Comprehensive Analysis of Drone Battery State of Health (SOH)

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.

The State of Health (SOH) of a drone battery is a core indicator for evaluating the degree of attenuation of the battery’s current performance compared to its brand-new state. It plays a decisive role in the drone’s endurance, flight safety, and battery service life. Accurately grasping the SOH can effectively prevent unexpected power outages during drone flights and provide a key basis for battery management, making it an indispensable parameter in the use and maintenance of drones.

1. Core Definition and Nature of SOH

Essentially, SOH is the percentage ratio of the battery’s current key performance to that of its factory-new state. These key performance metrics mainly include available capacity, charge-discharge efficiency, cycle life, etc.

The SOH of a brand-new battery is usually 100%, indicating that the battery performance fully meets the factory standards and can fully meet the drone’s flight requirements.

With the use of the battery, under the influence of factors such as cyclic charging and discharging, improper storage, and environmental impacts, irreversible attenuation occurs inside the battery, such as aging of electrode materials, loss of electrolyte, and increase in internal resistance, and the SOH also decreases gradually.

When the SOH drops to the industry-recognized threshold of 60%-80%, the battery performance will decline significantly, which is specifically manifested in a reduction in endurance by more than 30% and a decrease in discharge rate. Continuing to use the battery at this time may face risks such as bulging, liquid leakage, or even fire. It is recommended that the battery no longer be used as the main flight battery.

2. SOH Classification and Handling Recommendations

According to different SOH ranges, the state of drone batteries can be divided into different levels, and corresponding handling measures can be taken, as shown in the following table:

SOH Range	Status Description	Recommended Handling Methods
≥80%	Healthy	Can continue to be used for high-load tasks, such as long-duration flights and heavy cargo transportation
60%-80%	Mild Attenuation	Switch to low-power tasks, such as short-distance inspections and low-altitude flights, or conduct echelon utilization by applying it to scenarios with lower requirements for battery performance
<60%	Severe Attenuation	Stop using, and enter the recycling or disassembly process to avoid safety accidents caused by insufficient battery performance and realize the rational recycling and utilization of resources

For example, large logistics enterprises have effectively reduced the battery failure rate by 67% through this hierarchical management method, while significantly reducing operating costs and improving economic benefits.

3. Key Factors Affecting SOH

Drone batteries are mainly lithium-polymer batteries (LiPo), and a few are lithium iron phosphate batteries (LiFePO4). The SOH attenuation of these batteries is mainly driven by the following types of factors:

(1) Number of Charge-Discharge Cycles

Each completion of a “full charge + full discharge” cycle will cause slight loss of battery electrode materials, reduce the ion migration efficiency of the electrolyte, and gradually decrease the available capacity. For example, after frequent flights, the battery is fully charged, and after 100 cycles, the battery SOH may drop to about 90%.

(2) Charge-Discharge Methods

• Overcharging: When the charging voltage exceeds the rated voltage of the battery (e.g., a single LiPo battery exceeds 4.2V), it will cause lithium precipitation on the electrode and decomposition of the electrolyte, resulting in permanent damage to the battery. This situation is common when the charger malfunctions.

• Over-Discharging: When the battery discharge voltage is lower than the protection voltage (e.g., a single LiPo battery is lower than 3.0V), it will cause the collapse of the electrode structure and irreversible capacity loss. This mostly occurs in scenarios where the drone is forced to land due to exhausted power during flight.

(3) Storage Environment

• Temperature: High temperatures will accelerate the volatilization of the electrolyte and the aging of the electrode, causing damage to the battery. Although low temperatures do not have a significant impact on the battery in the short term, long-term storage in a low-temperature environment may lead to the precipitation of lithium dendrites, affecting battery performance. For instance, leaving the battery in an exposed drone backpack for a long time in summer will cause significant damage to the battery.

• State of Charge: When stored at full charge (100% SOH), the active substances inside the battery react actively, which easily accelerates battery attenuation. When stored at a depleted state (SOH < 20%), the battery is prone to “sulfation”. For example, storing a battery at full charge when it is idle for a long time will significantly shorten the battery life.

(4) Operating Environment

• High-Rate Discharging: In aggressive flight scenarios, such as rapid acceleration, vertical ascent, or long-term flight in “sport mode”, the instantaneous discharge current of the battery will exceed the rated value, leading to a sharp increase in internal resistance, intensified heat generation, and accelerated battery attenuation.

• Physical Damage: If the battery is impacted after a drone crash, or collided and squeezed during use or storage, the battery shell may be broken, and the internal cells may be short-circuited, directly damaging the battery structure and seriously affecting the SOH.

4. Methods for Detecting and Checking SOH

Ordinary users do not need professional equipment and can obtain the SOH of the drone battery through the following three common methods. Professional users can obtain more accurate data with the help of special tools:

(1) Official Drone APP (Most Direct)

Mainstream drone brands, such as DJI, Jifei, and Ehang, display the battery SOH in their supporting APPs. The specific operation steps are as follows:

• Turn on the drone and the remote controller, and connect the mobile phone to the APP.

• Enter the “Battery” or “Device Status” interface, where “Battery Health” or “SOH” is usually directly marked. For example, in the DJI Fly APP, it can be viewed in the “Battery Settings”.

• Some APPs also display auxiliary information such as “number of cycles” and “current capacity”. Users can combine this information with SOH to more comprehensively judge the battery state.

(2) Battery Management System (BMS) Feedback

Drone batteries have a built-in Battery Management System (BMS), which monitors the cell voltage, temperature, and number of cycles in real time and calculates the SOH. When the BMS detects an abnormality in the battery, it will prompt the user in the following ways:

• Battery Indicator Lights: Taking the intelligent flight battery as an example, if a certain cell fails, the corresponding indicator light will flash (e.g., a steady red light or alternating red and green lights). At this time, the battery SOH is usually below the safety threshold.

• APP Alerts: The APP will pop up prompts such as “Low Battery Health” and “Battery Replacement Recommended”. Users must stop using the battery immediately.

(3) Third-Party Tools (For Professional Users)

For professional users who need more accurate SOH data, such as maintenance personnel, the following tools can be used:

• Specialized Battery Testers: For example, some models of LiPo battery balance chargers support reading the battery SOH and the number of cycles.

• Official Brand Maintenance Tools: For instance, the special equipment at DJI maintenance stations can read the detailed internal attenuation data of the battery, providing an accurate basis for battery maintenance and evaluation.

5. Prevention and Mitigation Strategies for SOH Attenuation

To extend the SOH life of the battery, the key lies in avoiding damaging use and optimizing storage and charging habits. The specific principles can be followed as below:

(1) Charging: Avoid Overcharging and Control the Rate

• Only use official original chargers, and avoid using third-party fast chargers unless the fast charger is certified by the brand, to prevent damage to the battery caused by uncontrolled charging voltage and current.

• Charge the battery to 90%-95% instead of fully charging it, unless a long-distance flight is required. This can reduce the chemical pressure inside the battery in the fully charged state and slow down battery attenuation.

• Disconnect the power in time after the battery is fully charged, and avoid long-term “trickle charging” with the power plugged in. Generally, the trickle charging time should not exceed 2 hours.

(2) Discharging: Avoid Over-Discharging and Control the Rate

• Strictly monitor the battery power during flight. The drone must return when the remaining power is 20%-30%. Do not wait until the “low-power alarm” is triggered to start returning, and leave sufficient emergency time for unexpected situations.

• Reduce aggressive flight behaviors and avoid long-term high-rate discharging. For example, the continuous flight time in “sport mode” should not exceed 5 minutes.

• If the battery shows “bulging” or “unable to charge” due to over-discharging, it should be scrapped directly and not be repaired, to avoid safety accidents.

(3) Storage: Control the State of Charge and Environment

• When the battery is idle for a long time (more than 1 week), charge it to 40%-60% of the capacity. This is the “storage mode” recommended by the battery management system. Some chargers support one-click activation of this mode. At this time, the internal reaction of the battery is the most stable, which can effectively reduce power loss and performance attenuation.

• The storage environment temperature should be controlled between 10℃ and 25℃, avoiding high temperatures (>35℃), low temperatures (<0℃), and humid environments. At the same time, keep away from fire sources and metal objects to prevent the battery from being damaged by the external environment.

• Store the battery separately to avoid squeezing with other hard objects. If the battery shell is found to be damaged, stop using it immediately.

(4) Usage: Handle with Care and Conduct Timely Maintenance

• Before the flight, carefully check the appearance of the battery. If bulging, liquid leakage, or shell cracking is found, replace the battery directly and do not continue to use it.

• After the flight, wait for the battery to cool down to room temperature before charging. Charging the battery immediately when it is still at a high temperature after landing will accelerate battery aging.

• Calibrate the battery regularly. For example, every 20-30 cycles of the battery, a “full charge + slow discharge” calibration can be performed to enable the battery management system to calculate the SOH more accurately and improve the accuracy of battery state monitoring.

6. Key Notes

• Irreversibility of SOH: Battery attenuation is a physical and chemical process. Once the SOH decreases, it cannot be restored to 100% through “repair”. Only scientific maintenance methods can slow down the attenuation rate and extend the battery service life.

• Cycle Count ≠ the Only Criterion for SOH: Under the same number of cycles, the SOH may vary greatly if the battery usage habits are different. For example, the SOH of a battery that has undergone 100 “gentle charge-discharge” cycles may be higher than that of a battery that has undergone 50 “overcharge and over-discharge” cycles.

• Safety First: When the battery SOH is lower than 60%, or when problems such as bulging, liquid leakage, and abnormal charge-discharge occur, the battery must not be used continuously. It should be disposed of in accordance with the “hazardous waste” disposal standards and must not be discarded randomly, so as to avoid fire risks and ensure environmental and personal safety.