Mini DC-DC Boost Converter, 0.9V-5V to 5V, 600mA USB Output

A single AA or AAA battery starts around 1.5V and keeps dropping as it discharges, well below the steady 5V most USB-powered gadgets expect, which is exactly the gap this tiny boost module bridges. It can pull a usable 5V output starting from as little as 0.9V input, meaning it keeps delivering power from a battery that a typical device would already consider dead, making it a popular building block for scavenged-power projects, emergency phone chargers, and joule-thief style battery-life-extending builds. Its small size and USB-style output make it easy to tuck into a compact enclosure alongside a single battery holder.