SB002 Super Light Battery – SL8 Battery Incident – 14 Nov 2022 Follow-Up
Date Released: November 14th, 2022
Subject: SL8 Battery Incident
Required Action: None at this time – Alert
This is a follow-up to our 8 Nov Service Bulletin regarding an SL8 battery fire at our East Coast office. We have not yet determined the root cause, but our focus is narrowing. Below we describe some of our testing to date.
As of now, there are no required actions and customers are advised to continue normal SL4 / SL8 / Astro operations with extra attention paid to any battery faults.
In the previous service bulletin, we mentioned four areas of investigation: overvoltage leading to critical component failure, cell balance circuit failure, manufacturing defect in the PBCA, and random component failure. Here’s where are at on each possible failure mechanism:
- Overvoltage incident
- In bench testing, it’s possible to create similar damage to what we experienced by forcing significant overvoltage conditions. However, we have not yet been able to produce these overvoltage conditions in a practical setting. We continue to investigate here.
- We have modified a few SL8 batteries to give them high speed voltage logging capability and we are using these along with bench testing to find any conditions resulting in an overvoltage.
- Cell balance circuit failure or balance wire short circuit
- In our testing it has been extremely difficult to intentionally create a short in the balancing circuit which would cause a fire.
- Manufacturing error or defect in a PCBA
- We are reviewing specific processes with the PCBA manufacturer.
- Random and catastrophic failure of key component (TVS Diode, Regulator, etc)
- We have found no evidence of counterfeit parts or defective batches of parts.
In addition to our testing, we have completed an internal and external engineering review of the BMS circuit design and the teams found no errors or design flaws to explain the incident. We also reviewed manufacturing records and related flight logs, but found nothing out of the ordinary.
At this time, there is no immediate action required from our customers. If you have any abnormal battery behavior during use, charging, or storage, please contact Freefly Support.
Next Steps: Freefly will provide an update to this Service Bulletin by 11/21. We will follow up with all SL8 / SL4 / Astro customers on our investigation findings and all required customer actions that come from our investigation.
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