Method for judging service life of primary battery

Abstract

A method for judging a service life of a primary battery is disclosed, in which, by using a battery pack having a built-in microcomputer, a primary lithium battery is discharged at a given time, a voltage of the primary lithium battery is measured at the time of discharge, and such measured voltage is compared with a specified reference voltage, so that when the measured voltage is less than the reference voltage, the primary lithium battery is judged to have reached the end of its service life. And, the given time is a periodic timing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a circuit of the battery pack in accordance with one embodiment of the present invention;

FIG. 2 is a graph depicting a voltage level and a current value which are present at the time of discharge in accordance with the embodiment of the invention;

FIG. 3 is a graph depicting a voltage level and a current value which are present at the time of discharge at various battery temperatures;

FIG. 4 is a block diagram illustrating a circuit of the battery pack in accordance with an alternative embodiment of the invention; and

FIG. 5 is a flow chart showing how the battery pack, illustrated in FIG. 4, detects a service life and discharge mode of a primary lithium battery.

Claims

1. A method for judging a service life of a primary battery, the method comprising the steps of: discharging a primary battery at a given time;measuring a primary battery's voltage present at the time of discharge; andcomparing such measured voltage with a specified reference voltage, so that when the measured voltage is smaller than the reference voltage, the primary battery is judged to have reached the end of its service life.

2. The method for judging a service life of a primary battery as recited in claim 1, wherein the primary battery comprises a primary lithium battery.

3. The method for judging a service life of a primary battery as recited in claim 1, wherein the given time is a periodic timing.

4. The method for judging a service life of a primary battery as recited in claim 1, wherein the reference voltage is changed in accordance with a battery temperature.

5. The method for judging a service life of a primary battery as recited in claim 1, wherein a discharge mode is measured which indicates whether the primary battery has been discharged without switching on a switching device serving to discharge the primary battery via a discharge resistor.

6. The method for judging a service life of a primary battery as recited in claim 5, wherein when the primary battery is found to be in a discharge mode, the primary battery is judged to have reached the end of its service life.

7. The method for judging a service life of a primary battery as recited in claim 6, wherein the discharge mode of the primary battery is measured by means of an MPU electrically powered from a separate source.

8. The method for judging a service life of a primary battery as recited in claim 7, wherein a battery voltage is detected without switching on the switching device serving to discharge the primary battery via the discharge resistor, such battery voltage is compared with a subsequent battery voltage to be detected after a given time, and a voltage drop in the primary battery is measured, so that when the voltage drop is larger than a predetermined value, the primary battery is judged to be in a discharge mode.

9. The method for judging a service life of a primary battery as recited in claim 8, wherein a voltage of the primary battery is detected, such detected voltage is stored in a non-volatile memory, and a subsequent voltage of the primary battery to be detected after a given time is compared with the detected voltage being stored in the non-volatile memory, so that a voltage drop is detected.

10. The method for judging a service life of a primary battery as recited in claim 7, wherein a discharge current of the primary battery is detected without switching on a switching device serving to discharge the primary battery via a discharge resistor, so that when the discharge current is detected, the primary battery is judged to have been discharged.

11. The method for judging a service life of a primary battery as recited in claim 5, wherein a discharge mode of the primary battery is stored in the non-volatile memory.

12. The method for judging a service life of a primary battery as recited in claim 7, wherein a discharge resistor is employed in discharging the primary battery, and such discharge resistor is a fuse or a PTC element.