Even after the battery reaches the last stage of the end of life, the use can be continued. A charging system includes battery pack and charger. During the charge of lithium-ion secondary battery, charge control unit calculates the full charge capacity maintaining rate, sets a first charge current value on the basis of the full charge capacity maintaining rate, and charges the battery. When lithium-ion secondary battery reaches the last stage of the end of life, charge control unit sets a second charge current value lower than the first charge current value set based on the full charge capacity maintaining rate, and charges the battery.