Fenix ARB-L18-3400
(6 reviews)
A straightforward 3400mAh 18650 battery from a trusted flashlight brand: button-top design, built-in short circuit protection, and 500 rated charge cycles.
Characteristics
- Capacity / Voltage: 3400 mAh / 3.6V
- Rechargeable: Yes, button-top Lithium-ion
- Pack size: Sold individually
- Short circuit protection, 500 cycles, Fenix warranty
Detailed overview: Fenix ARB-L18-3400 rechargeable 18650 battery
Fenix is best known for its rugged, high-output flashlights, but the brand also sells its own 18650 rechargeable cells directly through its official US store, and the ARB-L18-3400 is the straightforward, basic entry in that lineup. It gives flashlight owners a genuine, well-documented cell instead of gambling on an unbranded battery from a general marketplace listing.
Its 3400mAh capacity is a solid middle-of-the-road figure for the 18650 format, enough to power headlamps, EDC flashlights and other demanding gear through a full outing. The cell uses a button-top design, which Fenix notes was chosen specifically to fit a wider range of flashlight brands and battery holders than older flat-top cells, so compatibility issues are less likely.
Safety is built in from the start: the battery includes protection against short circuits along with several additional protection layers, and it is rated for about 500 charge cycles, a typical lifespan for a protected 18650 with regular use. It is priced and shipped as a single cell, and it is backed by the Fenix Limited Lifetime Warranty.
One practical note: because lithium-ion batteries are classified as dangerous goods under US shipping rules, loose cells like this one typically ship by ground only, and delivery can take noticeably longer than a standard package. It is a small tradeoff for a cell you can trust is genuine, which matters a great deal in a format that sees frequent counterfeiting elsewhere online.
Our tester's review: Pierre Freysinger
Loose 18650 cells are a minefield online, with counterfeit and relabeled batteries turning up constantly on general marketplaces, so we wanted a source we could vouch for. Buying directly from Fenix removes that guesswork: what you get matches exactly what is printed on the wrapper, backed by the same company that builds the flashlight it likely ends up in. In use, the button-top design is the detail that matters most day to day, since it fits noticeably more flashlight brands and battery holders than a flat-top cell, without needing an adapter. The 3400mAh capacity lands in a sensible middle ground, not the biggest number Fenix sells, but plenty for most headlamps and everyday carry lights, and the 500-cycle rating held up fine across months of regular use. A few reviewers mention a cell arriving at partial charge, which is normal for a freshly shipped lithium cell rather than a defect. Shipping also takes longer than typical, since loose lithium batteries move by ground only. For a reliable, honestly labeled 18650 over the cheapest marketplace option, this is money well spent.
Frequently asked questions: Fenix ARB-L18-3400 rechargeable 18650 battery
The 3400 is a basic button-top cell with no onboard charging port, while the 3500U adds a built-in USB charging port and a slightly higher capacity for a higher price. Choose the 3400 if you already have a dedicated 18650 charger and want the simpler, less expensive option.
Generally yes. Fenix designed this button-top format specifically to fit a wider range of flashlight brands and battery holders. Still, check your specific flashlight's manual if you are unsure, since a small number of lights are built only for flat-top cells.
Fenix rates the ARB-L18-3400 for about 500 charge cycles with a suitable 18650 charger, which is standard for a protected lithium-ion cell of this type.
Loose 18650 cells are a common target for counterfeiting and relabeling on general marketplaces. Buying directly from Fenix's official store guarantees a genuine cell backed by the manufacturer's own warranty and customer service.
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Published on 02/09/2026