This unit was a by-product of another project. I needed a small power supply on the field that can give 12VDC. I did not want to carry a huge benchtop power supply so I made a battery powered packet size power supply. I used one 18650 Li-Ion battery, which has the best energy density feature among available batteries on the market. I used a step-up boost converter module, which changes the 3.7V of the battery to a higher voltage. The output Voltage is adjustable in the range of 5 V24VDC. There is a small potentiometer on the module for this purpose. The switched-mode power supply has a very good efficiency (approximately 90%). Without any cooling, it was capable of producing 600 mA at 12VDC (7.2W) (only for a short time). I put a USB connector as an output of the unit because this was the easiest way for me to connect to different loads. The output voltage and current are displayed with a USB tester. After the output Voltage is set, there is no need for any display (it consumes some energy, shortening the lifetime of the battery), so I just remove the USB tester, before using the unit for a longer time. I created a video with step by step instruction to show how to build this useful tool, and I made some test, to see the performance of the unit.
It is very simple to build the power supply, for someone who likes soldering, creating this unit will take 10 minutes.”