If you want your electronic device, whether it’s a smartphone, Raspberry Pi, or even rechargeable flashlight, to function, you need some sort of power source. Fortunately, more and more manufacturers are standardizing on USB connectors, meaning having a USB source around can be extremely useful.
If you’d like a portable power brick for go-anywhere USB charging, Kim’s 3DIY has a great-looking, 3D-printed gadget with a 12,000–16,000mAh capacity. Inside, it contains four 18650 rechargeable lithium-ion cells wired in parallel, a power management board, and backlit LCD display to tell you how much “juice” you have left.
He goes over how it’s made in the video seen here, and the 3D print files are available on Thingiverse.