The Separation And Detection Of DC And AC Signal Research Based On Lithium Battery Internal Resistance Test

Lithium battery internal resistance is an important index to evaluate the lithiumbattery.Its test is of great significance. However, it varies at different state of charge.In order to know the performance of lithium battery in real-time when using lithiumbattery hybrid cars,it needs to realize online detection of lithium battery internalresistance. Applying the method of Electrochemical Impedance Spectroscopy(EIS)for testing internal resistance,it obtains the resistance by calculating the ratio ofvoltage response and current response about lithium battery. But,the voltage responseand current response is admix of DC signal and AC signal and the value of AC signalis small,the separation and detection of them is difficult,which is the key problem forstudying in this thesis.In order to solve this problem,this thesis do such research asfollows:Firstly, introduce the working principle of lithium battery, analys itscharacteristics and set up equivalent model of lithium battery,then put forward themethod of lithium battery internal resistance test.Next,understand the research objectof this thesis based on the method mentioned above.Secondly,design the separation and detection scheme of mixed signal. Apply themethod of inverting superposition of RMS to separate the mixed signal.Apply16bitsexternal AD sampling module to sample DC signal. Apply FPGA sampling module tosample AC signal.Thirdly,Use Multisim simulation platform to build simulation circuit.Thenevaluate the practicability of this scheme.Then, according to the simulation results, built the hardwaretest platform,including mixed signal separation circuit, DC signal and AC signal samplingcircuit,the communication module.Design DC signal sampling program, FPGAsampling program module,programmable amplifier circuit control program and CANcommunication program based on the analysis of system software demand.Finally, evaluate the performance of circuit according to the software andhardware platform.The experimental result shows that this scheme can separate and detect mixed signal effectively.It can ensure the amplitude error and phase error meetthe test requirement.