Technical requirements for battery modules
Qualified battery modules should meet certain technical requirements, and relevant departments have formulated national and industry standards for battery modules. The following are some basic technical requirements for laminated encapsulated crystalline silicon battery modules.
(1) The battery module should be used for more than 25 years under the specified working environment.
(2) The power attenuation of the module shall not be less than 80% of the original power during the 25-year life span.
(3) The color of the upper surface of the battery of the module should be uniform, without mechanical damage, and no oxidation spots on the surface of the solder joints and interconnecting strips.
(4) Each battery and interconnection bar of the module should be neatly arranged, and the frame of the module should be clean and free of corrosion spots.
(5) No bubbles or delamination are allowed in the package layer of the module to form a path between a cell and the edge of the module. The geometric size and number of bubbles or delamination should comply with the corresponding product detailed specifications.
(6) The area specific power of the module is greater than 65W/m2, the mass specific power is greater than 4.5Wkg, and the fill factor FF is greater than 0.65.
(7) The insulation resistance of the modules under normal conditions shall not be less than 200MΩ.
(8) The cross-linking degree of module EVA should be greater than 65%, the peel strength between EVA and glass is greater than 30N/cm, and the peel strength between EVA and module backplane material is greater than 15N/cm.
(9) Each module must have a label including the following content.
①Product name and model;
②Main performance parameters: including short-circuit current ISC, open-circuit voltage UOC, peak operating current Im, peak operating voltage Um, peak power Pm and I-U curve, module weight, test conditions, precautions for use, etc.;
③Name of manufacturer, date of production, brand trademark, etc.
Inspection and testing of battery modules
The various performance tests of battery modules are generally carried out in accordance with the requirements and methods in GBT9535-1998 “Design Appraisal and Finalization of Crystalline Silicon Photovoltaic Modules for Ground Use”. The following are some basic performance indicators and testing methods of battery modules.
(1) Electrical performance test
Under the specified standard test conditions (AM: 1.5; light intensity irradiance 1000w/m2; ambient temperature 25℃), measure the open circuit voltage, short circuit current, peak output power, peak voltage, peak current and volt-ampere characteristic curve of the battery module.
(2) Electrical insulation performance test
Measure the insulation resistance through the module frame and the module lead-out line with a 1kV DC voltage. The insulation resistance must be greater than 200MΩ to ensure that there is no leakage of the module frame during the application process.
(3) Thermal cycle experiment
Place the module in a climate room with automatic temperature control and internal air circulation, and make the module circulate at 40~85℃ for a specified number of times, and keep it for a specified time under extreme temperature, and monitor possible short circuits and open circuits, appearance defects, electrical performance attenuation rate, insulation resistance, etc. that may occur during the experiment to determine the thermal strain capacity of modules related to repeated temperature changes.
(4) Damp heat-damp cold experiment
Place the modules in a climate room with automatic temperature control and internal air circulation, so that the modules will reciprocate under certain temperature and humidity conditions and maintain a certain recovery time, and monitor possible short circuits and open circuits, appearance defects, electrical performance degradation rate, insulation resistance, etc. that may occur during the experiment to determine the ability of the modules to withstand high temperature, high humidity, and low temperature and low humidity.
(5) Mechanical load test
Gradually load the module surface to monitor possible short circuits and open circuits, appearance defects, electrical performance attenuation rate, insulation resistance, etc. during the experiment to determine the module’s ability to withstand static loads such as wind, snow, hail, etc.
(6) Hail experiment
Use steel balls instead of hail to hit the modules from different angles with a certain momentum, and detect the appearance defects and the attenuation rate of electrical properties of the modules to determine the ability of the modules to resist the impact of hail.
(7) Aging test
The aging test is used to detect the effective anti-attenuation ability of the battery module when exposed to high humidity and high ultraviolet radiation.
The module sample is irradiated under ultraviolet sunlight with a temperature of 65°C and a spectrum of about 6.5, and finally the photoelectric characteristics are checked to see the drop loss. It is worth mentioning that in the exposure aging experiment, the electrical performance decline is irregular.