Design And Implementation Of BMS For Electric Logistics Vehicles

As people attach importance to environmental protection,the exhaust emissions from traditional logistics vehicles make the problem of environmental pollution become more serious.And the nonrenewable energy of traditional energy also makes the electric logistics vehicle emerge.As a new type of clean energy,lithium battery effectively alleviates environmental pollution and shortage of resources.As the manager of battery pack,lithium battery management system(BMS)has a mission to maintain efficient operation and safety of batteries.The electric logistics vehicle has 36 lithium batteries,whose rated voltage is 3.2V and the rated capacity is 100 Ah.This paper adopts the design of master-slave distribution system.The system is divided into 1 master board and 6 slave boards.The slave board uses the integrated battery management chip called BQ76PL536 to carry out voltage and temperature sampling for the six batteries,and then sends the information to the host for unified processing.The host receives the information from the machine through the CAN bus and makes the system deployment.Then the current acquisition circuit is designed.Using hall sensor sensor,the battery current signal is converted to voltage signal.After the signal conditioning,the analog signal is converted into digital signal through the internal ADC of the host plate,for display and comparison.In addition,the battery balance circuit is designed in the paper.The batteries in the same slave board adopt passive balance,and the active balance is adopted for the battery pack between different slave boards.In the paper,the passive balance is realized by using the passive discharge balance function of BQ76PL536.Start the battery balance when the battery voltage is lower than 50 m V.The active balance adopts the design of anti-shock switch power supply.When the voltage of the battery is higher than 100 m V,the singlechip microcontroller starts PWM wave to move the charge of the high voltage battery to the whole battery pack.In terms of software,in addition to calibrating the fitting error curve to improve the accuracy,the State of Charge(SOC)estimation is carried out with the Ampere-time method and the open-circuit voltage methodFinally,this paper describes the debugging process of this design,and lists the data of debugging results.The data shows that the design can accurately calculate the voltage,current,temperature and SOC status of the battery.The test results were in line with expectations.In addition,the paper also explains the future work and the future prospect.