DE102022208126A1 - Connection system for connecting cylindrical batteries - Google Patents

Abstract

Connection system for connecting battery cells in a battery pack comprising at least one asymmetric bus bar 5 made of a conductive material, the bus bar comprising a first set of connection elements 6 which can be connected to an equal number of negative poles 3 of battery cells in a set, and a second set of connectors 7 connectable to an equal number of positive poles 4 in a second set of battery cells in the same set, characterized in that the first and second sets of connectors are different, the first set of contact members with a flat area 6 that can be connected and welded to the negative pole 3 of the battery cell, and the second set of contact elements with a stamped terminal 7 that can be connected and welded to the positive pole of the battery cell 1.

Description

technical field

The present invention relates to a bus bar for connecting a large number of cylindrical batteries in a battery pack to be used for the drive system of electric vehicles such as automobiles, and a method of manufacturing such a bus bar.

State of the art

Prior art bus bars use wires to make the final connection to the positive and negative terminals of the battery and connect them to the main bus bars or alternative metallic components in the form of steel bars to carry the energy further.

With the advent of cylindrical batteries in battery packs for battery-electric vehicles, there is a need for a connection system that is easy and reliable to use, adaptable to changing battery layouts, and mass-produced quickly and inexpensively.

DE102020004357 discloses a connection system for a battery pack having a plurality of battery cells, each having a positive pole and a negative pole, with at least some of the positive poles all being connected to one bus bar, while the negative poles are connected to a second bus bar. The connection is made with tabs.

EP3800702 discloses an interconnection system for a battery pack having a lead member extending to and connected to each of the electrode posts of the battery cells, each lead member including a first weld nub in direct contact and a second weld nub without contact. The latter is the reserve in case a connection fails.

The arrangement of these connection systems with cylindrical battery cells in the available space does not allow straight "symmetrical" designs of the busbar that connects the positive and negative poles of the batteries. Increasingly, designs have string lengths that deviate from the number of batteries required for a group of battery cells to achieve a given current or power at a given time. In addition, the busbars according to the prior art take up too much space, which leads to a greater height of the battery housing and thus reduces the possible spaces for accommodating the battery modules in the car.

The aim of the proposed bus bar and associated connection system is to overcome these problems and in particular to provide an alternative bus bar system that can be easily adapted to any layout and increases the freedom of choice in placement in the car. In addition, the proposed connection system offers a reliable system that is easy to assemble and has lower production costs.

Summary of the Invention

The problem is solved with a connection system for connecting battery cells in a battery pack that includes at least two asymmetric bus bars made of a conductive material, the bus bars including a first set of connection elements that are connected to an equal number of negative poles of battery cells in a pack and a second set of connectors connectable to an equal number of positive poles in a second set of battery cells in the same pack, according to the invention and as specified in independent claim 1.

In particular by using asymmetrical busbars with a first and a second set of different terminal elements, the first set comprising contact elements with a flat area 6 that can be connected and welded to the negative terminal 3 of the battery cell, and the second set of contact elements with a stamped terminal 7 includes, which can be connected and welded to the positive pole of the battery cell 1, it is possible to create a connection system that is more flexible in its design of the busbar shape.

In addition, the object is achieved by a battery pack that contains the connection system according to the invention.

Preferably, the first set of contact elements is arranged parallel to each other and can contact a first set of battery cells, while the second set of contact elements is arranged side by side and can reach a second set of battery cells that do not belong to the first set.

In another preferred embodiment, the contact elements connecting the negative poles of the cells are protruding and bent to reach the negative pole. The offset of Contact element intended for connection to the negative pole must not be more than 3 mm away from the underside of the main busbar. To advantageously reduce the overall height of the connection system.

This can be further improved by integrating at least part of the contact elements for the positive pole into the main area of the busbar. The positive pole of the battery preferably protrudes from the battery. The overall height of the system is defined by the height between the negative terminal terminal and the battery cover, which can sit directly over the main area of the power rail.

The distance between the surface of the connector intended for the connection of the negative pole and the highest point of the opposite surface of the busbar is determined by the distance between the battery cover and the top surface of the busbar.

The busbar with the contacting elements according to the invention can consist of a single material.

The busbar is preferably made of a conductive metal, preferably aluminum, steel, brass, copper or their alloys.

The busbars are preferably stamped or pressed from plate or sheet metal material.

Preferably, the conductor rail consists of a plate or sheet with a final thickness in the part between 0.1 and 3 mm, preferably the thickness in the main area of the conductor rail is between 0.4 and 1 mm. The thickness in the connection terminal can be less than the main part of the bus bar, preferably between 0.3 and 0.7 mm. This thickness is preferable for any welding work in this area, preferably ultrasonic or laser welding is used. Preferably, the welding process is different between the positive terminals and the negative terminals so that the melting temperature is different and the second weld does not adversely affect the adjacent weld points and/or the battery parts directly connected to the weld point.

Thermal expansion zones are preferably created in the bus bar material to prevent thermal expansion forces in the horizontal or vertical direction at each weld joint, preferably vertical offsets and/or horizontal cuts are used.

In a further embodiment, the connection system according to the invention also comprises a polymer support frame which is connected to each bus bar by at least one mechanical connection or a material connection such as gluing. The polymer support frame has multiple functions including holding multiple bus bars together in a predefined pattern, easily placing the bus bars on the battery cells in alignment with the battery posts for welding the connection points, integrating any necessary sensors on the bus bars and/or the battery cells, for Example temperature or voltage sensors.

The polymer support frame preferably forms a gap between the top of the battery and the bus bars to prevent shorting of the circuit. Depending on the polymer chosen, they can enhance the battery pack's impact protection, preventing a lateral or vertical impact from causing a short circuit by forcing the metallic bus bars onto the cells.

Preferably, the mechanical connection between the support frame and the bus bar is such that the bus bar can move within a certain range in the direction of the plane of the bus bar in order to compensate for the thermal expansion of the bus bar and/or the support frame.

The support frame preferably consists of at least one of the following materials: polycarbonate, polypropylene, polyetheretherketone (PEEK), polyamide PA, acrylonitrile butadiene styrene (ABS) and preferably of a filling material such as glass fibers, natural fibers, wood fibers, carbon fibers, mica flakes or calcium carbonate.

A battery pack with multiple cylindrical battery cells mounted so that all positive poles are in the same plane, each (3+n) battery cell forming a group, where n is a number between 0 and 7, and the battery pack containing multiple groups comprising sufficient busbars according to the invention to connect each first group of poles in a first group to a second group of poles in a second group adjacent to the first group, the first and second groups of poles being in pole direction distinguish and so that each battery is connected to two busbars.

A battery pack according to the invention, in which the connection system several power rails cells that are differently shaped and form a repeating pattern to connect multiple rows of battery cells together, with each cell connected to only two bus bars.

Preferably, the bus bar pattern consists of no more than 10 different bus bar shapes that are continuously repeated in a pattern that covers the entire battery pack. Fewer busbar shapes reduce overall production costs.

A battery pack may also include end bus bars that terminate rows of bus bars. These final busbars are only connected to either the positive or the negative pole. The end busbars can also be connected to a connection.

The invention also includes a method of manufacturing individual bus bars and a set of bus bars that can cover a group of battery cells. Multiple sets of bus bars may be required to cover an electric vehicle battery pack.

1. 1. Stanzen oder Ausschneiden der Stromschienen aus einem plattenförmigen leitfähigen Material, vorzugsweise Aluminium oder vergleichbarem Metall;
2. 2. Biegen, Stanzen oder Formen der Stromschienen in die endgültige Form,
3. 3. Übertragen der so geformten Stromschienen auf die Polymerträgerplatte und stoffliches Verbinden beider Schichten miteinander.

A method for producing the busbar system according to the invention comprises at least the following steps

1. 1. Stamping or cutting out the busbars from a plate-shaped conductive material, preferably aluminum or a comparable metal;
2. 2. Bending, stamping or forming the busbars into the final shape,
3. 3. Transferring the conductor rails formed in this way to the polymer carrier plate and materially connecting both layers to one another.

Bending, embossing or forming and cutting or stamping can be done in either separate or combined process steps. Depending on the final shape, you can start with either step 1 or 2. Optionally, the bending step 2 and the punching step 1 can be carried out alternately in order to achieve the optimal process and product conditions. Step 1 or 2 may involve local thinning of the material if required or necessary for the process. Deliberate thinning can be done at the solder joints.

In one type of production, a series of incremental steps can be performed in parallel for each disk type or group of disk types. Subsequently, these plate types must be positioned on the plastic carrier by automatic picking and placing.

The required work steps can also be combined in one tool. A method is preferably chosen in which at least one set of busbars is pre-cut, bent and punched out, preferably already in the final layout, all in the same tool. Surprisingly, this is a very economical way of production while eliminating the need to pick out the different parts for layout.

In one embodiment, a progressive stamping process is used. The individual metal plates are stamped and then bent to give the plates their final shape. In this case, all the different shapes of the busbars are manufactured separately and a manual or robotic picking process places all the metal busbars on the polymer support plate.

In an alternative embodiment, a single tool is used to punch and cut all of the bus bars that make up a set of a sheet of conductive material. The tool can contain process steps that take place within the framework of the one-tool concept. For example, a pre-cutting tool may be integrated to first cut free the legs that need to be bent, while the complete shape is stamped into final shape after the legs have been formed.

The busbars shaped and cut in this way are placed on a polymer carrier in the final layout. Preferably, the plates are placed in contact with a pre-glued area on the plastic backing to physically bond the metal plates and the plastic backing. Alternatively, the busbars and polymer backing plate can be connected by other means such as clips, pins and holes.

The busbars are placed on the polymer carrier plate and are connected to the polymer carrier plate at least at certain points. Preferably, a temperature sensitive or pressure sensitive adhesive is used to bond the bus bars to the backing plate. In this case, the polymer carrier plate and the busbars are pressed together by means of heat and/or pressure using a press.

One possible option is pins on the plastic carrier that insert through pinholes in the busbars and fuse the tip of the pin into a pinhead larger than the pinhole, connecting the busbar and carrier with an easy-to-move joint.

A tolerance can be created to guarantee that all connections are in the right place before the bus bars are soldered to the battery cells.

In one embodiment, a final forming and/or cutting step may be incorporated into this bonding step. For example, if the complete set is molded in one tool, the bus bars can be connected with small bridges to maintain the correct spacing between the plates during transport and storage. These small bridges can be cut off during the connection step.

A set of bus bars can cover a group of battery cells within a complete battery pack of a BEV or cover all cells. Multiple combinations of bus bars and polymer backing plates, defined as a unit, may be required within a vehicle to cover the entire battery pack. The polymer backing sheets may have connecting means to connect adjacent units, for example by mechanical means such as hooks or clips or similar devices. The polymer backing sheets may have overlapping areas for bonding, optionally with glue.

Preferably the conductive material is a conductive metal, for example aluminium, steel, copper, brass or its alloys.

1 schematically shows the batteries 1 and 2, the battery 1 belonging to a first group of battery cells and the battery 2 to a second group of battery cells. Each battery has a nipple 4, 4' forming the positive pole and a sleeve 3, 3' forming the negative pole; the sheath can extend over the top of the battery but should not be connected to the positive terminal. The connection system according to the invention with busbars 5 and 5' is arranged in such a way that the positive pole 4 of the first battery belonging to a first group of battery cells is connected to the negative sheath 3' of the battery belonging to the second group of battery cells . The connection area 7, 7', which is connected to the positive pole, is designed as a stamped terminal, while the connection area 6, 6', which is connected to the negative shell, is designed as a lip or leg. Both connection areas are flat in the contact area, which is defined as a contact terminal.

Each battery is only in contact with two different busbars, with one busbar being in contact with the positive pole and another with the negative pole.

Each group of batteries preferably all contacts a first positive pole bus bar and a second negative pole bus bar, with all within the group contacting the same positive pole or negative pole bus bar.

The busbars consist of a sheet-like conductive material that is shaped, for example by stamping.

Preferably, the bus bars are formed in a progressive stamping process while the polymer backing plate is manufactured in a combined stamping and stamping process.

Preferably the conductive material is a conductive metal, for example aluminium, steel, copper, brass or its alloys.

shows the configuration for placing multiple busbars on a battery stack where rows of 3 battery cells are grouped into 5 parallel cells.

Bus bars 5A, 5B, 5C, 5D, 5E and 5F are arranged in a pattern to connect adjacent groups of batteries to either the positive or negative terminal (see ). A group of batteries marked with a dashed circle and a 1 belong together and have their positive pole connected to the positive stamped terminal 7, all belonging to the same bus bar 5C. The negative pole of each battery belonging to this first group 1 is connected to the connection area 6 of the busbar 5D. The bus bar 5D is connected to the positive terminal of a second group of batteries (not shown) with another adjacent group on the right side of the picture. The bus bar 5C is connected to the negative poles of a third group of batteries on the left side of the picture.

All power rails shown have a slightly different asymmetrical design that allows multiple batteries to be connected in a group. The benefit of the geometry is that the asymmetric design and layout of the linkage system works especially well for groups where row size differs from group size. For example, in the case shown, the vertical physical battery cells have a row size of 3, while the group size is 5. While organizing the positive or negative connection within a group still is on a busbar, a group is therefore only in contact with two busbars.

The geometric design of each power rail is chosen to fit together in a repeating pattern without overlapping or touching adjacent power rails. This enables the reduction of different designs within one battery pack and lowers production costs. To close a series of busbars, special end busbars are used that have only positive or negative poles (not shown). These end bus bars can be formed by breaking off protrusions of the bus bars used in the pattern.

again shows the same 2 batteries as in with more detail in the height requirements between components.

Battery 1 belongs to a first group of batteries connected to a first busbar, while battery 2 belongs to a second group of batteries connected to a second busbar 5 . The busbars are welded to the positive or negative pole of the batteries (21). The bus bar 5 also includes an example of a thermal expansion zone 20 to prevent force being applied to the weld joint during thermal expansion of the material of the bus bars.

The height difference at the specified point is indicated with h.

The conductor rail is made of plate material and has a thickness h1 of between 1 and 3 mm, preferably between 1 and 2 mm in the main area of the plate.

Preferably, the thickness of h1 is less than the thickness h2 so that adjacent bus bar connections of a battery cannot overlap or touch, resulting in undesirable circuit shortcuts.

The area of the stamped terminal can be thinner so that welding is possible in this area, preferably this busbar plate has a thickness h3 of less than 1 mm, preferably between 0.1 and 0.7 mm.

Taking these different height requirements into account, the total height of the busbars welded onto the batteries, including the connection plate, must not exceed 4 mm. This is a reduction in height compared to the prior art connection system.

The connection system according to the invention shows a modular busbar system that is easy to manufacture and to place on the battery pack and allows precise welding of the busbars to the battery poles and ensures a reliable circuit even under thermal stress. In addition, it is more flexible in adapting to different layouts of cylindrical battery cells and/or shapes and/or sizes of the cylindrical battery cells. In addition, it is reduced in height, which enables the use of battery cell modules with the busbar system according to the invention in areas that cannot be reached with current busbar systems.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102020004357 [0004]
• EP 3800702 [0005]

Claims (21)

Connection system for connecting battery cells in a battery pack comprising at least one asymmetric bus bar 5 made of a conductive material, the bus bar comprising a first set of connection elements 6 which can be connected to an equal number of negative poles 3 of battery cells in a set, and a second set of connectors 7 connectable to an equal number of positive poles 4 in a second set of battery cells in the same set, characterized in that the first and second sets of connectors are different, the first set of contact members with a flat area 6 that can be connected and welded to the negative pole 3 of the battery cell, and the second set of contact elements with a stamped terminal 7 that can be connected and welded to the positive pole of the battery cell 1. connection system claim 1 , wherein the first set of contact elements is arranged parallel to each other and can contact a first group of battery cells, while the second set of contact elements is arranged side by side and can reach a second group of battery cells that do not belong to the first group. A connection system according to any one of the preceding claims, wherein the contact elements connecting the negative poles of the cells project and are bent in an offset to reach the negative pole. connection system claim 3 , where the offset of the contact element intended for connection to the negative pole is not more than 3 mm from the lower surface of the main busbar. Connection system according to one of the preceding claims, wherein at least part of the contact elements for the positive pole is integrated into the main area of the busbar. Connection system according to one of the preceding claims, in which the busbar with the contact elements consists of a conductive metal, preferably aluminium, steel, brass, copper or alloys thereof. Connection system according to one of the preceding claims, wherein the distance between the surface of the connection element intended for connecting the negative pole and the highest point of the opposite surface of the busbar is no more than 4 mm, preferably more than 1.5 mm. Connection system according to one of the preceding claims, wherein the conductor rail consists of a plate material and has a thickness between 0.1 and 3 mm, preferably between 0.4 and 1 mm. Connection system according to one of the preceding claims, wherein the thickness of the busbar varies, preferably the connection has a smaller thickness than the main busbar, preferably between 0.3 and 0.7 mm. Connection system according to one of the preceding claims, wherein the at least one busbar is formed in thermal expansion zones to prevent thermal expansion forces in horizontal or vertical direction at each weld connection, preferably by vertical offsets and/or horizontal cuts. A connection system according to any one of the preceding claims, further comprising a polymer support frame connected to each bus bar by at least one mechanical connection. connection system claim 11 wherein the mechanical connection between the support frame and the busbar is such that the busbar can move within a certain limit in the direction of the plane of the busbar to compensate for the thermal expansion of the busbar and/or the support frame. Connection system according to one of Claims 11 or 12 , wherein the support frame comprises at least one of the following materials: polycarbonate, polypropylene, polyetheretherketone (PEEK), polyamide PA, acrylonitrile butadiene styrene (ABS) and preferably a filler material such as glass fibers, natural fibers, wood fibers, carbon fibers, mica flakes or calcium carbonate. Battery pack comprising a plurality of cylindrical battery cells mounted with all positive poles in the same plane, each (3+n) battery cell forming a group, where n is a number between 0 and 7, and the battery pack having multiple groups, comprising enough bus bars according to any one of the preceding claims to connect each first group of poles in a first group to a second group of poles in a second group adjacent to the first group, the first and second groups of poles himself in the Distinguish pole direction and in such a way that each battery cell is connected to two busbars. battery pack after claim 10 , wherein the connection system has multiple bus bars that are differently shaped and form a repeating pattern to connect multiple rows of battery cells together, each cell being connected to only 2 bus bars. battery pack after Claim 16 , where the busbar pattern consists of no more than 10 different busbar shapes continuously repeating in a pattern to cover the entire battery stack. Battery pack according to one of the Claims 15 and 16 , further with end busbars, which close rows of busbars by connecting them only to either the positive or negative pole. A method for producing the busbar system according to the invention comprises at least the following steps (1) Stamping or cutting the bus bars out of a sheet-like conductive material, preferably aluminum or comparable metal; (2) Bending, embossing or forming the bus bars into the final shape and (3) Transferring the busbars thus formed to the polymer backing sheet and materially bonding both layers together. procedure after Claim 18 , where steps 1 and 2 are combined in one tool. procedure after Claim 18 or 19 , whereby steps 1 and 2 are combined in a single tool and the process steps take place within the tooling concept, preferably a pre-cutting tool can be integrated to first cut free the legs to be bent, while the complete shape is stamped into the final shape after the legs have been formed becomes. procedure after Claim 18 , whereby the busbars are manufactured in a progressive stamping process.

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