ADDTECH | 18650 Vs. 21700 Battery Side-by-Side Comparison

By Addmotor | 28 February 2024 | 0 Comments
Lithium-ion batteries have been the popular choice of batteries in the market in recent years. They are being used in a variety of electrical devices, especially in electrical vehicles, due to their various benefits. The rechargeable properties, high energy density, portability, and longevity are some of the advantages of lithium-ion batteries that make them a popular choice for various electrical devices.

There are various types of lithium-ion batteries available, but the most popular ones are 18950 and 21700 lithium-ion batteries. The two lithium-ion batteries may seem similar, but they vary in size, which may seem like a minor difference, but it impacts how the battery works.  So, let’s compare the two popularly known lithium-ion batteries i.e. 21700 battery vs 18650 battery in detail based on their advantages and disadvantages, parameters, and applications to help you make an informed decision when purchasing an electrical device, especially electric bikes, and electric trikes.


Comparison between the key parameters

♦ Size and dimensions

As we said above, the major difference between the 18650 and 21700 battery cells is their size and dimensions, which then impact the other parameters of the batteries. The 18650 battery cells are 18 mm wide and 65 mm tall, whereas the 21700 battery cells are 21mm wide and 70 mm tall. The larger size of the 21700 battery allows it to store more energy, providing a greater capacity.

♦ Capacity

There is a difference between the size of 18650 and 21700 battery cells, which majorly impacts the capacity of the battery. The larger the size of the battery the larger the capacity. With its limited dimensions of 18mm X 65mm, the 18650 battery cell has a maximum capacity of up to 3500 mah. Whereas the 21700 battery cells, due to their larger size, hold a maximum capacity of 5000 mah.

♦ Energy density

A battery with a higher energy density is beneficial for electric vehicles as it allows longer battery life and efficient performance. When comparing the 18650 and 21700 battery cells, the 21700 battery cells have higher energy density due to their larger size, which allows more energy storage in the same volume as the 18650 battery cell. 

♦ Discharge rate

Discharge rate is another important parameter to look for when inspecting a battery in an appliance or an electrical device, as it measures the amount of current that can be delivered safely without causing damage. Lithium-ion batteries usually have a greater output current as compared to other batteries, such as lead-acid batteries. Both the 18650 and 21700 lithium-ion batteries have higher discharge rates, but when compared, the 21700 battery has a greater capability to handle higher output currents, as compared to the 18650 battery.

21700 lithium-ion battery


• High Capacity

The 21700 battery has a higher capacity of a maximum of 3600 Mah, which makes it a suitable choice for electric vehicles, i.e., electric trikes and electric bikes so that they can cover more miles on a single charge.

High energy density

21700 lithium-ion battery has a 20% higher energy density than the 18650 battery. The higher energy density of the 21700 battery allows it to store more energy in the same size and volume. The higher density also makes the devices deliver better performance and run for a longer time on a single charge.

Higher discharge rate

The higher discharge rate of the 21700 battery is also one of its advantages, as it can handle the higher discharge rates compared to the other batteries, which makes it suitable for electric vehicles such as electric bikes and electric trikes.



Compared to the other lithium-ion batteries, such as the 18650 battery, the 21700 battery is quite expensive to manufacture, and due to its less production. It also increases the cost of the device or any electrical vehicle that uses a 21700 battery.


Due to its larger size, the 21700 lithium-ion battery weighs much more than the other batteries available in the market. The increased weight of the battery also increases the weight of the devices using this battery, which can be problematic, especially in electric vehicles, i.e., electric bikes and electric trikes, which are already heavier and bulkier.

Limited compatibility

As the 21700 battery is newer in the market, it is not very compatible with various devices. The size of the 21700 battery also makes it incompatible for various devices as due to its larger size it is unable to fit in smaller and compact devices.  It limits the application of 21700 batteries to larger devices such as electric vehicles.

18650 lithium-ion battery


Wide compatibility

The 18650 battery has been widely used in the market for a long time and is compatible with a wide range of devices, from flashlights to electric vehicles such as electric bikes and electric trikes. Due to its smaller size, the 18650 lithium-ion battery can fit into a wide range of devices, that may be small and compact, or large and bulkier.

Widespread availability

Since the 18650 lithium-ion battery has been quite popular and widely used in various appliances, it is easily available in the market. Due to its widespread availability, the 18650 battery can be found at cheaper rates, providing a cost-effective battery option for customers looking for an affordable and high-performance battery.


Limited energy density

Compared to the latest lithium-ion battery, i.e., the 21700 battery, the 18650 battery has limited energy density, which reduces its ability to store maximum energy. The limited energy density allows lesser storage of energy and ultimately results in shorter run times for devices, which can be problematic for electric vehicles, i.e., electric bikes and trikes.

Limited capacity

Another downside of the 18650 battery is its limited capacity, as compared to the 21700 lithium-ion battery. Its maximum capacity is 3500 Mah, which is less than the capacity of a 21700 battery. The lesser capacity of the battery means it won’t be able to deliver much power to the high demand devices such as electric bikes and electric bikes, and they may run out of battery by covering just a few miles.


Applications of 21700 battery

21700 lithium-ion battery is commonly used in high-demand or high-performance applications due to its high capacity, high energy density, and efficient performance. Let's look at some of the devices using 21700 batteries.

♦  Electric vehicles

The 21700 lithium-ion battery is being widely used in electric vehicles, especially electric bikes, and trikes, as it provides an extended driving range due to high capacity and high energy density, ultimately allowing an improved performance.

♦  High-performance devices

The 21700 lithium-ion battery is suitable for high-performance devices such as high-powered flashlights, drones, and power tools such as drills and saws, as they require high power output and longer run time.

♦  Energy Storage systems

Energy storage systems such as solar power require a battery that can store the maximum energy generated by solar power quickly and efficiently. Due to higher energy density and capacity, the 21700 battery is widely used in large-scale renewable energy storage systems such as solar power as it allows better storage and utilization of energy.

♦  Medical devices

Medical devices such as defibrillators and monitors require batteries that have a longer run time and don’t go empty easily. Due to this, the 21700 battery is being widely used in medical devices due to its higher capacity, which allows the devices to remain charged and be used anytime in crucial conditions.

Applications of 18650 battery

18650 lithium-ion battery is used in a wide range of devices due to its compact size, lightweight, and high energy density. The 18650 battery is found in devices including:

♦  Electric Bike

As 18650 Li-ion batteries can store more power in a compact size, it is crucial for electric bikes to extend the range and riding time. Therefore, 18650 batteries are widely used in electric bikes and electric tricycles.

♦  Portable devices

Due to its smaller size and weight, and higher energy density, the 18650 lithium-ion battery can fit into compact spaces, which makes it suitable for portable devices such as phones, remote-control toys, cameras, etc. 

♦  Laptops

18650 battery is commonly used in laptops and tablets due to its compact size and efficient performance. It may not provide a longer run time than a 21700 battery, but enough to allow the laptops to run for hours without recharging.

♦  Vapes

This lithium-ion battery is also commonly used in vaping devices due to its discharge rate, which is high enough to provide the power output needed by vaping devices. Its compact and lightweight nature also makes the 18650 battery a suitable choice for vapes.

♦  Flashlights

 Another device in which an 18650 battery is commonly used is the flashlight, which requires a decent amount of consistent power and run time. Due to its small size and lighter weight, this lithium-ion battery is considered a suitable choice for flashlights.

♦  Electric vehicles

The 18650 battery is also used in electric vehicles, which may not be as popular as the 21700 battery but has been widely used in electric bikes and electric trikes. The high discharge rate, high energy density, low self-discharge, and long life cycle make it a popular choice among electric vehicles.


There's tough competition between the 18650 battery, and the 21700 battery when compared side by side, as both lithium-ion batteries have their own set of advantages and disadvantages. The choice of the battery depends upon the device, its requirements, and your preferences. Before deciding which lithium-ion battery can be the best choice, it is better to look at the parameters of the battery, i.e., capacity, size, energy density, power output, etc., and the device requirements.  

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