A LiFePO4 battery management system for heavy-haul train electrically controlled pneumatic brake system application

In an electrically controlled pneumatic(ECP) brake system, The locomotives of heavy-haul train communicate with cars and supply power for them through the lonworks bus. To guarantee the proper level of uninterrupted power supply for each car, as well as reliable communication between them, a dedicated LiFePO4 battery management system(BMS) is proposed in this paper. Compared with the conventional BMS, several improvements were made. To begin with, a carefully designed impedance network is integrated for reliable communication. Then, a synchronous rectifier buck converter is used for charger design, which can improve the charging efficiency of LiFePO4 battery. Moreover, To avoid overcharging and discharging caused by cell imbalance, a passive cell balancing algorithm is adopted. Finally, an improved battery impendence based coulomb counting method is proposed to report the accurate state of charge(SOC) of battery to locomotives. The experimental results show the battery charger has the peak efficiency of 97.5%, and the SOC estimation and cell balancing have satisfactory performances.