Development Of Online State Detection And Equalization Control Device For Series Battery Pack

Batteries have been widely used in uninterruptible power supply,electric vehicles and other fields because of their ecnomical efficiency.Due to the gradually improvement of battery manufacturing process and technology,the lifepan of the battery is significantly improved,and failure due to its own quality is rare.Overcharging and overdischarging in the use of the batteries will cause the plate active substance to fall off and the grid to corrode,which seriously affects the lifespan of batteries.The density of electrolyte,temperature and ventilation conditions,self-discharge degree and charging and discharging modes of individual batteries will be slightly different.After multiple charging and discharging cycles,the difference will gradually increase,which will lead to the inconsistency of voltage,internal resistance,capacity and other parameters of the battery pack,which inevitably lead to overcharged and overdischarged problems.Therefore,it is important to study the state of charge and equalizing control of battery packs.State of charge(SOC)estimation and the equalization control are combined in this paper,which makes the system not only have the function of state of charge estimation,but also play the role of equalizing charging,It avoids the problem of unbalanced capacity,overcharged and overdischarged,effectively prolongs the lifespan of batteries.On the basis of analyzing and summarizing the research in related fields,the detection methods of parameters such as terminal voltage,current,internal resistance and temperature were selected.The voltage of the two terminals was selected by AQW214 photoelectric relay,and the current was detected by Hall current sensor.The injection method detects the internal resistance,and the DS18B20 temperature sensor detects the temperature.Based on above,the working principle block diagram of each part is designed.Based on the research of battery pack equalization variable,equalization control strategy and equalization circuit,the switch-type shunt resistor equalization circuit is realized based on S-8261 chip design.The S-8261 model and the equalization model of charge-discharge is implemented under the Simulink simulation platform to simulate the voltage and SOC changes during the charging and discharging process of the lead-acid battery pack.According to the above simulation results of charging-discharging process,the problem of equalization in the charging process of lead-acid battery pack is solved based on the switching shunt resistor equalization circuit designed by the overcharged and overdischarged protection mechanism of S-8261 battery protection chip.Damage of overcharged and overdischarged to battery lifespan is successfully avoided.On the basis of theoretical analysis and simulation research,the power supply module circuit,single battery terminal voltage acquisition circuit,current acquisition circuit,temperature acquisition circuit,internal resistance acquisition circuit,communication and storage circuit,equalization charging control circuit,etc are successfully designed and implemented.The function of soc estimation and equalization control is designed and implemented.Finally,the system software workflow is designed.