Abstract: A method for monitoring and diagnosing the status of a battery in an electrical system, more particularly, a method for determining a battery's reserve time based on comparison of measurements made during a battery discharge to a universal normalized discharge curve. Specifically, a battery discharge is initiated and the battery's voltage and discharge time is continuously measured. The measured battery voltage is normalized by dividing it by either the peak voltage or foothill voltage, as monitored during the discharge. By comparing this normalized voltage measurement to a universal normalized discharge curve, the percent discharge level of the battery is determined. Using the percent discharge level and the discharge time, the reserve time and total capacity of the battery can be determined.

Abstract: A battery diagnostic method for monitoring the status of a battery in an electrical system and continuously providing a relatively accurate prediction of battery condition and performance, more particularly, a self-adjusting method for providing the best possible prediction of a battery's reserve time before, during, and after a battery discharge. The method of the present invention utilizes different prediction methods depending on what state the electrical system is in; that is, before, during or after a battery discharge. By determining what state the system is in, the most effective prediction method can be utilized to provide an accurate battery reserve time. By providing a relatively accurate continuous reserve time prediction, the method helps prevent a complete loss of power in an electrical system relying on a battery to supply the system's electrical power.