Fenix ARB-L21-4900U 21700 4900mAh 8A 3.6V USB-C Rechargeable Battery Button Top – Built-in Charging Port for Flashlights & Headlamps
Description
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
| Parameter | Specification |
|---|---|
| Model | Fenix ARB-L21-4900U |
| Battery Type | 21700 Button Top Protected Lithium-Ion with USB-C Charging |
| Typical Capacity | 4900 mAh (0.2C discharge to 2.5V) |
| Minimum Capacity | ~4800 mAh |
| Nominal Voltage | 3.6 V (typical operating 3.7 V) |
| Max Continuous Discharge | 8 A (limited by built-in protection circuit) |
| Protection Functions | Overcharge (4.2V cutoff), Over-discharge (2.5V cutoff), Short Circuit, Overcurrent |
| USB-C Charging Input | USB Type-C port, 5V / 1–2A recommended |
| Charging Indicator | Built-in LED (Red = Charging, Green = Fully Charged) |
| Discharge Cut-off Voltage | 2.5 V (automatic protection cutoff) |
| Internal Resistance | Approx. 50–70 mΩ (including protection circuit and USB module) |
| Cycle Life | ≥ 500 cycles (to 80% capacity) |
| Operating Temperature (Discharge) | -20°C to 60°C |
| Charging Temperature | 0°C to 45°C |
| Top Type | Button Top |
| Dimensions | Approx. 21.5 mm diameter × 75.5 mm length (~5–6mm longer than standard unprotected 21700) |
| Weight (single cell) | Approx. 73 g |
| Package Includes | 1 × Fenix ARB-L21-4900U USB-C rechargeable battery |
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.
Shipping and Returns
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Free Shipping: Enjoy free shipping on all orders over $65. For orders under $65, the shipping cost is $8.99.
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Delivery Time: Once shipped, orders typically arrive within 7–15 business days.
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Easy Returns: We want you to be completely satisfied. If you're not, you can return your product within 30 days of receiving your order. Please ensure the items are unused and in their original condition. For return instructions, please contact our support team.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
Security
One USB-C cable charges my phone, watch, and this battery. Perfect for minimalist travel.
The USB-C charging doesn't sacrifice capacity or protection. Fenix did it right.
If you want built-in charging in a 21700, this Fenix is the best option.
After 6 months of use, the USB-C port is still solid. Capacity holding at 4800mAh.
My security camera runs on this 21700. The USB-C port allows charging without removing it.
Refund Policy
OneAndes Return & Refund Policy
At OneAndes, we are committed to providing high-quality cylindrical lithium-ion batteries for your drones, vacuums, garden tools, and other power needs. If you are not completely satisfied with your purchase, we are here to help. Please read our full return policy below before initiating a return.
1. Return Window
You have 30 calendar days from the date you received your item(s) to request a return. Any return request submitted after 30 days will not be eligible for a refund or exchange.
2. Eligibility Conditions
To qualify for a return, all items must meet the following conditions:
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Condition: Items must be unused, undamaged, and in the same condition that you received them.
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Packaging: Items must be returned in their original packaging with all accessories, manuals, and protective covers intact.
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Proof of Purchase: A valid receipt, order confirmation email, or proof of purchase must accompany all returns.
Non-Returnable Items:
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Batteries that have been installed, used, or show any signs of wear.
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Items marked as “Final Sale” or “Clearance” at the time of purchase.
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Customized or special-order products.
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Gift cards.
If a returned item fails to meet these conditions, we reserve the right to deny the return or charge a restocking fee.
3. How to Initiate a Return
Follow these steps to return your product:
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Contact Us: Email our support team at support@oneandes.com with your order number and the reason for return. We aim to respond to all return requests within 24 hours on business days.
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Receive RMA: We will provide you with a Return Merchandise Authorization (RMA) number and return instructions. Do not ship any item without an RMA number.
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Pack Securely: Place the item in its original packaging, include all accessories, and clearly write the RMA number on the outside of the box.
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Ship to Our US Warehouse: Ship the package to the following address:
OneAndes Returns
10320 6th St
Rancho Cucamonga, CA 91730
USA*Important: Lithium-ion batteries are classified as hazardous materials (Class 9). Please follow the shipping guidelines provided in Section 4 below. We recommend using a trackable shipping service and purchasing shipping insurance, as we cannot guarantee receipt of your returned item.*
4. Return Shipping Costs
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Defective or Incorrect Items: If the item you received is defective, damaged in transit, or different from what you ordered, OneAndes will cover the return shipping cost. In this case, we will provide you with a prepaid return shipping label.
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Buyer’s Remorse / Non-Defective Returns: If you are returning an item for any other reason (e.g., no longer needed, ordered the wrong model), you are responsible for the return shipping costs. You must prepay the return shipping cost using a trackable carrier that accepts lithium batteries. We do not provide prepaid return labels for non-defective returns.
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Lithium Battery Shipping Regulations: By law, all returns must be shipped in compliance with applicable dangerous goods regulations. We will provide guidance on proper packaging and labeling. Failure to comply may result in carrier refusal, seizure, or additional fees. We are not responsible for returned items lost or rejected by the carrier due to improper shipping.
5. Refunds
Once we receive and inspect your return at our Rancho Cucamonga, CA facility, we will notify you via email of the approval or rejection of your refund.
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Approved Refunds: If approved, your refund will be processed to your original method of payment within 5 to 10 business days. Please note that depending on your bank or credit card issuer, it may take additional time for the credit to appear on your statement.
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Partial Refunds: In certain situations, only partial refunds may be granted:
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Items not in original condition, missing parts, or damaged for reasons not due to our error.
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Items returned more than 30 days after delivery (reviewed on a case-by-case basis).
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Non-Refundable Fees: Original shipping charges are non-refundable unless the return is due to our error (defective product or incorrect shipment).
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Restocking Fee: We do not charge a restocking fee for defect-free returns, but we may deduct the return shipping cost, which will be deducted from your refund.
6. Exchanges
We replace items only if they are defective or damaged upon arrival. If you need to exchange a defective item for the same product, please contact us at support@oneandes.com. Exchanges are subject to product availability.
If you ordered the wrong battery size or model, please follow the standard return process above and place a new order for the correct item.
7. Damaged or Missing Items
If your package arrives visibly damaged, please take photos of the package before opening and contact us immediately. We will work with the shipping carrier to file a claim and arrange for a replacement or refund. Damaged or missing item claims must be reported within 7 calendar days of delivery. For immediate assistance, you may also call us at (213) 316-8849.
8. Order Cancellation
You may cancel your order without penalty if it has not yet been shipped. To cancel, email us at support@oneandes.com as soon as possible. If the order has already been processed or shipped, you will need to follow the standard return process upon receipt.
9. Warranty
All OneAndes batteries are backed by a 12-month limited warranty against defects in materials and workmanship. This warranty does not cover damage caused by misuse, improper charging, unauthorized modifications, normal wear and tear, or use outside of manufacturer specifications. For warranty claims, please contact our support team.
10. Contact Us
If you have any questions about our Return & Refund Policy, please reach out:
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Email: support@oneandes.com
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Phone: (213) 316-8849 (Mon-Fri, 9 AM – 5 PM Pacific Time)
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Mailing Address: 10320 6th St, Rancho Cucamonga, CA 91730, USA
We aim to respond to all inquiries within 24 hours during business days. Please include your order number for faster assistance.