Battery Management System Controls 101 Design Guidelines and Best Practices The BMS is the central control unit of the battery pack There are two major types of BMS typologies: Centralized and Distributed A centralized BMS has all of the hardware located in one spot in the battery pack A distributed BMS has a single master controller and then a series of slave boards attached to the cell modules Two major types of cell balancing are passive and active balancing Passive balancing uses resistors to convert excess energy into waste heat Active balancing transfers energy from a cell at a higher SOC to a cell at a lower SOC