Back contact battery assembly and photovoltaic system

Abstract

The invention relates to the technical field of back contact cells, and particularly discloses a back contact cell assembly and a photovoltaic system.The cell assembly comprises a cell string, a first insulating strip, a second insulating strip, a first electrode, a second electrode and a second electrode, the cell string comprises cells which are connected in series, the cells comprise a first cell and a second cell which are arranged in the first direction, and the first cell is arranged at the end of the cell string; the first insulating strip is arranged at one end, close to the first battery piece, of the second battery piece, the first bus bar is arranged on one side, back on to the second battery piece, of the first insulating strip, the first insulating strip and the first bus bar are arranged in an extending mode in the second direction, and the first welding strip is used for electrically connecting the first bus bar and the first battery piece. The end, close to the first battery piece, of the first bus bar is provided with an extension section, the extension section extends out of the edge of the first insulating strip in the first direction and is electrically connected with the first welding strip, and a connecting end is formed at the connecting position of the extension section and the first welding strip. According to the invention, the effective light-receiving area of the cell module can be increased, the conversion efficiency of the module is improved, the observed area of the bus bar from one side of the light-receiving surface is smaller, even the bus bar can be completely hidden and is more beautiful, meanwhile, the production difficulty can be effectively reduced, the risks of subfissure and fragmentation of the cell piece are reduced, and the reliability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of back-contact batteries, and in particular to a back-contact battery assembly and a photovoltaic system. Background Art

[0002] In existing back-contact battery modules, the series bus bars between adjacent battery strings in series are usually placed at the edge of the battery module, and the parallel bus bars between adjacent battery strings in parallel are usually placed in the reserved spacing area between the two battery strings. This results in the need to reserve a certain amount of space at the edge of the battery module for placing the series bus bars, and a certain amount of space also needs to be reserved between two parallel battery strings for placing the parallel bus bars. On the one hand, this reduces the effective light-receiving area of ​​the battery module and affects the module conversion efficiency. On the other hand, it affects the appearance of the battery cell.

[0003] In some products, the bus bar is installed in the middle position on the back side of the battery cell, and an insulating strip is set between the bus bar and the battery cell. Although this setting can hide the bus bar, it is necessary to make holes in the insulating strip or replace the bus bar with intermittently set insulating blocks so that the bus bar can contact the same polarity welding strip on the battery cell and be insulated from the opposite polarity welding strip on the battery cell. This setting has high requirements on the opening accuracy of the insulating strip and the arrangement position accuracy of the insulating block. It is difficult to produce and is prone to short circuit due to position offset when the insulating strip is opened or the insulating block is laminated. Summary of the invention

[0004] The purpose of the present invention is to provide a back-contact battery assembly and a photovoltaic system in view of the existing technical status.

[0005] The present invention can increase the effective light-receiving area of ​​the battery assembly and improve the conversion efficiency of the assembly. The area of ​​the bus bar observed from the light-receiving side is smaller and can even be completely hidden, which is more beautiful. At the same time, it can effectively reduce the difficulty of production, reduce the risk of hidden cracks and fragments of battery cells, and improve reliability.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] First, the present invention provides a back contact battery assembly, comprising:

[0008] A battery string, wherein the battery string includes battery cells connected in series, the battery cells include a first battery cell and a second battery cell arranged along a first direction, the first battery cell is arranged at an end of the battery string,

[0009] A first insulating strip is provided at one end of the second battery cell close to the first battery cell,

[0010] A first bus bar is provided on a side of the first insulating strip facing away from the second battery cell.

[0011] The first insulating bar and the first bus bar are both extended along a second direction, and the first direction is intersected with the second direction.

[0012] a first welding strip, used for electrically connecting the first bus bar and the first battery cell,

[0013] An extension section is provided at one end of the first bus bar close to the first battery cell. The extension section extends in the first direction to the outside of the edge of the first insulating strip and is electrically connected to the first welding strip. The connection between the extension section and the first welding strip forms a connection end.

[0014] In some embodiments, the first bus bar has a main body, and in the thickness direction of the second battery sheet, the orthographic projection of the main body falls within the orthographic projection of the first insulating strip.

[0015] The relative height distance from the connection end to the first battery cell is smaller than the relative height distance from the side of the main body facing away from the first insulating strip to the first battery cell.

[0016] In some embodiments, the main body and the extension segment are both in the form of long strips extending along the second direction.

[0017] In some embodiments, the extension section includes extension segments, and the extension segments are intermittently arranged along the second direction at one end of the main body close to the first battery cell.

[0018] In some embodiments, the first insulating strip at least partially extends to outside an edge of the second battery cell close to an end of the first battery cell.

[0019] In some embodiments, the connection end is at least partially disposed outside an edge of the second battery cell close to one end of the first battery cell, and in the thickness direction of the second battery cell, the orthographic projection of the connection end at least partially overlaps with the orthographic projection of the first battery cell.

[0020] In some embodiments, the first battery cell and the second battery cell are arranged on the same plane.

[0021] In the first direction, a relative width distance from one end of the second battery cell close to the first battery cell to the connecting end is greater than a distance between the second battery cell and the first battery cell.

[0022] In some embodiments, in the first direction, the relative width distance between the end of the second battery cell close to the first battery cell and the connection end is:

[0023] l11 <L 1 <l 12 ,

[0024] Where, L 1 is the relative width distance from one end of the second battery cell close to the first battery cell to the connection end in the first direction, l 11 is the distance between the second battery cell and the first battery cell, l 12 It is the relative width distance from one end of the second battery cell close to the first battery cell to the first welding point, the first welding point is arranged at one end of the first battery cell close to the second battery cell, and the first welding point is connected to the first welding strip.

[0025] In some embodiments, the first battery cell and the second battery cell are at least partially stacked on an end close to the first battery cell.

[0026] In some embodiments, in the first direction, the relative width distance from one end of the first battery cell close to the second battery cell to the connection end is:

[0027] l 21 <L 2 <l 21 +l 22 ,

[0028] Where, L 2 is the relative width distance from one end of the first battery cell close to the second battery cell to the connection end in the first direction, l 21 is the width of the stacking area of ​​the first battery cell and the second battery cell, l 22 It is the relative width distance from one end of the second battery cell close to the first battery cell to the first welding point, the first welding point is arranged at one end of the first battery cell close to the second battery cell, and the first welding point is connected to the first welding strip.

[0029] In some embodiments, the battery assembly includes at least one series-connected battery string group, each of the series-connected battery string groups includes two battery strings arranged along the second direction and arranged in series with each other,

[0030] Furthermore, in the same series-connected battery string group, the same first bus bar extends from the second battery cell in one battery string to the second battery cell in another battery string.

[0031] In some embodiments, a fourth battery cell is disposed at one end of each battery string away from the first battery cell, and a third battery cell is disposed at one end of the fourth battery cell close to the first battery cell.

[0032] The battery assembly includes a parallel battery string group, each of the parallel battery string groups includes at least two battery strings arranged along a first direction and arranged in parallel with each other, and the fourth battery cells in the two battery strings arranged in parallel with each other are arranged adjacent to each other in the first direction,

[0033] The battery assembly also includes:

[0034] A second insulating strip is provided at an edge of the third battery cell in one of the battery strings, and the second insulating strip is provided at an end of the third battery cell close to the fourth battery cell,

[0035] an intermediate bus bar, used for connecting two battery strings arranged adjacent to each other in a first direction in parallel, the intermediate bus bar being arranged on a side of the second insulating strip facing away from the third battery cell,

[0036] The second insulating strip and the middle bus bar are both extended along the second direction.

[0037] The second welding strip is used to electrically connect the middle bus bar, the fourth battery cell in the battery string, and the fourth battery cell in another battery string adjacent to the battery string in the first direction.

[0038] In some embodiments, an extension section is provided at one end of the intermediate bus bar close to the fourth battery cell, and the extension section extends in the first direction to the edge of the second insulating strip and is electrically connected to the second welding strip. The connection between the extension section and the second welding strip forms a joining end.

[0039] Secondly, the present invention provides a back contact battery assembly, comprising:

[0040] A parallel battery string group, wherein the same parallel battery string group comprises at least two battery strings arranged in a first direction and arranged in parallel with each other, each of the battery strings comprises battery cells connected in series with each other, the battery cells comprise a third battery cell and a fourth battery cell arranged in the first direction, the fourth battery cell is arranged at an end of the battery string, and the fourth battery cells in the two battery strings arranged in parallel with each other are arranged adjacently in the first direction,

[0041] A second insulating strip is provided at an edge of the third battery cell in one of the battery strings, and the second insulating strip is provided at an end of the third battery cell close to the fourth battery cell,

[0042] an intermediate bus bar, used for connecting two battery strings arranged adjacent to each other in a first direction in parallel, the intermediate bus bar being arranged on a side of the second insulating strip facing away from the third battery cell,

[0043] The second insulating strip and the middle bus bar are both extended along the second direction.

[0044] a second welding strip, for electrically connecting the middle bus bar, the fourth battery cell in the battery string where the middle bus bar is located, and the fourth battery cell in another battery string adjacent to the battery string in the first direction,

[0045] An extension section is provided at one end of the middle bus bar close to the fourth battery cell. The extension section extends in the first direction to the outside of the edge of the second insulating strip and is electrically connected to the second welding strip. The connection between the extension section and the second welding strip forms a joint end.

[0046] In some embodiments, the intermediate bus bar is provided with a main matrix, and in the thickness direction of the third battery sheet, the orthographic projection of the main matrix falls within the orthographic projection of the second insulating strip.

[0047] The relative height distance from the joint end to the fourth battery cell is smaller than the relative height distance from the side of the main substrate facing away from the second insulating strip to the fourth battery cell.

[0048] In some embodiments, the main substrate and the extension section are both in the form of a long strip extending along the second direction, or,

[0049] The extension section is disposed on the main substrate and is in a strip-shaped structure extending along the second direction. The extension section includes extension segments, and the extension segments are intermittently arranged along the second direction at one end of the main substrate close to the fourth battery cell.

[0050] In some embodiments, in the thickness direction of the third battery cell, the second insulating strip at least partially extends to the outside of an edge of the third battery cell close to one end of the fourth battery cell.

[0051] In some embodiments, in the battery string provided with the middle bus bar, in the thickness direction of the third battery sheet, the orthographic projection of the joining end at least partially overlaps with the orthographic projection of the fourth battery sheet.

[0052] In some embodiments, in the same battery string, the fourth battery cell and the third battery cell are arranged on the same plane.

[0053] In the battery string provided with the middle bus bar, in the first direction, a relative width distance from one end of the third battery cell close to the fourth battery cell to the joining end is greater than a spacing between the third battery cell and the fourth battery cell.

[0054] In some embodiments, in the battery string provided with the intermediate bus bar, in the first direction, the relative width distance from one end of the third battery cell close to the fourth battery cell to the joint end is:

[0055] l 31 <L 3 <l 32 ,

[0056] Where, L 3 is the relative width distance from one end of the third battery cell close to the fourth battery cell to the joint end in the first direction in the battery string provided with the middle bus bar, l 31 is the distance between the third battery cell and the fourth battery cell in the battery string provided with the middle bus bar, l 32 The relative width distance from the edge of the third battery cell close to one end of the fourth battery cell to the second welding point in the battery string provided with the intermediate bus bar, the second welding point is arranged on the fourth battery cell in the battery string provided with the intermediate bus bar, and is arranged at one end of the fourth battery cell close to the third battery cell, and the second welding point is connected to the second welding strip.

[0057] In some embodiments, the fourth battery cell is at least partially stacked with an end of the third battery cell close to the fourth battery cell.

[0058] In some embodiments, in the battery string provided with the intermediate bus bar, in the first direction, the relative width distance from one end of the fourth battery cell close to the third battery cell to the joint end is:

[0059] l 41 <L 4 <l 41 +l 42 ,

[0060] Where, L 4 is the relative width distance from one end of the fourth battery cell close to the third battery cell to the joint end in the first direction in the battery string provided with the middle bus bar, l 41 is the width of the stacking area of ​​the third battery cell and the fourth battery cell in the battery string provided with the middle bus bar, l 42 In the battery string provided with the intermediate bus bar, the relative width distance from the edge of the third battery cell close to one end of the fourth battery cell to the second welding point, the second welding point is provided at one end of the fourth battery cell close to the third battery cell, and the second welding point is connected to the second welding strip.

[0061] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned back-contact cell assembly.

[0062] The beneficial effects of the present invention are:

[0063] 1) On the one hand, the built-in structure of the end bus bar of the present invention can increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, avoid the exposure of the first bus bar, and make the overall appearance of the battery assembly better; on the other hand, it can ensure that the first welding strip can be fully fitted and welded to the effective welding position of the first battery cell, so as to avoid the installation of the first bus bar causing insufficient welding between the first welding strip and the first battery cell and affecting the current collection. During assembly, it is only necessary to place the entire first insulating strip on the end of the second battery cell close to the first battery cell, which effectively reduces the production precision requirements and production difficulty; furthermore, the built-in structure of the end bus bar of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. The built-in end bus bar and the hanging setting of the extension section make the relative height distance between the connection between the end bus bar and the first welding strip smaller, thereby making the stress of the built-in end bus bar structure smaller during lamination, which can reduce the risk of hidden cracks and fragments of the battery cell, and the reliability of the back contact battery assembly is good.

[0064] 2) On the one hand, the built-in structure of the intermediate bus bar of the present invention can increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, avoid the exposure of the intermediate bus bar, and improve the overall aesthetics of the battery assembly; on the other hand, it can ensure that the second welding strip can be fully fitted and welded to the effective welding position of the fourth battery cell, avoiding the installation of the intermediate bus bar causing insufficient welding between the second welding strip and the fourth battery cell and affecting the current collection. During assembly, it is only necessary to place the entire second insulating strip on the end of the third battery cell close to the fourth battery cell, which effectively reduces the production precision requirements and production difficulty; furthermore, the built-in structure of the intermediate bus bar of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. The built-in intermediate bus bar and the hanging setting of the extension section reduce the relative height distance between the connection between the intermediate bus bar and the second welding strip, thereby making the stress of the built-in structure of the intermediate bus bar smaller during lamination, which can reduce the risk of hidden cracks and fragments of the battery cells, and the reliability of the back contact battery assembly is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic structural diagram of a series-connected battery string group (adjacent battery cells are on the same plane, and the extended section is a long strip structure) according to Example 1 of the present invention.

[0066] Figure 2 Schematic diagram of the structure of the battery string of Example 1 of the present invention.

[0067] Figure 3 It is a schematic structural diagram of a series-connected battery string group (adjacent battery cells are on the same plane, and the epitaxial section includes epitaxial segments) according to Example 1 of the present invention.

[0068] Figure 4 It is a cross-sectional view of the end busbar built-in structure of Example 1 of the present invention.

[0069] Figure 5 It is a schematic structural diagram of the first bus bar (the extension section includes the extension segment) according to Embodiment 1 of the present invention.

[0070] Figure 6 This is a schematic diagram of the structure of the back contact battery assembly of Example 1 of the present invention.

[0071] Figure 7 It is a schematic structural diagram of a parallel battery string group (adjacent battery cells are on the same plane) according to Example 1 of the present invention.

[0072] Figure 8 It is a schematic structural diagram of a series-connected battery string group (adjacent battery cells are stacked) according to Embodiment 2 of the present invention.

[0073] Fig. 9 This is a cross-sectional view of an embodiment of the end busbar built-in structure of embodiment 2 of the present invention.

[0074] Fig.10 It is a cross-sectional view of another embodiment of the end busbar built-in structure of embodiment 2 of the present invention.

[0075] Fig.11 It is a schematic structural diagram of a parallel battery string group (adjacent battery cells are on the same plane) according to Example 3 of the present invention.

[0076] Fig.12 It is a schematic structural diagram of the intermediate bus bar (the extension section includes the extension segment) of Example 3 of the present invention.

[0077] Fig.13 It is a cross-sectional view of the end busbar built-in structure of embodiment 3 of the present invention.

[0078] Fig.14 It is a schematic structural diagram of a parallel battery string group (adjacent battery cells are stacked) according to Example 4 of the present invention.

[0079] Fig.15 It is a cross-sectional view of an embodiment of the intermediate bus bar built-in structure of embodiment 4 of the present invention.

[0080] Fig.16 It is a cross-sectional view of another embodiment of the intermediate bus bar built-in structure of embodiment 4 of the present invention. DETAILED DESCRIPTION

[0081] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0082] In the description of the present application, the terms "first", "second", "third", "fourth", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", "fourth", etc. may explicitly or implicitly include one or more of the features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0083] 1) On the one hand, the built-in structure of the end bus bar of the present invention can increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, avoid the exposure of the first bus bar, and make the overall appearance of the battery assembly better; on the other hand, it can ensure that the first welding strip can be fully fitted and welded to the effective welding position of the first battery cell, so as to avoid the installation of the first bus bar causing insufficient welding between the first welding strip and the first battery cell and affecting the current collection. During assembly, it is only necessary to place the entire first insulating strip on the end of the second battery cell close to the first battery cell, which effectively reduces the production precision requirements and production difficulty; furthermore, the built-in structure of the end bus bar of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. The built-in end bus bar and the hanging setting of the extension section make the relative height distance between the connection between the end bus bar and the first welding strip smaller, thereby making the stress of the built-in end bus bar structure smaller during lamination, which can reduce the risk of hidden cracks and fragments of the battery cell, and the reliability of the back contact battery assembly is good.

[0084] 2) On the one hand, the built-in structure of the intermediate bus bar of the present invention can increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, avoid the exposure of the intermediate bus bar, and improve the overall aesthetics of the battery assembly; on the other hand, it can ensure that the second welding strip can be fully fitted and welded to the effective welding position of the fourth battery cell, avoiding the installation of the intermediate bus bar causing insufficient welding between the second welding strip and the fourth battery cell and affecting the current collection. During assembly, it is only necessary to place the entire second insulating strip on the end of the third battery cell close to the fourth battery cell, which effectively reduces the production precision requirements and production difficulty; furthermore, the built-in structure of the intermediate bus bar of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. The built-in intermediate bus bar and the hanging setting of the extension section reduce the relative height distance between the connection between the intermediate bus bar and the second welding strip, thereby making the stress of the built-in structure of the intermediate bus bar smaller during lamination, which can reduce the risk of hidden cracks and fragments of the battery cells, and the reliability of the back contact battery assembly is good.

[0085] Example 1

[0086] See also Figure 1 , Figure 2 and Figure 4 As shown, this embodiment discloses a back contact battery assembly, including:

[0087] A battery string, the battery string includes battery cells connected in series, the battery cells include a first battery cell 11 and a second battery cell 12 arranged along a first direction, the first battery cell 11 is arranged at the end of the battery string,

[0088] The first insulating strip 21 is disposed at one end of the second battery cell 12 close to the first battery cell 11.

[0089] The first bus bar 31 is disposed on the side of the first insulating strip 21 facing away from the second battery cell 12 (i.e., the back side of the first insulating strip 21; conversely, the side of the first insulating strip 21 facing the second battery cell 12 is the front side of the first insulating strip 21).

[0090] The first insulating strip 21 and the first bus bar 31 are both extended along the second direction, and the first direction and the second direction are intersected.

[0091] The first welding strip 41 is used to electrically connect the first bus bar 31 and the first battery cell 11.

[0092] An extension section 311 is provided at one end of the first bus bar 31 close to the first battery cell 11. The extension section 311 extends in the first direction to the outside of the edge of the first insulating strip 21 and is electrically connected to the first welding strip 41. The connection between the extension section 311 and the first welding strip 41 forms a connection end 312, wherein the electrical connection method can be welding, bonding through conductive adhesive, etc., but is not limited thereto.

[0093] It is understandable that in a battery string, the battery string may include two battery cells connected in series, three battery cells connected in series, or any other greater number of battery cells. The specific number of battery cells to be connected in series may be determined based on actual usage.

[0094] In the present embodiment, the first bus bar 31 is an end bus bar, and the first battery cell 11 is located at the end of the battery string. For ease of explanation, in the present embodiment, the end where the first battery cell 11 is located is recorded as the tail end of the battery string, that is, in the first direction, the first battery cell 11 is the last battery cell of the battery string, and the second battery cell 12 is the second to last battery cell of the battery string. It is not difficult to understand that the end where the first battery cell 11 is located can also be recorded as the head end of the battery string, which will not be repeated here.

[0095] Optionally, in the same battery string, adjacent battery cells can be connected in series by means of welding strips, conductive adhesive, etc.

[0096] In one embodiment, adjacent battery cells are connected by a series welding ribbon 51. Specifically, the series welding ribbon 51 includes a first series welding ribbon 511 and a second series welding ribbon 512. In a first direction, the first series welding ribbon 511 and the second series welding ribbon 512 are alternately arranged. In a second direction, the first series welding ribbon 511 and the second series welding ribbon 512 are alternately arranged. In a battery string, the Nth battery cell, the N+1th battery cell, and the N+2th battery cell (N is a positive integer greater than 1) are arranged in sequence along the first direction, wherein the positive electrode welding point of the Nth battery cell and the negative electrode welding point of the N+1th battery cell are connected in series through multiple first series welding ribbons 511, and the positive electrode welding point of the N+1th battery cell and the negative electrode welding point of the N+2th battery cell are connected in series through multiple second series welding ribbons 512.

[0097] During assembly, the battery cells in the battery string are connected in series with each other, the first insulating strip 21 is arranged at one end of the second battery cell 12 close to the first battery cell 11, the first bus bar 31 is arranged on the back side of the first insulating strip 21, the main body of the first welding strip 41 is electrically connected to the effective welding position of the first battery cell 11, and the end of the first welding strip 41 close to the second battery cell 12 is electrically connected to the first bus bar 31, thereby enabling the first bus bar 31 to draw the current of the battery string.

[0098] First, in the present invention, the first bus bar 31 is arranged on the second battery cell 12, and the first bus bar 31 and the second battery cell 12 are separated by the first insulating strip 21. On the one hand, there is no need to reserve space on the edge of the battery assembly for placing the bus bar, and the battery assembly can reserve more space for installing the battery cells, so that the effective light-receiving area of ​​the battery assembly is larger and the assembly conversion efficiency is higher. On the other hand, when observing from the light-receiving surface (or "front") of the battery cell, the first insulating strip 21 can block the first bus bar 31 to prevent the first bus bar 31 from being exposed, and the overall aesthetics of the battery assembly is better.

[0099] Secondly, compared to setting the bus bar in the middle position on the back of the battery cell, the first bus bar 31 of the present invention is set at the end of the second battery cell 12 close to the first battery cell 11, and the first welding strip 41 can be fully fitted and welded with the effective welding position of the first battery cell 11, thereby avoiding the installation of the first bus bar 31 causing insufficient welding between the first welding strip 41 and the first battery cell 11 and affecting the current collection. At the same time, after the first welding strip 41 is welded to the first battery cell 11, it can be directly connected to the first bus bar 31 without the need to open holes in the insulating strip or replace it with an intermittently arranged insulating block. During assembly, it is only necessary to place the entire first insulating strip 21 on the end of the second battery cell 12 close to the first battery cell 11, which effectively reduces the production precision requirements and production difficulty, and can avoid short circuits caused by position offset when opening holes in the insulating strip or position offset when laminating the insulating blocks, thereby increasing product yield.

[0100] Furthermore, when the bus bar is set at the outer edge of the last battery cell in the battery string, that is, when the first battery cell 11 is away from one end of the second battery cell 12, since the outer edge of the last battery cell in the battery string is close to the edge of the battery assembly, the stress there is relatively large during lamination, which is prone to defects such as fragments. At the same time, the installation of the bus bar will affect the welding between the first welding ribbon 41 and the first battery cell 11. The first welding ribbon 41 cannot be welded to the first battery cell 11 at the position covered by the bus bar, resulting in insufficient welding between the first welding ribbon 41 and the first battery cell 11 and poor current collection. This situation is particularly serious when the battery assembly is a main grid back contact battery assembly.

[0101] In contrast, the end bus bar built-in structure of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and is more versatile. In addition, on the one hand, the end of the second battery cell 12 close to the first battery cell 11 has less stress during lamination than the outer edge of the last battery cell in the battery string. On the other hand, when the connection between the bus bar and the welding strip is located directly above the insulating strip, the relative height distance from the connection between the bus bar and the welding strip to the first battery cell 11 is relatively large, which is easy to break and split. Therefore, the first bus bar 31 of the present invention is provided with an extension section 311 extending outside the first insulating strip 21. After extending to the first insulating strip 21, the extension section 311 can fall down, thereby reducing the relative height distance from the connection between the first bus bar 31 and the first welding strip 41 (connection end 312) to the first battery cell 11, thereby further reducing the risk of hidden cracks and fragments of the battery cells and improving the reliability of the back contact battery assembly.

[0102] In some embodiments, see Figure 1 , Figure 2 and Figure 4 As shown, the first bus bar 31 is provided with a main body 313. In the thickness direction of the second battery sheet 12, the orthographic projection of the main body 313 falls within the orthographic projection of the first insulating strip 21.

[0103] The relative height distance between the connection end 312 and the first battery cell 11 is smaller than the relative height distance between the side of the main body 313 facing away from the first insulating strip 21 and the first battery cell 11 .

[0104] After extending to the first insulating strip 21, the extended section 311 can hang down, so that the relative height distance from the connection end 312 to the first battery cell 11 is smaller than the relative height distance from the side of the main body 313 facing away from the first insulating strip 21 to the first battery cell 11, and the relative height distance from the connection point between the first bus bar 31 and the first welding strip 41 (connection end 312) to the first battery cell 11 becomes smaller, thereby further reducing the risk of hidden cracks and fragments of the battery cell and improving the reliability of the back-contact battery assembly.

[0105] In the first embodiment, see Figure 1 and Figure 2 As shown, the main body 313 and the extension section 311 are both in the form of a long strip extending along the second direction. At this time, the first bus bar 31 can be made into a long rectangular structure as a whole, and the first bus bar 31 does not need to be cut or spliced. It is only necessary to ensure that the first bus bar 31 is insulated from the heterosexual welding strip / heterogenic grid line on the first battery cell 11, and the production process is simpler.

[0106] In the second embodiment, see Figures 3 to 5As shown, the extension section 311 includes an extension segment 314, and the extension segment 314 is intermittently arranged along the second direction at one end of the main body 313 close to the first battery cell 11. The extension segment 311 is made into an intermittently arranged extension segment 314. Compared with the above-mentioned long integrated extension segment 311, on the one hand, the extension segment 314 is easier to fall, and the connection end 312 can achieve a smaller relative height distance at a position closer to the main body 313 of the first bus bar 31. On the other hand, the extension segment 314 can be arranged corresponding to the first welding strip 41, and is staggered and spaced apart from the heterosexual welding strips / heterogenic grid lines on the first battery cell 11, thereby reducing the risk of short circuit and increasing the reliability of the battery assembly.

[0107] For further information, see Figure 5 As shown, the width w of each extension segment 314 in the second direction is 1 1mm≤w 1 ≤5mm, so that each epitaxial segment 314 can be staggered and spaced apart from the anisotropic welding strips / anisotropic grid lines on the first battery cell 11.

[0108] For further information, see Figure 3 As shown, the number of epitaxial segments 314 corresponds to the number of first welding strips 41 , and the spacing between adjacent epitaxial segments 314 corresponds to the spacing between adjacent first welding strips 41 , so that the epitaxial segments 314 are connected to the first welding strips 41 in a one-to-one correspondence.

[0109] In the first embodiment, in the thickness direction of the second battery cell 12 , the orthographic projection of the first insulating strip 21 falls on the second battery cell 12 . At this time, the first insulating strip 21 can insulate and isolate the first bus bar 31 from the welding strip on the second battery cell 12 .

[0110] In the second embodiment, see Figure 4 As shown, the first insulating strip 21 at least partially extends to the edge of the second battery cell 12 near one end of the first battery cell 11. At this time, the first insulating strip 21 can not only ensure that the first bus bar 31 is insulated and isolated from the welding strip on the second battery cell 12, but also ensure that the first welding strip 41 is insulated and isolated from the welding strip on the second battery cell 12, thereby avoiding short circuit and improving the reliability of the battery assembly.

[0111] It can be understood that when the first battery cell 11 and the second battery cell 12 are arranged along the same plane, the portion of the first insulating strip 21 extending outside the edge of the second battery cell 12 can be less than, equal to or greater than the inter-cell spacing between the two battery cells. Preferably, the portion of the first insulating strip 21 extending outside the edge of the second battery cell 12 is greater than the inter-cell spacing between the two battery cells, so as to avoid a short circuit caused by contact between the first bus bar 31 and the anisotropic welding strip / anisotropic grid line on the first battery cell 11, reduce the risk of short circuits easily caused by conductive foreign matter such as tin slag during the preparation process, and improve the reliability of the battery assembly.

[0112] In some embodiments, see Figure 4 As shown, in the thickness direction of the second battery cell 12, the orthographic projection of the connection end 312 at least partially overlaps with the orthographic projection of the first battery cell 11, that is, the orthographic projection of the connection end 312 may partially overlap with the orthographic projection of the first battery cell 11, or the orthographic projection of the connection end 312 may completely fall within the orthographic projection of the first battery cell 11.

[0113] On the one hand, the hanging connection end 312 is kept away from the second battery cell 12, and the first welding strip 41 can be connected to the connection end 312 at a certain distance from the second battery cell 12, thereby avoiding a short circuit caused by contact between the first welding strip 41 and the heterogeneous welding strip / heterogeneous grid line of the second battery cell 12. On the other hand, the connection end 312 can be located at a lower position to reduce the risk of fragments and cracks, thereby further improving the reliability of the battery assembly.

[0114] In some embodiments, see Figure 1 and Figure 4 As shown, the first battery cell 11 and the second battery cell 12 are arranged on the same plane.

[0115] In the first direction, a relative width distance from one end of the second battery cell 12 close to the first battery cell 11 to the connecting end 312 is greater than a spacing between the second battery cell 12 and the first battery cell 11 .

[0116] As a result, the hanging connection end 312 is kept away from the second battery cell 12, and the first welding strip 41 can be connected to the connection end 312 at a certain distance from the second battery cell 12, thereby avoiding the first welding strip 41 from contacting the heterogeneous welding strip / heterogeneous grid line of the second battery cell 12 to cause a short circuit. At the same time, the connection end 312 can be located at a lower position to reduce the risk of fragments and cracks, and further improve the reliability of the battery assembly. In addition, it can also cooperate with the setting of the first insulating strip 21 covering the edge of the first battery cell 11 (that is, the first insulating strip 21 at least partially extends to the edge of the second battery cell 12 close to one end of the first battery cell 11, and the part of the first insulating strip 21 extending to the edge of the second battery cell 12 is greater than the distance between the two battery cells) to avoid the first bus bar 31 from contacting the heterogeneous welding strip / heterogeneous grid line on the first battery cell 11 to cause a short circuit, and the reliability of the battery assembly is better.

[0117] In some embodiments, see Figure 1 and Figure 4 As shown, in the first direction, the relative width distance from the end of the second battery cell 12 close to the first battery cell 11 to the connection end 312 is:

[0118] l 11 <L 1 <l 12 ,

[0119] Where, L 1 is the relative width distance from one end of the second battery cell 12 close to the first battery cell 11 to the connection end 312 in the first direction, l 11 is the distance between the second battery cell 12 and the first battery cell 11, l 12 It is the relative width distance from the end of the second battery cell 12 close to the first battery cell 11 to the first welding point 61 . The first welding point 61 is disposed at the end of the first battery cell 11 close to the second battery cell 12 , and the first welding point 61 is connected to the first welding strip 41 .

[0120] It can be understood that the first welding point 61 is located at the effective welding position of the first battery cell 11 and is closest to the edge of the second battery cell 12. 1 Greater than l 11 and less than l 12 , so that the connection end 312 can maintain a relatively long distance away from the second battery cell 12 while ensuring that it does not exceed the effective welding position of the first battery cell 11, thereby effectively reducing the relative height of the connection end 312, and the first welding ribbon 41 can be connected to the connection end 312 at a certain distance from the second battery cell 12, and can ensure sufficient contact and welding between the first welding ribbon 41 and the first battery cell 11, thereby reducing the risk of fragments and cracks while avoiding short circuits, so that the battery assembly can maintain a high reliability.

[0121] In some embodiments, see Figure 1 and Figure 4 As shown, more preferably, in the first direction, the relative width distance from the end of the second battery cell 12 close to the first battery cell 11 to the connection end 312 is:

[0122] l 11 <L 1 <l 12 ,

[0123] Where, L 1 is the relative width distance from one end of the second battery cell 12 close to the first battery cell 11 to the connection end 312 in the first direction, l 11 is the distance between the second battery cell 12 and the first battery cell 11, l 12 It is the relative width distance from the end of the second battery cell 12 close to the first battery cell 11 to the first welding point 61 . The first welding point 61 is disposed at the end of the first battery cell 11 close to the second battery cell 12 , and the first welding point 61 is connected to the first welding strip 41 .

[0124] By controlling L 1 Greater than l 11 and less than l 12 , within this range, the reliability of the battery assembly is better.

[0125] In some embodiments, see Figure 1 and Figure 6 As shown, the battery assembly includes at least one series-connected battery string group 100, each of which includes two battery strings arranged in a second direction and connected in series with each other.

[0126] Furthermore, in the same series-connected battery string 100 , the same first bus bar 31 extends from the second battery cell 12 in one battery string to the second battery cell 12 in another battery string.

[0127] Furthermore, the first welding strip 41 includes a first positive welding strip 411 and a first negative welding strip 412. The same first bus bar 31 is electrically connected to the first positive welding strip 411 in one battery string and is electrically connected to the first negative welding strip 412 in another battery string, so that adjacent battery strings are connected in series.

[0128] Exemplarily, the same series battery string group 100 includes a first battery string 10A and a second battery string 10B, and the first welding strip 41 includes a first positive electrode welding strip 411 and a first negative electrode welding strip 412. In the same series battery string group 100, the same first bus bar 31 extends from the second battery cell 12 in the first battery string 10A to the second battery cell 12 in the second battery string 10B, and in the first battery string 10A, the first bus bar 31 is electrically connected to the first positive electrode welding strip 411 on the first battery cell 11, and in the second battery string 10B, the first bus bar 31 is electrically connected to the first negative electrode welding strip 412 on the first battery cell 11.

[0129] In one embodiment, the battery assembly includes a parallel battery string group 200, and the same parallel battery string group 200 includes at least two battery strings arranged along a first direction and arranged in parallel with each other, and a spacing area is set between the two battery strings arranged in parallel with each other, and an intermediate bus bar 32 is provided in the spacing area. The intermediate bus bar 32 is used to connect two battery strings adjacent to each other in the first direction in parallel, that is, the end bus bar built-in structure of the present invention can cooperate with the conventional intermediate bus bar 32 installation structure.

[0130] In another more preferred embodiment, see Figure 6 and Figure 7 As shown, each battery string is provided with a fourth battery cell 14 at one end away from the first battery cell 11, and a third battery cell 13 is provided at one end of the fourth battery cell 14 close to the first battery cell 11.

[0131] The battery assembly includes a parallel battery string group 200, and the same parallel battery string group 200 includes at least two battery strings arranged along a first direction and arranged in parallel with each other, and the fourth battery cells 14 in the two battery strings arranged in parallel with each other are arranged adjacent to each other in the first direction.

[0132] The battery assembly also includes:

[0133] The second insulating strip 22 is disposed at the edge of the third battery cell 13 in a battery string, and the second insulating strip 22 is disposed at one end of the third battery cell 13 close to the fourth battery cell 14.

[0134] The middle bus bar 32 is used to connect two battery strings arranged adjacent to each other in the first direction in parallel. The middle bus bar 32 is arranged on the side of the second insulating strip 22 facing away from the third battery cell 13.

[0135] The second insulating strip 22 and the middle bus bar 32 are both extended along the second direction.

[0136] The second welding strip 42 is used to electrically connect the middle bus bar 32 , the fourth battery cell 14 in the battery string, and the fourth battery cell 14 in another battery string adjacent to the battery string in the first direction.

[0137] For example, for ease of explanation, the third battery string 20A and the fourth battery string 20B connected in parallel in the same parallel battery string group 200 are taken as an example, wherein the third battery string 20A is the battery string where the middle bus bar 32 is located:

[0138] The third battery cell 13 in the third battery string 20A is recorded as the third battery cell 13A, the fourth battery cell 14 is recorded as the fourth battery cell 14A, the third battery cell 13 in the fourth battery string 20B is recorded as the third battery cell 13B, the fourth battery cell 14 is recorded as the fourth battery cell 14B, the third battery string 20A and the fourth battery string 20B are arranged along the first direction, the fourth battery cell 14A and the fourth battery cell 14B are adjacently arranged in the first direction,

[0139] The battery assembly also includes:

[0140] The second insulating strip 22 is disposed at the edge of the third battery cell 13A in the third battery string 20A, and the second insulating strip 22 is disposed at one end of the third battery cell 13A close to the fourth battery cell 14A.

[0141] The middle bus bar 32 is used to connect the third battery string 20A and the fourth battery string 20B in parallel. The middle bus bar 32 is arranged on the side of the second insulating strip 22 facing away from the third battery cell 13.

[0142] The second insulating strip 22 and the middle bus bar 32 are both extended along the second direction.

[0143] The second welding ribbon 42 is used to electrically connect the middle bus bar 32 , the fourth battery cell 14A and the fourth battery cell 14B. That is, the same second welding ribbon 42 extends from the fourth battery cell 14B to the fourth battery cell 14A and the center bus bar in sequence.

[0144] Furthermore, the second welding strip 42 includes a second positive electrode welding strip 421 and a second negative electrode welding strip 422 , and the fourth battery cell 14A, the fourth battery cell 14B and the central bus bar are electrically connected through the second positive electrode welding strip 421 or the second negative electrode welding strip 422 .

[0145] On the one hand, the built-in structure of the intermediate bus bar of the present invention can increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, avoid exposure of the intermediate bus bar 32, and improve the overall aesthetics of the battery assembly; on the other hand, it can ensure that the second welding strip 42 can be fully bonded and welded to the effective welding position of the fourth battery cell 14, and avoid the installation of the intermediate bus bar 32 causing insufficient welding between the second welding strip 42 and the fourth battery cell 14 and affecting the current collection. During assembly, it is only necessary to place the entire first insulating strip 21 on the end of the third battery cell 13 close to the fourth battery cell 14, which effectively reduces the production precision requirements and production difficulty; furthermore, the built-in structure of the intermediate bus bar of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. The stress of the built-in structure of the intermediate bus bar is smaller during lamination, which can reduce the risk of hidden cracks and fragments of the battery cells, and the reliability of the back contact battery assembly is good.

[0146] The built-in structure of the end bus bar of the present invention cooperates with the built-in structure of the middle bus bar of the present invention to increase the effective light-receiving area of ​​the battery assembly, improve the conversion efficiency of the assembly, improve the overall aesthetics and reliability of the battery assembly, effectively reduce the production precision requirements and production difficulty, and improve production efficiency.

[0147] In some embodiments, see Figure 7 As shown, an extension section 321 is provided at one end of the intermediate bus bar 32 close to the fourth battery cell 14. The extension section 321 extends in the first direction to the edge of the second insulating strip 22 and is electrically connected to the second welding strip 42. The connection between the extension section 321 and the second welding strip 42 forms a joint end 322.

[0148] The intermediate bus bar built-in structure of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and has stronger versatility. On the one hand, the end of the third battery cell 13 close to the fourth battery cell 14 has less stress during lamination than the outer edge of the last battery cell in the battery string. On the other hand, when the connection between the bus bar and the welding strip is located directly above the insulating strip, the relative height distance from the connection between the bus bar and the welding strip to the first battery cell 11 is relatively large, which is easy to break and split. Therefore, the intermediate bus bar 32 of the present invention is provided with an extension section 321 extending outside the second insulating strip 22. After extending to the second insulating strip 22, the extension section 321 can fall down, thereby reducing the relative height distance from the connection between the intermediate bus bar 32 and the second welding strip 42 (joining end 322) to the third battery cell 13, thereby further reducing the risk of hidden cracks and fragments of the battery cells and improving the reliability of the back contact battery assembly.

[0149] Furthermore, the present invention provides a photovoltaic system, comprising the above-mentioned back-contact cell assembly.

[0150] Example 2

[0151] The difference between this embodiment and embodiment 1 is that, see Figures 8 to 10 As shown, the first battery cell 11 and the second battery cell 12 are at least partially stacked on one end close to the first battery cell 11 .

[0152] That is, the first battery cell 11 and the second battery cell 12 are stacked, and there is no gap between the two batteries.

[0153] In one embodiment, see Fig. 9 As shown, the side of the second battery cell 12 facing the first insulating strip 21 is at least partially stacked with the first battery cell 11 .

[0154] In another embodiment, see Fig.10 As shown, the side of the second battery cell 12 facing away from the first insulating strip 21 is at least partially stacked with the first battery cell 11 .

[0155] In the first embodiment, in the thickness direction of the second battery cell 12 , the orthographic projection of the first insulating strip 21 falls on the second battery cell 12 . At this time, the first insulating strip 21 can insulate and isolate the first bus bar 31 from the welding strip on the second battery cell 12 .

[0156] In the second embodiment, the first insulating strip 21 at least partially extends to the edge of the second battery cell 12 near one end of the first battery cell 11. At this time, the first insulating strip 21 can not only ensure that the first bus bar 31 is insulated and isolated from the welding strip on the second battery cell 12, but also ensure that the first welding strip 41 is insulated and isolated from the welding strip on the second battery cell 12, thereby avoiding short circuit and improving the reliability of the battery assembly.

[0157] When the first battery cell 11 and the second battery cell 12 at least partially overlap, that is, when the first battery cell 11 and the second battery cell 12 are stacked, the portion of the first insulating strip 21 extending outside the edge of the second battery cell 12 may be less than, equal to or greater than the width of the stacking area of ​​the two battery cells. Preferably, the portion of the first insulating strip 21 extending outside the edge of the second battery cell 12 is greater than the width of the stacking area of ​​the two battery cells to avoid short circuit caused by contact between the first bus bar 31 and the heterogeneous welding strip / heterogeneous grid line on the first battery cell 11, thereby improving the reliability of the battery assembly.

[0158] In some embodiments, see Fig. 9 and Fig.10 As shown, in the first direction, the relative width distance from the end of the first battery cell 11 close to the second battery cell 12 to the connection end 312 is:

[0159] l 21 <L 2 <l 21 +l 22 ,

[0160] Where, L 2 is the relative width distance from one end of the first battery cell 11 close to the second battery cell 12 to the connection end 312 in the first direction, l 21 is the width of the stacking area of ​​the first battery cell 11 and the second battery cell 12, l 22 It is the relative width distance from one end of the second battery cell 12 close to the first battery cell 11 to the first welding point 61 . The first welding point 61 is disposed at one end of the first battery cell 11 close to the second battery cell 12 , and the first welding point 61 is connected to the first welding strip 41 .

[0161] It can be understood that the first welding point 61 is located at the effective welding position of the first battery cell 11 and is closest to the edge of the second battery cell 12. 2 Greater than or equal to l 21 and less than l 22 , so that the connection end 312 can maintain a relatively long distance away from the second battery cell 12 while ensuring that it does not exceed the effective welding position of the first battery cell 11, thereby effectively reducing the relative height of the connection end 312, and the first welding ribbon 41 can be connected to the connection end 312 at a certain distance from the second battery cell 12, and can ensure sufficient contact and welding between the first welding ribbon 41 and the first battery cell 11, thereby reducing the risk of fragments and cracks while avoiding short circuits, so that the battery assembly can maintain a high reliability.

[0162] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the back contact battery described above can refer to the corresponding structure and implementation principle in the aforementioned embodiment 1, and will not be repeated here.

[0163] Example 3

[0164] See also Fig.11 and Fig.13 As shown, this embodiment discloses a back contact battery assembly, including:

[0165] A parallel battery string group 200, wherein the same parallel battery string group 200 includes at least two battery strings arranged in a first direction and arranged in parallel with each other, each battery string includes battery cells connected in series, the battery cells include a third battery cell 13 and a fourth battery cell 14 arranged in the first direction, the fourth battery cell 14 is arranged at the end of the battery string, and the fourth battery cells 14 in the two battery strings arranged in parallel are adjacently arranged in the first direction,

[0166] The second insulating strip 22 is disposed at the edge of the third battery cell 13 in a battery string, and the second insulating strip 22 is disposed at one end of the third battery cell 13 close to the fourth battery cell 14.

[0167] The middle bus bar 32 is used to connect two battery strings arranged adjacent to each other in the first direction in parallel. The middle bus bar 32 is arranged on the side of the second insulating strip 22 facing away from the third battery cell 13.

[0168] The second insulating strip 22 and the middle bus bar 32 are both extended along the second direction.

[0169] The second welding strip 42 is used to electrically connect the middle bus bar 32, the fourth battery cell 14 in the battery string where the middle bus bar 32 is located, and the fourth battery cell 14 in another battery string adjacent to the battery string in the first direction.

[0170] An extension section 321 is provided at one end of the middle bus bar 32 close to the fourth battery cell 14 . The extension section 321 extends in the first direction to the edge of the second insulating strip 22 and is electrically connected to the second welding strip 42 . The connection between the extension section 321 and the second welding strip 42 forms a joint end 322 .

[0171] For example, for ease of explanation, the third battery string 20A and the fourth battery string 20B connected in parallel in the same parallel battery string group 200 are taken as an example, wherein the third battery string 20A is the battery string where the middle bus bar 32 is located:

[0172] The third battery cell 13 in the third battery string 20A is recorded as the third battery cell 13A, the fourth battery cell 14 is recorded as the fourth battery cell 14A, the third battery cell 13 in the fourth battery string 20B is recorded as the third battery cell 13B, the fourth battery cell 14 is recorded as the fourth battery cell 14B, the third battery string 20A and the fourth battery string 20B are arranged along the first direction, the fourth battery cell 14A and the fourth battery cell 14B are adjacently arranged in the first direction,

[0173] The battery assembly also includes:

[0174] The second insulating strip 22 is disposed at the edge of the third battery cell 13A in the third battery string 20A, and the second insulating strip 22 is disposed at one end of the third battery cell 13A close to the fourth battery cell 14A.

[0175] The middle bus bar 32 is used to connect the third battery string 20A and the fourth battery string 20B in parallel. The middle bus bar 32 is arranged on the side of the second insulating strip 22 facing away from the third battery cell 13.

[0176] The second insulating strip 22 and the middle bus bar 32 are both extended along the second direction.

[0177] The second welding strip 42 is used to electrically connect the middle bus bar 32, the fourth battery cell 14A and the fourth battery cell 14B. That is, the same second welding strip 42 extends from the fourth battery cell 14B to the fourth battery cell 14A and the center bus bar in sequence.

[0178] An extension section 321 is provided at one end of the middle bus bar 32 close to the fourth battery cell 14A. The extension section 321 extends in the first direction to the edge of the second insulating strip 22 and is electrically connected to the second welding strip 42 . The connection between the extension section 321 and the second welding strip 42 forms a joint end 322 .

[0179] During assembly, the battery cells in the battery string are connected in series with each other, the second insulating strip 22 is arranged at one end of the third battery cell 13A close to the fourth battery cell 14A, the intermediate bus bar 32 is arranged on the back of the second insulating strip 22, the main body of the second welding strip 42 is electrically connected to the effective welding position of the fourth battery cell 14A and the effective welding position of the fourth battery cell 14B respectively, and the end of the second welding strip 42 close to the third battery cell 13A is electrically connected to the intermediate bus bar 32, thereby enabling the intermediate bus bar 32 to connect the third battery string 20A and the fourth battery string 20B in parallel.

[0180] First, in the present invention, the middle bus bar 32 is arranged on the third battery cell 13A, and the middle bus bar 32 and the third battery cell 13A are separated by the second insulating strip 22. On the one hand, there is no need to reserve space on the edge of the battery assembly for placing the bus bar, and the battery assembly can reserve more space for installing the battery cells, so that the effective light-receiving area of ​​the battery assembly is larger and the assembly conversion efficiency is higher. On the other hand, when observing from the light-receiving surface (or "front") of the battery cell, the second insulating strip 22 can block the middle bus bar 32 to prevent the middle bus bar 32 from being exposed, and the overall aesthetics of the battery assembly is better.

[0181] Secondly, compared to setting the bus bar in the middle position on the back of the battery cell, the intermediate bus bar 32 of the present invention is set at one end of the third battery cell 13A close to the fourth battery cell 14A, and the second welding strip 42 extends to the fourth battery cell 14A after being connected to the effective welding position of the fourth battery cell 14B, and can be fully fitted and welded with the effective welding position of the fourth battery cell 14A, thereby avoiding the installation of the intermediate bus bar 32 causing insufficient welding between the second welding strip 42 and the fourth battery cell 14A, thereby affecting the current collection. At the same time, after the second welding strip 42 is welded to the fourth battery cell 14A and the fourth battery cell 14B, it can be directly connected to the intermediate bus bar 32 without the need to perform hole processing on the insulating strip or replace it with an intermittently arranged insulating block. During assembly, it is only necessary to place the entire second insulating strip 22 on one end of the third battery cell 13A close to the fourth battery cell 14A, thereby effectively reducing the production precision requirements and production difficulty, and can avoid short circuits caused by position offset when the insulating strip is opened or the insulating block is laminated, thereby increasing product yield.

[0182] Furthermore, when the bus bar is set at the outer edge of the last battery cell in the battery string, that is, when the fourth battery cell 14A is away from one end of the third battery cell 13A, the stress at the outer edge of the last battery cell in the battery string is relatively large when it is laminated, which is prone to produce defects such as fragments. At the same time, the installation of the bus bar will affect the welding between the second welding ribbon 42 and the fourth battery cell 14A. The second welding ribbon 42 cannot be welded to the fourth battery cell 14A at the position covered by the bus bar, resulting in insufficient welding between the second welding ribbon 42 and the fourth battery cell 14A and poor current collection. This situation is particularly serious when the battery module is a main grid back contact battery module.

[0183] In contrast, the intermediate bus bar built-in structure of the present invention can be applied to battery assemblies with main grid back contact and battery assemblies without main grid back contact, and is more versatile. In addition, on the one hand, the end of the third battery cell 13A close to the fourth battery cell 14A has less stress during lamination than the outer edge of the last battery cell in the battery string. On the other hand, when the connection between the bus bar and the welding strip is located directly above the insulating strip, the relative height distance from the connection between the bus bar and the welding strip to the fourth battery cell 14 is relatively large, which is easy to break and split. Therefore, the intermediate bus bar 32 of the present invention is provided with an extension section 311 extending outside the second insulating strip 22. After extending to the second insulating strip 22, the extension section 311 can fall down, thereby reducing the relative height distance from the connection between the intermediate bus bar 32 and the second welding strip 42 (connection end 312) to the fourth battery cell 14A, thereby further reducing the risk of hidden cracks and fragments of the battery cells and improving the reliability of the back contact battery assembly.

[0184] Furthermore, the second welding strip 42 includes a second positive electrode welding strip 421 and a second negative electrode welding strip 422 , and the fourth battery cell 14A, the fourth battery cell 14B and the central bus bar are electrically connected through the second positive electrode welding strip 421 or the second negative electrode welding strip 422 .

[0185] In some embodiments, see Fig.13 As shown, the middle bus bar 32 is provided with a main substrate 323. In the thickness direction of the third battery cell 13, the orthographic projection of the main substrate 323 falls within the orthographic projection of the second insulating strip 22.

[0186] The relative height distance between the joint end 322 and the fourth battery cell 14 is smaller than the relative height distance between the side of the main substrate 323 facing away from the second insulating strip 22 and the fourth battery cell 14 .

[0187] After extending to the second insulating strip 22, the extension section 321 can hang down, so that the relative height distance from the joining end 322 to the fourth battery cell 14A is smaller than the relative height distance from the side of the main substrate 323 facing away from the second insulating strip 22 to the fourth battery cell 14A, and the relative height distance from the connection between the intermediate bus bar 32 and the second welding strip 42 (joint end 322) to the fourth battery cell 14A becomes smaller, thereby further reducing the risk of hidden cracks and fragments of the battery cell and improving the reliability of the back-contact battery assembly.

[0188] In the first embodiment, see Fig.11 As shown, the main base 323 and the extension section 321 are both in a long strip structure extending along the second direction.

[0189] At this time, the middle bus bar 32 can be made into a long rectangular structure as a whole. There is no need to cut or splice the middle bus bar 32. It only needs to ensure the insulation between the middle bus bar 32 and the heterogeneous welding strip / heterogeneous grid line on the fourth battery cell 14A, which makes the production process simpler.

[0190] In the second embodiment, see Fig.12 As shown, the extension section 321 includes extension segments 324 , and the extension segments 324 are intermittently arranged along the second direction at one end of the main substrate 323 close to the fourth battery cell 14 .

[0191] The extension section 321 is made into an intermittently arranged extension segment 324. Compared with the above-mentioned long integrated extension segment 321, on the one hand, the extension segment 324 is easier to hang down, and the joint end 322 can achieve a smaller relative height distance at a position closer to the main substrate 323 of the middle bus bar 32. On the other hand, the extension segment 324 can be set corresponding to the second welding strip 42 and staggered and spaced apart from the heterosexual welding strips / heterogenic grid lines on the fourth battery cell 14A, thereby reducing the risk of short circuit and increasing the reliability of the battery assembly.

[0192] Furthermore, the width w of each extension segment 324 in the second direction is 2 1mm≤w 2 ≤5mm, so that each extended segment 324 can be staggered and spaced apart from the anisotropic welding strips / anisotropic grid lines on the fourth battery cell 14A.

[0193] Furthermore, the number of extension segments 324 corresponds to the number of second welding strips 42 , and the spacing between adjacent extension segments 324 corresponds to the spacing between adjacent second welding strips 42 , so that the extension segments 324 are connected to the second welding strips 42 in a one-to-one correspondence.

[0194] In the first embodiment, in the thickness direction of the third battery cell 13 , the orthographic projection of the second insulating strip 22 falls on the third battery cell 13 . At this time, the second insulating strip 22 can insulate and isolate the middle bus bar 32 from the welding strip on the third battery cell 13 .

[0195] In the second embodiment, the second insulating strip 22 at least partially extends to the edge of the third battery cell 13 near the end of the fourth battery cell 14. At this time, the second insulating strip 22 can not only ensure that the intermediate bus bar 32 is insulated and isolated from the welding strip on the fourth battery cell 14, but also ensure that the second welding strip 42 is insulated and isolated from the welding strip on the third battery cell 13, thereby avoiding short circuit and improving the reliability of the battery assembly.

[0196] It can be understood that when the third battery cell 13 and the fourth battery cell 14 are arranged along the same plane, the portion of the second insulating strip 22 extending outside the edge of the third battery cell 13 can be less than, equal to or greater than the distance between the two battery cells. Preferably, the portion of the second insulating strip 22 extending outside the edge of the third battery cell 13 is greater than the distance between the two battery cells to avoid short circuit caused by contact between the intermediate bus bar 32 and the heterogeneous welding strip / heterogeneous grid line on the fourth battery cell 14, thereby improving the reliability of the battery assembly.

[0197] In some embodiments, see Fig.13 As shown, in a battery string provided with an intermediate bus bar 32, in the thickness direction of the third battery cell 13, the orthographic projection of the joining end 322 at least partially overlaps with the orthographic projection of the fourth battery cell 14, that is, in the third battery string 20A, in the thickness direction of the third battery cell 13A, the orthographic projection of the joining end 322 at least partially overlaps with the orthographic projection of the fourth battery cell 14A.

[0198] It can be understood that the orthographic projection of the bonding end 322 may partially overlap with the orthographic projection of the fourth battery cell 14A, or the orthographic projection of the bonding end 322 may completely fall within the orthographic projection of the fourth battery cell 14A.

[0199] On the one hand, the hanging joint end 322 is kept away from the third battery cell 13A, and the second welding strip 42 can be connected to the joint end 322 at a certain distance from the third battery cell 13A, thereby avoiding a short circuit caused by contact between the second welding strip 42 and the heterogeneous welding strip / heterogeneous grid line of the third battery cell 13A. On the other hand, the joint end 322 can be located at a lower position to reduce the risk of fragments and cracks, thereby further improving the reliability of the battery assembly.

[0200] In some embodiments, see Fig.13 As shown, in the same battery string, the fourth battery cell 14 and the third battery cell 13 are arranged on the same plane.

[0201] In the battery string with the middle bus bar 32 , in the first direction, the relative width distance from the end of the third battery cell 13 close to the fourth battery cell 14 to the joint end 322 is greater than the spacing between the third battery cell 13 and the fourth battery cell 14 .

[0202] In this way, the hanging joint end 322 is kept away from the third battery cell 13A, and the second welding strip 42 can be connected to the joint end 322 at a certain distance from the third battery cell 13A, thereby preventing the second welding strip 42 from contacting the heterogeneous welding strip / heterogeneous grid line of the third battery cell 13A to cause a short circuit. At the same time, the joint end 322 can be located at a lower position to reduce the risk of fragments and cracks, and further improve the reliability of the battery assembly. In addition, it can also cooperate with the setting of the second insulating strip 22 covering the edge of the fourth battery cell 14A (that is, the second insulating strip 22 at least partially extends to the edge of the third battery cell 13A close to one end of the fourth battery cell 14A, and the part of the second insulating strip 22 extending to the edge of the third battery cell 13A is greater than the spacing between the two battery cells) to prevent the middle bus bar 32 from contacting the heterogeneous welding strip / heterogeneous grid line on the fourth battery cell 14A to cause a short circuit, and the reliability of the battery assembly is better.

[0203] In some embodiments, see Fig.13As shown, in the battery string provided with the middle bus bar 32, in the first direction, the relative width distance from the end of the third battery cell 13 close to the fourth battery cell 14 to the joint end 322 is:

[0204] l 31 <L 3 <l 32 ,

[0205] Where, L 3 is the relative width distance from one end of the third battery cell 13 (third battery cell 13A) close to the fourth battery cell 14 (fourth battery cell 14A) to the joint end 322 in the first direction in the battery string provided with the middle bus bar 32, l 31 is the distance between the third battery cell 13 (third battery cell 13A) and the fourth battery cell 14 (fourth battery cell 14A) in the battery string provided with the middle bus bar 32, l 32 It is the relative width distance from the edge of the third battery cell 13 (third battery cell 13A) close to one end of the fourth battery cell 14 (fourth battery cell 14A) to the second welding point 62 in the battery string provided with the intermediate bus bar 32. The second welding point 62 is arranged on the fourth battery cell 14 (fourth battery cell 14A) in the battery string provided with the intermediate bus bar 32, and is arranged at one end of the fourth battery cell 14 (fourth battery cell 14A) close to the third battery cell 13 (third battery cell 13A), and the second welding point 62 is connected to the second welding strip 42.

[0206] It can be understood that the second welding point 62 is located at the effective welding position of the fourth battery cell 14A closest to the edge of the third battery cell 13A. 2 Greater than or equal to l 21 and less than l 22 , so that the joint end 322 can maintain a relatively long distance away from the third battery cell 13A while ensuring that it does not exceed the effective welding position of the fourth battery cell 14A, thereby effectively reducing the relative height of the joint end 322, and the second welding strip 42 can be connected to the joint end 322 at a certain distance from the third battery cell 13A, and can ensure sufficient contact and welding between the second welding strip 42 and the fourth battery cell 14A, thereby reducing the risk of fragments and cracks while avoiding short circuits, so that the battery assembly can maintain a high reliability.

[0207] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the back contact battery described above can refer to the corresponding structure and implementation principle in the aforementioned embodiment 1, and will not be repeated here.

[0208] Example 4

[0209] The difference between this embodiment and embodiment 3 is that, see Figures 14 to 16 As shown, the fourth battery cell 14 is at least partially stacked with an end of the third battery cell 13 close to the fourth battery cell 14 .

[0210] That is, the third battery cell 13A and the fourth battery cell 14A are stacked, and there is no gap between the two batteries.

[0211] In one embodiment, see Fig.15 As shown, the side of the third battery cell 13A facing the first insulating strip 21 is at least partially stacked with the fourth battery cell 14A.

[0212] In another embodiment, see Fig.16 As shown, the side of the third battery cell 13A facing away from the second insulating strip 22 is at least partially stacked with the fourth battery cell 14A.

[0213] In the first embodiment, in the thickness direction of the third battery cell 13A, the orthographic projection of the second insulating strip 22 falls on the third battery cell 13A. At this time, the second insulating strip 22 can insulate and isolate the middle bus bar 32 from the welding strip on the third battery cell 13A.

[0214] In the second embodiment, the second insulating strip 22 at least partially extends to the edge of the third battery cell 13A near the end of the fourth battery cell 14A. At this time, the second insulating strip 22 can not only ensure that the intermediate bus bar 32 is insulated and isolated from the welding strip on the third battery cell 13A, but also ensure that the first welding strip 41 is insulated and isolated from the welding strip on the third battery cell 13A, thereby avoiding short circuits and improving the reliability of the battery assembly.

[0215] When the fourth battery cell 14A at least partially overlaps with the third battery cell 13A, that is, when the fourth battery cell 14A and the third battery cell 13A are stacked, the portion of the second insulating strip 22 extending outside the edge of the third battery cell 13A may be less than, equal to or greater than the width of the stacking area of ​​the two battery cells. Preferably, the portion of the second insulating strip 22 extending outside the edge of the third battery cell 13A is greater than the width of the stacking area of ​​the two battery cells to avoid short circuit caused by contact between the intermediate bus bar 32 and the heterogeneous welding strip / heterogeneous grid line on the fourth battery cell 14A, thereby improving the reliability of the battery assembly.

[0216] In some embodiments, see Fig.15 and Fig.16 As shown, in the battery string provided with the middle bus bar 32, in the first direction, the relative width distance from the end of the fourth battery cell 14 close to the third battery cell 13 to the joint end 322 is:

[0217] l 41 <L 4 <l 41 +l 42 ,

[0218] Where, L 4 is the relative width distance from one end of the fourth battery cell 14 (fourth battery cell 14A) close to the third battery cell 13 (third battery cell 13A) to the joint end 322 in the first direction in the battery string provided with the middle bus bar 32, 41 is the width of the stacking region of the third battery cell 13 (third battery cell 13A) and the fourth battery cell 14 (fourth battery cell 14A) in the battery string provided with the middle bus bar 32, and l 42 It is the relative width distance from the edge of the third battery cell 13 (third battery cell 13A) close to one end of the fourth battery cell 14 (fourth battery cell 14A) to the second welding point 62 in the battery string provided with the middle bus bar 32. The second welding point 62 is provided at one end of the fourth battery cell 14 (fourth battery cell 14A) close to the third battery cell 13 (third battery cell 13A), and the second welding point 62 is connected to the second welding strip 42.

[0219] It can be understood that the second welding point 62 is located at the effective welding position of the fourth battery cell 14 (fourth battery cell 14A) closest to the edge of the third battery cell 13 (third battery cell 13A). 2 Greater than or equal to l 21 and less than l 22 , so that the connection end 312 can maintain a relatively long distance away from the third battery cell 13 (third battery cell 13A) while ensuring that it does not exceed the effective welding position of the fourth battery cell 14 (fourth battery cell 14A), thereby effectively reducing the relative height of the connection end 312, and the second welding ribbon 42 can be connected to the connection end 312 at a certain distance from the third battery cell 13 (third battery cell 13A), and can ensure sufficient contact and welding between the second welding ribbon 42 and the fourth battery cell 14 (fourth battery cell 14A), thereby reducing the risk of fragments and cracks while avoiding short circuits, so that the battery assembly can maintain a high reliability.

[0220] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the back contact battery described above can refer to the corresponding structure and implementation principle in the aforementioned embodiments 1 and 3, and will not be repeated here.

[0221] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0222] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with the field can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A back contact battery assembly, It is characterized in that include: A battery string, wherein the battery string includes battery cells connected in series, the battery cells include a first battery cell and a second battery cell arranged along a first direction, the first battery cell is arranged at an end of the battery string, A first insulating strip is provided at one end of the second battery cell close to the first battery cell, A first bus bar is provided on a side of the first insulating strip facing away from the second battery cell. The first insulating bar and the first bus bar are both extended along a second direction, and the first direction is intersected with the second direction. a first welding strip, used for electrically connecting the first bus bar and the first battery cell, An extension section is provided at one end of the first bus bar close to the first battery cell. The extension section extends in the first direction to the outside of the edge of the first insulating strip and is electrically connected to the first welding strip. The connection between the extension section and the first welding strip forms a connection end.

2. A back contact battery assembly according to claim 1, It is characterized in that The first bus bar has a main body, and in the thickness direction of the second battery sheet, the orthographic projection of the main body falls within the orthographic projection of the first insulating strip, The relative height distance from the connection end to the first battery cell is smaller than the relative height distance from the side of the main body facing away from the first insulating strip to the first battery cell.

3. A back contact battery assembly according to claim 2, It is characterized in that The main body and the extension section are both in a long strip structure extending along the second direction.

4. A back contact battery assembly according to claim 2, It is characterized in that The epitaxial section includes epitaxial segments, and the epitaxial segments are intermittently arranged along the second direction at one end of the main body close to the first battery cell.

5. A back contact battery assembly according to claim 1, It is characterized in that The first insulating strip at least partially extends outside an edge of the second battery cell close to one end of the first battery cell.

6. A back contact battery assembly according to claim 1, It is characterized in that The connection end is at least partially disposed outside an edge of the second battery cell close to one end of the first battery cell, and in a thickness direction of the second battery cell, an orthographic projection of the connection end at least partially overlaps with an orthographic projection of the first battery cell.

7. A back contact battery assembly according to claim 6, It is characterized in that The first battery cell and the second battery cell are arranged on the same plane. In the first direction, a relative width distance from one end of the second battery cell close to the first battery cell to the connecting end is greater than a distance between the second battery cell and the first battery cell.

8. A back contact battery assembly according to claim 6, It is characterized in that In the first direction, the relative width distance from one end of the second battery cell close to the first battery cell to the connection end is: l 11 ＜L 1 ＜l 12 ， Where, L 1 is the relative width distance from one end of the second battery cell close to the first battery cell to the connection end in the first direction, l 11 is the distance between the second battery cell and the first battery cell, l 12 It is the relative width distance from one end of the second battery cell close to the first battery cell to the first welding point, the first welding point is arranged at one end of the first battery cell close to the second battery cell, and the first welding point is connected to the first welding strip.

9. A back contact battery assembly according to claim 6, It is characterized in that The first battery cell and the second battery cell are at least partially stacked on one end close to the first battery cell.

10. A back contact battery assembly according to claim 9, It is characterized in that In the first direction, the relative width distance from one end of the first battery cell close to the second battery cell to the connection end is: l 21 ＜L 2 ＜l 21 +l 22 ， Where, L 2 is the relative width distance from one end of the first battery cell close to the second battery cell to the connection end in the first direction, l 21 is the width of the stacking area of ​​the first battery cell and the second battery cell, l 22 It is the relative width distance from one end of the second battery cell close to the first battery cell to the first welding point, the first welding point is arranged at one end of the first battery cell close to the second battery cell, and the first welding point is connected to the first welding strip.

11. A back contact battery assembly according to claim 1, It is characterized in that The battery assembly includes at least one series-connected battery string group, each of the series-connected battery string groups includes two battery strings arranged along the second direction and connected in series with each other, Furthermore, in the same series-connected battery string group, the same first bus bar extends from the second battery cell in one battery string to the second battery cell in another battery string.

12. A back contact battery assembly according to claim 1, It is characterized in that A fourth battery cell is disposed at one end of each battery string away from the first battery cell, and a third battery cell is disposed at one end of the fourth battery cell close to the first battery cell. The battery assembly includes a parallel battery string group, each of the parallel battery string groups includes at least two battery strings arranged along a first direction and arranged in parallel with each other, and the fourth battery cells in the two battery strings arranged in parallel with each other are arranged adjacent to each other in the first direction, The battery assembly also includes: A second insulating strip is provided at an edge of the third battery cell in one of the battery strings, and the second insulating strip is provided at an end of the third battery cell close to the fourth battery cell, an intermediate bus bar, used for connecting two battery strings arranged adjacent to each other in a first direction in parallel, the intermediate bus bar being arranged on a side of the second insulating strip facing away from the third battery cell, The second insulating strip and the middle bus bar are both extended along the second direction. The second welding strip is used to electrically connect the middle bus bar, the fourth battery cell in the battery string, and the fourth battery cell in another battery string adjacent to the battery string in the first direction.

13. A back contact battery assembly according to claim 12, It is characterized in that An extension section is provided at one end of the middle bus bar close to the fourth battery cell. The extension section extends in the first direction to the outside of the edge of the second insulating strip and is electrically connected to the second welding strip. The connection between the extension section and the second welding strip forms a joint end.

14. A back contact battery assembly, It is characterized in that include: A parallel battery string group, wherein the same parallel battery string group comprises at least two battery strings arranged in a first direction and arranged in parallel with each other, each of the battery strings comprises battery cells connected in series with each other, the battery cells comprise a third battery cell and a fourth battery cell arranged in the first direction, the fourth battery cell is arranged at an end of the battery string, and the fourth battery cells in the two battery strings arranged in parallel with each other are arranged adjacently in the first direction, A second insulating strip is provided at an edge of the third battery cell in one of the battery strings, and the second insulating strip is provided at an end of the third battery cell close to the fourth battery cell, an intermediate bus bar, used for connecting two battery strings arranged adjacent to each other in a first direction in parallel, the intermediate bus bar being arranged on a side of the second insulating strip facing away from the third battery cell, The second insulating strip and the middle bus bar are both extended along the second direction. a second welding strip, for electrically connecting the middle bus bar, the fourth battery cell in the battery string where the middle bus bar is located, and the fourth battery cell in another battery string adjacent to the battery string in the first direction, An extension section is provided at one end of the middle bus bar close to the fourth battery cell. The extension section extends in the first direction to the outside of the edge of the second insulating strip and is electrically connected to the second welding strip. The connection between the extension section and the second welding strip forms a joint end.

15. A back contact battery assembly according to claim 14, It is characterized in that The intermediate bus bar is provided with a main matrix, and in the thickness direction of the third battery sheet, the orthographic projection of the main matrix falls within the orthographic projection of the second insulating strip, The relative height distance from the joint end to the fourth battery cell is smaller than the relative height distance from the side of the main substrate facing away from the second insulating strip to the fourth battery cell.

16. A back contact battery assembly according to claim 15, It is characterized in that The main substrate and the extension section are both in the form of a long strip extending along the second direction, or, The extension section is disposed on the main substrate and is in a strip-shaped structure extending along the second direction. The extension section includes extension segments, and the extension segments are intermittently arranged along the second direction at one end of the main substrate close to the fourth battery cell.

17. A back contact battery assembly according to claim 14, It is characterized in that The second insulating strip at least partially extends outside an edge of the third battery cell close to one end of the fourth battery cell.

18. A back contact battery assembly according to claim 14, It is characterized in that In the battery string provided with the middle bus bar, in the thickness direction of the third battery sheet, the orthographic projection of the joining end at least partially overlaps with the orthographic projection of the fourth battery sheet.

19. A back contact battery assembly according to claim 18, It is characterized in that In the same battery string, the fourth battery cell and the third battery cell are arranged on the same plane, In the battery string provided with the middle bus bar, in the first direction, a relative width distance from one end of the third battery cell close to the fourth battery cell to the joining end is greater than a spacing between the third battery cell and the fourth battery cell.

20. A back contact battery assembly according to claim 18, It is characterized in that In the battery string provided with the intermediate bus bar, in the first direction, the relative width distance from one end of the third battery cell close to the fourth battery cell to the joint end is: l 31 ＜L 3 ＜l 32 ， Where, L 3 is the relative width distance from one end of the third battery cell close to the fourth battery cell to the joint end in the first direction in the battery string provided with the middle bus bar, l 31 is the distance between the third battery cell and the fourth battery cell in the battery string provided with the middle bus bar, l 32 The relative width distance from the edge of the third battery cell close to one end of the fourth battery cell to the second welding point in the battery string provided with the intermediate bus bar, the second welding point is arranged on the fourth battery cell in the battery string provided with the intermediate bus bar, and is arranged at one end of the fourth battery cell close to the third battery cell, and the second welding point is connected to the second welding strip.

21. A back contact battery assembly according to claim 18, It is characterized in that The fourth battery cell is at least partially stacked with an end of the third battery cell close to the fourth battery cell.

22. A back contact battery assembly according to claim 21, It is characterized in that In the battery string provided with the middle bus bar, in the first direction, the relative width distance from one end of the fourth battery cell close to the third battery cell to the joint end is: l 41 ＜L 4 ＜l 41 +l 42 ， Where, L 4 is the relative width distance from one end of the fourth battery cell close to the third battery cell to the joint end in the first direction in the battery string provided with the middle bus bar, l 41 is the width of the stacking area of ​​the third battery cell and the fourth battery cell in the battery string provided with the middle bus bar, l 42 In the battery string provided with the intermediate bus bar, the relative width distance from the edge of the third battery cell close to one end of the fourth battery cell to the second welding point, the second welding point is provided at one end of the fourth battery cell close to the third battery cell, and the second welding point is connected to the second welding strip.

23. A photovoltaic system, It is characterized in that Comprising a back contact battery assembly according to any one of claims 1 to 22.

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