DROK&reg; DC-DC Voltage Regulator Buck Converter 4-38V to 1.25-36V 5V/12V Power Supply Module 5A Red light is on in constant current status and off in constant voltage status. Blue light is on when charging and off when full-charging Work as high-power LED constant current driver module Work as buck converter module with over-current protection Charger of batteries(eg. nickel-cadimium or nickel-metal hydride battery, lithium batteries)