21700 VS 18650 Battery, Which is batter?
The 18650 battery has been in development for many years.The technology is relatively mature compared to other types of batteries.However, it still faces problems such as high calorific value, complex grouping and inability to realize fast charging.Therefore, the 21700 cylindrical ternary battery was born in this context.
What are 21700 and 18650 lithium-ion batteries?
21700 batteries and 18650 batteries are short for rechargeable lithium-ion batteries. It’s used to power devices as diverse as flashlights and e-cigarette accessories. Like other lithium-ion batteries, the 21700 battery is named after its size for quick identification of size and compatibility. For example, the 21700 battery is 21 millimetres in diameter and 70 millimetres long.So the exact size of the 18650 battery is 18mm in diameter and 65mm in length.
Applications
Different products and appliances have different needs of energy , volume , current and weight efficiency. The performance of the 18650 and 21700 cells varies depending on the quality of their manufacture.
Applications of 18650 Lithium-ion Battery: The 21,700 lithium-ion batteries, which offer a 35 percent increase in capacity over existing batteries, can be used in a wide range of power tools, laptops,E bikes and other devices. And soon become the new standard of cylindrical batteries.
Applications of 21700 Lithium Battery: The 18650 battery is commonly used in electronic devices, laptops, drones, flashlights and Vaping.And even some electric cars, but it use 18650 Lithium-ion battery pack. For example,Tesla typically uses Panasonic’s 18650 battery pack, which has 7,104 cells.
Main features
21700 battery cell
- High energy density: Ideal for high capacity battery packs.
- Low Priming: Quickly charge rate and does not need prolonged charging.
- High price: the manufacture cost of 21,700 lithium-ion batteries are expensive .And also due to their higher output capacity.
18650 battery cell
- Efficiency: 18650 Batteries have a good balance between the amount of energy produced and the rate of continuous discharge. Also,they are highly efficient.
- Cost effective: The 18650 battery has the largest market.This made the 18650 battery more economical to manufacture.
- Improvements: The capacity and efficiency of the 18,650 cells are continuously improved each year.It is a good choice for emerging technologies, as more efficient battery packs are emerging.
21700 Vs 18650
Size: This difference is the most obvious between the 18650 and 21700 Lithium-ion Batteries.
Capacity: The general rule of lithium-ion batteries is that the bigger the volume for higher capacity.
Energy Density: According to Tesla’s disclosure data, the early 18650 battery system had an energy density of about 250Wh/kg.Later, the Tesla 21700 battery system has an energy density of about 300Wh/kg, making the volume energy density of the 21700 battery nearly 20% higher than the original 18650.
System cost: According to Tesla’s disclosed battery pricing information, 21700 lithium-ion battery system costs $170 / hour ,and the 18650 lithium-ion battery system costs $185 / hour. So, the cost of the battery system can be reduced by about 9%, if 21,700 cells are installed on the Model3.
Weight of the system: The volume of 18650 is smaller than 21700. As the capacity of a single battery increases, the energy density of a single battery becomes higher. So the amount of energy required for a single battery can be reduced by a third. It reduces the difficulty of system administration, and reduces the number of metal structures and electrical components in the battery pack. Furthermore reducing the weight of the battery. Thus,when Samsung SDI switched to 21,700 new batteries, it found that the system was 10% lighter than the existing battery.
Conclusion
21700 battery maintains the high reliability and stable performance of 18650 battery. Compared with 18650 battery, the performance of 21700 battery has been greatly improved in all aspects. In addition, in terms of raw material selection, manufacturing process, technical flow,compared to other battery models, the 21700 is similar to the more mature 18650 battery. Therefore, Therefore, they can be compatible in most of the production lines. And some enterprises work more safely on the production line, closer to the compatibility of the 21700 and 18650 production lines.
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21700 vs 18650: specifications at a glance
| Specification | 18650 | 21700 |
|---|---|---|
| Diameter | 18 mm | 21 mm |
| Length | 65 mm | 70 mm |
| Volume (approx.) | 16.5 cm³ | 24.2 cm³ |
| Typical capacity | 1,800–3,500 mAh | 3,000–5,000 mAh |
| Nominal voltage | 3.6–3.7 V | 3.6–3.7 V |
| Energy per cell | 6.5–12.6 Wh | 11–18 Wh |
| Weight (approx.) | 45 g | 70 g |
| Typical continuous discharge | 5–10 A | 10–20 A |
21700 battery dimensions and size
The name is the size: a 21700 cell is 21 mm in diameter and 70 mm long (about 0.83 × 2.76 in), and an 18650 cell is 18 mm in diameter and 65 mm long (about 0.71 × 2.56 in). Because volume scales with the square of the diameter, the 21700 has roughly 42% more volume than the 18650 — the geometric source of most of its extra capacity.
21700 battery capacity and energy
A quality 21700 delivers around 3,000–5,000 mAh, roughly one and a half times the capacity of a common 18650. At 3.6 V nominal that is about 11–18 Wh per cell, so a 13S4P 21700 pack reaches roughly 700–900 Wh, while the equivalent 18650 pack lands nearer 450–650 Wh in the same envelope.
Energy density: is the 21700 actually better than the 18650?
On gravimetric energy density the two are close — both land around 200–270 Wh/kg at cell level — because both use the same chemistries. The 21700 wins on volumetric density and on system overhead: a pack built from larger cells needs fewer cans, fewer welds, fewer holders and a smaller BMS, so the finished pack packs more energy into the same space. That is why power tools and EVs moved to 21700, and why cells such as ours are specified cell by cell rather than by total count — see how energy density is measured and compared.
Which cell should you choose?
| Application | Typical choice | Why |
|---|---|---|
| Flashlights, small devices | 18650 | Cheap, universal, easy to source |
| E-bike, e-scooter packs | 21700 | Fewer cells per pack, higher capacity, better pack density |
| Power tools | 21700 | Higher continuous current per cell |
| EV traction | 21700 (or larger) | Lower cost per kWh at pack level |
| Custom LiFePO4 storage | Prismatic LFP | Cylindrical ternary cells suit power, not stationary storage — see how we build a 72 V e-scooter pack |
21700 battery FAQs
What does 21700 mean on a battery?
The number is the physical size in millimetres: 21 mm diameter and 70 mm length. The same convention gives the 18650 its name (18 mm × 65 mm).
Are 21700 batteries better than 18650?
Per cell, a 21700 stores more energy and handles more current; per kilogram, the two are similar. For a pack that has to be light and small, the 21700 usually wins on pack-level density.
Can I replace 18650 cells with 21700 cells?
Not in the same holder — the 21700 is larger in both dimensions. Swapping requires a new holder, new spacing and a re-check of the BMS current limits.
What is the 21700 cell voltage?
Nominal voltage is 3.6–3.7 V for the common NMC/NCA versions, charged to 4.2 V and cut off near 2.5–3.0 V.
Need a quote? Tell us your voltage, capacity and current requirements and we will match the right cell format for your pack — factory-direct, no obligation.
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