Method and apparatus for measuring the voltage and charge of a battery

• US 5,315,253 A
• Filed: 08/28/1992
• Issued: 05/24/1994
• Est. Priority Date: 05/22/1989
• Status: Expired due to Term

• Current Assignee: Alexander Technologies Europe Ltd.
• Original Assignee: Alexander Manufacturing Co.
• Inventors: Hall, Larry, Klusman, Larry, Kindschuh, Dennis P., Potratz, Steve, Peden, Perry B., Alexandres, Richard B.
• Primary Examiner(s): Wieber, Kenneth A.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/937,223
• Time in Patent Office: 634 Days
• Field of Search: 324/426, 324/427, 324/435, 324/437, 324/428, 324/429, 324/433, 340/636, 320/48, 320/37, 320/38
• US Class Current: 324/429
• 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

Method and apparatus for measuring the voltage and state of charge of a secondary battery. The voltage and state of charge values are taken by a circuit every four (4) seconds by reading voltage, waiting two (2) seconds, reading current, waiting two (2) seconds, and repeating the voltage readings and the current readings. The circuit includes a 4-bit microprocessor, CMOS analog switches, and two operational amplifiers. The voltage and current readings are taken from dual-sloped converters, and the values determined by software algorithms in the microprocessor.

Claims

1. Apparatus for measuring the voltage on a battery comprising:

a. a battery for storing electrical power;

b. voltage regulator means connected to said battery having a constant reference output voltage;

c. integrating means including a capacitor connected to said constant reference output voltage of said voltage regulator means and said battery; and

,

d. microprocessor means connected to said constant reference output voltage for initiating, charging and discharging of said capacitor, timing the charging and discharging of said capacitor, and computing battery voltage by comparing the ratios of charge time to discharge time and constant reference output voltage to battery voltage.

2. The apparatus of claim 1 further including means for displaying the battery voltage.

3. The apparent of claim 2 wherein the means for displaying is an LCD.

4. The apparatus of claim 2 wherein said means for displaying is positioned on a battery charger housing.

5. The apparatus of claim 1 wherein said charging out discharging times are dependent on said constant reference output voltage.

6. The apparatus of claim 1 wherein said battery is a NiCad battery.

7. The apparatus of claim 1 wherein said battery is an alkaline battery.

8. The apparatus of claim 1 wherein said battery is a mercury battery.

9. The apparatus of claim 1 wherein said battery is a gel battery.

10. Apparatus for measuring the current consumed by or added to a battery comprising:

a. a battery for storing electrical power;

b. a shunt resistor and load connected in series with said battery, said shunt resistor being of low resistance and high precision;

c. amplification means having an output for amplifying the voltage drop across said chart resistor;

d. integrating means connected to the output of said amplification means, said integrating means including a capacitor; and

,

e. a microprocessor connected to said integration means for initiating charging of said capacitor as a function of said amplified voltage across said shunt resistor, discharging said capacitor, timing said discharge, and compacting battery current as a function of said discharge time.

11. The apparatus of claim 10 further including means for displaying battery current.

12. The apparatus of claim 11 wherein said means for displaying is an LCD.

13. The apparatus of claim 11 wherein said means for displaying is positioned on a battery charger housing.

14. The apparatus of claim 10 wherein said battery is a NiCad battery.

15. The apparatus of claim 10 wherein said battery is a mercury battery.

16. The apparatus of claim 10 wherein said battery is a gel battery.

17. The apparatus of claim 10 further including calibration means for said amplification means.

18. The apparatus of claim 17 wherein said calibration means comprises analog multiplexers and an operational amplifier connected to said amplification means.

19. The apparatus of claim 18 further including multiplexers in circuit with said amplification means and said integration means.

20. The apparatus of claim 19 wherein said microprocessor controls said multiplexer so as to alternate between calibration and current sensing modes.

21. Apparatus for measuring the voltage and current of a battery comprising:

a. a battery for storing electrical energy;

b. voltage regulator means connected to said battery having a constant reference output voltage;

c. integrating means including a capacitor connected to said constant reference output voltage and said battery;

d. microprocessor means connected to said constant reference output voltage for initiating charging and discharging of said capacitor, timing, charging and discharging of said capacitor, and computing battery voltage by comparing the ratios of charge time to discharge time and constant reference output voltage to battery voltage;

e. a shunt resistor and load connected in series with said battery, said shunt resistor being of low resistance and high precision;

f. amplification means having an output for amplifying the voltage drop across said shunt resistance;

g. integrating means connected to the output of said amplification means, said integration means including a capacitor; and

,

f. said microprocessor further connected to said integration means for initiating charging of said capacitor as a function of said amplified voltage across aid shunt resistor, discharging said capacitor, timing said discharge, and computing battery current as a function of said discharge time.

22. Apparatus of claim 21 further including means for displaying said voltage out current.

23. The apparatus of claim 22 wherein said means for displaying is an LCD.

24. The apparatus of claim 23 wherein said LCD display is positioned over a battery charger housing.