Self-correcting and adjustable method and apparatus for predicting the

Abstract

A self-correcting and adjustable apparatus and method of predicting remaining capacity (Q) and reserve time (t) of a discharging battery to a selected end voltage determined by an arrangement considering the open circuit voltage (E.sub.oc), battery voltage (V) battery temperature (T) and battery internal resistance (R.sub.int). The apparatus and method of the present invention utilize a calculation process which first compares calculated and measured capacity discharged between two times (Q.sub.dis.calc. -Q.sub.dis.act.). If this difference exceeds a certain predetermined tolerance or limit of error, the calculation process is adjusted or tuned and the comparison is repeated until the difference between the actual capacity and the calculated capacity are within a predetermined tolerance. The calculation process is tuned by adjusting the value attributed to the battery's internal resistance (R.sub.int). A correlation between battery capacity and battery internal resistance is used to make a reasoned initial adjustment to the calculation process. Then an iterative process of successive approximations is used to tune the calculation process within a given tolerance factor. Once the calculation process has been tuned, the adjusted internal resistance (R.sub.int) is then used for subsequent calculations of remaining battery capacity (Q) and reserve time (t). The calculation process may be tuned or adjusted initially, intermittently, or throughout the battery discharge.