21700 vs 18650 Battery: What’s The Difference?

21700 and 18650 are two popular types of  rechargeable batteries. Both are lithium-ion batteries and tend to be used in the same class of applications.

From the overview, you can easily assume that these to are the same, and maybe interchangeable.

But is this true?

21700 and 18650 are somehow different. And the purpose of this article is to expose all these differences between them.

Other than that, I will go ahead to give you valuable tips for buying 21700 and 18650 batteries in China.

21700 battery overview

A 21700 is a high-capacity battery designed for performance. It is a lithium-ion battery that is mainly designed for the high-drain applications.

In terms of the design, it is a cylindrical-shaped battery and slightly different from other common batteries in this category. The name refers to the dimension of the battery whereby it measures 21mm by 70mm.

Since it is a performance-oriented battery, it is mainly suitable for the high-drain applications such as electric cars, electric bikes and other high-capacity portable devices. In the recent years, it has expanded its scope to other applications such as flashlights.

The large size of this battery ensure it can comfortably run for long without completely draining its current. In other words, it is a perfect fit for the applications  that need longer runtime.

Of course, the large size also means that it has a high energy-density.

18650 battery overview

This is another lithium-ion battery that should attract our attention. Similarly, the name refers to the dimension of the battery whereby it measures 18mm by 650mm.

Just like other batteries in this category, it has an anode, cathode, a separator and an electrolyte.

18650  is also packed with a plethora of features that make it suitable for the high-drain applications. For example, it has a high energy density hence capable for storing a significant amount of energy in a small package.

The battery is also capable of handling high discharge cycles, a feature that improves its effectiveness and reliability when used as a source of power.

18650 batteries are widely available from different suppliers and you can easily find one that meets the needs of your application.

21700 battery specifications

Let’s look at the key specifications that define the 21700 battery.

• Cell: Lithium ion battery cell
• Nominal voltage  of 3.65V
• Charge voltage of 4.2V
• Discharge cut off voltage of 2.75V
• Nominal capacity of 4000mAh
• Standard current 2000mA and voltage of 4.20V
• Cycle  life: Less than 80% capacity after 1000 cycles
• Operating temperature of between -20 to +60ºC
• Dimensions D×H 21mm×70mm
• Weight 69-70g
• Charging methods CC and CV

18650  battery specifications

Now let’s look at the specifications for the 18650 battery

• Cell: Lithium ion battery cell
• Nominal voltage  of 3.6V
• Charge voltage of 4.2V
• Charging current 0.5C
• Discharge cut off voltage of 2.75V
• Nominal capacity of 2850mAh
• Standard current 2000mA and voltage of 4.20V
• Cycle  life: Less than 80% capacity after 500-700 cycles
• Operating temperature of between -20 to +60ºC
• Dimensions D×H 18mm×65mm
• Charging time
• Weight 48g
• Charging methods CC and CV

21700 vs 18650 Battery: What’s The Difference?

Now that you know the specs, lets’ go ahead and compare key areas that differentiate the two rechargeable batteries.

Nominal voltage

From the specs, it is clear that both have nominal voltage of 3.6V. This means that you should expect the same performance when it comes to the power requirement of the batteries.

Capacity

The current capacity of 21700 ranges between 3000 to 5000mAh. This means that it has a way higher capacity than the 18650 whose capacity is between 2000 and 3000mAh. This directly implies that the 21700 has a longer runtime than the 18650.

Physical attributes

In terms of size, 21700 is larger  and heavier than the 18650 battery. So, if size and weight are a big issue, you know which battery to go for. However the larger size and weight come with the advantage of higher capacity.

The size or dimensions will also depend on the application area of the battery.

Safety

While both the rechargeable batteries are considered safe, 21700 has an extra edge. It has an integrated circuit designed to prevent overcharging and discharging. 18650 does not have this feature. Hence 21700 is considered safer than the 18650 battery.

Cost

The price of 21700 is higher than that of 18650 battery. This is expected as it is packed with numerous features that make it an ideal option.

However, the price difference is too small, and you can easily get affordable rechargeable lithium cell batteries if you decide to buy in bulk.

Discharge rate

The discharge rate of a battery is the amount  of energy that can be drawn from it at any given time. 21700 has a higher discharge rate than the 18650 battery.

Application

Both the batteries are used in the same applications, that is for the high-drain applications such as EVs e-bikes and flashlights. However, we cannot dispute the fact that 21700 is still superior than the 18650 when it comes to most application areas.

Operating temperature

The batteries have the same operating temperature range. As long as they are stored with -20 to +60ºC, they will be able to deliver the desired performance.

Other than the temperature, you should store these batteries in proper physical conditions.

Which battery should n I choose? 21700 vs 18650

After this detailed comparison, which type of lithium battery cell are you going to buy?

First, you need to analyze your needs and wants.

What do you need to need to use the battery for and where do you intend to use?

From there, you can check out the features and specifications of each battery as we have outlined here.

Other than the technical specs, you can also find out the cost and availability of the battery.

Finally, you can check out from different lithium rechargeable battery cells suppliers  and place your order.

If you want to find more Electronic Components Distributors, please check out the following articles:

Electronic Components Distributors In the USA

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Electronic Components Distributors In Singapore

Electronic Components Distributors In Malaysia

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