Note: The rationale for this post will be reviewed . The "unprecedented" is not what was imagined. Post will suffer revision, corrections or even deleted.
Hi,
TURIN:
This is unprecedented. Boeing innovated designing the first airliner using Li Ion batteries (as the main battery) AND ALSO:
Using a battery that only delivers (higher) current when there is a (very rare) failure in the DC bus.
This means:
The ANA battery (certainly older than JAL APU unit) probably NEVER* WAS USED. I.e. never delivered (high) current. Just was kept "floating" since was manufactured.
This is a radically different use of a typical battery. At least we can say this could introduce new (and unknown) possibilities. It is a truly backup unit. Not being "exercised" like (as i imagine) in practically 100% of vehicles (land, water and air, main batteries)
AFAIK the designers made the same in A380 (emergency lighting).
The failure mode of the ANA battery (or the reason for the failure) now becomes clear to me could be another completely different. Even with the same charger could be another reason. I am assuming BOS JAL 787 started the APU using the battery. And ANA 787 had no DC bus failure requiring main battery use before the incident.
The timing between both cases (intriguing) could be just a coincidence.
APU battery operates differently than main battery that just waits (charged) an emergency (in the DC bus)
I am assuming something (that will be verified) from what i learned so far on 787. (Use of Diode, APU opp. etc.) Unfortunately we donīt have yet all information (schematic diagrams, etc.) to understand completely the issue.
(*) Unless there is a discharger (between the battery and the diode unit) to cycle it (cycles of charging and discharging, during normal operation) Something not feasible for deeper discharge. (you may need it when it was recovering from the "exercise")
Note: The rationale for this post will be reviewed . The "unprecedented" is not what was imagined. Post will suffer revision, corrections or even deleted.