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Reprinted from Battery Power Products & Technology, July 2001By Mark Warner Ultralife Batteries, Inc. High-tech, portable equipment has made its way into defense inventories, which has increased the need for safe, high performance batteries greater than ever before. This is true despite the various cutbacks in military budgets over the last few years. The performance requirements for portable power sources are varied however. For the myriad of equipment the requirements for battery power cover a wide range of environmental and electrical conditions for both operation and storage. In normal "commercial" markets numerous types of battery chemistries and designs can be tailored to suite a given application. However, for military applications, the demands placed upon the battery system require that the battery perform to extremes of temperature and mechanical abuse. Today's military equipment is required to operate in dry desert heat, humid tropical jungles and in cold arctic conditions, as well as submerged in water or dropped from planes and helicopters.  Increasingly powerful and sophisticated military equipment and their power sources must function reliably under all these conditions. High rate capability, light weight, more power per unit volume, no voltage delay even after long storage periods, operation in a wide range of temperatures, long storage life and safety are just a few of the challenges that the batteries for these applications must face. Applications include GPS: receivers, remote surveillance, field computing, command and control devices, smart missiles, satellites, chemical agent monitors and especially communications devices just to name a few. All of them have the demanding need for lighter, more powerful and safer batteries.Over the last twenty years the battery needs for many of these applications have been met with lithium sulfur dioxide (Li/SO2) primary (non-rechargeable) battery technology. Though this technology has served the military well and performs at the wide temperature ranges currently required, it has not been without some problems and some challenges, including safety, weight, capacity and cost. Safety: Battery safety is a top concern to military organizations. Most of the cells in current battery systems used by the military for portable devices utilize pressurized cylindrical cans. Though many of these are rectangular batteries, the cells inside are cylindrical cans, which can pose a hazard if abused or punctured. The latter being of special concern to the soldier, because the last thing the soldier wants to happen in a firefight is to have a battery explode because it was hit by a bullet or a piece of shrapnel. One of the things that battery manufacturers are working on to make batteries safer is to develop nonpressurized cells. An example of a non-pressurized cell is the development of a high energydensity lithium-manganese dioxide (Li/MnO2) pouch cell. This cell is constructed with a solid lithium metal anode, solid MnO2 cathode and liquid electrolyte. These active electrochemical materials are packaged in a flexible, laminated aluminized bag configuration (pouch). A challenge with pouch technology is mastering a sealing process to prevent cell leakage. Though this is not necessarily a safety concern, it does affect the performance. Another challenge is performing at the extremes of the military specified temperature ranges. To address these challenges battery manufacturers, with assistance from the US Army, are researching advanced packaging materials and sealing techniques as well as unique electrolyte formulations and processing for both rechargeable and primary batteries. Hazardous gasses venting from a battery also present a serious safety issue. The US Army has replaced the Li/SO2 cells in most electro-optical type devices, such as night-vision goggles, with Li/MnO2 cells. This was done to avoid the possibility of the battery venting noxious sulfur dioxide (SO2) gas in the face of the device user in the event of a short circuit or overheating condition. Another improvement in safety being implemented into military batteries is a fusible separator between the anode and cathode of the cell. This separator will shut down the battery when overheated either due to short circuit or over-current conditions. Weight: The weight of the battery is critical, especially to the person who must carry it around all day. When we hear reports of soldiers cutting handles off toothbrushes or not carrying sugar for coffee because of the extra weight, it becomes obvious that every ounce counts. The implementation of lithium batteries significantly reduces the weight when compared to the battery technologies preceding it, i.e. alkaline and carbon-zinc. Now, the challenge for battery manufacturers is to take the next step in reducing the weight of their batteries. One approach is to increase the energy density in existing battery compartments. If one battery will do the job of two, that is one less to carry. The development of longer life, lighter and thinner batteries are some of the challenges facing battery manufacturers in programs such as the Land Warrior system. The battery for this system must meet paratrooper requirements whereby it must weight two pounds or less and be no thicker than 1.6 inches (40.6 mm). Yet it must supply enough power to last at least ten hours to supply power to a computer, communications devices and vision enhancement devices, sometimes all at the same time. These types of requirements are challenges that military battery manufacturers face daily. Add to this the demanding qualification and testing criteria that is necessary to supply batteries to the military and you can understand why most large commercial battery manufacturers do not choose to supply batteries to that market. Some innovative ideas are currently being tested for Land Warrior type applications, such as integrating rechargeable cells into the clothing of the soldier or into ammunition belts. This requires flat cells such as those used in lithium-ion polymer rechargeable batteries.  More Capacity: As more portable electronic devices are fielded the demand for longer battery life increases. Designers regularly ask battery manufacturers to make batteries lighter, thinner and to last longer. Two of the ways these challenges are being addressed is by moving towards the Li/MnO2 system, which has higher energy density than Li/SO2, and by utilizing the entire battery cavity. An example of this is the US Army's BA-5590/U battery. This is the most widely used battery in the Defense Department inventory. It is used in the PRC-119 SINCGARS communications radio. The current Li/SO2 battery has a capacity of approximately 7.5 Amp hours. A Li/MnO2 cylindrical cell version of this battery has a capacity of approximately 10 Ah and the capacity of a Li/MnO2 pouch version, which utilizes the full volume of the battery case, can be as high as 12 Ah. That’s a 60 percent increase in capacity in the same amount of space! Cost: Not only do battery manufacturers need to make batteries safer, lighter, smaller, more powerful and able to be stored for years, they must now make these batteries more cost effective. This is another significant challenge, especially as the electronic devices become "smart" the need for a smarter battery is on the rise. Examples of this are the growing need for State Of Charge Indicators and battery to device "Smart Bus" type communications. Though these smart electronics add to the cost, the value of the battery is higher and the life cycle cost is improved. This is because with state of charge indicators and smart communications the user knows how much energy is left in the battery and it can be used completely. Another contributing factor to reducing battery cost is volume. As more US military equipment is distributed to other countries the need for batteries increases. As the demand and quantities increase the price decreases. Another way to reduce the cost of military batteries is to increase production quantities through usage in commercial applications that require long storage capabilities, high power on demand and the ability to operate at wide temperature ranges. Applications such as sonobuoys, emergency location transmitters and heart defibrillators are a few that require this type of battery. Military organizations around the world have begun to realize the benefits and cost savings of using rechargeable technology. This technology is especially desired in training. In the past, however, rechargeable batteries have had low energy density when compared to primary technology, and they were heavy. Battery manufacturers have made considerable improvements in both energy density and weight in the last few years by the development and improvement of lithium-ion and polymer rechargeable technologies. As these technologies continue to improve, they may be considered for missions other than training. Manufacturing batteries for the military has its challenges: rigorous operation conditions, delivery deadlines, continuous quality inspections and pressure to reduce cost. However, historically the military has driven cutting-edge technology. Today's computer chips, image enhancing software and hardware, miniaturization of electronics and high strength materials have all been driven by military applications. The same can be said for today's battery technology. Batteries being used by the military today will be found in civilian cars, hand-held electronic devices and portable electronics equipment tomorrow. Safety, high capacity, light weight, cost effectiveness and high performance are just a few of the requirements placed upon battery manufacturers by the military. When lives depend on the device and the device depends on battery power, they will not settle for second best. These types of performance requirements exist in the commercial sector as well. Lives depend on battery powered devices in applications such as automotive telematics, portable defibrillators, survival radios, marine and aircraft emergency locating beacons and smoke alarms. When your life depends on it, reliable battery performance is critical. Mark Warner, Ultralife’s Marketing Manager for Government Programs, has an electrical engineering background and worked in the electronics and barcode scanner industry for sixteen years prior to joining Ultralife in 1998 as a Sales Applications Engineer. Ultralife's lithium-manganese dioxide (Li/MnO2) technology provides portable power in a high energydensity battery that experiences no voltage delay after prolonged periods of storage; yet, is lightweight, safer, environmentally friendly and utilizes a non-corrosive electrolyte. That is why national defense agencies of the United States, United Kingdom and NATO forces specify this technology in applications where safe, reliable portable power is needed, even after prolonged storage and in applications requiring a lightweight, powerful battery without the inherent dangers of Li/SO2 technology. Ultralife is committed to total quality in our worldclass manufacturing facilities in Newark, NY and Abingdon, UK, both of which are ISO9001 certified. In 2000 Ultralife was awarded the prestigious Best Value Bronze Medallist award by the US Defense Supply Center in Richmond, VA. |
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