Are 21700 Batteries Better Than 18650?

With battery technology continuously improving, 21700 lithium-ion batteries have emerged as a new player, sparking plenty of comparisons to the tried-and-true 18650 battery. So when it comes to 18650 vs 21700, which one reigns supreme?

When looking at the 18650 vs 21700 debate, it’s clear that each battery format has its benefits depending on your specific needs. 21700 batteries offer increased capacity and discharge rates thanks to their larger size. However, 18650 batteries still work well for compact electronics and remain easy to source.

To help determine if 21700 batteries are better for your application, as a professional lithium battery manufacturer, let me break down how these two popular lithium-ion battery types compare across several key factors.

18650 Batteries vs 21700 Batteries

Size and Design

The numbers 18650 and 21700 refer to the size of each cylindrical battery in millimeters. Specifically:

• 18650 batteries are 18mm wide x 65mm tall
• 21700 batteries are 21mm wide x 70mm tall

So while their voltage may be the same at around 3.6-3.7 volts, 21700 batteries are a bit chunkier. However, they’re still under 1 inch wide, allowing 21700 cells to work with many existing battery sleds.

Both battery types come in protected and unprotected versions. Protected cells contain a BMS chip for safety cutoffs and charge/discharge protection.

Capacity

The main advantage of 21700 over 18650 batteries lies in their increased capacity, which more efficiently utilizes the additional space inside 21700 cells.

Typical capacities include:

• 18650 batteries: 2000-3500 mAh
• 21700 batteries: 3000-5000+ mAh

So on average, a 21700 battery holds over 40% more capacity compared to 18650 cells. All that extra juice means 21700 batteries can theoretically power your devices considerably longer before requiring a recharge.

Discharge Rate

Thanks again to more internal space, 21700 cells support discharge rates up to 75A, handily beating most 18650 batteries that top out below 35A continuous discharge.

Higher discharge Ability translates into devices capable of higher power draw. For example, the same power tool outfitted with a 21700 battery would run faster, harder and longer compared to using lower-output 18650 cells.

Energy Density

Energy density measures how much energy a battery can store per unit volume. And thanks to their optimized size, most 21700 cells achieve an energy density around 20% higher vs 18650 batteries.

More energy packed into the same space means longer runtimes from 21700 battery packs without increased size or weight.

Availability

Given their popularity in laptops, power tools and other devices, 18650 batteries currently enjoy wider availability among major battery brands. Everyone from Samsung to Sony produces their own 18650 cells.

The 21700 battery market is admittedly smaller but growing. Still, major battery makers are quickly ramping up 21700 cell production to meet increasing demand.

Cost

Due to sheer production volume, 18650 cells tend to rate as the more budget-friendly option, at least for now. However their lower capacity means needing more 18650 cells to achieve the same battery pack voltages as 21700 options.

And as 21700 production scales up to the level of 18650, economies of scale should translate into 21700 cells boasting better cost-per-mAh in the near future.

So Are 21700 Batteries Better Than 18650 Overall?

While the 21700 vs 18650 battle contains nuances, 21700 batteries take the win in most head-to-head performance metrics.

21700’s optimally sized cylindrical format unlocks considerably more capacity and current ability compared to 18650 alternatives. And their slowly descending price coupled with rising availability bodes well for 21700 cells to become a battery of choice across many industries.

However, longer-proven 18650 batteries still work excellently for low-current devices. Their smaller format also makes 18650 cells ideal when tiny size remains critical, like powering compact wearables.

But for most high-drain uses – whether electric vehicles, power tools or battery banks – 21700 batteries are better. Their abundance of capacity means delivering far longer runtimes and better performance than 18650 batteries could ever reliably achieve.

So if given an option, choosing 21700 over 18650 cells often makes perfect sense if your device can leverage 21700 capabilities… with the longer run times and high-powered operation representing only the start of advantages these larger-format cylindrical cells provide.

Key Points: Differences Between 18650 and 21700 Batteries

• 21700 batteries have a larger physical size at 21mm x 70mm compared to 18650 at 18mm x 65mm
• 21700 cells offer 40%+ more capacity on average (3000-5000 mAh) versus 18650 (2000-3500 mAh)
• 21700 batteries achieve higher continuous discharge rates, typically over 75 amps vs under 35 amps for 18650
• 21700 cells boast around 20% greater energy density thanks to increased internal volume
• 18650 batteries currently benefit from greater production volumes and availability
• Price per mAh should favor 21700 batteries as production scales up to meet demand