A 28-V, 25-A-hr lithium-ion (Li-ion) battery that was designed, built, and flight-qualified for the 2001 Mars Surveyor Program Lander is being tested at the NASA Glenn Research Center at 0 °C in a low-Earth-orbit cycle (LEO) regime. In 2005, a milestone was achieved when the battery passed 10,000 cycles. This testing is part of a coordinated test program among several organizations to evaluate the performance of Li-ion batteries under a variety of aerospace mission profiles. Five flight-qualified batteries became available for evaluation upon the cancellation of the 2001 Mars Surveyor Program mission. Since then, the batteries have undergone testing in various LEO, geosynchronous orbit, and planetary mission profile regimes. Organizations participating in the evaluations include the NASA Jet Propulsion Laboratory, the Naval Research Laboratory, the Air Force Research Laboratory, and Glenn.
Mars Surveyor Program Lander Battery in the test chamber.
Long description of figure 1.
The battery contains eight prismatic Li-ion cells connected in series (see the photograph). The cells contain a liquid organic electrolyte, a mesocarbon microbead anode, and a lithium nickel cobalt oxide (LiNiCoO2) cathode. The battery does not contain charge-balancing electronics.
Glennís test program began with characterization of the battery to measure baseline performance followed by LEO life-cycle testing at 0 °C, which is ongoing. The LEO test profile consists of a 90-min orbit with a 55-min charge period and a 35-min discharge period during which the battery is discharged to 40-percent depth-of-discharge (DOD). Characterization tests are conducted at 1000-cycle intervals. Thus far, cell balancing, which is performed when the individual cell voltages diverge beyond a predetermined value, has been required only once during the life test, after 7000 cycles.
The battery continues to display excellent performance during its cycling. Some performance metrics are given here, including capacity, end-of-discharge voltage (EODV), efficiency, and specific energy.
Baseline capacity at 100-percent DOD was 25.7 A-hr. At 10,000 cycles, the 100-percent DOD capacity measured 24.2 A-hr, which represents 94 percent of the baseline. The EODV has decreased from an initial 27.95 V at the beginning of LEO cycling to 27.28 V after 10,000 LEO cycles (see the graph). A linear trend projection of the performance would predict a battery EODV of approximately 26.3 V at the 5-yr, 30,000-cycle point, which is well above the 24-V minimum battery-voltage level. However, the electrochemical processes that contribute to battery aging have not been accurately modeled in this simple projection.
EODV versus cycle number.
Long description of figure 2.
Li-ion battery chemistries typically display excellent efficiencies. For this battery, coulombic efficiency is consistently 100 percent throughout LEO cycling. Energy efficiency is between 90 and 93 percent during LEO cycling.
The battery can deliver an average specific energy of 76 W-hr/kg at 100-percent DOD and 32 W-hr/kg during LEO cycling. The specific energy for the battery was calculated using the mass of the entire flight battery assembly, including the cell stack, battery wiring, deck plate, and connectors. In order to meet mission requirements, the Mars lander battery was fortified with robust construction designed to tolerate the impact it would sustain during its landing on the surface of Mars.
Li-ion batteries are excellent candidates to provide power and energy storage for satellites in LEO due to their high specific energy, high energy density, and high efficiency. Although Li-ion batteries are increasingly being used for aerospace missions 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 test data of Li-ion batteries are critical to establishing confidence in Li-ion battery technology for widespread use in manned and unmanned missions.
Reid, Concha: Low Temperature Low-Earth-Orbit Testing of Mars Surveyor Program Lander Lithium-Ion Battery. AIAA-2005-5562, 2005.
Reid, C.: Low Temperature Life-Cycle Testing of a Lithium-Ion Battery for Low-Earth-Orbiting Spacecraft. Presented at the NASA Aerospace Battery Workshop, Huntsville, AL, 2004.
Find out more about Glennís Electrochemistry Branch: http://www.grc.nasa.gov/WWW/Electrochemistry/
Concha M. Reid, 216-433-8943, Concha.M.Reid@nasa.gov; and Michelle A. Manzo, 216-433-5261, Michelle.A.Manzo@nasa.gov
Author: Concha M. Reid
Headquarters program office: Exploration Systems
Programs/Projects: Exploration Technology Development Program, Energy Storage Project
Last updated: October 16, 2006
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