FPOBN,
The Special Regulations were composed in 2007, and approved the same year (October).
The Fire Research report, in addressing the "large format" Li technology, stated unequivocally that there were no Industry standards in place as of JULY,2011.....
Large Format seems to mean 10-100 aH. So FAA left Boeing to come up with a PROVEN system. I do not fault FAA for that. To the contrary, advancing technology requires room to advance. The special regs set limits, not specs on how to ennable the technology short of them (pardon the pun). The limits turn out to be sufficiently rigorous, NO FIRE, NO UNCONTAINED ELECTROLYTE. (One in a Billion, one in ten million)
The Airworthiness Directive is couched in similar terms and provoked a snarky rejoinder from the airframer. "Show us how to conform"....
It is up to the builder to perform, there is no room for wriggling.
Large Format seems to be simply, "scaled up". Not an engineer, but that seems like an invitation to Fail. "Nice Battery, can you make it bigger?"
Primarily as to heat control. Now Boeing can "scale back", until they can demonstrate some acceptable thermal performance, but that will take time, and it means satisfying a regulator who has been taken to the cleaners once already.
It also means packaging more and smaller batteries into an existing architecture.
The Big Box format might be fine to alleviate fire control issues, but it does not address the prevention of fire in the first place, something that was touted to be on the order of "One in a BILLION" (John Goglia). It does nothing to salvage the trashed reliability profile as to "Back Up Battery".
Have you seen the photos of the "Exemplar" battery removed from JAL 08?
The "Jelly Roll" looks to have sat in the lunch box for quite awhile, and may have seen Sally and Joey sit on it several times.
The electrode stacks are sensitive to shape retention, as to remaining safe from internal damage, and evenly distributed excess heat. (Sic).
Last edited by Lyman; 10th Mar 2013 at 17:22.