Impact of Test Conditions While Screening Lithium-Ion Batteries for Capacity Degradation in Low Earth Orbit CubeSat Space Applications

A wide variety of commercial cylindrical lithium-ion batteries are available for use in nanosatellites (CubeSats) that cycle in low Earth orbit (LEO). This space application differs greatly from the conditions used to create the manufacturer datasheets that CubeSat teams rely on to screen cell types and estimate performance lifetimes. To address this, we experimentally test three LIB cell types using a representative LEO CubeSat power profile in three progressively complex test representations of LEO. The first is "standardized" condition (101 kPa-abs, 20 degrees C), which uses only a power cycler; the second adds a thermal chamber for "low temperature" condition (101 kPa-abs, 10 degrees C); and the third adds a vacuum chamber for "LEO" condition (0.2 kPa-abs, 10 degrees C). Results indicate that general "standardized" and "low temperature" conditions do not yield representative results to what would occur in LEO. Coincidentally, the "LEO" condition gives similar capacity degradation results as manufacturer datasheets. This was an unexpected finding, but suggests that CubeSat teams use full experimental thermal-vacuum testing or default to the manufacturer datasheet performance estimates during the lithium-ion cell screening and selection process. The use of a partial representation of the LEO condition is not recommended.