Battery string detection method

Abstract

Embodiments of the present application relate to the field of photovoltaic cells, and provide a method for detecting a battery string, including: providing a battery string to be detected, the battery string including a plurality of solar cells, a plurality of solder joints being provided on the solar cells, and adjacent solar cells being electrically connected; acquiring an electroluminescence image and an appearance image of the battery string; performing image processing on the electroluminescence image to obtain a target solar cell, the target solar cell being a solar cell having a target solder joint, and the target solder joint being a solder joint determined to be a loose solder joint with a solder ribbon based on the electroluminescence image; acquiring a target appearance image corresponding to the target solar cell from the appearance image; acquiring a magnified image of the target solder joint based on the target appearance image; and judging the welding condition of the target solder joint based on the magnified image, so as to improve the efficiency and accuracy of detecting loose solder joints in the battery string.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of photovoltaic cells, and in particular to a method for detecting a battery string. Background Art

[0002] Various defects may occur in the complicated production process of solar cells, seriously affecting the photoelectric conversion efficiency and service life of solar cells. For example, solar cell wafers are mainly connected in series through solder tapes to the solder joints on the wafers to form a battery string, and the solder tapes are used to lead the photo-generated current of each solar cell in the battery string to the outside of the solar cell wafer to achieve the conversion of light energy into electrical energy. However, due to the narrow welding window, the problem of false soldering is likely to occur.

[0003] The defect detection method of solar cells is mainly based on infrared image detection, such as electroluminescence (EL for short). With the development of battery technology, the number of solar cells in the existing battery string is large, and the number of solder joints on the solar cell wafers is large, so that the dark spots in the infrared image of the battery string may cover multiple solder joints, thus making it impossible to accurately obtain the false solder joints on the battery string. In addition, the battery string can also be detected manually by observing the battery string with the naked eye and marking the abnormal points. However, the manual detection speed is slow and the inspection time is long, which cannot meet the requirements of high production volume and high speed of the current battery string components. Summary of the Invention

[0004] The embodiments of the present application provide a method for detecting a battery string to improve the detection efficiency and accuracy of false solder joints in the battery string.

[0005] According to some embodiments of the present application, on the one hand, the embodiments of the present application provide a method for detecting a battery string, including: providing a battery string to be detected, the battery string including a plurality of solar cell wafers, a plurality of solder joints being arranged on the solar cell wafers, and adjacent solar cell wafers being electrically connected; acquiring an electroluminescence image and an appearance image of the battery string; performing image processing on the electroluminescence image to obtain a target solar cell wafer, the target solar cell wafer being a solar cell wafer having a target solder joint, and the target solder joint being a solder joint determined to be falsely soldered to the solder tape based on the electroluminescence image; acquiring a target appearance image corresponding to the target solar cell wafer from the appearance image; acquiring a magnified image of the target solder joint based on the target appearance image; and judging the welding condition of the target solder joint based on the magnified image.

[0006] In some embodiments, obtaining the electroluminescence image and the appearance image of the battery string includes: establishing a coordinate system and obtaining the coordinate positions of each solar cell in the battery string in the coordinate system. Both the electroluminescence image and the appearance image include coordinate information representing the coordinate positions of each solar cell; performing image processing on the electroluminescence image to obtain a target solar cell further includes: obtaining target coordinate information of the target solar cell, where the target coordinate information represents the coordinate position of the target solar cell; obtaining a target appearance image corresponding to the target solar cell from the appearance image, including: based on the target coordinate information, obtaining the target appearance image corresponding to the target coordinate information in the appearance image.

[0007] In some embodiments, the appearance image includes a front image and a back image; after obtaining the appearance image, it further includes: decomposing the front image into a plurality of first sub-images, each first sub-image corresponding to the front of a solar cell, and each first sub-image includes the coordinate information of the solar cell; decomposing the back image into a plurality of second sub-images, each second sub-image corresponding to the back of a solar cell, and each second sub-image includes the coordinate information of the solar cell.

[0008] In some embodiments, based on the target coordinate information, obtaining the target appearance image corresponding to the target coordinate information in the appearance image includes: obtaining a first target image corresponding to the target coordinate information in the first sub-image; obtaining a second target image corresponding to the target coordinate information in the second sub-image, and the second target image and the first target image form the target appearance image.

[0009] In some embodiments, the method for obtaining the front image and the back image includes: providing a first light source to the front of the battery string; obtaining the front image along the direction directly facing the front of the battery string; providing a second light source to the back of the battery string; obtaining the back image along the direction directly facing the back of the battery string.

[0010] In some embodiments, the irradiation direction of the first light source is perpendicular to the front of the battery string, and the irradiation direction of the second light source is perpendicular to the back of the battery string.

[0011] In some embodiments, obtaining the electroluminescence image of the battery string includes: passing a forward current of 1 to 1.5 times the open-circuit current through the battery string; obtaining the electroluminescence image presented by the infrared light with a wavelength range of 1000 to 1100 nm emitted by the battery string.

[0012] In some embodiments, based on the target appearance image, obtaining an enlarged image of the target solder joint includes: obtaining the brightness value of each solder joint in the target appearance image; based on the brightness value of the solder joint, obtaining the target solder joint from the target appearance image, where the brightness value of the target solder joint is greater than a preset brightness value; obtaining an enlarged image of the target solder joint from the target appearance image.

[0013] In some embodiments, the solder joints on adjacent solar cells are electrically connected through a solder tape; based on the magnified image, judging the soldering condition of the target solder joint includes: obtaining the difference S1 between the actual area of the target solder joint and the orthographic projection area of the solder tape on the target solder joint; obtaining the exposed area S2 of the actual area of the target solder joint; if the ratio of S2 / S1 is less than or equal to a preset value, it is judged that the target solder joint has no soldering defect; if the ratio of S2 / S1 is greater than the preset value, it is judged that the target solder joint has a soldering defect.

[0014] In some embodiments, the preset value is set in the range of 0.95 to 1.

[0015] The technical solution provided by the embodiments of the present application has at least the following advantages: by combining the electroluminescence image and the appearance image of the battery string, the target solar cell that may have soldering defects in the battery string can be judged through the electroluminescence image of the solar cell, and at the same time, the position of the target solar cell on the battery string can be obtained; further, the target appearance image corresponding to the target solar cell is found by combining the appearance image at the corresponding position; then, through the target appearance image, it is judged whether each solder joint on the target solar cell has a soldering defect, so as to locate the target solder joint that may have a soldering defect on the target solar cell; finally, based on the magnified image of the target solder joint, it is judged whether the target solder joint is soldered defectively. By combining the electroluminescence image and the appearance image, the detection range of the battery string is gradually reduced, and then the position where the target solder joint is located is determined, and the soldering condition of the target solder joint is judged, improving the efficiency and accuracy of detecting soldering defects in the battery string. Description of the Drawings

[0016] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation; in order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic diagram of the steps of the battery string detection method provided by the embodiments of the present application;

[0018] Figure 2 It is a schematic diagram of the magnified image provided by the embodiments of the present application. Detailed Embodiments

[0019] As can be seen from the background art, it is difficult to efficiently and accurately obtain the soldering defects on the battery string during the battery string detection process.

[0020] The battery string can be detected by electroluminescence. During the electroluminescence detection process, a certain forward bias voltage is applied to the battery string. Electric energy causes the carriers in the battery string to recombine and emit infrared light. The areas with defects on the battery string will become strong recombination centers for minority carriers, resulting in a decrease in the number of minority carriers at the defect positions. Correspondingly, the luminous intensity of the infrared light will decrease. Therefore, an infrared camera is used to capture the electroluminescence image of the battery string, and image processing is performed on the captured image to detect the areas with virtual soldering defects in the battery string. However, since there are many solar cells in the battery string and a large number of solder joints on the same solar cell, electroluminescence detection can only detect the approximate area of the virtual solder joints and cannot accurately locate the specific virtual solder joints. Moreover, since there are solder joints on both the front and back of the solar cell, based on the mechanism of electroluminescence detection, the electroluminescence image cannot determine whether the virtual solder joint is on the front or back of the battery string. In addition, the battery string can also be detected manually by observing the battery string with the naked eye and marking the abnormal points. For example, a flexible pick or other tools are used to move the solder tape on the solder joint. If the solder tape can be moved, the solder joint is a virtual solder joint. However, manual detection is slow and the inspection time is long, which cannot meet the requirements of high production volume and high speed of current battery string components.

[0021] An embodiment of the present application provides a battery string detection method to improve the efficiency and accuracy of detecting virtual solder joints in a battery string.

[0022] The following will elaborate on the embodiments of the present application with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in the embodiments of the present application, many technical details are provided to help readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present application can still be implemented.

[0023] Figure 1 It is a schematic diagram of the steps of the battery string detection method provided by the embodiment of the present application. Figure 2 It is a schematic diagram of an enlarged image provided by the embodiment of the present application. The following will elaborate on the battery string detection method provided by this embodiment in detail as follows:

[0024] Refer to Figure 1 , the battery string detection method includes:

[0025] Step 11: Provide a battery string to be detected. The battery string includes a plurality of solar cells, and a plurality of solder joints are provided on the solar cells, and adjacent solar cells are electrically connected.

[0026] For the battery string to be detected, the battery string includes a plurality of solar cells, and the solar cells include photovoltaic solar cells. The photovoltaic solar cells can be connected in series through solder tapes to the solder joints on the photovoltaic solar cells, so as to lead the photo-generated current of each photovoltaic solar cell in the battery string to the outside of the photovoltaic solar cell, realizing the conversion of light energy into electrical energy. In some embodiments, the electrical connection between the solder joints and the solder tapes is mainly achieved through high-temperature soldering. However, for temperature-sensitive batteries such as heterojunction batteries and tandem batteries combined with crystalline silicon batteries, in order to reduce the damage to the battery itself caused by the high-temperature soldering method, low-temperature solder tapes are generally selected for soldering at a lower soldering temperature. The melting point of the low-temperature solder tape is generally lower than 165 degrees. In the process of using the low-temperature solder tape for low-temperature soldering, due to the relatively narrow soldering window, it is easy to cause the problem of poor soldering between the solder joints and the solder tapes.

[0027] Step 12, obtaining the electroluminescence image and the appearance image of the battery string.

[0028] For the electroluminescence image, in some embodiments, obtaining the electroluminescence image of the battery string includes: passing a forward current of 1 to 1.5 times the open-circuit current through the battery string; obtaining the electroluminescence image presented by the infrared light with a wavelength range of 1000 to 1100 nm emitted by the battery string. By applying a forward current of 1 to 1.5 times the open-circuit current to the battery string, the carriers in the battery string recombine to emit infrared light. The area with a poor soldering problem in the battery string will become a strong recombination center for minority carriers, resulting in a decrease in the number of minority carriers in the area with the poor soldering problem and a corresponding decrease in the emission intensity of the infrared light. Then, an infrared camera is used to capture the electroluminescence image of the battery string in the infrared wavelength range of 1000 to 1100 nm, and image processing is performed on the captured electroluminescence image, so that the area with a poor soldering defect in the battery string can be captured. However, based on the imaging mechanism of the electroluminescence image, the electroluminescence image cannot determine whether the poor solder joint is on the front or the back of the battery string.

[0029] In some embodiments, obtaining the electroluminescence image and the appearance image of the battery string includes: establishing a coordinate system, and obtaining the coordinate position of each solar cell in the battery string in the coordinate system. Both the electroluminescence image and the appearance image contain coordinate information representing the coordinate position of each solar cell. By establishing a coordinate system, each solar cell can correspond to a coordinate position in the battery string. Thus, in the process of processing the electroluminescence image, after obtaining the target solar cell that may have a poor soldering problem, the target coordinate information of the target solar cell can be quickly obtained.

[0030] For the appearance image, in some embodiments, the appearance image includes a front image and a back image. Specifically, the method for obtaining the front image and the back image includes: providing a first light source to the front of the battery string; obtaining the front image along the direction directly facing the front of the battery string; providing a second light source to the back of the battery string; obtaining the back image along the direction directly facing the back of the battery string.

[0031] It can be understood that both the front and back of the battery string have multiple solder joints. The solder joints on the front or back of the battery cells can be electrically connected to adjacent battery cells through solder tapes. Correspondingly, the appearance image of the battery string includes a front image and a back image. The solder joints are generally white silver paste, and the solder joints undergo diffuse reflection under light, and the solder joints presented by the camera are white; the solder tapes are generally tinned copper tapes with a tin-lead alloy on the surface, and the cross-section of the solder tape is usually cylindrical. Under light, most of the light is reflected by the surface of the solder tape to the surface of the battery string, and the color of the solder tape presented by the camera is darker (i.e., the brightness value of the solder tape is less than that of the solder joint); when the solder tape is welded to the solder joint, there will be solder accumulation near the solder tape, resulting in a darker area with a diameter larger than that of the solder tape on the solder joint (i.e., the brightness value at the solder accumulation is less than that of the solder joint). Therefore, by the brightness values of each solder joint presented in the appearance image of the battery string, it is possible to judge the solder joints on the battery cells where there may be a problem of poor soldering; under the illumination of the light source, obtaining the appearance image along the direction directly facing the front or back of the battery string can obtain the appearance images of all the solder joints in the battery string at the same angle, avoiding errors in judgment caused by differences in the brightness of the solder joints and solder tapes due to different acquisition angles.

[0032] Further, in some embodiments, the irradiation direction of the first light source is perpendicular to the front of the battery string, and the irradiation direction of the second light source is perpendicular to the back of the battery string. When the irradiation direction of the first light source is perpendicular to the front of the battery string, the incident light and the reflected light on the front of the battery string are both perpendicular to the front of the battery string, and all the solder joints on the front of the battery string are under the same illumination conditions, which can avoid the influence of different illumination conditions on the accuracy of the front image; when the irradiation direction of the second light source is perpendicular to the back of the battery string, the incident light and the reflected light on the back of the battery string are both perpendicular to the back of the battery string, and all the solder joints on the back of the battery string are under the same illumination conditions, which can avoid the influence of different illumination conditions on the accuracy of the back image.

[0033] In some embodiments, the appearance image includes a front image and a back image; after obtaining the appearance image, it further includes: decomposing the front image into multiple first sub-images, each first sub-image corresponding to the front of a battery cell, and each first sub-image including the coordinate information of the battery cell; decomposing the back image into multiple second sub-images, each second sub-image corresponding to the back of a battery cell, and each second sub-image including the coordinate information of the battery cell.

[0034] It can be understood that after obtaining the appearance image, the front image is decomposed into multiple first sub-images corresponding to the front of the battery cells, and each first sub-image includes the coordinate information of the corresponding battery cell. The back image is decomposed into multiple second sub-images corresponding to the back of the battery cells, and each second sub-image includes the coordinate information of the corresponding battery cell. After performing image processing on the electroluminescence image to obtain the target battery cell, based on the coordinate information of the target battery cell, the corresponding first sub-image and second sub-image can be directly extracted, thereby improving the efficiency of obtaining the target appearance image.

[0035] Step 13: Perform image processing on the electroluminescence image to obtain the target battery cell. The target battery cell is a battery cell with a target solder joint, and the target solder joint is a solder joint determined to be poorly soldered with the bus bar based on the electroluminescence image.

[0036] Based on the imaging mechanism of the above-mentioned electroluminescence image, it can be known that after performing image processing on the electroluminescence image, the area with poor soldering defects in the battery string can be obtained, and the corresponding target battery cell can be obtained through the position corresponding to the area with poor soldering defects.

[0037] In some embodiments, performing image processing on the electroluminescence image to obtain the target battery cell further includes: obtaining the target coordinate information of the target battery cell, where the target coordinate information represents the coordinate position of the target battery cell. By establishing a coordinate system, each battery cell can correspond to a coordinate position in the battery string. Thus, during the processing of the electroluminescence image, after obtaining the target battery cell that may have a poor soldering problem, the target coordinate information of the target battery cell can be quickly obtained, and through the coordinate information, the target appearance image corresponding to the target battery cell in the appearance image can be more quickly corresponded to.

[0038] Step 14: Obtain the target appearance image corresponding to the target battery cell from the appearance image.

[0039] In some embodiments, obtaining the target appearance image corresponding to the target battery cell from the appearance image includes: obtaining the target appearance image corresponding to the target coordinate information in the appearance image based on the target coordinate information. It can be understood that after establishing the coordinate system, each battery cell corresponds to coordinate information, and in the target appearance image, the appearance image can be directly magnified based on the coordinate information to display the target appearance image corresponding to the target battery cell.

[0040] In some embodiments, based on the target coordinate information, obtaining a target appearance image corresponding to the target coordinate information in the appearance image includes: obtaining a first target image corresponding to the target coordinate information in the first sub-image; obtaining a second target image corresponding to the target coordinate information in the second sub-image, and the second target image and the first target image form the target appearance image. It can be understood that after establishing a coordinate system and decomposing the front image and the back image, each solar cell corresponds to coordinate information and a first sub-image and a second sub-image corresponding to the coordinate information. Based on the coordinate information of the target solar cell, the first sub-image and the second sub-image corresponding to the target coordinate information in the appearance image can be quickly locked, further improving the efficiency of obtaining the target appearance image.

[0041] Step 15: Based on the target appearance image, obtain a magnified image of the target solder joint.

[0042] Specifically, in some embodiments, the solder joints on adjacent solar cells are electrically connected through a solder strip; based on the target appearance image, obtaining a magnified image of the target solder joint includes: obtaining the brightness value of each solder joint in the target appearance image; based on the brightness value of the solder joint, obtaining the target solder joint from the target appearance image, and the brightness value of the target solder joint is greater than a preset brightness value; obtaining a magnified image of the target solder joint from the target appearance image. From the above, it can be seen that based on the appearance image of the battery string, the solder joints on the solar cells that may have a soldering problem can be judged. The brightness value of the solder joint is greater than the brightness value of the solder strip and the brightness value of the solder accumulation area. When the solder joint is welded to the solder strip, solder will accumulate on the surface of the solder joint near the solder strip, and the brightness value of the corresponding solder joint will decrease. Therefore, by comparing the brightness value of the solder joint with the preset brightness value, the target solder joints that may have a soldering problem can be obtained. The preset brightness value can be 90% - 100% of the brightness value when there is no solder accumulation on the surface of the solder joint, for example, it can be 90%, 93%, 95%, 98% or 100%.

[0043] Step 16: Based on the magnified image, judge the soldering condition of the target solder joint.

[0044] Specifically, refer to Figure 2 In some embodiments, based on the magnified image 101, judging the soldering condition of the target solder joint 102 includes: referring to Figure 2 (a), obtaining the difference S1 between the actual area of the target solder joint 102 and the orthographic projection area of the solder strip 103 on the target solder joint 102; referring to Figure 2(b), obtain the exposed area S2 of the actual area of the target solder joint 102; if the ratio of S2 / S1 is less than or equal to the preset value, it is determined that the target solder joint 102 has no soldering defect; if the ratio of S2 / S1 is greater than the preset value, it is determined that the target solder joint 102 has a soldering defect. It can be understood that whether the solder 104 accumulates on the surface of the target solder joint 102 can be judged by the brightness value. Since the surface of the target solder joint 102 is covered with a solder tape 103, the difference S1 between the actual area of the target solder joint 102 and the orthographic projection area of the solder tape 103 on the target solder joint 102 is the area exposed when the target solder joint 102 is not soldered to the solder tape 103, and the exposed area S2 of the actual area of the target solder joint 102 is the area where no solder 104 accumulates after the welding process of the target solder joint 102; through the ratio of S2 / S1, the degree of solder 104 accumulation can be judged, and accordingly, the soldering condition of the target solder joint 102 can be reflected.

[0045] Further, in some embodiments, the preset value is set in the range of 0.95 to 1. For example, 0.95, 0.96, 0.98, 1. When the preset value is equal to 1, that is, the exposed area when the target solder joint 102 is not soldered to the solder tape 103 is equal to the area where no solder 104 accumulates after the welding process of the target solder joint 102, which means that the target solder joint 102 is not soldered to the solder tape 103; when the preset value is less than 1, that is, the area where no solder 104 accumulates after the welding process of the target solder joint 102 is less than the exposed area when the target solder joint 102 is not soldered to the solder tape 103, which means that there is solder 104 accumulated on the surface of the target solder joint 102. However, due to the tin layer flow of the solder tape 103 or the uneven tin layer of the solder tape 103 itself after welding, the ratio of S2 / S1 needs to be at least less than 0.95 to determine that the solder joint 102 and the solder tape 103 are effectively soldered.

[0046] The battery string detection method provided by the embodiments of the present application combines the electroluminescence image and the appearance image of the battery string. Through the electroluminescence image of the battery cell, the target battery cell in the battery string that may have soldering defects can be judged, and at the same time, the position of the target battery cell on the battery string can be obtained; further, the target appearance image corresponding to the target battery cell can be found by combining the appearance image at the corresponding position; then, through the target appearance image, it can be judged whether each solder joint on the target battery cell has a soldering defect, so as to locate the target solder joint on the target battery cell that may have a soldering defect; finally, based on the magnified image of the target solder joint, it can be judged whether the target solder joint is soldered defectively. Through the method of combining the electroluminescence image and the appearance image, the detection range of the battery string is gradually narrowed, and then the position where the target solder joint is located is determined, and the soldering condition of the target solder joint is judged, improving the efficiency and accuracy of detecting soldering defects in the battery string.

[0047] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present application, and in actual applications, various changes can be made to them in form and details without departing from the spirit and scope of the present application.

Claims

1. A method for detecting a battery string, characterized in that, Including: Providing a battery string to be detected, the battery string includes a plurality of battery cells, a plurality of solder joints are arranged on the battery cells, and adjacent battery cells are electrically connected; Obtaining an electroluminescence image and an appearance image of the battery string, establishing a coordinate system, and obtaining the coordinate position of each battery cell in the battery string in the coordinate system, and both the electroluminescence image and the appearance image include coordinate information characterizing the coordinate position of each battery cell; The appearance image includes a front image and a back image; after obtaining the appearance image, it further includes: decomposing the front image into a plurality of first sub-images, each first sub-image corresponding to the front of a battery cell, and each first sub-image includes the coordinate information of the battery cell; decomposing the back image into a plurality of second sub-images, each second sub-image corresponding to the back of a battery cell, and each second sub-image includes the coordinate information of the battery cell; performing image processing on the electroluminescence image to obtain a target battery cell, the target battery cell being the battery cell with a target solder joint, the target solder joint being the solder joint determined to be poorly soldered to the solder strip based on the electroluminescence image, and obtaining the target coordinate information of the target battery cell, the target coordinate information characterizing the coordinate position of the target battery cell; Obtaining a target appearance image corresponding to the target battery cell from the appearance image, and obtaining the target appearance image corresponding to the target coordinate information in the appearance image based on the target coordinate information; Obtaining a magnified image of the target solder joint based on the target appearance image; Judging the soldering condition of the target solder joint based on the magnified image.

2. The detection method of the battery string according to claim 1, wherein, The obtaining the target appearance image corresponding to the target coordinate information in the appearance image based on the target coordinate information includes: Obtaining a first target image corresponding to the target coordinate information in the first sub-image; Obtaining a second target image corresponding to the target coordinate information in the second sub-image, and the second target image and the first target image constitute the target appearance image.

3. The detection method of the battery string according to claim 1, characterized in that, The method for obtaining the front image and the back image includes: Providing a first light source to the front of the battery string; Obtaining the front image along the direction directly facing the front of the battery string; Providing a second light source to the back of the battery string; Obtaining the back image along the direction directly facing the back of the battery string.

4. The detection method of the battery string according to claim 3, characterized in that, The irradiation direction of the first light source is perpendicular to the front of the battery string, and the irradiation direction of the second light source is perpendicular to the back of the battery string.

5. The detection method of the battery string according to claim 1, characterized in that, Obtaining the electroluminescence image of the battery string includes: Applying a forward current of 1 to 1.5 times the open-circuit current to the battery string; Obtaining the electroluminescence image presented by the infrared light with a wavelength range of 1000 to 1100 nm emitted by the battery string.

6. The detection method of the battery string according to claim 1, wherein, Obtaining a magnified image of the target solder joint based on the target appearance image includes: Obtaining the brightness value of each solder joint in the target appearance image; Based on the brightness value of the solder joint, obtain the target solder joint from the target appearance image, where the brightness value of the target solder joint is greater than the preset brightness value; Obtain the magnified image of the target solder joint from the target appearance image.

7. The detection method of the battery string according to claim 1, characterized in that The solder joints on adjacent cell wafers are electrically connected through a solder strip; Based on the magnified image, judge the soldering condition of the target solder joint, including: Obtain the difference S1 between the actual area of the target solder joint and the orthographic projection area of the solder strip on the target solder joint; Obtain the exposed area S2 of the actual area of the target solder joint; If the ratio of S2 / S1 is less than or equal to the preset value, it is judged that the target solder joint has no soldering defect; If the ratio of S2 / S1 is greater than the preset value, it is judged that the target solder joint has a soldering defect.

8. The detection method of the battery string according to claim 7, wherein, The setting range of the preset value is 0.95 - 1.

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