Method and circuit for determining battery capacity

• US 4,413,221 A
• Filed: 12/18/1980
• Issued: 11/01/1983
• Est. Priority Date: 12/18/1980
• Status: Expired due to Term

• Current Assignee: Christie Electric Corp. (Transdigm Group Incorporated)
• Original Assignee: Christie Electric Corp. (Transdigm Group Incorporated)
• Inventors: Heil, Robert H., Benjamin, Fred
• Primary Examiner(s): PELLINEN, A DAVID
• Application Number:
  US06/217,897
• Time in Patent Office: 1,048 Days
• Field of Search: 320/5, 320/9-11, 320/13, 320/14, 320/20-22, 320/43, 320/48, 340/636, 324/426, 324/427, 324/429, 324/433, 324/435
• US Class Current: 320/129
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/386 using test-loads
• CPC Class Codes: Y10S 320/33 Aircraft or spacecraft application

Abstract

The capacity of a battery is determined while charging the battery by measuring the time it takes the battery voltage to decrease to a selected voltage level during discharging intervals interspersed between charging intervals. The state-of-charge is also determined by measuring the voltage level during a discharge interval while monitoring the duration of the charge cycle. Additionally, faulty cells of the battery are detected by measuring the voltage of the individual cells at the end of a discharging interval during the charging of the battery.

Claims

1. A method of determining the capacity of a battery comprising the steps of:

imposing an increasing charge on a battery during a plurality of charge intervals and a plurality of discharge intervals interspersed with the charge intervals by applying a charge current to the battery during each charge interval;

applying a load to the battery during each discharge interval until the battery voltage decreases to a selected level;

removing the load in response to the attainment of the selected level to end the discharge interval; and

sensing the duration of each discharge interval as an indication of the capacity of the battery.

2. A method in accordance with claim 1 further comprising the step of displaying the sensed duration as a bar chart having a length indicating the capacity of the battery.

3. A method in accordance with claim 2 wherein the bar chart has a logarithmic time base.

4. A method in accordance with claim 1 wherein the charge current has a fixed duration and a fixed amplitude.

5. A method of determining the capacity of a battery comprising the steps of:

imposing an increasing charge on a battery during a plurality of charge intervals and a plurality of discharge intervals interspersed with the charge intervals by applying a charge current to the battery during each charge interval;

applying a load to the battery during each discharge interval until the battery voltage decreases to a selected level;

removing the load in response to the attainment of the selected level to end the discharge interval; and

measuring the cell trough voltage at the end of the battery discharge interval of each individual cell in succession.

6. The method of determining the capacity of a battery in accordance with claim 5 comprising the further steps of:

applying a portion of the cell voltage to a sample-and-hold circuit at the end of each discharge interval; and

displaying the cell voltage on a meter.

7. A method of determining the capacity of a battery comprising the steps of:

imposing an increasing charge on a battery during a plurality of charge intervals and a plurality of discharge intervals interspersed with the charge intervals by applying a charge current to the battery during each charge interval;

applying a load to the battery during each discharge interval until the battery voltage decreases to a selected level;

removing the load in response to the attainment of the selected level to end the discharge interval;

applying a shunt in the path of the battery discharge current;

developing a signal in response to the voltage across the shunt during each discharge interval with the signal having a duration determined by the duration of the discharge interval; and

applying the signal to a bar chart display.

8. A method in accordance with claim 7 wherein the bar chart display is made up of a plurality of light-emitting diodes driven from a voltage divider network wherein the value of the resistors of the network has a logarithmic relationship.

9. A battery charger analyzer comprising:

a charge current source;

means for applying a selected amplitude of charge current from the source to a battery for a selected interval of time;

means for discharging the battery at the end of each charge current interval;

means for sensing the battery terminal voltage during discharge;

means responsive to the sensing means for terminating each discharge interval upon the battery terminal voltage decreasing to a selected level;

means for sensing the duration of each discharge interval; and

means for displaying this duration as a measure of the charge capacity of the battery.

10. A battery charger analyzer in accordance with claim 9 wherein the display means is a bar chart made up of light-emitting diodes driven by a driver having a voltage divider network with a logarithmic relationship.

11. A battery charger analyzer in accordance with claim 9 further comprising means for measuring the trough voltage of the individual cells of the battery.