Power in the Field
BATTERIES AND FUEL CELLS OF ONE TYPE OR ANOTHER HAVE BECOME ESSENTIAL BATTLEFIELD GEAR. SOF CAN’T LEAVE HOME WITHOUT THEM.
The proliferation of battery-powered electronic devices carried by soldiers is revolutionizing the face of modern warfare. But it is also resulting in a tremendous increase in the need for batteries. And for the foot soldier, that means lots of extra weight in his or her rucksack.
It is not uncommon to carry dozens of pounds of batteries in a rucksack. But thanks to advancements in rechargeable battery technology, a 40-pound battery back could be replaced with a 6 to 8 pound energy pack while retaining the same amount of energy, according to S. Paul Dev, president of D-Star Engineering, Shelton, Conn.
According to a Jane’s Strategic Advisory Services report titled “Powerful Challenges: A View on the Evolving State of Powering Technologies for Soldier-Borne Equipment,” a squad leader might need to carry at least 20 pounds of batteries, and upwards of 35 pounds for a special operations operator for a five-day mission, according to the same report. And while normal battery life typically is less then eight hours, missions of the 101st Division typically last 12-18 hours, prompting the need for multiple battery switches during the course of a mission.
There are between 450 and 500 items in the U.S. Army inventory that consume battery power, including radios, laser range finders, night vision equipment, laptop computers, and unmanned aerial vehicles. There is an urgent need, therefore, to reduce battery requirements while maintaining the same amount of power. In addition to using primary (nonrechargeable) batteries that are lighter weight, there is substantial emphasis on rechargeable batteries.
Apart from reducing weight, rechargables can save lives. Several years ago, for example, some South Korean special operations soldiers reportedly died of exposure during winter exercises. It was found that the batteries that powered their radio no longer worked, and they had no way of recharging them.
The adoption of rechargeables, however, has been slow. Much of that is because of cultural resistance. According to Randy Nelson, sales manager of Bren-Tronics, Inc., Commack, N.Y., which supplies batteries to the Army, factors include the need to manage an additional activity; whereas disposables are simply discarded after their use and replaced with new ones, rechargables require the need to handle and utilize extra equipment— namely chargers.
There also is the “if in doubt, throw it out” mindset; according to the Jane’s report, even batteries that still have plenty of life are discarded in favor of fresh replacements, in order to ensure that a critical piece of equipment will not fail. “Also, they might think, ‘This isn’t charged fully,’” said Nelson. “And if you’re going out on a mission, it’s going to be critical. You want to make sure you have a new battery. With brand new non-rechargables out of the box, you know it’s fully charged.” Nelson added that, under the older, nickel cadmium technology, rechargables had a reputation as being undependable.
Since 1996, his company, Bren-Tronics, has produced and/or supplied batteries as a sole supplier to the Army. The company provides the preferred batteries as listed by the U.S. Army Communications and Electronics Command (CECOM) at Fort Monmouth, N.J. The preferred battery list describes the various form factors and electrical characteristics of a series of 11 batteries. There are both rechargeable and non-rechargeable versions of each of these batteries.
ENERGY INDEPENDENCE
The culture is changing. “This generation’s soldiers, being trained on computers and electronics, know full well that if they do not have power with them when they need it, they will not be able to communicate. I believe the behavior change will happen in this generation by virtue of [the] soldier’s renewable energy awareness,” commented Tim Teich, vice-president of sales marketing and product development for Global Solar Energy, Inc., Tucson, Ariz.
“Today’s soldiers are used to carrying iPods, PDAs, cell phones and laptops everywhere they go. And they use rechargeable batteries. They’re already developing discipline that says, ‘I have to make sure I have my battery charged when I go, wherever I go,’” pointed out Nelson.
Perhaps more important, the technology is changing, too.
When rechargeable batteries first came out, they were made of nickel cadmium and subsequently nickel metal hydride. “They put a bad taste in many people’s mouths because they didn’t work very well compared to primary batteries,” explained Teich. Now the material of choice for rechargables is lithium-ion—a much more robust technology that is only a couple of years old. For the SINCGARS radio, lithium-ion achieves a weight saving of one pound over existing technology, with 50 percent more battery life, according to the Jane’s report.
With rechargables, “The idea is that after your first four cycles, you basically pay for the battery. And after those four cycles, all the rest of them are free, in comparison to nonrechargeables,” remarked Nelson.
So rechargeables are gaining ground. “In 1995 you probably had less than 10 percent of battery usage going to rechargeables,” indicated Nelson. “In 2001 it might have grown to around 25 percent. There are some market studies that show that they’re up to about 35 percent at this point. So it’s a steady climb, and what’s causing that is that truly a cultural barrier is breaking down. And the batteries last longer and weigh less than they used to. They’re more dependable.”
Nelson says rechargables are “without a doubt” becoming more accepted in the Army. “First, they’re getting lighter. And they’re lasting as long as their non-rechargeable counterparts. Now, if you’re going on a fourday mission and you know how long your battery lasts and what you’re doing with it, you have to carry a supply of batteries with you to meet that four-day mission. So they go out and they grab what ever they need...say, 10 batteries. With rechargeables, what they’re learning is that if they can manage it, they can take two to four batteries and complimentary field chargers to be able to charge these things. And that gives them energy independence on the battlefield.”
He continued, “With a disposable battery, a SINCGARS radio typically would last 36 hours. With a rechargeable it would last for the same 36 hours, and then you’d recharge it and it would last for another 36 hours. And they could do this hundreds of times.”
DISPOSABLES STILL REIGN
Primary or non-rechargeable battery technology is advancing as well. A SINCGARS radio can run between five and nine days using a BA-8180/U zinc-air battery as compared to the normal 18 hours using the conventional battery. About the size of a notebook computer, it has the energy equivalent of five to seven BA-5590 battery packs. In 24V mode, the battery can last up to more than 50 hours on .5 amps, and up to 110 hours in 12V mode.
Being made of zinc-air, it is half the weight of lithium battery for the same mission run time. “So it runs twice as long as lithium with the same weight,” said Graydon Hansen, president of Electric Fuel Battery Corporation (Auburn, Ala.), which manufactures the BA-8180/U and the smaller BA-8140/U.
He continued, “If the guys are in training and they want to save money, they’re encouraged to use rechargeable. The units that go into combat don’t trust rechargeables as much. So they’ll tend to use primaries, because they’re sure the primary is full when they open the box.” The BA-8180/U is about 3kg. And the company just released the BA-8140/U, which is half that size, with half the discharge time. It is designed to run the MBITR radio for up to a full week.
HARNESSING THE SUN
Battery chargers are also advancing. Among the innovations is a flexible, foldable technology to make rucksack-portable solar panels. The principal material is thin-film copper indium gallium de-selenide (CIGS).
The wattage of solar blankets keeps rising. “The Global Solar foldable panel offered was 30 watts. They’re up to 55 watts right now and climbing, while maintaining the same size,” said Teich. “So they’re getting more efficient. That improves the cost factor.” Solar panels are obviously ideal for sunny environments such as Iraq and Afghanistan. And in other climates, as long as there is some degree of sunlight and even clouds present, this technology still can provide a charge.
Global Solar developed a CIGS cell under Defense Advanced Research Projects Agency (DARPA) funding. CECOM has selected Global Solar’s technology for soldier rucksack portable charging with solar panels. The company is supplying the panels bundled with Bren- Tronics’ lithium-ion BB 2590 battery, a patio brick-sized battery that powers the SINCGARS radio. The power pack is now being deployed in its final stage of testing with troops at both local and international bases.
Folded, the 55-watt solar panel is 9 inches by 11 inches and when unfolded reaches 32 inches by 48 inches. It takes as little as six hours to recharge the BB2590, depending on solar conditions. “The initial product shipped over a year ago, and we got a lot of feedback along the lines of, ‘This is great.’” said Teich.
Global Solar also has developed a 6,000 watt trailer system, which is a hybrid system of fuel cell generator and solar panel to provide power in large amounts, such as to a tent community.
“All of this is done with our foldable solar panels, which are rugged and lightweight,” said Teich. “For instance, our 55-watt panel weighs three-and-a-half pounds. If you bought s 55-watt framed glass solar panel for your roof, by contrast, it would be upwards of 25 to 30 pounds.” The solar panels are rucksack portable, folding into a pack of the size of a notebook.
According to Teich, the military made the decision that new handheld electronic equipment should be developed using an AA battery platform, due to their worldwide availability. “Now, [we’ve] got the problem of, for instance, a Special Forces soldier having to carry 30 to 40 to 50 AAs in some fashion with his gear so he can get through a mission. With CECOM we developed [a] small 6-watt charger, enabling the soldier to take only four to 12 rechargeable batteries and daily restore his power.”
The AA charger, when folded, is as small as a wallet. It will charge four batteries—depending on the capacity of the particular battery—in three to five hours. Folded out, the panel is about 18 inches long and 5 to 7 inches wide.
“It has been designated as a dual-use charger so a cell phone, satellite phone, PDA or radio can plug into it. Actually, every soldier could take it with him and cover his basic charging needs.”
DIESEL POWER
Small, rucksack-portable diesel-powered generators/rechargers soon will be available. Thanks in part to a DARPA grant, D-Star Engineering developed “micro diesel” engines, housed in a handportable unit. It is a hybrid device, consisting of an internal battery in addition to the engine. It runs on diesel or JP/8 fuel—the same fuel that powers most military ground vehicles.
The 50-watt battery chargers have been validated in the lab, and three prototypes are expected to be ready for field testing by the Army in March or April 2006. D-Star also has a 700-watt unit, of which two fully functional prototypes of the 700-watt version have been delivered to USSOCOM for testing. They also have been demonstrated to the Rangers and to the Army Mobile Electric Power Branch at Fort Belvoir, Va.
“With this device, the soldier would not have to carry so many batteries,” said Dev. Not only would that save the weight of the batteries, but also the cost of the batteries.”
The 50-watt unit, designed for use by one individual soldier, also can be used as an on-board battery charger or an auxiliary power unit for small, hybrid-electric unmanned ground vehicles. It is designed for the Future Force Warrior (formerly Land Warrior).
A soldier is estimated to use about 15-watts of power on average, typically over the course of a day. Of course, his peak power needs can be much higher, such as 50 or 100 watts, e.g. when he is conducting a satellite transmission. “Our goal is to supply each soldier with this personal battery charger, to charge his batteries about once a day, maybe twice a day. So if we charge it once a day, he would run it for eight hours, and the 50-watt system for eight hours will put in 400-watt-hours of energy, which comes out to a little more than 15 watts on average,” explained Dev.
He continued, “Let us say he is simultaneously both charging his battery and running a load off of the system. And he suddenly does a radio transmission and he uses up 75 watts. The system will provide this 75 watts temporarily.”
The size of the device is 6 inches by 6 inches by 6 inches. That includes a one-quart fuel tank. That quart of fuel would last 16 hours. The empty weight of the system is about 3 pounds, and the total weight, with fuel, is about 5 pounds. The 700-watt unit is about 17 inches long, and it is about 10 inches wide by 9 inches tall. It is more designed for use by a whole squad of soldiers rather than an individual.
PORTABLE FUEL CELLS
Fuel cells convert hydrogen-based fuels to energy via an electrochemical process. A common ingredient in fuel cells is liquid methanol combined with gaseous hydrogen. “Compared to batteries, fuel cells typically deliver a significantly longer duration of power at up to onetenth the weight, while occupying comparable volume,” according to Ball Aerospace & Technologies Corp., Boulder, Colo. Portable fuel cells can weigh less than 10 pounds.
Ball Aerospace offers three fuel cell systems—20 watt, 50 watt and 100 watt. The 20 watt system is a direct-methanol fueled fuel cell,designed to provide direct power or work in conjunction with a hybrid rechargeable military battery. It weighs just over 2 pounds and provides up to 400 watt-hours of energy from a single liquid methanol fuel container, which is about the size of an eight-ounce aluminum can. The 50-watt and 100-watt versions require an external source of hydrogen gas, such as compressed hydrogen.
Ball Aerospace is also developing systems in a fully man-wearable configuration. It is about the size of a VHS videocassette and weighs 1.5 pounds.
Meanwhile, MTI Micro, Albany, N.Y., has delivered to USSOCOM five hybrid direct methanol fuel cell prototypes to power items such as radios and remote sensors. The five power packs in the same form factor of the BA-5590, one of the most commonly used batteries in the military.
In addition, the Army Research Laboratory, in conjunction with Mesoscopic Devices, Broomfield, Colo., is developing a 20-watt direct methanol fuel cell. It is to be used for a continuous trickle charge of a rechargeable battery, or as a direct power source. “For a 72 hour mission and 20 watt average load, this system would reduce the soldier’s load from 16 pounds of primary batteries to 8 pounds including rechargeable battery, fuel cell and fuel canisters or 4.5 pounds for the fuel cell system with fuel canisters,” according to the U.S. Army Research, Development and Engineering Command. Re-supplying the fuel cell only involves having more methanol fuel canisters. ♦