Master-Slave BMS Architecture with CAN-bus for Inter-Cell Communication

In this paper, a Battery Management System (BMS) is designed and implemented to enable fast balancing of a 4S1P battery pack, which contains four Lithium Iron Phosphate (LiFePO4) cells connected in series. The proposed Master-Slave architecture supposes a single Master node and four Slave nodes which communicate using a Controller Area Network (CAN). The Master node receives the measured parameters (voltage, temperature, balancing state) from all Slave nodes, detects if the battery pack is charged, compares the cells voltages, takes the decision which cell to be balanced, and transmits the balancing command to a specific Slave node. Also, the Master node has the role of protection for undervoltage, overvoltage, and overtemperature, by disabling the battery charger or the load. Each Slave node acquires cell data and enables passive balancing of that cell using high power resistors. The measured parameters and the operating states of the BMS can be also transmitted through the CAN-bus to other Electronic Control Units (ECUs), for example an LCD display.