Method and apparatus for determining battery life

• US 6,842,708 B2
• Filed: 04/26/2002
• Issued: 01/11/2005
• Est. Priority Date: 04/27/2001
• Status: Active Grant

• Current Assignee: Lenovo PC International Limited (Lenovo Group Ltd.)
• Original Assignee: International Business Machines Corporation
• Inventors: Odaohhara, Shigefumi
• Primary Examiner(s): WASHBURN, DOUGLAS N
• Application Number:
  US10/133,922
• Publication Number:
  US 20020161537A1
• Time in Patent Office: 991 Days
• Field of Search: 320/134, 320/162, 324/426, 324/427, 324/428, 324/429, 702/57, 702/63, 702/60, 738/617.8, 429/91, 455/572, 607/27, 607/29
• 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: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: G06F 1/28 Supervision thereof, e.g. detecting power-supply failure by out of limits supervision

Abstract

A method and apparatus in accordance with the present invention determines the life of a battery which is repeatedly charged and discharged while providing power to one or more electronic devices. The battery is provided with a circuit for measuring current while the battery is charged, another circuit for stopping the charging of the battery, a circuit for measuring the voltage of the battery while charged and while charging is stopped. A CPU is included for computing an internal impedance depending on the measured battery voltage, the current under charge and the battery voltage while charging is stopped. An embedded controller is also included for determining the life of the battery depending upon the information about the internal impedance calculated by the CPU. Finally, information about the battery life can be displayed or delivered to a user at a predetermined time or continuously during use.

Claims

1. A battery-life detection method for detecting a life of a battery for performing charge and discharge and supplying power to a body, comprising the steps of:

measuring the voltage of the battery at a constant current whose value is stabilized while the battery is charged or discharged;

measuring the current value of the battery at the constant current;

stopping supply of current at the constant current;

measuring the stop battery voltage that is the voltage of the battery when supply of the current is stopped;

computing the internal impedance of a battery in accordance with the battery voltage, the current value, and the stop battery voltage; and

determining the life of a battery in accordance with the internal impedance.

2. A computer apparatus having a battery pack which repeatedly charges and discharges to supply power from the battery pack to a system body, wherein the battery pack comprises:

a voltage measurement circuit for measuring a battery voltage when charging is, performed and when charging is stopped;

a current measurement circuit for measuring a charge current;

and a CPU for computing an internal impedance in accordance with the measured battery voltage and charge current, and wherein the system body comprises;

a controller for determining a life of the battery pack in accordance with the internal impedance computed by the CPU of the battery pack;

wherein the controller of the system body temporarily stops the charge of the battery pack when charging the battery pack at a constant current and determines the life of the battery pack in accordance with the internal impedance computed in accordance with the battery voltage when the charge is temporarily stopped

and a display for displaying a message about the determined life.

3. A battery-life determination system for determining the life of a secondary battery for

supplying power to a body, the system comprising:

an under-charge-battery-voltage measurement unit for measuring the battery voltage while the secondary battery is charged;

a charge current measurement unit for measuring the charge current while the secondary battery is charged;

a stop unit for stopping charge of the secondary battery while the secondary battery is charged;

an under-stop-bettery-voltage measurement unit for measuring the under-stop battery voltage of the secondary battery while charge of the secondary battery is stopped by the stop unit;

an internal impedance computation unit for computing the internal impedance of the secondary battery in accordance with the battery voltage and charge current under the charge and the under-stop battery voltage; and

a life determination unit for determining the life of a battery in accordance with the internal impedance computed by the internal impedance computation unit.

4. The battery-life determination system according to claim 3, wherein the stop unit stops

charge under constant-current charge when the value of charge current to the secondary battery is stabilized.

5. A battery for supplying power to a body by repeating charge and discharge, comprising:

an under-charge-voltage measurement unit for measuring the battery voltage under charge;

a current measurement unit for measuring the charge-current value under charge;

an under-stop-voltage measurement unit for measuring the battery voltage when charge is stopped; and

a computation unit for computing an internal impedance in accordance with the battery voltage measured by the under-charge-voltage measurement unit, the charge current value measured by the current measurement unit, and the battery voltage measured by the under-stop-voltage measurement unit.

6. The battery according to claim 5, further comprising a transmission unit for transmitting

the information about the internal impedance computed by the computation unit to the body.

7. The battery according to claim 5, further comprising a charge stop unit for temporarily

stopping charge under the constant-current charge.