How to deal with the inconsistency of the battery

The inconsistency of battery core performance is formed during processing and deepened during use. The battery cells in the same battery pack are always weak for the weak, and become weaker at an accelerated rate. The degree of dispersion of the parameters between the single cells increases as the degree of aging deepens. At present, engineers must consider three aspects to deal with the inconsistency of single cells. Single battery sorting, thermal management after grouping, the battery management system provides equalization function when there is a small amount of inconsistency. 1. Separate different batches of batteries and theoretically do not put them together for use. Even cells of the same batch must be screened, and cells with relatively concentrated parameters are placed in a battery pack and in the same battery pack. The purpose of sorting is to select cells with similar parameters. The sorting method has been studied for many years, and it is important to be divided into two categories: static sorting and dynamic sorting. ① Static sorting. Screen the characteristic parameters such as open circuit voltage, internal resistance and capacity of the cells, select the target parameters, introduce statistical algorithms, set the screening criteria, and finally divide the cells of the same batch into several groups. ②Dynamic screening. It is based on the characteristics of the battery cell during the charging and discharging process. Some choose the constant current and constant voltage charging process, some choose the pulse impulse charging and discharging process, and some compare the relationship between their own charging and discharging curves. ③Combined dynamic and static sorting. Static screening is used for preliminary grouping, and dynamic screening is performed on this basis, so that more groups are divided and the screening accuracy is higher, but the cost will rise accordingly. Here is a small reflection of the importance of the processing scale of a power lithium battery. Large-scale shipments allow manufacturers to perform finer sorting and obtain battery packs with closer performance. If the output is too small and there are too many groups, no one batch can be equipped with a battery pack, no matter how good the method is. 2. Thermal management aims at the battery cells with inconsistent internal resistance and the problem of different heat. The addition of the thermal management system can adjust the temperature difference of the entire battery pack to keep it within a small range. Cells that generate more heat still have a high temperature rise, but they will not be far apart from other cells, and there will be no clear gap in the degradation level. 3. Balance the inconsistency of the battery cells. The terminal voltage of some battery cells is always ahead of other batteries and reaches the control threshold first, which leads to a reduction in the capacity of the entire system. In order to solve this problem, the battery management system BMS has designed a balancing function. A certain cell first reaches the charging cut-off voltage, while the voltage of the other cells clearly lags behind. BMS activates the charge equalization function, or connects a resistor to release part of the high-voltage cell's power, or transfer the energy away and put it to low The voltage cell goes up. In this way, the charging cut-off condition is lifted, the charging process is restarted, and the battery pack is charged with more power. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.