The importance of the pre-inspection process for 18650 cylindrical cell PACK.
Due to the high degree of automation in production, good stability, and high replaceability of 18650 lithium-ion power batteries, these batteries possess unparalleled unique advantages in terms of modularization and standardization in system development. They can effectively reduce production costs and save labor.
Apart from the established Tesla, Porsche and domestic brands such as JAC, Zotye, Changan, and Guangzhou Automobile have also joined the research and development team for 18650 battery models. Industry insiders say that more models will "fall in love" with 18650 batteries in the future, driving a revolutionary change in the application of 18650 batteries.
However, everything has its dual nature, and it is common for things to have both advantages and disadvantages. Apart from the aforementioned advantages, the disadvantages of 18650 batteries cannot be ignored. The biggest drawback of 18650 batteries currently lies in their low individual battery capacity, generally around 2~4Ah. Therefore, electric vehicles require a large number of batteries, such as Tesla cars, which require 7000-8000 18650 batteries reliably connected into modules. Such a large number of batteries makes battery management more complex and requires higher consistency.
In the field of multi-series and parallel systems, such as electric vehicles, battery inconsistency can affect the battery's performance and even pose some safety hazards.
When lithium-ion batteries are used individually or in small-scale series-parallel configurations, their safety issues can generally be controlled. However, when lithium-ion batteries are used in large-scale groups, especially as power batteries for electric vehicles, their safety issues become more prominent. When lithium-ion batteries are used in groups, due to the large number of individual cells and complex structure, the issues of consistency screening and matching, as well as consistency management, become more difficult. This makes the "short-board" batteries within the battery pack prone to excessive aging, thus increasing the likelihood of safety accidents during use.
Therefore, to address the safety issues of lithium-ion battery packs, it is both necessary and urgent to enhance the safety technology of lithium-ion batteries from the perspective of the battery pack system, while improving the safety of individual battery cells.
There are various sources of inconsistency. The materials used to construct batteries are inherently not completely uniform, and the manufacturing process of batteries cannot be controlled to ensure that every battery is identical in every detail. This leads to inconsistencies in capacity, terminal voltage, internal resistance, and lifespan, among others. It is difficult to fundamentally resolve these issues. Therefore, it is necessary to conduct testing and screening of the cells before assembling them into a battery pack.
In addition to screening electrical performance, the appearance of
18650 batteries also needs to be inspected. For example, defects such as scratches, damages, stains, pits, and bumps on the battery surface will affect the assembly of battery modules and the safety characteristics after grouping.
For example, damage to the plastic coating on the surface of the battery poses a safety hazard of short circuit;
Stains, pits/bumps, etc. on the end surface can also affect the soldering stability of the circuit;
The flatness of the plastic coating will also affect the efficiency of module assembly.
In addition, the consistency of the length and end face diameter of the cells will also affect the production efficiency of module assembly.
Therefore, appearance inspection is also a crucial and indispensable step before the PACK process.
