Hi,
RetiredBA/BY: Ref:18:13
...so is there any way the crew could be advised of a developing internal battery problem such as a defective cell, say through the EICAS, and could a defective cell be automatically isolated from the rest of the battery ?
1) Unfortunately these cells has not "graceful degradation" nor "fault tolerance" a good characteristic of Lead acid and to some extent, Ni Cd. So a message is just to inform the crew battery is INOP. I imagined along this days in a solution using a MAIN battery and a AUX battery. Will comment on advantages later. The AUX could be one to preserve the MAIN.
2) The problem to isolate a defective cell is: You need a costly relay and you reduce the voltage of the battery. Itīs not practical.
...someone queried whether the main battery could/should be used to start the APU on the 787. Isn't that one of its main functions ?
Weight (cost and other) considerations led designers to have two independent. Certainly a good approach. But posing inherent operational limitations in a degraded scenario.
I seem to remember frequently staring the APU on the ground on the 75 and 76 and in the event of double flameout and loss of both gens. in flight starting the APU from the battery would be a very high priority ! One might think that a main battery or separate APU batt should be able to do two or three APU starts with ease.
787 designers relied on this battery to provide adequate safety. Problem is the "ideal" battery failed. The a/c design was adequate. (IMO good)
P. S. I may have missed it but no one seems to have mentioned the electrical fire and emergency landing on a 787 during test work. Anyone know the cause of that fire?
The official cause was not a battery related issue. Iīve heard of a distribution panel destroyed by a tool left by a mechanic.
The event was serious.
Will comment later on RC issue.