he role of power battery system
As we all know, traditional cars use fuels such as oil or gas as energy sources, and these fuels are stored in fuel tanks or gas storage tanks on the body. The internal combustion engine system burns these fuels to produce mechanical energy, which provides driving force for vehicle driving, as shown in Figure 1.
The electric part of electric new energy vehicles is driven by electricity. The electric energy it needs is stored in the power battery system installed on the body, and the electric energy is converted into mechanical energy through the motor drive system to provide driving force for the vehicle to travel, as shown in Figure 2.
In terms of function, the fuel tank or gas storage tank is the fuel storage device of the traditional automobile, the power battery system is the electric energy storage device of the electric new energy vehicle, and the charged power battery system is the power source of the new energy vehicle.
Design concept of power battery system
The power battery system itself is a complex system integrating chemical, electrical and mechanical characteristics. The system design must take into account the satisfaction of all aspects, especially the safety and life attenuation contained in the chemical characteristics of the battery, which cannot be directly observed and evaluated, and it is not easy to predict in a short time.
In addition, when the power battery is installed on the car, the complicated and changeable application environment must be considered. To ensure the long-term safety and durability of the battery system, it is necessary to define how to use and maintain it in the design phase.
Therefore, in the battery system design, we need to pay attention to the two “iron triangles” shown in Figure 3. The first triangle shows that the three technologies that the battery system R&D and manufacturing rely on are indispensable (see the subsequent system architecture analysis for details). The second triangle indicates that battery system products must be defined and controlled in their entire life cycle in accordance with the concept of automobile development, from product R&D and manufacturing to application maintenance to ensure easy use.
The composition of the power battery system and related technologies
In general, the power battery system mainly includes power battery monomer (or module), BMS (battery management system, generally including a single monitoring unit, main control unit and high voltage modules), structural parts (contains structural parts such as box body, mounting parts, conductive metal parts, seals, etc.), high and low voltage wiring harness (including connectors and plug-in terminals, etc.), thermal management modules (water-containing cold plate, fan or heating plate, etc.), as shown in Figure 2-13.
For smaller battery systems, such as Start-Stop (start-stop) system power supply, because it mainly works in the pulse power state, it is converted into a smaller average power and less heat. Coupled with cost factors, such systems generally do not require special thermal management components. The shell is not only a structural part, but also a natural heat dissipation surface. In addition, because the PCB board is used instead of the wire harness to conduct electricity, the wire harness part is also invisible, as shown in Figure 5.
It can be seen from the above battery system composition that although different battery systems have differences in shape, size, internal structure and group technology, the most basic technical classifications used are the same, including power battery technology, BMS technology, group technology (can be subdivided into thermal management components, structural design, electrical connection, wiring harness design).