Circuit for monitoring cells of a multi-cell battery during charge

• US 6,417,646 B1
• Filed: 05/22/2001
• Issued: 07/09/2002
• Est. Priority Date: 05/22/2001
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Huykman, Richard B., Singh, Harmohan
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/862,228
• Time in Patent Office: 413 Days
• Field of Search: 320/116, 320/118, 320/119, 320/120, 320/122, 320/162
• US Class Current: 320/122
• CPC Class Codes: G01R 19/16542 for batteries charge condition monitoring in G01R31/36
• 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 circuit (M) to monitor and protect individual cells (12-1 . . . 12-n) of a multi-cell battery (10) from over-charge and acquire data to be used to determine various characteristics of the cell state-of-health is connected to each individual cell (12) of a multi-cell battery as the battery is being charged. The circuit includes a portion (Q1-R5) to bypass charging current from the cell, this portion being variably pre-settable to bypass current above a desired high voltage (V-By) limit for the cell. As the battery is being charged, the bypass circuit will shunt current around a cell when the preset high voltage level is exceeded, thus preventing any damage to the cell. The circuit (Q2) can be operated to produce a pulse of current and the change in voltage of the monitored cell in response to the change in current, dV/dl, can be used to determine the cell internal resistance. The cell polarization resistance also can be determined. The data acquired can be used to determine factors relating to the cell state of charge (SOC) and its state of health. A programmable controller (C) controls all of the circuits and also acquires the data produced by the circuits.

Claims

1. A circuit to monitor a cell of a multi-cell battery that is being charged from a current source, comprising:

means for variably setting a predetermined high limit voltage for the cell during its charging;

a first amplifier connected to the cell for receiving as one input the voltage of the cell as the battery is being charged and said high limit voltage as another input, said first amplifier producing an output signal upon the cell voltage exceeding the high voltage limit; and

a bypass circuit connected to the cell that is activated by receiving the output signal produced by said first amplifier to bypass the charging current around said cell.

2. A circuit as in claim 1 wherein said bypass circuit comprises a resistor through which the current bypassed flows, and further comprising:

a second amplifier connected to said resistor to produce an output voltage corresponding to the magnitude of the bypass current.

3. A circuit as in claim 1 wherein said first amplifier further comprises a voltage divider connected across the cell and said one input to said first amplifier is taken from a point on said voltage divider.

4. A circuit as in claim 1 wherein said means for variably setting said predetermined high limit level voltage comprises a programmable controller.

5. A circuit as in claim 2 further comprising:

switching means for operating said bypass circuit to produce a pulse of discharge current;

a third amplifier connected across the cell to measure the cell voltage in response to the current pulse; and

means receiving the output of said second amplifier and said third amplifier for determining the internal resistance of the cell as a function of the magnitude of the bypass current pulse and the cell voltage response.

6. A circuit as in claim 5 wherein said switching means operates to extend the current pulse for a time after the cell internal resistance is determined, said circuit further comprising means for using the outputs of said second amplifier and said third amplifier to determine the cell polarization resistance.

7. A circuit as in claim 5 further comprising:

a controller for operating said switching means.

8. A circuit as in claim 7 wherein said switching means comprises:

a light source operated by said controller to produce light of a duration corresponding to the duration of the current pulse, and an opto-coupler responsive to the light to produce a signal to operate said first amplifier to activate said bypass circuit.

9. A circuit as in claim 8 wherein said first amplifier further comprises a voltage divider connected across the cell and said one input to said first amplifier is taken from a point on said voltage divider, and wherein said opto-coupler is connected across a part of said voltage divider to operate said first amplifier to produce its output signal.

10. A circuit as in claim 5 further comprising second switching means connected to said first amplifier to prevent said first amplifier from producing its output signal for activating said current bypass circuit;

and

a controller for operating said second switching means.

11. A circuit as in claim 10 wherein said second switching means comprises:

a light source operated by said controller to produce light; and

an opto-coupler responsive to the light to produce a signal to operate said first amplifier to prevent said first amplifier means from producing its output signal.

12. A circuit as in claim 11 wherein said first amplifier further comprises a voltage divider connected across the cell and said one input to said first amplifier is taken from a point on said voltage divider, and wherein said opto-coupler is connected across a part of said voltage divider to operate said first amplifier to prevent production of its output signal.

13. A circuit to monitor an individual cell or a multi-cell battery, said multi-cells being serially connected to a current source, and said circuit comprising

a first amplifier having power inputs connected to both terminals of the individual cell to be monitored, and

a second amplifier having one power input connected to a cell serially above said individual cell and having a second power input connected to a cell serially below said individual cell to provide a dynamic operating range for said first amplifier, having a signal input for determining the high voltage limit for said individual cell, and having an output connected to a signal input of said first amplifier.

14. A circuit in accordance with claim 13 further comprising a bypass circuit connected across said individual cell, said bypass circuit including a resistor and a bypass switch connected to the output of said second amplifier.

15. A circuit in accordance with claim 14 further comprising a third amplifier connected across said resistor.

16. A circuit in accordance with claim 14 further comprising a voltage divider connected across said individual cell to be monitored, said first amplifier having a further signal input connected to a point on said voltage divider.

17. A circuit in accordance with claim 16 further comprising first and second switch means connected to said voltage divider for operating or preventing operation of said first amplifier.

18. A circuit in accordance with claim 17 wherein said first and second switch means each comprise an opto-coupler connected across a portion of said voltage divider.

19. A circuit in accordance with claim 13 further comprising a network of a parallel connected resistor and capacitor connected between the output of said first amplifier and said signal input of said first amplifier to which the output of said second amplifier is connected.