Simple and scalable assembly of battery cells using printed circuit boards

Abstract

The present invention relates to a rechargeable battery pack (10) comprising a plurality of battery cells (1), a mechanical structure (3A, 3B) for supporting the battery cells (1), at least one printed circuit board (2) provided for the electrical interconnection of the battery cells (1) and disposed on said upper surface or said lower surface, or both, means of electrical interconnection (4, 4', 5) by contact and without soldering between the battery cells (1) and the printed circuit boards (2), characterized in that the mechanical structure comprises a lower plate (3A) and an upper plate (3B), both provided with housings (20) in corresponding alignment and intended to receive and locate, without gluing, respectively a first end of the battery cells (1) and a second end of the battery cells (1), and in that the printed circuit boards (2) are standardized, such that the number of battery cells (1) and of printed circuit boards (2) can be quickly adapted in order to make the total capacity and voltage of the battery pack (10) scalable or expandable.

Description

SIMPLE AND MODULAR BATTERY CELL ASSEMBLY USING PRINTED CIRCUIT BOARDS Subject of the invention

[0001] The present invention relates to the field of electrical energy storage in batteries. The invention relates more particularly to the design of battery packs comprising a relatively high number of small battery cells. The batteries concerned according to the invention must not have extremely rapid charging constraints, and therefore high thermal constraints. Technological background and state of the art

[0002] Currently, the individual cells that make up the basic elements of a battery are usually welded together or connected to each other by screwed metal plates. Welding means that individual cells, especially defective ones, cannot be easily removed from the battery pack for maintenance or recycling. To prevent the cells from being held together solely by welding, the use of glue is also very common, which stabilizes the cells and protects them from vibrations.

[0003] Low-level protection and integrity (which therefore does not concern the BMS - battery management system) of the battery is often carried out using a small wire soldered between the head of each unit cell and a bus bar to act as a fuse in the event of a malfunction of the affected unit cell. Since the fuse must be specifically sized to match the electrical characteristics of the unit cells, the entire assembly is impacted if a standard unit cell, mechanically identical but electrically different, is used.

[0004] In the case of a wire fuse, there is the disadvantage that this fuse, once burned or broken, causes a short circuit on one of the cells of the battery pack or that metal particles are released into the battery pack. When the fuse is integrated into a printed circuit board (see below), on the other hand, it retains its physical integrity in the event of destruction.

[0005] According to the known state of the art, to summarize, a battery pack is therefore mainly in the form of an assembly via spot welding directly on the cells or via welding of a sheet metal and / or a fuse wire if there is a fuse provided. To ensure the mechanical integrity of the battery pack, different glues are generally used to bond the cells together.

[0006] The current approach has the major drawback of offering insufficient possibilities in terms of maintainability, recycling and flexibility since it is extremely difficult, if not impossible, to desolder and remove the glue without damaging the battery pack.

[0007] With current technology, a complete new design must be created each time a new battery pack is created, due to a lack of flexibility. Maintenance is nearly impossible and recycling is difficult.

[0008] US1 1302981 B2 discloses a battery pack comprising a plurality of battery cells, each battery cell having a positive electrode and a negative electrode on an upper surface of the battery cell, the battery cells being arranged in a first direction and in a second direction traversing the first direction; a protection circuit module, the protection circuit module comprising a printed circuit board (PCB) arranged over the battery cells, and a plurality of conductive tabs on the board printed circuit board for electrically connecting the battery cells; and a housing accommodating the battery cells and the protection circuit module; wherein each of the conductive tabs includes a substrate connector connected to the printed circuit board, a cell connector electrically connected to a battery cell, and a fusible link extending from the substrate connector and having a width less than that of the substrate connector.

[0009] US10720616B2 discloses a battery pack that includes: a plurality of battery cells; a printed circuit board (PCB) substrate electrically connected to the plurality of battery cells and including first and second surfaces opposite each other; and first and second electrode tabs electrically connecting each of the battery cells and the PCB substrate and respectively connected to conductive pads that have different polarities and are located on the first surface of the PCB substrate. The battery pack has an improved structure for easy electrical connection of the battery cells.

[0010] Document US20160329606A1 discloses a battery pack having a housing that includes housing areas for battery cells located between printed circuit boards (PCBs). Each PCB has openings that correspond to the respective housing areas. The battery pack also has legs connected to the battery cells through the openings in the PCBs.A battery management system (BMS) is provided on a side surface of the housing, wherein the PCB boards include pattern portions and wherein: the first ends of the pattern portions of the first PCB are connected to respective ones of the legs corresponding to the first PCB and the second ends of the pattern portions of the first PCB are at a first pattern collection portion on the side surface of the housing, and the first ends of the pattern portions of the second PCB are connected to respective ones of the legs corresponding to the second PCB and the second ends of the pattern portions of the second PCB are at a second pattern collection portion on the side surface of the housing.

[0011] Document US10559804B2 discloses a battery pack comprising first and second cell groups each comprising one or more cells, a printed circuit board electrically connected to the first and second cell groups and a connector provided in the printed circuit board and comprising a plurality of connection terminals. The connection terminals comprise first and second connection terminals respectively electrically connected to the first and second electrodes of the first cell group. The connection terminals comprise first and second connection terminals respectively electrically connected to the first and second electrodes of the second cell group. The first and third connection terminals are in releasable contact with each other, the second and fourth connection terminals are in releasable contact with each other.In some embodiments, it is possible to simply physically release a parallel connection of a plurality of cells or a plurality of groups of cells.

[0012] US 2010 / 062329 A1 discloses a storage battery assembly for vehicles comprising a plurality of battery cells. Each battery cell comprises an enclosed housing and at least one terminal extending from the housing. Conductive bars, mounted on dedicated terminals, electrically connect the battery cells. At least one printed circuit board comprises electronic circuitry configured to at least monitor and control the battery cells. The terminals have electrically conductive interconnecting washers mounted thereon. The interconnecting washers extend to a dedicated printed circuit board and are connected to the electronic circuitry on the respective printed circuit board.

[0013] GB 2522443 A discloses a battery pack using a printed circuit board as an electrical connection for connecting battery cells, comprising a printed circuit board, several conductive parts, protective components, battery cells and a conductive circuit. The printed circuit board comprises several openings. The conductive parts each comprise a first conductive section electrically connected to the upper surface of the printed circuit board, a middle section abutting the inner surface of the openings, and a second conductive section inserted through the openings to the lower surface. The protective components are fixed on the upper surface of the printed circuit board. The battery cells each have two conductive terminals aligned with the openings and electrically connected to the second conductive section. The conductive circuit is electrically connected between the battery cells, the conductive pieces and between the conductive bases of the protective components, and each of the battery cells is electrically connected to a corresponding one of the protective components. Preferably, the conductive pieces are connected to the battery terminals by soldering.

[0014] EP 3 660 952 A1 discloses a battery module comprising: battery cells comprising negative and positive electrodes on the same side; a first conductive plate provided at end portions of the battery cells and adjacent to the negative and positive electrodes, the first conductive plate comprising first through holes through which the negative and positive electrodes are respectively exposed and first stepped portions which are adjacent to the first through holes and recessed toward the battery cells; an insulating plate provided on the first conductive plate and comprising second through holes which at least partially overlap the first through holes;a second conductive plate disposed on the insulating plate, the second conductive plate including third through holes that at least partially overlap the second through holes and second stepped portions that are adjacent to the third through holes and recessed toward the insulating plate; first connection tabs electrically connecting the positive electrodes or the negative electrodes to the first stepped portions; and second connection tabs electrically connecting the other positive and negative electrodes to the second stepped portions.;

[0015] There are several issues related to this technology that need to be addressed, including: - the connection mode of each unit cell with the PCB board; - mechanical fixing of the cells compatible with disassembly of the block and good vibration resistance; - easy connection of the battery pack with the battery monitoring system (BMS); - the ability (linked to the BMS) to diagnose the state of cells in a maintenance context; - the size reduction required for the connection between the cells and the PCBs of the block; - reduction of the space required for fixing the block PCBs. Definitions

[0016] A battery's capacity is the amount of current it continuously delivers. It is expressed in ampere-hours (Ah). Multiplying a battery's capacity by its (nominal) voltage in volts (V) gives the battery's energy (in watt-hours, Wh). To characterize a battery, you need to know its capacity and voltage.

[0017] A battery management system (BMS) is an intelligent electronic safety system, particularly intended for the management of battery packs with cells in series and parallel, capable of providing protection mainly against overvoltages, undervoltages and overcurrents. In addition to the basic functions, the BMS can provide additional control and management functions such as cell balancing, personalized settings, via smartphone and Bluetooth connection, etc. Aims of the invention

[0018] The present invention aims to provide a solution that does not require welding on the unit cells, nor the use of glue to secure the cells together, which allows easy design and production of new batteries of different and variable capacity and / or voltage. each other and ultimately improves the maintainability of the battery pack as well as its recycling.

[0019] This type of battery pack should be able to be used in / as any type of pack incorporating smaller unit cells. Main characteristic elements of the invention

[0020] The present invention relates to a rechargeable battery pack comprising: - a plurality of battery cells, each battery cell having a positive terminal and a negative terminal, an upper surface and a lower surface, said positive and negative terminals being arranged on the same side on the upper or lower surface or alternately arranged on the upper surface and the lower surface, the plurality of battery cells being arranged in a first direction and in a second direction, orthogonal to the first direction; - a mechanical structure supporting the battery cells; - at least two printed circuit boards for electrical interconnection of battery cells arranged on said upper surface or said lower surface, or both; - means of electrical interconnection by contact and without soldering between the battery cells and the printed circuit boards allowing a connection of the battery cells in series and / or in parallel; - means for mechanically fixing the printed circuit boards to the mechanical support structure; the mechanical structure comprising a lower plate and an upper plate, both provided with correspondingly aligned housings intended to accommodate and locate without gluing respectively a first end of the battery cells and a second end of the battery cells, the printed circuit boards being identical or having a limited number of sizes depending on the number of cell connections they have; the printed circuit boards having through holes for fixing by means of screws or rivets the printed circuit boards to the bottom plate and the top plate of the mechanical structure via alignment holes corresponding to the through holes of the printed circuit boards, in said plates, said corresponding holes being located between said housings in the bottom plate and the top plate; said mechanical fixing means cooperating with the printed circuit boards and the mechanical structure to be able to quickly modify the number of battery cells and consequently the total capacity and voltage of the battery pack;characterized in that: the printed circuit boards have a non-linear, wavy profile or lateral side, such that two adjacent printed circuit boards have added wavy profiles, so that, in the final assembly of the battery pack, two adjacent holes on a straight line along the junction of the two printed circuit boards are alternately positioned on each board; and; - the fixings of the printed circuit boards to the lower plate and the upper plate of the mechanical structure respectively are located outside the cells.

[0021] According to preferred embodiments of the invention, the rechargeable battery pack further comprises at least one of the following features or a suitable combination of several of them: - printed circuit boards have the same size or a variable size depending on the number of cell connections they have; - the housings in the lower plate and the upper plate are generally cylindrical in shape and have a lower and upper rim respectively to allow the location and locking of the corresponding battery cell at each of its ends; - the receiving structures are made of an insulating material, for example plastic or a conductive material such as metal; - in the case where at least one of the receiving structures is made of a conductive material, the battery cells, apart from their connections, are wrapped in whole or in part in an insulating film, the insulating film stopping where appropriate before one end of the cell in order to allow the connection of the latter on its periphery; - the host structures are fitted with fins on their edges to allow better heat transfer to the outside; - the means of electrical interconnection by contact and without soldering include spring connectors or contacts; - printed circuit boards are bus bars; - the rechargeable battery pack includes a battery management system integrated on one of the printed circuit boards serving as a bus bar or connected to all of the printed circuit boards via a board edge connector; - the integrated battery management system is configured to know the status of subgroups of cells; - the integrated battery management system includes a dedicated circuit to identify a defective cell; - the integrated battery management system is configured to adapt the charging parameters of the battery pack or each subgroup of cells in the event of detection of one or more defective unit cells; - a fuse of standardized characteristics is associated with each cell, or is in the form of a strip incorporated into the substrate of the printed circuit board or soldered onto it, changing the fuse in the latter case requiring changing the entire board. Brief description of the figures

[0022] Figure 1 shows an embodiment for the connection between cells and PCB boards in a battery pack according to the invention, with electrical connections positioned on one side of a unit cell, at a PCB board located on that same side, according to a perspective view (left) and two elevation views at 90° to each other (right).

[0023] Figure 2 shows another embodiment for the connection between cells and PCB boards in a battery pack according to the invention, with electrical connections positioned on both sides of a unit cell, at two PCB boards located respectively on each side of the cell, in a perspective view (left) and an elevation view (right).

[0024] Figure 3 shows in a plan view the space saving obtained in the configuration according to one embodiment of the invention thanks to a particular profile of PCB cards allowing them to be nested.

[0025] Figure 4 shows an example of a complete battery pack whose total capacity is defined by 6 cells and total voltage is defined by 13 cells, as well as its mechanical structure and using PCB boards on both sides of the pack.

[0026] Figures 5A to 5D show the different stages of assembly of a battery pack according to the execution example of Figure 4, with a bottom-up approach.

[0027] Figure 6 shows an exemplary embodiment according to the invention of a simple PCB board integrating a standard size fuse per cell and a standard connector intended for the connection of a BMS battery monitoring system. Description of preferred embodiments of the invention

[0028] The present invention provides an innovative assembly solution for small, unitary battery cells.

[0029] The innovation of the solution lies in its flexibility and speed in being able to implement batteries of different capacity and voltage while respecting high safety standards starting from same standard unit cells. The solution also offers significant benefits in cell recycling and battery maintenance to enable increased battery pack life.

[0030] Thanks to the assembly solution according to the invention, the cells will no longer be soldered or glued and the possible individual fuse will be a fuse of standard size and characteristics, preferably a removable cartridge fuse fixed to the PCB on a fuse holder, which can be replaced if necessary by another of the same size but with characteristics corresponding to the unit cells used.

[0031] According to the invention, fuses of standardized characteristics can be used which are mounted on a printed circuit board (PCB). These fuses have complete specifications and are available for different current levels, allowing the fuse to be perfectly matched to the unit cell used. Alternatively, the fuse can also be in the form of a strip incorporated into the PCB substrate or soldered onto it, but in this case, changing the fuse will then require changing the entire PCB.

[0032] FIG. 1 shows the specific connection of a cell 1 with a single PCB board 2, the connections of different polarity 4, 4' being located on the same side of the cell 1. FIG. 2 shows the specific connection of a cell 1 with two PCB boards 2, one of these boards 2 being located on each side of the cell 1. In this case, there is a connection 4, 5 on each side of the cell 1, the two connections being of opposite polarity. Since it is not a question, within the scope of the present invention, of soldering the connections to the poles of the individual battery cells, any type of quick connector by contact known to those skilled in the art will advantageously be used, for example spring contacts. The contact will be made when the PCB boards are secured to the mechanical structure of the battery pack (see below).

[0033] As shown in FIG. 3, a feature of the invention is to provide PCB boards 2 having a very particular lateral (side) profile 6, wavy and non-linear, particularly useful when several identical boards 2 are adjacent in the assembly along this lateral side 6, which provides the advantage of reducing the volume or surface area required for the battery pack. The PCB boards 2 are provided with through holes 7 to be able to screw these boards to the mechanical structure 3A, 3B of the battery pack (FIG. 4). Since these fasteners must necessarily be located outside the cells and in order not to increase the distance between two rows of cells at the point where two PCB boards are joined (or adjacent or reported), the corrugated profile allows two adjacent holes 71, 72 in the final assembly to be positioned on two different boards 2 (FIG. 5D).

[0034] FIG. 4 shows a fully assembled battery pack according to one embodiment of the invention.

[0035] As shown in FIGS. 5A to 5D, the assembly is advantageously carried out using a bottom-up approach. The individual cells 1 are first secured without glue to a first mechanical reception structure 3A. This structure 3A has the form of a plate comprising spaced rows of housings 20, of generally cylindrical shape (to accommodate “pencil” batteries). The cells are arranged in these housings 20 at one end and blocked by a rim 21 at this same end (FIG. 5A; detail). A second reception structure 3B is arranged on the cells, at their other end, provided with identical housings 20 with also a rim (not shown) to block the cells at their other end.The two receiving structures 3A, 3B are provided with equidistant holes 7, located between the cell housings and corresponding on the two plates, in order to be able to fix there, preferably screw, the different PCB boards 2 which will close the battery pack, on one or both sides (as in FIG. 4) of the latter. To this end, the through holes 7 made in the PCB boards 2 make it possible to precisely locate these boards relative to the receiving structures 3A, 3B. It is only once the battery pack 10 is assembled that the connectors of the PCB boards 2 actually ensure the electrical connection of the battery elements to each other, in parallel or in series.

[0036] The mechanical support structures 3A, 3B may be made of an insulating material, for example plastic or a conductive material such as metal, which provides better cooling. In this In the latter case, however, there is a constraint of perfect insulation of the battery cells from the mechanical support (use of cells "packaged" in an insulating film). For heat dissipation, the host structures can also be provided with fins or even grooves 22 allowing air circulation.

[0037] PCB boards advantageously serve the purpose of integrating basic unit cell protection, such as a fuse, as well as other potential functions such as a BMS. They also facilitate battery disassembly through the use of non-soldered connectors. This configuration of course allows the use of PCB boards either on one side of the cells for a positive and negative electrical connection, or on both sides for a single (and opposite) polarity connection on each side of the cells.

[0038] FIG. 6 shows an example of a PCB board 2 with four pairs of connectors, corresponding respectively to four cells 1 , the board 2 having a built-in fuse 23 per cell, as well as a connector 24 for the BMS.

[0039] The particular advantages associated with the invention are as follows: - the absence of welds facilitates recycling and makes maintenance possible in the event that one or more unit cells are defective; - fixing the cells without glue in purely mechanical supports which also makes maintenance possible; - the use of PCB boards for connecting cells instead of welded sheets allows flexibility in designs and makes it possible to directly integrate a BMS or integrate other electronic circuits into the battery (for maintenance or for detecting dead cells, for example); - thanks to the use of PCB boards, battery control can be carried out down to the “set” or subset level (level with 6 unit cells for example) with the possibility of determining the status of each “set”; - the status of each “set” being known, the battery management system (BMS) can be designed to intelligently adapt the charging parameters in order to avoid damaging the cells; - the possibility of integrating the BMS into the battery pack on one of the busbar boards or on the side of the battery pack via edge connectors, known per se to those skilled in the art; - the use of standard fuses, which provides flexibility in the choice of cells and independence of the production line with respect to the particular cells chosen in each case; - when the fuse is integrated into the PCB board, it retains its physical integrity even when electrically opened (burned, broken), unlike a simple wire which can leave residue in the battery pack; - the use of PCB boards for the connection between cells reduces the danger of short circuits during assembly since the conductive elements are insulated from the external surface of the PCBs and all connections are then established at the same time. On the other hand, in the case of busbars, it is easier to establish a short circuit during assembly than with a PCB system; - the battery output connectors as well as the connectors for a BMS not integrated into the PCB can be directly part of the PCB; - as the final assembly does not include a welding step but only mechanical assembly steps, there is no need for personnel specifically qualified for cell welding or for a dedicated machine. This avoids the risk of damaging the cells during assembly by welding.

[0040] The disadvantages of the invention are only related to certain higher costs (but which are largely offset by the technological and operational advantages): - using a PCB instead of a soldered sheet metal results in a higher cost compared to direct soldering for large battery packs (typically with more than 100 cells per pack); - the use of standard fuses results in a higher cost compared to a simple wire (or a simple tab) soldered when the production volume is large.

[0041] The battery pack according to the present invention is particularly suitable for military vehicle applications or industrial applications, in which, unlike in civilian vehicles, the charging speed constraint and therefore the corresponding thermal constraint may not be very significant.

[0042] Energy storage applications such as domestic batteries (power wall) with larger cells and constituting a mix of scalable and expandable sub-modules according to the invention and welded sub-modules can also be considered, provided that the degree of maintainability of the assembly is deemed sufficient. List of reference symbols battery cell printed circuit board mechanical support structure connector connector printed circuit board corrugated profile through (resp. non-through) hole rechargeable battery pack housing in mechanical support plate housing flange groove fuse board edge connector adjacent holes in final assembly

Claims

CLAIMS 1. A rechargeable battery pack (10) comprising: - a plurality of battery cells (1), each battery cell (1) having a positive terminal and a negative terminal, an upper surface and a lower surface, said positive and negative terminals being arranged on the same side on the upper or lower surface or alternately arranged on the upper surface and the lower surface, the plurality of battery cells (1) being arranged in a first direction and in a second direction, orthogonal to the first direction; - a mechanical structure (3A, 3B) for supporting the battery cells (1); - at least two printed circuit boards (2) for the electrical interconnection of the battery cells (1) arranged on said upper surface or said lower surface, or both; - electrical interconnection means (4, 4', 5) by contact and without soldering between the battery cells (1) and the printed circuit boards (2) allowing a connection of the battery cells (1) in series and / or in parallel; - means for mechanically fixing the printed circuit boards (2) to the mechanical support structure (3A, 3B); the mechanical structure comprising a lower plate (3A) and an upper plate (3B), both provided with housings (20) in corresponding alignment intended to receive and locate without gluing respectively a first end of the battery cells (1) and a second end of the battery cells (1), the printed circuit boards (2) being identical or having a limited number of sizes depending on the number of cell connections they have; the printed circuit boards (2) having through holes (7) for fixing by means of screws or rivets the printed circuit boards (2) to the lower plate (3A) and to the upper plate (3B) of the mechanical structure via alignment holes (7') corresponding to the through holes (7) of the printed circuit boards (2), in said plates (3A, 3B), said corresponding holes (7') located between said housings (20) in the lower plate (3A) and the upper plate (3B); said mechanical fixing means cooperating with the printed circuit boards (2) and the mechanical structure (3A, 3B) to be able to quickly modify the number of battery cells (1) and consequently the total capacity and voltage of the battery pack (10); characterized in that: - the printed circuit boards (2) have a non-linear, wavy profile or lateral side (6), so that two adjacent printed circuit boards (2) have attached wavy profiles (6), so that, in the final assembly of the battery pack (10), two holes (71, 72) adjacent on a straight line along the junction of the two printed circuit boards (2) are alternately positioned on one and the other board (2); and - the fixings of the printed circuit boards (2) respectively to the lower plate (3A) and to the upper plate (3B) of the mechanical structure are located outside the cells (1).

2. The rechargeable battery pack (10) according to claim 1, characterized in that the printed circuit boards (2) have an identical size or a variable size depending on the number of cell connections (1) they have.

3. The rechargeable battery pack (10) according to claim 1, characterized in that the housings (20) in the lower plate (3A) and the upper plate (3B) are generally cylindrical in shape and have a rim (21) respectively low and high to allow the location and blocking of the corresponding battery cell (1) at each of its ends.

4. The rechargeable battery pack (10) according to claim 1, characterized in that the receiving structures (3A, 3B) are made of an insulating material, for example plastic or a conductive material such as a metal.

5. The rechargeable battery pack (10) according to claim 4, characterized in that, in the case where at least one of the receiving structures (3A, 3B) is made of a conductive material, the battery cells, apart from their connections, are wrapped in whole or in part in an insulating film, the insulating film stopping where appropriate before one end of the cell in order to allow the connection of the latter on its periphery.

6. The rechargeable battery pack (10) according to claim 1, characterized in that the receiving structures (3A, 3B) are provided with fins on their edge to allow better heat transfer to the outside.

7. The rechargeable battery pack (10) according to claim 1, characterized in that the electrical interconnection means (4, 4', 5) by contact and without soldering comprise spring connectors or contacts.

8. The rechargeable battery pack (10) according to claim I, characterized in that the printed circuit boards (2) are bus bars.

9. The rechargeable battery pack (10) according to claim 8, characterized in that it comprises a battery management system integrated on one of the printed circuit boards (2) serving as a bus bar or connected to all of the printed circuit boards (2) via a board edge connector (24).

10. The rechargeable battery pack (10) according to claim 9, characterized in that the integrated battery management system is configured to know the status of subgroups of cells (1).

11. The rechargeable battery pack (10) according to claim II, characterized in that the integrated battery management system comprises a dedicated circuit for identifying a defective cell (1).

12. The rechargeable battery pack (10) according to claim 9, characterized in that the integrated battery management system is configured to adapt the charging parameters of the battery pack (10) or of each subgroup of cells (1) in the event of detection of one or more defective unit cells (1).

13. The rechargeable battery pack (10) according to claim 1, characterized in that a fuse (23) of standardized characteristics is associated with each cell (1), or is in the form of a strip incorporated in the substrate of the printed circuit board (2) or soldered thereto, the change fuse (23) in the latter case requiring the replacement of the complete card (2).

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