{"product_id":"fenix-18650-rechargeable-battery-3-6v-3850mah-18650-button-top-battery-for-headlights-etc","title":"Fenix ARB-L18-3850 18650 3850mAh 5A 3.6V Button Top Protected Battery – High 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=\"\"\u003eGet noticeably more runtime with the genuine Fenix ARB-L18-3850, a protected 18650 button top battery that bridges the gap between standard 3500mAh cells and premium 4000mAh models. Built around a high-capacity Panasonic 3850mAh cell core, it delivers approximately 10% more runtime than standard 3500mAh batteries at a more accessible price point. Integrated overcharge, over-discharge, and short-circuit protection ensures safe, worry-free operation, while the raised button top guarantees reliable contact in Fenix, Streamlight, and most other major flashlight brands. For users who want a meaningful runtime upgrade without the premium price tag, the ARB-L18-3850 is the smart choice.\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=\"\"\u003e3850mAh Extended Capacity\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Powered by a genuine Panasonic high-capacity cell core, delivering approximately 10% more runtime than standard 3500mAh cells. An ideal sweet spot between standard and maximum capacity.\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, protecting both the battery and your valuable equipment.\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, Streamlight, and most other 18650 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 its initial capacity after 500 charge\/discharge cycles, 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 an authentic Panasonic cell core and premium protection circuitry for consistent, safe performance.\u003c\/span\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eWide Compatibility\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e – Ideal for single-cell LED torches, headlamps, camping lanterns, bicycle lights, and other outdoor illumination equipment drawing under 5A.\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-L18-3850\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003eCell Core\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan class=\"\"\u003ePanasonic High-Capacity (3850mAh variant)\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=\"\"\u003e3850 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~3750 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=\"\"\u003e5 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 (~1900 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. 60–80 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. 18.6 mm diameter × 68.5 mm length (~3–4mm longer than standard unprotected flat top)\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. 50 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-L18-3850 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=\"\"\u003eLED Flashlights \u0026amp; Tactical Torches\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Perfect for Fenix, Streamlight, and other quality brands requiring a button top 18650. The 3850mAh capacity provides a tangible runtime upgrade over standard 3500mAh cells—ideal for extended trips, professional use, or anyone who wants to change batteries less often.\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 Outdoor \u0026amp; Professional Use\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Ideal for camping, running, caving, and industrial work. The protection circuit prevents over-discharge damage when lights are accidentally left on, and the extended capacity means fewer battery swaps on long excursions.\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 trips and power outages. The 3850mAh 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\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Consistent output for night riding. Single-cell runtime easily covers long commutes, weekend tours, or endurance training 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\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: Many video doorbells use 18650 cells. The ARB-L18-3850 provides extended runtime between charges, reducing maintenance frequency.\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 18650-powered device drawing under 5A where longer runtime is desired.\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 protection circuit will cut off power under heavy loads.\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 15–40A, far beyond this battery's 5A 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 RC Models\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: These require 10–30A+ 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=\"\"\u003eUltra-Compact Flashlights with Tight 65mm Battery Tubes\u003c\/span\u003e\u003c\/strong\u003e\u003cspan class=\"\"\u003e: The protected button top design adds length (~68.5mm). Some compact lights may not close fully. Always verify your device can accommodate the extra length.\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: How does the 3850mAh compare to 3500mAh and 4000mAh cells?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: The ARB-L18-3850 sits right in the middle: it delivers approximately 10% more runtime than a standard 3500mAh cell, while typically being more affordable than the 4000mAh flagship model. In practical terms, this means an extra 25-30 minutes on high mode or several additional hours on low mode in a typical flashlight compared to a 3500mAh cell.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: Is this battery compatible with my Streamlight \/ Fenix \/ other brand flashlight?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: If your flashlight accepts 18650 batteries and requires a button top (raised positive terminal), then yes. The ARB-L18-3850 is compatible with most Fenix and Streamlight models, as well as many other major flashlight brands. Due to the protection circuit and button top, the battery is approximately 68.5mm long. Some ultra-compact lights with very tight battery tubes may not close properly. Please check 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: What does \"protected\" mean and why should I choose a protected cell?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: A protected cell has a small circuit board added to the negative end that automatically prevents overcharge (above 4.2V), over-discharge (below 2.5V), short circuits, and excessive current draw. This makes single-cell use much safer, especially in devices without their own battery management. The trade-off is a slightly longer cell (68.5mm vs. 65mm) and a current limit of around 5A.\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, RC cars, or power tools?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: No. These applications require high continuous currents (typically 15–35A or more). The ARB-L18-3850's protection circuit limits current to approximately 5A. 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 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 18650 cells. Fenix chargers are an excellent match. Charge at 0.5C (~1.9A) for best longevity. The built-in protection circuit provides an additional safety layer, but a good charger is still essential. Never use damaged or low-quality chargers.\u003c\/span\u003e\u003c\/p\u003e\n\u003cp class=\"ds-markdown-paragraph\"\u003e\u003cstrong\u003e\u003cspan class=\"\"\u003eQ: How should I store this battery when not in use?\u003c\/span\u003e\u003c\/strong\u003e\n\u003cbr\u003e\u003cspan class=\"\"\u003eA: Store at approximately 3.6–3.7V (40–50% charge) in a cool, dry place. Use a non-conductive battery case to prevent accidental short circuits. Avoid storing fully charged or fully discharged for extended periods, as this accelerates capacity loss.\u003c\/span\u003e\u003c\/p\u003e","brand":"Fenix","offers":[{"title":"Default Title","offer_id":51454154670326,"sku":"OAS407","price":27.98,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0819\/2753\/6886\/files\/imagesfenix-3850mah-18650-battery-main_22ec4f9e-0463-443a-8df3-71d375b58b34.webp?v=1786965955","url":"https:\/\/oneandes.com\/products\/fenix-18650-rechargeable-battery-3-6v-3850mah-18650-button-top-battery-for-headlights-etc","provider":"OneAndes","version":"1.0","type":"link"}