A battery unit for a flavor inhaler, comprising: a chargeable and dischargeable power supply ; a connection part capable of electrically connecting to an external charger ; a controller configured to perform control regarding at least the power supply; and a switch configured to allow an electrical connection and disconnection between the external charger and the power supply , wherein the controller is configured to: detect whether the charger is connected to the connection part; while the charger is connected to the connection part , cause the switch to alternate between an electrical connection and disconnection of the power supply to the connection part , such that the electrical disconnection is carried out in response to a first predetermined time period elapsed since the electrical connection has established, and thereafter the electrical connection is carried out in response to a second predetermined time period being elapsed, thereby periodically stopping charging to the power supply from the charger ; measure an accumulated value of a connection time period to the charger without including a period during which charging is periodically stopped, wherein the accumulated value of the connection time period to the charger is counted while the switch is in a connection state; and determine whether the accumulated value of the connection time period to the charger exceeds a first predetermined time period to identify that the power supply has been degraded. a chargeable and dischargeable power supply ; a connection part capable of electrically connecting to an external charger ; a controller configured to perform control regarding at least the power supply; and a switch configured to allow an electrical connection and disconnection between the external charger and the power supply , wherein the controller is configured to: detect whether the charger is connected to the connection part; while the charger is connected to the connection part , cause the switch to alternate between an electrical connection and disconnection of the power supply to the connection part , such that the electrical disconnection is carried out in response to a first predetermined time period elapsed since the electrical connection has established, and thereafter the electrical connection is carried out in response to a second predetermined time period being elapsed, thereby periodically stopping charging to the power supply from the charger ; measure an accumulated value of a connection time period to the charger without including a period during which charging is periodically stopped, wherein the accumulated value of the connection time period to the charger is counted while the switch is in a connection state; and determine whether the accumulated value of the connection time period to the charger exceeds a first predetermined time period to identify that the power supply has been degraded. detect whether the charger is connected to the connection part; while the charger is connected to the connection part , cause the switch to alternate between an electrical connection and disconnection of the power supply to the connection part , such that the electrical disconnection is carried out in response to a first predetermined time period elapsed since the electrical connection has established, and thereafter the electrical connection is carried out in response to a second predetermined time period being elapsed, thereby periodically stopping charging to the power supply from the charger ; measure an accumulated value of a connection time period to the charger without including a period during which charging is periodically stopped, wherein the accumulated value of the connection time period to the charger is counted while the switch is in a connection state; and determine whether the accumulated value of the connection time period to the charger exceeds a first predetermined time period to identify that the power supply has been degraded. <EOS>