Power hungry: Army seeks light, efficient batteries to meet insatiable energy demand.
All that could change, if Steve Slane has his way. Slane, chief of the battery branch at Army Communications-Electronics Research, Development and Engineering Center (CERDEC) at Fort Monmouth, N.J., is working with several contractors to develop new battlefield batteries--an effort employing 30 Army scientists and engineers and budgeted at around $15 million annually.
One recent innovation championed by CERDEC is a simple charge indicator built into a battery's casing so that soldiers don't have to guess how much juice is left. Such indicators are now standard on all new large batteries. A combination of lighter, longer-lasting batteries and innovations such as the charge indicator, can make a huge difference for soldiers in combat, Slane says.
In today's high-tech Army, where even the smallest patrol counts on a wide range of electronic systems--including radios, network terminals, night-vision goggles, radio jammers and shoulder-fired rockets--batteries are a critical resource. And demand is growing. "Five to 10 years ago, a soldier on average would consume three to four watts of [battery] power" on a typical mission, Slane says. "Today ... we're seeing power numbers of around 20 watts."
Watts are a generic unit of power, or work. Wattage is the product of voltage and current; the latter is measured in amperes.
To provide his 20 watts, a soldier might carry as many as eight 2.2-pound BA-5590 lithium sodium dioxide batteries on a mission, in addition to smaller alkaline batteries, for a combined weight of around 20 pounds--a load that outweighs even his rifle ammunition and takes up more space. As a result, battery weight and size have become important factors in mission planning. One way to reduce that load while slaking soldiers' thirst for power is to transition to more efficient chemistries.
"For the last 15 to 20 years, the majority of applications have been filled with lithium sulfur dioxide batteries" such as the 5590, says Mark Matthews, director of strategic market development for New York-based firm Ultralife, which alongside French company Saft, manufactures the majority of the million or so soldier batteries the Defense Logistics Agency consumes annually at a cost of around $100 million. CERDEC is responsible for administering the agency's orders for Army batteries.
"Lithium sulfur dioxide has been a workhorse for years," says Ben Helminen, Saft's director of sales. "Now we are looking at new chemistries. Lithium carbon monofluoride is quite promising."
But that chemistry hasn't yet found widespread acceptance for military applications. In the meantime, both Saft and Ultralife have begun producing a lithium manganese dioxide version of the 5590, designated BA-5390.
"The push has been towards lithium manganese dioxide in the same size battery [as the 5590] to get 50- to 80-percent more energy," Matthews says. "With the 5390, we're able to get double the runtime in some applications in the same size box," Matthews reports.
Ultralife's 5390 boasts a capacity of 11.1 ampere-hours of current, compared to 7.2 for its latest 5590, according to Ultralife spokesman Julius Cirin. "We're on verge of launching a 13-ampere hour version" of the 5390, he adds. "In an environment where [a soldier] might carry six 5590 batteries, he carries only three or four 5390s."
In a parallel effort to better meet soldiers' portable power needs, with CERDEC's encouragement both Salt and Ultralife are investing in improved rechargeable batteries. Greater dependence on rechargeables, versus single-use "primary cell" batteries such as the 5590 and 5390, is one way to cut the number of batteries a unit must haul along on missions.
Historically, soldiers in combat preferred primary cell batteries; the admittedly more cost-effective rechargeable batteries eked out only half the ampere-hours and so were used only in training. But an industry-wide movement towards lithium ion rechargeables has yielded longer-lasting, more robust batteries that many soldiers now feel confident using in combat. "Rechargeables are being used more and more on the battlefield," Slane says.
"With the latest increases with commercial technology, with laptop computers, we're able to get a higher-capacity, lighter lithium ion battery than in the past," Matthews says. "We are seeing more and more people seeing that as a viable option in the field. At Ultralife, we will always see a need for [both] primary and rechargeable batteries. It's highly unlikely that we'll see reusable batteries approach the capacity of primaries. But for people that are close to base or to a vehicle, it does make sense."
For reusable batteries, chargers are as important as chemistry. Ultralife has developed new multi-bay chargers for vehicles in addition to smaller man-portable chargers. The company's CH0006 Stryker charger can hold three batteries; the infantry carrier variant of the vehicle can fit three chargers for a total of nine bays--one for each dismounted soldier in a Stryker brigade squad.
"There is limited space inside a Stryker," explains Adeeb Saba, Ultralife's director of engineering. "You need to position batteries in different places to take advantage of the space, which is why you'd have three three-bay chargers" instead of one nine-bay charger. "Some Stryker variants fit only one three-bay charger. In this way, we keep things fairly modularized."
Ultralife also has a large 12-bay charger, the CH0017, that fits into most humvee variants. Its tiny CH0008, by contrast, charges just one battery at a time and is tailored for individual soldiers.
"A soldier can put it in his rucksack and use it where he sees fit," Saba says. "He can use it in his bunk or in the field with a generator ... If [he] is going to be around a vehicle, he can run his charger off an AC connection to vehicle."
"He can pretty much use any available power source," Cirin adds.
To diversify those potential power sources, CERDEC has developed what Slane calls a "solar solution to energy scavenging."
Ultralife's work on chargers parallels CERDEC's. The Army command has developed its own vehicle-mounted and individual chargers in addition to introducing commercial chargers to the force.
For both primaries and rechargeable, simply repackaging existing chemistries can result in smaller batteries without a loss in power. While this doesn't necessarily reduce weight very much, the space savings are important to infantrymen struggling to haul around a lot of bulky equipment.
"We do a lot of programs on conformal packaging of materials that would allow more body-conformal power sources," Slane says.
Conformal geometries are an especial priority for Ultralife, which has been tapped by General Dynamics Land Systems to provide batteries for early incarnations of the Army's $8-billion Land Warrior system. Land Warrior is an integrated suite for the individual soldier featuring a new intra-squad radio, a monocular display and, for squad leaders, a personal digital assistant--all of which are powered by one pair of rechargeable batteries.
New geometries "may be as simple as going from square to rectangular," Matthews says. "Think of M-16 clips that soldiers put in pouches on their vests. We went through several design iterations and came up with design very similar to that for our current Land Warrior battery. Depending on their mission, soldiers might choose to take additional batteries or additional ammo" and fit either into the same pouches.
For the future, Ultralife is investing in its trademark "thin-cell" technology, which replaces the traditional cylindrical batteries with a sort of pouch. Cylinder batteries waste at least 23 percent of their volume, Cirin reports. "You can utilize more volume" with a pouch.
Salt's Helminen is less bullish about new geometries--and he blames the Army. "It's really quite difficult to create new configurations because they [the Army] want everything to be standardized."
Says Slane, "We do have standard Army battery [configurations]. We try to get more energy into the same package. But some breakthroughs enable smaller packages."
Fuel cells are one potential breakthrough that might spawn entirely new standard batteries--but probably not any time soon, according to Helminen. "It's an old song, that that technology still has quite a lot of development to be done."
"Fuel cells," he adds, "are most likely to come into play in some kind of hybrid system," with the cells perhaps serving as a charging system for reusable batteries.
Slane concurs--but he is more optimistic. Alongside advanced chemistries such as Lithium air, which offers energy density to rival gasoline and should start fielding in around 10 years, fuel cells as part of a hybrid system are the "next step in dismounted soldier power," he says. This year CERDEC conducted tests of fuel cells intended for Land Warrior--the Army's high-tech ensemble that features multiple electronic devices, including a radio, a computer and a GPS receiver.
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|Date:||Feb 1, 2007|
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