NOVELTY - The inventive battery control apparatus includes a charge detection circuit (5,6) for detecting a change in battery (B1,B2,B3,B4) charge-state, according to the output current available on load. A first residual charge, available at a given time, detection circuit (3), connected to circuit (5,6), compensates for a predetermined reference residual charge, according to the measured change in charge-state. A second residual charge detection circuit (4) operates in accordance with the battery terminal voltage. A reference residual charge up-dating circuit operates on the second residual charge available, at a time when the battery output current has reduced to zero or almost zero.    USE - To provide electrical battery state-of-charge, without depending on accumulated charge/discharge cycle current variation, or on the temperature dependency of terminal voltage measurement. For computer, electric bicycle, portable telephone.    ADVANTAGE - Overcomes prior art deficiencies by combining residual charge detection by output current integration with residual charge detected from terminal output voltage available, deriving an intermediate residual charge measurement based on terminal voltage when output current is almost zero, for use as a reference for detecting a final residual charge available.    DESCRIPTION OF DRAWING(S) - The drawing shows in block diagram form a battery pack apparatus in accordance with a first embodiment of the inventive system.    Battery pack (1)    Switching apparatus for battery output (2)    Central processing unit (CPU) controlling charge-discharge of (3)    Battery cells within (B1,B2,B3,B4)    Battery in accordance with terminal voltages (B)    Amplifier for terminal voltages (4)    Detection resistor (5)    Amplifier for detecting signal across 5 (6)    Temperature detector eg. thermistor (7)    Field-Effect Transistor (FET discharge control (9)    FET charge control (10)    Driver compensator for ground level difference between 9,10 (11)    Power-saving logic circuitry for CPU operating mode (12)    Non-volatile memory for storing eg. calibration data to improve detection accuracy of battery terminal voltage measurements (13)