Batteries and Advanced Airplanes

Electricity has been used in powered flight since the pioneering days of aviation. Orville and Wilbur Wright used an electrical spark to ignite the fuel mixture in the engine that powered the Wright Flyer off the ground and into the history books. Today’s jet airplanes have much more demanding requirements and consequently more advanced electrical systems, of which batteries are an integral component.

The 787 Dreamliner has two primary rechargeable batteries – the main and auxiliary power unit (APU). While identical part numbers, they serve separate purposes.

The main battery “powers up” aircraft systems, bringing the airplane to life before the engines have been started. Once the engines are started, the electrical energy to run the systems comes from generators. It also is used to support ground operations such as refueling and powering the braking system when the airplane is towed. The main battery also provides backup power for critical systems during flight in the extremely unlikely event of a power failure. It is located in the forward electronics equipment (EE) bay, which is under the main cabin floor at the front of the airplane.

The APU battery supplies power to start the APU, which in turn can start the airplane engines. The APU, and its battery, also serves as part of the multiple layers of redundancy that would ensure power in the rare possibility of a loss of primary sources of power.

Matching the right battery to the requirements

After extensive testing, Boeing ultimately selected the lithium-ion type battery because it has the right functionality and chemistry to deliver a large amount of power in a short period of time to do a high-energy task like start a jet engine. It then has the ability to recharge in a relatively short period of time so that it is available for the critical backup role that it plays during flight. Earlier commercial airplane models, such as the 777, 747 and MD-11, used nickel cadmium (NiCd) batteries, which are heavier, larger and less powerful.   

Batteries, like other technologies, have advanced significantly, and lithium-ion type batteries match up with the unique requirements of advanced aircraft.

Lithium-ion batteries have other key advantages that suit it for modern jet application:

• The required high voltage and high current production
• Improved power quality
• An ability to recharge quickly
• Similar functionality to that of NiCd batteries while weighing 30 percent less
• Compact – about the size of the average car battery

Since entering service, Boeing 787 lithium-ion batteries, each with eight cells, have logged more than 2.2 million cell-hours on the ground and in the air during more than 50,000 flight-hours. No battery-related incidents occurred before January 2013, when the airplane experienced two events. Investigation into these events is in progress.

Boeing has been using lithium batteries for decades safely and successfully in other demanding aerospace applications. For instance, they have been successfully used in the satellite industry. Closer to home, lithium batteries are being used safely to power everything from consumer electronics, household power tools and many other applications.


Boeing design philosophy

Behind the selection of any individual component is a deep commitment and philosophy about airplane design. Boeing designs airplanes with two key objectives in mind: design to prevent failures, and design in protections in case they do. Above all, the goal is to ensure that no single failure will ever prevent safe operation of the aircraft. This philosophy is integral to the battery design, which includes multiple independent protections to the battery.