The BMS is the brain of the battery pack in a BESS, responsible for monitoring and protecting individual cells to prevent damage and extend lifespan. It measures critical parameters such as voltage, current, and temperature, while calculating the State of Charge (SOC) and State of. Battery Energy Storage Systems (BESS) are pivotal in modern energy landscapes, enabling the storage and dispatch of electricity from renewable sources like solar and wind. As global demand for sustainable energy rises, understanding the key subsystems within BESS becomes crucial. Among the key innovations, the 3S Integration—combining Energy Management System (EMS), Battery Management System (BMS), and Power Conversion. A Battery Management System (BMS) is the backbone of any modern energy storage system (ESS), especially those using lithium-ion batteries. Without a proper BMS, batteries may experience overcharging. The widespread adoption of electric vehicles (EVs) and large-scale energy storage has necessitated advancements in battery management systems (BMSs) so that the complex dynamics of batteries under various operational conditions are optimised for their efficiency, safety, and reliability.