{"product_id":"fenix-21700-rechargeable-battery-3-7volt-lithium-batteries-5800mah-button-top-for-headlamp-flashlight","title":"Fenix ARB-L21-5800 21700 5800mAh 10A 3.6V Button Top Protected Battery – Max Capacity for Flashlights \u0026 Headlamps","description":"\u003ch4\u003e\u003cspan class=\"\"\u003eDescription\u003c\/span\u003e\u003c\/h4\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cspan class=\"\"\u003eMaximize your runtime to the absolute limit with the genuine Fenix ARB-L21-5800, the highest-capacity 21700 battery in Fenix's lineup. Built around an ultra-high-capacity 5800mAh cell core, this protected button top battery delivers approximately 16% more runtime than standard 5000mAh 21700 cells—making it the ultimate power solution for extended missions, multi-day adventures, and professional applications where changing batteries is inconvenient or impossible. Integrated overcharge, over-discharge, and short-circuit protection ensures safe, worry-free operation, while the raised button top guarantees reliable contact in Fenix and most other 21700 flashlight brands. For users who refuse to compromise on runtime, the ARB-L21-5800 is the undisputed endurance champion.\u003c\/span\u003e\u003c\/p\u003e\n\u003ch4\u003e\u003cspan class=\"\"\u003eKey Features\u003c\/span\u003e\u003c\/h4\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003e5800mAh Maximum 21700 Capacity\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – The highest capacity battery in the Fenix 21700 lineup. Provides approximately 16% more runtime than 5000mAh cells and about 65% more energy than a standard 3500mAh 18650.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003e10A Continuous Discharge\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Delivers stable, reliable power for demanding LED flashlights and outdoor equipment. Enough current for turbo modes and high-output settings without triggering protection.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eBuilt-in Protection Circuit\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Safeguards against overcharge (4.2V cutoff), over-discharge (2.5V cutoff), short circuits, and overcurrent (10A limit), ensuring safe operation and protecting your valuable devices.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eButton Top Design\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Raised positive terminal ensures reliable electrical contact in Fenix and most other 21700 flashlights and devices requiring a button top.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eLong Cycle Life\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Retains over 80% of initial capacity after 500 charge\/discharge cycles under recommended conditions, reducing long-term replacement costs.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eFenix Genuine Quality\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Manufactured to strict standards with a premium 21700 cell core and advanced protection circuitry for consistent, safe performance in demanding applications.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003e\u003cspan class=\"\"\u003eParameters\u003c\/span\u003e\u003c\/h4\u003e\n\u003cdiv class=\"ds-scroll-area ds-scroll-area--show-on-focus-within ds-scroll-area--enabled _1210dd7 c03cafe9\"\u003e\n\u003cdiv class=\"ds-scroll-area__gutters\"\u003e\n\u003cdiv class=\"ds-scroll-area__horizontal-gutter\"\u003e\u003c\/div\u003e\n\u003cdiv class=\"ds-scroll-area__vertical-gutter\"\u003e\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003cspan class=\"\"\u003eParameter\u003c\/span\u003e\u003c\/th\u003e\n\u003cth\u003e\u003cspan class=\"\"\u003eSpecification\u003c\/span\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003cbr\u003e\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eModel\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eFenix ARB-L21-5800\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eBattery Type\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e21700 Button Top Protected Lithium-Ion\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eTypical Capacity\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e5800 mAh (0.2C discharge to 2.5V)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eMinimum Capacity\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e~5700 mAh\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eNominal Voltage\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e3.6 V (typical operating 3.7 V)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eMax Continuous Discharge\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\n\u003cstrong\u003e\u003cspan class=\"\"\u003e10 A\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e (limited by built-in protection circuit)\u003c\/span\u003e\n\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eProtection Functions\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eOvercharge (4.2V cutoff), Over-discharge (2.5V cutoff), Short Circuit, Overcurrent\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eDischarge Cut-off Voltage\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e2.5 V (automatic protection cutoff)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eStandard Charge\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eCC-CV, 0.5C (2900 mA) to 4.2 V, cut-off 50 mA (use a quality Li-ion charger)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eInternal Resistance\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eApprox. 40–60 mΩ (including protection circuit and button top)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eCycle Life\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e≥ 500 cycles (to 80% capacity)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eOperating Temperature (Discharge)\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e-20°C to 60°C\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eTop Type\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eButton Top\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eDimensions\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eApprox. 21.5 mm diameter × 71.5 mm length (~1–2mm longer than standard unprotected 21700)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eWeight (single cell)\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eApprox. 73 g\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003ePackage Includes\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003e1 × Fenix ARB-L21-5800 protected button top battery\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003cbr\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003ch4\u003e\u003cspan class=\"\"\u003eApplications\u003c\/span\u003e\u003c\/h4\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eRecommended For\u003c\/span\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eHigh-Output 21700 LED Flashlights\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Perfect for Fenix and other 21700-powered flashlights. The 5800mAh capacity delivers the longest illumination time available in a protected 21700 cell—ideal for search and rescue, professional inspection, and extended outdoor expeditions.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eHeadlamps for Professional \u0026amp; Outdoor Use\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Designed for cave exploration, long-distance trail running, industrial inspection, and multi-day camping. The protection circuit prevents over-discharge damage during extended use.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eCamping Lanterns \u0026amp; Emergency Lights\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Reliable power for extended power outages and off-grid living. The 5800mAh capacity ensures lights stay on through the longest nights.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eBicycle Lights for Ultra-Endurance\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Perfect for 24-hour races, multi-day bikepacking, and long-distance touring. Single-cell runtime covers entire events without battery changes.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eSmart Doorbells \u0026amp; Wireless Security Cameras (21700 Compatible)\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Months of standby time with reliable power for motion detection and recording events.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eSearch \u0026amp; Rescue Equipment\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: When missions extend beyond expected timeframes, the extra 800mAh over standard 5000mAh cells provides a critical safety margin.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003ePortable Fans \u0026amp; Outdoor Gadgets\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Suitable for any 21700-powered device drawing under 10A where maximum runtime is the priority.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eNot Recommended For\u003c\/span\u003e\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eHigh-Power Vaping \/ Mechanical Mods\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: These require 15–35A unprotected cells. The 10A protection limit is insufficient for sub-ohm applications.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eCordless Power Tools\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Drills, saws, and impact drivers demand 20–40A continuous current, far beyond this battery's 10A protection limit.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eRC Cars, Drones \u0026amp; High-Drain Models\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: These require 20–30A+ continuous current. This battery will not function and may trigger protection.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003e18650-Only Devices\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: This is a 21700 cell (21mm diameter) and will not physically fit in 18650 battery compartments.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eMulti-Cell Series Packs\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Individual protection boards may conflict. Use matched unprotected cells with an external BMS instead.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch4\u003e\u003cspan class=\"\"\u003eFAQ\u003c\/span\u003e\u003c\/h4\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: Is 5800mAh the real capacity? How much more runtime does it give compared to 5000mAh?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: Yes. The ARB-L21-5800 uses an ultra-high-capacity 21700 cell core that delivers a true 5800mAh under standard test conditions. Compared to a 5000mAh 21700 cell, this provides approximately 16% more runtime. In a typical flashlight on high mode, this could mean an extra 30–45 minutes of illumination. Compared to a 3500mAh 18650, it offers about 65% more energy.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: Is this battery compatible with my Fenix 21700 flashlight?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: Yes. The ARB-L21-5800 is specifically designed for Fenix 21700 flashlights and is compatible with most other brands requiring a button top 21700 cell. Due to the protection circuit and button top, the battery is approximately 71.5mm long. Most 21700 flashlights are designed to accommodate protected cells, but please verify your device's battery compartment length before ordering.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: Can I use this battery in my 18650 device?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: No. The 21700 format has a larger diameter (21mm vs. 18mm for 18650) and will not physically fit into 18650 battery compartments. Only use this battery in devices specifically designed for 21700 cells.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: What does \"protected\" mean and why does it matter?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: A protected cell has a built-in circuit board that automatically prevents overcharge (above 4.2V), over-discharge (below 2.5V), short circuits, and excessive current draw (above 10A). This makes single-cell use significantly safer, especially in devices without their own battery management. The trade-off is a slightly longer cell (71.5mm vs. ~70mm) and a current limit of 10A.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: Can I use this battery for vaping or power tools?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: No. Vaping devices and power tools require high continuous currents (typically 15–40A). The ARB-L21-5800's protection circuit limits output to approximately 10A. Using it in such devices will cause the protection to cut off power or may damage the battery. Please use dedicated unprotected high-drain cells for those applications.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: How should I charge and store this battery?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: Use a quality lithium-ion battery charger with a CC-CV algorithm designed for 21700 cells. Fenix chargers are an excellent match. Charge at 0.5C (2.9A) for best longevity. 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.\u003c\/span\u003e\u003c\/p\u003e","brand":"Fenix","offers":[{"title":"Default Title","offer_id":51454157619446,"sku":"OAS415","price":31.98,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0819\/2753\/6886\/files\/imagesfenix-21700-5800mah-button-top-main_d6331926-3412-4898-bfde-ccbf0849e2a2.webp?v=1786965967","url":"https:\/\/oneandes.com\/products\/fenix-21700-rechargeable-battery-3-7volt-lithium-batteries-5800mah-button-top-for-headlamp-flashlight","provider":"OneAndes","version":"1.0","type":"link"}