1. BMU (Battery Management Unit): This is the part of the BMS responsible for the management and control of individual battery cells or battery modules. The BMU monitors the voltage, current, temperature, and cell balance of each battery cell and performs functions such as cell voltage monitoring, cell balancing, charge allocation, and overcharge and over-discharge protection.

2. BCU (Battery Control Unit): The BCU is the part of the BMS responsible for controlling and monitoring the behavior of the entire battery system. It communicates with the BMUs and coordinates battery charging and discharging, monitors overall battery status, implements security algorithms, and can also facilitate communication with other system components.

3. BAU (Battery Auxiliary Unit): The BAU is an additional module within the BMS that provides additional functionality to improve the performance and safety of the battery system. This may include temperature control systems, cooling, heating, or insulation of the battery, monitoring non-critical parameters such as environmental conditions, and other additional functions such as a communication interface to the smart grid controller.