Today the choice of power supplies, power converters and batteries can rank as a make or break decision in embedded military computer systems. With more and more computing stuffed into smaller spaces, power has direct implications on the size, cooling and mobility of a system. Military programs—land, sea and air—are all in some way dependent on technology trends affecting military batteries, DC/DC converters, power supply module bricks and slot-card power supplies.

Starting on the battery side, vendors continue to advance their power densities both with new chemistry innovations and by refining their existing processes. Lithium-ion for its part remains the favorite choice for today’s computing-based systems. Along those lines, Saft’s advanced Li-ion energy storage system will support the technology development phase of the U.S. Army’s Ground Combat Vehicle (GCV) program. As a member of the BAE Systems GCV team, which has been awarded a contract for the initial phase of the program, Saft has entered into an agreement to design and build ultra-high-power batteries for the vehicle’s hybrid electric drive system.

Battery System for the GCV

Comprised of ultra-high-power, high-voltage VL 5U cells, the Li-ion energy storage system will support the vehicle’s hybrid electric drive system when it is not relying on traditional carbon-based fuels; an example of an operation that would utilize this technology would be silent watch missions. In addition, the system will provide thermal management and act as a high-power traction motor battery. The technology development phase of the GCV program is a 24-month program aimed at completing preliminary design reviews in order to begin building prototype systems for the engineering and manufacturing development phase of the program. Saft’s contribution of an ultra-high-power energy storage system will allow BAE Systems to prove the advantages of Li-ion technology in this hybrid electric vehicle.

Another direction of battery innovation is the drive to power-dense portable solutions. Feeding that need, Contour Energy Systems earlier this year signed a technology development agreement with In-Q-Tel, a strategic investment firm that identifies innovative technology solutions to support the missions of the U.S. Intelligence Community. This strategic partnership between Contour Energy Systems and IQT will advance portable power solutions for various terrestrial and emerging applications.

IQT’s strategic investment in Contour Energy Systems provides funding for new battery developments that are directly applicable to current application power requirements at many U.S. government agencies. Contour’s advanced lithium/carbon fluoride battery technology has a gravimetric energy density twice that of either sulfur dioxide or manganese dioxide. This is significant for military applications because by doubling the energy density, the weight of a battery pack needed for a mission of a given duration can be cut in half, or the same size and weight in battery packs could double the mission’s duration.

An example of AA-sized battery technology aimed directly at military/aerospace is Tadiran’s high-voltage/high-rate AA-sized lithium battery, the TLM 1550. Packing 2Wh of energy at 4.0 volts into an AA-size cell, the TLM 1550 is specifically designed for applications requiring high power, long life and extended storage, such as military/aerospace systems. The AA-sized TLM 1550 features an open circuit voltage of 4.0 volt, and the ability to handle pulses of up to 15A, with 5A maximum continuous load. The TLM offers very long life in extreme environmental conditions, including a self-discharge rate of less than 3% per year at room temperature, and a temperature range of (-40° to +85°C). Tadiran’s TLM 1550 battery is also extremely safe, as its solvents are non-toxic and non-pressurized and its anode material is less reactive than that found in other lithium cells. The battery has performed well in a variety of safety tests, including nail penetration, crush tests, high-temperature chambers, short circuit and charge tests.

Robust Power Convertor Solutions

Shifting to the power supply and power convertor side of the equation, power system vendors continue to step up with more efficient products, new partitioning strategies and increased ruggedization. Choosing power supplies and power conversion electronics can become make or break technical choices because power supplies and converters are critical enablers for meeting today’s rugged requirements.

Vendors like ATC Power Systems not only make military modules but offer entire power systems for the military programs. An example of ATC’s offerings is its new MIL Power PAC power supply (Figure 1). The unit provides an output power of 500W. Its output voltages (up to four) can be 3.3V, 5.0V, +12V, +/- 15V, or 28V. Output features include current limit / short circuit protection, droop compensation for ease of paralleling and precision clamp output overvoltage protection. It can be configured for output redundancy operation and all outputs can be independent (no minimum load required) and synchronized to a master clock. Efficiencies of over 75 percent are achieved with PFC and ORing diodes. For input voltage, the supply supports 103.5 VAC to 126 VAC at 160 Hz per MIL-STD-1399 and 108 VAC to 118 VAC at 1400 Hz per MIL-STD-704. 180 to 425 VDC is supported over single or 3 phase inputs. Military standards support includes MIL-STD-1399, MIL-STD-704 and MIL-STD-461.

The MIL Power PAC supply comes in three mechanical versions. The first is a VME 6U card slot supply in forced air-cooled version. The second is the same but with “D” style connectors on the input and output. The last type is a conduction-cooled version—no fins and thick baseplate—with “D” style connectors on the input and output. ATC can also customize for any application depending on customers’ requirements. ATC currently sells a similar type of (forced air-cooled) unit to the U.S. Navy that is used on submarines and aircraft carriers.

Cooling is an issue at high power dissipation levels. Targeting that issue, TDI Power offers its patent pending LiquaCore power management technology. It employs liquid cooling in a modular and scalable architecture. The technology uses a cold plate to wrap the electronics with cooling liquid in a sealed package that enables efficient management of waste heat at very high power densities. The cooling liquid employed is either water or a mixture of water and ethylene glycol (anti-freeze). As part of their power management technology, TDI Power has developed a DC/AC Inverter that boasts 95% efficiency and has an MTBF of more than 80,000 hours per MIL-HDBK 217. With a power density exceeding 33W/in3, TDI Power can easily create a modular solution for higher power needs. The inverter can also be used as a standalone single-phase inverter or as a single phase in a multiphase system. It is ideal for harsh environment vehicular applications.

Rugged Power Supplies

Rugged operation is a key differentiator for military power supplies. Last month Schaefer announced broadened capabilities for their Raptor Series (Figure 2) of military power supplies. The supplies are designed for harsh military applications such as shelters, armored vehicles, avionics, naval and open air applications. The Raptor’s output voltage range is now extended to provide DC outputs from 12 VDC to 52.5 VDC with power ratings from 1200W to 1800W. Parallel capability and other power levels are also available. Single and three-phase input ranges span from 88 VAC to 265 VAC or 125 VDC to 400 VDC. The series specifies high efficiency (85% nominal) and high power factor correction.

The series meets MIL-STD-810D for operating temperature conditions, vibration and shock, and also meets other critical MIL-STD-461 ratings for EMI, navy MIL-STD-1399 and aircraft electrical power MIL-STD-704D, and environmental test methods. A variety of optional protection features include CARC, dark out switches, alarm/controls, auto temperature derating, overvoltage protection and reverse polarity protection.

Navy UPS Solution

One area where battery and power supply technologies overlap is in the area of Uninterruptible Power Supplies. UPSs are critical for military systems where a power outage can disrupt a mission. Late last year, Acumentrics, working with Earl Industries, modified an existing Rugged-UPS to power a vertically mounted voice-data-video (VDV) network node for the Ford Class Aircraft Carrier (Figure 3). According to Acumentrics, while the company has fielded many shipboard UPS systems, the specifications for the VDV contract required significant modifications. After implementation of the adaptations, the newly designed unit was successfully tested and certified to MIL-STD-1399 and MIL-STD-461. Physically, it had to conform seamlessly to the overall system and into a shock mount enclosure. The battery also needed to be user replaceable from the vertical orientation when the enclosure was in the “rack out” position.

In terms of changing internal components, the inverter portion of the Rugged-UPS had to be integrated between the server and modem. This was accomplished through two alterations. First, the team developed a 1U battery pack that would mount in the vertical position. Next, they redesigned the chassis to eliminate the space of the existing battery compartment to save room and provide cabling and connectors to tie into the separate battery pack. Other features were added including multiple AC inputs for redundancy.

In another example of UPS technology innovation, Falcon Electric recently added a ruggedized wide temperature (-30° to 63°C) extended runtime battery bank option to its popular SSG and SSG-RP UPS products (Figure 4). The wide-temperature-rated batteries provide long back-up runtimes for protecting connected computers and instrumentation operating in harsh environments during a prolonged power outage. The new battery pack gives users over 10 times the battery runtime, compared to Falcon’s standard 2U extended battery pack option.

The new battery bank carries a UL listing when powering Falcon’s unique UL-listed SSG2.5KRP-1. UL is pending for the remaining models in the SSG and SSG-RP Series wide-temperature-rated UPS product line. The SSGB-1S40-5U 40AH battery bank is a rugged battery option that consists of eight deep cycle, valve regulated lead-acid, maintenance-free 40 amp hour batteries and two internal one amp chargers. The batteries and chargers are housed in a sleek rackmount enclosure, which takes only 5U (8.75 inches) of vertical rack space. The battery banks may be interconnected or “daisy chained” to provide exceptionally long battery runtimes and can be easily added in the field after the SSG units are installed and in service.  

ATC Power Systems
Merrimack, NH.
(603) 429.0391.
[atcpowersystems-products.com].

Acumentrics
Westwood, MA.
(781) 461-8251.
[www.acumentrics.com].

Contour Energy Systems
Azusa, CA.
(626) 610-0660.
[www.contourenergy.com].

Falcon Electric
Irwindale, CA.
(626) 962-7770.
[www.falconups.com].

Saft America
Cockeysville, MD.
(410) 771-3200.
[www.saftbatteries.com].

Schaefer
Hopkinton, MA.
(508) 436-6400.
[www.schaeferpower.com].

Tadiran
Lake Success, NY.
(516) 621-4980.
[www.tadiranbat.com].

TDI Power
Hackettstown, NJ.
(908) 850-5088.
[www.tdipower.com].