What is an 18650 Lithium Battery?

The 18650 battery is a standard cylindrical lithium-ion cell. It is widely used because of its stable size, safe performance, and low cost. It can be made into battery packs for electronics, power tools, vehicles, and energy storage.

1. 18650 Naming Rules & Size

• 18: diameter = 18 mm
• 65: length = 65 mm
• 0: cylindrical shape

All brands use the same standard size, so 18650 cells are interchangeable.

2. Core Specifications

• Nominal Voltage: 3.6V / 3.7V
• Full Charge: 4.2V
• Discharge Cut-off: 2.5V – 3.0V
• Capacity: 2000mAh – 3500mAh
• Working Temp: Charge 0~45℃, Discharge -20~60℃
• Cycle Life: 500 – 2000 times

3. Main Types of 18650 Battery

4. Main Advantages

• Standard size, universal use
• Safe and good heat dissipation
• Easy to make battery packs (series/parallel)
• Low cost, easy to replace bad cells
• Mature supply chain

5. Common Applications

• Electronics: laptops, power banks, flashlights
• Power tools: drills, grinders, vacuum cleaners
• Transport: e-bikes, scooters, early EVs
• Energy storage: solar systems, outdoor power stations

6. Safety Notes

• Bare 18650 cells have no protection — use BMS board
• Do not discharge below 2.5V
• Do not disassemble, puncture, or heat
• Use proper lithium battery charger

7. 18650 vs 21700

• 18650: small, low cost, universal
• 21700: bigger, higher capacity, for high-end devices