A portable phone has an internal battery and an external battery pack that is releasably attachable to the phone. A control unit in the phone controls connection of the respective batteries to a phone power input, depending on the detection of the external battery voltage. Whenever an external battery is present with a voltage above a predetermined minimum value, the external battery will be connected to the phone power input to provide power to operate the phone, so that the internal battery lifetime is extended. When the external battery voltage falls below the minimum value, or the external battery is removed, the unit automatically switches to internal battery power, so that the external battery can be changed without interrupting power supply to the phone, if the phone is on or during a call. An improved multi-phase software controlled battery-charging method and apparatus is used to charge the internal and external battery packs. The preferred battery-charging method uses a multi-phased charging approach comprising a trickle-charging phase, a fast-charging phase, and a top-off charging phase. The internal battery is charged to near-full capacity by trickle-charging (when required) and subsequently fast-charging the battery. The external battery is similarly charged to near-full capacity. Thus, both batteries are charged to near-full capacity in a substantially reduced charging time period as compared with the total charging time.
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