System and method of measuring a battery lifetime

A detector for measuring the lifetime remaining until a battery reaches a first predetermined voltage reference which represents a first end-of-life battery voltage, comprising:

• a voltage measuring device selectively connected to the battery for measuring a first battery voltage, which is an instantaneous battery voltage;
• a first subtractor circuit responsive to said voltage measuring device for measuring the difference between at least two instantaneous battery voltage measurements, made at a predetermined time interval by said voltage measuring device, to provide a voltage change rate which is proportional to the difference between the instantaneous battery voltage measurements;
• a second subtractor circuit responsive to said voltage measuring device and the first voltage reference, for measuring the difference between the first battery voltage and the first voltage reference, and providing a first voltage margin which is a voltage proportional to the difference between the first battery voltage and the first voltage reference;
• and
• a first divider circuit responsive to said first and second subtractor circuits to divide the first voltage margin by the voltage change rate to provide a first battery condition, which is a period of time proportional to the time remaining until the first battery voltage approximately equals the first voltage reference, thereby determining the remaining useful life of the battery.

A detector for measuring the lifetime remaining until a battery reaches a first predetermined voltage reference, which represents a first end-of-life battery voltage, and comprising:

• a first comparator having inputs operatively connected to the battery and the first voltage reference to measure the difference between an instantaneous battery voltage and the first voltage reference, said first comparator providing a first voltage margin which is a voltage proportional to the difference between the instantaneous battery voltage and the first voltage reference;
• a voltage gradient measuring device operatively connected to the battery and to a clock pulse having a predetermined time interval, to measure the change in the instantaneous battery voltage with respect to an interval of time, said voltage gradient measuring device providing a voltage gradient, which is the battery voltage rate of change;
• and
• a first condition analyzer operatively connected to said first comparator and said voltage gradient measuring device for dividing the first voltage margin by the voltage gradient, and to output a first battery condition, which is a period of time proportional to the time remaining until the instantaneous battery voltage approximately equals the first voltage reference, whereby the remaining useful life of the battery is determined.