21700 vs 18650 Battery
Currently, lithium-ion batteries are widely used in various electronic devices due to their high energy density and recyclable properties. Lithium-ion batteries can be subdivided into multiple categories, the most common of which include 18650 batteries and 21700 batteries. Let’s take a look at these two batteries.
About 18650 battery
What is 18650 battery?
18650 battery is the abbreviation of rechargeable lithium-ion battery. Its size is 18mm in diameter and 65mm in length. 18650 batteries have excellent capacity and discharge rate and can be used in flashlights, electronic watches, laptops, new energy vehicles , and some high-power consumption equipment.
Advantages of 18650 battery
(1):Good heat dissipation performance:From the internal structure of the battery, the winding length and thickness of the 18650 battery are smaller than that of the 21700 battery, which means that it has better heat dissipation performance when working.
(2):Affordable and easy to obtain:Currently, there are many manufacturers of 18650 batteries on the market, and its market development is almost mature. This means that the supply of 18650 batteries is sufficient, it is easy to obtain, and we can buy it at a relatively affordable price.
(3):The battery is more compact and lighter.
Application fields of 18650 battery
Electronic cars, electric bicycles
Mobile power supply, emergency power light
Consumer electronics, etc.
About 21700 battery
What is a 21700 battery?
The 21700 battery is a type of rechargeable lithium-ion battery. Its number represents the physical size of the battery, that is, the battery diameter is 21mm and the length is 70mm. 21700 batteries are quite popular in Tesla and some electric scooters and electric cars. It can also be used in consumer electronics such as e-cigarettes and flashlights.
Advantages of 21700 battery
（1）Larger battery cell capacity:Taking the battery used by Tesla as an example, since it replaced 18650 cells with 21700 cells, the battery cell capacity can reach 3 to 4.8Ah, an increase of nearly 35%. In other words, the total capacity of the 21700 battery will be greater.
（2）The energy density of the battery system is higher:According to the data given by Tesla, the energy density of the 18650 battery system used in its early days was about 250Wh/Kg. But then the energy density of the 21700 battery system it produced and used could reach 300Wh/Kg, which was nearly 20% higher than the energy density of the original 18650 battery.
（3）Lower manufacturing cost:21700 battery capacity is larger than 18650 battery capacity. This means that the 18650 battery requires more raw materials to achieve the same capacity as the 21700 battery. For example, a 100Ah battery can be composed of 30 3300mAh 18650 cells, but if replaced by 5000mAh 21700 cells, only 20 cells are needed.
（4）Stable battery performance:The 21700 battery maintains the high reliability and stability of the 18650 battery, and its battery performance in other aspects has also been improved.
Application fields of 21700 battery
Electronic cigarette(21700 vape battery)
Other consumer electronic products, etc.
21700 battery VS 18650 battery
18650 battery and 21700 battery are both steel-cased cylindrical lithium-ion batteries. As long as we pay a little attention, we will find that they can be seen everywhere in our daily life and work.
Similarities between 21700 battery and 18650 battery
- The application fields are similar. Both 18650 batteries and 21700 batteries can be used in power tools, electric vehicles, flashlights, laptops, etc.
- They are all steel-cased cylindrical batteries.
- All have low self-discharge rate. That is, the battery can be stored for a longer period of time without losing its charge quickly.
- It can be recharged repeatedly, and the number of recharges may exceed 500 times.
- The battery operating temperature is similar, and its optimal temperature is around 25°C (77°F).
- All have good battery system energy density.
The difference between 21700 battery and 18650 battery
（1）Size difference:The most obvious difference between 21700 batteries and 18650 batteries is their different physical sizes. The 21700 battery is larger in size than the 18650 battery.
（2）Capacity difference:The difference in battery size brings about differences in its capacity. The larger battery size also has a larger capacity. The maximum capacity of the 18650 battery is about 3500mAh, while the maximum capacity of the 21700 battery is about 5000mAh. In comparison, the large capacity of the 21700 battery can support the use of the device for a longer period of time.
-Capacity range of 18650 battery: 2200mAh to 3600mAh
- Capacity range of 21700 battery: 3300mAh to 5100mAh
（3）Weight difference:Due to different capacities, 21700 batteries are 40% to 90% heavier than 18650 batteries. But this is not always the case, as the materials used to make the battery can lead to large differences in the weight of the battery.
（4）Cost price difference:Protection mode batteries (or simply "protected" batteries) can prevent fire or explosion to a certain extent. In most cases, unprotected 21700 cells have a similar cost per mAh to 18650 cells. However, if it is a protected 21700 battery, its cost price will be more expensive than that of an 18650 battery.
（5）Power difference:Compared with 18650 batteries, the 21700 battery with a larger capacity has more space to increase the cooling capacity and available power of the battery pack. The 21700 battery has more sufficient power and power to support the operation of the device.
Choose 18650 battery or 21700 battery? Which one is better?
Between the 18650 battery and the 21700 battery, it is most important that the battery you choose matches your needs. Different batteries have different characteristics and uses, and you need to choose based on actual conditions.
For example, with the same power consumption, if you want a battery with a longer service life, choose the 21700 battery. The 21700 battery has a larger capacity and is more durable. But if you want the overall weight of the device to be lighter, then the 18650 battery may be a good choice.
Some suggestions when purchasing 18650 batteries or 21700 batteries
（1）Be wary of false advertising.If you see an 18650 battery or 21700 battery with a capacity that is higher than their maximum capacity, be wary as they are most likely fake.
（2）Pay attention to compare the prices of protected and unprotected batteries. Generally speaking, protected batteries cost more than unprotected batteries. If you find a protected battery that's really cheap, it's best to make sure it's genuine before you buy it.
（3）Pay attention to comparing the weight of the battery.If you find that the weight of the 21700 battery is less than 60g, or the weight of the 18650 battery is less than 42g, it indicates that the quality of the battery may not be good, or it may even be a counterfeit.
（4）Purchase batteries from reputable manufacturers or merchants.
Finally, if you want to learn more about batteries, you can visit BatteryMall.com/support or go to batterymall.com to purchase new batteries.
Finally, if you want to learn more about batteries, please visit：BatteryMall.com/support.
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