Power Supply A Consistent Challenge As Troops Use More Gadgets
While batteries have become much more efficient and energy dense in the past two decades, they have been radically outpaced by devices and the demand for portable power. If over the past 20 years batteries have progressed in capability by a factor of three, electronic devices have leaped forward in computing capability and power consumption by a factor of 20, Michael Manna, vice president of product management for Newark, N.Y.-based Ultralife, told National Defense.
“The problem now is, a lot of the stuff that we carry, that soldiers carry, has advanced much faster than batteries. Everyone is carrying more of these devices, which means more batteries,” Manna said. “Those devices do 20 times more than they used to, but they also draw 20 times more power now than they used to.”
Army engineers want to provide useful equipment to soldiers without overburdening them or displacing vital supplies, said Deanna Tyler, an electronics engineer with the Army’s Communications-Electronics Research, Development and Engineering Center. “We have several programs in place where we are working with industry and academia to achieve that goal.”
Those relationships were on display here at Power Sources, an annual exhibition hosted by CERDEC. It is the front line of the ongoing struggle to lessen the logistical and physical burden of battlefield energy. An international assortment of engineers and university professors gathered to share with Army officials their efforts at tackling the issue. Ultralife was one of more than 50 companies represented that make batteries for everything from tactical radios to missile-guidance systems. But many were focused on finding lightweight, efficient ways to meet the exploding energy demands of individual troops.
“As [commercial-off-the-shelf] equipment has become more involved and more of that type of technology is integrated, each system has added a certain battery to the already 12 or 15 dictated military batteries,” Manna said. “Now you have a variety of specific batteries being pushed into the supply chain and even more COTS equipment being issued.”
In a typical 72-hour mission in Afghanistan, a soldier could carry up to 70 batteries to power his electronic equipment, according to the Army Research Laboratory. Battery weight can represent 20 percent of a soldier’s load. An infantry battalion spends more than $150,000 on batteries per year. It is estimated that the Army buys 200,000 custom-designed batteries per year at about $50 each for radio and communications equipment alone, according to the Army’s Research, Development and Engineering Command.
There are at least 14 types of batteries used to power radio and other communications equipment. Another 16 custom batteries are used in vehicles and to store power from generators.
A short list of devices for which soldiers need batteries includes smartphones and tablets, night vision equipment, optical sights, radios, laser telemetry devices, emergency location beacons, GPS, laser designators, thermal imagers, computers and memory backup.
As Defense Department engineers continue to attack the problem of soldier loads, which can affect troop mobility and health, industry insiders see a wide open market for new power sources and energy management technology.
“I think it’s definitely a growing market,” Manna said. “And there are a couple different flavors out there … areas in which industry can make strides.”
Ultralife mostly makes primary batteries — non-rechargeable, single-use cells — in dozens of forms and sizes for both commercial and defense applications. It also manufactures some of the new centralized power cells that the Army uses to power soldier gear. About the size and weight of a ceramic body armor plate, the UBBL35 is a form–fitting battery worn against a soldier’s body. The Army is using similar batteries in its Soldier Wearable Integrated Power System, which uses a single battery to run all electronic gear, whittling down the number and types of batteries that must be carried into combat.
It is a step toward paring down the logistics of battery supply, but is no silver bullet, Manna said.
“We’ve got some users who absolutely love plate batteries,” he said. “Some users hate centralized power. It’s great for reducing load, but if you lose your centralized power, you lose everything. Whereas if you’ve got individual batteries for each device, your night vision goggles might run out of power, but your radio still works.”
Much of the research into battery technology, including the Army’s own efforts, has been aimed at increasing energy density and reducing size and weight. But basic chemistry limits how dense batteries can get. At 5,200 watt-hours per kilogram, lithium-air batteries are as dense as current technology will allow.
“Lithium-air is the highest energy density battery that one can develop,” said K.M. Abraham, a research professor at Northeastern University’s Center for Renewable Energy Technologies, in Boston. “And, fortunately, it’s low cost because air is free.”
Air batteries use oxygen as a cathode instead of metal, reducing weight and size. But with batteries projected to become only 15 percent smaller, industry is looking for other avenues to reduce not just soldier load, but also the logistics of supplying troops with power.
“Energy density, size and weight are traditionally the metrics most people focus on in battery development,” said Alex Fay, business development manager for Quallion, a custom battery manufacturer based in Sylmar, Calif. “I don’t think we’re going to see any major increases in energy density without some drastic leap in technology.
“People expect that battery technology is going to progress like computers or other electronics, but that isn’t the case. They’ve gotten much smaller and energy dense, but those characteristics are at their height.”
Having largely switched from single-use lead-acid batteries to higher density lithium-ion and other types, the Defense Department is also weighing the respective advantages and shortcomings of both non-rechargeable, or primary batteries, and those that can be used multiple times.
Primary batteries can store more power than rechargeable batteries relative to weight, but must be disposed of and replaced. They also can be stored for long periods of time without losing charge, which makes them strategically valuable to the government. But that could be detrimental to industry, said Manna.
Non-rechargeable batteries can be prestaged without losing charge. Rechargeable batteries, after lengthy storage, would be dead and need to be recharged. They are better suited to training and other non-combat applications, Manna said.
While money currently is flowing to companies that make both, when the war in Afghanistan winds down, manufacturers of non-rechargeable batteries might see a loss in sales.
“Non-rechargeable batteries can be stored for 10 to 15 years and still be usable when taken off the shelf,” Manna said. “For that reason, they are targeted to conflict situations. Some manufacturers of primary batteries may not be able to cope because they can’t sit and wait around for an order every four or five years.”
The Defense Department also gains better return for its investment in rechargeable batteries, but they are initially more expensive and cannot store as much power as primary batteries. Though their storage capacity will improve incrementally, technology that will allow dramatic increases in energy density for rechargeable batteries likely won’t come within the next decade, Manna said.
“Some of the materials being worked on are themselves exotic, so not only do you have to scale the technology, you also have to scale up the mining and manufacturing process of the basic materials,” he said. “That’s going to take time.”
Yet, unforeseen technological breakthroughs can happen any time, as dozens of labs and universities are working on better and more efficient energy storage devices.
Researchers at Rice University recently developed a “spray-on” battery. Though still developmental, the technology takes liquid battery components and sprays them in layers onto any surface to create a power source. Rice researchers were able to light a set of LED bulbs from the surface of bathroom tiles and even a coffee mug using the sprays.
In the future, soldiers themselves, or the devices they carry, could become their own sources of power.
For now, Army officials are focused on adopting existing technologies, like rechargeable batteries. Heavily dependent on single-use cells, when it comes to multi-use power sources, “the U.S. Army seems to dwell in the Dark Ages,” said Isidor Buchmann, chief executive officer of Richmond, British Columbia-based Cadex Electronics.
One impediment to the proliferation of rechargeable batteries is the need for chargers — yet another device soldiers or units have to carry. But portable solar panels like the Rucksack Enhanced Portable Power System and super-efficient generators are making that challenge less onerous.
Soldiers also need to know how much energy they have remaining when using rechargeable batteries. Inaccurate readings or batteries without a charge indicator can cause soldiers problems, Buchmann said. “You have to have a fuel gauge and a power management system,” he said.
Traditional fuel gauges only read a percentage of the full battery charge. But as a rechargeable battery ages and naturally loses capacity, a 100 percent charge is actually only a fraction of the battery’s original storage capacity. Without accurate charge indicators, a soldier or Marine could go into combat with fully charged batteries that in fact hold a much smaller amount of juice.
Rechargeable batteries also have a limited life and most must be kept charged to avoid deterioration. At very high or very low charge levels, or extreme temperatures they can also become unstable and cause fires or explode.
In late 2008, a battery malfunction all but destroyed the Advanced SEAL Delivery System, a $272 million mini-sub designed to launch Navy special operators from an attack submarine close to a hostile coast. While recharging its lithium-ion fuel cells at Pearl Harbor, Hawaii, the 65-foot craft burst into flames. No one was injured, but the fire burned for six hours before it was extinguished.
The episode brought into stark relief the limitations of current battery technology. Making them smaller and more powerful can lighten the logistical load of supplying soldiers and their units with power in the field. But without mature technology, the quest for a lighter, more powerful battery could yield dangerous results, industry and engineering experts said.
“The problem is, when you’ve got enough batteries to move a sub, you’ve got a lot of power and a lot of stored energy,” Fay said. “But the technology that goes into rechargeable batteries now has progressed to the point where that kind of catastrophic failure could be avoided.”
Quallion’s Zero Volt technology seeks to alleviate such safety and logistics issues. Built into its military batteries, it allows a lithium-ion cell to be discharged all the way to zero whereas similar batteries typically operate between 90 percent and 20 percent. The company has also developed cells that can operate at negative 40 degrees Celsius, eliminating the need for heaters.
“If you can discharge batteries all the way to zero volts for transportation or storage, you lower the risk of fires or catastrophic damage to cells and you don’t risk blowing up a cargo airplane or the cargo hold of a ship,” Fay said. “You also don’t have to worry about the expense of equipment, personnel and facilities for maintenance charging because the inert cell won’t naturally decay over time.”
For troops carrying dozens of charged batteries into extreme combat situations, similar technologies offer an added level of protection and take pounds off their backs. Whittling down battery weight will allow U.S. troops to retain their technological advantage and replace spare power sources with other necessities — food, water and ammunition.