FENIX ARB-L18-4000 18650 4000 mAh USB-C Battery

The ARB-L18-4000 is the Fenix rechargeable 18650 cell with 4000 mAh capacity and built-in direct USB-C charging. At 18.75x69.2 mm, it powers high-performance Fenix torches, headlamps and lanterns, and is compatible with airsoft and outdoor devices that accept protected 18650 cells.

At 4000 mAh, this cell offers noticeably longer runtime than the 3400–3500 mAh 18650 cells common on the market, with no change in size. A maximum discharge current of 7 A handles the peak draw of high-output torches without voltage drop. USB-C charging accepts up to 4 A, cutting recharge times compared to cells that rely on micro-USB or an external charger. The trade-off is in the dimensions: the 18.75 mm diameter, slightly above the standard, prevents fitting in some older housings such as the PD31, TK11 and TK21 — worth checking before purchase.

Key points

• 4000 mAh capacity in 18650 format: more runtime without changing your device
• USB-C charging up to 4 A directly on the cell, no separate charger needed
• Discharge current up to 7 A: handles peak draws from high-output torches
• Built-in electronic protection against overcharge, over-discharge, short circuit and overcurrent
• Nominal voltage 3.6 V, compatible with Fenix devices that accept protected 18650 cells