Battery Cell Tab Monitor

• US 20110169452A1
• Filed: 01/14/2010
• Published: 07/14/2011
• Est. Priority Date: 01/14/2010
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: ZHANG, Weibiao NA, SCOTT, Kyl Wayne, COOPER, J. Randall
• Granted Patent: US 8,547,064 B2
• Time in Patent Office: Days
• US Class Current: 320/116
• CPC Class Codes: G01R 31/396 Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery

Abstract

A battery cell tab monitoring apparatus includes a conductive element electrically connected between two battery cells. The conductive element is connected to a sensing circuit including a pull-down current source connected to pull current from the conductive element and/or a pull-up current source connected to drive current into the conductive element. A voltage measuring circuit is connected to sense voltages during operation of the pull-down current source and the pull-up current source to be used to determine the status of the conductive element. For instance, voltages beyond certain fixed or variable thresholds indicate that the conductive element is flexing or cracking, which can be a precursor to its breaking. Voltages beyond other fixed or variable thresholds indicate that the conductive element is fully disconnected. The current sources used to push and pull the sensing currents may be used to bring the battery cells into balance when an imbalance is detected.

Claims

1. A battery cell tab monitoring circuit electrically connected to a conductive element electrically connected to a first battery cell and a second battery cell, the circuit comprising:

a current source connected to pull current from the conductive element or drive current into the conductive element;

a controller circuit connected to control operation of the current source;

a voltage measuring circuit connected to sense voltages during operation of the current source; and

the controller circuit connected to determine a status of the conductive element based at least in part on the voltage measurements.

2. The battery cell tab monitoring circuit of claim 1 wherein the current source comprises a pull-down current source connected to pull current from the conductive element and a pull-up current source connected to drive current into the conductive element.

3. The battery cell tab monitoring circuit of claim 2 wherein the pull-down current source comprises a first pull-down current source and a second pull-down current source and wherein the pull-up current source comprises a first pull-up current source and a second pull-up current source.

4. The battery cell tab monitoring circuit of claim 3 wherein the controller circuit operates the first pull-down current source and the first pull-up current source periodically to determine whether the conductive element electrical connection is intact.

5. The battery cell tab monitoring circuit of claim 3 wherein the controller circuit operates the second pull-down current source and the second pull-up current source periodically to monitor quality of the conductive element electrical connection.

6. The battery cell tab monitoring circuit of claim 2 wherein the controller circuit controls the pull-up current source and the pull-down current source to alternate in operation to balance load on the first battery cell and the second battery cell.

7. The battery cell tab monitoring circuit of claim 2 wherein the controller circuit compares voltages during operation of the pull-down current source to a first voltage fixed or variable threshold, and wherein the controller circuit compares voltages during operation of the pull-up current source to a second fixed or variable voltage threshold.

8. The battery cell tab monitoring circuit of claim 2 wherein the controller circuit receives information regarding relative charge of the first battery cell and the second battery cell and the controller circuit operates the pull-up current source and the pull-down current source to balance the relative charge of the first battery cell and the second battery cell.

9. A method of monitoring battery cell conditions comprising:

pulling current out of a conductive element disposed between a first battery cell and a second battery cell;

sensing a first voltage across the first battery cell while pulling current out of the conductive element;

pushing current into the conductive element disposed between the first battery cell and the second battery cell;

sensing a second voltage across the first battery cell while pushing current into the conductive element;

determining a connection status of the conductive element based at least in part on the first voltage and the second voltage.

10. The method of claim 9 wherein the pushing current into the conductive element and the pulling current out of the conductive element are alternated periodically.

11. The method of claim 9 wherein the step of determining the connection status of the conductive element based at least in part on the first voltage and the second voltage comprises comparing the first voltage to a first voltage threshold, comparing the second voltage to a second voltage threshold, and providing an indication of the connection status of the conductive element according to a function of the first voltage as compared to the first voltage threshold and the second voltage as compared to the second threshold.

12. The method of claim 9 wherein the step of determining the connection status of the conductive element based at least in part on the first voltage and the second voltage comprises comparing a difference between the first voltage and an initial voltage to a first threshold to make a first comparison, comparing a difference between the second voltage and the first voltage to a second voltage threshold to make a second comparison, and providing an indication of the connection status of the conductive element according to the first comparison and the second comparison.

13. The method of claim 9 wherein the step of pushing current into the conductive element comprises:

pushing a first current at a first interval; and

pushing a second current at a second interval.

14. The method of claim 13 wherein the step of pushing the first current at the first interval comprises pushing a current of about 1 milliampere to determine whether the conductive element is connected to a sensing circuit;

and wherein the step of pushing the second current at the second interval comprises pushing a current of about 10 microamperes to determine a degradation of the connection between the conductive element and the sensing circuit.

15. The method of claim 9 further comprising:

determining an imbalance of charge between the first battery cell and the second battery cell;

correcting the imbalance of charge between the first battery cell and the second battery cell by pushing current or pulling current via the conductive element.

16. A battery cell tab monitoring apparatus electrically connected to a conductive element electrically connected to a first battery cell and a second battery cell, the apparatus comprising:

a first pull-down current source connected to periodically pull a first current from the conductive element for a first amount of time;

a first pull-up current source connected to periodically push current approximately equal to the first current into the conductive element for approximately the first amount of time;

a second pull-down current source connected to periodically pull a second current from the conductive element for a second amount of time;

a second pull-up current source connected to periodically drive current approximately equal to the second current into the conductive element for approximately the second amount of time;

a controller circuit connected to control operation of the first pull-down current source, the first pull-up current source, the second pull-down current source, and the second pull-up current source;

a voltage measuring circuit connected to sense voltages during operation of the first pull-down current source, the first pull-up current source, the second pull-down current source, and the second pull-up current source; and

the controller circuit connected to determine a status of the conductive element based at least in part on the measured voltages such that the controller circuit compares voltages during operation of at least one of the first pull-down current source and the first pull-up current source to a first fixed or variable voltage threshold and the controller circuit compares voltages during operation of at least one of the second pull-down current source and the second pull-up current source to a second fixed or variable voltage threshold.

17. The battery cell tab monitoring apparatus of claim 16 wherein the controller circuit receives information regarding relative charge of the first battery cell and the second battery cell and the controller circuit operates the second pull-up current source and the second pull-down current source to balance the relative charge of the first battery cell and the second battery cell.

18. The battery cell tab monitoring apparatus of claim 16 wherein the first current comprises about 1 milliampere of current and the second current comprises about 10 microamperes of current.

19. The battery cell tab monitoring apparatus of claim 16 wherein the first pull-down current source and the first pull-up current source are controlled by at least one hardware based controller and wherein the second pull-down current source and the second pull-up current source are controlled by at least one firmware based controller.