The harm of inconsistency of lithium ion battery and its treatment method

The harm of lithium-ion battery inconsistency and its treatment method The answer of lithium-ion battery manufacturers is that the inconsistency of battery performance is formed during the production process and deepened during use. The batteries in the same battery pack are weak, and become weaker with acceleration. As the degree of aging deepens, the dispersion of parameters among single cells increases. Power lithium-ion battery has firmly occupied the leading position of electric vehicle power supply. Long service life, high energy density, and great potential for improvement. Security can be changed, and energy density can continue to rise. In the foreseeable future (rumored around 2020), it will be possible to catch up with the endurance and cost-effectiveness of gasoline-powered vehicles, and enter the first stage of maturity of electric vehicles. However, lithium-ion batteries also have their own problems. The inconsistency of battery performance is formed during the production process and deepens during use. The batteries in the same battery pack are weak, and become weaker with acceleration. As the degree of aging deepens, the dispersion of parameters among single cells increases. At present, engineers should be inconsistent with single cells, and there are three important aspects. A single battery is divided into several groups for thermal management. The battery management system provides a balancing function when there is a small amount of inconsistency. 1) Theoretically, different batches of cells cannot be used at the same time. Even the batteries of the same batch must be screened. The relatively concentrated parameter batteries are in one battery pack and the same battery pack. The purpose of sorting is to select cells with similar parameters. The sorting method has been studied for many years, divided into static sorting and dynamic sorting. Static sorting is to screen characteristic parameters such as open circuit voltage, battery internal resistance, capacity, etc., select target parameters, introduce statistical algorithms, set screening criteria, and finally divide the same batch of batteries into several groups. Dynamic screening is to screen the characteristics of the battery during charging and discharging. Some choose the constant current and constant voltage charging method, some choose the pulse pulse charging and discharging method, and some compare the relationship between their own charging and discharging curves. Static screening is combined with static screening, and static screening is used for preliminary grouping, and dynamic screening is carried out on this basis. In this way, there are more groups and higher screening accuracy, but the cost will increase accordingly. Here is a demonstration of the importance of small-scale lithium-ion battery production. Large-scale shipments can allow manufacturers to perform more complex sorting, thereby bringing battery pack performance closer. If the output is too small, there are too many packs, and one batch cannot be equipped with battery packs, even the best method cannot be used. 2) Thermal management Regarding batteries with inconsistent internal resistance, the heat generated is also different. The thermal management system can adjust the temperature difference of the entire battery to keep it within a small range. The battery with more heat is still rising in high temperature, but it will not be separated from other batteries, and there will be no significant difference in the degree of deterioration. 3) Balance the inconsistency of cell monomers and the terminal voltage of some cells always reach the control threshold earlier than other cells, resulting in a decrease in the capacity of the entire system. In order to solve this problem, the battery management system BMS has designed a balance function. One of the batteries is the first to reach the charge cut-off voltage, while the voltage of the other batteries lags behind significantly. The BMS can start the charge equalization function, and can also discharge part of the high-voltage battery by connecting a resistor, or transfer the energy to the low-voltage battery. In this way, the cut-off condition is removed and the charging process is restarted, so that the battery pack is charged with more energy. So far, cell inconsistency is still an important area of u200bu200bresearch in the industry. No matter how high the energy density of the battery is, if it is subject to inconsistent interference, the capacity of the battery pack will be greatly reduced. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.