Problems with the Dreamliner battery

"......There are serious and unresolved physics problems here - perhaps even fundamental physics barriers that cannot be overcome and extend across the gamut of Li-Ion (this is my personal belief - what do you think?).......

Japan’s two biggest airlines replaced lithium-ion batteries on their Boeing Co 787 Dreamliners in the months before separate incidents led to the technologically advanced aircraft being grounded worldwide due to battery problems.

Comments from both All Nippon Airways, the new Boeing jetliner’s biggest customer to date, and Japan Airlines Co Ltd point to reliability issues with the batteries long before a battery caught fire on a JAL 787 at Boston’s airport and a second battery was badly charred and melted on an ANA domestic flight that was forced into an emergency landing.

ANA said it changed 10 batteries on its 787s last year, but did not inform accident investigators in the United States because the incidents, including five batteries that had unusually low charges, did not compromise the plane’s safety, spokesman Ryosei Nomura said on Wednesday.

JAL also replaced batteries on the 787 “on a few occasions”, said spokeswoman Sze Hunn Yap, declining to be more specific on when units were replaced or whether these were reported to authorities.

ANA did, however, inform Boeing of the faults that began in May, and returned the batteries to their manufacturer, GS Yuasa Corp. .....

Probably one would have to play golf or go fishing with pilots and airplane mechanics to get the real story.

Wow, that is really bad news for Boeing if they can't completely nail this problem down to a fixable root cause. I sure hope Boeing has a 'Plan B' that won't take a year of downtime to qualify a new electrical sub-system.

The initial redesign includes a fireproof battery box, made of titanium or steel, several sources said. That will seal the cells, keeping moisture out and flames in.

It also includes a venting system that will directly evacuate to the outside any vapor and liquid flowing from the battery.

In the two recent battery overheating incidents, flammable liquid and vapor sprayed out of the battery and across the electronics bay where the battery sits, before reaching an outflow valve.

Longer term, the battery box will be enlarged to provide more separation between the battery’s eight cells, several sources said.

That will help ensure that overheating of one cell doesn’t spread to others — a so-called “thermal runaway” that occurred in both recent incidents.

The battery control system will have sensors to monitor the temperature and voltage of each individual cell rather than the battery as a whole, one source said.

And the same source said engineers are also working on using an inert gas such as halon or nitrogen to expel the oxygen generated when a battery overheats.

.... and any cowboy will tell you : "Always drink upstream of the herd".

old jim

Boeing has short and medium term plans.

http://seattletimes.com/html/busines...yndication=rss
"....The battery control system will have sensors to monitor the temperature and voltage of each individual cell rather than the battery as a whole,...."

The FAA is on the hot seat. Five years ago, they accepted Boeing’s arguments and granted permission to use lithium-ion batteries on the Dreamliner, “if potential fire is contained and fumes vented”. They now have a dilemma – hurting an important domestic industry by doing their job, or becoming discredited if another problem occurs.

After offering to help Boeing with its lithium-ion battery problems, Elon Musk is somewhat raising the stakes. Musk, who heads both Tesla Motors and space exploration company SpaceX, has now called the batteries in the Boeing 787 "inherently unsafe" in an e-mail to trade publication Flightglobal.

For example, with seven thousand 18650 cells the surface area is roughly 27 square meters. If there were an imaginary set of 20 much larger cube-shaped cells that enclosed the same volume, the surface area would be only 3.5 square meters, more than seven times smaller. Surface area is essential to cooling batteries since the surface is where heat is removed; more is better. Also, because of their small size, each cell is able to quickly redistribute heat within and shed heat to the ambient environment making it essentially isothermal. This cooling architecture avoids “hot spots” which can lead to failures in large battery modules.