Design And Research Of Active Balancing System For Power Lithium Battery Pack

Under the strategic guidance of ’ carbon peak ’ and ’ carbon neutralization ’,new energy electric two-wheeled vehicles have developed rapidly.Power lithium batteries are often used as the power source of electric two-wheeled vehicles because of their high energy density,long cycle life and wide operating temperature range.The single lithium battery has low voltage and small capacity.In order to meet the voltage level and capacity requirements of practical applications,multiple lithium batteries are usually used in series and parallel.Due to the complexity of the production process and the use process,there will be inconsistencies in the single lithium battery,which will reduce the available capacity of the lithium battery pack and have potential safety hazards when used in series,this topic studies this issue.Firstly,aiming at the function of the equalization management system and the inconsistency of the terminal voltage of the single battery of the power lithium battery pack,a centralized active equalization management system scheme is proposed,in which the charger charging current is completely used for the equalization charging of the single battery in the group.The scheme monitors the terminal voltage of the single battery in the group in real time through the front-end chip SH367309 of the battery management system.When the terminal voltage of a single battery reaches the equilibrium opening threshold,the equalization circuit is turned on,and the charging current of the charger is adjusted in real time to adapt to the equalization current,so that the charger directly charges the uncharged single battery in the group through the equalization circuit until the terminal voltage of all single batteries reaches the equilibrium threshold.Secondly,the hardware and software of the system are designed according to the centralized active equalization management system scheme.In the design of hardware circuit,the principle design and device selection of main control unit and peripheral circuit,equalization unit circuit,subordinate management unit circuit and auxiliary unit circuit are carried out.The principle analysis and parameter calculation of isolated buck flyback converter and constant current output synchronous Buck converter in equalization circuit are carried out in detail.In the software design,the main program,data acquisition program,charge and discharge management program,serial communication program,equalization strategy control program,charging switch control program,equalization circuit start and stop program and Buck converter current feedback control algorithm are designed.Finally,an experimental prototype of power lithium battery equalization management system with centralized active equalization function is developed.The prototype was used to conduct a balanced charging and unbalanced charging control experiment on 24 series of15 Ah lithium iron phosphate power battery packs.After the balanced charging was completed,the terminal voltage of the single battery in the group tended to be consistent,And the terminal voltage range is reduced from 147 m V of unbalanced charging to less than15 m VThe.experimental data verify the correctness and feasibility of the proposed centralized active equalization management system.