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18650 vs 21700 vs 20700 Vape Batteries

Without power, your vape device is just a fancy storage unit for e-liquid. Your vape needs the right type of batteries in order to achieve top performance and a great vaping experience.

High-quality batteries will provide more power and should have a long lifespan. Using the wrong batteries can impact battery life and longevity.

Thankfully, we stock a wide range of batteries that are capable of powering your vape. This article will explore the differences between 18650, 20700, and 21700 batteries. By exploring the pros and cons of each option, you’ll be able to pick the best options for your needs.

Keep reading to learn which batteries will best suit your device and vaping needs.

What Do the Different Battery Numbers Indicate?

Lithium-ion batteries, also sometimes written as Li-ion batteries, are used for vapes because of their excellent lifespan. They can even last as much as ten times longer than lead-acid batteries.

Lithium-ion batteries are identified by numbers that may appear confusing at first. When you understand the number sequence, it makes it significantly easier to determine the batteries you will need.

The numbers show the battery size. The diameter is shown by the first two numbers. The following two numbers let you know the battery length.

The batteries we are looking at today are broken down as follows:

  • 18650 – 18 mm diameter, 65 mm length
  • 20700 – 20 mm diameter, 70 mm length
  • 21700 – 21 mm diameter, 70 mm length

How Do 18650, 20700, and 21700 Batteries Compare?

For many years, the 18650 battery was the most popular battery type. These rechargeable lithium-ion cells are used in all manner of items. These include:

  • Electric Cars
  • Torches
  • Computers
  • Vape Mods
  • Power Tools
  • Battery-Powered Construction Equipment
  • Remote Control Toys

20700 and 21700 batteries haven’t been around as long as the 18560s. Because they are newer, they are used in fewer applications.

20700 were the next to come along after 18650. These offer greater energy density.

Then the 21700 cells came along. Panasonic and Tesla collaborated to create this new cell for use in electric vehicles.

21700 are now produced by a wide variety of manufacturers. This gives the consumer far greater choice.

When comparing the newer 20700 and 21700 against the classic 18650 lithium batteries, the former both enjoy higher energy density per kilogram than 18650 batteries.

21700 batteries’ energy density is around a third greater than that of the 20700.

The greater energy output means that they have slower heat dissipation. However, additional vent holes in 21700 combat this. When used in vapes, any difference in heat is barely noticeable.

There are pros and cons to each option. If you want a smaller, lighter vape mod, you may have to sacrifice some power from your batteries.

18650 Batteries

The 18650 lithium-ion battery is the original option for rechargeable devices. Comparing 20700 and 21700 vs 18650 battery cells reveals pros and cons for each.

18560 vape batteries offer a balance of Amp output and capacity. They are suited to both sub-ohm and MTL vape kits. Relatively quick to charge, 18650 batteries last for a long time.

To take a closer look at the specifications of 18650 batteries, let’s consider the example of the Molicel P28A 18650 Battery Pair which we sell here at Legion of Vapers:

  • 18 mm x 65 mm dimensions
  • Unprotected
  • Flat-Top
  • 4.2V (fully charged)
  • 3.6V to 3.7V nominal voltage
  • 25A maximum continuous discharge
  • 2800mAh capacity

So, what are the pros and cons of this type of battery?

18650 Batteries Pros

  • Compatible with an extensive range of vape mods
  • Affordable battery types
  • Great battery life
  • Available from a wide range of stockists
  • Used as standard in the vaping industry

18650 Batteries Cons

  • 18650 batteries can be dangerous if damaged or unwrapped
  • Should not be used in mechanical mods
  • Lower energy density than 20700 and 21700
  • Lower power output than 20700 and 21700

Why Are 18650 Batteries So Popular?

18650 batteries are popular because they are small and still offer a high capacity. This type of battery has been around since the early 1990s. To maintain popularity for this long is an incredible achievement – especially when you consider the level of technological development at this time.

Small batteries allow for smaller, lightweight vaping devices. This is a significant benefit for people that want a vape that is easily transportable.

20700 Batteries

20700 are large batteries that are best used in sub-ohm vape devices. Vapers who are looking for an extended battery life can benefit from this option. The enhanced power output and capacity also ensure you will be able to produce large clouds of vapour.

20700 Batteries Pros

  • Greater power density provides long-lasting performance and great battery capacity
  • 20700 batteries are typically an affordable option
  • They are still fairly lightweight options that provide great performance for electronic equipment

20700 Batteries Cons

  • The large size of 20700 means that electronic devices need to be specially designed to cater for them
  • The 20700 can have a shorter battery life if lithium-ions are over-discharged

21700 Batteries

The 21700 battery is the largest battery option for vapes. While this does increase the size and weight of the device, there are some key benefits. This large lithium-ion battery has more capacity and power. This makes it suitable for sub-ohm devices and an ideal choice for cloud chasers.

21700 Batteries Pros

  • Large battery capacity
  • Long battery life
  • It can be used in mechanical vapes
  • It can be used in high-wattage vapes
  • Offers vapers more control

21700 Batteries Cons

  • Heavier than 18650 options
  • Size and weight restrict portability
  • It doesn’t fit in all vape devices
  • A more expensive option

Important Considerations For Buying a Vape Battery

18650 vs 21700 vs 20700 lithium batteries have their various pros and cons, but not all battery types are compatible with all devices. The vape device and battery pack size will dictate the most suitable option for you.

Your preferred vaping style also determines the type of device you need. Vaping styles require different power outputs delivered by your battery – an MTL vaper will never need a 20700 battery but a cloud-chasing hobbyist might need one.

It’s also important to consider battery charging. Investing in high-quality battery chargers will be beneficial when working with high-drain devices. It can also provide a longer lifecycle for your battery.

Vape Battery Safety Advice

Always remember the following safety advice in order to protect your battery pack, vape device, and yourself.

  • Batteries should never be carried loose
  • Batteries should never come into contact with other conductive materials
  • You should never mix different branded lithium batteries
  • The correct charging current must be used on your device
  • Never overcharge a lithium battery
  • Batteries should not be stored in extreme temperatures
  • Keep batteries out of direct sunlight
  • Never use damaged batteries

We offer an excellent range of stylish and useful battery repair kits that can help to prolong the life of your batteries.


It is always good to have a better understanding of your vape’s power source.

Comparing the different choices won’t necessarily give you a “better” battery. However, it can provide you with the most suitable option for your needs.

The battery type you need will be determined by your vaping style and the device you use. Not all batteries are created equal, but they do all have benefits that are worth exploring.

Take a look at our excellent range of batteries and vaping accessories to improve your vaping experience today.

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