In a solar power supply system, the controller (also known as a charging controller or charging regulator) is responsible for managing the transmission of electrical energy between the solar cell array and the battery to protect the battery from damage caused by overcharging or overdischarging. Choosing the appropriate controller is crucial for system performance and lifespan. The following are the key factors to consider when choosing a solar controller:

Type: There are currently two main types of controllers on the market, namely pulse width modulation (PWM) controllers and maximum power point tracking (MPPT) controllers. PWM controllers have lower costs and are suitable for small systems; MPPT controllers have superior energy conversion efficiency and are suitable for large systems or situations with poor environmental conditions.

System voltage: When selecting a controller, ensure that the voltage it supports matches the voltage of the solar panel and battery. Common system voltages include 12V, 24V, and 48V.  

Maximum input current: The maximum input current of the controller should be greater than or equal to the output current of the solar panel under maximum lighting conditions. Usually, the maximum input current required can be determined by multiplying the short-circuit current (Isc) of the solar panel by 1.25.

Maximum power output: Select the appropriate controller based on the maximum power output (Pmax) of the solar panel. Ensure that the maximum power output of the controller is greater than or equal to the maximum power output of the solar panel.

Configuration and Scalability: Choose a controller with flexible configuration and scalability to adjust and expand according to system requirements.  

Protection function: Choose a controller with comprehensive protection functions, such as overcharge protection, over discharge protection, overload protection, short circuit protection, and reverse polarity protection, to ensure the safe and stable operation of the system.

Display and communication functions: Modern controllers typically have display and communication functions, such as LED or LCD displays, remote communication, and data recording. These features help monitor and manage the operation of the system.

Price: Choose a suitable controller based on budget while meeting system requirements and performance requirements.

In short, when choosing a controller for a solar power supply system, multiple aspects such as performance, compatibility, protection functions, and scalability should be fully considered to ensure stable operation and optimal performance of the system.