The 21700 3.7V 4000mAh Rechargeable Liquid Battery Long Cycel is developed for applications where higher energy density and longer runtime are required. Its larger cylindrical structure provides more active material space compared with conventional 18650 cells, allowing manufacturers to achieve greater battery capacity with fewer cells in the same application.
With stable discharge characteristics and strong structural reliability, this 21700 cell is suitable for battery pack designs requiring continuous power output. The standardized cylindrical format also simplifies pack integration and enables flexible series and parallel configurations according to different voltage and capacity requirements.
| Item | Specification |
| Model | 21700 |
| Material | Li-ion Polymer Battery |
| Normal Capacity (0.2C) | 4000mAh |
| Minimum Capacity (0.2C) | 4000mAh |
| Energy | 14.8Wh |
| Normal Voltage | 3.7V |
| Delivery Voltage | 3.7V ~ 4.2V |
| Standard Charge Method | Charge at maximum current. When the battery or pack terminal voltage reaches the charging limit voltage, charge at constant voltage until the charging current is less than or equal to 0.02 C, then stop charging. |
| Discharge Program | The battery or the battery pack carries on the constant current discharge with the maximum discharge current to the discharge termination voltage. |
| Max Charging Current | 1C CC/CV → 0.02C cutoff |
| Max Discharging Current | 1C CC/CV → 3.0V cutoff |
| Over-Discharging Current | 3.0V |
| Operation Temperature Range |
Charging: 0°C ~ 50°C Discharging: -20°C ~ 60°C |
| Allowable Maximum Surface Temperature |
Charging: Tmax ≤ 50°C Discharging: Tmax ≤ 60°C |
| Storage T/H Range (time) |
-20°C ~ 60°C (Less than 1 month) -20°C ~ 45°C (Less than 3 months) -20°C ~ 25°C (Less than 1 year) |
| Cycle Life |
≥ 300 times (Thickness expansion rate ≤ 10%) ≥ 500 times (Thickness expansion rate ≤ 12%) |
The main advantage of the 21700 3.7V 4000mAh Rechargeable Liquid Battery Long Cycel is its improved capacity-to-size ratio. Compared with traditional 18650 cells, the larger cell format helps battery manufacturers increase total energy storage while optimizing pack structure.
For high-power applications, stable internal resistance and optimized electrode design contribute to more consistent current output and reduced performance fluctuation during operation. This makes the cell suitable for equipment requiring longer working time and frequent discharge cycles.
21700 cells are commonly selected for power-demanding applications because of their ability to maintain stable voltage output under continuous load.
Yideng applies strict cell grading procedures based on capacity, voltage and internal resistance to improve consistency when multiple cells are assembled into battery packs.
Better cell matching helps reduce imbalance between individual cells and improves the reliability and service life of finished battery systems.
The 21700 3.7V 4000mAh Rechargeable Liquid Battery Long Cycel is designed for manufacturers developing high-capacity rechargeable battery systems.
Used in portable power stations and backup energy solutions requiring longer operating time and reliable energy output.
Suitable for cordless tools and professional equipment requiring high-power discharge capability.
Applied in electric bicycles, scooters and other lightweight mobility devices requiring compact but powerful battery systems.
Used in outdoor lighting, camping power equipment and portable electrical products requiring extended runtime.
A full range of official certifications is available for our lithium batteries. Our cells comply with BIS, UL1642, UN38.3, IEC62133, CE, CB, RoHS standards, accompanied by MSDS documents. We hold KC certification for South Korea and independent invention patents. All test reports come from accredited third-party testing institutions. We can supply all certification materials to facilitate customs clearance and local product registration for global partners.
Failure to observe the following precautions may result in battery leakage, explosion or fire.
--- Do not immerse the battery in water or allow it to get wet.
--- Do not use or store the battery near sources of heat such as a fire or heater.
--- Do not reverse the positive (+) and negative (-) terminals.
--- Do not connect the battery directly to wall outlets or car cigarette-lighter sockets.
--- Do not put the battery into a fire or apply direct heat to it.
--- Do not short-circuit the battery by connecting wires or other metal objects to the positive (+) and negative (-) terminals.
--- Do not place the battery in a microwave oven or pressurized container.
--- Do not use the battery in combination with primary batteries (such as alkaline batteries) or batteries of different capacity, type or brand.
--- Do not use the battery if it gives off an odor, generates heat, becomes discolored or deformed, or appears abnormal in any way. If the battery is in use or being recharged, remove it from the device or charger immediately and discontinue use.
--- Do not pierce the battery casing with a nail or other sharp object, break it open with a hammer, or step on it.
--- Do not attempt to disassemble the battery in any way.
--- Keep the batteries out of the reach of children. If a child somehow swallows a battery, seek medical attention immediately.
--- If the battery leaks and electrolyte gets in your eyes, do not rub them. Rinse them with clean running water and immediately seek medical attention. If left as is, electrolyte can cause eye injury.
--- The isolated measures are needed between battery (the bare Al layer at side and top sealing) and the PCB, and also between battery and electric equipment, especially avoid the Al layer in packing foil contact to cathode or anode (including electric equipment), otherwise this can cause battery leakage or swelling.
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