Is It Better To Choose 18650 Or 21700 Battery For Electric Bicycles

Electric bicycles have gained immense popularity over the past decade, offering a more sustainable and cost-effective alternative to traditional transportation. Central to the performance of these bikes are the batteries that power them, influencing everything from range and speed to overall durability. Among the different types of lithium-ion battery cells, the 18650 and 21700 are the most commonly used for e-bikes.

So, which one is better for your electric bike: the smaller, more established 18650 battery or the newer, larger 21700 cell? In this article, we will compare both types of batteries to help you make an informed decision based on factors such as performance, cost, and battery longevity.

Basic Overview of 18650 and 21700 Batteries

• 18650 Battery: The 18650 battery is one of the most widely used lithium-ion battery cells. It measures 18mm in diameter and 65mm in length, hence the name "18650." With a typical capacity ranging from 2500mAh to 3500mAh, the 18650 has been a staple in the world of consumer electronics, powering devices like laptops, flashlights, and even electric vehicles in their earlier models.
• 21700 Battery: The 21700 battery is a newer format that measures 21mm in diameter and 70mm in length. Thanks to its larger size, the 21700 can hold a greater energy capacity, typically up to 5000mAh. Due to this improved energy density, the 21700 battery is increasingly becoming the preferred choice in high-performance applications, such as electric vehicles (EVs) and electric bicycles, where longer ranges and higher power outputs are necessary.

While both batteries are lithium-ion, their size and energy storage capacity are what set them apart in the electric bicycle industry.

Key Parameter Comparison

When it comes to choosing the right battery for your e-bike, several key factors come into play. Below, we compare the 18650 and 21700 cells on important parameters such as size, capacity, energy density, and discharge rates.

Size and Capacity:

• 18650: With a diameter of 18mm and a length of 65mm, the 18650 battery typically offers a maximum capacity of around 3500mAh. It is compact and lightweight, making it ideal for smaller devices or applications that don't require as much power or energy.
• 21700: In contrast, the 21700 battery, measuring 21mm in diameter and 70mm in length, can store up to 5000mAh of energy. Its larger size allows it to provide more energy, which translates to longer riding ranges for electric bicycles.

Energy Density: The 21700 battery has a higher energy density than the 18650 battery, meaning that it can store more energy within the same volume. This results in a greater range per charge, making it an attractive option for e-bike riders who need to go further without frequent recharging. The energy density of the 21700 is approximately 20% higher than that of the 18650, giving it a significant advantage when it comes to long-distance performance.

Discharge Rate: Both the 18650 and 21700 batteries have a high discharge rate, meaning they can release power quickly without compromising safety. However, the 21700 battery is better suited for handling higher output currents due to its larger size and higher energy capacity. This is particularly beneficial for e-bikes that require consistent power delivery during acceleration or when tackling uphill terrains.

Advantages and Disadvantages of 18650 Battery

Advantages:

High Consistency: The 18650 battery has been around for a long time and has been widely tested, particularly in consumer electronics. This means it is known for its stability and reliability.

Cost-Effective: Due to its smaller size and more established production processes, the 18650 is typically more affordable than the 21700. This makes it an attractive choice for e-bike manufacturers and consumers on a budget.

Wide Compatibility: The 18650 cell is versatile and can be used in a wide range of devices, from laptops and cameras to electric bikes. Its compact size allows it to fit into smaller battery packs, which is ideal for certain e-bike models where space is limited.

Disadvantages:

Lower Capacity: The main downside of the 18650 battery is its limited capacity compared to the 21700. With a maximum capacity of around 3500mAh, it may not provide as long a riding range on a single charge, especially on more powerful e-bikes.

Shorter Range: The lower capacity directly impacts range, and for long-distance riders or those who require higher power output, the 18650 might not be ideal.

Limited Performance: While the 18650 is perfectly sufficient for light to moderate e-bikes, it may struggle to provide consistent power for high-performance e-bikes or more demanding terrains like steep hills or rough trails.

Advantages and Disadvantages of 21700 Battery

Advantages:

Higher Capacity: The 21700 battery can hold up to 5000mAh, which allows it to provide more energy and longer riding distances. This is particularly useful for long-distance commuters or those who use their e-bikes for recreational long rides.

Better Energy Density: Thanks to its higher energy density, the 21700 can store more power within the same space, making it an ideal option for riders who need both endurance and efficiency.

Higher Discharge Rate: With the ability to handle higher currents, the 21700 battery is suitable for high-performance e-bikes, where smooth acceleration and high power are essential. It performs better on steep inclines or during rapid acceleration.

Improved Thermal Management: The larger size of the 21700 battery helps dissipate heat more effectively, improving both safety and performance, especially under load.

Disadvantages:

Higher Cost: Due to the larger size and more complex manufacturing processes, the 21700 battery tends to be more expensive than the 18650. This can increase the overall cost of the e-bike, making it less accessible for budget-conscious consumers.

Increased Weight: The 21700's larger size and higher energy capacity make it heavier than the 18650. This can result in a slightly bulkier e-bike, which might affect handling or rider comfort, particularly for those looking for lightweight models.

Limited Compatibility: Since the 21700 is a newer format, it may not be compatible with all existing e-bike designs. Some smaller e-bike frames might not have the space to accommodate a 21700 battery, which could limit its application to certain models or high-performance bikes.

18650 vs 21700: A Comprehensive Comparison

Now that we've looked at the advantages and disadvantages of both the 18650 and 21700 batteries, it's time to compare them head-to-head across several important factors:

Applications and Market Positioning of 18650 and 21700 Batteries

When choosing between the 18650 and 21700 battery for electric bicycles, it's essential to consider not just technical specifications but also their intended use cases and market positioning. Both batteries have distinct advantages depending on the specific requirements of the rider or manufacturer.

Applications of 18650 Battery in Electric Bicycles

• Compact E-Bikes: The 18650 battery is ideal for smaller, more compact electric bicycles that prioritize portability and maneuverability. Its lighter weight and smaller form factor make it suitable for folding bikes or e-bikes designed for urban commuting, where range demands might be more modest.
• Entry-Level and Budget-Friendly Models: Many entry-level or budget-conscious e-bike models feature the 18650 battery due to its lower cost and adequate performance for lighter, casual use. For riders who only need a short-range commute or occasional leisure ride, the 18650 offers a solid, cost-effective solution.
• Applications Requiring Smaller Footprints: In some e-bike designs where battery space is constrained, the smaller 18650 format is an obvious choice. It allows manufacturers to fit battery packs into tighter spaces without sacrificing too much on power delivery.

Applications of 21700 Battery in Electric Bicycles

• Long-Range and High-Performance E-Bikes: The 21700 battery is more commonly found in premium e-bike models designed for long-distance riders, high-performance enthusiasts, and commuters who need longer ranges. With its higher capacity and energy density, the 21700 is ideal for e-bikes that require extended power for all-day rides or longer trips without frequent recharging.
• Off-Road and Mountain E-Bikes: The larger size and superior power output of the 21700 battery also make it suitable for off-road and mountain bikes that demand higher energy for challenging terrain. The 21700's ability to provide higher current outputs and better thermal management ensures smooth power delivery even during intense riding sessions.
• Premium and High-End E-Bikes: As the cost of the 21700 battery is higher, it tends to be used in high-end, feature-rich e-bikes equipped with advanced motors, integrated systems, and the latest technology. These bikes cater to riders seeking top-tier performance, better efficiency, and cutting-edge features.

Market Positioning

• 18650 Battery: The 18650 is generally positioned as a more affordable and versatile option, suitable for a wide range of e-bike models. It is widely used in entry-level bikes, folding bikes, and urban commuters, where affordability and a reasonable range are more important than extreme performance.
• 21700 Battery: In contrast, the 21700 is positioned as a premium offering in the e-bike market. It is aimed at riders who prioritize long-range travel, high performance, and reliability, with higher-end models often using this battery type. Due to its superior capacity and efficiency, it is well-suited for riders who require more robust power output and extended battery life.

Future Trends of 18650 and 21700 Batteries

As the e-bike market continues to evolve, so too do the demands placed on battery technology. Both the 18650 and 21700 battery types are likely to experience changes in the near future, driven by advancements in battery chemistry, manufacturing techniques, and market trends.

Evolution of Battery Chemistry and Technology

• Improved Energy Density: Both the 18650 and 21700 cells are likely to see improvements in energy density as new lithium-ion chemistries (such as lithium nickel cobalt manganese oxide (NCM) and lithium iron phosphate (LiFePO4)) become more common. These improvements could help both batteries store more energy within the same size, further enhancing their range and performance.
• Solid-State Batteries: The future of lithium-ion batteries could also include solid-state technology, which promises even higher energy densities and faster charging times. If solid-state batteries become mainstream, both the 18650 and 21700 formats could benefit, offering even better performance for e-bikes in the coming years.

Cost Reductions and Affordability

• As the production scale of 21700 batteries increases, costs are expected to fall, making them more accessible for a wider range of e-bike manufacturers and riders. This could lead to more competitive pricing and possibly make the 21700 battery more common in mid-range e-bike models.
• Similarly, as the 18650 battery remains a staple in many industries, its cost-effectiveness is expected to continue. Innovations in manufacturing and supply chain improvements could make the 18650 more affordable, while still offering reliable performance for budget-conscious riders.

Market Shifts and E-Bike Trends

Longer Ranges and High-Performance Features: With increasing interest in long-distance cycling and off-road adventures, demand for higher capacity batteries like the 21700 is expected to rise. As electric bikes become more capable of longer trips and higher speeds, riders will demand batteries that can keep up with these advancements.

Urban Commuting and Foldable E-Bikes: On the flip side, urban commuters and riders of foldable bikes will continue to benefit from the 18650's compact size and lighter weight. As cities push for cleaner transportation solutions, the demand for smaller, lightweight e-bikes powered by 18650 batteries could grow.

Conclusion

Choosing between the 18650 and 21700 battery for your electric bicycle ultimately depends on your specific needs, preferences, and budget. The 18650 battery, with its long-standing reputation and lower cost, remains a great choice for riders who don't require extreme range or power output. It suits urban commuters, budget-friendly e-bikes, and those who prioritize lightweight designs.

On the other hand, the 21700 battery, with its higher energy density, capacity, and discharge rate, is better suited for long-distance riders, off-road enthusiasts, and those seeking high performance. While it comes with a higher upfront cost and increased weight, the 21700's advantages in range and power output make it a top choice for serious cyclists and premium e-bike models.

Looking ahead, we can expect both battery types to continue evolving, with advancements in energy density, manufacturing, and affordability shaping the future of electric bicycles. Whether you opt for the 18650 or 21700, understanding their strengths and applications will help you make the best decision for your e-bike needs.

Choose GEB for Safe, High-Performance Lithium Batteries for Your Electric Bicycle!

At General Electronics Technology Co., LTD (GEB), we specialize in manufacturing top-tier lithium batteries for electric bicycles. With over 15 years of experience, our advanced plastic shell technology ensures superior safety, enhanced thermal management, and excellent low-temperature charging performance. As a leading manufacturer with over 180 employees and annual sales surpassing $30 million, we are committed to delivering high-end, reliable batteries that are trusted by customers worldwide.

Our lithium iron phosphate (LiFePO4) batteries offer unparalleled safety-with no reported safety incidents since our founding in 2009. When you choose GEB, you choose quality, innovation, and peace of mind.

Contact us today to learn more about how our batteries can power your e-bike safely and efficiently. Choose GEB-where safety meets performance.(sales@gebattery.co)