Fenix ARB-L18-3400

Fenix, well known for its powerful flashlights, also makes its own range of rechargeable 18650 cells. The ARB-L18-3400 is the most classic version in that lineup: a protected button-top design with no built-in USB charging electronics, aimed at users who already own a charger dedicated to lithium-ion cells.

With a 3400mAh capacity at 3.6V (around 12.24Wh), it provides comfortable runtime for demanding flashlights and headlamps, cameras, or any other gear using 18650 cells. At roughly 69mm long, it stays close to the standard cell length (65mm) and is noticeably more compact than the USB version in the range, which keeps it compatible with the widest possible range of flashlights and battery holders, including some models that are fussier about cell length. That makes it a natural match for Fenix's own high-output torches, as well as third-party lights, headlamps and bike lights built around the 18650 format.

This battery includes a protection circuit built into the positive terminal, guarding against short circuits, overcharging, deep discharge and overheating, backed up by a pressure relief vent for added safety. Fenix rates it for around 500 charge cycles, retaining about 75% of its capacity at that point, a solid figure for a protected cell.

Buying an 18650 straight from an authorised Fenix retailer rather than a generic marketplace listing avoids the real risk, common with this format, of ending up with a reconditioned or overrated cell: the ARB-L18-3400 is covered by Fenix's limited lifetime warranty. A compatible lithium-ion charger is still required (1A recommended, 2A maximum), never a standard NiMH battery charger. For anyone who already owns one, this is a dependable, well-protected 18650 in the most universally compatible size Fenix makes, and a sensible pick for a spare cell to keep in a bag or glovebox.