Fighting Form: Military Takes On Battery Fatigue

By KEITH JOHNSON

Since at least the time of Alexander the Great, military leaders have sought to dominate logistics. Today, the U.S. Army and Marine Corps are grappling with a unique logistical challenge that has mushroomed in the past decade: the proliferation of electronic devices and batteries required to keep the average foot soldier in the fight.

Battery life hasn't kept up with gadget innovations, but inventors are on the case, Ian Sherr reports on digits.

The explosion in electronic gear in the modern military, from radios and GPS equipment to night-vision goggles, means a typical soldier may carry a dozen devices and 70 batteries on a three-day patrol. That adds weight—16 pounds or so—to already-overburdened warriors.

A typical soldier or Marine today carries more than 100 pounds on his back, roughly twice as much as dogfaces did in World War II. A typical infantry company of roughly 150 soldiers requires more than 6,600 batteries, weighing more than 1,400 pounds, for 72 hours of operation. All that weight slows down soldiers on foot, tethers them to constant resupply, and contributes to a rash of muscular and skeletal injuries caused by excessively heavy packs.

Solar Soldiers

Scientists at defense laboratories, including the Office of Naval Research and the Army Research Laboratory, are targeting battery proliferation as part of a much wider Pentagon effort to change the way the armed forces use energy. Marines in the front lines in southern Afghanistan last year received portable solar panels that helped them curb their fuel consumption and save on batteries. The test project, which enabled the Marines to recharge in the field and become a lot more mobile, is now being rolled out more aggressively.

Another big push is to develop "soldier power," or ways for soldiers in the field to become their own sources of energy. One idea turns soldiers into virtual docking stations by packing large batteries into their body armor.

Wearable batteries have been available for some time. Airborne units in Afghanistan have field-tested systems in which soldiers pack a large, curved battery over the plate in their body armor. The big central battery keeps most electronic gear continuously charged up, lessening the drain on the litany of smaller batteries, so fewer spares are needed. Such systems can shave at least three pounds of weight off what a soldier needs to carry on a three-day patrol, says Cody Reese, who oversees the soldier-power program at the Office of Naval Research in Arlington, Va.

Kinetic Tactic

Further down the road, soldiers might be able to do away with some batteries by harnessing kinetic energy produced by the very packs they struggle under. The idea is simple: Packs are mounted on a slider on a soldier's back, and the up-and-down shifting of the load drives a small piston, which captures the kinetic energy. Some airborne units in Afghanistan earlier this year carried 3.5-watt kinetic-energy harvesters. Trials so far have captured "tens of watts" for each soldier, enough to power field radios.

"Tens of watts is extraordinarily useful," says Mr. Reese.

The big challenge now: Making energy-harvesting systems rugged enough to withstand constant abuse.

Mr. Johnson is a staff reporter in the Washington bureau of The Wall Street Journal. He can be reached at keith.johnson@wsj.com.