The 21700 Battery Revolution: A Complete Guide for Enthusiasts

Apr 13, 2023 | XTAR

Welcome to the world of 21700 batteries – the latest and greatest in cylindrical li-ion technology. As an experienced battery expert, I’m excited to share with you everything you need to know about 21700 batteries, from their capacity and compatibility to their performance and safety features. Whether you’re a business customer looking for the best batteries for your products or a battery enthusiast eager to upgrade your flashlight or vaping device, this comprehensive guide has got you covered. So, let’s dive in and explore the 21700 battery revolution!

21700 Battery Basics

As a battery enthusiast, it’s important to understand the basics of 21700 batteries before diving into the details. In this section, we’ll cover everything you need to know about 21700 batteries, from their basic definition to their compatibility with devices.

what are 21700 batteries?

What are 21700 batteries?

21700 batteries are cylindrical lithium-ion batteries that are 21mm in diameter and 70mm in length. They are larger than the popular 18650 batteries and have gained popularity due to their high energy density, longer run time, and increased safety.

Capacity and dimensions

The capacity of a 21700 battery can vary depending on the brand and model, but they typically range from 3000mAh to 5000mAh. This high capacity, combined with the larger size, makes the 21700 battery an excellent choice for devices that require a lot of power. Currently, the highest capacity of 21700 battery is 5000mAh at the market.

Unprotected and protected types

Like other lithium-ion batteries, 21700 batteries come in both protected and unprotected versions. Unprotected batteries are simply the bare cells without any additional protection, while protected batteries have a built-in protection circuit that helps to prevent overcharging, over-discharging, and short circuits.

It’s important to note that unprotected batteries can be dangerous if not handled properly, so it’s recommended to use protected batteries in most devices. However, unprotected batteries can be useful in certain applications where maximum power output is needed.

Compatibility with devices

Many high-end devices, such as flashlights and vaping devices, are designed specifically for 21700 batteries. However, some devices may also be compatible with 18650 or other battery types. In addition, Not all 21700 batteries are created equal. Some devices may only work with certain brands or types. So be sure to check your device’s specifications before making a purchase.

With these basic concepts in mind, let’s dive deeper into the world of 21700 batteries and explore their benefits, top brands, and more.

Performance and Safety

As a battery expert, I’ve tested and used countless lithium-ion batteries over the years, and 21700 batteries continue to impress me with their outstanding performance. Let’s dive into the advantages and disadvantages of these batteries and discuss some important safety considerations.

Performance and safety of 21700 battery

Advantages and Disadvantages of 21700 Batteries

One of the key advantages of 21700 batteries is their larger capacity compared to other lithium-ion batteries. This means they can power devices for longer periods of time and require less frequent charging. They also have a higher discharge rate, making them suitable for high-drain devices like flashlights and electric vehicles.

However, with these advantages come some drawbacks. 21700 batteries are larger and heavier than other lithium-ion batteries, which may not be suitable for some devices. They are also more expensive, and not all battery chargers are compatible with them.

Safety Considerations

Safety should always be a top priority when working with lithium-ion batteries, and 21700 batteries are no exception. It’s important to use only high-quality, reputable brands and to avoid overcharging or exposing them to extreme temperatures.

Another safety consideration is the use of protected vs. unprotected 21700 batteries, as discussed earlier. If you’re not experienced in handling unprotected batteries, it’s best to stick with the protected type for added safety features.

Environmental Impact

As we strive towards more sustainable and eco-friendly practices, it’s important to consider the environmental impact of our battery use. While lithium-ion batteries are generally more eco-friendly than traditional disposable batteries, they still require proper disposal or recycling to prevent harmful chemicals from entering the environment. Many battery manufacturers now offer recycling programs for their products, so be sure to look into these options when it’s time to replace your 21700 batteries.

Top Brands and Comparison

As the popularity of 21700 batteries continues to grow, the market has become flooded with various brands and options. It can be overwhelming for customers to choose the right one, especially when considering factors like performance, safety, and durability. This section will help you.

Top brands and battery size comparison of 21700.

Overview of Top 21700 Battery Brands

When it comes to 21700 batteries, there are several top brands to consider. Some of the most popular brands in the market include Samsung, Sony, LG, Molicel, XTAR, and Efest.

Samsung is one of the top brands in the market and is well-known for its INR21700-30T battery, which is a high-performance battery that offers a 3000mAh capacity and 35A continuous discharge rate. Sony also offers high-quality 21700 batteries, with its VTC6A battery being a popular option that provides a 4000mAh capacity and 35A continuous discharge rate.

XTAR offers high-quality 21700 batteries with the highest capacity of 5000mAh. It is popular among enthusiasts and professionals in the industry.

When choosing a brand, it’s important to consider factors like capacity, discharge rate, and overall quality to ensure that you’re getting a battery that meets your needs.

Comparison with Other Battery Sizes

While 21700 batteries are becoming increasingly popular, there are still other battery sizes on the market that are worth considering. Some of the most popular battery sizes include the 18650 and 26650. Here is a table for you to make a quick and easy comparison.

Battery Size

Diameter (mm)

Length (mm)

Capacity Range (mAh)

Common Uses





Flashlights, Vaping Mods





Electric Vehicles, High-Drain Devices





Electric Bikes, Power Tools

This table shows that, 21700 batteries offer several advantages that make them worth considering. They have a larger capacity than 18650 batteries, with most models ranging from 4000mAh to 5000mAh, and are more compact than 26650 batteries, making them a great option for devices that require high power output in a small size.

When comparing different battery sizes, it’s important to consider factors like capacity, size, and compatibility with your device.

Chargers and Charging Methods

When it comes to charging 21700 batteries, it’s essential to use a compatible charger and follow the manufacturer’s guidelines to ensure safety and optimal performance. Here are some types of chargers for 21700 batteries:

Best 21700 battery chargers

Types of chargers for 21700 batteries

• USB chargers: These are the most convenient type of charger and can be charged via USB ports. They are usually small and portable, making them ideal for on-the-go charging.

• Wall chargers: These chargers can provide faster charging speed compared to USB chargers. Some chargers reach 4A per slot in charging current. However, they are less portable and may require an AC power source.

• Smart chargers: These chargers have advanced features like automatic detection of battery type and capacity, overcharge protection, and temperature control. They are ideal for professional use and can provide optimal charging speed. 

Nowadays, the best 21700 battery charger is USB 4-slot smart charger with LCD screen, such as XTAR VC4SL. This charger has capacity test and storage voltage adjusting function, which is very helpful for prolonging battery life.

Best charging methods

The best charging method for 21700 batteries is the TC-CC-CV charging method. Many smart chargers use this method, including the XTAR brand. This method ensures that the battery is charged safely and efficiently. During the charging process, the charger will automatically select the proper charging current according to the battery status. The fast charging only happens in the constant charging current period. Customers can also adjust the charging current by themselves, but they need to know what current they should use based on the battery capacity.

Charging Safety Tips

It’s important to follow these safety tips when charging your 21700 batteries:

Use a high-quality charger that is designed for 21700 batteries.

Avoid charging the batteries at a high temperature or in direct sunlight.

Do not overcharge or over-discharge the batteries.

Do not leave the battery in the charger after it is fully charged.

Do not charge damaged or wet batteries.

Industry Applications

21700 batteries are widely used in various industries due to their high energy density, long lifespan, and reliable performance. Here are some of the main industries that benefit from the use of 21700 batteries.

21700 battery applications in flashlight, electric car, power bank, etc.

Usage Industry

Electric vehicles (EVs): The most well-know application of the 21700 batteries is in electric cars like Tesla, and other vehicles like e-bikes, e-scooters, due to their high energy density and ability to provide a long driving range on a single charge.

Portable electronics: Many portable devices such as laptops, flashlights, and power banks are powered by 21700 batteries. These batteries provide a high capacity in a compact size, making them ideal for use in small electronics. It is also widely used in vape mods due to its high discharge rate.

Energy storage: 21700 batteries are used for energy storage systems in renewable energy applications, such as solar and wind power systems.

Benefits and Limitations

The use of 21700 batteries in these industries offers several benefits, including:

High energy density: 21700 batteries have a higher energy density compared to other battery types, which means they can store more enegery in a smaller space.

Long lifespan: 21700 batteries have a similar lifespan to other lithium-ion batteries, typically lasting over 500 charge cycles. This can reduce the need for frequent replacements and save money in the long run.

High Discharge Rate: 21700 batteries can handle high discharge rates, which makes them ideal for use in high-powered devices like electric vehicles.

However, there are also some limitations to consider when using 21700 batteries, including:

Cost: 21700 batteries are more expensive than other lithium-ion battery types due to their increased energy density and superior performance.

Size and Weight: The 21700 battery is larger and much heavier than the popular battery sizes like 14500 and 18650, which may limit their use in certain applications.

Environmental impact: As with all lithium-ion batteries, 21700 batteries have an environmental impact and must be disposed of properly to minimize their impact on the environment.


Congratulations, you’ve made it to the end of this electrifying article on the 21700 battery! By now, you should be buzzing with excitement about all the benefits this battery size can offer.

From its high capacity to its compatibility with various devices, the 21700 battery is a powerful energy source that can keep you going all day long. Plus, with its eco-friendly and safe features, you can rest assured that you’re making a smart choice for both your devices and the environment.

So, what are you waiting for? Don’t let your devices run out of juice – invest in a high-quality 21700 battery today and see the difference it can make! Trust me, your devices (and the planet) will thank you for it.


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