Meeting report: Space Power Conference--Redondo Beach, California--April 22-25, 2002

Advanced Battery Technology, Jul 2002 by Roth, Jo'el

Lithium ion has not yet replaced nickel hydrogen as the battery of choice for aircraft, missiles, satellites, and space systems. The search continues for the next, best alternafive. As they proceed in their quest, more than 260 technical professionals from around the world gathered together to share their research results at the 20th Annual Space Power Workshop, April 22 to 25, at the Crown Plaza Hotel in Redondo Beach, California.

The meeting was jointly sponsored by the Air Force Research Laboratory (AFRL), the Air Force Space and Missiles Center (SMC), and The Aerospace Corporation. Dean Marvin of The Aerospace Corporation was the general chairman of the conference. "This is an opportunity for researchers who are working in labs all year to get together and exchange information with the end users, battery manufacturers, and those who participate in government policy and funding activities," he explained. "We have attendees here from many European countries, including Finland, Germany, and France, and a group from Astrium, the European Consortium." Many of those in attendance represented prime contractors, government organizations such as NASA, the Department of Defense (DoD), and the Department of Energy (DOE); the academic community; and product suppliers.

The conference program noted that one goal is to provide a forum for the exchange of the latest information in a casual, unclassified environment. Many who attended are members of the Aerospace Power Systems Technical Committee of the American Institute of Aeronautics and Astronautics. Membership is limited to those who are "...active in the analysis, design, test or application of electrical generation or storage systems for aerospace."

Why does nickel-hydrogen still reign? "Lithium ion has just not been around long enough," explained Valerie Ang of The Aerospace Corporation. Unlike the world of portable electronics, avionics requires many years of performance test data. "We do not have enough solid data about its long-term performance, impedance build-up, or safety issues. We still do not understand enough about cell balancing to make the commitment required to send them up into space for more than five years."

Nickel hydrogen is the battery used most frequently in commercial communications satellites, telephony relays, and devices that stay in space for many years in their geosynchronous orbit.

During the course of the conference, presenters explored the performance of Sanyo nickel cadmium (NiCd), Saft lithium ion, various types of lead acid, Yardney lithium ion, Lion lithium ion, and Eagle Picher nickel hydrogen. Alternative power sources also were explored, including nuclear, solar array, flywheel, and energy storage concentrators.

As concluded by Chuck Lurie of TRW, "There just isn't any one size that fits all." The search continues.

Summary of Battery-Related Presentations

Joe Sovie, manager of Spacecraft Systems at NASA, presented the NASA Space Power Program Overview. Their research continues to pursue "...better and cheaper..." energy sources that provide longer life. The efficiencies of thin film technology are still too low and the mass too great to meet the needs of the tight space and weight requirements. Instead, enhanced nickel-based and lithium batteries are proving the most effective for use in orbiting systems, landers, rovers, and aircraft. In addition, NASA is involved in extensive fuel cell development with several industry partners.

Energy Storage Section

Organized by Valerie Ang of The Aerospace Corp. and Michelle Manzo of NASA and GRC

Lawrence H. Thaller of the Aerospace Corporation explored "Techniques to Improve the Usability of Nickel-- Hydrogen Cells." This chemistry has proven effective for 20 years, and the studies show that cycling efficiency can be improved with lower temperatures and higher KOH concentrations as well as higher cobalt contact, lower end-of-charge voltage, and a minimum recharge ratio. Also, usable energy density can be impacted with lower temperatures, higher KOH concentrations, higher cobalt content, and higher end-of-charge voltage. They found that the cycling characteristics of nickel electrodes can be adjusted according to the needs of each mission's objective.

Judith A. Jeevarajan and Yi Deng of Lockheed Martin presented "Performance and Safety Characteristics of Sanyo NiCd Cells." This study was conducted along with Bobby Bragg of NASA Johnson Space Center and Wenlin Zhang of Schlumberger Reservoir Completion. They based their research on a joint NASA/Dreamtime Holdings project that used NiCd batteries in high definition TVs on the ISS and Space Shuttle. On an STS 105 flight in July 2001, they compared commercial off-the-shelf Sony BP90 packs with Sanyo and Frezzi Energy packs composed of D cells. In tests that had been running since August 1997, they were able to achieve a SC rate for 200 cycles. The cells passed exposure tests at 80 deg C, and vented at about 280psi, but the can did not burst until about 570psi. The cells also passed the vacuum, drop, and vibration tests, and gave acceptable results from the internal short test. During her presentation, Dr. Jeevarajan pointed out, "The cells had to be completely crushed before failure."