Implementation of commercial Li-ion cells on the MarCO deep space CubeSats

In NASA's first technology demonstration of CubeSats in deep space, MarCO-A and MarCO-B were launched with the Mars InSight mission. These CubeSats successfully transmitted the InSight lander's entry, descent, and landing telemetry back to Earth in near-real time, which was not possible with existing Mars orbital data relay systems. In addition to solar arrays, each MarCO CubeSat was powered by a 3S4P battery comprising 18650-size lithium-ion cells. These commercial lithium-ion cells (Panasonic NCR18650B) were screened and matched using a cell selection process that was simplified relative to larger missions, to ensure safe and reliable battery behavior at an acceptable cost. This paper describes the design of the MarCO power system and battery, the lithium-ion battery cell testing and screening processes and results, and initial performance data from MarCO flight telemetry. •Li-ion batteries with commercial 18650 cells supported MarCO CubeSats successfully.•Panasonic NCRB 18650 cells showed high specific energy and radiation tolerance.•Space-quality batteries are possible with COTS cells with suitable cell selection.•MarCO CubeSats were used to follow Entry Descent and Landing of Mars Insight Lander.