(1) Introduction to the structure of cylindrical battery cell module.
In the design of cylindrical battery cell modules, there are various module structures, which are mainly determined according to the needs of customers and models, which ultimately leads to different manufacturing processes of the modules. The module is generally composed of battery cores, upper and lower brackets, bus bars (some are also called connecting pieces), sampling wiring harness, insulation board and other main components. The common process flow of the module shown in Figure 9-9 is introduced.
(2) Introduction to the assembly process flow of cylindrical battery cell module
- Cell sorting.
When designing the module process, it is necessary to consider the consistency of the electrical performance of the module to ensure that the overall performance of the Pack meets or meets the requirements of the vehicle. In order to ensure the consistency of the electrical performance of the modules, strict requirements must be imposed on the incoming materials of the batteries. The cell manufacturers generally group the cells according to their voltage, internal resistance and capacity specifications before shipment, but the final requirements of the cell manufacturers and the pack manufacturers are different, taking into account the manufacturing process, cost, cell performance, etc. Factors, Pack manufacturers generally re-sort the cells according to their own standards.
Cell sorting needs to consider the issue of sorting standards. A reasonable standard will reduce the remaining idle cells, improve production efficiency, and reduce production costs. In the actual production process, it is also necessary to check the appearance of the battery core, such as checking whether the battery core has defective products such as insulation film damage, insulation film warping, battery leakage, and positive and negative end surface stains.
- Insert the battery into the lower bracket.
Inserting the battery core into the lower bracket refers to inserting the battery core into the battery positioning hole of the lower bracket. The difficulty lies in the matching tolerance between the battery core and the lower bracket hole. If the hole is too large, it is convenient for the battery core to be inserted, but the battery core is not fixed well, which affects the welding effect; if the hole is too small, it is more difficult for the battery core to be inserted into the lower bracket positioning hole. In serious cases, the battery core cannot be inserted, which affects production efficiency. In order to facilitate the insertion of the battery core and fix the battery core, the front end of the lower bracket hole can be opened into a bell mouth (Figure 9-10). When assembling, it is necessary to prevent the polarity of the battery cell from being reversed. If it is assembled manually, the battery polarity needs to be quickly checked to prevent defective products from flowing into the subsequent process.
- Judgment of cell polarity.
Cell polarity judgment refers to checking whether the polarity of the cell meets the requirements of the document, which is a safety inspection. If there is no polarity check and the polarity of the battery core is reversed, the module will short-circuit when the busbar on the second side is installed, resulting in damage to the product and serious personal injury. Note that it is necessary to check that the equipment is in good working condition before the start of each shift, otherwise it needs to be shut down for maintenance.
- Cover the bracket.
Covering the bracket means to cover the upper bracket on the cell and fix the cell in the bracket. In general, it is more difficult to cover the bracket than the battery cell to enter the lower bracket. One is related to the production process of the cylindrical battery. There is a rolling groove process in the process. If the control is not good, it will lead to poor consistency of the battery size and affect If the bracket is covered, it will not be able to be covered in serious cases; secondly, the battery core is not fixed well with the lower bracket, which causes the battery cell to have a certain skew, which in turn causes the upper bracket to be difficult to cover or not to be covered.
- Module spacing detection
Module spacing detection refers to the detection of the distance between the end face of the cell pole and the surface of the bracket. The purpose is to check the fit between the end face of the cell pole and the bracket. It is used to determine whether the cell is fixed in place, and to make advance judgments for whether the welding conditions are met. .
Plasma cleaning is a kind of dry cleaning, which mainly relies on the “activation” of active ions in the plasma to remove surface contamination. This method can effectively remove dirt, dust, etc. on the end face of the cell pole, and prepare for resistance welding in advance to reduce welding defects.
- The busbar installation.
The bus bar installation refers to the installation and fixation of the bus bar to the module for resistance spot welding. When designing, it is necessary to consider the position accuracy of the bus bar and the cell, especially the problem of positioning reference. The purpose is to make the bus bar position in the center of the pole surface of the cell, which is convenient for welding. When designing the upper and lower brackets, consider the isolation of the busbars: if the isolation design is not good, you need to consider the use of anti-short-circuit tooling in the process design to avoid short-circuits under abnormal conditions.
- Resistance connection.
Resistance welding refers to welding the bus bar and the pole surface of the cell by means of resistance welding. At present, resistance spot welding is generally used in China. When designing the resistance spot welding process, the following four points need to be considered:
①The material, structure and thickness of the busbar;
②The material, shape, front diameter and frequency of repairing the electrode (also called soldering pin);
③Optimization of process parameters, such as welding current, welding voltage, welding time, applied pressure, etc.;
④ Cleanliness and flatness of the welding surface.
In actual production, there are many failure factors, which require technical personnel to analyze and deal with the actual situation.
- Welding inspection.
During the resistance welding process, the equipment generally monitors the welding parameters. If abnormal parameters are detected, the equipment will automatically alarm. As there are many factors that affect welding quality, only parameter monitoring is used to judge welding failure. The current results are not particularly satisfactory. In the actual production control, the welding effect is generally checked and confirmed again by manually inspecting the appearance and manually selecting the buss.
Glue generally has two uses in the application of modules: one use is to fix the battery core, which mainly emphasizes the performance indicators of the adhesive force, shear strength, aging resistance, and life span of the glue; the other use is to connect the battery core and the module The heat is transferred out through the thermal conductive glue, which mainly emphasizes the thermal conductivity, aging resistance, electrical insulation, flame retardancy and other performance indicators of the glue. Due to the different uses of glue, the properties and formulas of glue are also different, so the methods and equipment for realizing the glueing process are different. In terms of glue selection and gluing process, the following three points need to be considered:
①The safety and environmental protection performance of glue: try to choose non-toxic and odorless glue, which can not only protect the operator, but also protect the user, but also better protect the environment. This is the goal of new energy development.
② Surface drying time of glue: In order to improve production efficiency, it is generally hoped that the surface drying time of glue is as short as possible.
In the actual production process, if the glue meter drying time is too short, factors such as material waiting and equipment abnormality will lead to a large amount of glue waste; it may also be that the operator does not handle it in time, causing the equipment to block due to the short glue meter drying time. According to experience, it is reasonable to control the surface drying time to 15-30min as much as possible.
③The amount of glue: The amount of glue is mainly determined by the product and process, and the purpose is to meet the requirements of the product. At present, the commonly used gluing processes are glue, gluing, spraying and potting, and the equipment required for each process is also different. It is necessary to pay attention to the control of the amount of glue when making glue to avoid overflowing glue and affecting other processes.
- Cover the insulation board.
Cover insulation board means to insulate and protect the busbars of the module. When designing the process, it is necessary to pay attention that the insulating board cannot be higher than the upper edge of the support, and the gap between the insulating board and the frame of the support is preferably less than 1mm.
- Module EOL test.
EOL (end of line) testing (generally called offline testing) is a key part of quality control in the production process. It mainly tests the special characteristics of modules. The main test items are:
①Insulation withstand voltage test;
②Internal resistance test;
③Voltage sampling test;
④Size inspection; ⑤Appearance inspection.
Test items are generally increased or decreased according to the requirements of customers and products, among which safety test items are indispensable.
- Transfer to Pack assembly or storage.
After EOL, the tested modules are transferred to the Pack assembly process or warehoused according to the regulations. During the transfer process, the modules need to be insulated and protected to prevent the modules from falling.
Through the introduction of the production process of the cylindrical battery cell module, the design of the process is different for different customers and products, and the purpose is to quickly respond to the needs of customers and the market. When designing the module process flow, generally the following points need to be considered:
①Safety: product safety and safe production;
②Electrical performance: the consistency of capacity, voltage, internal resistance and performance;
③Production beat: the higher the beat, the greater the production capacity;
④Dimensions: external dimensions and fixed dimensions;
⑤ Process route: refers to the selection and determination of key processes;
⑥ Cost: factors that need to be considered in both product design and process design.
Through the above analysis, it is not enough to design the module process flow well. It also needs a complete production system to support it in order to manufacture products that satisfy customers.