I. Battery test
Due to the random nature of cell fabrication conditions, the performance of the cells produced varies. Therefore, in order to effectively combine batteries with the same or similar performance. They should be classified according to their performance parameters. Battery testing means classifying batteries by testing the magnitude of their output parameters (current and voltage). In order to improve the utilization of batteries and make battery components of acceptable quality.
2. Front side welding
Front side soldering is to solder the sink strip to the main grid line on the front side (negative) of the battery. The sink strip is a tinned copper strip, and the soldering machine used can spot weld the strip to the main grid line in the form of multiple points. The heat source for welding is an infrared lamp, which uses the infrared heat effect for welding. The length of the pv ribbon is about twice the length of the battery side. And the extra tape is connected to the electrode on the back of the battery cell when welding on the back side.
3. Back side string connection
Back-side stringing is the process of connecting cells together in series to form a component string. The cells are positioned mainly by a mold plate with recesses for placing the cells, the size of the slots corresponds to the size of the cells, the position of the slots has been designed and different templates are used for different sizes of components.
4. Laminated laying
After the backside is strung and inspected and qualified, the strung cells, glass and cut EVA, glass fiber, and backsheet are laid in accordance with certain levels and prepared for lamination. The glass is pre-coated with a layer of reagent to increase the bonding strength of the glass and EVA.
5. Component lamination
Put the laid cell into the laminator and extract the air from the module by vacuuming. The EVA is then heated to melt and bond the cell, glass and backsheet together; finally, the assembly is cooled and removed. The lamination process is a key step in the production of components. The lamination temperature and lamination time are determined by the nature of EVA. Currently, the main use of fast-curing EVA, lamination cycle time of about 25 minutes, curing temperature of 150 ℃.
6. Trimming
When laminating EVA melted due to pressure and outward extension of the curing formation of burrs. So the lamination should be removed.
7. Framing
Similar to fitting a glass with a mirror frame, an aluminum frame is fitted to the glass assembly to increase the strength of the assembly, further sealing the battery components and extending the life of the battery. The gap between the frame and the glass module is filled with polysiloxane resin. And each frame is connected with corner bonds.
8. Welded junction box
A box is welded to the back leads of the module to facilitate the connection between the cell and other devices or cells. Solar junction box provides users with a combined connection solution for solar panels. It is a connector between the solar cell square formed by solar cell modules and the solar charging control device. And is a cross-disciplinary and comprehensive design that combines electrical design, mechanical design and material science, and is an important component of solar modules.
The construction of the junction box: general solar junction box includes the upper cover and the lower box. The upper cover and the lower box are connected through the shaft, its characteristic lies in: in the lower box there are several wiring blocks arranged in parallel, each adjacent two wiring blocks connected by one or more diodes between. The upper cover or lower box is made of thermally conductive material, and its product types are now: glued junction box, screen wall junction box, panel junction box, etc.
9. Component Testing
The purpose of the test is to calibrate the output power of the cell, test its output characteristics and determine the quality level of the module. Solar cell module parameters measurement should include insulation resistance, insulation strength, operating temperature, reflectivity and thermo-mechanical stress, in addition to some parameters commonly used and the same as those of a single solar cell.
Insulation resistance measurement is to measure the insulation resistance between the module output and the metal substrate or frame. Before measurement, do a safety check, for the square array that has been installed and used should first check the potential to ground, electrostatic effect, and whether the metal basic, frame, bracket and other grounding is good, etc.
Insulation resistance measurement
Can use ordinary megohmmeter to measure the insulation resistance, but choose a megohmmeter with a voltage level roughly equivalent to the circuit open circuit voltage of the square array to be measured. When measuring the insulation resistance, the relative humidity of the atmosphere should be no more than 75%. Dielectric strength is the insulation itself to withstand voltage capacity.
The voltage acting on the insulation exceeds a certain critical value, the insulation will be lost and lose the insulation role. Usually, the insulation strength of power equipment is expressed by breakdown voltage; while the insulation strength of insulation materials is expressed by the average breakdown electric field strength, referred to as breakdown field strength. Breakdown field strength is the voltage at which breakdown occurs divided by the distance between the two electrodes to which the voltage is applied under the specified experimental conditions.
Indoor testing and outdoor testing
In the case of both indoor and outdoor testing, the requirements for the shape, size. And dimensions of the reference component are not the same. In the case of indoor testing, the structure, material, shape, and size of the reference component are required to be the same as the component to be tested as much as possible.
In the case of outdoor sunlight testing, the above requirements can be slightly relaxed, i.e., reference components of smaller size and not exactly the same shape can be used. In module parameter measurement. It is better to use reference module to calibrate irradiance than to use standard solar cell to calibrate irradiance directly.
Ground-mounted solar modules operate in outdoor environments for years and years. And must repeatedly withstand various harsh climatic conditions and other variable environmental conditions. And must ensure that their electrical performance does not deteriorate significantly over a long rated life (usually more than 15 years is required).
Before and after each project are required to observe and check the appearance of the components for abnormalities, whether the maximum output power drop is greater than 5%, where the appearance of abnormalities or the maximum output power drop greater than 5% are unqualified, which is a common requirement of the test.
High Voltage Testing
High voltage test is to apply a certain voltage between the module frame and electrode leads to test the voltage resistance and insulation strength of the module to ensure that the module will not be damaged under severe natural conditions (such as lightning strikes, etc.).
Vibration and shock testing: The purpose of the vibration and shock test is to assess its ability to withstand transportation. The vibration time is 20 minutes in normal direction and 20 minutes in tangential direction. And the number of shocks is 3 times each in normal direction and tangential direction.
Hail test: Solar cell modules used in offshore environments should be subjected to this test. After 96 hours of storage in the mist of 5% sodium chloride aqueous solution, the appearance, maximum output power and insulation resistance are checked. More stringent tests include ground solar irradiation test, twist and bend test, constant humidity and heat storage. The low temperature storage and temperature alternation test, etc.
