In the field of electrochemical energy storage, lithium-ion battery energy storage is currently the most mature and rapidly developing technology. Among them, lithium-ion battery pack technology is a crucial component. So, what exactly is a battery pack? What does its production line look like?
What is the Battery Pack?
A lithium-ion battery pack, also known as a battery module, is a manufacturing process for lithium-ion batteries. It involves connecting multiple lithium-ion cells in series and parallel configurations, taking into account factors such as system mechanical strength, thermal management, and BMS compatibility.
Its key technological aspects include overall structural design, welding, and processing technology control, protection rating, and active thermal management systems. For example, when connecting two batteries in series or parallel and forming a specific shape according to customer requirements, it is referred to as a battery pack.
Components of Battery PACK
The important components of a battery pack include four parts: individual battery modules, electrical systems, thermal management systems, casing, and BMS (Battery Management System).
Battery Module: If the battery PACK is likened to a human body, then the module is the “heart,” which is responsible for the storage and release of electrical energy.
Electrical System: Comprising components such as connecting copper busbars, high-voltage harnesses, low-voltage harnesses, and electrical protection devices.
The high-voltage harness can be seen as the “major arteries” of the battery pack, continuously delivering electrical energy to end loads, while the low-voltage harness can be likened to the “neural network” of the battery pack, transmitting real-time detection and control signals.
Thermal Management System: The thermal management system primarily operates in two modes: air cooling and liquid cooling, while liquid cooling is further divided into direct liquid cooling and immersion liquid cooling. The thermal management system is equivalent to installing an air conditioner for the battery PACK.
Batteries generate heat during discharge, and to ensure they operate at a reasonable ambient temperature, thereby enhancing battery cycle life, it is generally required that the temperature difference within the system is ≤5℃.
Case: It is mainly composed of case, case cover, metal bracket, panel, and fixing screws, which can be regarded as the “skeleton” of the battery PACK, providing support, mechanical impact resistance, mechanical vibration resistance, and environmental protection.
BMS: Abbreviated as “Battery Management System,” it serves as the battery’s “brain.” It is mainly responsible for measuring parameters such as battery voltage, current, and temperature, it also performs functions such as cell balancing. The data can be transmitted to MES(Manufacturing Execution System).
Characteristics of Battery PACK
Lithium battery PACK requires high consistency of the cells(capacity, internal resistance, voltage, discharge curve, and lifespan).
The cycle life of the battery pack is lower than that of a single cell.
Use under specified conditions (including charging and discharging current, charging method, temperature, etc.)
The battery voltage and capacity of the lithium battery PACK are greatly increased after molding and must be protected and monitored for charge balancing, temperature, voltage, and overcurrent.
The battery pack must meet the voltage and capacity requirements of the design.
PACK Method
Series-parallel configuration: The battery module is composed of individual cells connected in series and parallel.
Parallel connection increases capacity while voltage remains unchanged; series connection increases the voltage while capacity remains unchanged.
Example:
If individual cells with a voltage of 3.2V are connected in series, 15 cells in series result in 48V, which is series boosting.
If two cells with a capacity of 50Ah are connected in parallel, the total capacity is 100Ah, which is parallel expansion.
Cell requirements: Select corresponding cells according to design requirements.
Cells in parallel and series connections should have consistent types, and models, with differences in capacity, internal resistance, and voltage values not exceeding 2%. Whether they are pouch cells or cylindrical cells, multiple series combinations are required.
PACK manufacturing process: Battery packs are assembled through two main methods.
One is through laser welding, ultrasonic welding, or pulse welding, which are common welding methods known for their reliability but are not easily replaceable.
The other method involves contact via elastic metal strips, eliminating the need for welding and making battery replacement easier, though it may result in poor contact.
Considering production yield, efficiency, and internal resistance of connection points, laser welding is currently the preferred choice for many battery manufacturers.
What does a complete PACK line look like?
The lithium battery pack production line refers to a systematic collection of equipment and process flows required for producing lithium battery packs.
Typically, it includes six core stages: cell manufacturing, cell testing, cell grading, cell assembly, packaging, and quality inspection. Among these stages, cell manufacturing and cell assembly are the most critical as they directly influence the performance and quality of lithium battery packs.
Cell Manufacturing: This is the initial stage of the production line and can be further divided into the preparation of positive and negative electrode materials, cell molding, electrolyte injection, and cell aging.
Cell molding is the pivotal step, involving methods such as winding, stacking, and pressing, which determine the shape and size of the cell and directly impact its performance and lifespan.
Different molding methods are suitable for different lithium battery products, depending on specific requirements.
Cell Testing: This process primarily involves screening out unqualified cells, ensuring the smooth progress of subsequent production stages.
It mainly includes cell capacity testing, cell internal resistance testing, and cell temperature testing. These testing procedures help manufacturers understand the performance of cells, identify problems in time, and make adjustments and optimizations accordingly.
Exploring the Future Prospects of Lithium Battery Packs
As the energy storage battery market continues to expand, PACK production lines are continuously being refined and improved to enhance the performance and quality of battery packs.
With the popularization of automation, the PACK process will be transformed from labor-intensive to technical, focusing on parameter matching and battery pack design, while leaving the rest to machines.
In the future, the technological direction of lithium battery pack production lines mainly includes the following aspects:
Intelligence: By incorporating technologies such as artificial intelligence(AI) and the Internet of Things(IoT), achieve automation, intelligence, and informatization of production lines to improve production efficiency and product quality.
Environmentalization: Implement measures such as using environmentally friendly materials and energy conservation to achieve the environmentalization and sustainable development of the production process.
Personalization: Customize and provide services for production lines according to the needs and requirements of different customers to enhance customer satisfaction and loyalty.
Safety: Strengthen safety management and risk control to ensure the safety and stability of the production process.
How to Read Battery PACK Technical Parameters
| Item | Data |
| Configuration | 1P24S |
| Rated capacity | 280Ah |
| Rated voltage | 76.8V |
| Rated energy | 21.504kWh |
| Weight | 138±3kg |
Take the above parameters as an example
Configuration: 1P24S
S represents series cells, and P represents parallel cells. 1P24S means 24 series and 1 parallel.
The voltage is multiplied after the series connection, and the rated voltage is 3.2 * 24 = 76.8V.
Rated capacity: 280Ah
The battery’s rated capacity refers to the capacity at which the battery can continuously operate under rated conditions.
The rated capacity C of a battery, in ampere-hours (Ah), is the product of the discharge current in amperes (A) and the discharge time in hours (h). Therefore, 280Ah indicates that the battery can sustain a discharge at a maximum rate of 0.5C for 2 hours.
Rated energy: 21.504kWh
The rated energy (Wh) = nominal capacity (Ah) * nominal voltage (V), which also means that the total energy discharged from a battery is related to both capacity and voltage.
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