When it comes to deciding on the right battery for your UAV, UAS, or robotics needs, the choice between 18650 and 21700 lithium-ion cylindrical cells can be just as tricky as choosing between LiPo and Li-Ion batteries. Fortunately, MaxAmps is here to help.
Pros of Li-ion 18650 Cells
• Availability and Cost: The 18650 cell has been a reliable and widely used standard for years, making it easy to find and integrate into various applications. Given its widespread use, 18650 cells are often more affordable and available, providing flexibility in budgeting for your project.
• Compact Size and Versatility: The 18650's smaller cell size compared to the 21700 makes it more suitable for compact builds where space is limited.
• Lower Weight: That smaller size also means lighter weight, which is often preferred in situations where minimizing weight is crucial, such as UAVs designed for agility, speed, or both.
Cons of Li-Ion 18650 Cells
• Lower Capacity: Compared to the 21700, the 18650 has a smaller energy capacity, usually offering less runtime. This would often come into play for endurance-oriented applications where longer battery life is crucial.
• Lower Discharge Rates: While the 18650 is a flexible option, it may not handle high current as efficiently as the 21700. For your applications requiring more power, this can mean lower voltage under load and reduced performance.
• Heat Management: Because of its compact size, the 18650 can heat up quickly in heavy discharge conditions, requiring additional thermal management solutions in high-performance builds.
Pros of Li-Ion 21700 Cells
• Higher Energy Density: The 21700 cell offers a higher energy density (Wh/kg) compared to the 18650, allowing for longer runtimes and higher capacity. This is ideal for UAVs, or robotics where extended operational time is a priority.
• Higher Discharge Capacity: The larger format allows the 21700 to handle higher current draws more effectively, maintaining stable voltage under intense load for longer. This is beneficial for high-power applications that demand consistent performance.
• Improved Thermal Performance: Thanks to its increased surface area and volume, the 21700 can better disperse heat buildup, making it a safer option for projects with higher power demands.
Cons of Li-Ion 21700 Cells
• Larger Size and Weight: That increased capacity and power of the 21700 do not come for free. That extra boost needs extra space, and the 21700 allows that by coming in at 68g per cell, (22g more than an 18650 cell) and an extra 5mm in length. This can often conflict with projects that require more compact power solutions.
• Higher Cost: While the 21700 offers more power, the cost-per-cell is often higher than the 18650. Budget conscious builders or those working on smaller-scale projects might find the 18650 a cheaper option.
• Limited Compatibility: Given the larger dimensions and slightly less universal applications, the 21700 might not fit into setups designed for 18650 cells or, alternatively, could require additional modification to fit in your setup.
Conclusion
When deciding between Li-Ion 18650 and 21700 batteries, it’s crucial to consider your application’s needs. If you need a compact, lightweight, and cost-effective solution, the 18650 is a fantastic choice. However, if you prefer longer runtimes, higher energy density, and improved thermal management, the 21700 might fit your needs better.
Are you still unsure which battery is right for your project? Reach out to our Battery Tech Team for personalized guidance—click here to contact us. We want to help you power up your project with the perfect battery!
