Review on JacobsParts XL4015 5A DC-DC Buck Step Down Voltage Constant Current Converter Module with LED Voltmeter, USB Output, and Adjustable Power Regulator Board by Brian Cox

I use this to drop the voltage from 12v to 8v for supercapacitors that draw virtually unlimited current while charging and destroy unprotected power supplies. Short circuit protection can also be useful in other applications. When shipped the outputs are set to maximum and the potentiometers turned fully clockwise, so expect a few counter-clockwise turns before the output voltage and current decrease. The button to the left of the LED digits toggles the LEDs on and off (but not power). The button to the right of the LED digits switches the display from voltage to power, from current to cycle. The input and output voltage values are distinguished by separate small LEDs that light up to the left or right of the numbers. .