The Japanese spacecraft, HAYABUSA, was launched on May 9, 2003 and spent more than 2.5 years approaching the asteroid ITOKAWA. This spacecraft used 13.2 Ah lithium-ion secondary cells. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage in case it is required for contingency operations. To maintain this SOC condition, the battery is charged once a week. After HAYABUSA touched down on ITOKAWA in December 2005, four of 11 lithium-ion secondary cells were over-discharged. However, the battery power was still indispensable for sealing the container with the asteroid sample. The seven remaining healthy cells were slowly recharged using minimum current. After its safety was confirmed, the lithium-ion secondary battery was used to transfer, latch, and successfully seal the sample container into the reentry capsule. The seven remaining cells have been slowlydischarged through the resistance of the monitoring circuit. The capacity by the discharge revealed that the storage performance of the lithium-ion secondary battery is predictable based on the ground-test results even after the storage for 5 years in space.