This month marks the 5th anniversary of the Boeing 787 Dreamliner return-to-service after an unprecedented Federal Aviation Administration (FAA)-directed grounding of the Boeing 787 Dreamliner aircraft fleet due to a series of in-service lithium-ion battery (LIB) failures. The B-787 return-to-service marked the end to one of the most challenging periods in the history of the world’s biggest aerospace company and the beginning of a new era in a better understanding of LIB safety.
It all began with the first LIB failure (aboard a Japan Airlines B-787 aircraft parked at Boston’s Logan International Airport) on January 7, 2013, followed 9 days later by another LIB failure on an All Nippon Airways flight (en route from Yamaguchi Ube airport to Tokyo later diverted to Takamatsu, Japan). Immediately following the second incident, the FAA issued an emergency airworthiness directive to ground all US-registered B-787 model aircraft due to concerns over compliance to FAA requirements for safe operation of commercial aircraft LIB’s. The impact of the B-787 grounding reached far beyond the aviation community as questions about the intrinsic safety of LIB technologies for high-reliability applications became commonplace.
As a recognized Boeing expert on LIB power systems, I was selected to join the root cause and corrective action (RCCA) team which convened a few short days after the aircraft grounding. Co-located at The Boeing Co. Commercial Aircraft (BCA) facility (Everett, WA), the core RCCA team was comprised of a diverse mix of Boeing Co. technical experts specializing in aircraft design, thermal control subsystems, materials science, electrical power systems, and of course LIB technologies. The RCCA team was responsible for identifying technical issues, determining causal factors for the battery failures, and recommending corrective actions to ensure a safe return-to-flight for the B-787 fleet. In addition to the Boeing Co. experts, participants from Boeing Co. subcontractors, FAA, and National Transportation Safety Board investigative personnel were actively engaged.
The challenges facing our Boeing RCCA team were significant. Tasked with analyzing immense amounts of LIB forensics data collected from the incident LIB’s, conducting specialized engineering tests designed to characterize relevant LIB fault signatures, and coordination with incident investigation teams (located in Washington D.C. and Kyoto, Japan) resulted in long and exhausting work days. Comprehensive investigative test data coupled with detailed incident battery forensics analysis was at the forefront of isolating the most probable root causes for the flight battery mishaps. Within a few short weeks however, the RCCA team in close collaboration with other stakeholders, began to converge on technical recommendations for battery power system changes as well as manufacturing improvements for enhanced battery production and process controls. These recommendations included FAA-certifiable changes to the B-787 LIB itself, battery charging unit and battery installation.
Highlighted by a layered approach to increasing safety and reliability, the B-787 battery power system improvements included the addition of a new stainless steel battery enclosure. The enclosure also featured a pressure-activated vent capability designed to carry toxic battery vapors outside the airplane in the event of an energetic battery failure. Although the addition of the new battery enclosure system added weight to the B-787 airplane, which reduced the mass savings associated with utilizing the new LIB technology, it was a necessary part of the integrated solution to reliably mitigate the safety risk to any future battery mishaps.
Beyond the failure investigation results and B-787 battery safety improvements, there has been a continuing impact to how industry and academia now views LIB safety risks. This increased awareness has been further amplified by recent high-visibility LIB mishaps such as the Samsung Galaxy Note 7 smartphone and countless number of hoverboard, electronic cigarette, and other portable electronics LIB safety incidents. In addition, commercial airline transportation of lithium batteries is now more closely regulated by the FAA to further ensure passenger and crew safety.
Clearly, the “business as usual” approach to LIB safety is a thing of the past. New industry standards are driving lithium battery manufacturers to certify high-reliability LIB’s only after completion of rigorous safety risk assessments. Although compliance to new industry battery safety standards may adversely impact the cost to market for some applications, there are few alternatives available to battery suppliers and users alike. As such, the un-managed severity of an energetic battery safety incident has the potential to make high specific energy LIB chemistries an at-risk technology for some applications. So what’s next ?
Measurable progress has already been made and continues along the lines of improved safety design and test of LIB power systems with a special focus on:
- Implementing Battery Safe-By-Design Philosophies: LIB safety starts and ends with robust designs which incorporate verifiable safety features.
- Proactive Risk-Based Safety Assessments: Adoption and implementation of new LIB safety test protocols to assess the severity and consequences of a catastrophic battery incident.
- Safety Testing in Relevant Configurations and Environments: Recognition that LIB safety tests must be conducted in relevant system configurations and environments which replicate the intended use of the deployed LIB.
Industry lessons learned from LIB safety mishaps are not really learned unless the lesson becomes an integral part of processes and procedures for safer LIB power system designs. In the meantime, robust LIB designs compliant to industry safety standards and requirements makes LIB technologies the right choice for the future of advanced energy storage systems.