21700 Battery: A Complete Guide

What is the 21700 Battery?

The 21700 battery is a rechargeable lithium-ion battery with a cylindrical shape, measuring 21 mm in diameter and 70 mm in length. It has a nominal voltage of 3.6V to 3.7V and is increasingly popular for its higher capacity, making it ideal for high-drain devices like flashlights. With a capacity ranging from 3000mAh to 5100mAh, the 21700 battery offers up to 42% more capacity than the 18650 battery.

Its energy density is around 300Wh/kg, surpassing the 18650's 250Wh/kg. Weighing between 60g and 80g, it typically takes about 4 hours to charge, depending on the charger and battery type. Available in both protected and unprotected variants, protected 21700 batteries include a built-in protection circuit to prevent overcharging and over-discharging. The battery can withstand between 300 to 2000 recharge cycles and is commonly used in devices such as flashlights, electronics, laptops, vaping devices, power tools, and some electric vehicles.

21700 Battery Features

The 21700 battery is a rechargeable lithium-ion battery with a cylindrical shape, 21 mm in diameter and 70 mm in length. It typically has a voltage between 3.6V and 3.7V. Below are the key features of the 21700 battery:

Capacity: It can hold 5000mAh or more, higher than the 18650 battery. The capacity can vary, ranging from 3000mAh to 5100mAh.

Energy density: The 21700 batteries have an energy density ranging from 250 Wh/kg to 300 Wh/kg.

Size and weight: The battery's dimensions are 70 mm in length and 21 mm in diameter3. The weight typically ranges from 50 to 70 grams.

Voltage: The voltage of a 21700 battery typically varies between 3.6V to 3.7V when it’s in use.

Types: 21700 batteries can be protected or unprotected2. Protected 21700 batteries generally have a button top, while unprotected ones typically have a flat top.

Charge cycles: A 21700 battery can last between 500 to 1000 charge cycles, depending on its chemistry, usage, and maintenance.

The 21700 battery is used in devices such as electric vehicles, flashlights, and power tools.

21700 Battery Dimensions

21700 Battery Specifications

21700 Battery Applications

21700 batteries are lithium-ion rechargeable cells with a diameter of 21mm and a length of 70mm. They are used in various high-demand applications due to their high energy density, long lifespan, and reliable performance. Below are some common applications of the 21700 Battery:

Electric Vehicles (EVs): Due to their high energy density and ability to provide a long driving range on a single charge, 21700 batteries are utilized in electric cars (like Tesla), e-bikes, and e-scooters. Tesla reported that after using 21700 battery packs, battery capacity increased by 35%, and energy density increased by about 20%.

Portable Electronics: Many portable devices like laptops, flashlights, power banks, and vape mods are powered by 21700 batteries because they provide a high capacity in a compact size. High-performance flashlights utilize 21700 cells for extended run times.

Energy Storage: 21700 batteries are used in energy storage systems for renewable energy applications, such as solar and wind power systems.

Power Tools: Companies like DeWalt and Makita use 21700 cells in their cordless power tools for improved runtime and power output.

Drones: Drones that need extended flight times and higher power output rely on 21700 batteries for their long-lasting power.

Motorcycle battery power supply: Motorcycle charging systems use a battery to provide power for starting the bike and to buffer electric energy. The battery is charged by a generator driven by the engine.

Compared to 18650 batteries, 21700 batteries have a higher energy density and capacity, typically ranging from 4000mAh to 5000mAh. Although 21700 batteries are more expensive and larger than 18650 batteries, their advantages make them suitable for high-power devices.

21700 Battery Equivalent

The 21700 battery has become increasingly popular due to its optimal balance between size and capacity, making it ideal for high-drain applications. While 18650 batteries remain widely used, the 21700 offers higher capacity in a slightly larger form factor. The 20700 battery serves as a close alternative, while the 26650 provides even greater capacity at the cost of increased size. Each battery type has its specific applications, with the 21700 being particularly favored in electric vehicles and high-performance power tools due to its excellent energy density and discharge capabilities.

Advantages of Using 21700 Battery

Compared to its predecessor, the 18650 battery, the 21700 battery provides a higher energy density, a longer lifespan, and greater power output. The 21700 battery measures 21mm in diameter and 70mm in length, while the 18650 battery measures 18mm in diameter and 65mm in length. Below are some advantages of 21700 batteries:

Higher Capacity: The 21700 typically offers a capacity between 3000mAh and 5000mAh, while the 18650 ranges from 1200mAh to 3500mAh. The 21700 battery can reach a maximum capacity of 5000mAh, a 42% increase from the 18650.

Improved Efficiency: With its higher capacity, fewer cells are needed to achieve the same battery pack size, which reduces complexity.

Better Thermal Management: The 21700 cells handle heat more effectively because their larger size spreads heat over a greater area, leading to better performance and safety, especially under high loads.

Longer Lifespan: Enhanced thermal management and energy density contribute to a longer overall battery lifespan. The 21700 allows for better performance over more charge cycles compared to 18650 cells.

Enhanced Performance: E-bikes with 21700 battery packs often experience more consistent power delivery, which translates to smoother acceleration and better handling, especially on challenging terrains.

Cost-Effective: 21700s are cheaper relative to capacity and simplify the building of battery packs. The price of the 21700 lithium battery pack is expected to be lower than the 18650 battery pack.

Higher Energy Density: 21700 batteries typically have an energy density ranging from 250 Wh/kg to 300 Wh/kg, a notable improvement compared to 18650 batteries, which usually offer around 180 Wh/kg to 250 Wh/kg. The 21700 battery's power density can increase by 20% or more compared to the 18650.

The high energy density and reliability of the 21700 make it versatile across various industries and ideal for high-drain applications like electric vehicles.

21700 vs 18650 Battery

The 21700 and 18650 batteries are both widely used lithium-ion battery types but differ significantly in terms of size, capacity, and performance. The 21700 battery is larger, with a higher capacity (up to 5000mAh) and better energy density (around 300Wh/kg) compared to the 18650's maximum capacity of 3500mAh and energy density of 250Wh/kg. This means the 21700 battery is better suited for high-power, high-drain applications like electric vehicles (EVs), power tools, and devices requiring extended usage times. It can also handle higher power outputs, up to 1400 watts, which is advantageous for applications that demand significant power.

On the other hand, the 18650 battery is more affordable and commonly used in smaller devices like flashlights and portable gadgets. It generally has a lower energy density, but its smaller size and cost-effectiveness make it ideal for less power-hungry applications. Additionally, there are more devices compatible with the 18650 battery, making it more accessible and versatile in the market.

The 21700’s higher energy density also results in longer battery life for devices like the Fenix HT18 hunting flashlight, which can provide brighter and more sustained lighting than the 18650. However, the larger size and higher cost of the 21700 might make it less suitable for applications where cost and space are primary concerns.

Comparison between 18650, 26650, and 21700 batteries

Here is the comparison between the 18650, 26650, and 21700 batteries:

Summary

The 18650, 26650, and 21700 batteries are each unique in their size, capacity, and power requirements, which render them suitable for a variety of applications.

• 18650 batteries are the most compact and are frequently employed in consumer electronics, including laptops, flashlights, and vaporizer devices. They are widely available and affordable, and they provide a dependable solution for low-to-medium power applications. Nevertheless, they possess the lowest capacity and lifespan in comparison to the other two sizes.
• 26650 batteries are larger and have a higher capacity, with a capacity spanning from 4000mAh to 6000mAh. They are optimal for high-drain applications, including solar energy storage systems, power tools, and electric vehicles. They are appropriate for devices that necessitate high output and extended runtime due to their capacity to manage continuous power draw. However, they are generally more expensive and less prevalent than the 18650.
• 21700 batteries provide a balance between capacity and dimensions, with a typical range of 4000mAh to 5000mAh. Power-hungry applications such as electric vehicles and advanced flashlights, they are acquiring popularity in consumer electronics and electric vehicles, as they offer superior performance compared to 18650 batteries. The 21700 battery is becoming a new standard for high-performance devices due to its higher discharge rate and lifespan of 500-800 cycles, which surpasses that of the 18650.

In conclusion, the 18650 is the most cost-effective and widely accessible option for low-to-medium power requirements. For high-power applications, the 26650 and 21700 are more appropriate. The 21700 is a more recent technology with more sophisticated chemistries and is increasingly being used in electric vehicles and other high-drain devices.

Are 21700 and 18650 Batteries interchangeable?

While you can use a 21700 battery instead of an 18650, ensure your device supports it. The 21700 is larger (21mm x 70mm) than the 18650 (18mm x 65mm), so it may not fit in all devices. Always check specifications before replacing batteries. From a chemistry and voltage standpoint, there is no reason an 18650 battery won't work in your 21700-size flashlight. However, the 18650 batteries are simply too short and narrow to make a solid connection. If you want to still use your 18650 batteries, look for 21700 battery flashlights that include an 18650 battery magazine like the NEW P12. This special adapter will make up for the extra length and diameter and allow you to use either size battery in your flashlight interchangeably. Both battery types typically operate at a nominal voltage of around 3.7V, making them electrically compatible. However, ensure that your device can handle any potential variations in voltage output.

In some cases, substituting a 21700 for an 18650 may be feasible if: The device has adjustable battery compartments capable of accommodating larger cells. The application does not require strict adherence to size specifications. You are using custom-built devices where you can modify the battery compartment. They technically all can since a 21700 has the same lithium technology and voltage as an 18650. The only issue is physical compatibility.

How Long Do 21700 Batteries Last?

The lifespan of a 21700 battery is influenced by several factors, including its chemistry, usage, maintenance, and charging habits. On average, a 21700 battery can last between 500 to 1000 charge cycles before it starts to lose capacity, though some models can endure anywhere from 1500 to 4000 recharge cycles. Compared to smaller batteries like the 18650, 21700 batteries are better at handling daily wear and tear. Using a lower amp charger can help reduce stress on the battery, thereby extending its lifespan. Proper storage is also crucial—keeping the battery in a cool, dry place and avoiding exposure to high heat or freezing conditions can prevent performance degradation. With proper care, a 21700 battery can last between 3 to 6 years, typically with 300 to 500 charge/discharge cycles, offering longevity and reliable performance over time.