Battery monitor apparatus

• US 6,268,710 B1
• Filed: 03/31/2000
• Issued: 07/31/2001
• Est. Priority Date: 07/09/1999
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Koga, Kazunobu
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): TOATLEY, GREGORY J
• Application Number:
  US09/539,626
• Time in Patent Office: 487 Days
• Field of Search: 320/116, 320/117, 320/120, 320/121, 320/162, 320/166, 324/433, 324/434
• US Class Current: 320/116
• CPC Class Codes: G01R 31/3842 combining voltage and current measurements
• 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
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/0014 Circuits for equalisation of charge between batteries
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]

Abstract

A battery monitor apparatus for monitoring the voltage of each cell of a battery pack including a plurality of cells is disclosed, in which each cell of the battery pack having the plurality of cells is connected to a capacitor by a switch, so that the cell voltage is retrieved and measured, and the current is detected, thereby making it possible to control the charge/discharge of each cell. This apparatus includes a capacitor, a switch group for connecting the ends of an arbitrary one of the cells constituting the battery pack or the ends of an arbitrary plurality of the cells to the capacitor thereby to retrieve the voltage of one cell or a plurality of the cells, and a detector for detecting the voltage of the capacitor.

Claims

1. A battery monitor apparatus for monitoring at least the voltage of each cell of a battery pack including a plurality of cells, comprising:

a capacitor;

a group of switches for connecting the ends of one arbitrary cell or the ends of a plural cells fewer in number than all the cells constituting said battery pack to said capacitor and retrieving the voltage of said one cell or said plural cells; and

a detector for detecting the voltage of said capacitor.

2. A battery monitor apparatus according to claim 1,

wherein the voltage retrieved from the ends of said capacitor is divided by resistors to a voltage equivalent to a single stage of all the stages of the cells from which the voltage is retrieved, and the analog voltage after said division is converted into a digital voltage.

3. A battery monitor apparatus according to claim 1,

wherein a part of an arbitrary number of plural stages of cells with the voltage thereof divided into a voltage equivalent to the voltage of one of the stages of said arbitrary cells is connected to said capacitor by said switch group thereby to retrieve the voltage of said plural cells substantially as the voltage of a single cell.

4. A battery monitor apparatus according to claim 1,

wherein the ends of one or plural cells making up said battery pack are connected to said capacitor sequentially for all the cells by said switch group, said detector thus detects the voltage of said one or said plural cells sequentially, and the voltage of said battery pack is calculated based on the voltage thus detected.

5. A battery monitor apparatus according to claim 1,

wherein said detector is a voltage follower circuit, and the current is prevented from leaking as far as possible at the time of detection of the voltage across said capacitor.

6. A battery monitor apparatus according to claim 1,

wherein the ends of the cell detected by said detector to be lower in voltage than a specified value are connected to the ends of a charge power supply by said switch group, thereby charging said charge power supply.

7. A battery monitor apparatus according to claim 1,

wherein the ends of the cell detected by said detector to be higher in voltage than a specified value are connected to the ends of a charge power supply by said switch group, thereby discharging said charge power supply.

8. A battery monitor apparatus according to claim 1,

wherein said capacitor has a minimum capacity at which said detector can detect a voltage.

11. A battery monitor apparatus according to claim 1,

further comprising control means for outputting a signal indicating the end of discharge for each cell based on the voltage of each cell detected by said detector or said voltage and the current flowing in said cell.

12. A battery monitor apparatus according to claim 1,

further comprising control means for outputting a signal indicating the end of charge for each cell based on the voltage of each cell detected by said detector or said voltage and the current flowing in said cell.

13. A battery monitor apparatus according to claim 1,

further comprising control means for outputting a signal indicating the deterioration or fault of each cell based on the voltage of said cell detected by said detector or said voltage and the current flowing in said cell.

14. A battery monitor apparatus according to claim 1 or 9,

further comprising a current measuring circuit for measuring the current flowing through a resistor in each cell train including a plurality of cells connected in series, a plurality of said cell trains being connected in parallel.

15. A battery monitor apparatus according to claim 1,

wherein the input terminal of said detector is connected to a predetermined voltage as required for detecting and storing an offset value of said detector thereby to correct the offset of the voltage detected by said detector.

16. A battery monitor apparatus according to claim 1,

wherein the remaining capacity and/or the remaining life of each cell is determined and/or displayed for each cell based on the voltage of each cell detected by said detector and said voltage and the current flowing in said cell.

17. A battery monitor apparatus according to claim 1 or 9,

wherein said switch group is a group of analog switches.

9. A battery monitor apparatus for monitoring at least the voltage of each cell of a battery pack including a plurality of cells, comprising:

a capacitor;

a group of switches for connecting the ends of an arbitrary single cell or the ends of a plural cells fewer in number than all the cells constituting said battery pack to said capacitor and retrieving the voltage of said single cell or said plural cells;

a comparator circuit for comparing the voltage of said capacitor with a predetermined reference voltage and detecting the normal state, the over-charge state or the over-discharge state; and

a circuit for storing said normal state, said over-charge state or said over-discharge state.

10. A battery monitor apparatus according to claim 9,

further comprising a circuit for storing an over-charge state or an over-discharge state in synchronism with the detection of said over-charge state or said over-discharge state, as the case may be, for each single cell or plural cells individually and subsequently adding a hysteresis voltage individually to said predetermined reference voltage.

18. A battery monitor apparatus according to claim 9,

further comprising a voltage monitor for displaying the normal charge/discharge, over-charge or over-discharge state and the voltage detected for each cell or plurality of said cells.

19. A battery monitor apparatus according to claim 9,

further comprising a protection circuit for stopping the charge or discharge upon detection of an over-charge or an over-discharge, as the case may be, for each cell or for plurality of said cells.