18650 vs 21700 Batteries: Which One is Right for You?

by Mike Beard in Battery Knowledge Base

Lithium-ion batteries come in various sizes, but two of the most commonly used types are the 18650 and 21700 cells. These batteries power everything from flashlights and laptops to electric vehicles and drones or robotics. While both share similar technology, they have key differences in size, capacity, and performance. Let’s break down the differences between 18650 and 21700 batteries to help you choose the right one for your application.

Size and Dimensions

  • 18650 Battery: 18mm diameter, 65mm length

  • 21700 Battery: 21mm diameter, 70mm length

The 21700 is slightly larger in both diameter and length, which directly impacts its energy storage and power output.

Capacity and Energy Density

  • 18650: Typically ranges from 2000mAh to 3500mAh

  • 21700: Typically ranges from 3000mAh to 5000mAh

Because of its larger size, the 21700 battery can store more energy than an 18650. This means longer runtimes and higher energy density, making it ideal for high-drain applications.

Performance and Power Output

  • 18650: Average Max discharge rate of 10A to 35A (varies by model)

  • 21700: Average Max discharge rate of 20A to 50A (varies by model)

The 21700 battery generally supports a higher discharge rate, meaning it can deliver more power, which is especially beneficial for high-performance applications like electric vehicles and drones or robotics.

Lifespan and Durability

  • 18650: Typically lasts 300-500 charge cycles

  • 21700: Typically lasts 500-1000 charge cycles

The 21700 battery often has a longer lifespan due to improved internal design and higher energy capacity, making it a better long-term investment.

Weight and Portability

  • 18650: Weighs around 45g

  • 21700: Weighs around 70g

While the 21700 battery offers more power and capacity, it is also heavier. If weight is a critical factor, the 18650 may be a better option for portable applications.

Which Battery Should You Choose?

  • Choose 18650 if: You need a smaller, lighter battery for applications like flashlights, laptops, or DIY electronics.

  • Choose 21700 if: You need more power, longer battery life, and better performance for demanding applications like electric vehicles, e-bikes, or drones or robotics.

Conclusion

Both the 18650 and 21700 batteries are excellent choices, but the right one depends on your specific needs. The 18650 battery is more compact and widely available, while the 21700 battery provides higher capacity, better performance, and a longer lifespan. If you need help selecting the best battery for your application, feel free to reach out to our team!

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