Xtar 21700 5000mAh

The Xtar 21700 5000mAh (INR21700-50E cell) is a rechargeable lithium-ion battery in the 21700 format, larger than the classic 18650 (21mm diameter versus 18mm), which lets it pack more capacity into a footprint that stays compact. Unlike a bare cell reserved for experienced users, this Xtar version includes a protection circuit (PCB) that makes it far more approachable for everyday use.

It offers a nominal capacity of 5000mAh (around 4900mAh minimum guaranteed) at a nominal voltage of 3.6V, and can deliver up to 10A continuous discharge. Enough to power demanding torches and headlamps, custom battery packs for e-bikes and e-scooters, and power-hungry portable tools.

The built-in protection circuit constantly monitors voltage and cuts power in case of overcharge, over-discharge or short-circuit, a safeguard completely absent from a bare 21700 cell as sometimes found on the market. It's a real argument for anyone who doesn't want to manage a lithium cell's voltage limits themselves, at the cost of a slightly longer Button Top format: 74.5mm versus 70mm for a standard bare 21700, worth checking on devices with tight tolerances.

Xtar rates it for solid long-term durability, with several hundred charge/discharge cycles before any noticeable capacity drop, and an impact-resistant design. Sold as a single unit, this cell charges with an external charger suited to protected 21700 cells (such as an Xtar VC4 or equivalent), never with a standard NiMH charger.

For anyone already running 21700-format devices without wanting to learn the finer points of bare cells, the Xtar 21700 5000mAh ticks every box: high capacity, built-in safety, and the reliability of a brand that has specialised in lithium cells and chargers for over a decade.