WITHIN A BATTERY PACK

This International Application claims priority from a provisional patent application filed in India having Patent Application No. 201841032830, filed on August 31, 2018 and titled“A CELL INTERCONNECTION SYSTEM FOR ELECTRICAL AND THERMAL MANAGEMENT IN A BATTERY PACK”.

FIELD OF INVENTION

Embodiments of a present disclosure relate to an energy storage device and more particularly to a system to interconnect a plurality of battery cells within a battery pack.

BACKGROUND

A battery pack includes a set of a plurality of battery cells each with positive and negative terminals and a plurality of interconnects. Each of the battery cells convert chemical energy of substances stored in the battery cell into electrical energy. The plurality of interconnects provides electrical conductivity among the plurality of battery cells. The plurality of battery cells may be configured in a series, parallel or a combination of both arrangements to deliver a desired voltage, capacity, or power to an electrical device. During the discharge or charging of the battery cells, heat is generated in the battery cells. However, the plurality of battery cells, specifically battery cells, based on Lithium-ion chemistry, show weakness in the ability to operate safely and consistently at extremes of ambient temperatures where they show a decrease in lifespan, performance, capacity and susceptibility to thermal runaway. Further, ageing rate of lithium-ion batteries is highly sensitive to the operating temperature. Hence, it is desirable to maintain battery cells within a narrow range of ambient temperatures, prevent thermal runaway and minimize the temperature gradient inside the battery pack during a charging and a discharging of the battery pack to improve battery cell capacity, life and performance. Various approaches have been utilized for thermal management to overcome the problems faced while using the lithium ion batteries. Heat generation within battery cells occurs due to electrochemical reactions and ohmic effects from the movement of charged ions and electrons. Heat generation from electrochemical reactions change with time, temperature and rates of reaction while heat generation from electron flow depends on current densities and varies with the rate of charging or discharging, ambient temperatures and internal resistance of battery cells.

Each battery cell contains layers containing multiple materials including electrodes - anode and cathode, solid-electrolyte interphases, separators and current collectors, each with different thicknesses and thermal properties. As a result, the thermal conductivity of the battery is anisotropic. The thermal problem for batteries is partially due to the poor thermal conductivity within a battery cells that creates a large thermal resistance between the heat generation locations and the outer surfaces that can be cooled. For cylindrical battery cells where the layers are spirally wound, heat flowing radial direction in the wound direction must flow through each sheet in series, while heat flowing along the layers flows through each layer in parallel toward the current collectors and the terminals of the battery cell. A significant amount of heat is accumulated inside the battery cell for small temperature rises, but this heat is not easily transported to the surface due to the low effective radial thermal conductivity of the battery. Prior art and published research have established the axial thermal conductivity in battery cells is substantially higher than thermal conductivity in the radial direction.

The other limiting issue for lithium-ion batteries is safety. Lithium-ion batteries are very sensitive to overcharge and high temperature. At temperatures near 100°C, unfavorable heat-producing 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. Thermal runaway is triggered by portions of the battery cell reaching critical temperatures that cause the onset of heat- producing exothermic reactions. Internal short circuiting can lead to rapid temperature rises in an individual battery cell leading to a thermal runaway, and the temperature increase in one cell can propagate to other nearby cells in a battery pack, thus causing them to rapidly self-heat, too leading to a cascading effect of thermal runaway propagation. Furthermore, the energy released from these reactions can be significant and dangerous. Thermal management schemes and devices that mitigate or counteract a rapid temperature rise triggered by thermal runaway also improve the safety of high energy battery packs.

Thermal management strategies that can more uniformly cool the battery cells have a positive impact and can play a critical role in mitigating all these effects. The operating temperature can be tuned to balance transient high-current and high-power discharging and charging requirements and improve battery cell lifecycles if the temperature is maintained uniformly throughout the battery cells and the battery pack.

One such approach for thermal management in the battery pack utilizes cooling an outer radial surface of the battery cells through use of external liquid channels, direct forced convection cooling with air or dielectric liquid, or indirect means through the use of interface materials at the outer radial surface. However, such approaches of cooling can lead to severe thermal anisotropy within the layers of a cell at higher discharge currents. Although the battery cells can be cooled from the outside, a certain temperature gradient forms in the radial direction towards the interior of the battery cell. The temperature in a battery cell drops towards the outside, starting from the center of the battery cell. Temperature gradients within a cell, both in radial and in axial directions, can lead to non-uniform degradation within the cell. Another approach to thermal management in the battery pack involves cooling the terminals or tabs of battery cells. Prior art and research indicate that temperature gradients within a cell can be better managed through tab cooling of battery cells. However, it has not been possible to effectively cool the interior of the battery cells in conventional arrangements via the terminals of battery cells as the accessible surface area at the terminals of the battery cells is limited and the unevenness of the surface due to the presence of electrical connections and welded interconnect structure make it hard to provide a thermal path for the dissipation of heat from the plurality of battery cells.

In further approaches, a plurality of materials with high thermal conductivity and high electrical conductivity, such as electrically conductive adhesives, are used to provide electrical and thermal pathways and connect to the terminals of battery cells without a provision to weld the terminals of the battery cells The use of electrically conductive adhesives , based on acrylate, epoxy or silicone chemistries, poses other challenges such as increased cost of materials, increased electrical and thermal resistance as compared to weld joints and longer assembly times due to curing requirements of these compounds. In further approaches, printed circuit boards made of traditional glass- reinforced epoxy laminate material based printed circuit boards (FR4) or Composite epoxy material based printed circuit boards (CEM-3) have been used to provide a electrical circuit with a limited ability to transfer heat away from the terminals of the battery cells. Other limitations in previous efforts include a lack of a pathway to remove vented fumes and heated gases from the battery cell in the event of an internal failure or an accident. This results in an increased risk of eventual thermal runaway when the material is used with the plurality of battery cells.

In yet another approach, a plurality of thermal interface materials such as thermal pads based on silicone or acrylic compounds or thermal gap fillers are used to remove the heat from the tabs welded to the terminals of battery cells. Thermal interface materials are placed between a heatsink on one side while the plurality of tabs welded to the terminals of the battery cells are in contact on the other side. In such scenarios thick thermal pads have to be used to avoid inadvertent electrical conduction through ruptures in the Thermal interface materials. This results in an increase in thermal resistance and leads to a bottleneck in the flow of heat from the source - the battery cells, to the heatsink.

Hence, there is a need for an improved system to interconnect a plurality of battery cells within a battery pack to address the aforementioned issues.

BRIEF DESCRIPTION

In accordance with one embodiment of the disclosure, a system to interconnect a plurality of battery cells within a battery pack is provided. The system includes a metal core printed circuit board (MCPCB). The metal core printed circuit board (MCPCB) includes a base layer. The metal clad printed circuit board (MCPCB) also includes a thermally conductive dielectric layer bonded to the base layer. The metal core printed circuit board (MCPCB) also includes a circuit layer bonded to the thermally conductive dielectric layer. The circuit layer includes a plurality of sections. Each of the plurality of sections is electrically insulated from each other. The metal core printed circuit board (MCPCB) also includes a mask layer bonded on top of the circuit layer. The system also includes a plurality of interconnect tabs electrically coupled to the corresponding plurality of sections of the circuit layer of the metal core printed circuit board (MCPCB). The plurality of interconnect tabs is configured to connect to the plurality of battery cells. The system also includes one or more through-holes located within each of the corresponding plurality of sections of the circuit layer. Each of the one or more through- hole is configured to facilitate welding of the plurality of interconnect tabs to the battery terminal of the corresponding plurality of battery cells using the at least one welding method.

In accordance with another embodiment, an electric vehicle system is provided. The electric vehicle system includes a chassis. The chassis is configured to provide a structure to the electric vehicle. The electric vehicle also includes at least one controller operatively coupled within the chassis. The at least one controller is configured to control a plurality of electronic components within the electric vehicle. The electric vehicle system also includes a battery pack operatively coupled to the at least one controller. The battery pack includes a metal core printed circuit board (MCPCB). The metal core printed circuit board (MCPCB) includes a base layer. The metal core printed circuit board (MCPCB) also includes a thermally conductive dielectric layer bonded to the base layer. The metal core printed circuit board (MCPCB) also includes a circuit layer bonded to the thermally conductive dielectric layer. The circuit layer includes a plurality of sections. Each of the plurality of sections is electrically isolated from each other. The metal clad printed circuit board (MCPCB) also includes a mask layer bonded on top of the circuit layer. The system also includes a plurality of interconnect tabs electrically coupled to the corresponding plurality of sections of the circuit layer of the metal core printed circuit board (MCPCB). The plurality of interconnect tabs is configured to connect to a battery terminal of the corresponding plurality of battery cells. The system also includes one or more through- holes located within each of the corresponding plurality of circuit layer sections. Each of the one or more through-holes is configured to facilitate welding of the plurality of interconnect tabs to the battery terminals of the corresponding plurality of battery cells using the at least one welding method.

To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:

FIG. 1 is a schematic representation of a system to interconnect a plurality of battery cells within a battery pack in accordance with an embodiment of the present disclosure;

FIG. 2 is a schematic representation of an embodiment of a metal core printed circuit board of system of FIG. 1 in accordance with an embodiment of the present disclosure;

FIG. 3 is a schematic representation of an embodiment of the system of FIG. 1 representing the plurality of sections of the circuit layer of the metal core printed circuit board with a plurality of through-holes and interconnect tabs in accordance with an embodiment of the present disclosure;

FIG. 4 is a schematic representation of an embodiment of the system of FIG. 1 representing an arrangement of the plurality of battery cells on the metal core printed circuit board in accordance with an embodiment of the present disclosure;

FIG. 5 is a block diagram representation of a battery pack of FIG. 1 in accordance with an embodiment of the present disclosure.

FIG. 6 is a block diagram representation of an electric vehicle in accordance with an embodiment of the present disclosure.

Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the disclosure, 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 disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

The terms "comprise", "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 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, sub-systems, 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 disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.

In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”,“an”, and“the” include plural references unless the context clearly dictates otherwise.

Embodiments of the present disclosure relate to a system to interconnect a plurality of battery cells within a battery pack. The system includes a metal core printed circuit board (MCPCB). The metal core printed circuit board (MCPCB) includes a base layer. The metal clad printed circuit board (MCPCB) also includes a thermally conductive dielectric layer bonded to the base layer. The metal clad printed circuit board (MCPCB) also includes a circuit layer bonded to the thermally conductive dielectric layer. The circuit layer includes a plurality of sections. Each of the plurality of sections of the circuit layer is electrically insulated from each other. The metal clad printed circuit board (MCPCB) also includes a mask layer bonded on top of the circuit layer. The system also includes a plurality of interconnect tabs electrically coupled to the corresponding plurality of sections of the circuit layer of the metal core printed circuit board (MCPCB). The plurality of interconnect tabs is configured to connect to the plurality of battery cells. The system also includes one or more through-holes (80) located within each of the corresponding plurality of sections. Each of the one or more through- hole (80) is configured to facilitate welding of the plurality of interconnect tabs (90) to the battery terminal of the corresponding plurality of battery cells (20) using the at least one welding method.

FIG. 1 is a schematic representation of a system (10) to interconnect a plurality of battery cells (20) within a battery pack in accordance with an embodiment of the present disclosure. As used herein, the term‘battery cells’ is defined as a unit which converts chemical energy into electrical energy. In one embodiment, the plurality of battery cells (20) may correspond to a plurality of lithium ion cylindrical cells. In another embodiments, the plurality of battery cells (20) may correspond to a plurality of primary or secondary energy storage elements of different chemistry and form factors.

The system (10) includes a metal core printed circuit board (MCPCB) (30) as described in FIG. 2. As used herein, the term‘MCPCB’ is defined as a type of printed circuit board comprised of metal base which is configured to provide mechanical support and provide a thermal pathway for the removal of heat out of electrical components, wherein the heat may be generated during the operation of the electrical components. A thermally conductive dielectric layer is sandwiched between the metal base layer and a circuit layer to provide electrical isolation between the electrical components. The thermally conductive dielectric layer is also configured to facilitate thermal conduction. The circuit layer is to be chemically etched to form different interconnections required between the electrical components. MCPCBs take advantage of the thermally conductive dielectric layer (50) to transfer heat from the components mounted on the circuit layer (60) to the base layer (40) to achieve lower thermal resistance. Alternatively the metal core printed circuit board abbreviated as MCPCB, may also be referred to as metal clad printed circuit board, metal core pcb, metal pcb, metal base pcb, metal backed pcb, metal clad pcb, insulated metal substrate (IMS), metal core board, aluminium backed pcb, aluminum printed circuit board or metal core board.

The MCPCB (30) includes a base layer (40) which is made of aluminium, copper or stainless steel. The thickness of the base layer (40) may be between 0.5 milli meter (mm) to 3.5 milli meter (mm). The base layer (40) functions as heat spreader. The base layer (40) gives the MCPCB mechanical integrity and distributes and transfers the heat to a heat sink, mounting surface or directly to the ambient air. The base layer (40) may also be referred to as the metal core base layer, aluminum substrate, metal substrate, metal base, aluminium base layer.

The MCPCB (30) also includes a thermally conductive dielectric layer (50). In one embodiment, the thermally conductive dielectric layer (50) may be composed of ceramic polymer material. As used herein, the term‘ceramic polymer material’ is defined as inorganic-organic composites which consists of ceramic fillers and organic polymers. The thermally conductive dielectric layer (50) is configured to transfer heat generated from the current flow in the circuit layer (60) and the heat produced in the plurality of battery cells (20) of the battery pack to base layer (40). Furthermore, the thermally conductive dielectric layer (50) offers electrical isolation between the base layer (40) and the circuit layer (60) with minimum thermal resistance. Alternatively, the thermally conductive dielectric layer may also be referred to as insulation layer, pre-preg dielectric, dielectric layer, thermal conductive laminate, di-electrical layer, dielectric material, dielectric polymer layer, dielectric pre-preg insulator, thermally conductive resin compound, thermal dielectric, thermal pre-preg, or a ceramic- polymer dielectric layer. In one exemplary embodiment, the thickness of the thermally conductive dielectric layer (50) may be between 30 micrometer (pm) to 300 micrometer (pm). The thermally conductive dielectric layer has a thermal conductivity higher than 0.35W/ (m K). The MCPCB (30) also includes a circuit layer (60) bonded to one side of the thermally conductive dielectric layer (50). The circuit layer (60) is composed of metal. In one embodiment, the circuit layer (60) may be made of copper. Further, the circuit layer (60) includes a plurality of sections (not shown in FIG. 1), wherein each of the plurality of sections is electrically insulated from each other. In one embodiment, each of the plurality of sections may have electrical contact among them in a pre-set manner which may be pre-set during the fabrication of the circuit layer (60) associated with the MCPCB (30). In one specific embodiment, the circuit layer (60) may be composed of copper foil. In such embodiment, the circuit layer (60) may be of thickness between 0.5 oz (17.5pm) to 10 oz (350pm). Alternatively, the circuit layer (60) may also be referred to as copper foil or copper circuit layer.

Furthermore, a mask layer (70) is printed on top of the circuit layer (60). In one embodiment, the mask layer (70) may be configured to provide electrical isolation between the circuit layer (60) and any components placed on the mask layer (70). The mask layer (70) also protects the circuit layer (60) from oxidation. Alternatively, the mask layer may also be referred to as the solder mask layer or solder mask.

Furthermore, the system (10) includes a plurality of interconnect tabs (90) electrically coupled to the corresponding plurality of sections of the circuit layer (60) of the metal core printed circuit board (30). The plurality of interconnect tabs (90) is configured to connect the plurality of battery cells (20) with metal core printed circuit board (30). In one embodiment, at least one of the plurality of interconnect tabs (90) connects the terminals of a plurality of battery cells (20) to the corresponding plurality of sections of the circuit layer (60) of the metal core printed circuit board (30). In another embodiment, each of the plurality of interconnect tab (90) connects a single battery cell of the plurality of battery cells (20) to the corresponding plurality of sections of the circuit layer (60) of the metal core printed circuit board (30). In one embodiment, the plurality of interconnect tabs (90) are soldered on to the exposed regions of the circuit layer (60) of the metal core printed circuit board (30). In one embodiment, the plurality of battery cells (20) are welded to the plurality of interconnect tabs (90) by adopting at least one welding method. In one exemplary embodiment, the at least one welding method may be one of a resistance welding method, spot-welding, pulse-arc welding, a laser welding method and an ultrasonic welding method. In such embodiment, the at least one interconnect tab material may be one of Nickel, Copper, or a multi-layer composite of metallurgically bonded dissimilar metals such as nickel, copper, aluminium and stainless steel.

Furthermore, in one specific embodiment, each of the plurality of interconnect tabs includes a bend structure. The bend structure is configured to connect the interconnect tabs (90) to the circuit layer (60) of metal core printed circuit board (30). The interconnect tabs (90) can have dimples, more specifically projections, to support resistance projection welding or spot welding of the interconnect tabs to a battery terminal of the corresponding plurality of battery cells (20). In one embodiment, the interconnect tabs are made circular to maximize surface area of contact with the MCPCB (30) and to maximize cross-sectional area of the current and heat conduction path between a terminal of one of the plurality of battery cells (20) and the MCPCB (30). In one exemplary embodiment radius of the interconnect tab is kept to a minimum to achieve as low resistance as possible for current and heat conduction path between the terminal of the one of the plurality of battery cells (20) and the MCPCB (30). In another exemplary embodiment, a multilayer clad material consisting of copper is used for the interconnect tab to reduce the resistance for the current and heat conduction path between the terminal of one of the plurality of battery cells (20) and the MCPCB (30). In one specific embodiment, each of the adjacent plurality of battery cells (20) may have an opposite polarity to that of the one being electrically coupled to the corresponding plurality of interconnect tabs (90).

The MCPCB (30) also includes one or more through- hole/ openings (80) located within each of the corresponding plurality of sections of the circuit layer (60). Each of the one or more openings (80) is configured to provide access to weld the interconnect tabs to the battery terminal of the corresponding plurality of battery cells (20) to form the battery pack. In one embodiment, a minimum clearance area is provided around the through-hole/opening where the circuit layer (60) is not permitted, to enable the fabrication of the one or more through-holes (80) in the MCPCB (30) using a stamping method or a routing method or a laser cutting method. In another exemplary embodiment, the one or more through-holes (80) may provide a path for vented gases from the plurality of battery cells (20) to escape. The system (10) provides a path to extract heat from individual battery cells (20) along the axial direction through the terminals of the plurality of battery cells (20). Since the axial thermal conductivity within the plurality of battery cells (20) is higher than the thermal conductivity in radial direction, more heat can be extracted from the path of lower thermal resistance. The heat flows from the heat generation locations inside the plurality of battery cells (20) from near the electrodes to the current collectors within the plurality of battery cells (20), and then to the terminals of the corresponding plurality of battery cells (20). The system (10) provides a means to extract heat from the terminals of the plurality of battery cells (20) to the corresponding plurality of interconnect tabs (90) which are welded to the terminals of the plurality of battery cells (90). The heat flows from the plurality of interconnect tabs (90) to the circuit layer (60) of the MCPCB (30) and through the thermally conductive dielectric layer (50) to the base layer (40) which acts as a heat spreader.

FIG. 3 is a schematic representation of an embodiment of the system (100) of FIG. 1 representing the circuit layer (60) of the metal core printed circuit board (30) with a plurality of interconnect tabs (90) in accordance with an embodiment of the present disclosure. The circuit layer (60) of the metal core printed circuit board (MCPCB) (30) includes the plurality of sections (110), wherein the plurality of sections (110) is electrically isolated from each other. In some embodiments, the electrical isolation between each of the plurality of section (110) of the circuit layer (60) may be created by etching the copper material from the undesirable portion of the circuit layer (60). Each of the plurality of section (110) includes the corresponding plurality of interconnect tabs (90).

The plurality of interconnect tabs (90) are configured to connect to the terminals of the plurality of battery cells (20) using the at least one welding method. The at least one welding method includes one of the resistance welding method, spot-welding, pulse-arc welding, laser welding method and the ultrasonic welding method. In one embodiment, the plurality of interconnect tabs may be composed of at least one of nickel material, copper material, or a multi-layer composite of metallurgically bonded dissimilar metals such as nickel, copper, aluminium and stainless steel. In such embodiment, the interconnect tabs may include the bend structure which may be configured to attach the plurality of interconnect tabs (90) to the corresponding plurality of section (110) of circuit layer (60).

FIG. 4 is a schematic representation of an embodiment of the system (130) of FIG. 1 representing an arrangement of the plurality of battery cells (20) on the metal core printed circuit board (30) in accordance with an embodiment of the present disclosure. Each of the plurality of battery cells (20) are connected in at least one of a series configuration and a parallel configuration. In the parallel configuration, the plurality of battery cells (20) are connected such that a positive terminal (140) or a negative terminal (150) of a battery cell of the plurality of battery cells (20) is connected to a similar terminal of an adjacent battery cell of the plurality of battery cells (20) through the corresponding plurality of interconnect tabs (90) and the plurality of sections (110) of the circuit layer (60) of the MCPCB (30). In the series configuration, the plurality of battery cells (20) is connected in alternate manner, such as the positive terminal (140) of a battery cell of the plurality of battery cells (20) is connected to the negative terminal (150) of an adjacent battery cell of the plurality of battery cells (20) through their corresponding plurality of interconnect tabs (90) and the plurality of sections (110) of the circuit layer (60) of the MCPCB (30).

FIG. 5 is a block diagram representation of a battery pack (115) of FIG. 1, showing the interconnection between components in accordance with an embodiment of the present disclosure. In one embodiment, the Battery Pack (115) may further include a battery management system (120) electrically coupled to the plurality of battery cells (225) connected in a parallel-series configuration and the circuit layer (240) via a connecting means. The battery management system (120) is configured to control and monitor the charging and discharging of the battery pack. The battery management system (120) may be coupled through one or more use of bus-bars (85) or cables. The one or more bus-bars (85) or cables electrically connect the parallel-series combined battery cells to the battery management system (120) through the circuit layer (240) of the MCPCB (200). By virtue of the fact that the plurality of battery cells (225) are directly connected to the circuit layer (240), the one or more bus-bars (85) or cables can be connected to specific exposed regions of circuit layer (240). The one or more bus-bars (85) are electrically connected to specific sections of the circuit layer (110) of the MCPCB (200) and the battery management system (120).

In a further embodiment of the battery pack, one of the battery cell of the plurality of battery cells (225) in the Battery pack (190) undergoing thermal runaway is partially prevented from propagating the thermal runaway to other adjacent battery cells (225) by quickly drawing away the heat from the faulty battery cell (225) to a wide area of the MCPCB (200) and other connected cells, thus preventing localized heating near the faulty battery cell (225) from causing adjacent battery cell (225) temperatures reaching their thermal runaway transition point. In accordance with the invention, by providing a method for heat removal from the terminals of the corresponding plurality of battery cells (225) to the MCPCB (200), the invention reduces localized transfer of heat between the plurality of battery cells (225) during a thermal runaway event.

In a further embodiment of the battery pack, additional flexibility to insert thermal barriers (25) between the radial surfaces of the battery cells (225) is provided, thereby further preventing localized transfer of heat between the plurality of adjacent battery cells (225) during a thermal runaway event while still providing a means for thermal management and heat dissipation from the terminals of the plurality of battery cells (225) to the MCPCB (200). Thermal barriers (25) are materials that have a low thermal conductivity or high-temperature withstanding capability or a high specific heat capacity or a high specific latent heat or a combination thereof. Thermal barriers (25) when placed between the radial surfaces of the plurality of battery cells (225) can prevent the localized transfer of heat from any particular battery cell (225) to the neighboring or adjacent battery cell of the plurality of battery cells (225) and this reduces the occurrence of thermal runaway propagation to multiple battery cells (225) within the battery pack (190).

In another embodiment of the battery pack in accordance with the invention, the plurality of battery cells (225) which are connected in a parallel combination, are connected to a battery management system (120) via sense lines (118) which are provided on the circuit layer (240). By virtue of the fact that the battery cells are directly connected to the circuit layer (240), the sense lines (118) can be included in the circuit layer (240). Separately attached voltage sensing wires are not required and the sense lines (118) can be guided directly to the battery management system (120) via the circuit layer (240). Similar sense lines (118) can be used to connect temperature sensors (125) to the battery management system (120).

In yet another embodiment of the battery pack in accordance with the invention includes at least one electrical safety element electrically coupled to the plurality of battery cells (225). The at least one electrical safety element may behave as a fuse. The at least one electrical safety element may be configured to provide protection during one of an overload condition or short circuit condition using a current limitation associated with tapered sections in the circuit layer (230) or necked down region in the plurality of interconnect tabs (90) or a combination thereof. When fuse is implemented as tapered sections (93) in the circuit layer (230), it may be provided in series with any one of the two terminals of each of the plurality of battery cells (20). Similarly, if fuse is implemented in interconnect tabs, then any one of the two interconnect tabs (90) connecting to the two terminals of the plurality of battery cells (225) may have necked down region.

Furthermore, the fuse is used as a type of electrical protection for each individual battery cell. If a malfunction occurs in a battery cell (20), such as an internal electrical short circuit, then this safety element blows open and disconnects the battery cell and interrupts the flow of current from parallel cells into the malfunctioned cell. As a result, the energy storage device, always remains in a safe operating state. Further hazardous processes which could result in a multiple battery cells catching fire can be reliably prevented.

In a yet another embodiment of the battery pack in accordance with the invention, the heat output by the battery cells or group of battery cells is detected by at least one associated temperature sensor (125). The temperature sensor (125) can be connected to the circuit layer (240). The temperature sensor (125) signals the detected temperature of the corresponding plurality of battery cells (225) or groups of battery cells to the battery management system (120). Since the heat of the plurality of battery cells (225) is dissipated via the interconnect tabs and the arrangement of the MCPCB (200) in accordance with the invention, the temperature sensors (125) can be provided in contact with MCPCB (200) and do not need to be accommodated in the interior of the battery pack. In a yet another embodiment of the battery pack in accordance with the invention, balancing resistors (245) are operatively coupled to the circuit layer (240). The one or more balancing resistors (245) are configured to convert excess charge of the corresponding plurality of battery cells (225) in parallel into heat. The one or more balancing resistors (245) are connected to the circuit layer, output the heat produced thereby to the MCPCB (200) and are controlled via the battery management system (120). The one or more balancing resistors (245) are provided for balancing the individual groups of battery cells (225) in parallel when they are unbalanced in comparison to charge stored in other groups of battery cells (225) in parallel. Load differences and different ageing of the plurality of battery cells (225) can cause, within the battery pack, the series-connected battery cells to have different charge levels. The charge differences are compensated for by means of charge balancing using the one or more balancing resistors (245). Excess charge from plurality of battery cells (225) in parallel is converted into heat via the corresponding one or more balancing resistors (245).

In a further embodiment of the battery pack in accordance with the invention, the heat output by the balancing resistors (245) is preferably uniformly distributed via the MCPCB (200) in order to pre heat the battery pack. Pre-heating preferably occurs at low ambient temperatures. At low ambient temperatures, the extractable power and energy of the battery cells decreases. Therefore, in this preferred embodiment, at low temperatures the battery pack is pre-heated. In contrast to battery packs in which the energy stores are pre-heated by a dedicated heater, in the battery pack in accordance with this invention, pre-heating occurs by means of the balancing resistors (245) which are provided for the charge compensation. Since the temperature distribution on the contacting MCPCB (200) is extremely effective, the generated heat of the balancing or compensation resistors is effectively distributed to all the battery cells. Therefore, the battery pack is automatically pre-heated, in particular at low ambient temperatures, whereby the extractable power and energy of the battery cells is increased.

Furthermore, the MCPCB (200), the base layer (210), the thermally conductive di electric layer (220), the circuit layer (230), the mask layer (250), the battery cells (225), the interconnect tabs (90), the circuit layer sections (240) of FIG. 5 are substantially similar to the MCPCB (30), the base layer (40), the thermally conductive di-electric layer (50), the circuit layer (60), the mask layer (70), the battery cells (20), the interconnect tabs (90), the circuit layer sections (110) of FIG. 1.

FIG. 6 is a block diagram representation of an electric vehicle system (160) in accordance with an embodiment of the present disclosure. The electric vehicle (160) includes a chassis (170). As used herein, the term‘chassis’ is defined as a base frame of a wheeled vehicle. The chassis (170) is configured to provide a structure to the electric vehicle. The electric vehicle (160) also includes at least one controller (180) operatively coupled within the chassis (170). The at least one controller (180) is configured to control a plurality of electronic components within the electric vehicle (160).

The electric vehicle (160) also includes a battery pack (190) operatively coupled to the at least one controller (180). The battery pack (190) includes a metal core printed circuit board (MCPCB) (200). The MCPCB (200) includes a base layer made of aluminium, copper or stainless steel. In one embodiment, thickness of the base layer may be between 0.5 milli meter (mm) to 3.5 milli meter (mm). The MCPCB (200) also includes a thermally conductive dielectric layer bonded to the base layer. The thermally conductive dielectric layer is made of ceramic polymer material. The thermally conductive dielectric layer is configured to transfer heat generated from the current flow in the circuit layer and the heat produced in the plurality of battery cells (225) of the battery pack (190) to the base layer. In one exemplary embodiment, the thickness of the thermally conductive dielectric layer may be between 30 micrometer (pm) to 300 micrometer (pm).

The MCPCB (200) also includes a circuit layer bonded to one side of the thermally conductive dielectric layer. The circuit layer is composed of metal. In one embodiment, the circuit layer may be made of copper. Further, the circuit layer includes a plurality of sections, wherein each of the plurality of sections is electrically insulated from each other. In one embodiment, each of the plurality of sections may have electrical contact among them in a pre-set manner which may be pre-set during the fabrication of the circuit layer associated with the MCPCB (200). In one specific embodiment, the circuit layer may be composed of a copper foil. In such embodiment, the circuit layer may be of thickness between 0.5 oz (17.5pm) to 10 oz (350pm). Furthermore, the MCPCB (200) includes a mask layer bonded to the circuit layer. In one embodiment, the mask layer may be configured to provide electrical isolation between the circuit layer and any components placed on the mask layer. The mask layer also protects the circuit layer from oxidation. Alternatively, the mask layer may also be referred to as the solder mask layer or solder mask.

The battery pack (190) also includes one or more openings located within each of the corresponding plurality of circuit layer sections. Each of the one or more openings is configured to provide access to weld the interconnect tabs (270) to one of the terminals of one of the plurality of battery cells (225) to form the battery pack (190). In one exemplary embodiment, the at least one welding method may be one of a resistance welding method, a laser welding method, spot-welding, pulse-arc welding and an ultrasonic welding method.

Furthermore, the battery pack (190) includes a plurality of interconnect tabs (270) electrically coupled to the corresponding plurality of sections of the circuit layer (240) of the metal core printed circuit board (200). The plurality of interconnect tabs (270) is configured to connect the plurality of battery cells (225) with metal core printed circuit board (200) using at least one welding method. In such embodiment, the at least one interconnect tab material may be one of Nickel, Copper, or a multi-layer composite of metallurgically bonded dissimilar metals such as nickel, copper, aluminium and stainless steel.

In one exemplary embodiment, the battery terminal of the plurality of battery cells (225) is connected in at least one of a series configuration and a parallel configuration. In a parallel configuration, the plurality of battery cells (225) are connected such that the positive or negative terminal of a battery cell (225) is connected to the similar terminal of an adjacent battery cell (225) through the corresponding interconnect tabs (270) and sections of the circuit layer of the MCPCB (200). In a series configuration, the plurality of battery cells (225) is connected in alternate manner, such as a positive terminal of a battery cell (225) is connected to the negative terminal of an adjacent battery cell (225) through the corresponding interconnect tabs (270) and sections of the circuit layer of the MCPCB(200). In one embodiment, the plurality of battery cells (225) corresponds to a plurality of lithium-ion cylindrical cells. In other embodiments, the plurality of battery cells (225) may correspond to a plurality of primary or secondary energy storage elements of different chemistry and form factors.

Furthermore, the MCPCB (200) the base layer, the thermally conductive di-electric layer, the circuit layer, the mask layer, the battery pack (190), the interconnect tab (270) and the plurality of battery cells (225) of FIG. 6 are substantially similar to MCPCB (30), a base layer (40), a thermally conductive di-electric layer (50), a circuit layer (60), a mask layer (70), a plurality of interconnect tabs (90), a battery pack (115) of FIG. 1 and FIG. 5 respectively.

Various embodiments of the present disclosure enable the system in providing effective pathways for electrical and thermal management while separating the electrical pathway from the thermal pathway.

Furthermore, the thermally conductive dielectric layer of the metal core printed circuit board includes ceramic polymer material which has excellent viscoelastic properties and Coefficient of Thermal Expansion (CTE) matched with the base layer and the circuit layer which may defend the metal core printed circuit board against thermal and mechanical stresses. In addition, due to the flexibility of the plurality of interconnect tabs, the plurality of battery cells is less prone to wear and tear as they support a movement of the plurality of battery cells without causing actual damage to the plurality of battery cells, henceforth making the system more reliable and more efficient. In addition, the interconnect tabs are designed to be flexible so as to accommodate for the variations in cell height due to manufacturing tolerances

While specific language has been used to describe the invention, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.