnection elements (102) form a plurality of paths of equal electrical resistance between positive terminals of each cell (104A-D) of the first group of cells (106A), connected in parallel, and negative terminals of each cell (104E-H) of the second group of cells (106B), connected in parallel. The conductive interconnection element (102) is of predetermined uniform thickness, where the ratio of lengths and widths of each of the plurality of paths formed by the slits (108) are configured for achieving equal electrical resistances. The plurality of paths formed by the slits (108) are the paths of least resistance between each cell (104A-D) of the first group (106A) and each cell (104E-H) of second group (106B) for uniform charging and discharging currents of each cell (104A-H).
Figure 8 illustrates the simulation observations obtained for current flow in the CCA of the battery pack known in the state of the art. The cells are arranged in two rows namely, Row 1 and Row 2 current collector assembly as shown in (800A). The Row 1 comprises groups of parallel cells individually connected to terminal outs. The Row 2 comprises of two groups of parallel cells which are connected in series.
The current measured across each cell of Row 1 and Row 2 with the obtained variance value clearly indicates that the current discharge from cells connected in parallel is different leading to an imbalance within the parallel group of cells. A similar effect takes place in the second group of parallel cells which accepts the inflowing current. The color coding as shown in (800B) shows a clear imbalance in the current flowing between the parallel group of cells and a higher deviation from the expected ideal value, wherein the regions in red indicate high current zones and the regions in blue indicate low current zones. In FIG 8, it is apparent that the current imbalance results in high current zone in the middle region of the groups of cells whereas the other regions are low current regions which leads to poor battery performance and efficiency. (shown in uniform blue color).
Figure 9 illustrates the simulation observations for current flow obtained for the disclosed CCA of the battery pack (100) of Figure 1. The assembly for connecting cells in the battery pack (100) using the conductive interconnection elements (102) is shown in (900A). The current measured across each cell is shown in Row 1 and Row 2. The Row 1 includes two groups of parallel cells individually connected to terminal outs. The Row 2 comprises of two groups of parallel cells which are connected in series through the conductive interconnective elements (102) comprising slits (108). The uniformity in the colour, i.e., indicated in blue as shown in (900B) indicates a more stable current flow across the parallel group of cells as achieved by the disclosed assembly of cells in the battery pack (100). This also implies that, due to uniform flow of current within the cells of the battery pack, the overall performance as well as the efficiency of the battery pack increases.
Based on the observations in Figure 9, it is indicated that the current flowing through the cells in the battery pack (100) is more uniform across each cell groups in comparison to the observations as shown in Figure 8, which shows imbalance within the parallel group of cells. It indicates that the disclosed assembly in the present invention for connecting cells in the battery pack efficiently achieves equal electrical resistances of a plurality of paths in an interconnection element. This equal electrical resistance of paths leads to substantially uniform charging and discharging currents of each cell.
It will be appreciated that the modules, processes, systems, and devices described above can be implemented in hardware, hardware programmed by software, software instruction stored on a non-transitory computer readable medium or a combination of the above. Embodiments of the methods, processes, modules, devices, and systems (or their sub-components or modules), may be implemented on a general-purpose computer, a special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit element, an ASIC or other integrated circuit, a digital signal processor, a hardwired electronic or logic circuit such as a discrete element circuit, a programmed logic circuit such as a programmable logic device (PLD), programmable logic array (PLA), field-programmable gate array (FPGA), programmable array logic (PAL) device, or the like. In general, any process capable of implementing the functions or steps described herein can be used to implement embodiments of the methods, systems, or computer program products (software program stored on a non-transitory computer readable medium).
Furthermore, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products may be readily implemented, fully or partially, in software using, for example, object or object-oriented software development environments that provide portable source code that can be used on a variety of computer platforms. Alternatively, embodiments of the disclosed methods, processes, modules, devices, systems, and computer program products can be implemented partially or fully in hardware using, for example, standard logic circuits or a very-large-scale integration (VLSI) design. Other hardware or software can be used to implement embodiments depending on the speed and/or efficiency requirements of the systems, the particular function, and/or particular software or hardware system, microprocessor, or microcomputer being utilized.
In this application, unless specifically stated otherwise, the use of the singular includes the plural and the use of “or” means “and/or.” Furthermore, use of the terms “including” or “having” is not limiting. Any range described herein will be understood to include the endpoints and all values between the endpoints. Features of the disclosed embodiments may be combined, rearranged, omitted, etc., within the scope of the invention to produce additional embodiments. Furthermore, certain features may sometimes be used to advantage without a corresponding use of other features.
List of reference numerals:
Components Reference numerals
100 battery pack
102 conductive interconnection elements
104A-H plurality of cells
106A-B group of cells
108 plurality of slits , Claims:1. An assembly for connecting cells in a battery pack (100) using conductive interconnection elements (102), the assembly comprising:
a. a plurality of cells (104A-H) interconnected in series-parallel configuration, wherein the cells (104A-H) are divided into a plurality of groups (106A-B), each group (106A-B) comprising a predefined number of cells (104A-H) connected in parallel; and
b. a plurality of conductive interconnection elements (102) connected between the cells (104A-H) of two or more groups of cells (106A-B), wherein the conductive interconnection elements (102) comprise a plurality of slits (108) to form a plurality of paths of equal electrical resistance between the cells (104A-H) of at least two or more groups of (106A-B) for achieving substantially uniform charging and discharging currents of each cell (104A-H).

2. The assembly as claimed in claim 1, wherein the slits (108) provided in the conductive interconnection elements (102) form a plurality of paths of equal electrical resistance between positive terminals of each cell (104A-D) of a first group of cells (106A), connected in parallel, and negative terminals of each cell (104E-H) of a second group of cells (106B), connected in parallel.

3. The assembly as claimed in claim 1,
wherein the conductive interconnection element (102) is of predetermined uniform thickness;
wherein the ratio of lengths and widths of each of the plurality of paths formed by the slits (108) are configured for achieving equal electrical resistances, and
wherein the first group of cells (106A) and the second group of cells (106B) amongst the plurality of groups of cells (104A-H) form a series connection.

4. The assembly as claimed in claim 1, wherein the plurality of paths formed by the slits (108) are the paths of least resistance between each cell (104A-D) of the first group (106A) and each cell (104E-H) of second group (106B) for uniform charging and discharging currents of each cell (104A-H).

5. The assembly as claimed in claim 1, wherein the conductive interconnection elements (102) effecting the interconnection of cells (104A-H) from a plurality of groups (106A-B) of cells is applicable to multiple groups of cells in parallel connection of predefined cell arrangement matrix.

6. A method (700) for achieving equal electrical resistances of a plurality of paths in an interconnection element (102) in a battery pack (100), the method (700) comprising:
a. identifying (722) a first group of cells (106A) connected in parallel and a second group of cells (106B) connected in parallel among a plurality of groups (106A-B) of cells;
b. identifying (724) a path of least resistance between each cell (104A-D) of the first group (106A) and a corresponding chosen cell of second group (106B);
c. estimating (726) resistance of the identified path based on a resistivity of the interconnecting element (102), length of the path and a cross-sectional area of each path; and
d. interconnecting (728) the first group of cells (106A) connected in parallel and the second group of cells (106B) connected in parallel using the path of least resistance from one cell of the first group (106A) to a chosen cell of the second group (106B).

7. The method (700) as claimed in claim 6, wherein interconnecting the first group of cells (106A) connected in parallel and the second group of cells (106B) connected in parallel comprises using a conductive interconnection element (102).

8. The method (700) as claimed in claim 7, wherein the conductive interconnection element (102) effecting an interconnection comprises slits (108) to form paths of equal electrical resistance between positive terminals of each cell of a first group of cells (106A) connected in parallel and negative terminals of each cell of a second group of cells (106B) connected in parallel.

9. The method (700) as claimed in claim 8, wherein equal electrical resistances are achieved by choosing lengths and widths of the paths formed by the slits (108) in the conductive interconnection element (102).