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Abstract

A method and apparatus for monitoring the operational state (C.sub.R) and stand-by (t.sub.St) of a battery averages battery currents (I.sub.B) and battery voltages (U.sub.B) and determines the operating mode (charging L.sub.A, or discharging, E.sub.n) from the direction of the battery current (I.sub.B). When discharging (E.sub.n), a discharge power (P.sub.En) is calculated form the average battery current (I.sub.Bm) and battery voltage (U.sub.Bm). The average cell voltage (U.sub.BZ) is determined by dividing the average battery voltage (U.sub.B) by the number of cells (Z.sub.Z) in the battery. The cell discharge power (P.sub.EnZ) is determined by dividing the discharge power (P.sub.En) by the number of cells (Z.sub.z) in the battery. Consequently, the cell discharge time (t.sub.p) is known since it is proportional to the cell discharge power (P.sub.EnZ). The cell discharge power (P.sub.EnZ) is then compared with stored families of curves of cell voltage versus withdrawn capacity (C.sub.En) and cell discharge power (P.sub.EnZ). The withdrawn capacity (C.sub.En) is determined from the average cell voltage (U.sub.BZ) and the previously determined cell discharge power (P.sub.EnZ). The withdrawn capacity (C.sub.En) is subtracted from the maximum capacity (C.sub.max) to determine the residual capacity (C.sub.R), which is multiplied by the discharge time (t.sub.p). Consequently with the aid of only one family of curves and without large expenses, the operational state (C.sub.R) and the stand-by (t.sub.St) of a battery can be monitored.

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