Boeing Releases More Details on Dreamliner Battery Fix

By Paul Riegler on 15 March 2013
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ANA's Dreamliner in Seattle for its launch flight

ANA’s Dreamliner in Seattle for its launch flight

Boeing released additional details about its plans to revise the design of the trouble-prone lithium-ion batteries that caused two fires that resulted in the worldwide grounding of the Dreamliner fleet.

The changes and improvements will add several layers of safety and could be ready to be deployed to the fleet, pending FAA approval, in a matter of weeks.

Boeing has already designed new stainless steel enclosures for the batteries. The new cases will isolate the battery from other equipment in the electronic equipment bays.  It is being designed to make it impossible for a fire to occur inside the enclosure and has a new direct vent to carry vapors outside the aircraft.  In addition, Boeing is using new titanium fixtures to support the housing in the equipment bay.

The battery itself has been redesigned to reduce the likelihood of a battery fault developing.  Should a fault develop despite the changes, the new design will isolate it so that it does not cause any additional issues with other parts of the battery.  In addition, two kinds of insulation are being added.  An electrical insulator is being wrapped around each battery cell to isolate the cells from each other and the battery case.  Electrical and thermal insulation is being installed above, below, and between the cells to keep the heat from one cell from impacting another.  New wiring sleeving and the wiring inside the battery has been redesigned to be more resistant to heat and chafing and new fasteners are being used to attach the metallic bars that connect the eight cells of the battery, including a new locking mechanism.

The battery’s case now has small drainage holes on the bottom to allow moisture to drain away from the battery as well as larger holes on the side that would allow a failed battery to vent with less impact to other parts of the battery.

Boeing will use four new or revised tests to screen battery cell production, which currently goes through ten distinct tests.  Each cell will go through one month of testing including a 14-day test during which readings of discharge rates are taken every hour.  This new procedure started at the beginning of February and Boeing has already completed the testing of multiple cells.

Boeing and its partners Thales and GS Yuasa have also narrowed the battery’s acceptable level of charge, both by lowering the highest charge allowed and raising the lower level allowed for discharge.  The battery monitoring unit and charger were both redesigned to support the new threshholds.  The charger has also been redesigned to soften the charging cycle, ensuring that it puts less stress on the battery during charging.

Boeing is looking forward to completing its testing of the new batteries and components so that airlines around the world can resume flying the Dreamliner.  “As soon as our testing is complete and we obtain regulatory approvals, we will be positioned to help our customers implement these changes and begin the process of getting their 787s back in the air,” said Ray Conner, heading Boeing’s Commercial Airplanes unit.

(Photo: Accura Media Group)

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