Lithium-ion batteries: still at full power?

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.
Permanent fix
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.
Industry take
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.
- See more at: http://www.mro-network.com/analysis...es-still-full-power/5538#sthash.Rb4lFr3A.dpuf