Method and apparatus for monitoring the voltage of a battery

• US 8,164,307 B2
• Filed: 05/27/2005
• Issued: 04/24/2012
• Est. Priority Date: 05/27/2005
• Status: Active Grant

• Current Assignee: Savi Technology Incorporated
• Original Assignee: Savi Technology Incorporated
• Inventors: Cargonja, Nikola, Chan, Joseph S., Ahn, Don H.
• Primary Examiner(s): Zhang, Jue
• Application Number:
  US11/139,428
• Publication Number:
  US 20060267554A1
• Time in Patent Office: 2,524 Days
• Field of Search: 320/130, 320/131, 320132-136, 324/433
• US Class Current: 320/132
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/3835 involving only voltage measurements

Abstract

One aspect of the invention involves: monitoring a voltage of a battery over time; evaluating whether a rate of voltage decrease of the battery is in excess of a threshold; and indicating that the battery is subject to a low voltage condition when the rate of voltage decrease exceeds the threshold. Another aspect of the invention involves: causing a circuit powered by a battery to respond to battery replacement by thereafter applying a selected load to the battery during a selected time interval. A further aspect involves: periodically sampling a voltage of a battery; and applying a load to the battery during a selected time interval before each sampling of the battery voltage.

Claims

1. A method comprising:

monitoring a voltage of a battery over time;

evaluating whether a rate of voltage decrease of said battery is in excess of a threshold; and

indicating that said battery is subject to a low voltage condition when said rate of voltage decrease exceeds said threshold;

wherein said monitoring of said voltage over time includes;

monitoring an ambient temperature; and

normalizing measured voltage values as a function of the ambient temperature.

2. A method according to claim 1, including providing a radio frequency identification tag that includes and is powered by said battery, said tag having an antenna, and having a circuit that includes a transmitter coupled to said antenna, said circuit transmitting through said transmitter and said antenna a radio frequency signal that indicates whether a determination has been made that said battery is subject to a low battery condition.

3. A method according to claim 1, including selecting a lithium cell to serve as said battery.

4. A method comprising:

monitoring a voltage of a battery over time;

evaluating whether a rate of voltage decrease of said battery is in excess of a threshold; and

indicating that said battery is subject to a low voltage condition when said rate of voltage decrease exceeds said threshold;

wherein said monitoring includes;

tracking the drain of charge from said battery;

determining a series of points in time for which a substantially equal amount of charge is drained from said battery between each pair of successive said points in time;

sampling said voltage of said battery at each of said points in time;

calculating the difference between said voltage samples from successive said points in time; and

comparing said calculated difference to said threshold.

5. A method according to claim 4, including applying a load to said battery for a selected time interval before each said sampling of said voltage of said battery.

6. A method according to claim 4, including providing a radio frequency identification tag that includes and is powered by said battery, said tag having an antenna, and having a circuit that includes a transmitter coupled to said antenna, said circuit transmitting through said transmitter and said antenna a radio frequency signal that indicates whether a determination has been made that said battery is subject to a low battery condition.

7. A method according to claim 4, including selecting a lithium cell to serve as said battery.