Nickel-cadmium battery state-of-charge measuring method

• US 4,644,245 A
• Filed: 01/28/1985
• Issued: 02/17/1987
• Est. Priority Date: 01/28/1985
• Status: Expired due to Fees

• Current Assignee: Applied Electro Mechanics, Incorporated
• Original Assignee: Applied Electro Mechanics, Incorporated
• Inventors: Brown, Harry B.
• Primary Examiner(s): Hickey, R. J.
• Application Number:
  US06/692,982
• Time in Patent Office: 750 Days
• Field of Search: 320/13, 320/14, 320/21, 320/39, 320/48, 324/429
• US Class Current: 320/127
• CPC Class Codes: G01R 31/378 specially adapted for the type of battery or accumulator
• CPC Class Codes: H02J 7/00711 with introduction of pulses during the charging process
• CPC Class Codes: Y10S 320/21 State of charge of battery

Abstract

The terminal voltage of nickel-cadmium battery is measured while the battery is placed under a heavy discharge load during a predetermined short interval.

Claims

1. A method of determining the state of charge of a nickel-cadmium battery, which comprises

discharging the battery through a low impedance path at the rate of about 50 to 80 amperes for a pulse discharge period of about one millisecond,

measuring the highest battery terminal voltage sustained during the major portion of the discharge period,

wherein the battery terminal voltage is stored in a capacitor which is connected across a battery current path concurrently with the pulse discharge period, and wherein the charge remaining in the capacitor is measured subsequent to the termination of the discharge period,

wherein the low impedance path includes a resistor of relatively low impedance and wherein the high impedance path includes a resistor of relatively high impedance,

wherein said reisistors are in parallel to the battery throughout the pulse discharge period and for time intervals preceding the pulse discharge period, further including the step of shorting out the high impedance resistor throughout the pulse discharge period.

2. The method claimed in claim, 1 wherein the battery terminal voltage is measured by connecting the capacitor across the battery terminals no sooner than a first portion of the pulse discharge period and disconnecting the capacitor from across the battery terminals no later than the end of the pulse discharge period.