Product Description
Uncompromising Power for the Most Demanding Devices
When your gear demands extreme current — a turbo flashlight blasting thousands of lumens, a cordless drill biting into steel, or a racing drone pulling full throttle — the Samsung INR21700-40T answers without hesitation. This cell is a true high‑drain champion, rated for a massive 35A continuous discharge (with pulse capability significantly higher). It packs 4000mAh of genuine capacity, striking a deliberate balance between raw power and usable runtime. In the world of 21700 batteries, the 40T is a legend: trusted by flashlight hot‑rodders, power tool rebuilders, and FPV pilots who can't afford voltage sag at critical moments.
35 Amps of Relentless Current
The 40T's headline specification is its extraordinary ability to deliver current. With an internal resistance so low (≤14mΩ) that it barely registers heat at 35A, this cell keeps your devices at full throttle long after ordinary energy cells have collapsed in voltage. In a FET‑driven turbo flashlight drawing 20–30A, the 40T maintains a stable voltage plateau — no premature step‑down, no flickering, just a blinding wall of light. In a cordless impact driver or circular saw, the cell provides the instantaneous torque required to drive screws into hardwood or cut through sheet metal without stalling. And in a racing drone or high‑power RC model, the 40T feeds the brushless motors with the sustained current they crave, keeping lap times low and punch‑outs explosive.
Genuine 4000mAh — Runtime That Respects the Amps
High‑drain cells often sacrifice capacity for current. Samsung has engineered the 40T to deliver both. The 4000mAh capacity (approximately 14.8 watt‑hours) means you aren't swapping batteries every few minutes. A turbo flashlight gets meaningful bursts of full brightness; a cordless tool completes a series of demanding tasks on one pack; a drone stays in the air for a competitive flight time. This is the cell you choose when you refuse to accept the false choice between power and endurance.
Unprotected, Purpose‑Built for Enthusiasts
The 40T is supplied as a bare, unprotected cell — exactly as Samsung intends. There is no external protection PCB to add length, increase resistance, or inadvertently trip under high current surges. The result is a cell that measures just 70.0mm (flat top) or 71.0mm (button top), fits effortlessly into the tightest flashlight tubes and the most compact tool battery shells, and delivers its full 35A without interference. In return, you simply use a quality charger that terminates at 4.2V and install the cell only in devices that have their own low‑voltage cutoff — a feature already present in virtually all modern turbo flashlights, brushless power tools, and drone electronics.
Three Terminal Options for Total Flexibility
We offer the 40T in three distinct positive‑terminal configurations to ensure a perfect fit for any application:
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Flat Top: A completely flush positive terminal. Mandatory for ultra‑tight flashlight tubes, pogo‑pin contacts, and spot‑welded battery packs. Most enthusiast lights (ZebraLight, Noctigon, Emisar, etc.) and many power tool rebuilds require flat‑top cells.
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Button Top: A raised positive nipple (~1.5mm) that locks securely into spring‑loaded compartments and passes mechanical reverse‑polarity guards. Ideal for consumer flashlights, some tool adapters, and devices with spring‑based contacts.
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Nickel Tab: Both positive and negative ends come pre‑welded with pure nickel strips, ready for soldering or additional spot welding. The turn‑key solution for building high‑current battery packs for drones, power tools, or custom electronics.
Samsung INR Chemistry — The Heart of the 40T
Under the nickel‑plated steel can, Samsung's advanced INR (Nickel‑Manganese‑Cobalt) chemistry delivers not only exceptional power density but also excellent thermal stability and cycle life. The cell is rated for over 500 full charge/discharge cycles while retaining ≥70% of its initial capacity. Low self‑discharge ensures that your spare packs stay ready for weeks or months. Built‑in safety features — a PTC thermistor that increases resistance during over‑current, a resealable safety vent that releases pressure in extreme conditions, and a CID (Current Interrupt Device) that physically disconnects the electrode if internal pressure continues to rise — provide multi‑layered passive protection, giving you confidence even under the most demanding loads.
Key Features
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35A Continuous High Discharge — True 9C Rating
Delivers a genuine 35A continuous current. Handles the most demanding flashlights, power tools, and drones without voltage sag. Can pulse even higher for split‑second torque bursts.
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4000mAh Genuine Capacity (14.8Wh)
A balanced capacity that provides meaningful runtime in high‑drain applications. Enough for sustained turbo bursts, repeated tool tasks, or competitive drone flights.
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Ultra‑Low Internal Resistance (≤14mΩ)
Minimal heat generation and voltage drop. At 35A, the voltage sags by only ~0.49V, keeping your devices in regulation and your performance at its peak.
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Unprotected Bare Cell — Standard 70mm Length
Fits all 21700‑compatible devices. Eliminates the added resistance and length of a protection PCB, essential for high‑current applications. Requires a quality 4.2V Li‑ion charger and a device with low‑voltage cutoff.
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Three Terminal Options: Flat Top, Button Top & Nickel Tab
Flat Top for ultra‑tight tubes and pogo‑pin contacts. Button Top for spring‑loaded compartments. Nickel Tab for ready‑to‑weld high‑current battery packs. Complete versatility.
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Advanced Samsung INR (NMC) Chemistry
Provides a stable 3.7V nominal voltage, flat discharge curve, and excellent thermal stability — trusted in professional power tools and electric vehicles.
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500+ Cycle Life & Low Self‑Discharge
Recharge over 500 times with minimal capacity fade. Holds charge for months when stored at 3.6–3.7V — always ready for the next race, job, or adventure.
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Multi‑Layered Passive Safety
Built‑in PTC thermistor, resealable safety vent, and CID protect against over‑current, over‑pressure, and internal short circuits.
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Rugged Nickel‑Plated Steel Can
Corrosion‑resistant and impact‑resistant. Built to withstand the vibrations, drops, and temperature swings of power tools, drones, and outdoor environments.
Technical Parameters
Applications
1. Turbo Flashlights & Hot‑Rod Lights
For FET‑driven multi‑emitter flashlights, custom SBT90.2 builds, and any light that pulls 20–35A, the 40T is the gold standard. It holds voltage rock‑steady, preventing early step‑down and keeping lumens at maximum. Flat top fits ultra‑tight enthusiast tubes; button top secures in spring‑loaded hosts.
2. Cordless Power Tools (Rebuilds & Upgrades)
Replace worn‑out cells in drills, impact drivers, circular saws, and angle grinders with 40T cells. The 35A continuous discharge handles the startup spikes and sustained loads of professional‑grade tools. Use flat tops or nickel tabs to build 5S1P or 5S2P packs for 18V/20V platforms.
3. Racing Drones & FPV Quadcopters
The 40T is a favorite among drone pilots who need high current and low voltage sag for punch‑outs and high‑speed runs. Build a 4S or 6S pack for racing or freestyle quads; the 4000mAh capacity provides competitive flight times while delivering the amps that brushless motors demand.
4. High‑Power RC Models
RC cars, trucks, boats, and aircraft that run on 2S–6S Li‑ion packs benefit from the 40T's blend of current and capacity. Whether you're bashing, crawling, or speed‑running, the 40T delivers the punch and runtime you need.
5. E‑Bike & Scooter Battery Packs
For high‑power e‑bikes and scooters that require sustained high current, the 40T is an excellent cell choice in multi‑parallel configurations (e.g., 4P, 5P). It provides the necessary current without the excessive voltage sag of lower‑drain cells.
6. Portable High‑Power Inverters & Power Stations
DIY battery packs for portable inverters, camping power stations, and job‑site generators often demand high surge currents. The 40T handles these with ease, providing reliable power for tools, lights, and electronics.
FAQ
Q1: Is the Samsung 40T really capable of 35A continuous?
A: Yes. Samsung rates the INR21700-40T for 35A continuous discharge. With an internal resistance of only ~14mΩ, it can sustain this current while staying within safe temperature limits. It can also pulse higher (up to 45A) for short bursts.
Q2: Why is this battery unprotected? Is it safe to use in a flashlight or power tool?
A: Samsung 40T cells are designed as bare cells for pack building and high‑drain applications. Omitting the protection PCB minimizes length, reduces resistance, and prevents the current limit from tripping during high surges. It is completely safe when you use a quality 4.2V Li‑ion charger and only install it in devices that have built‑in low‑voltage cutoff — a standard feature in modern turbo flashlights, brushless tools, and drone electronics. The cell includes PTC, vent, and CID for passive safety.
Q3: Which terminal option should I choose — Flat Top, Button Top, or Nickel Tab?
A: Flat Top for ultra‑tight flashlight tubes and pogo‑pin contacts, and for spot‑welded packs. Button Top for spring‑loaded compartments and devices with reverse‑polarity rings. Nickel Tab if you are soldering or spot‑welding the cell into a pack. Consult your device manual if unsure.
Q4: Can I use the 40T in a device designed for an 18650?
A: No. A 21700 cell (21mm × 70mm) is larger than an 18650 (18mm × 65mm). The device must explicitly support 21700 batteries. Never force a 21700 into an 18650 tube.
Q5: How does the 40T compare to the Samsung 50E or 30T?
A: The 40T sits between the 50E (5000mAh, 10A) and the 30T (3000mAh, 35A but with higher pulse capability). The 40T offers a balanced 4000mAh capacity with 35A continuous — ideal for users who need both high current and decent runtime. The 30T is better for absolute maximum pulse current; the 50E is better for maximum runtime at lower currents.
Q6: How hot does the 40T get at 35A?
A: With ≤14mΩ internal resistance, heat generation at 35A is relatively modest. The cell will become warm — typically reaching ~60–70°C under sustained 35A load after several minutes — but remains within safe operating limits. Allow the cell to cool between heavy discharge cycles when possible.
Q7: Can I charge the 40T at 4A?
A: Yes, the maximum charge current is 4A (1C). However, for maximum cycle life, we recommend the standard 2A (0.5C) charge rate. Faster charging generates more heat and may slightly reduce long‑term capacity retention.
Q8: How should I store spare 40T cells?
A: Store them in a plastic battery case or silicone sleeve, away from metal objects and moisture. For storage longer than one month, bring the voltage to about 3.6–3.7V (roughly 50% charge). Check every 3 months and recharge if the voltage drops below 3.0V. Never store a fully depleted cell.
Q9: Can I bring the 40T on an airplane?
A: Yes. At 14.8Wh, it is well under the 100Wh IATA limit for carry‑on luggage. Insulate the terminals with tape or a plastic case and carry the cells in your hand luggage.
