Here’s the sales literature:
This listing is for a very useful little DC-DC booster circuit. As long as you have 3.4VDC or higher at the input, you can vary the output voltage anywhere from the input voltage up to 34VDC. It is wonderful for slow-charging super capacitors, or powering higher voltage circuits using a couple of AA batteries. I used one of these on my Halloween costume this year. I powered it using a couple super capacitors, and one of these DC-DC boosters. There is a current table in the enclosed images. It tells you how much current can be sources at the output based on the input voltage. I also use one in my variable capacitor charger. You can find these videos on youtube. Search user “patrickikis”.
There is a three-pin screw-type terminal block for safe connection, and a variable resistor that allows for you to change the output voltage for your desired application. The three pints are labeled VOUT/GND/VIN. So, VOUT is your varied output, GND is common ground, and VIN is your input voltage pin; requiring at least 3.4VDC. It is VERY easy to use. DIMENSIONS: 32x34x20mm. It can supply up to 3A of current, but that is not suggested for continuous draw. It is highly suggested that you keep continuous draw under 2A. This bad boy is rated for 15W and has an efficiency of 90%.