Battery Energy Storage System (BESS) is a large-scale battery system that is connected to the power grid and used to store electricity and energy. It consists of the following parts:

A single cell, as part of a battery system, can convert chemical energy into electrical energy.

A battery module composed of multiple battery cells in series or parallel. The battery module also includes a module battery management system (MBMS) for monitoring the operation of the battery cells.

A battery cluster is used to carry multiple series modules and battery protection units (BPUs) - also known as a battery cluster controller. The battery protection unit includes a battery cluster battery management system (BMS), which can be used to monitor the voltage, temperature, and charging status of the battery. This unit can also be used to adjust the charging and discharging cycles of the battery.

The energy storage container can carry multiple parallel battery clusters and may also be equipped with other additional components for easy management or control of the container's internal environment.

The direct current (DC) generated by the battery is processed by the power conversion system (PCS) or bidirectional inverter, converted into alternating current (AC), and transmitted to the power grid (facility or end user). If necessary, the system can also extract electricity from the power grid to charge the battery.

BESS may also include some safety systems, such as fire control systems, smoke detectors, and temperature control systems, and even cooling, heating, ventilation, and air conditioning systems. The specific systems included will depend on the need to maintain the safe and efficient operation of BESS.