3500mAh (12.95Wh) 3.7V 18650 Li-ion Rechargeable Battery (2-Pack) – Long-Lasting Power for Flashlights, Headlamps, Fans & Outdoor Lights

Endurance That Keeps Up With You

When your adventures span from sunset to sunrise, you need a battery that refuses to quit early. This 2‑pack of 3500mAh 18650 cells stores a massive 12.95 watt‑hours of energy per cell — nearly double what a standard 2000mAh battery can hold. It’s the definitive power upgrade for devices that must run for hours on end: the flashlight guiding you through a night hike, the headlamp illuminating your campsite, the portable fan keeping the tent comfortable, or the outdoor garden light standing guard until dawn. With two cells in the pack, you always have a fully charged spare ready to swap, doubling your total runtime and eliminating downtime.

Unprotected, Uninhibited, Unbeatable Compatibility

We deliberately leave the external protection PCB off these batteries for three good reasons: shorter length, lower internal resistance, and unfettered compatibility. The flat‑top version measures just 65.0mm, the button‑top 66.5mm — both significantly shorter than a typical protected 18650. This means they slide effortlessly into ultra‑compact flashlights, tight‑fitting fan battery bays, and outdoor light compartments that simply cannot accommodate the extra 2–3mm of a protection circuit. By removing the PCB, we also eliminate an extra layer of electrical resistance, allowing more of the stored energy to reach your device, generating less heat and maintaining voltage under load. The trade‑off is small: you must pair these cells with a quality charger that stops at exactly 4.2V, and only install them in devices that have their own built‑in low‑voltage cutoff. The vast majority of modern LED flashlights, headlamps, USB‑rechargeable fans, and outdoor solar lights already meet this requirement, making them ideal partners.

Choose Your Connection: Button Top or Flat Top

To cover every possible device, we supply both positive terminal styles. The Button Top has a raised positive nipple (~1.5mm) that locks securely into spring‑loaded battery compartments, easily passing mechanical reverse‑polarity protection rings. It’s the go‑to choice for many consumer flashlights, headlamps, and fan holders. The Flat Top has a completely flush positive end, mandatory for devices with extremely tight battery tubes (where even a millimeter matters), for spot‑welding custom DIY battery packs, and for gadgets that use pogo‑pin or flat PCB contacts. Check your device manual, select the right version, and enjoy a wiggle‑free, reliable connection every time.

Where 3500mAh Becomes a Game‑Changer

Rated for a maximum continuous discharge of 5A (approximately 1.4C), this cell is optimized for medium‑drain, long‑runtime applications — precisely the profile of the flashlights, headlamps, fans, and outdoor lights it’s designed for. In a high‑performance LED flashlight, a single 3500mAh cell delivers over 3.5 hours of bright 300‑lumen output, or an entire night on a gentle 50‑lumen low mode. A lightweight headlamp will easily power a weekend camping trip or multiple evening runs on one charge. A portable USB fan can hum on low speed for 10–14 hours, covering two full work shifts or a sweltering night in a tent. And in a solar‑powered outdoor garden light, the 12.95Wh energy reserve stores enough daytime sun to illuminate pathways, flowerbeds, and patios from dusk until well past midnight, far outlasting the smaller 1500mAh cells often bundled with such fixtures. With two cells, you can keep one in use and one on charge — zero waiting, total peace of mind.

Built for Years of Reliable Service

Under the nickel‑plated steel shell, high‑density NMC chemistry maintains a stable 3.7V nominal voltage and an impressively flat discharge curve. Your light doesn’t gradually dim, your fan doesn’t slowly lose speed, and your outdoor light stays bright hour after hour. Despite the lack of an external protection IC, each cell features a built‑in PTC thermistor that suppresses over‑current spikes and a resealable pressure vent that releases gas under extreme thermal stress. The steel can shrugs off drops, corrosion, and daily abuse. With a cycle life exceeding 500 full charges and exceptionally low self‑discharge, you can store a spare for months at the recommended voltage, and it will wake up with most of its capacity intact — ready for the next power outage, camping trip, or backyard party.

Key Features

• Genuine 3500mAh High Capacity (12.95Wh per cell)
  Nearly double the energy of a 2000mAh battery. Delivers extended runtime for flashlights, headlamps, fans, and outdoor lights — fewer swaps, more doing.

• 2‑Pack for Uninterrupted Power
  Two identical cells. Keep one in your device, one fully charged in reserve. Perfect for long excursions, multi‑day trips, or high‑use scenarios.

• Unprotected, Ultra‑Compact Design
  Shorter length (65.0mm flat, 66.5mm button) fits tight battery compartments that reject longer protected cells. Lower overall internal resistance means cooler operation and more power to your device.

• Dual Terminal Options: Button Top & Flat Top
  Button Top for a secure click in spring‑contact devices. Flat Top for recessed contacts, spot‑welded packs, and space‑constrained gadgets. Full compatibility — no adapters needed.

• Stable NMC Chemistry & Flat Discharge
  Maintains a consistent 3.7V from 4.2V down to 2.5V. Your LED stays bright, your fan speed holds steady, and your outdoor light performs predictably.

• Low Internal Resistance (≤60mΩ)
  Minimal voltage sag even under a 5A load. On typical 1–3A flashlight and fan draws, the drop is virtually imperceptible, maximizing usable capacity.

• 500+ Cycle Life & Negligible Self‑Discharge
  Recharge each cell over 500 times with minimal capacity loss. Store for months at 3.6–3.7V — it will still be ready for action when you need it.

• Built‑In Passive Safety Mechanisms
  PTC thermistor suppresses over‑current; resealable vent prevents pressure buildup. Nickel‑plated steel can resists impact, leaks, and corrosion.

• Eco‑Friendly & Cost‑Effective
  Replaces hundreds of disposable alkaline batteries over its lifetime. Zero memory effect allows partial top‑ups without conditioning.

Technical Parameters

Applications

1. High‑Performance LED Flashlights
   For enthusiasts who demand maximum runtime from their EDC or tactical lights. On a 300‑lumen medium setting, one cell lasts over 3.5 hours; on a low 50‑lumen mode, it can illuminate an entire night. Flat top fits ultra‑tight ZebraLight tubes; button top locks securely into spring‑loaded hosts. Keep the spare in your pocket for instant swaps during extended night use.

2. Headlamps for Extended Outdoors
   Trail runners, backpackers, and campers will appreciate a headlamp that won’t die mid‑adventure. At a comfortable 100‑lumen setting, expect over 10 hours of hands‑free illumination. The cell’s moderate weight keeps the headlamp balanced and comfortable, even during active movement.

3. Portable Fans for All‑Day Cooling
   USB‑rechargeable desk fans, camping fans, and stroller fans pair brilliantly with this high‑capacity cell. On low speed, enjoy 10–14 hours of gentle breeze — enough for two full work shifts or a night in a hot tent. On high, expect around 3–4 hours of strong airflow. The flat top is often required for recessed fan battery bays.

4. Outdoor Garden & Path Lights
   Replace the smaller 1500–2000mAh cells in your solar‑powered outdoor lights with these 3500mAh workhorses. They store more energy during the day, keeping your pathways, flowerbeds, and patios illuminated from dusk until well after midnight. Ensure your solar light’s charge controller has its own over‑discharge protection.

5. Backup Power & Emergency Kits
   Keep a few charged cells in your go‑bag, glovebox, or power‑outage drawer. The ultra‑low self‑discharge means they’ll still be full months later, ready to power flashlights, radios, or USB chargers when the grid fails.

6. DIY Battery Packs & Hobby Projects
   The flat top variant is purpose‑built for spot welding into 2S or 3S configurations for portable Bluetooth speakers, drone ground stations, or custom power banks. The high per‑cell capacity minimizes the total number of cells needed for a given energy target.

FAQ

Q1: Is 3500mAh a true capacity? Many batteries exaggerate.
A: Yes, this cell uses high‑density NMC electrodes to achieve a genuine 3500mAh. We encourage you to test it with a professional analyzing charger — you will see close to 3500mAh discharged from 4.2V to 2.5V at a 0.2C rate.

Q2: Why is this battery unprotected? Is it safe for my flashlight?
A: We omit the protection PCB to keep the cell short (fits more devices) and to lower internal resistance. It’s perfectly safe when used correctly: charge only with a dedicated 4.2V Li‑ion charger, and use only in devices that have built‑in low‑voltage cutoff (like most modern flashlights, headlamps, USB fans, and solar charge controllers). The cell includes a PTC thermistor and pressure vent for passive safety.

Q3: How do I choose between Button Top and Flat Top?
A: If your device has a spring at the positive end and a plastic ring that would block a flat terminal, you need a Button Top. If the battery tube is very tight or the positive contact is a flat metal pad (common in ZebraLight, some fans, and welded packs), you need a Flat Top. Always consult your device manual.

Q4: Can I use this battery in an RC car or high‑drain device?
A: No, this is an energy‑density cell rated for a maximum continuous discharge of 5A. RC cars, power tools, and sub‑ohm typically require 10–30A or more. Using this cell in such a device could cause severe voltage sag, overheating, and damage. For high‑drain needs, please select our 10C/20A high‑rate batteries.

Q5: How long will a 3500mAh battery run my portable fan?
A: On low speed (drawing around 0.3–0.5A), expect 10–14 hours. On high speed (1.5–2A), around 3–4 hours. With two cells in the pack, you can swap and keep the air moving continuously.

Q6: How should I store the spare battery?
A: Store it in a plastic battery case, away from keys, coins, and moisture. For storage longer than one month, adjust the voltage to about 3.6–3.7V (roughly 50% charge). Check every 3 months and recharge if it drops below 3.0V. Never store a fully depleted cell.

Q7: How many times can I recharge this battery?
A: Over 500 full charge/discharge cycles while retaining at least 70% of its original capacity. For devices that are recharged once a week, that’s nearly 10 years of service.

Q8: Can I bring these batteries on an airplane?
A: Yes. At 12.95Wh per cell, they are well under the 100Wh IATA limit. Carry them in your hand luggage with terminals insulated (electrical tape or a plastic case). Airlines permit multiple small Li‑ion cells for personal use.

Q9: What charger do you recommend?
A: Any quality charger designed for 3.7V Li‑ion cells with accurate 4.2V termination. A basic single‑ or dual‑bay smart charger from brands like Nitecore, XTAR, or LiitoKala works perfectly. Never use a NiMH or alkaline charger.