A Fenix ARB-L18-3500U rechargeable lithium-ion battery with built-in USB port, predominantly black with orange accents, labeled with RoHS and CE certification marks.
Fenix ARB-L18-3500U rechargeable battery with detail text
Fenix ARB-L18-3500U rechargeable battery plugged in via micro-usb port
Fenix ARB-L18-3500U rechargeable battery protection features
Fenix ARB-L18-3500U rechargeable battery with short circuit protection
Fenix ARB-L18-3500U rechargeable battery pressure relief vent
Text explaining the 500 charge cycles of the Fenix ARB-L18-3500U rechargeable battery
Fenix ARB-L18-3500U rechargeable battery technical parameters chart
A pair of Fenix ARB-L18-3500U rechargeable batteries

Fenix ARB-L18-3500U USB Rechargeable Li-ion 18650 Battery

Regular price$24.95
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The Fenix ARB‑L18‑3500 is a high-capacity 18650 rechargeable Li‑ion battery, offering 3,500 mAh within a standard size that fits most high-performance flashlights. Built for safety and durability, it includes a button-top design, integrated protection circuitry against overcharge, over-discharge, short-circuit, and overheating, plus pressure relief vents to prevent buildup and reduce risk of swelling or rupture. A robust steel-infused anode structure further improves impact resistance and electrical safety. This cell is rated for up to 500 charge cycles, maintaining around 75% capacity afterward, and carries Fenix’s 12-month warranty.

Key Specifications:

  • Capacity & Voltage: 3,500 mAh, 3.6 V
  • Protection Features: Overcharge, over-discharge, short-circuit, overheat protection; pressure relief vents; reinforced steel anode
  • Design: Button-top, compatible with Fenix and other 18650 devices
  • Durability: Up to 500 charge cycles, retains ~75% capacity over time
  • Size & Weight: Approx. 69 mm length × 18.6 mm diameter; ~50 g
  • Warranty: 12-month manufacturer’s warranty

A reliable, long-lasting, and safe power solution—perfect for tactical flashlights, headlamps, lanterns, and high-drain devices.

Note: This item is packaged and priced as one battery. 

Shipping Note: Lithium ion batteries are considered "dangerous goods" per US transportation regulations and can often only be transported via ground shipment. Orders containing loose batteries will typically take much longer than predicted to be delivered. Delivery times of 14+ days are not uncommon.  

  • Fenix ARB-L18-3500U mAh USB Rechargeable 18650 Battery
  • Micro USB charging port lets you charge the battery directly
  • Button-Top Design Protection circuit built in the anode with a riveted steel hat.
  • Riveted steel shell eliminates the risk of short circuit caused by collision and impact.
  • Pressure Relief Vent: Expels waste gas generated by internal short circuit. Expelling waste gas prevents a cell from inflating or exploding.
  • Three Sets of Over-Heat Protection: Overcharge protection, Over-discharge protection, Short-circuit protection, and overheating protection
  • 500 Charge Cycles: A properly maintained ARBL18 battery is designed to retain up to 75% of its original capacity at 500 full charge and discharge cycles.
  • **USB Cable NOT Included**
  • Fenix ARB-L18-3500U Rechargeable 3500mAh 18650 battery