What are the effects of voltage consistency on the use of lithium batteries in series?

The impact of voltage consistency on the use of lithium batteries in series Abstract: The cycle life of 18650 single cells under different charging voltages and over-discharge currents was tested. The SOC of the battery pack is caused by a quantitative difference, and the voltage inconsistency of the battery pack is due to the self-discharge of a single battery being used in series, which leads to the cycle process of single battery over-discharge and the attenuated battery pack cycle life. A three-electrode system was used to measure the potential relationship between the positive and negative electrodes of a real battery during charging and discharging. Lithium battery; Consistency; Overcharge; Discharge; Consistency in the series of lithium batteries is the user's requirement for the battery. In the field of multiple series combination, the inconsistency of the battery will affect the performance of the battery, and even bring safety risks. There are many factors that cause inconsistent use of multiple series of batteries, including the original battery itself, such as inconsistent capacity, inconsistent self-discharge rate, inconsistent internal resistance, and inconsistent life. There are also external reasons, such as different battery cooling environments, internal resistance between different battery connections, and even uneven discharge caused by the detection circuit. This article discusses the impact of voltage inconsistency on the use of multiple batteries. Inconsistent battery voltage is a common problem in practical applications, and voltage is also the most important monitoring parameter in the battery management system. In practical applications, the important reasons for the inconsistent battery voltage are uneven capacity and battery self-discharge, and the inconsistent battery voltage affects the use of batteries in series. The battery used in this article is a 18650 cylindrical power lithium-ion battery. A battery in the over-charge cycle life test is charged with 2C constant current, and the current is less than 0.05 degrees at a different voltage, and then 10 points of current are transferred to a battery in the over-discharge cycle life test, using 2C constant current charging, 4.2V Constant voltage current is less than 0.05C, then 1C, 10C constant discharge to 1.0, 2.5V. The cycle life test of the 5S1P combination uses 2c constant current to 21.0v, 21.0v constant voltage to 0.05c, and 10c discharge to 12.5v. During the test, single battery overcharge and overdischarge protection is not performed. Regarding the three-electrode test of the battery, the reference electrode uses a nickel wire with a diameter of 1 mm. The circumferential surface of the nickel wire is wrapped with a metal lithium sheet, which is ground on the glass surface, so that fresh metal lithium is tightly wrapped on the nickel wire as a metal lithium reference electrode. After the 18650 battery is discharged, remove the battery cover with pliers. Then insert the reference electrode into the center hole of the electrode assembly, and inject the electrolyte into the center hole. Make a plastic cover from the PP material that has been perforated in advance, and seal it with Parafilm tape. Finally, the three-electrode system was measured in a dry room with a humidity of less than 1%. Test content: 1.1 Single battery cycle life under different charging voltage 1.2 Single battery over-discharge cycle life 1.3 Uniform voltage impact on battery pack cycle life 1.4 Charge and discharge of true battery three-electrode system This article measured the difference in lithium batteries in 18650 years Different cycle performance of charge voltage and discharge current, voltage and initial SOC difference, manual simulation of battery self-discharge leads to inconsistent series battery pack voltage, overcharge protection does not have a part, battery cycle life, because a single battery is discharged, causing battery pack failure . Through the test of the actual battery three-electrode system, the relationship of the negative electrode potential change at the end of the discharge is obtained. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: Comparison of the advantages and disadvantages of fuel power batteries and lithium batteries