Tonight during a live webcast from Japan, which you can watch a replay of here, we unveiled the specifics of our permanent solution to the 787 battery issue. That solution is the result of a detailed and rigorous process involving people from around the globe who put in thousands of hours of work—and we’re very confident this solution is the right one.
The three layers of protection we’ve developed address the factors identified by the Boeing technical team as possible causes of battery failure. The findings were also verified by an independent group of lithium-ion battery experts from a number of industries, universities and national laboratories. Let’s walk through each of them.
Enhanced Production Controls and Operating Processes
The first layer of improvements is taking place during the manufacture of the batteries in Japan. Boeing teamed with Thales, the provider of the integrated power conversion system, and battery maker GS Yuasa to develop and institute enhanced production standards and tests to further reduce any possibility for variation in the production of the individual cells— as well as the overall battery.
Enhanced production standards are built into the new battery design.
Four new or revised tests have been added to screen cell production, which now includes 10 distinct tests. Each cell will go through more rigorous testing in the month following its manufacture including a 14-day test during which readings of discharge rates are being taken every hour. This new procedure started in early February and the first cells through the process are already complete. There are more than a dozen production acceptance tests that must be completed for each battery.
We’ve also decided to narrow the acceptable level of charge for the battery, both by lowering the highest charge allowed and raising the lower level allowed for discharge. Two pieces of equipment in the battery system - the battery monitoring unit and the charger— are being redesigned to the narrower definition. The battery charger will also be adapted to soften the charging cycle to put less stress on the battery during charging.
Improved Battery Design Features
Changes inside the battery will help reduce the chances of a battery fault developing and help to further isolate any fault that does occur so that it won’t cause issues with other parts of the battery.
To better insulate each of the cells in the battery from one another and from the battery box, two kinds of insulation will be added. An electrical insulator is being wrapped around each battery cell to electrically isolate cells from each other and from the battery case, even in the event of a failure. Electrical and thermal insulation installed above, below and between the cells will help keep the heat of the cells from impacting each other.
Wire sleeving and the wiring inside the battery will be upgraded to be more resistant to heat and chafing and new fasteners will attach the metallic bars that connect the eight cells of the battery. These fasteners include a locking mechanism.
Finally, a set of changes is being made to the battery case that contains the battery cells and the battery management unit. Small holes at the bottom will allow moisture to drain away from the battery and larger holes on the sides will allow a failed battery to vent with less impact to other parts of the battery.
New Battery Enclosure
The battery case will sit in a new enclosure made of stainless steel. This enclosure will isolate the battery from the rest of the equipment in the electronic equipment bays. It also will ensure there can be no fire inside the enclosure, thus adding another layer of protection to the battery system. The enclosure features a direct vent to carry battery vapors outside the airplane.
New titanium fixtures are being installed in the electronics equipment bays to ensure the housing is properly supported.
The battery will now sit inside a new enclosure made out of stainless steel. A stainless steel panel is seen on the right.
With the FAA’s permission, we’ve already started testing to gain FAA approval of the battery enhancements. During engineering testing, which occurs prior to certification testing, the team demonstrated that the new housing could safely contain a battery failure that included the failure of all eight cells within the battery. The “ultimate” load is the equivalent of 1.5 times the maximum force ever expected to be encountered during a battery failure. The housing easily withstood this pressure and did not fail until the pressure was more than three times the ultimate load.
Through another test, the team demonstrated that fire cannot occur within the new enclosure. Its design eliminates oxygen, making the containment unit self-inerting. Inerting is a step above fire detection and extinguishing as it prevents a fire from ever occurring. The design also vents all vapors by venting directly outside of the airplane rather than into the equipment bay.
As we’ve said before, we’ll use two 787s for ground and in flight testing of this solution. We’re also simultaneously moving out on an effort to resume deliveries.
During the webcast, Boeing Commercial Airplanes president and CEO Ray Conner said he spoke for all 170,000 Boeing employees when he said our number one priority is the safety of everyone who flies on our airplanes. I couldn’t agree more—and look forward to being one of the first people back on board the 787 when it takes to the skies again.