TB50 & TB55 User Guidance
Background
DJI released a firmware update on 16 November 2018 following reports of a small number of TB50 and TB55 batteries that showed incorrect power levels which led to loss of power mid-flight. The firmware update addresses a rare issue involving the battery state of charge (SOC) calculation algorithm by incorporating the following conservative measures which serve to enhance the battery management system and optimize power supply during flight. These are interim measures until the release of a further firmware update in December 2018.
For TB55 batteries used with the M200 series drone, the firmware update imposes these new battery safeguards:
- Battery temperature detection before take-off (S1)
The battery temperature must be 15°C (59°F) or higher before the aircraft can take off. This is because a battery with low temperature has a higher internal resistance, which causes lower voltage than in warmer conditions. A battery with low voltage will provide a lower level of power to the drone, and hence impose higher risk of a power loss.
- SOC (state of charge) detection before take-off (S2)
The voltage of the battery will be used to verify the SOC value by the DJI algorithm in the new firmware. This SOC value will be compared to the one calculated by the battery SOC calculation algorithm to determine if there is a “false high” SOC reading. If there is a “false high” SOC reading, then the aircraft will not be able to take off.
- Return-to-Home (RTH) or Automatic Landing (AL) (S3)
When the DJI algorithm detects a difference in SOC levels (this calculation runs within the battery and is therefore not visible to users through the screen) between the algorithm and the actual level that is greater than 5%, RTH (return-to-home) will be activated at a detected battery level of 30% and automatic landing (AL) activated at 10% (based on the DJI algorithm). If the difference is less than 5% then no action will be activated.
For TB50 batteries used with the M200 series drone, the firmware update imposes this new battery safeguard:
- Battery temperature detection before take-off (S1)
The battery temperature must be 15°C (59°F) or higher before the aircraft can take off. This is because a battery with low temperature has a higher internal resistance, which causes lower voltage than in warmer conditions. A battery with low voltage will provide a lower level of power to the drone, and hence impose higher risk of a power loss.
Safety is DJI’s top priority which is why we implemented these conservative safeguards as a quick countermeasure to help prevent any further potential of M200 series drones experiencing loss of power mid-flight, while we continue our thorough investigation of the root cause of the issue and take further steps in the near future to remediate the issue.
These conservative measures, however, mean that some pilots may experience early and unexpected RTH or AL of their M200 series drone during operations as the batteries have been programmed to respond take an overabundance of caution when it detects even a small chance of battery failure or insufficient power to RTH/AL. During this interim period, we advise customers to plan their flights accordingly, allowing for the potential of an early RTH or AL function to be initiated. DJI has prepared the following guideline to help minimize potential disruption to our users’ operations as we work around-the-clock to release a new firmware update in December which will further address these issues and improve overall user experience.
Guideline
Latest firmware. M200 series drone users are strongly advised to update their drone and batteries to the latest firmware. From 23 November 2018, this safety-related update is mandatory for pilots using DJI GO 4 to operate their M200 series drone as they will experience a flight lock until the update is complete. This is why we ask that pilots allow extra time before their next flight to perform this update to minimize disruption to their operations.
Inconsistent Firmware Notification. For the time being, pilots who are using drones of both the DJI M200 series and the DJI Inspire 2 may receive an "inconsistent firmware" notification when using batteries updated with different firmware versions. This may lock the flight of the drone. DJI advises that pilots use batteries upgraded with the same firmware until the new firmware update is released in December. This update will solve this compatibility issue in addition to improving overall user experience.
Battery is taking a longer time to heat up. This is caused by S1. DJI suggests pilots pre-heat their batteries or keep them at room temperature (about 23°C/73.4°F) before flying outdoors to minimize risk of flight disruption.
Drone is returning home (return-to-home or RTH) or auto-landing (AL) earlier. Pilots may see their drone start RTH or AL when the battery SOC is still more than 30%. This is caused by S3 which intentionally implements a conservative algorithm in the flight controller to ensure the drone has sufficient battery capacity to sustain flight as it returns-to-home or auto-lands. If you are constantly experiencing earlier RTH or AL (where battery SOC registers more than 30% on the screen), follow the guidance of pre-heating batteries prior to flight. If it still occurs, please send your flight logs to DJI customer service at dji.com/support so our team can investigate and provide a recommended solution.
Guidance for pilots experiencing automated RTH or AL:
- When a drone starts Smart RTH, pilots can interrupt and stop RTH by pressing the “X” on the screen
- When a drone begins AL, pilots can still steer the drone using the joystick to help find the safest landing location. Pushing up the throttle can also slow or counteract the descending aircraft.
It is important to note that these responses are not caused by any hardware fault. Early RTH or AL is due to the risk mitigation strategy programmed into our flight controller.
While DJI, just like any other manufacturer, can never guarantee absolute safety in every case, we take safety very seriously and therefore are addressing this situation with an abundance of caution, while we work on a longer-term resolution to be released in December.
We sincerely apologize for inconvenience caused by these conservative measures and ask for our users’ continued understanding and patience as we work around the clock to release the next firmware update, which will address these non-critical but significant performance issues.
If you believe you may have experienced a related power problem involving the TB50 or TB55 battery, please contact DJI customer service at
https://www.dji.com/support to report the issue.