The risk of human casualties associated with fuel convoys, combined with the long-term cost issues of unreliable technologies, has the military exploring greener, more sustainable options with the goal of increasing energy efficiencies, lowering fuel consumption, and lessening the risk of lost lives. Advanced battery technology continues to be validated as a viable solution to lowering fuel demands. For example, today’s advanced energy storage systems can store energy from portable solar arrays to power essential electronic systems at forward operating bases (FOBs) — instead of using a vehicle’s idling engine power or diesel generators — significantly reducing fuel consumption, costs, and risk.

There is a growing trend toward rechargeable batteries in the military, especially as they become more rugged, safer, and have a longer operating life. Primary battery systems will always have a home, but rechargeables are being used in more and more applications in tactical operations and command posts. Lithium-ion batteries are well suited for these applications with superior cycle life and with the wide operating temperature capability required in rugged operations, especially when there is less availability to charging stations. Moreover, lithium-ion batteries are more likely to be reused after missions due to their enhanced reliability. Specific goals for DOD include Silent Watch, microgrid applications, renewable energy applications and, potentially, underwater vehicles. The ultimate scenario is to provide the building- block battery module that can be used independently or in multiples to serve these different applications.

Optimum Performance

Until now, the military used generators or lead-acid batteries to power their communication systems. While lead-acid batteries are ubiquitous due to their lower cost, their popularity is being diminished by lithium-ion battery chemistries for demanding, energy-dense storage applications. Lithium-ion batteries offer many advantages as they are much better at moving large amounts of energy into the battery without overheating, and they offer much higher round-trip efficiency. Top-off charging of the fully depleted batteries by stationary chargers can be accomplished in just two or three hours with lithium, versus six to eight hours to charge lead-acid batteries.

Lithium-based large-format cells on the market today are proving themselves in interesting pilot programs as they offer up to 70 times the capacity of prior generation cylindrical lithium cells and have much lower system integration costs when aggregated into large battery packs. Having an order of magnitude reduction in the number of cells also enables a reduced number of battery interconnections, further improving reliability of the battery pack and providing for a much higher value proposition. Individual cell monitoring with the use of Battery Management Systems (BMS) is a key to success with these systems.

Energy Storage for Military Applications

Large format Li-ion prismatic battery compared to a cylindrical lithium cell.
The Marine Corps and the Army have expressed interest in using lithium iron phosphate batteries in microgrid applications and for FOB camps. Typically in the past, the military has used generators and/or lead-acid batteries to power these camps, but now decision-makers are looking to lithium as a more efficient and lighter-weight solution. Combining renewable energy together with lithium batteries, and even with a generator, can optimize the use of all three — getting the energy needed for the soldiers in the field. The reduction of fuel consumption is substantial, which is a primary driver in cultivating these technologies. Fewer fuel convoys means less risk and greater savings.

Forward operating missions can generate all their power independently — off the grid — with reduced use of generators. In order for the military to cut down on the use of generators, it needs to hybridize or supplement the generator with an energy-dense battery and a workable solar array. Even when the generator needs to be used, at full efficiency, power can be put back into the battery. Plus, the battery can be continuously charged from the solar cells. The generator won’t be completely eliminated, but it can be hybridized by using inverters to charge the battery to continuously run, creating a generator with much greater efficiency using fuel for shorter periods of time. That’s a huge advancement, and lithium-ion batteries are a big part of that reduction.

Weight is a key consideration in selecting battery technologies as well as energy density — being able to provide the most amount of energy for the least amount of weight. Lithium-ion battery technology fits both requirements and can do so safely. Within the military’s comprehensive testing requirement, there’s a significant amount of safety testing for batteries that involves having live ammunition fire through the battery, water submersion, and fire. Lithium iron phosphate chemistries have performed admirably.

Real-World Example

In recognizing the growing trend of combining renewable sources with energy storage for microgrids in the field, contractor HDT Global (HDT) is working with the U.S. Marine Corps to supply energy storage systems for the Ground Renewable Expeditionary ENergy System (GREENS). The network is a portable hybrid photovoltaic/battery power system that provides renewable energy for forward- deployed units that have a limited power supply. According to the Office of Naval Research, “GREENS will reduce the logistics burden for providing power to remote locations. It will provide AC and DC power needs to charge typical communication, targeting, and computing devices. GREENS will reduce the fuel use otherwise needed for typical generators, and will lessen the need for fuel resupply, reducing the associated threats to vehicle convoys in Afghanistan and Iraq.”

GREENS consists of networkable and vastly scalable 1600 watt solar arrays and rechargeable large-format lithium-ion batteries that provide continuous electricity for Marines in remote locations and forward operating bases. The lithium-ion component of GREENS enables high efficiency storage of solar energy in a package substantially lighter than a lead-acid battery solution. The lithium-ion battery exhibits dramatically improved durability when operating at high ambient temperatures — which severely shorten the lifetime of typical lead-acid batteries — and allows for near 100 percent utilization of the nameplate battery capacity.

Expanded Duties

Lithium-ion batteries enable longer equipment runtimes when tanks, Humvees, and other military vehicles are conducting reconnaissance activities.
Beyond renewable energy capture, lithium-ion battery energy storage has found other uses in military applications, including Silent Watch. The battery chemistry enables longer runtimes when Humvees, Stryker tanks, and other military vehicles conduct reconnaissance activities, allowing soldiers to concentrate on the task at hand, silently. By running electronic surveillance and communications equipment from lithium batteries as opposed to the vehicle’s battery, military forces can eliminate heat signature and audible signature for extended amounts of time, possibly up to eight to ten hours. Silent Watch requires battery systems to be ruggedized and able to withstand wide temperature

variances. Moreover, lithium-ion batteries were showcased this year at The Experimental Forward Operating Base (ExFOB) event at the Marine Corps Air Ground Combat Center, as part of a system that provides up to 75 percent fuel consumption reduction for Humvees. To improve fuel and energy efficiencies, save costs, and simplify logistics, the vehicle power unit — which can be installed in less than 30 minutes — operates automatically (no operator intervention needed) and independently of a vehicle’s battery system, utilizing an auxiliary alternator and up to four 1.5kWh or 4.1kWh batteries featuring UN certified large-format lithium- iron phosphate rechargeable cells.

Looking Forward

As the military continues to pursue advanced battery options, microgrids and stealth activities can be transformed accordingly. And, while there are different storage solutions, large-format lithium- ion cells are leading the way in many high-energy applications because of their near 100 percent efficiency, scalability, and versatility. Today’s ad - vances in battery technology, combined with superior methods of monitoring and managing batteries, take energy storage to a higher and more cost-effective level of integration for many military applications.

This article was written by David McShane, Executive Vice President of Business Development and Sales, International Battery (Allentown, PA). For more information, visit .