Research on consistency of Grouped lithium batteries Based on Capacity Increment Curve

Lithium-ion batteries are the most widely used and reliable power source for electric vehicles. With the development of electric vehicles, the safety performance, energy density, life and reliability of lithium-ion batteries have been continuously improved. However, in the field of automotive power battery technology, battery cells are grouped in series and parallel to provide sufficient energy, but a major problem faced by grouped battery is the problem of consistency between battery cells. In this paper, the lithium iron phosphate battery capacity increase curve (IC curve) was used as an analysis tool. It is found that the IC curve characteristic peaks of different monomers in the battery pack can reflect the consistency between the monomers. On this basis, a mathematical model was established, which used the IC curve II peak feature point of a single cell as a reference to characterize the consistency of other monomers one by one, so as to evaluate the battery pack consistency problem and calculate it with the SOC-OCV curve. The actual capacity was compared and found to be consistent with the battery consistency trend of capacity characterization. This method can quickly describe the battery pack consistency problem, and can be applied during the normal charging process of the battery pack. During the whole life of the battery pack, the battery consistency can be determined in real time, which has certain practical value for the utilization and accurate management of the battery pack.