Lead-acid Batteries Are Old, But Effective Technology For Aviation

 - May 13, 2012, 5:30 AM
Concorde Battery's RG-380E/44SKH battery has a capacity of 42 Ah.

Concorde Battery (Stand 2404) is exhibiting its range of improved lead-acid aircraft batteries. Although lead-acid is old battery technology, having been invented in 1859, it may be soon the only one available for aviation use. According to Concorde executives, nickel-cadmium batteries could be banned to protect worker health and lithium-ion models seem too hazardous for airborne applications.

The California-based equipment manufacturer’s products are in the “recombinant gas, valve-regulated sealed lead-acid” category. This means maintenance for them is reduced compared to “vented” or “flooded” battery technologies. According to Concorde, it is not necessary to top-up cells with distilled water periodically to compensate for evaporation. Also, there is no risk of corrosion due to electrolyte spillage because when the battery is constructed, sheets made of “absorbed glass mat” absorb the electrolyte that is necessary for the battery to work.

Batteries are shipped fully charged so they are ready for immediate installation in the aircraft. “The shipping cost is lower because batteries are classified as non-spillable and exempt of hazardous material rules,” a Concorde spokesperson told AIN. Unlike with nickel-cadmium batteries, there is no so-called “memory effect” in which batteries fail to hold their full charge.

Concorde recently added heaters to some of its batteries. The heater is an element fitted around the battery itself and can be used after the aircraft’s engines or auxiliary power unit start generating electrical power. In cold environments, the heater helps the battery reach optimal temperature quicker, otherwise, it would recharge very slowly, which would be a drawback on short flights.

Asked how Concorde will face power needs in more-electric aircraft architectures, Dave Vutetakis, director for advanced batteries, suggested that separate backup batteries may be introduced. This would be more practical than always having to increase the capacity of the existing batteries. “Our largest battery currently is rated at 24V/48Ah, and there have been only a few requests to go higher than this in capacity,” he said.

The move to more-electric aircraft is largely being driven by the desire to have more efficient power management for primary systems. Braking, for example, may move from hydraulic to electric power. But these primary systems requirements do not take into account growing needs for cabin systems such as in-flight entertainment. In the event of a loss of primary power (for example, due to generator failure), all electrical power is shut off except that required for safe flight and landing, and, in Vutetakis’s view, this supports the case for continued use of batteries.

As for the future of competing battery technologies, it seems that nickel-cadmium batteries may have little future. “They are maintenance-intensive and cadmium is classified as carcinogen and is difficult to recycle without exposing workers,” Vutetakis said. Although lead is not exactly environmentally friendly, it is easy to contain and recycle, he added.

Lithium-ion batteries are lighter, which can be a major advantage in aviation applications. However, they contain a highly flammable electrolyte and any overheating can cause a fire or an explosion. Also, they are three to six times more expensive than valve-regulated lead-acid types, and all of these factors are steering aerospace firms away from their use.

Business aircraft families using Concorde batteries include, among others, Dassault Falcon, Bombardier Learjet, Bombardier Challenger, Hawker and Cessna Citation jets, as well as Socata TBM700/850 and Pilatus PC-12 turboprops.