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Comparing 18650 and 21700 Batteries

(Summary description)

Comparing 18650 and 21700 Batteries

(Summary description)

  • Categories:Industry information
  • Author:Pamela
  • Origin:Battery university
  • Time of issue:2020-03-23 10:46
  • Views:16


What is An 18,650 Battery?


It’s a lithium-ion battery cell classified by its size: 18,650. The “18” represents the cell’s 18mm diameter. The “65” stands for its 65mm length, and the “0” denotes the cell’s cylindrical form.


What is a 21,700 Battery?


This is a rechargeable lithium-ion cylindrical cell.

The same naming strategy applies here:

  • 21 represents the 21mm diameter
  • 70 represents the 70mm length
  • 0 represents the cylindrical cell form

What’s the Difference between 18,650 and 21,700 Batteries?

From the measurements above, you can easily tell the new-generation lithium-ion battery cell type 21,700 has a larger volume than the older 18,650 battery cell.

How big of a volume?

Find out the quick volume and energy capacity calculations below. It’s nothing technical, we promise.


How Are the Two Battery Cells Different?


1.  Energy Density


How long do 18,650 batteries hold charge for?

This short calculation below shows that a 21,700 battery offers up to 46% more energy capacity than its 18,650 counterpart.



The 21,700 battery cell achieves that by offering an extra 5mm X 3mm volume and 7,701 cubic millimeters more.



Both the 18,650 and 21,700 batteries are based on the traditional Lithium-ion battery cell. According to research, Li-Ion battery cells have a slightly better energy density compared to Li-Po battery cells. So, if you have many devices to charge, choose a power bank with a 21,700 lithium-ion battery cell.

Elon Musk and his team decided to use a variation of the 21,700 Li-Ion battery cells, the Tesla 2170 battery cells, to power the Tesla Model 3 up to 399-499 miles.

That’s a big improvement than what the older two models could achieve on a single charge with their 18,650 Li-Ion battery cells.  


2. Safety and Stability


This is one of two areas where polymer battery cells outdo Li-Ion cells. High-capacity Li-Ion batteries were in the news a while ago for exploding and were banned from flights in different places.

However, advanced battery technologies by reputable manufacturers have eliminated the issue of Li-Ion batteries exploding if they overcharge or overheat.

For example, despite its incredibly high output, the RAVPower PD Pioneer 20,000mAh 60W portable charger  comes with an entire safety system 

The system is geared towards protecting you, your loved ones, and dear devices from burns, overheating, overcharging, and short-circuiting.

The 21,700 battery technology makes for slower discharging and higher thermal stability than the 18,650 battery technology, according to a 2018 research study




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