The ultimate comparison guide of 21700 battery vs 18650



There's a huge difference between an average portable battery and the lithium-ion cylindrical battery. It is portable, reusable, and rechargeable, so you never have to worry about running out of energy. Lithium-ion cylindrical batteries are the smallest rechargeable batteries on the market today. So, you can enjoy more mobility without worrying about charging for an extended period of hours. You can also get your favorite device back to normal working condition to keep you going all day long.

The most widely used lithium-ion cylindrical batteries are 21700, 18650, AA, and AAA. In addition, there is Tesla's recently launched 4680 large cylindrical battery. Among them, 21700 is often compared with 18650. The same is the cylindrical battery launched by Tesla, what are the differences between the two? This article is a detailed comparison guide on 21700 battery vs 18650, which will give you a comprehensive analysis of the differences between 21700 and 18650, aiming to help you understand the comparison of 21700 battery vs 18650 in more depth.

1.What kind of battery is 21700?

What kind of battery is 21700


The 21700 battery is also known as a rechargeable lithium-ion cylindrical cell. 21700 usually refers to a cylindrical battery with an outer diameter of 21mm and a height of 70.0mm. When 21700 battery vs 18650, the former that appeared later is a more advanced battery technology. Because of the sturdy construction and lightweight weight, this battery can last longer than most other batteries.

2.What are 21700 batteries used for?

21700 is the most common type of battery used in flashlights and a range of household portable electronic devices. They have also been introduced in some high-lumen flashlight models. 21700 batteries can also be used to run laptops and even some EVs, they can also be used as vape batteries for vaping (smoking) accessories. If you have experience with electronics, you can probably replace packs by hand. But make sure to get the right size if possible and know how to use them properly, otherwise they might explode with incorrect handling.

3.Does Tesla use 18650 batteries? How many are 21700 batteries in a Tesla model 3?

Does Tesla use 18650 batteries How many 21700 batteries are in a Tesla Model 3


Tesla used the18650 lithium cobalt acid battery made by Panasonic for its model S and Model X cars back in 2013. This battery consists of thousands of independent cells, and each cell is slightly bigger than a regular lithium ion AA battery. Tesla currently holds 4,416 (21700) cells in the Model 3/Y Long-Range battery pack. The battery pack is made of 4 modules into bricks of 46 cells each block.

4.What is the highest capacity 21700 battery?

The 21700 batteries have between 3000 milliamps and 5100 milliamps, measuring how many hours' worth of power the cell can generate. The battery voltage in the 21700s ranges from a low of 2.5 volts to a high of 4.2 volts. The 21700 cells have a 3.7V and 4.2V for charging voltage which is the standard for a 21700 battery. It is clear that a 3.7v, 5100mAh 21700 battery stores 3Ah or 5Ah depending on the model. Usually, the max capacity is 15 to 20 watt-hours. For example, a typical air conditioner uses 9000 BTU, about 1100 Wh (watt per hour). So, it would help if you had up to 74 (21700) batteries to run an AC for 1 hour.

5.How long does an 18650 battery take to charge?

Typically, the amount of time to fully charge a 18650 lithium-ion battery takes 4 - 5 hours. The capacity of an ordinary 18650 lithium battery is about 2500 mAh, while the output voltage of an ordinary 18650 lithium battery charger is 4.2 volts, and the output current is about 500 mAh. In theory, it takes 5 hours to fully charge the battery. Of course this is not absolute. For high-rate lithium batteries, the allowable charging current can also reach more than 1 amp, so the charging time will be reduced accordingly.

How long does an 18650 battery take to charge

6.Can you charge 21700 batteries in a 18650 charger?

Based on the battery charging device, it would fit, and size-wise would work as well as the recesses. It has spring-loaded battery holders to accommodate the versatile size of batteries. The 21700 battery cells are 3 millimeters wider and 5 millimeters longer than a 18650 battery. To be safe, use chargers that explicitly say they are compatible with 21700 batteries.

7.Does 21700 last longer than 18650?

The battery cells used in 18650 and 21700 are often discussed, as they offer fairly similar performance. The only notable difference is that the size of the battery cells can vary. Other distinctions between the batteries are their capacity.

18650 Li-ion battery cells

21700 Li-ion battery cells

1 single cell: 2.0Ah–3.0Ah (36 Wh–54 Wh)

1 single cell: 3.0Ah–4.0Ah (54 Wh–72Wh)

 2 battery packs: 4.0Ah–6.0Ah (72 Wh to 108 Wh)

2 battery packs: 6.0Ah–8.0Ah (108 Wh–144 Wh)

3 battery packs: 9.0Ah (162Wh)

3 battery packs: 9Ah–12Ah (162 Wh–216 Wh)

The 18650 can provide between 2300-3600mAh while the 21700 has a capacity from 3000 to 5100mAh. It shows the 21700 can be more long-lasting in general than the 18650.

8.Is a 21700 battery better than 18650? Can I use a 21700 battery instead of 18650?

The higher power of 21700 cells and lower internal resistance means that 18650 cells have a lower polarization. It is a greater divergence between their voltage curves at higher C-rates. The 21700 batteries are a larger and more powerful replacement for 18650 in EV battery packs. The 21700 has twice the capacity at discharge rates up to 3.75C, which is 50% more than the 18650.

Is a 21700 battery better than 18650 Can I use A 21700 battery instead of 18650

9.What is the difference between 18650 and 21700 batteries?

The 21700 batteries weigh between 60 to 65 grams, and their energy density is 300 watt-hours. On the other hand, 18650 batteries weigh between 45 to 48 grams per each, and their energy density is less than 21700 batteries. It shows the 21700 battery is more durable and last longer than a conventional 18650 battery. Some of the important characteristics that determine which cell is better than the other such as follow:


Diameter (Mm)

Height (Mm)

Capacity (mAh)


The energy density (Wh/Kg)













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