Process Introduction: Here we will only briefly introduce the function of the process to give you a basic understanding.
1. Battery Testing: Due to the randomness of solar cell manufacturing conditions, the performance of produced cells varies. Therefore, to effectively combine cells with similar or identical performance, they should be classified according to their performance parameters. Battery testing involves classifying cells by measuring their output parameters (current and voltage). This improves cell utilization and produces high-quality battery modules. Including one or several low-power cells in a single solar cell will reduce the overall module's output power. Therefore, to minimize losses from series and parallel connections, cells with similar performance must be combined into modules.
2. Welding typically involves connecting 6-12 photovoltaic cells in series to form a photovoltaic string. Traditionally, silver flat wires were used to form the cell connectors, which were then connected using spot welding or welding (using infrared lamps to utilize the thermal effect of infrared radiation). Currently, copper flat wires plated with 60% Sn, 38% Pb, and 2% AG (approximately 100-200 μm thick) are commonly used. The connectors require treatment with flame, infrared radiation, hot air, and laser. Due to the toxicity of lead, an alloy of 96.5% copper and 3.5% silver is increasingly being used. However, when welding with this alloy, the welding temperature and time must not be too high, otherwise it will lead to the growth of weld crystals, reduced strength, or cell breakage. The welded joints should have a good fit and appropriate gap, and the joints should be smooth, flat, and strong. The series-connected cells should have uniform spacing and consistent color.
3. Rear-side stringing involves connecting 36 cells together to form a module string. Currently, the process is generally manual. The cells are positioned using a template with 36 grooves for placing the cells. The size of the grooves corresponds to the size of the cells, and the positions of the grooves are pre-designed. Different templates are used for different module sizes. The operator uses a soldering iron and solder wire to solder the front electrode (negative terminal) of the "front cell" to the back electrode (positive terminal) of the "rear cell." This process is repeated to connect the 36 cells together, and leads are soldered to the positive and negative terminals of the module string.
4. After the back-side connections are completed and inspected, the module strings, glass, and cut EVA, fiberglass, and backsheet are laid out in layers according to a specific plan, ready for lamination. A reagent is applied to the glass beforehand to increase the adhesion strength between the glass and EVA. During installation, ensure the relative positions of the battery strings and other materials such as glass, and adjust the distance between the batteries to lay a good foundation for lamination. Laying layers: from bottom to top: glass, EVA, battery, EVA, fiberglass, backsheet.
5. Module Lamination: The laid-out cells are placed in a laminator. Air is removed from the module through vacuuming, and then the EVA is heated to melt, bonding the cells, glass, and backsheet together. Finally, the module is cooled and removed. The lamination process is a crucial step in module production; the lamination temperature and time are determined by the properties of the EVA. When using fast-curing EVA, the lamination cycle time is approximately 25 minutes. The curing temperature is 150℃. The laminated module should have no broken, cracked, or significantly displaced individual cells. There should be no air bubbles or delamination channels in the EVA at the module edges and between any parts of the circuitry, and the EVA should have good cross-linking.
6. During the trimming and lamination process, the EVA melts and solidifies outwards due to pressure, forming burrs. Therefore, these burrs should be removed after lamination is completed.
7. Framing: The laminated battery modules are framed, similar to framing glass, to increase module strength, further seal the battery modules, and extend battery life. Gaps between the frame and the glass module are filled with silicone resin. The frame is made of stainless steel or plastic. A module consists of the frame and a junction box. For every 1 square meter of module produced, the energy consumption of the aluminum alloy frame increases by 215 kWh. To reduce costs, frameless photovoltaic modules are becoming increasingly common. Modules are typically fixed to the support structure using clamping bolts, and sometimes adhesive. The use of frameless modules significantly reduces energy demand and carbon dioxide emissions.
9. Soldering a junction box: Solder a box to the lead wires on the back of the component to facilitate the connection of the battery to other devices or batteries.
10. High-voltage testing refers to applying a certain voltage between the component frame and the electrode leads to test the component's withstand voltage and insulation strength, in order to ensure that the component is not damaged under harsh natural conditions (such as lightning strikes).
11. Component Testing: The purpose of this test is to calibrate the output power of the battery, test its output characteristics, and determine the quality grade of the component. The international IEC standard test conditions are AM1.5, 100 mW/m², and 25℃. The following parameters must be tested and listed: open-circuit voltage, short-circuit current, operating voltage, operating current, maximum output power, fill factor, photoelectric conversion efficiency, series resistance, parallel resistance, and IU curve, etc.
12. After labeling the photovoltaic modules according to the test results, they can be stored in the warehouse for sale.
