Solar cell module will generate photovoltaic voltage and photovoltaic current under the irradiation of sunlight, and it is the power generation device of photovoltaic system. It outputs direct current, which is set by the charge-discharge controller to charge the battery; The process of charging is the process of storing energy.

Battery is the energy storage device of photovoltaic system. During the day, solar energy is converted into electrical energy by photovoltaic cells, and electrical energy is converted into chemical energy by charging storage batteries. At night, the solar cell stops generating and charging, and the storage battery begins to discharge the load, and the chemical energy is converted into electric energy to supply the light source to work. Therefore, a complete photovoltaic system has a series of energy conversion in one day and night: solar radiation energy → electric energy → electrochemical energy → electric energy → electro-optical lighting.

Intelligent charge-discharge controller plays an extremely important role in the energy conversion of photovoltaic system. The controller has advanced charging control, discharging control and a series of protection functions such as overcharge protection, overdischarge protection and overload protection. The performance of photovoltaic system has a great relationship with the controller. It can be said that the charge and discharge controller is the heart of photovoltaic system. At present, all the charge and discharge controllers used in photovoltaic system closely monitor the charge and discharge process, especially the charging process, which greatly improves the reliability of the system.