2500mAh 3.7V 18650 Li-ion Rechargeable Battery (2-Pack) – High Capacity for LED Flashlights, Headlamps & Portable Fans

The Everyday Power Upgrade
Why settle for standard when you can have 25% more? Each cell in this 2‑pack stores a genuine 2500mAh — that’s 9.25 watt‑hours of energy, noticeably extending the runtime of your LED flashlights, headlamps, and portable fans compared to the common 2000mAh battery. It’s the intelligent upgrade for people who use their gear daily: the pocket torch that lights your way home, the headlamp that guides your evening run, the desk fan that hums through a long work shift. With two identical cells, you’ll always have a fully charged spare ready to swap — zero downtime, double the peace of mind.

Unprotected Design: Shorter, Lighter, More Efficient
We deliberately leave off the external protection PCB to create a cell that’s as compact and electrically pure as possible. At just 65.0mm (flat top) or 66.5mm (button top), these batteries slip effortlessly into tight flashlight tubes, slim headlamp compartments, and recessed fan battery bays that simply cannot accommodate the extra length of a protected cell. Removing the PCB also eliminates an extra layer of resistance, so more stored energy reaches your device and less is wasted as heat. The trade‑off is small: you must use a quality charger that stops exactly at 4.2V, and only install the cell in devices with built‑in low‑voltage cutoff — a standard feature in virtually all modern LED lights, headlamps, and USB‑rechargeable fans.

Choose Your Terminal: Button Top or Flat Top
Compatibility should never be a guessing game, so we offer both styles. The Button Top has a raised positive nipple (~1.5mm) that locks securely into spring‑loaded compartments and easily passes mechanical reverse‑polarity rings — common in many consumer flashlights and headlamps. The Flat Top has a completely flush positive end, essential for devices with ultra‑tight battery tubes, for spot‑welding custom DIY battery packs, and for gadgets with pogo‑pin or flat PCB contacts. Check your manual, pick the right version, and enjoy a wiggle‑free connection every time.

Where 2500mAh Makes All the Difference
Rated for a continuous discharge of up to 5A (2C), this cell is optimized for medium‑drain devices — exactly the profile of the flashlights, headlamps, and fans it’s designed for. In a compact LED flashlight, expect around 2.5 hours of bright 300‑lumen output, or over 8 hours on a gentle low mode. A lightweight headlamp will easily power a full night of reading, camping, or trail running on a single charge. A USB portable fan will hum on low speed for 6–8 hours, keeping you cool through a workday or a hot summer night. And because you have two batteries, you can keep one in use and one on standby — no waiting for a recharge when you need power most.

Built to Endure, Designed for Safety
Under the nickel‑plated steel shell, stable NMC chemistry holds a true 3.7V nominal voltage and a flat discharge curve, so your light doesn’t dim and your fan doesn’t slow until the battery is nearly empty. Despite the lack of an external protection IC, each cell includes a built‑in PTC thermistor to suppress over‑current spikes and a resealable pressure vent that activates under extreme internal stress. The steel can withstands drops, corrosion, and daily abuse. With over 500 full charge cycles and very low self‑discharge, you can store a spare for months at the recommended voltage, and it will wake up ready for the next adventure.

Key Features

• Genuine 2500mAh High Capacity (9.25Wh per cell)
  25% more energy than a standard 2000mAh battery. Delivers up to 2.5 hours of flashlight high‑mode light, 8+ hours of headlamp glow, or all‑day fan cooling.

• 2‑Pack for Uninterrupted Use
  Two identical cells. Keep one in your device, one fully charged in your bag. Perfect for extended trips, long shifts, or power outages.

• Unprotected, Ultra‑Compact Form
  Shorter than protected cells (65.0mm flat / 66.5mm button) to fit the tightest battery compartments. Lower overall resistance means more efficient power delivery and less heat.

• Dual Terminal Options: Button Top & Flat Top
  Button Top for a secure click in spring‑contact devices. Flat Top for recessed contacts, welded packs, and ultra‑tight tubes. No adapters, total compatibility.

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

• Low Internal Resistance (≤75mΩ)
  Minimal voltage sag under load. At a 5A draw, voltage drops by only 0.375V; on typical 1–3A loads, the drop is barely noticeable.

• 500+ Cycle Life & Low Self‑Discharge
  Recharge each cell over 500 times with minimal capacity fade. Store the spare at 3.6–3.7V for months; it will still be ready when you need it.

• Built‑In Passive Safety
  Integrated PTC thermistor and resealable safety vent provide foundational protection. Rugged steel can resists drops, leaks, and corrosion.

• Eco‑Friendly & Cost‑Effective
  Replaces hundreds of disposable alkalines. Zero memory effect lets you recharge at any state without conditioning.

Technical Parameters

Applications

1. LED Flashlights & EDC Torches
Perfect for daily‑carry lights, tactical torches, and compact throwers. The 2500mAh capacity provides approximately 2.5 hours on a 300‑lumen medium mode, or a full night on low. Flat top fits ultra‑tight enthusiast tubes; button top secures firmly in spring‑loaded hosts. Keep the spare in your pocket for instant swaps during extended use.

2. Headlamps for Work & Play
Whether you’re a trail runner needing hours of light, a mechanic working under a vehicle, or a camper reading in a tent, the 2500mAh cell won’t let you down. At 100 lumens, expect 7–8 hours of hands‑free illumination. The cell’s moderate weight keeps the headlamp balanced and comfortable.

3. Portable Fans for All‑Day Cooling
USB desk fans, stroller fans, and camping fans run beautifully on this cell. Low speed delivers 6–8 hours of gentle breeze; high speed offers 1.5–2 hours of strong airflow. Two cells let you swap and stay cool around the clock. Flat top is often required for recessed fan battery bays.

4. Camping Lanterns & Outdoor Lights
Compact lanterns and tent lights benefit from the 9.25Wh energy reserve, providing a full night of illumination. Keep the spare cell in your pack for multi‑day adventures.

5. DIY Battery Packs & Hobby Projects
The flat top variant is ready for spot welding into 2S or 3S packs for Bluetooth speakers, IoT sensors, or Arduino robots. Unprotected design gives you full control over your BMS.

6. Emergency Backup Power
Store a few charged cells in a waterproof case for blackouts, storms, or road trips. Their low self‑discharge ensures they’re ready when the grid isn’t.

FAQ

Q1: Is 2500mAh a high capacity? How much better is it than 2000mAh?
A: Yes, it offers a genuine 25% capacity boost over standard 2000mAh cells. In practice, a flashlight that lasts 2 hours on a 2000mAh battery will run for about 2.5 hours on this 2500mAh cell — a noticeable improvement for everyday use.

Q2: Why is this battery unprotected? Is it safe for my flashlight?
A: We omit the protection PCB to shorten the cell (fits more devices) and to reduce internal resistance. It’s completely safe when you use a quality 4.2V Li‑ion charger and only install it in devices with built‑in low‑voltage cutoff — which most modern flashlights, headlamps, and USB fans already have. The cell also includes a PTC thermistor and a safety vent for passive protection.

Q3: How do I choose between Button Top and Flat Top?
A: If your device’s positive contact is a spring with a plastic ring around it, you likely need a Button Top for firm contact. If the battery tube is extremely tight or the contact is a flat metal pad, you need a Flat Top. For building welded packs, always choose flat top.

Q4: Can I use this battery in a high‑drain RC car or power tool?
A: No. This cell is rated for a maximum continuous discharge of 5A, perfect for flashlights, headlamps, and fans. RC cars and power tools often demand 10–30A, which would overheat this battery and cause damage. For those, choose our dedicated high‑rate cells.

Q5: How long will a 2500mAh battery run my portable fan?
A: On low speed (~0.5A), about 5–6 hours; on high speed (~1.5A), roughly 1.5–2 hours. The 2‑pack lets you swap cells and keep the air moving continuously.

Q6: How should I store the spare battery?
A: Keep it in a plastic case, away from metal objects. For storage longer than a month, charge or discharge to about 3.6–3.7V (~50%). Check voltage every 3 months and recharge if below 3.0V. Never store a fully depleted cell.

Q7: How many times can I recharge these batteries?
A: Over 500 full cycles while retaining ≥70% capacity. For a device recharged weekly, that’s nearly a decade of service.

Q8: Can I take these on a plane?
A: Yes. At 9.25Wh per cell, they are well under the 100Wh IATA limit. Carry them in hand luggage with terminals insulated.

Q9: What charger should I use?
A: A charger specifically designed for 3.7V Li‑ion batteries that terminates at 4.2V. A basic smart charger from Nitecore, XTAR, or LiitoKala is perfect. Never use a NiMH or alkaline charger.