Cylindrical Lithium-Ion Batteries for UAVs

Drone Battery

ENOV High-Energy drone batteries power industrial and commercial drones. Delivering 220–320 Wh/kg energy density, they enable long flight times (30+ mins) and support fast charging (2C). Perfect for aerial photography, surveillance, and delivery drones.

1. Basic Definition and Core Characteristics

Cylindrical lithium-ion batteries for UAVs are cylindrical-shaped batteries that utilize lithium-ion technology. With their mature production process and stable performance, they occupy specific application scenarios in the UAV field. Their core structure consists of a cylindrical metal casing, inside which key components such as electrodes, separators, and electrolytes are enclosed. These batteries are combined into battery packs through multiple cells to power UAVs, ensuring both safety and stability of the power supply.

In terms of core performance, this type of battery has advantages in multiple aspects. It exhibits good energy density, capable of storing a sufficient amount of energy within a limited size to meet the basic endurance requirements of UAVs, though there is still room for improvement compared to pouch batteries. It also has a long cycle life; most products can achieve 500-1000 charge-discharge cycles, and some high-quality models can even last longer, reducing long-term usage costs. Additionally, it features low internal resistance. Due to the short distance between polar materials and electrolytes, there is less energy loss during the charge-discharge process, ensuring efficient power output. Safety is guaranteed through multiple designs, such as a robust metal casing for impact resistance and overcharge/over-discharge protection mechanisms in some models, minimizing usage risks.

2. Common Models and Key Parameters

(1) Mainstream Models and Their Characteristics

• 18650 Model: With a diameter of 18mm and a height of 65mm, it is a classic model with mature technology. The capacity of a single cell typically ranges from 2000mAh to 3500mAh, and the nominal voltage is 3.7V (4.2V when fully charged). It has stable performance and is not only widely used in various electronic devices but also finds extensive application in the UAV field, especially suitable for scenarios with high requirements on cost and stability.

• 21700 Model: Boasting a diameter of 21mm and a height of 70mm, it is larger in size than the 18650 model. The capacity of a single cell can reach 4000mAh-5000mAh, with higher space utilization and energy density. It is gradually becoming the mainstream choice and is suitable for UAVs with high endurance requirements, effectively extending the flight time of UAVs.

• 26650 Model: It has a relatively large capacity but also a higher weight, with a diameter of 26mm and a height of 65mm. It is mainly used in high-power or industrial-grade UAVs, capable of providing continuous high-power output for UAVs to meet the operational needs in industrial scenarios.

• Other Special Models: Models such as 18350 and 14500 are small in size, with low single-cell capacity and power. They are only suitable for small UAVs or special scenarios, such as micro aerial models that have strict restrictions on battery size and weight.

(2) Interpretation of Core Parameters

• Voltage: The nominal voltage of a single cell is generally 3.6V-3.7V, and the full-charge voltage is approximately 4.2V. In actual UAV applications, multiple cells need to be connected in series to meet the voltage requirements. Common combinations include 2S (7.4V), 3S (11.1V), 4S (14.8V), and 6S (22.2V). The specific number of series-connected cells is determined by the voltage requirements of the UAV motor.

• Capacity: The capacity range of a single cell is 1500mAh-5000mAh. In practical applications, the total capacity can be increased by connecting multiple cells in parallel. For example, a 2P combination (two cells in parallel) can double the total capacity. Capacity directly affects the endurance time of UAVs; the larger the capacity, the longer the theoretical endurance. However, a balance between weight and flight performance must be struck.

• Discharge Rate (C Rating): The discharge rate of ordinary models ranges from 1C to 10C, suitable for UAVs with low-speed and low-maneuverability requirements. High-rate models can reach 15C-30C, and some special models even have higher rates, which can meet the demand for instantaneous large currents in UAVs such as aerial photography UAVs and racing UAVs. The calculation method is: Maximum continuous current = Capacity (Ah) × Discharge rate (C). For example, a 3000mAh (3Ah) 20C battery has a maximum continuous current of 60A.

• Energy Density: Usually ranging from 200Wh/kg to 300Wh/kg, there are differences among different models. The energy density of the 21700 model is generally higher than that of the 18650 model. The higher the energy density, the more energy the battery can store under the same weight, which helps to increase endurance while controlling the weight of the UAV.

3. Battery Pack Configuration Methods

Cylindrical lithium-ion batteries for UAVs need to be combined into battery packs through series (S) and parallel (P) connections to match the voltage and capacity requirements of UAVs. Common configuration methods are as follows:

• 4S1P: 4 cells are connected in series, with a total voltage of 14.8V. The total capacity is the same as that of a single cell (e.g., if a single cell is 3000mAh, the total capacity is 3000mAh). It is suitable for UAVs with certain voltage requirements and moderate capacity needs.

• 6S2P: 6 cells are connected in series, and then this series group is connected in parallel with another group of 6 series-connected cells. The total voltage is 22.2V, and the total capacity is twice that of a single cell (e.g., if a single cell is 3000mAh, the total capacity is 6000mAh). It is suitable for industrial-grade UAVs or large-scale aerial models with high voltage and high capacity requirements.

In addition, battery packs are usually equipped with a balance connector (such as an XT60 plug) for balanced charging of multiple cells. This ensures that the voltage of each cell remains consistent during charging, preventing the battery pack’s lifespan and safety from being affected by overcharging or undercharging of individual cells.

4. Advantages and Disadvantages Analysis

(1) Advantages

• Cost Advantage: Mature industrialized mass production leads to high production efficiency. Compared with pouch batteries and prismatic batteries, the cost per unit capacity is lower, making them suitable for users sensitive to budgets or low-cost UAV projects, such as low-end aerial models and training aircraft.

• Structure and Durability: The metal casing has good impact resistance and damage resistance, which can withstand vibrations and minor collisions during UAV flight to a certain extent. Meanwhile, the metal casing helps with heat dissipation, reducing performance degradation or safety risks of the battery caused by overheating.

• Replacement Flexibility: The battery pack is composed of independent cells. When a single cell is damaged, the damaged cell can be replaced individually without replacing the entire battery pack, reducing maintenance costs and extending the overall service life of the battery pack.

• Reliability: With a long and mature application history, its technical stability has been verified by the market. Under normal use and maintenance conditions, there is little performance fluctuation and a low failure rate, making it suitable for scenarios with high reliability requirements.

(2) Disadvantages

• Weight and Energy Density: The metal casing increases the battery weight, resulting in lower energy density than pouch lithium-polymer batteries (LiPo). For the same energy, cylindrical batteries are heavier, which increases the load of the UAV and affects flight endurance and maneuverability. They are particularly not suitable for consumer-grade UAVs with high lightweight requirements.

• Assembly Complexity: Multiple cells need to be assembled into a battery pack through welding or dedicated connectors. The assembly process has high technical requirements. Improper operation may lead to poor contact, short circuits, and other issues, increasing usage risks. At the same time, the fixed cylindrical structure also limits the design flexibility of UAVs, making it difficult to adapt to the fuselage of special shapes.

• Discharge Performance: The overall discharge rate is lower than that of pouch batteries. Ordinary models are difficult to meet the needs of UAVs with high maneuverability and high burst power requirements, such as racing UAVs and stunt performance UAVs. In high-intensity flight scenarios, problems such as insufficient power supply and rapid voltage drop may occur.

• Safety Hazards: Although the metal casing provides a certain degree of protection, under extreme conditions (such as severe collisions, overcharging, and high-temperature environments), the internal gas accumulation is difficult to release quickly, which may cause the casing to deform, crack, or even trigger safety accidents such as short circuits and fires. Moreover, some low-end models lack comprehensive safety protection functions.

5. Application Scenarios

Although cylindrical lithium-ion batteries for UAVs are not the mainstream choice for UAV power batteries, they have irreplaceable value in specific niche markets. The main application scenarios are as follows:

• Long-Endurance UAVs: Such as surveying and mapping UAVs, power inspection UAVs, and agricultural plant protection UAVs. These UAVs prioritize endurance over high maneuverability. Cylindrical batteries have a long cycle life and low cost, and can provide stable endurance support through multi-cell combination, meeting the needs of long-term operations and reducing operating costs.

• Low-Cost Aerial Models and Training Aircraft: For entry-level users or flight training scenarios, the requirements for battery performance are not high, and more attention is paid to cost control. Cylindrical batteries are low in price and can meet basic flight needs, making them suitable as power sources for novice practice or low-cost aerial models, reducing initial investment.

• Backup Solution for Industrial-Grade UAVs: Some industrial-grade UAVs use cylindrical battery packs as backup power sources to reduce costs or improve safety. When the main power supply fails, the backup cylindrical battery pack can supply power temporarily to ensure the UAV returns safely, avoiding equipment damage or mission interruption.

• Special Small UAVs: Such as micro reconnaissance UAVs and DIY small UAVs. Due to size and weight limitations, they cannot carry large batteries. Small cylindrical batteries such as 18350 and 14500 are small in size, can adapt to the design needs of such UAVs, provide basic power support, and meet the short-term flight tasks in specific scenarios.

6. Usage and Safety Precautions

(1) Charging Specifications

• Use a dedicated balanced charger and select a matching charging mode based on the number of series-connected cells (S number) and the type of the battery pack to avoid improper charging caused by using a universal charger.

• Monitor the battery voltage during charging to ensure that the voltage of a single cell does not exceed 4.2V (full-charge voltage). At the same time, avoid overcharging. Disconnect the power supply in a timely manner after charging is completed to prevent battery damage or safety accidents caused by overcharging.

• Do not charge the battery unattended. The charging environment should be well-ventilated, away from fire sources, high-temperature sources, and flammable and explosive materials to avoid danger caused by heat accumulation during charging.

(2) Discharge Management

• Avoid over-discharging. The voltage of a single cell must not be lower than 3.0V. If the voltage is too low, it may cause permanent damage to the battery and shorten the cycle life. During flight, real-time attention should be paid to the battery power, and sufficient power should be reserved to ensure the safe return of the UAV.

• Select a battery with an appropriate discharge rate according to the flight requirements of the UAV. Avoid using low-rate batteries in high-rate scenarios to prevent problems such as sudden voltage drop and severe heat generation of the battery due to overload, which may affect flight safety.

(3) Temperature Control

• The battery operating temperature should be controlled between 0℃ and 60℃. Avoid using the battery in extremely high-temperature (＞60℃) or low-temperature (＜0℃) environments. High temperatures will accelerate battery aging, reduce energy density, and even trigger thermal runaway; low temperatures will cause a decrease in battery capacity and poor discharge performance, affecting flight endurance and stability.

• Check the battery temperature before and after flight. If the battery generates abnormal heat during flight (e.g., the temperature exceeds 60℃), stop using it immediately. After cooling, check the battery status and confirm that it is not damaged before using it again.

(4) Transportation and Storage

• During transportation, use a dedicated battery packaging box or fireproof bag to prevent the battery from being squeezed or collided, which may cause damage to the casing or internal short circuit. At the same time, do not mix the battery with metal objects to avoid short circuits between the positive and negative electrodes.

• For long-term storage, keep the battery power at 30%-50% and place it in a cool, dry, and well-ventilated environment with the temperature controlled between 10℃ and 25℃. Avoid direct sunlight, humid or high-temperature environments to prevent rapid self-discharge of the battery, capacity attenuation, or safety hazards.

• Regularly check the status of stored batteries. Perform a charge-discharge cycle every 3-6 months to activate the battery activity and prevent permanent capacity loss of the battery due to long-term inactivity.

(5) Maintenance and Replacement

• Keep the battery clean during daily use. Regularly clean the dirt and debris on the battery surface to prevent impurities from entering the battery interface or affecting heat dissipation.

• Check whether the battery casing, connecting wires, and interfaces are damaged, worn, or loose. If problems such as casing cracks, liquid leakage, or broken connecting wires are found, stop using the battery immediately and replace it with a new one or use it after repair.

• When the number of battery cycles reaches the service life (usually the capacity decreases significantly after 300-500 cycles) or the capacity decays to below 70% of the initial capacity, the battery should be replaced in a timely manner to avoid affecting flight safety or causing UAV malfunctions due to insufficient battery performance.

7. Comparison with Other Battery Types (Taking Cylindrical Batteries as an Example)

Comparison Dimension	Pouch Batteries (Taking Lithium-Polymer Batteries as an Example)	Cylindrical Batteries
Space Adaptability	Adopting ultra-thin aluminum laminated films, they can be customized in shape, with high space utilization (increased by approximately 35%), and can fit the special designs of folded wings and micro UAVs.	With a fixed cylindrical structure, they require reserved fixed installation space, have low space utilization, are prone to space waste, and are difficult to adapt to UAVs of special shapes.
Mechanical Protection	The PA layer in the aluminum laminated board is combined with aramid fibers, resulting in strong puncture resistance; the flexible pressure release design can effectively prevent thermal runaway.	The metal casing has a robust structure and strong impact resistance, but it is prone to deformation under pressure, which may increase the risk of internal short circuits, and the gas is difficult to release quickly.
Thermal Management	The aluminum foil microchannel etching combined with a flexible thermal conductive film realizes 360° multi-directional heat dissipation, with high heat dissipation efficiency.	The winding structure leads to a long heat dissipation path, relying on external cooling systems, resulting in high thermal management costs. The performance is easily affected in high-temperature environments.
Safety Performance	The semi-solid electrolyte technology can eliminate flammable liquid electrolytes, the thermal runaway trigger temperature exceeds 300℃, and the explosion risk is reduced by more than 70% compared with cylindrical batteries.	The metal casing is prone to internal gas accumulation, the CID (Current Interrupt Device) has a delayed response, heat spreads quickly, and the explosion risk is relatively high under extreme conditions.
Energy Density	Adopting a ternary chemical stacking structure, the energy density can reach 320Wh/kg, which can extend the UAV flight time by more than 30%.	Limited by the winding structure, the energy density is usually lower than 300Wh/kg, making it difficult to meet the high energy demand of long-endurance UAVs.
Charge-Discharge Performance	Support 18C high-rate charge-discharge, can provide instantaneous high power to meet the rapid acceleration demand of UAVs; the cycle life exceeds 800 times.	The charge-discharge rate is usually limited to 1C-2C, and the maximum rate of high-rate models is about 30C. The winding electrodes are prone to deformation, the cycle life is about 600 times, and the performance degrades significantly with frequent use.
Weight and Portability	Without a thick casing, they are lightweight, suitable for UAVs with high lightweight requirements, and can improve flight endurance and maneuverability.	The metal casing increases the weight. Under the same energy, they are 20%-40% heavier than pouch batteries, increasing the UAV load and affecting flight performance.
Cost and Manufacturing	The manufacturing process is complex, requiring special materials and technologies, resulting in high costs.	The design is suitable for mass production, with low manufacturing costs, and the price is 10%-20% lower than that of pouch batteries.
Application Scenario Adaptation	Suitable for UAVs with high maneuverability, high burst power, and lightweight requirements, such as consumer-grade aerial photography UAVs, racing UAVs, and professional industrial-grade UAVs.	Suitable for scenarios with long endurance, low cost, and low-rate requirements, such as surveying and mapping UAVs, low-end aerial models, and backup power supplies.