Delipow 4000mAh 3.6V 21700 Rechargeable Battery – High Drain Max 40A Flat Top for Turbo Flashlights, RC Models & Power Tools

Product Description

Delipow 21700: Pure Flat‑Top Power for Extreme Current Demands
When your gear demands instantaneous high current — a turbo flashlight blasting lumens, an RC truggy exploding out of a corner, or a cordless impact driver driving screws into hardwood — the Delipow 4000mAh 21700 battery delivers without hesitation. Engineered with a single, no‑compromise flat‑top design, this cell is purpose‑built for the tightest battery tubes, the most demanding pogo‑pin contacts, and the custom spot‑welded packs of serious enthusiasts. It is rated for 30A continuous discharge with a 40A max pulse, all while storing a genuine 4000mAh of energy (approximately 14.4 watt‑hours at 3.6V nominal). This is the sweet spot for users who need high‑drain performance without sacrificing meaningful runtime.

Unprotected, Flat‑Top — Why It Matters
The Delipow 21700 comes as an unprotected bare cell with a completely flush positive terminal. We intentionally omit the external protection PCB to keep the overall length at the industry‑standard 70.0mm — critical for fitting into precisely machined flashlight tubes, compact power tool battery shells, and densely packed RC battery trays. Removing the PCB also eliminates the added internal resistance that can choke current flow during high‑drain pulses, ensuring your devices get every last amp they demand. The flat‑top terminal is the universal standard for high‑performance devices: it mates perfectly with pogo‑pin contacts, recessed flat PCB pads, and nickel strip spot welds without the added height of a button top that can prevent caps from closing or cause intermittent contact. Naturally, this design requires you to use a quality charger with precise 4.2V termination and to only install the cell in devices that have their own low‑voltage cutoff — a feature already present in virtually all modern turbo flashlights, brushless RC ESCs, and power tool motor controllers.

Where the Delipow 40A Flat‑Top Cell Excels
In a FET‑driven turbo flashlight (Emisar D4SV2, Noctigon K1, custom SBT90.2 builds), the Delipow 4000mAh flat‑top cell delivers the instantaneous 20–30A surges needed to keep the LEDs at full blaze without triggering early step‑down. Its flush terminal ensures a perfect fit in the ultra‑tight battery tubes typical of these lights. In a 1/10 scale RC truggy or monster truck, a 2S or 3S pack built from these cells provides relentless punch off the line and strong mid‑range torque that lasts an entire heat — and the flat tops weld cleanly into stick or saddle packs. For cordless power tools — drills, impact drivers, mini circular saws — the high discharge rate prevents motor stalling under load, while the 4000mAh capacity lets you drive dozens of screws or make numerous cuts before reaching for the charger. The flat‑top design is also the standard for rebuilding 18V/20V tool batteries, where cells are spot‑welded in series.

Safety and Longevity Without the PCB
Delipow’s advanced NMC (Nickel‑Manganese‑Cobalt) chemistry provides a flat 3.6V nominal discharge curve, excellent thermal stability, and an impressive cycle life. The cell is rated for over 500 full charge/discharge cycles while retaining at least 70% of its original capacity. Low self‑discharge means a spare pack stored at 3.6–3.7V will be ready months later. Built‑in passive safety layers include a PTC thermistor that increases resistance during over‑current, a resealable safety vent that releases gas if internal pressure builds dangerously, and a CID (Current Interrupt Device) that physically disconnects the internal electrode under extreme pressure. The rugged nickel‑plated steel can withstands drops, vibrations, and the temperature swings typical of power tools and outdoor RC use.

Key Features

• Extreme High‑Drain Output: 30A Continuous / 40A Pulse
  Feeds the most demanding turbo flashlights, RC models, and power tools without voltage sag. 30A continuous keeps devices at full power; 40A pulse handles instantaneous startup surges.

• Genuine 4000mAh Capacity (14.4Wh)
  Provides useful runtime even in high‑current applications — about 10–15 minutes of continuous turbo in a flashlight, multiple RC heats, or dozens of tool operations per charge.

• Unprotected Flat‑Top Design — The Enthusiast Standard
  Flush positive terminal ensures a perfect fit in ultra‑tight flashlight tubes, recessed contacts, and spot‑welded packs. Eliminates the added length and resistance of a protection PCB. Requires a 4.2V Li‑ion charger and device with low‑voltage cutoff.

• Stable NMC Chemistry & Flat Discharge
  Maintains a consistent 3.6V nominal voltage with minimal sag. Light output, motor RPM, and tool torque stay predictable from fresh off the charger to nearly empty.

• Ultra‑Low Internal Resistance (≤18mΩ)
  Voltage drop at 30A is only ~0.54V. Keeps heat generation low and devices in regulation longer.

• 500+ Cycle Life & Low Self‑Discharge
  Recharge over 500 times with minimal capacity fade. Stores for months at ~3.6–3.7V, always ready for the next race, project, or outage.

• Multi‑Layered Passive Safety
  Built‑in PTC thermistor, resealable vent, and CID protect against over‑current, over‑pressure, and short circuits.

• Rugged Nickel‑Plated Steel Can
  Corrosion‑resistant and impact‑resistant. Withstands the vibrations, drops, and harsh conditions of power tools, RC vehicles, and outdoor use.

Technical Parameters

Applications

1. Turbo Flashlights & High‑Lumen Hot‑Rods
For flashlights pulling 15–30A on turbo — Emisar D4SV2, Noctigon KR1/K1, Fireflies, and custom FET‑driven builds — this flat‑top cell delivers the instantaneous current needed for maximum brightness without premature step‑down. The flush terminal ensures a perfect fit in the tightest battery tubes where button tops simply will not fit.

2. RC Cars, Trucks & Drones
Build a 2S or 3S Li‑ion pack for 1/10 and 1/8 scale vehicles. The 30A continuous discharge feeds brushless motors with relentless punch, while the flat‑top design allows clean, low‑profile spot welds for stick packs, saddle packs, and drone battery builds.

3. Cordless Power Tools
Replace worn‑out cells in drills, impact drivers, circular saws, and angle grinders. The high drain rate handles the startup spikes and heavy loads of professional tools, and the flat‑top terminal is the standard for welding into 5S1P or 5S2P configurations for 18V/20V platforms.

4. High‑Power Portable Fans & Cooling Devices
Large portable fans that draw 3–8A on high speed run powerfully and consistently with this cell. The flat top mates seamlessly with recessed contacts in many high‑output fan battery bays.

5. DIY High‑Current Power Banks & Inverters
Build a portable power station or high‑current power bank that can fast‑charge multiple devices. The flat‑top cell is ready for spot welding into series/parallel configurations without the interference of a button top.

6. Professional & Industrial Equipment
Portable barcode scanners, thermal printers, and medical devices that require both high current pulses and dependable runtime are well‑served by this flat‑top 4000mAh cell.

FAQ

Q1: Is this cell really capable of 40A? I see 30A continuous and 40A max.
A: Yes. The cell is rated for 30A continuous discharge and can safely pulse up to 40A for short bursts (under 5 seconds). We specify both figures so you know exactly what to expect. For applications that demand sustained 40A+, consider ultra‑high‑rate cells like the Samsung 30T or Molicel P42A.

Q2: Why is the battery unprotected and only available in flat top?
A: Delipow designed this cell specifically for high‑drain applications where a protection PCB would add unwanted length and resistance, and where a button top would prevent installation in tight compartments or interfere with spot welding. The flat top is the universal standard for enthusiast flashlights, power tool rebuilds, and custom battery packs. 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. The cell’s PTC, vent, and CID provide passive safety.

Q3: Will this flat‑top cell work in my flashlight if it originally had a button‑top battery?
A: It depends on the light. If your flashlight uses a spring‑loaded positive contact with a physical reverse‑polarity ring, a button top may be required to make contact. However, most high‑performance and enthusiast flashlights are designed specifically for flat‑top cells, as they offer lower resistance and a more compact fit. Check your device manual: if it specifies “flat top” or “unprotected flat top,” this cell will work perfectly. If the light has a mechanical polarity ring and the flat top doesn’t reach, you may need a button‑top cell instead.

Q4: Can I use this in a device that takes 18650 batteries?
A: No. A 21700 cell (21mm × 70mm) is physically larger than an 18650 (18mm × 65mm). Your device must explicitly support the 21700 form factor. Do not force a 21700 into an 18650 tube.

Q5: How does the 3.6V nominal voltage compare to 3.7V cells?
A: 3.6V and 3.7V are often used interchangeably for lithium‑ion cells; the actual voltage depends on the specific chemistry and manufacturer rating. This cell is fully compatible with all 3.7V nominal devices. You charge it to 4.2V and discharge to 2.5V, just like any standard Li‑ion cell.

Q6: How hot does the cell get at 30A continuous?
A: With ≤18mΩ internal resistance, heat generation is moderate. The cell will become warm — typically reaching 60–70°C after several minutes of sustained 30A — but stays within safe limits. Allow cooling between heavy discharge runs for best longevity.

Q7: Can I charge this battery at 4A?
A: Yes, 4A (1C) is the maximum charge current. 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.

Q8: How should I store spare cells?
A: In a plastic case or silicone sleeve, away from metal and moisture. For storage over one month, bring the voltage to ~3.6–3.7V (about 50% charge). Check every 3 months and recharge if below 3.0V. Never store fully depleted.

Q9: Can I fly with this battery?
A: Yes. At ~14.4Wh, it’s well under the 100Wh IATA limit. Carry in hand luggage with terminals insulated.