NOVELTY - The pack (1000) has two power sources (1100, 1200) e.g. fuel cell, with two switching circuits (1120, 1140). A current sensor (1300) is serially connected to the power sources to sense currents of the power sources. A controller (1400) obtains voltages of the power sources such that the power sources are not over-charged or over-discharged. The controller calculates an entire capacity of the power sources using amount of currents obtained by the current sensor. The controller outputs a charging stop signal to the respective switching circuits.    USE - Hybrid battery pack for managing and controlling power sources such as fuel cell, solar cell, polygon type lithium ion battery, cylinder type lithium ion battery cell, pouch type lithium polymer battery cell, pouch type lithium ion battery cell (all claimed) and polygon type lithium ion battery cell, using a fuel gauge circuit in an electronic apparatus.    ADVANTAGE - The pack accommodates the power sources having different shapes, chemical characteristics, and capacities, and/or charging voltages, thus minimizing limitations on a space of the hybrid battery pack and maximizes the energy efficiency ratio per volume of the hybrid battery pack. The pack minimizes a number of circuit elements and to correctly determine the capacities of the power sources. The pack prevents supply of power to an external system from being stopped or interrupted. The pack allows a user to continuously use an electronic apparatus without interruption of power.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method of controlling a hybrid battery pack.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a structure of a hybrid battery pack.    Positive electrode terminal (B plus)    Pack positive electrode terminal (P plus)    System management bus (SMBus)    Hybrid battery pack (1000)    Power sources (1100, 1200)    Switching circuits (1120 ,1140)    Current sensor (1300)    Controller (1400)    Memory (1410)    External system (1500)    Load (1510)    Charging circuit (1520)