The Patents Behind the Plane
The Boeing 787 Dreamliner is much in the news due to several high profile problems associated with the lithium ion (Li-ion) batteries integrated into its electrical system, not the least of which is its grounding by FAA:
"As a result of an in-flight, Boeing 787 battery incident earlier today in Japan, the FAA will issue an emergency airworthiness directive (AD) to address a potential battery fire risk in the 787 and require operators to temporarily cease operations. Before further flight, operators of U.S.-registered, Boeing 787 aircraft must demonstrate to the Federal Aviation Administration (FAA) that the batteries are safe....
"The in-flight Japanese battery incident followed an earlier 787 battery incident that occurred on the ground in Boston on January 7, 2013. The AD is prompted by this second incident involving a lithium ion battery. The battery failures resulted in release of flammable electrolytes, heat damage, and smoke on two Model 787 airplanes. The root cause of these failures is currently under investigation. These conditions, if not corrected, could result in damage to critical systems and structures, and the potential for fire in the electrical compartment."
FAA press release statement, January 16, 2013
FAA issues airworthiness directives (ADs) in three tiers, with the emergency AD “issued when an unsafe condition exists that requires immediate action by an owner/operator. The intent of an Emergency AD is to rapidly correct an urgent safety of flight situation.”
The lithium ion batteries are used in the Dreamliner to start the auxiliary power unit and to provide flight system power backup and computer display startup power.
Boeing took an innovative approach to building the Dreamliner - use a global network of suppliers to develop, and then build, most of the parts in locations in many locations including Germany, Japan and Sweden. Boeing employees manufacture just 35% percent of the plane before assembling the final aircraft at its plant outside Seattle. This approach has spread innovation across the globe as well. There are many news reports and other online sources that discuss the Dreamliner battery problem, but what of the patents behind the batteries?
The Companies
Boeing chose the French firm Thales as the prime contractor to provide “electrical power conversion technology … to efficiently power the vast array of consumer systems onboard the B787 with the least environmental impact.” Thales stated that “Boeing chose Thales’s lithium-ion battery technology, which provides higher reliability and improved maintenance compared to traditional solutions, for the B787 low-voltage DC emergency back-up subsystem. This is a first in civil aviation, with Thales as prime contractor in association with Securaplane of the United States and GS Yuasa of Japan.”
Securaplane Technologies, Inc., headquartered in Tucson, AZ, supplies avionics products to the aviation industry including batteries, battery chargers and inverters. Securaplane manufactured the chargers for the Dreamliner lithium ion batteries; on January 20, 2013 the National Transportation Safety Board (NTSB) stated that those chargers did not cause battery overcharging.
GS Yuasa Lithium Power, formed in 2006 and located in Roswell, GA, is the manufacturer of the Boeing 787 Dreamliner Li-ion batteries. The company’s LVP10 and LVP65 Li-ion cells are used in the aircraft.
The Patents
We conducted searches for potentially relevant US and international patents of these companies. Some of the representative inventions that support the Li-ion technology under investigation are summarized below.
Thales
Thales is listed on more than 11,000 patents or applications worldwide according to Espacenet. One of those specifically relates to Li-ion battery technology. WO2005031943, “Module load transfer between two dipoles,” issued in April 2005, and provides a system for the “equilibration of dipoles in a battery of rechargeable cells, particularly lithium ion or supercapacitance type cells.” A related US patent “System for equilibrating an energy storage device” (US7,755,325) issued in July 2010. Inventor Christophe Taurand notes that:
"The number of [electrical storage] elements depends on the application aimed at: typically 24 volts in the industrial sector, 28 volts in the aeronautical sector and 42 volts in the automotive sector. If we take cells of lithium-ion type (4 volts for a charged cell) and an aeronautical application, an energy storage device thus typically comprises 7 elements. A charger, comprising a power converter supplied by the main network and whose output is regulated in voltage and in current, makes it possible to charge the cells which are connected in series. … Lithium-ion … cells are very sensitive to overvoltages, thereby requiring monitoring of the voltage at the terminals of each cell. … if a cell recharges more quickly than the others, it will overcharge (voltage greater than 4 volts for a lithium cell)."
His invention provides,
"...an equilibrating system … to maintain an identical voltage on all the storage elements. The basic principle of equilibration consists in the monitoring by the [battery monitoring unit] of all the voltage differences between the series elements of the storage device, so as to trigger the equilibrating system as soon as at least one of these voltage differences exceeds a certain critical value."
Securaplane
Four US patents have been issued since 1998 to Securaplane, three of which are relevant here.
US8,38736, “Power system having a local sense control dominant over a remote sense control to avoid effects of interconnection failure modes,” is “generally directed to electrical power systems, and, more particularly, to a power system configured with a local sense control dominant over a remote sense control to avoid effects of one or more failure modes that can occur in interconnecting lines of the system.”
US8,057,931, “Battery busing scheme,” provides for interconnecting (busing) the cells of multi-cell batteries:
The busing concept described herein utilizes components that enable one to reduce the assembled height of the packaging of the battery pack as compared to prior art. The concept reduces the need for large gauge inter-connect cabling by incorporating bus clamps for the main power inter-connects. Internal monitoring circuitry can also be incorporated into a printed circuit board which is part of the bus assembly. Utilizing all of the components of the concepts described herein will allow a minimal envelope for the battery pack into its enclosure.
US5,780,994, “Detection of inflection point in secondary-battery charging process by matching voltage response to first derivative of battery’s characteristic curve,” “pertains in general to the field of battery chargers. In particular, the invention consists of a novel approach for detecting the voltage-response inflection point during the process of constant-current charging of secondary batteries.”
GS Yuasa
GS Yuasa has received 74 US patents thus far. Fourteen of these are directly related to lithium-ion battery technology, of these three reference the lithium cobalt oxide formulation of the Dreamliner batteries.
US7,393,476, “Positive electrode active material for lithium secondary cell and lithium secondary cell,” provides a composite lithium-manganese-nickel-cobalt oxide cathode which reduces the amount of scarce and expensive cobalt needed, yet reduces abrupt decreases in battery discharge capacity following repeated charge/discharge cycles that can result from using that composite.
US7,691,535, “Active substance of positive electrode and non-aqueous electrolyte battery containing the same,” addresses the crystalline structure of the oxide composite, and according to the inventors, “retains the high thermal stability characteristic of lithium-manganese oxides having a spinel structure, has a high energy density and excellent high-rate discharge performance, is inhibited from suffering self-discharge, and has excellent storage performance.”
US7,964,305, “Non-aqueous electrolyte battery wherein a battery case and a terminal are connected through resistance,” relates to the structure of a lithium cobalt oxide metallic battery case.
The Wrong Battery?
Research firm Lux Research has suggested that a safer alternative to lithium cobalt oxide (LCO) batteries might have been chosen. They point out that LCO batteries do not resist overheating very well. They suggest that lithium iron phosphate (LFP) batteries are a safer alternative, being resistant to thermal runaway and oxygen generation in response to overcharging.
Many US patents related to lithium cobalt oxide batteries or cells (i.e., mentioned in the title, abstract, or claims) have been granted from 1972 through 2013. The earliest and latest in each category are listed below.
Title (9 grants)
US 6,521,379 Non-aqueous electrolyte secondary cell with a lithium cobalt oxide positive electrode, 2003, Sanyo Electric Co., Ltd.
US 8,354,191 Layered lithium nickel manganese cobalt composite oxide powder for material of positive electrode of lithium secondary battery, process for producing the same, positive electrode of lithium secondary battery therefrom, and lithium secondary battery, 2013, Mitsubishi Chemical Corporation
Abstract (144 grants)
US 4,555,457 Battery cell containing potassium monoperoxysulfate in the cathode mix, 1985, ACR Electronics Inc.
US 8,354,191 Layered lithium nickel manganese cobalt composite oxide powder for material of positive electrode of lithium secondary battery, process for producing the same, positive electrode of lithium secondary battery therefrom, and lithium secondary battery, 2013, Mitsubishi Chemical Corporation
Claims (811 claims)
US 3,647,542 Sold-fluid battery, 1972, McDonnell Douglass Corporation
US 8,354,192 Electrode active material, electrode, and nonaqueous electrolyte secondary battery, 2013, Sumitomo Chemical Company, Limited
Here are the citations for patents for lithium iron phosphate batteries, granted from 1974 through 2013.
Title (1 grant)
US 6,835,500 Hydrated iron phosphate electrode materials for rechargeable lithium battery cell systems, 2004, Rutgers University
Abstract (45 grants)
US 4,452,873 Positive electrode for galvanic high-temperature cells and method of its manufacture, 1984, Varta Batterie Aktiengesellschaft
US 8,137,841 Cathode compositions for lithium-ion electrochemical cells, 2012, 3M Innovative Properties Company
Claims (133 grants)
US 3,847,671 Hydraulically-refuelable metal-gas depolarized battery system, 1974, Electromedia Inc.
US 8,343,661 Cathode compositions comprising Zn and chalcogenide and energy storage cell comprising same, 2013, General Electric Company
The Bottom Line
The investigations now underway by the FAA, NTSB, Boeing, the Japanese government, Thales, Securaplane, GS Yuasa and others will ultimately determine root causes of the 787 Dreamliner Li-ion battery problems, which will lead to corrections and guidelines for the future application of lithium battery technology in the aviation industry. It is not clear exactly which patents the companies involved have licensed to support the design and manufacture of the electrical systems in question. Knowledge of the licensing agreements and the specific underlying patents might be an important component for the root cause analyses now underway.
To paraphrase a line from the movie ‘Cool Hand Luke’, what we have here is … an excellent example of unintended consequences of using technology in a way that pushes the envelope of past engineering practice.
