Understanding and Maintaining Lithium Polymer Batteries for Drones: A Comprehensive Guide

Lithium polymer batteries serve as the power source for drones, providing the energy required for flight. Understanding these batteries and adopting correct usage methods while ensuring proper maintenance can enhance flight safety and prolong battery life. Below, we provide a detailed explanation of battery usage and management.

Meaning of High-Rate Lithium Polymer Batteries

The batteries used in drones are known as high-rate lithium polymer batteries, belonging to the category of lithium batteries. They are widely used in the drone industry due to their high energy density, uniform high output voltage, high power output, and rapid charging capabilities.

Key Nominal Indicators

• Nominal Voltage: The nominal voltage of a lithium polymer battery cell is 3.7V.

• Voltage After Charging: After fully charging, the voltage of a lithium polymer battery cell ranges from 4.2V to 4.25V.

• Nominal Capacity: Measured in mAh, it indicates the battery's storage capacity.

• Continuous Discharge Rating (C-Rating): Indicates the maximum continuous discharge current of the battery. For agricultural drones, batteries with a continuous discharge rating of 15C are commonly used.

• Burst Discharge Rating: Indicates the maximum instantaneous (within 10 seconds) discharge current of the battery, typically twice the continuous discharge rating.

Common Lithium Polymer Batteries for Multirotor Aircraft

• 6S 10000mAh Battery: Used in large multirotor aircraft such as the S1000 and S800 EVO.

• 3S 5000mAh Battery: Commonly used in medium-sized multirotor aircraft like the Flame Wheel F550.

• 3S 2200mAh Battery: Utilized in small multirotor aircraft such as the Phantom 1 and Flame Wheel F450.

• 3S 5200mAh Battery: Suitable for quadcopters like the Phantom 2, Vision, and Vision+.

Explanation of Lithium Polymer Battery Parameters

• C-Rating: Represents the battery's ability to discharge. It is calculated by multiplying the C-rating by the capacity, providing the maximum discharge current of the battery.

• S-Number: Indicates the number of cells connected in series, influencing the battery's voltage.

• P-Number: Indicates the number of cells connected in parallel, affecting the battery's current capacity.

Battery Parameters Example

An example battery specification is: 16000mAh 15C 6S 22.2V, which translates to a capacity of 16,000mAh, a discharge rating of 15C, 6 cells connected in series, and a nominal voltage of 22.2V.

Precautions for Battery Use and Maintenance

1. Avoid Dissection by Non-Professionals: Disassembling battery cells by non-professionals may lead to internal short circuits, swelling, ignition, and other hazards.

2. Handle Leakage Safely: Though lithium polymer batteries theoretically do not have flowing electrolytes, in case of leakage, wash the affected area with water immediately and seek medical attention.

3. No Burning Allowed: Never burn or expose batteries to fire, as it poses a significant risk of ignition and should be strictly prohibited.

4. Avoid Immersion in Liquids: Keep batteries away from liquids such as freshwater, seawater, and beverages to prevent damage.

5. Handle with Care: Prevent dropping or impacting batteries to avoid accidents.

Charging Precautions

• Charge batteries within a temperature range of 0°C to +45°C.

• The charging current should not exceed the maximum specified current, usually not more than 2C.

• Do not charge batteries exhibiting swelling, deformation, leakage, or voltage below 2.6V.

• The charging upper limit voltage should not exceed 4.22V, and the temperature after charging should not exceed 45°C.

Discharge Precautions

• Discharge batteries within a temperature range of -20°C to +60°C.

• The discharge current should not exceed the maximum specified current.

• Do not discharge batteries exhibiting swelling, deformation, leakage, or a voltage difference ≥100mV.

• The discharge lower limit voltage should not be lower than 2.6V, and the surface temperature should not exceed 80°C after high-current discharge.

Charge-Discharge Precautions

• Maintain battery voltages within the normal range of 2.8V to 4.20V during charge and discharge operations.

• Periodically check the voltage of each cell before charging and discharging.

• Long-term storage of batteries should be within a temperature range of -10°C to 45°C.

• Charge the batteries to a voltage of 3.6V to 3.9V or ideally 3.85V before prolonged storage to prevent irreversible capacity loss.

Fire Extinguishing Methods for Lithium Polymer Battery Fires

• Turn off the charging power switch and use asbestos gloves and blankets to handle and cover the burning battery.

• Use fire sand to cover the asbestos blanket to smother the flames.

Battery Fire Extinguishing Precautions

• Use dry powder extinguishers for lithium battery fires, but be aware that it may corrode equipment and contaminate the area.

• Carbon dioxide extinguishers may suppress flames momentarily but will not stop the fire entirely.

• Other types of extinguishers are ineffective against lithium battery fires.

Conclusion

Understanding the parameters and proper handling of lithium polymer batteries is essential for drone operators to ensure safety and maximize battery performance. Adhering to precautions during use, charging, and storage can prevent accidents and prolong the lifespan of batteries, contributing to safer and more efficient drone operations.