“A 3V to 20V portable rechargeable power supply from off-the-shelf components. Powered by a single 18650 battery.
There are a number of Portable Power Supplies that makers have built around the cheap J5019 Adjustable Step Up module. Here are just a couple of them:
Portable Power Supply (18650 Battery) by alextrim
Portable Variable Power Supply by lonesoulsurfer
I decided to combine these two builds and design and 3D print a case for it.”