The Study And Design Of Li-ion Battery On-line Monitoring System

With the rapid increment of Li-ion battery requirement,higher requirement is proposed for the industrial production,product quality and on-line monitoring equipments of Li-ion battery.In this paper,a fast,multi-channel,high-accuracy,low-cost new on-line monitoring system for Li-ion battery is designed base on the requirement.This system is composed of the controlling module,monitoring module and supporting software.The controlling module uses TMS320LF2407 DSP processor of TI Company.It can realize the functions of fast computing,processing and displaying of floating-point data.The monitoring module is used to sample the battery parameters under the complex environment.The supporting software which runs on the PC is used to monitor and manage real-time data.During the design , the tendency of intelligent development direction , long-distance management and on-line maintenance is considered for the battery on-line monitoring system.The following contents are mainly studied in this system:Firstly,the principle and method of intelligent sampling and real-time prediction of battery parameters is studied,and the measuring method is proposed.The voltage, current,internal resistance,temperature,SOC and SOH are real-time variables.They need repeatedly sampling,real-time processing and giving an alarm when the situation is abnormal.MSP430F149 chip is used to substitute the labor of human to repeatedly count and off-line forecast the battery capacity.Then,the weak signal on-line detection is realized.A new method which is used to measure the internal resistance is proposed.This method can realize the accurate measure of internal resistance by using PWM and phase lock amplifier technology and compensation technique of benchmark resistance.PWM can modulate the excitation battery of constant-current source and generate weak signal of internal resistance.At the same time,a complex predicting strategy of SOC is established,which can achieve better experimental results.Secondly,the special design is used to improve the system's anti-interference capability and the safety of Li-ion battery.iM4A5-64/32 CPLD is used to substitute the normal chips to improve the integrated level and reduce interference between the wiring and the chips.The common-mode voltage and frequency interference are reduced by using V/I,I/V transformation,dual-band band-pass optical filter and differential amplification circuits.The battery span is improved by using balance power technology . The long range centralized management and on-line maintenance are realized by using RS-485, RS-232 communication.Finally,the hardware measuring of battery parameters,controlling and software algorithm are verified,the reasons caused the errors and inherent errors are analyzed.The experimental results show the performance index of this system can meet the requirement of market,and it has an important project application value.