Protected 21700

9 products

📖 Click to view full specifications, comparison & safety guide

Protected 21700 Batteries – Built-in Overcharge, Over-Discharge & Short-Circuit Protection, High Capacity & Ready to Use

Welcome to our Protected 21700 collection. A Protected 21700 integrates a precision Protection Circuit Module (PCM/PCB) onto a standard high-capacity 21700 cell. It retains the massive 4000mAh–5000mAh capacity advantage of the 21700 platform while adding four critical safety layers: overcharge protection, over-discharge protection, overcurrent protection, and short-circuit protection. This collection is engineered for high-power flashlights, headlamps, outdoor lighting, DIY power bank kits, and a wide range of consumer electronics—delivering safe, plug-and-play performance without additional circuitry.

What is a Protected 21700? How Does It Differ from Unprotected Flat Tops?

A Protected 21700 features a circular protection PCB welded to the negative (or positive) terminal of the bare cell, enclosed within an extended heat-shrink wrapper. This PCB acts as an intelligent "circuit breaker" that continuously monitors voltage and current.

Feature	Protected 21700 (This Collection)	Unprotected Flat Top 21700
Length	~74.0mm – 76.5mm (varies by PCB)	~70.0mm – 71.0mm
Safety Features	Built-in overcharge, over-discharge, overcurrent, short-circuit protection	None; relies on external device or BMS
Target User	General consumers, flashlight users, DIY beginners	Pack builders, advanced hobbyists
Typical Applications	High-power flashlights, headlamps, outdoor lighting, power banks	Power tool packs, vaping, EVs
Charging	Recommended to use a quality Li-ion charger (dual redundancy)	Must use a proper Li-ion charger

Core Advantages

Overcharge Protection: Automatically cuts off charging current when cell voltage reaches 4.25V ±0.05V, preventing overheating, swelling, or thermal runaway caused by overcharging.
Over-Discharge Protection: Disconnects the load when cell voltage drops to 2.5V – 2.9V, preventing irreversible capacity loss or internal damage from deep discharge.
Overcurrent & Short-Circuit Protection: Instantly cuts power (within milliseconds) if discharge current exceeds the PCB threshold (typically 8A–10A) or if a short circuit is detected across the terminals.
Massive Capacity, Extended Runtime: Leveraging the 21700 platform, mainstream capacities reach 4000mAh–5000mAh—a single cell delivers hours of turbo runtime for high-lumen flashlights.
Button Top Design: Most Protected 21700 cells feature a raised positive terminal, ensuring compatibility with older flashlights and headlamps that require physical polarity protection or dual-flat contacts.
Ready to Use – No Extra Circuitry Needed: Ideal for most single-cell consumer devices that lack built-in low-voltage cutoff or protection features.

Typical Specifications (Protected 21700)

Specification	Typical Values
Nominal Voltage	3.6V – 3.7V
Full Charge Voltage	4.2V ±0.05V (PCB overcharge threshold 4.25V)
Discharge Cut-off Voltage	2.5V – 2.9V (enforced by PCB)
Capacity Range	4000mAh – 5000mAh (based on internal bare cell)
Max Continuous Discharge	8A – 10A (limited by PCB; not for high-drain use)
Total Cell Length	74.0mm – 76.5mm (verify device battery compartment)
Protection Functions	Overcharge, Over-discharge, Overcurrent, Short-circuit
Cycle Life	500 – 800 cycles
Operating Temperature	Charge: 0°C~45°C / Discharge: -10°C~60°C

Popular Protected 21700 Cell Models – Quick Reference

Model	Core Cell Brand	Nominal Capacity	Max Discharge	Length (Approx.)	Best For
Protected 21700 50E	Samsung	5000mAh	8A–10A	75mm–76mm	High-lumen flashlights, searchlights
Protected 21700 50S	Samsung	5000mAh	10A	75mm–76mm	High-power flashlights, portable medical devices
Protected 21700 P42A	Molicel	4200mAh	10A	74mm–75mm	Balanced capacity and moderate drain
Protected 21700 P45B	Molicel	4500mAh	10A	74mm–75mm	High capacity, high reliability
Protected 21700 40T	Samsung	4000mAh	10A	74mm–75mm	Flashlights needing moderate current headroom
Protected 21700 NCR21700A	Panasonic	4800mAh	8A	75mm–76mm	Industrial flashlights, medical devices

Note: Exact lengths are listed on individual product pages. Please verify before purchase.

Protected 21700 vs. NMC 21700 vs. IFR21700

Parameter	Protected 21700 (This Collection)	NMC 21700 (Unprotected)	IFR21700 / LiFePO₄
Nominal Voltage	3.7V (NMC core)	3.6V–3.7V	3.2V
Capacity Range	4000mAh–5000mAh	3000mAh–5000mAh	1800mAh–3000mAh
Max Continuous Current	8A–10A	8A–45A	3A–10A
Safety Features	Built-in 4-layer protection	Requires external circuit	Inherently safe
Length	74mm–76.5mm	70mm–71mm	70mm–71mm
Target Audience	Consumers, plug-and-play	Pack assemblers, high-drain devices	Solar storage, safety-critical

⚠️ Important Compatibility & Sizing Notes

Increased Length – Verify Fitment: Protected 21700 cells are approximately 4mm – 6.5mm longer than standard 70mm flat top cells. Please measure your device's battery compartment before purchase. Tight-fitting flashlights or chargers may not accommodate the extra length.
Not Suitable for Ultra-High-Drain Devices: The protection PCB in this collection typically limits continuous discharge to 8A–10A. If your device requires 15A+ continuous current (e.g., high-power vape mods, professional power tools), the PCB will frequently trip. Please visit our NMC 21700 collection for unprotected high-current cells and use an appropriate external BMS or protected device.
Recommended Charger: While the cell features built-in overcharge protection, we strongly recommend using a quality brand-name Li-ion charger with its own overcharge protection for redundant safety.

Typical Applications

Application	Recommended Protected Cell	Why Protected
High-Power LED Flashlights / Tactical Lights	5000mAh, Button Top, 10A	Single-cell extended runtime, prevents over-discharge
Headlamps / Bike Lights / Camping Lanterns	4000mAh–5000mAh, Button Top	Overnight use; over-discharge protection is critical
DIY Power Bank Kits	5000mAh, Button Top	Provides stable, protected 3.7V input to the PCB
Outdoor Searchlights / Spotlights	5000mAh, 10A	High capacity supports extended high-output searching
Portable Medical Devices (Non-Life-Support)	4800mAh–5000mAh	Stable output with built-in safety redundancy
Industrial Inspection Flashlights / Headlamps	4000mAh–5000mAh	Long runtime, safe and reliable, fewer battery changes

Why Choose Our Protected 21700 Batteries?

Premium Grade-A Core Cells: Internal cells sourced from Samsung, LG, Panasonic, Molicel, and other Tier-1 manufacturers, ensuring genuine capacity and long cycle life.
High-Quality Protection PCB: Utilizes protection ICs from Seiko, Ricoh, and low-RDS(on) MOSFETs for precise protection thresholds and ultra-low quiescent current (<10μA).
Robust Welding Process: Nickel-plated steel strips are precision spot-welded between the cell and PCB, ensuring minimal contact resistance and no risk of cold solder joints.
100% Factory Testing: Every Protected 21700 undergoes full inspection for voltage, internal resistance, and functional verification of protection features before shipment.
Clear Dimensional Labeling: Product pages clearly state the actual total length (e.g., 75.2mm / 76.0mm) to help you verify compatibility with your device.
Safety Certified: CE, RoHS, UN38.3 certified. MSDS documentation provided with every shipment.

👇👇👇 Browse the product list below to select the ideal Protected 21700 based on required capacity and device battery compartment length. If unsure about compatibility, please contact customer service with your device model for dimensional guidance.

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