An 18650 battery is a rechargeable lithium-ion (Li-ion) cell characterized by its cylindrical shape and standardized dimensions of 18mm in diameter and 65mm in length. It is one of the most commonly used battery types in high-drain devices due to its high energy density, long lifespan, and efficiency compared to other rechargeable batteries.
Technical Specifications
Chemistry: Most 18650 batteries use lithium-ion chemistry, but there are variations such as:
Lithium Cobalt Oxide (LiCoO₂ - LCO): High energy density but lower discharge rates.
Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂ - NMC): A balance between energy density, power output, and safety.
Lithium Iron Phosphate (LiFePO₄ - LFP): Extremely safe with a 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–3.0V.
Capacity: Ranges from 1200mAh to over 3500mAh, depending on the chemistry and manufacturer.
Discharge Rate (C-Rating): Some 18650 cells are designed for high-drain applications, offering continuous discharge rates (CDR) up to 30A or more.
Cycle Life: Depending on the type, an 18650 battery can last between 300 to 1000+ charge cycles before noticeable degradation.
Protected vs. Unprotected Cells
Protected 18650 Batteries: Equipped with a protection circuit that prevents overcharging, over-discharging, and short-circuiting. These are often slightly longer (~70mm).
Unprotected 18650 Batteries: Do not have built-in safety mechanisms and are mainly used in battery packs with external Battery Management Systems (BMS).
Common Applications
18650 batteries are widely used in:
Consumer Electronics: Laptops, flashlights, vapes, and power banks.
Electric Vehicles (EVs) & E-Bikes: Tesla and other manufacturers use them in battery packs.
Power Tools: Drills, saws, and industrial equipment.
Energy Storage Systems: Solar power banks and uninterruptible power supplies (UPS).
Physical Variations
Some 18650 batteries have additional features that affect their size and compatibility:
Button Top vs. Flat Top: Button top batteries have an extended positive terminal, while flat tops are flush.
Protected vs. Unprotected: Protected cells are longer due to built-in circuitry.
If using an 18650 battery in a specific device, always verify the required specifications with the manufacturer to ensure proper fit and performance.
