Yes, 21700 batteries last longer than 18650 batteries in many ways. 

They have a longer overall lifespan because they can handle stresses better than a 18650 battery. They will last longer per charge because they are physically larger and more power dense so they can store more energy than an 18650 battery. And because they can deliver much higher currents than 18650 batteries, a 21700 battery will last longer in terms of how long it can run a load at a given current before that current begins to fall. 

What is the advantage of 21700 over 18650?

So, how does 18650 compare to 21700? In just about every way, a 21700 battery will last longer than an 18650. They are not twice as big as 18650s but they do often contain twice or more power energy than an 18650 cell. 21700s have more energy storage per cubic centimeter than 18650 cells. And if that's ever the case when comparing two batteries, then generally speaking you can say the one with more space is going to last longer. The one that's more power dense is going to last longer, especially if it has more space to take up.

There are still plenty of good applications for 18650s because they are so small. Sometimes they're the only option when you need to achieve a particular voltage in a given space, but that is exceedingly rare.

Applications of 21700 Batteries Compared to 18650 Batteries?

The versatility of 21700 batteries makes them an appealing option for a wide range of applications. Their increased capacity and power density make them particularly well-suited for use in electric vehicles, power tools, and energy storage systems. They are physically larger, which means they are going to have better thermal management and the ability to handle higher currents than 18650 batteries when all else is equal. This makes them ideal for applications where high power output and endurance are crucial.

18650 batteries are still a popular choice for smaller electronic devices like laptops, flashlights, and portable power banks, where compactness and lighter weight are important factors. For this reason, you will still see a lot of tool batteries that use 18650 cells. 

So, Why Do 21700s Last Longer Than 18650?

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There are several reasons why 21700 batteries last longer than 18650s. Here are some of the most important ones:

Higher energy capacity: As mentioned earlier, 21700 batteries have a higher energy capacity due to their larger size and increased power density. Currently, the highest capacity 21700 cell on the market is 5,000mAh, compared to the 18650 which is 3,500mAh. This means that they can store more energy, enabling them to last longer on a single charge. In turn, this can increase the overall cycle life which will prolong the life of the battery.

Better thermal management: 21700 batteries have a greater surface area, which allows for better heat dissipation. This is crucial for high-power applications, as heat buildup can cause battery degradation over time. Better thermal management not only ensures longer runtime but also helps maintain battery health, extending its overall lifespan.

Lower internal resistance: 21700 batteries generally have lower internal resistance than 18650 batteries, allowing them to deliver higher currents more efficiently. Lower internal resistance also means less heat generation within the battery, which further contributes to the prolonged battery life.

Improved chemistry and manufacturing techniques: Technological advancements in battery chemistry and manufacturing processes have allowed for the creation of 21700 batteries with better performance and longer lifespans. This includes optimizations in the materials used for the electrodes, separators, and electrolytes, which can contribute to improved cycle life, increased energy density, and enhanced safety features.

Optimized charge and discharge rates: 21700 batteries can handle higher charge and discharge rates without significant losses in capacity or increased heat generation. So, they can deliver power more consistently over time and maintain their performance for a longer period compared to 18650 batteries.