source: ECN article
What are some of the driving forces in military system design that will necessitate improvements in battery technology? The design inspiration counts with capacitors to extend its operational life or harvest energy.
By Sol Jacobs, VP and General Manager, Tadiran Batteries
The modern battlefield is becoming more technologically advanced, incorporating the use of remote wireless devices and communications. The growing list of applications includes ground sensors, wireless mesh networks, miniature UAVs, smart munitions, and devices that monitor military equipment and weapons systems, to name a few.
These applications typically exceed the performance capabilities of consumer alkaline and primary lithium batteries that don’t adequately support product miniaturization, suffer from short lifespans, and offer narrow temperature ranges. For example, wireless devices that draw low average daily current are typically better suited for industrial grade lithium thionyl chloride (LiSOCl2) batteries that deliver high energy density and capacity to support product miniaturization, a low annual self-discharge rate to extend operating life, extended temperature range, and high pulses capabilities to support two-way wireless communications.
Similarly, industrial grade rechargeable lithium-ion (Li-ion) batteries can outperform consumer grade Li-ion batteries in the battlefield by delivering an extended operating life, high pulse capabilities, and extended temperature range.
Applications designed for one-time use that draw high continuous current, such as smart munitions, were once powered by spin activated and reserve/thermal batteries: legacy technologies that are overly bulky, expensive, and cannot be activated unless exhausting all their energy, thus eliminating the opportunity to periodic test for system readiness. To address this problem, long-life lithium metal oxide batteries were developed that provide an economical COTS solution, featuring very high capacity and energy density to support miniaturization, up to 20-year shelf life, and ruggedized construction to survive shock, vibration, high spin rates and g-forces. Lithium metal oxide batteries are also being utilized for miniaturized emergency power so a crippled UAV can glide to a safe landing.
As remote wireless military applications continue to evolve, intelligent battery-powered solutions will be required to achieve maximized performance and value, while becoming increasingly miniaturized.
By Zachary Sharpell, CEO, Sharpell Technologies
Increases in power, complexity, along with size and weight reduction are at the forefront of newly developed military systems. Due to this innovation in military devices, not only must battery cells improve, but packaging in which multiple cells are placed, must be redesigned from the most basic level.
With increased power consumption from new technology in military systems, battery technology will need an increase in energy density—the power stored per weight of the battery. Keeping soldiers mobile and agile is a vital part of the winning strategy—the less weight a soldier carries, the quicker and further they can run. In terms of agility, battery technology must shrink—this doesn’t mean a decrease in capacity, but size. Smaller form factors for batteries equal small space requirements, and coincides with the decreasing size of new military technology.
The number of devices present on soldiers has been increasing over the past two decades, and will continue to increase as more systems are developed. While these systems are designed in part to protect soldiers, the batteries powering such systems are an opposition to protection. Li-ion batteries are known for their instability and flammability upon penetration (i.e., hit by a bullet). It’s necessary that a safer battery chemistry be used for upcoming military systems. The goal of missions is to succeed, and that includes ensuring the safety of our soldiers.
With the advent of augmented reality, intelligent scopes, and even new versions of radio, it’s important they are powered by the best batteries available. The last thing we want is our troops to go into the fight with their state-of-the-art technology dead due to an empty battery.
By Colin Leath, Field Applications Engineer, AVX Corporation
There is a continuous drive to improve battery system performance in military electronics, along with making them more lightweight and reliable. Passive components in these systems, like capacitors, can be used in parallel or addition to batteries, increasing reliability of the overall system, and extending the battery’s lifetime without adding undue amounts of weight or volume.
A supercapacitor can often be placed in parallel with a battery to increase its lifespan, since electrical loads in systems like military satellite phones aren’t always constant. In this case, an initial high burst of power may be needed to sync with the satellite, but the system would then drop back down to low power once the link was established. Without a supercapacitor, the system’s battery would supply the power needed during those spikes. The employment of a parallel supercapacitor prevents the battery from having to exclusively handle such stresses, significantly reducing the battery’s wear and tear, while extending the system’s lifetime and continuing to satisfy the overall design’s size, weight, and cost constraints.
Non-volatile static random-access memory (nvSRAM) applications are another focal point for military battery improvements. A relatively small capacitor can be placed in the circuit for holdup operations, giving the system sufficient time to store information into non-RAM, should the voltage going to Vcc drop below the minimum amount required. In this case, use of such a capacitor (and specifically a high-reliability one such as an MnO2 device) significantly increases the dependability of an already reliable system, while still satisfying its size, weight, and cost demands.
Additionally, energy harvesting circuits are already replacing batteries in certain applications, and will undoubtedly make their way into military equipment to satisfy size and weight demands in applications like soldier-worn systems.
By Scott Ferguson, Xcelion 6T Global Product Manager, Saft
Most heavy-duty military vehicles were originally fitted with batteries that supplied just enough power for engine starts and ancillary equipment operation. Their vintage electronic systems were designed to handle low-level starting, lighting, and ignition (SLI) loads. Today’s vehicles are equipped with sophisticated electronics and digital packages, often featuring an array of mission-critical sensors, jammers, communication, and control systems that strain traditional lead-acid batteries. The power and energy demands of modern vehicles require advanced chemistry batteries, enabling the systems to start up reliably and perform functions like extended silent watch missions.
Li-ion battery technology emerged as a solution that provides more power, reduced life cycle, and total cost of ownership in military vehicle applications. Typically, a military vehicle is outfitted with two, 24 V lead-acid batteries weighing approximately 88 pounds each and capable of performing a few hundred discharge cycles. Depending on conditions and use, lead-acid batteries could last about one year performing SLI functions and silent watch missions. Available capacity of traditional lead-acid batteries is dramatically affected by faster charge and discharge rates, and limited temperature ranges. By comparison, the increased energy density of Li-ion batteries provides consistent power capacity over various discharge rates and temperatures.
Li-ion technology has several advantages over lead-acid. One Li-ion 6T battery replaces two lead-acid batteries with a 74 percent reduction in weight, 50 percent reduction in volume, increased output, faster recharge capability, and enhanced cold temperature performance. They can perform significantly more depth of discharge cycles, outlasting lead-acid by five years.
By David Moore, Sales Manager for Defense/Aerospace, Avnet
As the U.S. military continues to increase battlefield advantage through mobile sophisticated electronic equipment, more time and resources are being invested into advanced battery technologies, which will provide continuous rechargeable power on the move, mitigate communication breakdown, and prevent data loss. Specifically, these technologies help enhance three components of the military: soldier, vehicle/UAV, and weaponry.
Depending on the mission, today’s soldier carries 15 to 25 pounds of stored mobile power to utilize next-generation communications, advanced sensors, tactical computers, and wireless networking for field operations. Consequently, the Department of Defense (DoD) continues to spend considerable R&D funds on new battery designs to reduce size and weight, while maintaining uninterrupted power to the soldier’s backpack.
Enhanced battery technologies are also essential to the effective operation of land, air, and sea vehicles. Land vehicles can’t support longer duration silent watch activities if patrol idling is required to offset insufficient energy storage that fuels essential on-board electronic subsystems. Unfailing electric power enables the hybrid land vehicle to move more quietly, avoiding additional sound that might otherwise alert the enemy. Smaller Unmanned Aerial Systems (UAS) are increasingly utilizing exclusive battery power to run the motor, controls, data link, and imaging equipment for missions lasting nearly two hours. Larger UAS continue migration towards hybrid energy where batteries become the primary power propulsion source. In both platforms, new military designs are further challenging size and weight of the battery pack for uninhibited power.
Newly developed battery systems are also improving the effectiveness of single use weapon applications. Shrinking guidance systems allow precise mortar strikes and tight parameter bursting artillery projectiles, effectively lowering costs to engage the enemy within an acceptable collateral damage window. Previously, this was only possible from the more expensive missile families.
To ensure our military’s continued modernization, there will need to be further development of enhanced battery power. The DoD knows this and is working to assist the market in new battery design, as numerous advancements are already impacting military electronic capability. This technology will continue to show great promise in the coming years.
By Mike Stein, Director of Military & Defense Product & Program Management, Inventus Power
As demand for portable power grows, the U.S. military is looking for cutting edge technologies to both supply energy and lighten the soldier’s load, necessitating specific improvements in battery technology. Over the last 15 years, the power consumption of warfighters conducting operations has climbed sharply. Troops often carry a variety of gear, requiring energy such as radios, GPS, computers, smartphones, night vision goggles, infrared sights, and counter-IED equipment. The extra weight soldiers must carry is a concern, as troops often haul around 100 pounds of gear on them when they’re out on patrol. An infantry platoon currently carries about 700 pounds of batteries (17 pounds per soldier) for a 72-hour mission.
The DoD has determined this current trend is unsustainable, and compounded by too many battery types with differing interfaces. The need for a centralized, wearable power solution is a priority. Small-unit leaders are the base, on which the Army’s networked system is built. With more capabilities comes the need for more power. That need can’t result in placing more weight onto our soldiers.
By Steven Lassen, Product & Applications Manager, LEMO
When selecting electrical connectors for an application, where do you begin? There are a multitude of choices, so how do you find the right match? First, know your requirements. A connector company can better assist you to narrow down choices. If for a rugged application, define the environment. Does it need to be vacuum-tight or just water-resistant? Push-pull, bayonet, ratchet-coupling, or quick-release? In normal operation, will the connector be exposed to sand, mud, salt water, and if so does it need to merely remain protected in the mated condition, or will it be disconnected and need to be cleaned?
Connector companies try to create families of products, which meet certain rugged aspects. For instance, a rugged connector may be a more durable metal or plastic body, which can replace an inexpensive USB or HDMI connector in an indoor application, where no water resistance is needed. When possible, the same internal electrical inserts can be designed to fit into ruggedized housings ranging from IP50 to IP69K, capitalizing on economies of scale using a modular approach.
In military/aerospace applications, a rugged connector designed for land use may not be the right choice for an airborne design. Housing materials like brass and stainless steel are heavier compared to aluminum or titanium. With a modular approach connector, companies can offer similar electrical characteristics with many different housing materials and treatments. In one recent airborne application, a copper-based cable wound up being too heavy, so the connector and cable were changed to a fiber optic design.
When selecting a connector, remember the component is only as good as the attaching cable. Retention and sealing system is equally important. If a quick-release connector is used, you want the connector to release before the cable is yanked. You might consider whether the standard cable retention system offered will suffice, or if the connector should have an overmold or hot-melt heat shrink boot.
Another consideration is operator ergonomics. You may have designed the perfect connector for all electrical and environmental requirements, but if the operator needs to wear gloves in a sub-zero or hazardous materials location, the connector may be too small to handle.
Know your end user, as some may only be familiar with ratchet-coupling style connectors. Introducing a push-pull in this environment could lead to damage if the user attempts to ‘get a bigger hammer’ and apply a high twisting force to a push-pull style connector. The operation must be intuitive to its application.
Consider a hybrid where you combine two or more connectors into a single unit. Both power and signal cables can be combined into a single connector, making it easier and more fool-proof.