Knowledge of Lithium Battery PACK
Lithium batteries are favored by industries such as consumer electronics and power tools due to their high energy density, high voltage, environmental protection, long life and fast charging. Their contribution to the new energy vehicle industry is particularly outstanding. As the world's energy crisis and environmental protection issues become increasingly prominent, the lithium battery industry, as a power source for new energy vehicles, has huge market potential and is an important part of the national strategic development.
1. What is a battery PACK?
Lithium-ion battery PACK, also known as battery module, is a manufacturing process for lithium-ion batteries. It refers to connecting multiple lithium-ion single cell groups in parallel and in series, and considering system mechanical strength, thermal management, BMS matching and other issues. Its important technologies are reflected in overall structural design, welding and processing technology control, protection level, active thermal management system, etc. If two batteries are connected in series or in parallel to form a specific shape according to customer requirements, it is called PACK.
2. Composition of battery PACK
Battery PACK mainly includes single cell modules, electrical systems, thermal management systems, boxes and BMS.
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.
Electrical 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 "aorta" 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, which transmits detection signals and control signals in real time.
Thermal management system: The thermal management system mainly has two methods: 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 for the battery PACK. There are many assembly types of air cooling systems, and the core components are mainly compressors, fans, heat exchangers, etc.
Box: It is mainly composed of a box, a box cover, a metal bracket, a panel, and fixing screws. It can be regarded as the "skeleton" of the battery PACK, which plays a role in support, resistance to mechanical shock, mechanical vibration and environmental protection.
BMS: Battery management system, which can be regarded as the "brain" of the battery. It is mainly responsible for measuring the battery's voltage, current, temperature and other parameters, and also has functions such as balancing. Data can be transmitted to MES.
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3. Characteristics of battery PACK
1. PACK lithium battery packs require batteries to have high consistency (capacity, internal resistance, voltage, discharge curve, life).
2. The cycle life of the battery pack PACK is lower than that of a single battery.
3. Use under limited conditions (including charging and discharging current, charging method, temperature, etc.)
4. After the lithium battery pack PACK is formed, the battery voltage and capacity are greatly improved, and it must be protected, and the charging balance, temperature, voltage and overcurrent monitoring are performed. Battery aging machine can be used to detect the battery's current, voltage, capacity, etc.
5. The battery PACK must meet the voltage and capacity requirements required by the design.
4. PACK method
Series-parallel composition: The battery module is composed of single cells connected in parallel and in series. Parallel connection increases capacity, and the voltage remains unchanged. After series connection, the voltage doubles, and the capacity remains unchanged. For example: 15 cells with a voltage of 3.2V are connected in series, which is 48V, which is a series voltage boost. For example: two cells with a capacity of 50Ah are connected in parallel, which is 100Ah, which is parallel capacity expansion.
Cell requirements: Select the corresponding cell according to your own design requirements. The batteries in parallel and series require the same type and model, and the difference in capacity, internal resistance, and voltage value is no more than 2%. Whether it is a soft-package battery or a cylindrical battery, multiple strings are required.
Lithium Spot Welding Machine
PACK process: The battery PACK is realized in two ways. One is through laser welding, ultrasonic welding, or pulse welding. This is a commonly used welding method with good reliability. The second is through elastic metal sheet contact. The advantage is that no welding is required and the battery is easy to replace.
