How To Make a Power Bank
Turning a handful of 18650 lithium-ion cells and a charging/boost module into a fully working USB power bank you built yourself.
How a power bank like this goes together
A commercial power bank is really three things: a set of cells for capacity, a small board that manages charging and protects the cells, and a boost circuit that steps the battery voltage up to a steady 5V for USB output. This build uses the same three pieces.
Cells are wired in parallel to add up their capacity while keeping the voltage the same as a single cell, which is what the charging and boost board expects.
Picking the cells
Not every 18650 cell lying around is safe to reuse — cells with damaged wrapping, visible swelling or that won't hold a charge should be set aside rather than used. The video walks through a quick check of the cells before committing to wiring them in.
Why build one instead of buying one
The end result is not necessarily cheaper or better than a shop-bought power bank, but it does teach exactly how they work internally, which makes future battery-based projects far less mysterious.
Want to build this yourself?
The guide covers cell prep, wiring and assembly in the same order as the video, and the downloads page links back to it.