21700 vs 18650 Battery: The Ultimate Consumer Guide

If you’ve ever shopped for a high-performance flashlight, a vaping device, or even an e-bike, you’ve likely come across rechargeable batteries with names like “” or “.”

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So, what are and batteries? They are the two most popular types of cylindrical lithium-ion (Li-ion) cells powering countless modern electronics. The names are actually a simple code for their physical dimensions:

• A  battery is 18mm in diameter and 65mm in length.
• A  battery is 21mm in diameter and 70mm in length.

This seemingly minor size difference creates a major impact on performance, directly affecting a device’s power, runtime, and overall capability. This guide breaks down the key distinctions to help you understand which battery is the right choice for your needs.

What Are and Batteries?

These battery types are lithium-ion cells named after their physical dimensions, with each number representing millimeters of width and height. Both serve as rechargeable power sources in various electronic devices and applications.

Definition of Batteries

The battery measures 21mm in diameter and 70mm in length. The final zero indicates its cylindrical shape.

These cells typically provide 4,000-5,000mAh capacity depending on the manufacturer and chemistry. Tesla popularized this format when they adopted it for their Model 3 vehicles.

batteries deliver higher energy density compared to older formats. They can handle discharge rates up to 35A in high-drain applications.

The larger size allows manufacturers to pack more lithium-ion material inside. This results in longer runtime and better thermal management.

Definition of Batteries

The battery measures 18mm in diameter and 65mm in length. This format has been the industry standard for portable electronics since the s.

These cells typically offer 2,200-3,500mAh capacity depending on quality and chemistry. They remain the most widely available lithium-ion format globally.

batteries can handle discharge currents from 10A to 30A based on their design. Protected versions include built-in safety circuits.

Their compact size makes them ideal for space-constrained devices. Manufacturers produce billions of these cells annually.

History and Evolution of Lithium-Ion Cells

Sony introduced the first commercial lithium-ion battery in . The  format emerged in the mid-s as a standardized size for portable electronics.

Early cells provided only 1,100-1,500mAh capacity. Advances in cathode materials and manufacturing increased this to over 3,500mAh by .

The  format appeared around  when Tesla partnered with Panasonic for their Gigafactory production. Other manufacturers quickly adopted this larger standard.

Modern lithium-ion chemistry improvements include:

• Silicon-enhanced anodes for higher capacity
• Nickel-rich cathodes for better energy density
• Advanced electrolytes for improved safety

Battery manufacturers continue developing larger formats like cells. However, and remain the dominant cylindrical standards for most applications.

At a Glance: The Key Differences

While only a few millimeters separate them, the and batteries have distinct characteristics that define their performance.

Physical Size and Weight

The most obvious difference is size. The cell is physically larger, with a 77% increase in volume compared to the . It’s also slightly heavier. This extra space is not for nothing; it is the fundamental reason for the ’s enhanced capabilities.

Capacity (mAh) – How Long Can It Last?

Capacity, measured in milliamp-hours (mAh), tells you how much energy a battery can store. Think of it as the size of the fuel tank. A higher mAh rating means a longer runtime before you need to recharge.

• : A high-quality battery typically has a capacity ranging from 2,300 mAh to a maximum of about 3,600 mAh.
• : The larger cell can reach a maximum capacity of 5,000 mAh. This translates to a significant runtime advantage, often 40-50% longer than a top-tier .

For a user, this is a tangible benefit. Your flashlight runs longer on a camping trip, your e-bike takes you further, and your power tool lasts through more of the job on a single charge.

Power & Energy Density – How Strong Is It?

Beyond just runtime, the battery’s ability to deliver power is critical.

• Energy Density: This refers to how much energy can be packed into a given volume. The battery boasts a higher energy density—up to 20% more than the . It simply stores more power in a slightly larger package.
• Power Output: The larger size and improved chemistry of the allow it to deliver power more efficiently and handle higher discharge rates. This means devices can achieve more demanding performance levels. A fantastic real-world example is found in high-end flashlights. A Fenix flashlight equipped with a battery might offer a -lumen “turbo mode,” whereas the exact same flashlight using a (with an adapter) may only be able to reach lumens because the battery can’t supply the necessary power for the brightest setting.

Cost and Availability

• : As the established industry standard for over a decade, the is generally more affordable per cell. It’s produced by a vast number of manufacturers and is widely available.
• : The cell can be more expensive to buy individually. However, its higher energy density means it often has a lower cost per kilowatt-hour (kWh). This is why it’s becoming the standard for large-scale applications like electric vehicle battery packs, where overall energy cost is more important than the cost of a single cell.

Deep Dive: The Pros and Cons

So, which one is right for you? Let’s break down the advantages of each.

Why Choose a Battery? (Pros)

• Superior Runtime: This is its killer feature. If you need the longest possible time between charges, the is the undisputed winner.
• Higher Performance: It can power more demanding devices and unlock the highest performance settings that a might not be able to handle.
• Future-Proofing: An increasing number of manufacturers are designing their new, high-performance products around the format.

Cons:

• Larger and Heavier: The increased size and weight make it unsuitable for compact devices where space is a premium.
• Limited Compatibility: It will not fit in the vast number of devices designed for the standard.
• Higher Upfront Cost: Individual cells are typically more expensive than their counterparts.

When is a Still the Right Choice? (Pros)

• High Cost-Effectiveness: If you’re on a budget, the upfront cost of a battery is lower.
• Wide Compatibility: A massive ecosystem of devices was built for the . If you have older or more standard electronics, this is likely the battery you need.
• Compact and Lighter: In applications where every gram and millimeter counts, the smaller and lighter is the ideal choice.
• Sufficient Power: Let’s be clear: for the vast majority of everyday uses, a high-quality provides more than enough power and capacity.

Cons:

• Shorter Runtime: Its lower capacity means it requires more frequent recharging.
• Lower Power Output: It cannot power the most demanding devices or unlock the highest performance modes that s can.
• Becoming Outdated for High-Drain Use: While still very common, it is being phased out in favor of the for new, high-drain applications.

Common Applications: Where You’ll Find These Batteries

You’ll find these powerhouses in a surprising number of places.

Applications:

• Laptop battery packs
• Older high-performance flashlights and headlamps
• Many power tools
• Drones
• Specialized medical devices
• Early Tesla models (Model S and Model X)

Applications:

• Modern Electric Vehicles (notably the Tesla Model 3 and Model Y)
• The latest generation of high-performance flashlights
• E-bikes and electric scooters
• Vaping mods and E-cigarettes
• Portable power stations and solar generators

Conclusion: Which Battery Should You Choose?

Ultimately, the “better” battery is the one that fits your device and meets your needs. There’s no single right answer.

• Choose the if: Your primary goal is getting the longest possible runtime and the absolute highest performance from a device that is specifically designed to support it.
• Choose the if: You are looking for a reliable, affordable, and widely available battery for a compatible device, and your power needs are within the standard range.

The most important takeaway is this: Always check your device’s specifications to confirm which battery type it supports before making a purchase. Using the wrong size or type of battery can be inefficient at best and unsafe at worst. By understanding the simple numbers on the label, you can ensure you’re getting the perfect fuel for your favorite gadgets.

Here are some MF Opto products that use and batteries, which you can recommend at the end of your blog post:

Power Your Adventures with MF Opto Lighting Solutions

At MF Opto, we offer a wide range of high-performance flashlights, headlamps, and work lights that utilize these powerful lithium-ion cells.

For a Balance of Power and Portability: Battery Products

The battery is a versatile and reliable power source, making it a popular choice for a wide range of our products. Its balance of capacity and size makes it ideal for everything from everyday carry flashlights to powerful headlamps for outdoor adventures.

Here are some of our top products that use batteries:

Solar-Powered LED Spotlight with 4 Modes and Emergency Flash

180° FoldableMagnetic LED Collapsible Work Light

Detachable Magnetic Lamp with Motion Sensor

Powerful LED Spotlight with Dual Light Sources

Zoomable LED Flashlight with Soft Light Cover & Hanging Hook

For Maximum Power and Runtime: Battery Products

When you need the longest possible runtime and the highest performance, our products equipped with batteries are the ideal choice. The higher capacity of these cells makes them perfect for heavy-duty applications and professional use.

Portable LED Work Light with Stand & Power Bank

You can explore our full range of products to find the perfect and powered solution for your needs. Contact us for bulk order pricing!

No matter which battery type you choose, MF Opto is committed to providing innovative and reliable lighting solutions. Explore our products today and find the perfect light to power your next adventure.

Frequently Asked Questions (FAQs)

1. What do the numbers “” and “” actually mean?

The numbers are a direct reference to the battery’s physical dimensions. A  battery is 18mm in diameter and 65mm long. A  battery is 21mm in diameter and 70mm long.

2. Can I use a battery in a device made for a ?

No, not directly. A battery is physically larger and will not fit in a device designed for a battery. While some devices (like certain flashlights) may offer an adapter sleeve to use a cell in a -sized compartment, you can never go the other way. Never force a battery into a device it is not designed for.

3. Is the battery replacing the ?

The is becoming the new standard for many new, high-performance devices, especially in the electric vehicle and high-end electronics industries. However, the is so widely used that it will remain a relevant and readily available battery for many years to come.

4. Are batteries more expensive?

Individually, a single cell is often more expensive than a single cell. However, because it holds more energy, the often has a lower cost per unit of energy (cost per kWh), making it more economical for large battery packs like those in an EV.

1.What is the battery?

The battery is another lithium-ion battery, and the number denotes the cell size. It comes in 21mm in diameter and 70mm in length. The  battery comes with an ampere power between mAh and mAh.

While compared to lithium batteries, it is more significant in length and diameter. The lithium ion battery has a technical design to offer a voltage range between 2.5v to 4.2v and a charging voltage of 4.2v. However, the nominal voltage of battery  will be 3.7v. The battery requires about 5 hours for a full recharge, but the charging time may vary subject to the charger voltage, amperage, and battery type.

2.How much does a battery cost?

The price of a lithium ion battery or any other battery depends on various factors. The price may vary depending on the brand's popularity, charging and discharging cycles, battery chemistry, power capacity, protective features, etc. On a general perception, the cost of a battery is between $6.95 to $28.95.

3.What is battery used for?

Like lithium batteries, cells also power many electronic and luminary devices. These batteries are used on flashlights, and electric vehicles. Since these batteries are rechargeable, they can use in all devices that come with built-in rechargers and need a voltage requirement of 3.2/3.7v.

4.How long does a battery take to charge?

A battery pack can typically charge within 4 hours; however, the charging time depends on the charger and battery capacity. You can quickly recharge a battery with a fast recharger than with a slow recharger.

These statistics show that you must use a recharger with a higher capacity for quick recharging.

The lithium ion battery comes with -mAh, so you should use a charger matching the battery capacity for fast charging. If you use a 2A charger to recharge a mAh battery, it will take about 2 hours to complete the charging. Similarly, if you use a 1A charger, the recharging timing will be approximately 3-4 hours.

5.How much does a battery weight?

The weight of a battery will be between 55gms to 75gms, depending on the technology and capacity.

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6.Are the same as ?

Both and cells are not the same. Their physical dimension is different to one another. When comes with 18mm diameter and 65mm length, the battery comes with 21mm diameter and 70mm height. The last digit '0' denotes its cylindrical shape. Both are identical in shape, i.e., both are cylindrical. However, is slightly bigger than ; hence,when the battery type is the same, can offer more power than batteries.

On the capacity segment, offers mAh to mAh, while offers mAh to mAh. Both can provide 3.7v output, but the output current of lithium-ion battery is more than 36Amps, but battery offers more than 25Amps.

lithium ion battery has 35% more cell capacity than batteries. Similarly, the energy density of a battery also shows an increment of 20%. As per the data released by Tesla, the energy density of was 250Wh/kg, but when they started using batter, the energy density registered as 300Wh/kg. The energy density of battery in volumetric terms stands 20% higher than batteries.

The volume of a battery is cubic mm, and  battery is cu mm, which means the latter has ~47% more volume. If we consider 10-12% of the volume space used to incorporate the protective features, the batteries still have room to produce more power. So, considering all these factors, and batteries are not the same. Since  battery has extended battery life and high output, it has a better edge over batteries.

7.Which battery is better vs ?

In the lithium battery segment, bigger batteries have high power delivery advantage than smaller batteries. Bigger batteries will have extended battery life than smaller batteries and a better amp rating. While comparing and battery, both have the same length, but one has a 20mm diameter, and the other has a 21mm diameter. Even though both have no considerable difference, batteries shall have a better amp rating and can discharge 30-45 amps continuously.

8.Can I Use batteries in my vape?

Yes, you can use lithium ion batteries in the vaping device. These batteries are the upgraded version of and batteries. The lithium ion batteries are larger than and , hence can deliver more amps continuously. Many companies are using lithium ion batteries for their vaping devices.

9.Are all batteries rechargeable?

The lithium ion batteries are rechargeable. Because of this, it has been used in electric vehicles, vaping devices, flashlights, and many other devices that require power to operate.The beauty of batteries is their size and power delivery capacity. Let us examine a projected situation to understand the convenience of using lithium ion batteries instead of other batteries.

Suppose you want to run a BTU cooling capacity air conditioner that consumes about watts per hour; you can run the air conditioner for one hour by using a battery pack of 74 cells. But to accomplish this task, you must use a lithium ion battery with 3.7v and mAh that can store 3aH to 5aH power and store about 11–18-watt hours.

①Limits of Recharging

All lithium-ion batteries are rechargeable, and they will have a limited recharge cycle. Due to chemical degradation and oxidation, the battery recharging cycle gets degraded over a period. All batteries do have these issues. The lithium ion batteries feature - cycles.

② Recharge Frequency of Batteries

Lithium batteries come with a rechargeable feature, and a battery will have - recharge cycles. So, your recharging pattern will decide the battery life. When your battery voltage reduces to 3v from 3.7v, you can put it for recharge. Frequent recharging may reduce the life of the battery, but not so for lithium-ion batteries. Because lithium-ion batteries have no memory effect.. Therefore, instead of going for a regular recharge, check the voltage level, and if it drops below 3v, do a recharge. If a lithium-ion battery voltage drip down to 2.5v, the battery may lock by itself, making it impossible to recharge using an ordinary recharger.

10.Which battery is best?(samsung,lg,panasonic,sony, which is best? )

In the best battery segment, Panasonic stands top. The mAh battery shows a continuous discharge rating of 30A and a nominal voltage of 3.7v. Because of the constant high voltage delivery, it reduces battery usage. The rechargeable battery offers + life cycles, and it can deliver 75 watts. It's high energy density minimizes the battery weight and size. These batteries are famous for their efficiency and can use for an extended period. The battery does not have any memory accumulation issues; hence you can always get a full charge after every recharge.

The LG50 lithium-ion battery is available with an energy capacity of mAh with a nominal voltage of 3.6v is our 2nd preference. The battery can offer a full charge voltage of 4.2v with a variation of +/- 0.05v. With a maximum continuous discharge rate of 7.27A and discharge cut-off voltage of 2.50v, this is an ideal battery for electronic devices that consume low power for an extended period. The battery comes with 500 recharge cycles, but you can recharge it + cycles if appropriately used. It is an unprotected battery, so it is best to use a protected battery management system.
Our third preference is the Sony lithium-ion battery USVTC6A which comes with mAh. It can offer a 40A continuous discharge at a 3.6v nominal voltage and a maximum of 4.2v. It is rechargeable but unprotected. You should use it with a protected battery pack. With a 9A recharger, it can recharge quickly and can let you have 500+ recharge cycles. It sells for US$9 per piece, and with a 3-year shelf life, it is a good option for using high-drain electronic devices that require minimum discharge rates.

Among various lithium ion batteries, Samsung 40T (Lithium Manganese Nickel -LiNiMnCoO2) has better market acceptance than the rest of the competitors and is one of the famous brands. The battery comes with mAh and can deliver 25A continuous power discharge with a maximum discharge current of 35A or 45A with a temperature cut off mark at 80°C. It can let you use 75W continuously without any break for an extended period. It comes with 250+ cycles with a 6A charger and can recharge more than 500 times if appropriately recharged. The battery’s market price is about $7.50 per unit.

Model

Size

Chemistry

Voltage

Capacity

Discharge

Cycles

Panasonic

21x70

INR

3.56v-3.6v

mAh

15A-20A

+

LG50

21x70

INR

3.63v

mAh

7.27A

+

Sony VTC6A

21x70

INR

3.6v-3.7v

mAh

30A

500+

Samsung 40T

21x70

INR

3.6v-4.2v

mAh

35A

250+

11.Dose Tesla use battery

①Are the same as ?

Previously Tesla has been using lithium batteries to power their electric vehicles. Now they are using cells for new model electric vehicles. As per the data released by Tesla, the energy density of lithium ion batteries is 20% more than batteries. The increased energy density is mainly attributed to the size and new battery chemistry.

Another critical aspect of batteries compared to batteries are their price. As per the data released by Tesla, the cost is less by 9% compared to batteries, which was about $185. The cost of batteries stands around $170. When the system costs about $171 per MH, the will be 9% less and may touch about $155 per Zhn.As per industry experts, the component and weight can also be reduced by 10% by using lithium-ion batteries rather than batteries. So, if the weight of the battery is less, that will eventually have an advantage over the energy density of the vehicle.

② Tesla battery

Tesla has been using batteries for their S and X model vehicles, but for the new Model 3 cars, they are using batteries. These batteries have 46% more cell volume than batteries. Also, as per a report released by Tesla, they are 15% more energy efficient. They have a cell capacity of 21.275Wh and show an energy density of ~877.5Wh/L.

12. Lithium-ion Batteries - Final thoughts

The lithium ion batteries are the best-preferred option for electronic devices and electric vehicles because it comes with ~35% more cell capacity and hence can produce 20% more energy than batteries. These batteries show moderate resistance to temperature fluctuations and short circuit issues. So, they are ideal for devices that require low power drain for an extended period.

The lithium ion batteries are rechargeable, and by using quick rechargers, you can get the battery charged to the required voltage level. Another highlighted feature of the best lithium on batteries is their nominal voltage discharge rates. They can deliver 3.7v on average and can deliver a maximum of 4.2v.

However, while purchasing the best lithium-ion battery, you need to check its mAh and discharge rates, marked as C-rate. If the discharge is too high, then there is no point in having a battery with high capacity. On average, lithium-ion batteries will have a power capacity of to mAh, but they should also have a corresponding slow discharge rate.

When the discharge rate is very high, it will drain your battery quickly. So, the best way to ensure the discharge rate is whether the C-rate matches the power capacity. If the power capacity is mAh, then the C-rate should be 30A, and if the power capacity is mAh, then the C-rate should be 50A. Any discharge rate more than the corresponding power capacity will fail to give the expected result. Similarly, check the battery's nominal average voltage level.

Any  lithium ion battery with a nominal voltage of 3v is good if it matches your device’s requirement. So, you must check the nominal voltage requirement before deciding on the battery and make sure the battery can match the voltage requirement with the nominal voltage offered by the battery.All cells may look the same in their physical appearance because of their size, 21mm diameter and 70mm length. However, their internal chemistry will be different from one another; their power output, continuous discharge rate, maximum power capacity, and voltage may vary according to the brand and model. Some batteries have protected features, and some don't have that feature. Therefore, you must select battery, matching the device's voltage and power requirement; otherwise, it may damage your device.

Contact us to discuss your requirements of Lithium Cells. Our experienced sales team can help you identify the options that best suit your needs.