Design On Battery Management System Of Electric Mini-car

In this paper, the design on a Battery Management System of lead-acid batteries is focused in the basis of an united project, development of an electric mini-car, implemented by NUAA and an EV manufacture.On the basis of the estimation of the advantages and disadvantages of the SOC methods, this paper uses Ampere-Hour integrating method and open circuit voltage method to estimate the SOC of Lead-acid batteries. The open circuit voltage method can estimate the initial SOC, the Ampere-Hour method can estimate the capacity that the battery used during the charge process or the discharge process.Based on the demand of BMS, this paper chooses the PIC18F4580 as the controller of the BMS. The BMS can collect the signals(voltage, current, temperature). This paper uses CAN bus to connect the BMS and the VCU,this paper uses LCD1602 to display the signals.A balancing system of the battery is designed in this paper. Since the electric mini-car is small, and its cost is low, so this paper uses the resistance to consume the energy of the battery which is at a high voltage level, The BMS also detects the temperature of the package of battery. the BMS uses fan and resistance wire to modify the temperature.The software is designed under the MPLAB environment, the software system include timer module, A/D module, CAN module, DS1302 module and DS18B20 module, when the controller begin to work, it will initialize the modules firstly, after initialization it will enter the circulation. It will calculate the SOC value in the circulation.Finally doing experiment by using the battery and BMS. the BMS can collect voltage and current signals in the experiment, it also can estimate the SOC value of the battery pack.