Apr. 21, 2025
In addition to the widely used 21700 battery, there are other cylindrical lithium-ion batteries with similar specifications, such as the 20700. Both the 20700 and 21700 batteries share the same nominal voltage and are typically compatible with the same chargers. However, there are slight differences between the two. The 21700 is slightly larger in both diameter and overall volume, which allows it to store more active materials—resulting in a higher capacity compared to the 20700.
A 21700 battery is a rechargeable lithium-ion cell that measures 21 mm in diameter and 70 mm in length—hence the name "21700." This size gained popularity through its use in electric vehicles, particularly Tesla models, as well as electric scooters.
Today, 21700 batteries are also commonly found in high-drain devices such as vaping equipment, flashlights, and increasingly in power tools, thanks to their high energy density and extended runtime.
The primary advantage of a 21700 battery over an 18650 lies in its significantly higher energy capacity. Due to size limitations, 18650 batteries typically max out at around 3600mAh. In contrast, the slightly larger dimensions of the 21700 battery allow it to reach capacities up to 5000mAh—a 42% increase.
For users of high-drain devices like flashlights, this means substantially longer runtimes on a single charge—an essential benefit for professionals and heavy users. Despite the larger size, the 21700 battery still maintains a diameter under 1 inch, allowing flashlights powered by these cells to remain compatible with standard 1-inch weapon mounts and holsters.
A 20700 battery is a rechargeable lithium-ion cell with a diameter of 20 mm and a length of 70 mm.
The 20700 battery shares similarities with the 21700, particularly in size, and is commonly used in a variety of electronic devices and vehicles, such as skateboards, electric scooters, and hoverboards.
Additionally, it is frequently found in vaping devices and flashlights due to its reliable performance and energy capacity.
Both the 20700 and 21700 batteries use the same raw materials and belong to the ternary lithium category, which means they share the same nominal voltage of 3.6/3.7V. As a result, they can be charged with the same charger. However, due to the larger size of the 21700 battery, it will take slightly longer to charge compared to the 20700.
Typically, a 20700 battery has a capacity of 4250mAh, while the 21700 battery ranges from 4800mAh to 5000mAh. This means the 21700 battery generally offers longer runtime.
Both 20700 and 21700 batteries have a discharge rate of 3C, meaning their performance in terms of discharge rate is very similar, with little to no significant difference between the two.
as I have shown, the size/diameter of 20700 is 20mm and the length is 70mm. while the size of 21700 is slightly bigger at 21mm and its length is the same as 70mm. So they are same nearly.
The 21700 battery weighs 72g, while the 20700 weighs 63g. The 21700 is clearly heavier, primarily due to its larger size and the additional raw materials used in its construction.
Generally, one would expect the larger 21700 battery with its higher capacity to be more expensive. However, the opposite is true—the 20700 battery tends to be more expensive than the 21700.
This price difference is largely due to supply and demand. Tesla’s use of 21700 batteries has led to widespread production, making them more affordable. In contrast, 20700 batteries are less commonly used, and their lower production volume has made them rarer and more expensive in the market.
The performance of the 20700 and 21700 batteries is quite similar, with only minor differences. If we were to compare, the 21700 battery generally offers a longer runtime than the 20700. Both batteries, however, boast about 20% higher energy density compared to other contemporary battery types.
While the 21700 battery is more mature and widely used, both the 20700 and 21700 are versatile and can be used in a variety of devices. In fact, they are often interchangeable.
Common Applications of the 21700 Battery:
- Flashlights
- Electric bicycles
- E-cigarettes
- Power tools
- Electric wheelchairs
- Golf cart batteries
- Electric cars
Common Applications of the 20700 Battery:
- Scooters
- Skateboards
- Cordless power tools
- E-cigarettes
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