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Among the three common packaging forms of lithium battery, the single energy density of the soft pack battery is the easiest to be high. However, at the level of module design, the task of considering the overall safety of the product is the most important. It can be said that the activity of a part of the cell is transferred to the module structure.

Main components of the module

There is a big gap in the design and selection of soft pack batteries. The above one is a more typical form. Its basic components include: module control (commonly referred to as BMS slave board), battery unit, conductive connector, plastic frame, cold plate, cooling pipe, pressing plates at both ends and a set of fasteners that combine these components. In addition to the function of gathering the single electric core and providing a certain pressure, the pressing plate at both ends often designs the fixed structure of the module in the pack.

Structural design requirements. Reliable structure: anti-seismic, dynamic and anti fatigue; controllable process: no over welding and lack of welding, ensuring 100% of the electric core without damage; low cost: low automation cost of pack production line, including production equipment and production loss; easy to split: battery pack is easy to maintain and repair, low cost, and the electric core can be echeloned and used well; To achieve the necessary heat transfer isolation and avoid the rapid spread of runaway heat, this step can also be considered in the package design.

General module optimization approach. Improving space utilization is also an important way to optimize the module. Power battery pack enterprises can improve the design of module and thermal management system, reduce the cell spacing, so as to improve the utilization of space in the battery box. Another solution is to use new materials. For example, the bus bar in the power battery system (bus in parallel circuit, generally made of copper plate) is replaced by aluminum, and the module fixings are replaced by high-strength steel and aluminum, which can also reduce the weight of the power battery.

Thermal design

The physical structure of the flexible core determines that it is not easy to explode. Generally, only when the pressure that the shell can bear is high enough, it can explode. When the internal pressure of the flexible core is large, it will start to release pressure and leakage from the edge of the aluminum plastic film. At the same time, the soft clad core is also one of several core structures, with the best heat dissipation.

At present, the mainstream cooling methods have been transformed into liquid cooling and phase change material cooling. Phase change material cooling can be used together with liquid cooling, or alone in the environment is not too bad. In addition, there is also a process which is still widely used in China at present. Here is filled with a thermal conductivity far greater than that of air. The heat released by the telecommunication is transferred to the module shell by the heat conductive adhesive, and then further distributed to the environment. In this way, it is impossible to replace the electric core by itself again, but to a certain extent, it also prevents the spread of thermal runaway.

Electrical design, including low-voltage and high-voltage two parts.

High voltage design is mainly the series and parallel connection between the electric core and the electric core, as well as the external part of the module, to design the connection and conductive mode between the module and the module. Generally, the series connection mode is only considered between the modules. These high-voltage connections need to meet two requirements: first, the conductive parts and contact resistance between the cores should be evenly distributed, otherwise the detection of single voltage will be disturbed; second, the resistance should be small enough to avoid the waste of electric energy in the transmission path.

safety design

Safety design can be divided into three backward requirements: good design to ensure no accidents; if not, it is better to give early warning to people in advance to reflect the time; if faults have occurred, the design goal is to prevent the accident from spreading too fast.

The first goal is to achieve a reasonable layout, a good cooling system, and a reliable structural design; the second goal is to make the sensor more widely distributed to every possible fault point, and comprehensively detect the voltage and temperature