What is lithium-ion battery capacity rating?
The first explanation: Lithium-ion battery capacity grading: Simply put, it's capacity sorting and performance screening. During capacity grading, data from each testing point is obtained through computer management, allowing analysis of battery capacity, internal resistance, and other data to determine the quality grade of the lithium-ion batteries. This process is called capacity grading. After the initial capacity grading, lithium-ion batteries need to be left to stand for a period of time, generally no less than 15 days. During this period, some inherent quality problems will become apparent.
The second explanation is that even if a batch of lithium-ion batteries are the same size, their capacities will vary after production. Therefore, they must be fully charged according to specifications on the equipment and then discharged (completely discharged) according to the specified current. The time taken to completely discharge multiplied by the discharge current is the battery's capacity. Only lithium-ion batteries that meet or exceed the designed capacity are considered qualified; batteries with a capacity less than the designed capacity are not considered qualified. This process of screening qualified batteries through capacity testing is called capacity grading.
Applications of lithium-ion battery capacity testing
Capacity separation not only helps stabilize the SEI membrane, but also shortens the time consumed in the capacity separation process, reducing energy consumption while increasing production.
The produced lithium battery cells cannot be sold immediately. They should be stored in the warehouse for at least 15 days. During this period, some inherent defects will become apparent, such as excessive self-discharge. Cells that have reached their storage period in the warehouse will be taken out again for testing and capacity assessment after receiving an order. That is, they will be charged and discharged again to eliminate those that do not meet the capacity requirements or have quality problems. Then, they will be delivered to the sales department with about 50% of their capacity remaining, and finally to the mobile phone battery assembly plant.
Another purpose of capacity grading is to classify and group batteries, that is, to select cells with similar internal resistance and capacity for combination. During combination, only cells with very similar performance can be assembled into a battery pack. For example, to meet the energy demands of electric vehicles, power lithium-ion battery packs often consist of dozens to thousands of cells. Due to the complexity of the system, the behavior of the battery pack is unique; the performance of the battery pack cannot be obtained simply by adding or subtracting individual cells.
