Originally Posted by Tweaker
The battery box that burned for 40+ minutes. After reading the hysteria around here from our experts, I have to say i am thoroughly disappointed. I expected more. Sorry about the size.
thanks for posting pic... re-sized below
apart from a breach of the structure of aircraft itself, isn't a fire on aircraft in the air among most serious emergency there is?
hysteria huh ... if a total system failure for a battery backup to the main APU doesn't scare you... then what does?
notice the burnt bundle of wires going into battery pack. which of course goes into all sorts of electronics. I'd be very concerned at what electronics taken out by fire. on an aircraft this advance ... a loss of electronics on such a heavily computer controlled aircraft would be bad news indeed.
peek at this high level schematic below. reason for so many electrical subsystems is the no bleed concept used in 787. IE electrically driven hydraulic pumps are extensively used.
burnt lithium cobalt picture reveals there are 8x 65amp hour GS Yusa prismatic cells. highly unlikely it would burn for 40 minutes by itself. 8x 3.7v nominal = 29.6v ... actual voltage range from 28v to 33.6v full charged. possible sustained output for large packs like this would be 28C+ range or 1,800+ amps at 29-33v
lithium cobalt cells will accept a charge for long as one is delivered. until thermal runaway occurs at about 4.4v range. a circuit board failure that controls charging for these massive lithium cobalt cells could easily result in burnt battery below.
Lithium cobalt battery pack fire progression typical ... one or two cells goes unstable into thermal runaway... then explodes with a ball of fire. burning cell will burn with explosive force. a few minutes later ... heating nearby cells to critical temp, igniting it... chain reaction continues until all cells are consumed.