Design requirements and production process of electric vehicle power lithium battery pack. As one of the strategic models for the industrialization of new energy vehicles in my country, small pure electric vehicles have attracted more and more attention. As the only power source of pure electric vehicles, power lithium battery packs bear the mass of modules such as battery packs. Therefore, their strength and stiffness must meet the usage requirements to ensure driving safety.

　　Design requirements for electric vehicle power lithium battery packs

　　In the early stage architecture development of pure electric vehicle projects, how to reasonably arrange the integrated power lithium battery pack is crucial. The specific work elements mainly involve ground clearance, passability, collision safety and power demand, etc., which will be discussed below. introduce.

　　1.Battery ground clearance requirements

　　When the lower surface of the battery is protected by structural parts, the following conditions also need to be met: under the maximum jump state, the battery needs to ensure a certain gap from the ground; under full load, a competitive ground clearance must be ensured; the battery RESS The forward direction needs to be protected; the battery RESS arrangement must not be lower than the lowest surface of the surrounding body structure.

　　2. The limitations of the human-machine layout of the crew cabin on the Z-direction size of the battery

　　It can be seen from the human-machine layout of an electric vehicle project that there are a total of 9 engineering indicators that need to be considered in the Z-direction latitude, specifically the distance from the passenger's H point to the ground H5, the passenger's sitting height H30, the head space H61, and the distance from the heel point to the ground The distance to the ground H8, the Z-direction thickness of the battery pack, the ground clearance of the battery pack, the vehicle height H100, the distance from the upper surface of the lithium battery pack to the upper surface of the floor, and the thickness of the carpet and sound insulation cotton. Therefore, the height of the vehicle body is limited based on the styling requirements, and the Z-direction size limit surface of the battery pack can be derived based on the human-machine layout requirements.

　　3. The limitations of the collapse space on the Y-direction size of the battery

　　Since the working voltage of the battery is generally higher than 300?V, and the electrolyte in the battery cell is highly corrosive, a reasonable safety collapse gap needs to be set when the lithium battery pack is laid out in the vehicle. Collision conditions are particularly harsh. Specific vehicle models need to use CAE iterative analysis methods to arrive at a reasonable design of the lateral collapse distance from the battery to the rocker panel.

　　4. The limitations of the vehicle load transfer path on battery pack design

　　The load transfer path of the entire vehicle can be roughly decomposed into: front cabin load path, front and center floor load transfer and rear floor load path. Since future lithium battery pack layout plans are basically laid out under the floor, the design of the front and middle floor load transfer paths is closely related to the structural plan of the battery pack.

　　After topology optimization, the load transfer under the floor is mainly accomplished by arranging the longitudinal beam extension beam on the side of the battery and the No. 1.5 beam in front of the battery. As shown in Figure 8, the purple longitudinal beam in the figure passes through the triangular structure and the No. 1.5 beam. The beam is connected to the longitudinal beam of the front cabin for load transfer in a frontal collision; at the same time, the battery frame should also serve as a load transfer path to cooperate with the body load path; the beam structure inside the battery pack should be connected with the body's No. 2/3/4 beams and the central channel The beam position remains consistent.

　　5. The demand for electric power due to cruising range

　　For the same battery unit module, the cruising range is related to the energy density and capacity of the battery, and the capacity parameters of the battery are determined by the number and method of series and parallel connection of its internal battery cells, which will eventually lead to a power lithium battery pack. Changes in overall shape and size. Table 2 details the differences in battery power and battery pack size due to differences in the energy density and series-parallel connection methods of cells and modules under the same cruising range target requirements for battery packs from different suppliers.

　　6. Battery pack installation interface requirements

　　The installation method of the power lithium battery pack on the vehicle directly affects its mode and strength. Generally, installation points need to be arranged at regular intervals around the battery pack. If the overall battery pack length is greater than 2mm, it is recommended to add hanging points in the middle. Improve modal.

　　The power lithium battery pack is the core energy source of new energy vehicles, providing driving power for the entire vehicle. It mainly forms the main body of the battery pack through a metal shell envelope. The modular structural design realizes the integration of battery cells, and the thermal management performance of the battery pack is optimized through thermal management design and simulation. The electrical components and wiring harness realize the safety protection and connection path of the battery by the control system; the management of battery cells is realized through BMS. , as well as communication and information exchange with the entire vehicle.

　　Power lithium battery pack production process

　　The production process from a simple battery cell to a lithium battery pack is also quite complicated and requires multiple processes. It is no simpler than the manufacturing process of battery cells.

　　1. Loading materials

　　The battery core is transferred to the designated position, and the robot automatically grabs it and sends it to the module assembly line.

　　2. Give the battery core a bath—plasma cleaning process

　　Clean the surface of each cell. Ion cleaning is used here to ensure that contaminants during the process do not adhere to the bottom of the battery cells.

　　3. Assemble the battery cores - apply glue to the battery cores

　　Before the battery core is assembled, the surface needs to be coated with glue. In addition to fixing, the glue also serves the purpose of insulation and heat dissipation. High-precision gluing equipment and robots work together to apply glue at a set trajectory, while monitoring the quality of the glue in real time to ensure the quality of the glue and further improve the consistency of each set of different battery modules.

　　4. Build a home for the battery core - welding of end plates and side plates

　　Power lithium battery modules are mostly welded with aluminum end plates and side plates, and are laminated and welded by robots.

　　5. Wire harness isolation board assembly

　　After the welding monitoring system accurately locates the welding position, it binds the material barcode of the wire harness isolation plate to the MES production scheduling management system to generate a separate code for traceability. After coding, the wiring harness isolation board is automatically loaded into the module through a robot.

　　6. Complete the series and parallel connection of batteries - laser welding

　　Through automatic laser welding, the connection between the pole posts and the connecting piece is completed, and the battery series and parallel connection are realized.

　　7. An important step before going offline—offline testing

　　Check the full performance of the module before going offline, including module voltage/resistance, battery cell voltage, withstand voltage test, and insulation resistance test. The standardized module design principle can be customized to match different models, and each module can also be installed in the best suitable space and predetermined position in the car.

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