Design And Realization Of Internal Resistance Detection Device For Battery Pack

With the widespread application of battery packs as a backup power supply in power supply systems in all walks of life,the health of battery packs has a close influence on the safe operation and economic benefits of power supply systems in all walks of life.In order to ensure the reliability and stability of battery pack power supply,the detection technology for each characteristic parameter of the battery pack came into being.In recent years,the correlation between battery internal resistance and battery health has been recognized by more and more people.Therefore,the health status of the battery can be judged by the size of the internal resistance,and achieving higher-precision measurement at a lower cost is the key to the research on the internal resistance detection of the battery pack.In this paper,after comparing the advantages and disadvantages of the existing internal resistance detection methods,the AC injection method is selected as the internal resistance detection method in this paper.The traditional AC injection method is to inject a constant current AC excitation signal into the battery,and collect the voltage response signal generated at both ends of the battery.The internal resistance of the battery is calculated by Ohm’s law,which has the advantages of short measurement period and less wear on the battery.However,because the battery is equivalent to the complex impedance of resistance and capacitance,the voltage response signal generated at both ends of the battery will have a certain phase shift,and the measurement accuracy is not high.At the same time,because the internal resistance of the battery is very small,the voltage response signal is very small,and it is very susceptible to noise.Aiming at the deficiencies of the AC injection method,it was improved,and a battery pack internal resistance detection device with higher measurement accuracy,stronger anti-interference ability and lower cost was designed.The main research contents are as follows:(1)In the detection circuit,the reference resistance is designed to simplify the calculation process of the traditional AC injection method to detect the internal resistance by calculating the proportional coefficient,it eliminates the need to measure other parameters in the detection circuit,and does not need to consider the influence of the phase shift,which improves the measurement accuracy in principle.(2)The phase-locked amplification technology is used to effectively extract the weak voltage response signals at both ends of the battery,and the measurement accuracy is further improved.The model is built on the Simulink platform,and the anti-interference ability of the phase-locked amplification module is verified through simulation experiments.(3)Design a standard sine wave array that stores the form of digital signals,and read the array through the DAC of the micro-control unit,cooperate with the timer and DMA to generate the required AC sine wave excitation signal instead of the waveform generator,reduce the introduction of external noise and save costs.(4)On the basis of the hardware design scheme of the battery pack internal resistance detection device,this article combines the circuit principle of each module and the pin function of each chip on the Altium Designer platform to complete the design of the circuit schematic diagram as required,complete the PCB layout design and complete the soldering of the circuit board.The main program of the internal resistance detection device of the battery pack and the design of each module program are completed on the IAR for ARM program development platform.After debugging and actual measurement experiments,it is proved that this device can accurately measure the internal resistance of the battery,and the measurement accuracy can reach 1.8%.