When U.S. soldiers first arrived in Afghanistan over a decade ago, they were carrying 3-pound, brick-shaped batteries originally designed for battery boxes and non-portable devices.
Multiply that 3-pound battery by the number of devices they had, plus a couple spares for each, and a soldier was typically carrying upwards of 20 pounds in batteries alone.
Engineers at CERDEC’s Command, Power and Integration directorate recognized that problem and began work to lighten the soldier’s load through more efficient power sources. Fewer batteries meant a soldier could carry something more crucial to survival like additional food, water or ammunition.
Fewer batteries also meant shedding pounds from the already over-loaded weight soldiers carried on a mission.
“The battery, at that point, had not been designed or optimized for wearable applications. As we adapted more toward wearable electronics, we had to come up with a design [for a battery] that allowed us to support what the soldier was wearing,” explained Chris Hurley, an electronics engineer who leads CERDEC’s battery development team.
CERDEC CP&I engineers, who have developed soldier power solutions for the Army for more than three decades, met the small unit’s demand for an integrated power source through the Soldier Wearable Integrated Power Equipment System, known as SWIPES, and the conformal battery.
SWIPES, recognized as one of the Army’s Greatest Inventions of 2010, integrated the charging of electronics carried by the soldier into the tactical vest; each device has a specific pocket with an associated power cord, connecting it to one central power source, simplifying the process of powering electronics and drastically reducing the number of batteries a soldier had to carry.
“SWIPES allowed a soldier to focus on the mission, rather than how often he needed to swap batteries and remembering which battery went with which device. It lightened both the physical and mental load on the soldier,” said Mike Brundage, CERDEC CP&I Power Sources branch chief.
“And logistically, to the Army as a whole, it meant less money spent on disposable batteries, less waste, and fewer convoys bringing in supplies – which were often targets for attack.”
The current conformal battery, at just over 2 pounds and lasting up to 24 hours, serves as the main power source for PEO Soldier’s Nett Warrior, a handheld situational awareness system. Initially developed by CERDEC in 2008, the conformal battery provides a flatter, flexible alternative to the traditional brick-shaped battery by conforming to the soldier’s body and top charging any soldier-wearable electronics.
CERDEC engineers are continuously working to extend the life of the conformal battery in order to last the duration of a small unit’s typical 72 hour mission. Since 2008, there have been four updates to the battery, each improving on its size, weight and power capacity.
The success of both SWIPES and the conformal battery changed how a dismounted soldier and the small unit carried power during a mission and has fueled subsequent soldier power development efforts within the Army.
“We have the conformal battery now, and moving forward, as always, we try to take the power sources that we have and make them smaller, lighter, more energy-dense and more powerful,” said Hurley.
For the next generation conformal battery, Hurley and other engineers at CERDEC are also looking to integrate ballistic protection for the soldier into the battery. Currently, the battery is designed to be worn in front of the soldier’s ballistic plate and must be disposed of if it is punctured.
“It would provide ballistic protection to a certain level and also function as the soldier’s main power source,” Hurley said. “The goal is to have the battery function at 80 or 90 percent if punctured – you don’t want the battery to be struck and you lose your entire power source – while still adhering to soldier protective requirements.”
Providing ballistic protection through the conformal battery makes the device multifunctional, reducing the need for two separate pieces of equipment and thus the overall weight and number of devices a soldier must carry.
“As SWIPES tied all the soldier-borne equipment to one power source, we’re looking to do something similar where instead of cables and wires, we’d do it wirelessly, eliminating the bulk of power cables and further reducing the load on the soldier,” Hurley said.
Current wireless power charging and transfer technologies are not nearly efficient enough for soldier use, but with research and development in this area, there is evidence that significant improvements are possible.
In lab tests, researchers find only 40-70 percent efficiency of wireless power transfer, Hurley said.
“If we can develop our power sources to have greater energy, it might help compensate with the inefficiencies of wireless power transfer, but until we see wireless power efficiency up near 80-90 percent, we won’t see it in a soldier configuration.”
Hurley noted the most near-term application of wireless power, in the form of vehicle to soldier power. As a soldier sits in a vehicle, wireless charging components integrated into a seat would top-charge the conformal battery or other central power source in the soldier’s vest. Other wireless charging possibilities include a table or closet that would charge the tactical vest while not in use.
Even with these applications, however, CERDEC engineers note limitations like the physical alignment of the battery and charging device, which plays a significant role in energy transfer. Any misalignment can result in energy loss and inefficient charging, Hurley said.
E-textile technology is another viable power transfer option, reducing the soldier’s load and the complexity of soldier systems, but without the power loss tied to wireless charging.
E-textiles are fabrics with electronic components seamlessly embedded within the textile.
“If we don’t ever get to a wireless construct for soldier power, we could make the vest itself out of e-textiles. The wires are basically the size of the thread you’re weaving the vest out of,” Brundage said.
“At the end of the day, it makes it a lighter weight piece of equipment just by the fact that you don’t have the additional weight of power cables. You can just substitute thread in the vest for an e-textile.”
The limiting factor for any potential soldier power source is often the ability to provide enough power for a small unit’s typical three or four day mission without the need for resupply. Novel power technologies, including energy harvesting and soldier-borne solar power are currently being researched in order to meet that mission requirement.
Soldiers spend a lot of time and energy walking, and through energy harvesting that energy could be converted into real, usable power to fuel electronics.
Energy harvesting technologies use small kinetic devices that oscillate back and forth when a soldier moves to produce small amounts of energy that can trickle-charge the soldier’s main power source and extend the life of electronic devices during a mission, Hurley said.
“One device we’re looking at is a backpack. If you incorporate the energy harvesting technology into the rucksack design, you don’t increase the weight you’re carrying and you’ve created a multi-functional device. Its carrying your load and generating energy for you,” said Brundage.
Research is also looking at ways to incorporate wearable solar panels into the soldier uniform, whether it is on top of the soldier’s helmet, on the rucksack or in another location. The solar panels would also trickle charge the soldier’s main power source.
As the Army transitions to a faster, more mobile fighting force, the number of wearable devices including smartphones, GPS devices, radios and other electronics carried by the soldier continues to grow – and so does the soldier’s demand for tactical power technologies.
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