All You Need to Know About 21700 Battery

What is a 21700 Battery?

The 21700 battery is a high-performance lithium-ion cell that has gained widespread adoption in various industries due to its higher energy density, longer lifespan, and better thermal stability. Originally popularized by Tesla, the 21700 cell is now widely used in electric vehicles (EVs), power tools, medical devices, and energy storage systems.

Dimensions and Specifications of 21700 Battery

The name 21700 derives from its physical dimensions:

• Diameter: 21mm
• Length: 70mm
• Weight: Approximately 60-75g (varies by manufacturer and chemistry)

Key Performance Parameters:

• Nominal Voltage: 3.6V – 3.7V
  This is the average operating voltage of the battery during discharge. It provides a stable power supply to devices and is slightly higher than the 18650 battery, allowing for greater energy output. A higher nominal voltage contributes to increased efficiency in power delivery.
• Capacity: 3000mAh – 5000mAh
  The capacity determines how much charge the battery can store. Higher-capacity 21700 cells can power devices for longer periods, making them ideal for high-drain applications like electric vehicles and power tools. A larger capacity means fewer battery swaps and extended operational time.
• Charge Voltage: 4.2V (standard lithium-ion charging voltage)
  This is the maximum voltage the battery reaches when fully charged. Charging above this limit can lead to overheating and reduced lifespan, which is why a proper battery management system (BMS) is essential. Consistently charging within the recommended range enhances battery longevity.
• Discharge Cut-off Voltage: 2.5V – 3.0V
  This is the minimum voltage before the battery is considered depleted. Discharging below this range can cause irreversible damage to the battery and reduce its cycle life. Proper monitoring of voltage levels helps maintain battery health.
• Standard Discharge Current: 5A – 15A (higher for high-drain models)
  The discharge current determines how much power the battery can deliver at a given time. Higher discharge rates are necessary for applications like electric bikes, drones, and power tools. Ensuring the right discharge rate prevents excessive heat buildup and extends performance stability.
• Cycle Life: 500 – 1000 cycles (depending on usage and chemistry)
  Cycle life refers to the number of complete charge and discharge cycles a battery can undergo before its capacity significantly degrades. The cycle life varies based on factors like charging speed, discharge rate, and operating temperature. Using proper charging practices and avoiding deep discharges can significantly enhance the number of cycles.

Chemical Composition of 21700 Battery 

21700 batteries use different lithium-ion chemistries, including:

• Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC): Offers a balance of energy density, power output, and lifespan.
• Lithium Iron Phosphate (LiFePO4 or LFP): Known for safety, thermal stability, and long cycle life.
• Lithium Cobalt Oxide (LiCoO2 or LCO): Higher energy density but lower lifespan and safety.
• Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2 or NCA): Used in high-energy applications, such as EVs.

21700 Battery vs. 18650 Battery

The 21700 battery is often compared to the 18650 battery due to their similar usage in electronics and energy storage. Here is a comparison:

21700 Battery Packs

A 21700 battery pack is a collection of multiple 21700 cells connected in series or parallel to achieve desired voltage and capacity. 

How 21700 Battery Packs Are Configured

1. Series Connection (S): Connecting batteries in series increases the voltage while maintaining the same capacity. For example, if three 21700 cells with a nominal voltage of 3.7V and a capacity of 4000mAh are connected in series (3S), the total pack voltage will be 11.1V (3 × 3.7V) while the capacity remains 4000mAh.
2. Parallel Connection (P): Connecting batteries in parallel increases the capacity while maintaining the same voltage. If three 21700 cells with a capacity of 4000mAh and a nominal voltage of 3.7V are connected in parallel (3P), the total pack capacity will be 12,000mAh (3 × 4000mAh) while the voltage remains 3.7V.
3. Series-Parallel Combination (S-P): To achieve both higher voltage and higher capacity, batteries are arranged in a combination of series and parallel connections. For example, a 3S2P configuration means three cells in series (3 × 3.7V = 11.1V) and two such sets in parallel (2 × 4000mAh = 8000mAh).
4. Battery Management System (BMS): A BMS is integrated into battery packs to balance the charge among cells, prevent overcharging/discharging, and ensure safe operation. This is crucial for maximizing the lifespan and efficiency of the pack.
5. Thermal Management: Since lithium-ion cells generate heat during charge and discharge, heat dissipation strategies such as thermal pads, cooling fans, and ventilation systems are used to maintain optimal operating temperatures.         

21700 battery packs provide customizable configurations to meet different power and energy storage requirements, making them an ideal choice for a wide range of industrial and consumer applications.   

Advantages of 21700 Batteries

1. Higher Energy Density: More power storage in a similar footprint compared to 18650.
2. Longer Lifespan: Better cycle life with reduced degradation.
3. Enhanced Thermal Stability: Safer under high discharge conditions.
4. More Efficient Energy Storage: Reduces the number of cells needed for high-capacity battery packs. 
5. Versatile Applications: Suitable for automotive, industrial, and consumer electronics.

Common Applications of 21700 Batteries

• Electric Vehicles (EVs): Used by Tesla, Rivian, and other automakers.
• Drones and Robotics: Essential for long-flight drones and autonomous systems.
• Energy Storage Systems (ESS): Home and industrial solar energy storage.
• Medical Devices: Powering portable medical equipment.
• Power Tools: Cordless drills, saws, and garden equipment.

FAQs About 21700 Battery

1. What makes 21700 batteries better than 18650 batteries?
21700 batteries offer higher capacity, better energy density, and longer runtime.

2. Can 21700 batteries be used in all devices that support 18650 batteries?
Not always. The larger size of 21700 batteries requires compatible battery compartments.

3. How do I charge a 21700 battery?
Use a dedicated lithium-ion charger with correct voltage settings (typically 4.2V per cell).

4: Can 21700 batteries be used in cold climates?
A: Yes, low-temperature 21700 models work at -40°C.

5: What’s the lifespan of a 21700 battery?
A: 500-1,000 cycles, depending on depth of discharge and temperature.

Landazzle 21700 Battery Packs

At Landazzle, we manufacture high-quality 21700 battery packs designed for superior performance, reliability, and customization. Our solutions cater to drones, robotics, and aerospace and industrial applications.

Visit our website or contact us at info@landazzle.com for custom 21700 battery solutions tailored to your needs.