Features MAIN FUNCTION: This MPPT solar charger allows you to transfer the power from solar panels or other photovoltaic devices to rechargeable batteries. 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. 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. MULTI FUNCTIONS: The constant current charging current is set by an external resistor; Trickle charging of deep discharge batteries; Automatic charging function. CHARGING DETAILS: Charging current up to 2A; PWM switching frequency 300KHz; Constant voltage charging voltage 4.2V ± 1%. Specification: Item Type: Solar Charger Board  Material: PCB Input Voltage: 9V Features: Output Voltage: Nominal 3.7V full stop voltage 4.2V lithium battery single series lithium battery charging management Interface: 2Pin PH2.0 JST Maximum power point tracking function of solar panels Complete charging management for a single lithium battery Charging current up to 2A PWM Switching Frequency: 300KHz Constant Voltage Charging Voltage: 4.2V ± 1% The constant current charging current is set by an external resistor Trickle charging of deeply discharged batteries Automatic recharge function Indication of charging status and charging end status Package List: 1 x Solar Panel Module  2 x Connect Cable  Package List 1 x Solar Panel Module 2 x Connect Cable