Power bank with USB output to charge cellphones etc.

thingiverse

Here's a design for a rechargeable power bank: print a custom housing to fit one or more 4.2V lithium polymer or 18650 laptop batteries. This enclosure comes with printable components, including buttons and LED light guides. For charging, plug in a USB connector, and output up to five volts using two standard ports. This project uses the Power Stream PST-MP150 board; it's available for purchase at powerstream.com. Instructions: Build this portable power source by printing the included housing pieces in black PLA - ABS should also work well. Insert LED light guides into their holes with a small drop of super glue, acetone, or MEK. Assemble the entire case by snapping its parts together and secure it using ABS cement or super glue for added strength.