Recharging of a secondary battery within a short time after the battery is fully charged is prevented. A method of achieving this prevention includes: a charging step of charging a secondary battery by external power until a charging amount of the secondary battery becomes equal to a fully charged amount, while stopping a driving component; and a stop continuation step of stopping the charging of the secondary battery by the external power and stopping a driving component in a stop continuation period in which the charging amount of the secondary battery decreases from the fully charged amount to a predetermined charging amount.