1、MAIN FUNCTION: This MPPT solar charger allows you to transfer the power from solar panels or other photovoltaic devices to rechargeable batteries. 2、EASY TO USE: Insert the solar panel into one side of the solar charger, and then insert the battery into the other side to start charging. 3、STABLE CHARGING: With the maximum power point tracking function of solar panels, the solar charger board provides complete charging management for a single lithium battery. 4、MULTI FUNCTIONS: The constant current charging current is set by an external resistor; Trickle charging of deep discharge batteries; Automatic charging function. 5、CHARGING DETAILS: Charging current up to 2A; PWM switching frequency 300KHz; Constant voltage charging voltage 4.2V ± 1%.