1 What is the battery pack? Lithium-ion battery pack, also known as battery module, is a lithium-ion battery manufacturing process, which refers to the connection of multiple lithium-ion cell groups in series, and considering the mechanical strength, thermal management, BMS matching and other issues of the system. Its important technologies are embodied in the overall structural design, welding and processing process control, protection level, active thermal management system, etc. If two batteries are connected in series or parallel to form a specific shape according to customer requirements, it is called pack.
2 Composition of the battery packThe important components of the battery pack include:Single battery modules, electrical systems, thermal management systems, cabinets, BMSThese four parts. 
Battery Module:If the battery pack is compared to a human body, then the module is the "heart", responsible for the storage and release of electrical energy. 
Lithium titanate battery moduleElectrical system:It is mainly composed of connecting copper bars, high-voltage wiring harnesses, low-voltage wiring harnesses and electrical guarantee devices. The high-voltage wiring harness can be regarded as the "aortic blood vessels" of the battery pack, which continuously transmits the battery power to the end load, and the low-voltage wiring harness can be regarded as the "neural network" of the battery pack, transmitting detection signals and control signals in real time. 
Energy storage high-voltage wiring harnessThermal Management System:There are two main ways of thermal management system: air cooling and liquid cooling, and liquid cooling can be divided into cold plate liquid cooling and immersion liquid cooling. The thermal management system is equivalent to installing an air conditioner in the battery pack. The battery will generate heat in the discharge mode, and in order to ensure that the battery works at a reasonable ambient temperature and improve the cycle life of the battery, the system temperature difference is generally required to be 5. 
There are a variety of assembled core components of the air-cooling system, mainly compressors, fans, heat exchangers, etc
Schematic diagram of the energy storage liquid-cooled temperature control systemCabinet:It is mainly composed of the box, the box cover, the metal bracket, the panel and the fixing screw, which can be regarded as the "bone" of the battery pack, which plays the role of support, mechanical shock resistance, mechanical vibration and environmental protection. 
Battery pack case▷ bms：The abbreviation of "battery management system", that is, battery management system, can be compared to the "brain" of the battery. It is mainly responsible for measuring the voltage, current and temperature of the battery, as well as equalizing and other functions. Data can be transmitted to MES. 
BYD 300A BMS control box
Juwei BMS
3 Features of the battery packPack lithium battery pack requires the battery to have a high degree of consistency (capacity, internal resistance, voltage, discharge curve, life); The cycle life of the battery pack is lower than that of a single battery; Use under limited conditions (including charging, discharging current, charging method, temperature, etc.); The battery voltage and capacity are greatly improved after the lithium battery pack is formed, and it must be protected, and the charge balance, temperature, voltage and overcurrent monitoring must be carried out; The battery pack must meet the voltage and capacity requirements required for the design.
4 pack approachSeries-and-parallel: The battery module is composed of single cells through and in series. Increase the capacity in parallel and the voltage remains the same, and the voltage doubles after series connection and the capacity remains the same. For example, the voltage is 3For 2V cells, 15 in series are 48V, which is series boost; For example, if a battery cell with a capacity of 50Ah is connected in parallel to have 100Ah, it is parallel expansion. Cell requirements: select the corresponding battery cells according to their own design requirements, and the types of batteries connected in parallel and series are required to be the same, and the difference in capacity, internal resistance and voltage value is not more than 2%. Whether it is a flexible packaging battery or a cylindrical battery, a combination of multiple strings is required. The process of pack: The pack of the battery is realized in two ways, one is through laser welding or ultrasonic welding or pulse welding, which is a commonly used welding method, and the advantage is that the reliability is good, but it is not easy to replace. The second is through the elastic metal sheet contact, the advantage is that there is no need for welding, the battery is easy to replace, and the disadvantage is that it may lead to poor contact. Considering the production yield, efficiency and internal resistance of the connection point, laser welding has become the first choice for many battery manufacturers. 5 What does a complete pack production line look like? A lithium battery pack production line refers to a series of systems that collect the equipment and processes required to produce a lithium battery pack. Usually included:Cell manufacturing, cell testing, cell grading, cell assembly, packaging and quality inspectionThese 6 core links, in these links, cell manufacturing and cell assembly are the most core, which directly affect the performance and quality of lithium battery packs. Cell Manufacturing:It is the first link in the production line, which can be divided into the preparation of positive and negative electrode materials, cell molding, cell injection and cell maturation. Cell forming is the most critical step, and there are winding, stacking, and stamping methods, which determine the shape and size of the cell, which directly affects the performance and life of the cell. Different molding methods are suitable for different lithium battery products, depending on the situation. Cell Testing:This process is mainly to screen out the unqualified battery cells to ensure the smooth progress of the subsequent production process. It mainly includes cell capacity test, cell internal resistance test and cell temperature test. These test items can help manufacturers understand the performance of battery cells, identify problems in time, and make adjustments and optimizations. 6. Analysis of the future prospects of lithium battery packWith the continuous expansion of the energy storage battery market, the PACK production line is also constantly improving and improving to improve the performance and quality of battery packs. When automation becomes widespread, the pack process will shift from labor to technology, work parameter matching and battery pack design, and leave the rest to the machine. In the future, the technical direction of lithium battery pack production line mainly includes the following aspects:
1. Intelligent:Through the introduction of artificial intelligence, Internet of Things and other technologies, the automation, intelligence and informatization of the production line are realized, and the production efficiency and product quality are improved.
2. Greening:Through the use of environmentally friendly materials, energy conservation and emission reduction measures, the green and sustainable development of the production process is realized.
3. Personalization:According to the needs and requirements of different customers, realize the personalized customization and service of the production line, and improve customer satisfaction and loyalty.
4. Safety:By strengthening safety management and risk control, the safety and stability of the production process are guaranteed.
7 How to understand the technical parameters of the battery pack
Take the above parameters as an exampleCombination:1P24SS represents series cells, P represents parallel cells, and 1P24S represents 24 strings and 1 parallel. After series connection, the voltage is doubled, and the rated voltage is 32*24=76.8v。Rated Capacity:The rated capacity of 280ah battery refers to the capacity of the battery to work continuously for a long time under the rated working conditions. The rated capacity of the battery c, in ampere-hours (AH), is the product of the discharge current ampere (a) and the discharge time hour (h). So 280ah means 0The current discharge of 5C can be continuously discharged for 2h. Rated energy:21.504kWh Rated Energy (Wh) = Nominal Capacity (AH) * Nominal Voltage (V), which also represents:The total amount of energy emitted by a battery is related to its capacity and voltage.