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

• US 5,144,248 A
• Filed: 05/22/1989
• Issued: 09/01/1992
• 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, Alexandres, Richard B., Klusman, Larry, Kindschuh, Dennis P., Potratz, Steve, Peden, Perry B.
• Primary Examiner(s): Wieder, Kenneth A.
• Application Number:
  US07/355,679
• Time in Patent Office: 1,198 Days
• Field of Search: 324/426, 324/427, 324/428, 324/435, 324/436, 324/433, 324/430, 340/636, 320/48
• US Class Current: 324/428
• 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. An apparatus comprising

a. a load;

b. a NiCad battery coupled to said load;

c. a shunt resistor coupled in series between said battery and said load

d. a current conditioner coupled in parallel with said shunt;

e. a voltage conditioner coupled in parallel with said load wherein said voltage conditioner further comprises means for supplying a reference voltage, means coupled to said NiCad battery and said supplying means for developing a comparison signal representing the difference between said reference voltage to said voltage of said NiCad battery, means coupled to said developing means for integrating said comparison signal, and means coupled to said microprocessor and said integrating means for indicating the time of said integrating;

f. a microprocessor coupled to said current conditioner and said voltage conditioner for periodically determining current and voltage of said NiCad battery; and

g. a liquid crystal display coupled to said microprocessor for periodically displaying said current and said voltage of said NiCad battery.

2. An apparatus according to claim 1 wherein said current conditioner further comprises:

means coupled to said shunt for measuring a voltage drop across said shunt; and

,

b. means coupled to said microprocessor and said measuring means for providing a signal to said microprocessor indicative of said voltage drop.