FIELD OF THE INVENTION

The present invention relates to a design of metal conductors for electrical energy storage cell interconnection systems for use in automotive, on/off-grid energy storage, portable energy devices and manufacturing fields using a plurality of energy storage devices. More specifically, the present invention relates to metal conductors with electromechanical flaps for energy storage cell interconnection in battery packs.

BACKGROUND OF THE INVENTION

This section is intended to provide information relating to the field of the invention and thus any approach/functionality described below should not be assumed to be qualified as prior art merely by its inclusion in this section.

Embodiments of a present disclosure relate to an energy storage device and more particularly to a battery cell interconnection system for electrical and thermal management in a battery pack. A battery cell is a fundamental building block of a battery pack for energy storage and is used in electric vehicles, on/off-grid energy storage systems, telecommunication devices, portable energy devices etc. A cylindrical battery cell consists of a positive electrode on the top surface and negative electrodes on the bottom surfaces of the battery cell. These electrodes are called 'cell tabs' and are the points to which connections are made. A battery pack is an electrical energy source using a plurality of the above-said battery cells in which the tabs of a plurality of the battery cells are connected in series and parallel connected arrays, providing an output voltage and current. The plurality of battery cells may include, but are not limited to, lithium ion battery cell, lithium ion polymer battery cell, nickel metal hydride battery cell, nickel cadmium battery cell, nickel hydrogen battery cell, nickel zinc battery cell, and silver zinc battery cell. Existing battery packs include a plurality of battery cells connected in series and parallel connected arrays using wires, where the wire connections are made using various interconnected systems. Interconnect systems currently consist of heat inducing mechanisms such as resistance spot welding, laser welding and also cold-welding processes such as ultrasonic welding, cell bonding. Such interconnect systems add a lot of capital expenditure and require intensive equipment for interconnecting connections, thereby making the entire process complex, expensive and time consuming.

Also, current battery packs use metal conductors that are welded onto the terminals of the individual energy storage cells, which make it extremely difficult to provide serviceability of the battery pack in-case of malfunctioning of one or more battery cells of the battery pack. In such a scenario, the whole battery pack would have to be replaced even if only a single battery cell has to be replaced as the replacement costs are more cost-effective than the cost of repairing current battery packs.

Further, a battery cell’s terminals include screws/bolts inserted into them where the metal conductors connecting them to a plurality of battery cells have to be tightened with bolts making the whole assembly very heavy and space consuming. This would reduce the energy density of the battery pack and defeating the purpose of making it swappable.

The other limiting issue for lithium-ion battery cells is safety. Lithium-ion battery cells are very sensitive to overcharge and high temperature. At temperatures above 70°C, unfavourable heatproducing side reactions inside the battery cell can lead to even further increases in the battery cell temperature. The battery cell internal temperature increases rapidly if heat is not dissipated effectively. Increase in internal temperature leads to internal short circuiting which causes rapid temperature rises in an individual battery cell. The rapid temperature rise in a battery cell further leads to a thermal runaway. Thermal runaway is triggered by portions of a battery cell reaching critical temperatures that cause the onset of heat-producing exothermic reactions. Also, a temperature increase in one battery cell can propagate to other nearby battery cells in a battery pack, thus causing them to rapidly self -heat, leading to a cascading effect of thermal runaway propagation. Further, the energy released from these reactions can be significant and dangerous, thereby causing the battery pack to heat up and cause harm to any person handling the battery pack. There has been use of safety gloves/insulated clothing by technicians/assembly line workers while assembling battery packs, which is not a fail proof method for worker/human safety.

Hence, there is a need for an improved cell interconnection system for electrical management and to simplify assembly process in a battery pack to address the aforementioned issues.

OBJECTIVE OF THE INVENTION

An object of the present invention is to provide a solution to complicated cell interconnection assembly processes in a battery pack using a plurality of energy storage devices with the aid of an electromechanical cell interconnection bus bar design that connects individual energy storage cells into a battery pack design.

Another object of the present invention is to reduce a cost of battery pack assembly by eliminating the usage of expensive equipment required for welding processes.

Another object of the present invention is to improve a serviceability of a battery pack, allowing individual energy storage devices inside the battery pack to be replaced in case of failure during the operational life-cycle of the battery pack.

Another object of the present invention is to also achieve an optimum provision of cooling for individual energy storage devices through its tab's, to increase the life-cycle and performance of the battery pack throughout its working voltage. SUMMARY

The present disclosure discloses a cell interconnection system for electrical and thermal management in a battery pack. The cell interconnection system comprises a plurality of energy storage cells, a plurality of bus bars and a thermally conducting pad. The plurality of energy storage cells are arranged vertically in a housing. The housing includes a plurality of cavities, where each cavity holds an energy storage cell. Each of the plurality of energy storage cells includes a protruded tab and a flat portion. Each of the plurality of bus bars include a plurality of flat projections and a plurality of flat surfaces. The plurality of bus bars are placed over the plurality of energy storage cells so that each of the plurality of flat projections contacts the protruded tab of each of the energy storage cells and each of the plurality of flat surfaces aligns with the flat portion of each of the energy storage cells.

The contact between each of the plurality of flat projections and the protruded tab of each of the energy storage cells exerts a pressure on the protruded tab of each of the energy storage cells to form a tight interconnection between each of the plurality of flat projections and the protruded tab of each of the energy storage cells. The pressure exerted by each of the plurality of flat projections on the protruded tab of each of the energy storage cells causes an interconnection between each of the plurality of flat surfaces and the flat portion of each of the energy storage cells. The plurality of bus bars are locked into their place because of the pressure exerted by each of the plurality of flat projections on the protruded tab of each of the energy storage cell to maintain the interconnection between each of the plurality of flat projections on the protruded tab of each of the energy storage cell at all times.

The thermally conducting pad dissipates heat from the protruded tab and the flat portion of each of the plurality of energy storage cells to a heat sink. The protruded tab and the flat portion of an energy storage cell has the most amount of heat generation during charging and discharging of the energy storage cell. The heat transfer from the energy storage cell to the thermally conducting pad ensures proper “Tab cooling” of the energy storage cells, thereby providing efficient heat dissipation by keeping the energy storage cells in their optimum working temperature through a wider spectrum of external atmospheric temperatures.

BRIEF DESCRIPTION OF DRAWINGS

The novel features and characteristics of the disclosure are set forth in the description. The disclosure itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following description of an illustrative embodiment when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

FIG. 1 illustrates a schematic representation of a top view of a battery pack 100, in accordance with one or more embodiments of the present disclosure.

FIG. 2 illustrates an exemplary housing 104 with multiple cavities, in accordance with an embodiment of the present disclosure.

FIG. 3 illustrates an exemplary bus bar 114, in accordance with an embodiment of the present disclosure.

FIG. 4 illustrates a schematic representation of an inside view of the battery pack 100, in accordance with one or more embodiments of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the assemblies, structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein. BRIEF DESCRIPTION OF THE INVENTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as would normally occur to those skilled in the art are to be construed as being within the scope of the present invention.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a nonexclusive 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 a process or method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, subsystems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting. Embodiments of the present invention will be described below in detail with reference to the accompanying figures.

The present disclosure relates to battery packs and more particularly to an energy storage cell interconnection system for electrical and thermal management in a battery pack. Existing battery packs include a plurality of energy storage cells connected in series and parallel connected arrays using various interconnected systems, such as welding wires or welding metal conductors onto the terminals of the individual energy storage cells. However, such interconnect systems add a lot of capital expenditure and require intensive equipment for interconnecting connections, thereby making the entire process complex, expensive and time consuming. Also, such interconnect systems do not allow an individual energy storage cell to be replaced in a battery pack in an event of malfunction of the individual energy storage cell. Therefore, the present invention describes an interconnection system which does not require welding and allows easy replacement of individual energy storage cells. Also, the present invention describes an interconnection system which effectively and efficiently dissipates heat from the energy storage cells.

FIG. 1 illustrates a schematic representation of a top view of a battery pack 100, in accordance with one or more embodiments of the present disclosure. The battery pack 100 consists of a plurality of energy storage cells 102 arranged vertically in a housing 104. Each of the plurality of energy storage cells 102 includes a protruded tab 106 surrounded by a flat portion 108. The protruded tab 106 forms a positive terminal and the flat portion 108 forms a negative terminal of the energy storage cell 102. In an embodiment, the energy storage cells 102 may include, but not limited to, lithium-ion cell, lithium-ion polymer cell, nickel metal hydride cell, nickel cadmium cell, nickel hydrogen cell, nickel zinc cell, and silver zinc cell. In another embodiment, the energy storage cells 102 may include any other device capable of storing energy and having a positive electrode and a negative electrode for electrical connections. In an embodiment, the protruded tabs 106 are made by rolling sheets of a metal with very high electrical and thermal conductivity into a tight and compact cylinder forming a body and chassis of the energy storage cells 102. Therefore, the energy storage cells 102 are able to transfer electrical current and energy from chemical reactions in the energy storage cells 102 and to conduct the heat away from the internal surfaces of the battery pack 100.

The housing 104 is a shock resistant, electrically insulated, and mechanically durable housing which includes multiple cavities for holding the plurality of energy storage cells 102. FIG. 2 illustrates an exemplary housing 104 with multiple cavities, in accordance with an embodiment of the present disclosure. The housing 104 includes multiple cavities 110, where each cavity 110 holds one energy storage cell 102. The size of each of the cavities 110 is equal to a size of an outer diameter of an energy storage cell 102, so that a respective cavity 110 holds a respective energy storage cell 102 in its place. Further, each of the cavity 110 includes an upper part 112a and a lower part 112b.

Referring to FIG. 1, the battery pack 100 further includes a plurality of bus bars 114 (also referred to as metal conductors) connecting the plurality of energy storage cells 102. The plurality of bus bars 114 include a plurality of flat projections 116 (also referred to as electromechanical flaps) and a plurality of flat surfaces 118. FIG. 3 illustrates an exemplary bus bar 114, in accordance with an embodiment of the present disclosure. In an embodiment, the plurality of bus bars 114 may be made from a metal (such as copper or aluminium) or an alloy of a metal which is highly electrically conductible and is good by virtue to dissipate heat energy. In another embodiment, the plurality of bus bars 114 may be mass manufactured by stamping sheets of metals, with a specified die or tool based on the plurality of flat projections 116 to ensure consistency and keeping manufacturing costs to a minimum. In yet another embodiment, the plurality of bus bars 114 may be integrated or manufactured into a Printed Circuit Board (PCB) with integrated circuitry as part of a single unit. Further, the thickness of the plurality of bus bars 114 may vary from 0.5mm to 10 mm depending on design variations and requirements of a battery pack. The plurality of flat projections 116 are designed to flex or bend towards a direction against a force or pressure applied so that the flat projections 116 seat onto the protruded tabs 106 of the energy storage cells 102, thereby ensuring proper contact at all given times and preventing any issue of electrical arcing which could occur without the flat projections 116 not being flexible. The thickness range of the flat projections 116 may vary based on a current carrying capacity and vibration levels present in a battery pack.

The plurality of bus bars 114 are placed over the plurality of energy storage cells 102 in a manner such that of the plurality of flat projections 116 of the plurality of bus bars 114 come in contact with of the plurality of protruded tabs 106 of the energy storage devices 102 and the plurality of flat surfaces 118 of the plurality of bus bars 114 align with the plurality of flat portions 108 of the plurality of energy storage cells 102. When the plurality of flat projections 116 come in contact with the plurality of protruded tabs 106, the plurality of flat projections 116 exert a pressure on the protruded tabs 106 so that an interconnection is established between the projections 112 and the protruded tabs 106, which further causes an interconnection between the plurality of flat surfaces 118 and the plurality of flat portions 108.

FIG. 4 illustrates a schematic representation of an inside view of the battery pack 100, in accordance with one or more embodiments of the present disclosure. Referring to FIG. 1 and FIG. 4, the battery pack 100 includes a single cavity 110 to hold an energy storage cell 102. However, it may be noted that any number of cavities may be there in a battery pack to hold multiple energy storage cells depending on the size of a battery pack. The battery pack 100 further includes a bus bar 114 having a flat projection 116 and a flat surface 118 on the left and right side of the flat projection 116. It may be noted that a single bus bar 114 is illustrated for exemplary purposes. However, a plurality of bus bars may be used depending on the size of a battery pack. The bus bar 114 is placed over the energy storage cell 102 in a manner such that the flat projection 116 of the bus bar 114 comes in contact with the protruded tab 106 of the energy storage cell 102 and the flat surface 118 of the bus bar 114 aligns with the flat portion 108 of the energy storage cell 102. When the flat projection 116 comes in contact with the protruded tab 106, the flat projection 116 exerts a pressure on the protruded tab 106. The pressure exerted on the protruded tab 106 causes the energy storage cell 102 to fit tightly within the cavity 110 by pushing the energy storage cell 102 slightly inside the cavity 110, thereby forming a tight interconnection between the flat projection 116 and the protruded tab 106. The interconnection formed between the flat projection 116 and the protruded tab 106 further causes an interconnection between the flat surface 118 of the bus bar 114 and the flat portion 108 of the energy storage cell 102. As a result of the interconnection formed between the flat projection 116 and the protruded tab 106, and the flat surface 118 and the flat portion 108, the energy storage cells 102 illustrated in each row 120a-120c are connected in parallel and the rows 120a-120c are connected in series to one another. The energy storage cells 102 connected in parallel help in increasing ampere-hour capacity of the battery pack 100 and the energy storage cells 102 connected in series help in increasing a voltage output according to load requirements of the battery pack 100. Further, the interconnection formed between the flat projection 116 and the protruded tab 106, and the flat surface 118 and the flat portion 108 couple the energy storage cells 102 with the bus bars 114 to form electrical connections to produce an output voltage. This ensures that the battery pack 100 is electrically connected according to a total number of energy storage cells 102 for a given kilowatt (kWh) requirement, thus can be applied to any voltage and amp-hr rating.

The bus bars 114 are locked into their place because of the pressure exerted by the flat projections 116 on the protruded tabs 106 to maintain the interconnection between the flat projections 116 and the protruded tabs 106 at all given times. This ensures that the interconnection is maintained between the flat projections 116 and the protruded tabs 106 electrically and once the pressure is removed, there is no more contact between the flat projections 116 and the protruded tabs 106, thereby ensuring that the energy storing cells 102 can be safely disconnected from each other. This allows for easy service, exchange, replacement or removal of an individual energy storing cell in case of an energy storage cell cycle life degradation, energy storage cell short circuit, energy storage cell accelerated ageing, increased internal resistance and also energy storage cell upgrades, if any. Therefore, it allows for easy serviceability/exchange/replacement/removal of an individual energy storage cell without having to have expensive and time-consuming processes involved in removing all the individual portable energy storage cells for misfunctioning of an individual energy storage cell.

In the embodiment explained above, an interconnection between the flat surface 118 of the bus bar 114 and the flat portion 108 of the energy storage cell 102 is formed at the top of the energy storage cell 102. However, in another embodiment, an interconnection between the flat surface 118 of the bus bar 114 and the flat portion 108 of the energy storage cell 102 may be formed at the bottom of the energy storage cell 102 by placing a bus bar 114 at the bottom of the energy storage cell 102 (not shown).

The battery pack 100 further includes a heat absorbent layer 122 at the bottom of the cavity 110 that absorbs heat away from the energy storage cell 102 and transfers it onto an outer pack heat sink to dissipate heat energy from the battery pack 100. The heat absorbent layer 122 may be made up of a heat absorbing gel, a heat absorbing material or a heat absorbing porous material. It may be noted that the heat absorbent layer 122 is shown to be present at the bottom of the cavity 110 in accordance with an embodiment of the present disclosure.

In another embodiment, a thermally conducting pad 124 may be present towards the top of the energy storage cell 102 to dissipate the heat energy from the protruded tab 106 and the flat portion 106 to an outer pack heat sink. The protruded tab 106 and the flat portion 106 has the most amount of heat generation during charging and discharging of the energy storage cell 102. The heat transfer from the energy storage cell 102 to the thermally conducting pad 124 ensures proper “Tab cooling” of the energy storage cells 102, thereby providing efficient heat dissipation by keeping the energy storage cells 102 in their optimum working temperature through a wider spectrum of external atmospheric temperatures. The heat transfer from the energy storage cell 102 to the thermally conducting pad 124 occurs through metal-metal conductive heat transfer and is transferred away from the energy storage cell 102 through the flat projection 116 or the bus bar 114 which is in contact with the thermally conducting pad 124. Thereafter, the heat from the thermally conducting pad 124 may be transferred through a latent heat of absorption into the atmosphere with the help of a metal heat sink in contact with the thermally conducting pad 124. The contact established through the flat projection 116 in combination with a metal alloy used in the bus bar 114 and the thermally conducting pad 124 ensures that the heat dissipation is uniform across all the energy storage cells 102 and ensures that the energy storage cells 102 are maintained at their optimum even at very high temperatures.

The arrangement of various components in the battery pack 100, as described in FIG. 1 and FIG. 4, has numerous advantages. The main advantage is that the battery pack uses pressure force to create an interconnection between the flat projections and the protruded tabs, and the plurality of flat surfaces and the plurality of flat portions. Therefore, there is no need of welding wires or welding strips of conducting metals which helps in keeping costs and complexity of the battery pack low and help in ensuring that the interconnection established is always maintained and is highly thermally conductive. In most of the known interconnection mechanisms, a magnetic element is added to a system for providing pressure. However, the addition of a magnetic element adds to a complexity of manufacturing and design, as the contacts are designed to be held onto the energy storing device tabs via an external pressure or force applied through the magnetic element which induces a small change in an electromagnetic inductive force of electrons flowing through an electric/electronic circuit. This electromagnetic inductive force causes hysteresis losses and also creates a variation of working for other passive electric components in the battery pack.

Further, the bus bars are locked into their place because of the pressure exerted by the flat projections on the protruded tabs to maintain the interconnection between the flat projections and the protruded tabs at all given times. This ensures that the interconnection is maintained between the flat projections and the protruded tabs electrically and once the pressure is removed, there is no more contact between the flat projections and the protruded tabs, thereby ensuring that the energy storing cells can be safely disconnected from each other. This allows for easy service, exchange, replacement or removal of an individual energy storing cell in case of an energy storage cell cycle life degradation, energy storage cell short circuit, energy storage cell accelerated ageing, increased internal resistance and also energy storage cell upgrades, if any. Therefore, it allows for easy serviceability/exchange/replacement/removal of an individual energy storage cell without having to have expensive and time-consuming processes involved in removing all the individual portable energy storage cells for misfunctioning of an individual energy storage cell.

Furthermore, heat transfer from the energy storage cell to the thermally conducting pad ensures proper “Tab cooling” of the energy storage cells, thereby providing efficient heat dissipation by keeping the energy storage cells in their optimum working temperature through a wider spectrum of external atmospheric temperatures. The contact established through the flat projection in combination with a metal alloy used in the bus bar and the thermally conducting pad ensures that the heat dissipation is uniform across all the energy storage cells and ensures that the energy storage cells are maintained at their optimum even at very high temperatures.

Equivalents:

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein. The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.