Boeing (http://www.boeing.com/787-media-resource/) this week outlined its plan to fix suspected problems with the lithium-ion batteries used in its flagship 787 “Dreamliner.” The U.S. Federal Aviation Administration (FAA) approved Boeing’s proposal last week.
The enhancements to the battery system address causal factors identified by the Boeing technical team as possible causes of battery failure, the company said. The technical team's findings also were verified by an independent group of lithium-ion battery experts from a number of industries, universities and national laboratories.
Boeing battery supplier GS Yuasa has said the batteries are not defective.
"We've come up with a comprehensive set of solutions that result in a safer battery system," said Mike Sinnett, vice president and chief project engineer, 787 program, Boeing Commercial Airplanes. "We have found a number of ways to improve the battery system and we don't let safety improvements go once they are identified. We incorporate them into our processes and products."
Among the measures Boeing announced:
· 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.
· Four new or revised tests have been added to screen cell production.
· Boeing, Thales and GS Yuasa will 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.
· Changes inside the battery will help to 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.
· A set of changes is being made to the battery case that contains the battery cells and the battery management unit.