Description
Simplify your power routine with the genuine Fenix ARB-L21-4900U, a 21700 battery featuring a built-in USB-C charging port. No dedicated charger needed—just plug any USB-C cable directly into the battery and recharge from a wall adapter, power bank, car charger, or laptop. Built around a premium 4900mAh cell core, it delivers near-flagship runtime with integrated overcharge, over-discharge, and short-circuit protection. The button top design ensures broad compatibility with Fenix and most other 21700 flashlights. With a convenient LED charging indicator and excellent cycle life, the ARB-L21-4900U keeps your gear ready to go wherever a USB-C cable is available.
Key Features
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Built-in USB-C Charging Port – Recharge directly from any standard USB-C power source. No external 21700 charger required. USB-C offers reversible plugging and improved durability over older connector types.
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4900mAh High Capacity – Provides near-flagship runtime for demanding LED flashlights, headlamps, and outdoor gear. Only slightly less than 5000mAh cells at a more accessible value.
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Integrated Safety Protection – Built-in circuit guards against overcharge (4.2V), over-discharge (2.5V), short circuit, and overcurrent (8A limit), ensuring safe operation in any compatible device.
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Button Top Design – Raised positive terminal ensures reliable electrical contact in Fenix and most other 21700 flashlights and devices.
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LED Charging Indicator – Built-in LED shows charging status at a glance: red means charging, green means fully charged and ready to use.
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Genuine Fenix Quality – Manufactured to strict standards with a premium 21700 cell core and advanced protection circuitry for long service life and consistent, safe performance.
Parameters
Applications
Recommended For
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High-Output 21700 LED Flashlights: Perfect for Fenix and other 21700-powered flashlights. The 4900mAh capacity provides excellent runtime, and USB-C allows convenient recharging from any modern USB source—no separate charger to carry.
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Headlamps for Outdoor & Professional Use: Ideal for camping, running, caving, and industrial work. The protection circuit prevents over-discharge damage, and USB-C enables easy field recharging from a power bank.
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Camping Lanterns & Emergency Lights: Any USB-C power source becomes your charger. The 4900mAh capacity ensures lights stay on through extended power outages.
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Bicycle Lights: Consistent output for night riding. Recharge between rides using the same USB-C cable you use for your phone or bike computer.
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Smart Doorbells & Wireless Security Cameras (21700 Compatible): Extended runtime between charges. USB-C port allows easy periodic recharging without removing the battery from the mounting bracket.
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Portable Fans & Travel Gadgets: Minimize accessories—one USB-C cable charges your phone and your spare batteries.
Not Recommended For
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High-Power Vaping / Mechanical Mods: These require 15–35A unprotected cells. The 8A protection limit is insufficient for sub-ohm applications.
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Cordless Power Tools: Drills, saws, and impact drivers demand 20–40A continuous current, far beyond this battery's 8A protection limit.
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RC Cars, Drones & High-Drain Models: These require 20–30A+ continuous current. This battery will not function and may trigger protection.
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18650-Only Devices: This is a 21700 cell (21mm diameter) and will not physically fit in 18650 battery compartments.
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Ultra-Compact Flashlights with Tight Battery Tubes: This battery measures approximately 75.5mm in length due to the USB-C port and protection circuit. Some flashlights with very tight battery compartments may not close fully. Always verify fit before ordering.
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Multi-Cell Series Packs: Individual protection boards and USB modules may conflict. Use matched unprotected cells with an external BMS instead.
FAQ
Q: How do I charge this battery? Is a special charger required?
A: No special charger needed. Simply connect a standard USB-C cable to the port on the battery and plug the other end into any 5V USB power source—a phone charger, power bank, laptop, or car adapter. The built-in LED glows red during charging and turns green when fully charged. A full charge takes several hours depending on the power source.
Q: Will this fit my 21700 flashlight?
A: It fits most 21700 flashlights that accept button top cells. Due to the integrated USB-C charging port and protection circuit, this battery is approximately 75.5mm long—about 5–6mm longer than a standard unprotected 21700 (70mm). Most 21700 flashlights with spring-loaded contacts can accommodate this extra length, but some ultra-compact models may not close fully. Please measure your device's battery tube or check the manufacturer's specifications before ordering.
Q: Can I also charge this battery in a regular 21700 charger?
A: Yes. The ARB-L21-4900U can be charged either through its built-in USB-C port or in any standard 21700 Li-ion charger that accepts button top cells. Both methods are safe and fully supported.
Q: Is this battery suitable for vaping or power tools?
A: No. Vaping devices and power tools require high continuous currents (typically 15–40A). The ARB-L21-4900U's protection circuit limits output to approximately 8A. Using it in such devices will cause the protection to cut off power or may damage the battery. For these applications, use dedicated high-drain unprotected cells.
Q: How does the 4900mAh compare to the 5000mAh version?
A: The ARB-L21-4900U provides 4900mAh, which is only about 2% less capacity than a 5000mAh cell. In real-world use, the difference is negligible—perhaps 5–10 minutes less runtime on high mode. Many users find the USB-C convenience far outweighs this tiny capacity difference.
Q: How should I store this battery long-term?
A: Store at approximately 3.6–3.7V (40–50% charge) in a cool, dry place using a non-conductive battery case. Avoid storing fully charged or fully discharged for extended periods, as this accelerates capacity loss. The built-in USB-C port makes it easy to top up before use after storage.
