Power supply method and electronic device therefor

An electronic device may include, for example: a first battery; at least one second battery; a power management module configured to monitor capacity information of the first battery; and a processor electrically connected to the first battery, the at least one second battery, and the power management module. The processor may be configured to: monitor whether a designated event or a low-power state in which a voltage of the first battery drops below a reference value has occurred, while the electronic device is driven using the first battery; determine that the designated event has occurred or that the first battery corresponds to the low-power state; and parallel-connect the first battery and at least one of the at least one second battery, based on determining that the designated event has occurred, or that the first battery corresponds to the low-power state. Various other embodiments are possible.