Concha M. Reid

Performance characterization of a lithium-ion gel polymer battery power supply system for an unmanned aerial vehicle

ABSTRACT Unmanned aerial vehicles (UAVs) are currently under development for NASA missions, earth sciences, aeronautics, the military, and commercial applications. The design of an all electric power and propulsion system for small UAVs was the focus of a detailed study. Currently, many of these small vehicles are powered by primary (nonrechargeable) lithium-based batteries. While this type of battery is capable of satisfying some of the mission needs, a secondary (rechargeable) battery power supply system that can provide the same functionality as the current system at the same or lower system mass and volume is desired. A study of commercially available secondary battery cell technologies that could provide the desired performance characteristics was performed. Due to the strict mass limitations and wide operating temperature requirements of small UAVs, the only viable cell chemistries were determined to be lithium-ion liquid electrolyte systems and lithium-ion gel polymer electrolyte systems. Two lithium-ion gel polymer cell designs were selected as candidates and were tested using potential load profiles for UAV applications. Because lithium primary batteries have a higher specific energy and energy density, for the same mass and volume allocation, the secondary batteries resulted in shorter flight times than the primary batteries typically provide. When the batteries were operated at lower ambient temperatures (0 to -20 °C), flight times were even further reduced. Despite the reduced flight times demonstrated, for certain UAV applications, the secondary batteries operated within the acceptable range of flight times at room temperature and above. The results of this testing indicate that a secondary battery power supply system can provide some benefits over the primary battery power supply system. A UAV can be operated for hundreds of flights using a secondary battery power supply system that provides the combined benefits of rechargeability and an inherently safer chemistry.

Energy Storage Technology Development for Space Exploration

Abstract The National Aeronautics and Space Administration is developing battery and fuel cell technology to meet the expected energy storage needs of human exploration systems. Improving battery performance and safety for human missions enhances a number of exploration systems, including un-tethered extravehicular activity suits and transportation systems including landers and rovers. Similarly, improved fuel cell and electrolyzer systems can reduce mass and increase the reliability of electrical power, oxygen, and water generation for crewed vehicles, depots and outposts. To achieve this, NASA is developing “non-flow-through” proton-exchange-membrane fuel cell stacks, and electrolyzers coupled with low-permeability membranes for high pressure operation. The primary advantage of this technology set is the reduction of ancillary parts in the balance-of-plant – fewer pumps, separators and related components should result in fewer failure modes and hence a higher probability of achieving very reliable operation, and reduced parasitic power losses enable smaller reactant tanks and therefore systems with lower mass and volume. Key accomplishments over the past year include the fabrication and testing of several robust, small-scale non-flow-through fuel cell stacks that have demonstrated proof-of-concept. NASA is also developing advanced lithium-ion battery cells, targeting cell-level safety and very high specific energy and energy density. Key accomplishments include the development of silicon composite anodes, lithiated-mixed-metal-oxide cathodes, low-flammability electrolytes, and cell-incorporated safety devices that promise to substantially improve battery performance while providing a high level of safety.

Performance and Comparison of Lithium-Ion Batteries Under Low-Earth-Orbit Mission Profiles

Abstract The performance of two 28 V, 25 Ah lithium-ion batteries is being evaluated under low-Earth-orbit mission profiles for satellite and orbiter applications. These space flight-qualified batteries were designed and fabricated by Lithion, Inc. (Yardney Technical Products) for the 2001 Mars Surveyor Program Lander, the first major NASA mission that baselined lithium-ion battery technology. Lithium-ion battery chemistry was an enabling technology for the mission because of its ability to provide low temperature operation in a lightweight and compact battery design. The Mars Surveyor Program mission was cancelled before launch, however, the Lander batteries had already been built and flight-qualified. Lithium-ion batteries are being baselined for increasingly more missions, including missions in low-Earth-orbit and geosynchronous orbit. These mission conditions are more challenging for lithium-ion batteries than a short mission on Mars. Many more cycles are required for operation in low-Earth-orbit and a much longer calendar life is required for operation in either low-Earth-orbit or geosynchronous orbit. A ground test program was established that utilized the Lander batteries from the original mission to demonstrate performance and life under various mission conditions. This paper presents results of the low-Earth-orbit (LEO) portion of the testing that is being conducted at NASA Glenn Research Center (GRC) and NASA Jet Propulsion Laboratory (JPL). The batteries discussed are currently undergoing life testing and have each achieved over 12,000 cycles to 40 percent depth-of-discharge. Each battery is cycling at a different temperature, one at 23 °C and the other at 0 °C. In addition to cycling under low-Earth-orbit conditions, the batteries have been characterized at 500 to 1000 cycle intervals throughout the life testing to observe their capacity and DC impedance changes. Because the batteries are not equipped with cell balancing electronics, cell balancing is manually performed on each battery when cell voltage dispersion exceeds the established threshold. The performance of the batteries will be discussed individually and their performance relative to each other at the different test conditions will be compared.

The Effect of Variable End of Charge Battery Management on Small-Cell Batteries

ABSL Space Products is the world leading supplier of Lithium-ion batteries for space applications and has pioneered the use of small capacity COTS cells within large arrays. This small-cell approach has provided many benefits to space application designers through increased flexibility and reliability over more traditional battery designs. The ABSL 18650HC cell has been used in most ABSL space battery applications to date and has a recommended End Of Charge Voltage (EOCV) of 4.2V per cell. For all space applications using the ABSL 18650HC so far, this EOCV has been used at all stages of battery life from ground checkout to in orbit operations. ABSL and NASA have identified that, by using a lower EOCV for the same equivalent Depth Of Discharge (DOD), battery capacity fade could be reduced. The intention of this paper is to compare battery performance for systems with fixed and variable EOCV. In particular, the effect of employing the blanket value of 4.2V per cell versus utilizing a lower EOCV at Beginning Of Life (BOL) before gradually increasing it (as the effects of capacity fade drive the End Of Discharge Voltage closer to the acceptable system level minimum) is analyzed. Data is compared from ABSL in-house and NASA GRC tests that have been run under fixed and variable EOCV conditions. Differences in capacity fade are discussed and projections are made as to potential life extension capability by utilizing a variable EOCV strategy.

Low Temperature Low -Earth -Orbit Testing of Mars Surveyor Program Lander Lithium -Ion Battery

A flight -qualified, lithium -ion ( Li -ion ) battery fabricated for the Mars Surveyor Program 2001 lander is undergoing life -testing at low temperature under a low -Earth -orbit (LEO) profile to assess its capability to provide long term energy storage for aerospace missions. Li -ion batteries are excellent candidates to provide power and energy storage for sate llites in LEO due to their high specific energy, high energy density, and excellent low temperature performance. Although Li -ion batteries are increasingly being used for aerospace m issions in geosynchronous orbit, some challenges still remain before they can be deemed a suitable replacement for their secondary alkaline battery counterparts in long cycle life LEO applications. Life cycle testing of this battery is being conducte d in the l aboratory to characterize battery -level performa nce and to examine the dynamics of individual cells with in the stack under aerospace conditions . Data generated in this work is critical to establish confidence in the technology for its widespread use in manned and unmanned missions. This paper discusses the performance of the 28 volt, 25 ampere -hour battery through 9000 LEO cycles, which corresponds to over 18 months on LEO orbit. Testing is conducted at 0 °C and 40% depth -of -discharge. Individual cell behaviors and their effect on the performance of the battery are descr ibed . Capacity, impedance, energy efficiency, end of -discharge voltages , and cell voltage dispersions are reported. Relationships between cell temperatures, cell impedance, and their relative position in the battery stack are discussed.