The Research On The Intelligent Controlling Strategy For Lithium Batteries

With the characters of large capacity and long life,lithium batteries have become the first chosen power source for automobiles and portable mobile devices.As the core ensuring the batteries working safely and increasing their service life,Battery Managing System(BMS)is also a key technical bottleneck in their producing process.After introducing the structural characteristics of lithium batteries,some factors leading to the inconsistent performance of lithium batteries were analyzed,then an intelligent BMS based on fuzzy control strategy theory was presented.It can mainly be divided into two major parts.One is the establishment of a mathematical model and simulation analysis.In this part,the nonlinear variation of the lithium battery voltage was simulated on the MATLAB/Simulink module by using of the second-order RC model,and the voltage curve agreed with the results got from actual measurement.Then,the equalizing topology of the lithium battery pack is designed,and the working principle of the active equalizing circuit was analyzed in detail,and the effectiveness of the equalization circuit is tested in the discharge state,which proves that the equalization circuit can effectively reduce the voltage range of the battery pack.At last,the intelligent fuzzy controller based on fuzzy control strategy theory was presented,the voltage changing curves under the controller and without the controller were both depicted on the simulation platform,and the expected functions and efficiency were verified by them.The other part is the design of the hardware system,setting up of the platform and testing.The whole system includes the detection part,fuzzy controller,and equalization part.The main controlling chip is STM32F103C8T6,the voltage detection chip for single lithium battery is ADS1110,the current monitoring chip is ACS712,the temperature detection chip is DS18B20,and the displaying unit is TFT(Thin Film Transistor,thin-film field-effect)LCD liquid crystal displayer.In terms of software,modular program designing method is adopted.The low power consumption and anti-interference design of hardware and software are carried out according to the system’s working requirements to ensure the reliability and stability of the system operation.The main results are: the lithium battery management system designed in this paper can accurately monitor the parameters and display them through the TFTLCD liquid crystal display to meet the needs of a real-time monitoring system.With the support of a fuzzy control algorithm and topological equalization circuit,BMS has the advantages of fast equalization speed and low energy loss,which reduces the voltage polarity to a certain extent,effectively reduces the inconsistency of the lithium battery pack,guarantees the operation of lithium battery pack in the safe temperature range,and improves the utilization of battery pack using capacity and energy.