Common ordinary cell modules include epoxy resin glue sealing plate modules, transparent PET laminate modules and tempered glass laminate modules. Among them, epoxy resin sealing board modules and transparent PET laminated board modules are generally small modules with a power less than 2W, which are mainly used for low-power products such as solar turf lights, road stud lights, and various solar toys; the power of the tempered glass laminate module can be 3~400w, which is the mainstream product used in the current photovoltaic power generation system. The composition and working principle of these types of battery modules are respectively introduced below.
1. Transparent PET laminate modules
The appearance of the transparent PET laminate assembly is shown in Figure 1. It is mainly composed of batteries, transparent PET film, printed circuit boards or plastic substrates, etc. The specific size and shape are also determined according to the needs of the product. Transparent PET laminates are generally also used in low-power circuits, and the power is generally less than 2W. The modules shown in Figure 1 are used in solar fan caps.
The structure of the transparent PET laminate is shown in Figure 2. It can be seen from the figure that its structure is similar to the epoxy resin package assembly, except that the epoxy resin glue is changed to a transparent PET film. PET is a composite material with strong corrosion resistance, aging resistance, good light transmittance and electrical insulation properties. One side of the film is smooth, and the other side is compounded with EVA film. EVA looks like a thin layer of transparent plastic paper at room temperature. In fact, EVA is a special film with high light transmittance. It melts at high temperature and acts as a bonding agent to bond the PET film, battery sheet and printed circuit board or other backplane materials together to form a sandwich-like structure, which is transparent and has good airtightness, to protect the cell from all kinds of corrosion. This packaging form is the same as the tempered glass packaging form, and needs to be laminated and cured in a laminating machine dedicated to the production of battery modules. The steps are vacuuming, heating, laminating, curing, etc. The detailed working process of the laminator is introduced in the next section. Due to the difference in packaging technology, battery modules encapsulated in transparent PET are easier to make than modules encapsulated in epoxy resin, and have a slightly longer working life. The PET film encapsulation process has the advantages of environmental protection, UV resistance and non-yellowing, and can replace the epoxy resin encapsulation process.
2. Tempered glass laminate modules
Tempered glass laminate modules are also called flat-panel battery modules. As shown in Figure 3, they are currently the most commonly seen and most commonly used battery modules. Tempered glass laminate modules are mainly composed of panel glass, silicon cells, two-layer EVA film, TPT backplane film, aluminum alloy frame and junction box, as shown in Figure 4. The panel glass covers the front of the battery module and constitutes the outermost layer of the module. It must have a high light transmittance, but also be strong and durable, and play a long-term role in protecting the battery. Two layers of EVA film are sandwiched between the panel glass, the battery sheet and the TPT back sheet film. Through the melting and solidification process, the glass, the battery sheet and the back sheet film are condensed into one body. TPT backsheet film has good weather resistance and can be firmly combined with EVA film. The aluminum alloy frame inlaid around the battery module not only protects the module, but also facilitates the installation and fixation of the module and the combined connection between the battery module square arrays. The junction box is fixed on the back plate with adhesive silica gel as a connecting part between the lead wires of the battery assembly and the outer leads.
