U.S. Army Eyes Carbon-Graphite Foam Batteries

November 9, 2007

3 Min Read
U.S. Army Eyes Carbon-Graphite Foam Batteries

Highly porous carbon-graphite foam structures replace lead plates in a move to dramatically extend battery life, as well as reduce weight and conserve space. Inside the carbon foam are pores into which a chemically active material is deposited to create either a positive or negative plate for the battery. “It has 2,000 times the surface area of a classic lead acid battery,” says Mil Ovan, a co-founder ofFirefly Energy, a spin-off of Caterpillar Tractor Co., where the technology was invented.

Caterpillar explored new approaches to batteries because of serious field performance problems caused by the corrosiveness of the lead current collector.

Cat's problems were exacerbated by extreme temperature fluctuations and the rough-and-tumble of field equipment.

The carbon-graphite foam technology will have applications well beyond tractors or earth-moving equipment. Early next year, Firefly will begin shipping prototype batteries for the U.S. Army's Silent Watch program, in which reconnaissance can be conducted from ground vehicles while their engines are off. The goal of the program is to provide consistent power for four to 72 hours. Other battery technologies, including lead acid, nickel and lithium, all failed government tests.

Firefly will also supply batteries to meet new truck idling restrictions in California. The new batteries will allow truckers to operate equipment such as refrigerators or microwave ovens without running the truck engine at rest stops. All sleeper-berth and other trucks will be required to shut down their engines within five minutes after stopping as of Jan. 1. New Jersey announced plans to step up enforcement of its anti-idling ban. Husqvarna is one of the investors in Firefly Energy and hopes to use the batteries some day in lawn and garden equipment.

Batteries for electric vehicles are probably two to three years off, according to Ovan.

In the current technology, the carbon-graphite foam is used to replace negative lead plates. This creates a weight reduction of 15 to 20 percent for slow-discharge single batteries and up to 50 percent for fast-discharge battery pack applications. In a version called 3D2, the foam replaces positive and negative lead plates, doubling weight savings and creating a battery that is almost impervious to the effects of both sulfation and corrosion.

Cost comparisons with other battery technologies depend on specific applications. Premium valve-regulated lead-acid batteries for trucks cost $220 to $300.

Listen to Mil Ovan of Firefly Energy explain how a proprietary carbon foam structure can replace lead plates in batteries, improving performance and reducing costs.

A carbon-graphite battery, at right, takes up much less space than a conventional lead-acide battery.

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