The composition, method and parameter analysis of lithium battery energy storage system PACK!

Lithium -ion battery PACK technology is an important part of the energy storage industry skills. Let’s follow the editor to learn some basic knowledge of battery PACK.

1. Definition of lithium-ion battery Battery PACK, also known as battery module, is a lithium- ion battery manufacturing process. It means packaging, encapsulation, and assembly. It refers to connecting multiple lithium -ion single cell groups in parallel and series. It is formed by taking into consideration the system mechanical strength, thermal management, BMS matching and other issues. Its important technologies are reflected 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. The composition of the battery PACK The battery PACK mainly includes the single battery module, electrical system, thermal management system, box and BMS.

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? 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.

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? Electrical system: Mainly composed of connecting copper strips, high-voltage wiring harness, low-voltage wiring harness and electrical guarantee devices. The high-voltage wire harness can be regarded as the "artery blood vessel" of the battery PACK, which continuously delivers battery power to the end load. The low-voltage wire harness can be regarded as the "neural network" of the battery PACK, transmitting detection signals and control signals in real time.

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? Thermal management system : Thermal management system mainly includes 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 on the battery PACK.

The battery will generate heat in discharge mode. To ensure that the battery operates at a reasonable ambient temperature and improve the battery cycle life, the system temperature difference is generally required to be ≤5 °C .

? Box: Mainly composed of the box, box cover, metal bracket, panel and fixing screws, it can be regarded as the "skeleton" of the battery PACK, playing the role of support, resistance to mechanical impact, mechanical vibration and environmental protection.

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? BMS: Battery management system Battery management system can be regarded as the "brain" of the battery. It is mainly responsible for measuring parameters such as voltage, current and temperature of the battery, as well as balancing and other functions. Data can be transferred to MES.

3. Characteristics of battery PACK

? PACK 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 PACK is lower than that of a single battery.

??Use under limited conditions (including charging and discharging current, charging method, temperature, etc.)

??After the lithium battery pack is formed, the battery voltage and capacity are greatly improved, and must be protected and monitored for charge equalization, temperature, voltage and overcurrent.

??The battery PACK must meet the voltage and capacity requirements required by the design.

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4.PACK method

??Series and parallel composition: The battery module is composed of single cells connected in parallel and in series. Parallel connection increases the capacity, but the voltage remains unchanged. After series connection, the voltage doubles, but the capacity remains unchanged. For example: if 15 batteries with a voltage of 3.2V are connected in series, it will be 48V. This is a series boost. For example: if two batteries with a capacity of 50Ah are connected in parallel, they will have 100Ah. This is parallel expansion.

??Battery core requirements: Select the corresponding battery core according to your own design requirements. Batteries connected in parallel and in series must be of the same type and model, and the difference in capacity, internal resistance, and voltage value should not be greater than 2%. Whether it is a soft-pack battery or a cylindrical battery, multiple string combinations are required.

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? PACK process: Battery PACK is realized in two ways. One is through laser welding or ultrasonic welding or pulse welding. This is a commonly used welding method. The advantage is that it has better reliability but is not easy to replace.

The second is contact through elastic metal sheets. The advantage is that no welding is required and the battery is easy to replace. The disadvantage is that it may lead to poor contact.