When a stationary Japan Airlines (JAL) 787-8 had a battery malfunction at Boston Logan International Airport on January 7, 2013, it marked the start of a series of events which brought into question Boeing’s use of lithium-ion (Li-ion) batteries to power systems in the aircraft. Two days later, new concerns arose when United Airlines reported a similar problem on one of its 787s, when wiring in the same area as the battery fire on JAL’s aircraft caught fire. On January 12, 2013, a second Japanese carrier, All Nippon Airways (ANA), was forced to make an emergency landing at Takamatsu Airport following warnings that its Li-ion battery was malfunctioning.
In response, Boeing — already smarting from having its flagship widebody arrive three years later than planned — was ordered by the FAA to ground all active 787s and halt the delivery of new aircraft until a solution was found. The aircraft had clocked just 52,000 flight hours before the problems had occurred, far short of Boeing’s prediction that a smoke incident may occur on the 787’s Li-ion batteries after 10 million flight hours.
Looking to get the 787 back in the skies, Boeing implemented a retrofit solution that didn’t completely fix the issue, but safeguarded the aircraft in the event of future fires. This modification included a battery and charger redesign, as well as reinforcing the steel box containing the battery to contain any fires and to vent hot gasses outside the aircraft. Larry Loftis, head of the 787 project, said in April 2013 that Boeing saw its amends as “the permanent fix”, and stated it found no compelling reason to move away from the Li-ion battery. The amendments led to the FAA approving the 787 to return to operation in May 2013, but scepticism remained over the safety of the battery. This scepticism didn’t abate following Boeing’s admission that it didn’t know what caused the fires and that it may never find out.
However, the cause of the first incident in Boston did come to light in December 2014, when a report from the US National Transport Safety Board (NTSB) concluded that the battery had design flaws which led to an internal short circuit leading to the thermal runaway of its cell — when the heat generated by a battery exceeds that which can be dissipated. Because of this, flammable materials were ejected outside the battery’s case resulting in a small fire. In the same report, the NTSB issued 18 recommendations to Boeing, GS Yuasa (the battery manufacturer) and the FAA, which it said should not have certified the aircraft. Earlier in the year, the FAA declared the 787 safe, but criticised Boeing’s supply-chain management, stating the need for the OEM to have a better “oversight of its suppliers”.
The 787 supply chain is vast and includes the likes of Thales, which designed the aircraft’s subsystem containing the Li-ion battery. The FAA said Boeing, which outsourced an estimated 70 per cent of parts and components to first-time subcontractors for the 787 needed to better manage the flow of information, standards and expectations between itself and its suppliers, while improving technical milestone checks during an aircraft’s development. When compared to Boeing’s other aircraft programmes, which typically see 30–50 per cent of parts to third parties, the 787’s supply-chain model proved quite the gamble.
Around the same time, the Japan Civil Aviation Bureau (JCAB) called for Boeing to implement a complete redesign of the battery, instead of the partial installation fix carried out. Whether or not this will be forthcoming remains to be seen, but JCAB acknowledged that public concern was a primary factor behind its recommendation. “It is considered that, for keeping peace of mind for the passengers and the public on the safety of the 787 fleet, further improvements of the reliability for cells and battery system are necessary,” it stated.
While JCAB may be convinced that the travelling public has concerns over the use of Li-ion batteries in aircraft, have industry attitudes towards them altered? M Stanley Whittingham, professor of chemistry, materials science and engineering at Binghamton University in New York, has led research into Li-ion batteries since the first non-rechargeable lithium batteries became commercially available in the 1970s. He says like with most technologies, there will always be an element of risk associated with the deployment of new batteries. “It’s all a matter of risk, and what level of risk companies using the batteries are willing to take,” he says. “High volumes of energy are being stored in a small box so of course Li-ion will be a bit riskier than other battery forms.” While Li-ion batteries have been used to power electronics devices and consumer products for more than 20 years, the 787 marked the first time they were used to run key aircraft systems. The majority of commercial aircraft continue to use vented nickel-cadmium (Ni-Cad) batteries as a power source. While these batteries have served the industry well for many years, the desire for lighter and more efficient batteries has turned attentions towards Li-ion technologies.
And statistically, their benefits make for impressive reading. Li-ion is estimated to be around 35–50 per cent lighter than Ni-Cad equivalents, and Boeing estimates that choosing Li-ion for the 787’s main battery shaved around 90kg off the aircraft’s weight. Lighter aircraft, of course, means lower fuel burn, so it’s no wonder that OEMs’ interest in Li-ion has been piqued. Alongside GS Yuasa, which declined to speak to ATE&M owing to a non-disclosure agreement with Boeing, French battery manufacturer Saft is a major supplier of Li-ion batteries. While Saft had no involvement in the 787, it has developed a Li-ion battery for the 787’s rival, the A350. Saft started on the project in 2008, however, following the 787 groundings Airbus confirmed that despite designing the A350 to be powered by Li-ion batteries, it was switching to Ni-Cad batteries for the first few production aircraft. Referencing the 787 incidents, which Airbus described as being “unexplained”, the OEM stated the decision was a means of mitigating risk as well as preserving the aircraft’s flight-test and entry-into-service schedule.
In September of last year, Airbus confirmed its intention to reinstate the use of Li-ion batteries on all A350-900s produced from 2016 onwards and Saft has confirmed that EASA certification for the Li-ion battery is imminent. It is understood Airbus’ renewed confidence in the technology was a result of the rigorous testing carried out in the 17 months between its February 2013 announcement. This was alluded to at the time of the announcement, when Gordon McConnell, chief designer of the A350, told the media: “We flew lithium-ion batteries for all the development aircraft, accumulating big experience on the flights. From the very beginning we were fully aware of the conditions of use, and how we could mitigate any risks to zero.”
A growing market
Antoine Brenier, international sales and marketing director for aviation at Saft, says that Airbus’ decision to reintroduce Li-ion batteries was the result of “minor” changes to the A350 battery. While unable to disclose specific technical details about the changes due to confidentiality agreements with Airbus, Brenier says: “It was more a set of modifications aimed at making the battery more mature and efficient rather than safer, because as far as we’re concerned it was already safe.”
The design of the A350 Li-ion battery was noted for its cautious approach, with Saft designing it to have a more conservative power output and energy levels than the GS Yuasa-designed batteries on the 787. Though modifications mean the A350 battery will be heavier than the initial 787 design, with four batteries needed to be installed on the A350 instead of the two batteries found on the 787. One of these batteries will be dedicated to starting the auxiliary power unit (APU), while the other three will be sources of power to other components. In contrast, the main battery on the 787, which is located at the front of the aircraft, powers maintenance systems and provides backup power for the aircraft’s control systems. The second battery, situated in the back of the aircraft, is used to start up the APU.
The number of maintenance teams currently servicing Li-ion batteries reflects the relatively small number of active aircraft using them. As ATE&M goes to press, a total of 247 787s equipped with Li-ion batteries have been delivered to airlines. But with the order backlog of 787s standing at 1,072 aircraft, and with 789 A350s on order, the market for Li-ion battery maintenance is clearly a growing one. However, one of Li-ion’s primary selling points is that the batteries require less maintenance than alternative technologies. While Ni-Cad batteries must be removed from the aircraft every six months or so — for maintenance including water replenishment and to undertake a deep discharge, for example — Li-ion batteries can be checked on-wing, reducing downtime.
Image is everything
Despite the faith the likes of Boeing and Airbus have in using Li-ion technologies in next generation aircraft, Brenier concedes the batteries have a wider image problem owing to the 787 grounding and high profile events from outside the aviation sector, such as Dell and Apple recalling thousands of Li-ion powered laptops after reported fires in 2006. Brenier remains upbeat, however, arguing that these misconceptions will erode as the Li-ion batteries become more commonplace in commercial aviation. “What we don’t talk about are the thousands of batteries safely and reliably performing their duties on laptops, computers and products in our industrial markets,” he says. “There is certainly an image issue with Li-ion but over time this will improve as more people see its value as a safe, reliable and beneficial technology.” Whittingham, meanwhile, cites the long history of batteries being used on BAE Systems’ buses, as an indicator of the technology’s viability for powering large vehicles.
Dr Daniel Doughty, president and founder of Battery Safety Consulting, an Albuquerque, New Mexico-based consultancy firm advising on Li-ion-related issues, says battery malfunctions on an aircraft brings an added sense of danger not associated with consumer products. “In electronics, there’s a very low frequency of events, but sometimes they are catastrophic, for example when a laptop catches fire, but people seem to be accepting these risks. However, there is a higher level of weariness for aircraft, mainly because people understand that while statistically you may be safer on an aircraft than say in a car, psychologically they don’t feel safer.”
Despite Li-ion battery use being deemed safe by aviation regulators for powering aircraft systems, there remains debates with regards the safe transport of Li-ion batteries, which present further perception problems. In March 2015, the International Coordination Council of Aerospace Industry Associations (ICCAIA), which represents OEMs including Boeing, Airbus and Bombardier, called for a ban on bulk Li-ion battery shipments on all passenger aircraft, a ban backed by US carriers Delta and United. The ICCAIA also called for stronger packaging and handling regulations for batteries shipped on cargo planes. Li-ion batteries have also been touted as a possible cause for the disappearance of the MH370 last year; with Malaysian Airlines confirming the 777 was carrying large loads of the battery type.
While Li-ion aircraft batteries might continue to struggle to win around the public, Whittingham predicts that they will continue to attract the attention of aircraft OEMs. He predicts that within the next 10 to 15 years they will become markedly more powerful. “Many believe Li-ion batteries will one day be able to store 50 to 100 times more energy than they can today,” he says. While in the world of commercial aviation, Li-ion batteries remain a young and relatively unproven technology, all indicators point to it becoming the industry norm at some point in the future. Its champions will no doubt be hoping that the way forward is considerably smoother than its journey so far.