DIY Mini Power Bank Case – 21700 Battery Excluded

Build a compact portable charging accessory with this DIY mini power bank case. It is an ABS enclosure intended for a separately supplied compatible 21700-format battery. The battery is not included, so the case needs a suitable cell and assembly before it can serve as a power source.

The case measures 82 mm long and weighs 32 g without the battery. Its rounded black body keeps the charging assembly small enough for a pouch or everyday carry compartment. The finished weight and available reserve power depend on the cell installed.

A USB-C socket is part of the connection layout, alongside a direct phone connector with a protective cap. The cap covers the protruding plug between uses, helping keep that part of the case contained for carrying. A row of indicator lights on the front provides a visible status reference for the assembled accessory.

This format is useful for someone putting together a small charger around a suitable battery rather than buying a sealed, preassembled power bank. The 21700 designation describes the required cell format; it is not the battery capacity. Electrical suitability also matters, since physical size alone does not establish compatibility with the case's charging components.

The key items to plan around are the compatible cell, the connector fitted to the case and the device it will charge. The enclosure provides the compact housing and connection arrangement, while the separately supplied battery determines the energy reserve.