Lithium battery Inconsistent performance
The voltages are inconsistent.
After the formation, they undergo the same charging and discharging process and are left to stand for a sufficient time. At the same ambient temperature, the cells to be evaluated are charged to the same SOC. Measuring the open circuit voltage, the voltage difference reflected at this time is the voltage inconsistency of the single cell. Studies have shown that the open circuit voltage of a single cell is in accordance with a normal distribution. That is to say, all our efforts to improve consistency can only change the concentration of parameters.
The internal resistance is inconsistent, and the internal resistance of the battery is an important characteristic of the power characteristics of the battery. It is also one of the reasons for further discretization of the performance parameters of the battery after the battery is grouped. Inconsistent internal resistance can cause inconsistent temperature rise, which is a cause of further discretization of other parameters.
The internal resistance is also the detection index after the mold group is formed. From the assembly of the cell to the module, it is necessary to go through a group process such as welding or mechanical structure clamping. The consistency of the group process is reflected to the module after molding, which is the internal resistance of the module.
The capacity is inconsistent and the lifespan is inconsistent. According to the current life measurement standard, the available capacity and life are closely linked together.
The capacity is generally used as the primary selection of the battery group, and is the most important parameter performance of the cell inconsistency. There are many reasons for inconsistent capacity, and most of them are inconsistent results of the manufacturing process.
In addition to achieving life, internal resistance and other life indicators, another meaning of inconsistent life is that battery failure time is inconsistent. Studies have shown that it is not necessarily the smallest capacity cell or the most difficult cell in the working condition to reach the end of life. Every cell has its ability to resist aging since birth.
The temperature rise is inconsistent. In addition to the internal resistance factor that directly affects heat generation, each cell has an inconsistent formation in the internal electrochemical material manufacturing process, which also affects the heat generation. Each cell has a different position in the battery pack, causing a difference in its heat dissipation conditions, which will eventually lead to inconsistent temperature rise of the cell.