Introduction of Lithium Ion 21700 Batteries
Introduction of 21700 Batteries
What is a 21700 Battery?
A 21700 battery is a rechargeable lithium-ion cell with a cylindrical shape and standardized dimensions of 21mm in diameter and 70mm in length. It was developed as an improvement over the 18650 battery, offering higher capacity, better energy density, and improved efficiency, making it ideal for high-power applications such as electric vehicles and energy storage systems.
Technical Specifications
Chemistry: Like 18650 batteries, 21700 batteries come in various lithium-ion chemistries, including:
Lithium cobalt oxide (LiCoO₂ – LCO): High energy density but lower discharge rates.
Lithium manganese oxide (LiMn₂O₄ – LMO): Improved safety and thermal stability.
Lithium nickel manganese cobalt oxide (LiNiMnCoO₂ – NMC): Balanced energy density, power output, and safety.
Lithium iron phosphate (LiFePO₄ – LFP): Excellent safety and long cycle life but lower energy density.
Voltage: Typically 3.6V or 3.7V nominal, with a full charge voltage of 4.2V and a discharged state at 2.5V to 3.0V.
Capacity: Ranges from 3000mAh to over 5000mAh, depending on the chemistry and manufacturer.
Discharge rate (C-rating): Some 21700 cells are designed for high-drain applications, offering continuous discharge rates (CDR) up to 45A or more.
Cycle life: Can last between 500 to 1500+ charge cycles, depending on usage and chemistry.
21700 batteries are widely used in:
Electric vehicles, High-power consumer electronics, Power tools, including drills, saws, and industrial-grade equipment, Renewable energy storage, such as solar power storage systems and backup power supplies (UPS).
Are 21700 batteries safe?
High capacity lithium batteries usually require a PCB (Protection Circuit Board) or other kinds of protection (like a PTC aka Resettable Fuse, and a CID Pressure Valve) to limit over charging, discharging, high temperatures and internal pressure. Protected cells are great for high performance devices and electronics, and are commonly recommended or designed for specific compatible models to get the most consistent efficiency while keeping your device and battery safe with the on-board protection.
SuPower Battery offers customize 18650 and 21700 battery pack with protection circuit and specified output connector according to customers’ needs.
| Brand | Model | Rate | Capacity |
| Samsung | INR21700-40T | 35A | 4000mAh |
| Samsung | INR21700-50E | 9.8A | 5000mAh |
| Samsung | INR21700-50S | 25A | 5000mAh |
| Panasonic | NCR21700T | 30A | 4800mAh |
| Panasonic | NCR21700A | 15A | 5000mAh |
| Sony | US21700VTC6A | 30A | 4000mAh |
Size Comparison for battery cells:
