Low-battery state detecting system and method for detecting the residual capacity of a battery from the variation in battery voltage

• US 5,287,286 A
• Filed: 06/08/1993
• Issued: 02/15/1994
• Est. Priority Date: 07/31/1989
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ninomiya, Ryozi
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US08/073,987
• Time in Patent Office: 252 Days
• Field of Search: 340/636, 320/48, 364/481, 364/483
• US Class Current: 702/63
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

There is provided a low-battery detection reference voltage table for memorizing the correspondence between current values and low-battery detection reference voltage values, which is obtained from battery voltage characteristic curves corresponding to different current values. Further, there is provided a low-battery reference voltage correction table for correcting the low-battery detection reference voltage in accordance with a voltage variation. Referring to the low-battery detection reference voltage table on the basis of the value of current output from the battery, the low-battery detection reference voltage corresponding to the current value is obtained. The voltage variation is found from the currently measured battery voltage and the previously measured battery voltage which is memorized. On the basis of the voltage variation, the correction voltage is found with reference to the low-battery reference voltage correction table. The found correction voltage is added to the low-battery reference voltage, thereby correcting the low-battery reference voltage. When the measured battery voltage is lower than the corrected low-battery detection reference voltage, the low-battery stated is determined.

Claims

1. A low-battery detection warning method comprising the steps of:

a) generating a discharge current signal related to a discharge current value outputted from a battery;

b) generating a low-battery detection reference voltage from the discharge current signal;

c) generating a first and a second voltage signal related to a first and a second voltage value of the battery determined at sequential times;

d) employing electronic processing means to determine a difference between the first and second voltage signals;

e) employing said electronic processing means to modify the low-battery detection reference voltage in accordance with the determined difference and battery voltage characteristic curves corresponding to different charge time periods, so as to make constant a time period from the time a low-battery stage was determined to the time when a device driven by the battery fails to operate normally, irrespective of a charge time for the battery;

f) employing said electronic processing means to compare the modified low-battery detection reference voltage with the first voltage signal, and determining the low-battery state when the first voltage signal is lower than the modified low-battery detection reference voltage; and

g) generating a detection warning signal when the low-battery state has been determined to exist.

2. The method according to claim 1, wherein the step (b) includes a step of generating the low-battery detection reference voltage, on the basis of the battery voltage characteristic curves which correspond to different current values.

3. A low-battery detection warning system comprising:

current detector means for measuring a discharge current from a battery;

voltage detector means for measuring a voltage value from the battery;

first table memory means for containing low-battery detection reference voltages which correspond to measured battery discharged current values;

second table memory means for containing low-battery detection reference correction values which correspond to variations in measured battery voltage values; and

electronic processing means for;

     1) obtaining a low-battery detection reference voltage in accordance with the discharge current measured by the current detector means from the first table means,

     2) obtaining a low-battery detection reference correction value in accordance with variations in voltage values measured by the voltage detector means from the second table means,

     3) correcting the low-battery detection reference voltage from the first table means with low-battery detection voltage correction values from the second table means and battery voltage characteristic curves, thus making constant time periods measuring from the time when a low-battery state is determined to the time when a device driven by the battery ceases normal operation, irrespective of the battery charge time, and

     4) determining the low-battery state on the basis of the corrected low-battery detection reference voltage and generating a low-battery detection warning signal based upon the determination of the low-battery state.

4. The system according to claim 3, wherein the electronic processing means corrects the low-battery detection reference voltage on the basis of the battery voltage characteristic curves which correspond to different current values.

5. A low-battery detection warning system comprising:

current detector means for measuring a discharge current from a battery;

voltage detector means for measuring a first voltage value and a second voltage value from the battery at sequential times; and

central processing means for;

     1) determining a corresponding low-battery detection reference voltage in accordance with a discharge current value from the current detector means,

     2) determining a voltage difference between the first and second measured voltages,

     3) correcting the low-battery detection reference voltage in accordance with the voltage difference and battery voltage characteristic curves, which correspond to different battery charge times, so as to make constant time periods measuring from the time when a low-battery state is determined to the time when a device driven by the battery ceases normal operation, irrespective of the battery charge time, and

     4) comparing the corrected low-battery detection reference voltage and the measured battery voltage for determining that a low-battery state exists when the first measured battery voltage is lower than the corrected low-battery detection reference voltage, and generating a low-battery detection warning signal based upon the determination of the low-battery state.

6. The system according to claim 5, wherein the central processing means corrects the low-battery detection reference voltage on the basis of the battery voltage characteristic curves corresponding to different current values.

7. An electronic equipment operable by a rechargeable battery, comprising:

current detector means for measuring a discharge current value from the battery;

voltage detector means for measuring a voltage value from the battery;

first determining means for determining a reference voltage for detecting a low battery state in accordance with the discharge current value measured by the current detector means;

memory means for storing correction values for correcting the low-battery-detection reference voltage determined by the first determining means, the correction values being used for making constant time periods measured from the time when the low battery state is detected to the time when the electronic equipment ceases normal operation, the correction values corresponding to respective charging times of the battery;

second determining means for determining the charging time of the battery based on the time required for the battery voltage being reduced to a predetermined voltage value;

correcting means for correcting the low-battery-detection reference voltage determined by the first determining means with one of the correction values stored in the memory means, the one correction value being determined by the second determining means based on the charging time of the battery;

detecting means for detecting the battery voltage being less than the low-battery-detection reference voltage corrected by the correcting means; and

means for generating a warning signal in accordance with a result of the detecting means.

8. A portable electronic equipment operable by a battery, comprising:

current detector means for measuring a discharge current value from the battery;

voltage detector means for measuring a voltage value from the battery;

determining means for determining a reference voltage for detecting a low battery state in accordance with the discharge current value measured by the current detector means;

memory means for storing correction values for correcting the low-battery-detection reference voltage determined by the determining means, the correction values being used for making constant time periods measured from the time when the low battery state is detected to the time when the electronic equipment ceases normal operation, the correction values corresponding to respective charging times of the battery;

correcting means for correcting the low-battery-detection reference voltage determined by the determining means with one of the correction values stored in the memory means, the one correction value being based on the time required for the battery voltage being reduced to a predetermined voltage value;

detection means for detecting the battery voltage being less than the low-battery-detection reference voltage corrected by the correcting means; and

means for generating a warning signal in accordance with a result of the detection means.