An apparatus for and a method of controlling battery discharge. A number of battery switching operations is minimized by detecting a remaining voltage capacity of each of a plurality of batteries supplying a battery-powered electronic device with power. The remaining voltage capacities of an internal battery and an external battery are detected and corresponding flags are set for the internal and external batteries according to predetermined conditions. A discharge status of at least one of the internal battery and the external battery is controlled by referring to the flags and a remaining voltage capacity of each of the internal battery and the external battery.