Electricity: battery or capacitor charging or discharging – Serially connected batteries or cells
Reexamination Certificate
2000-03-31
2001-07-31
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Serially connected batteries or cells
C320S162000, C320S166000, C324S433000
Reexamination Certificate
active
06268710
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery monitor apparatus for monitoring the voltage of each cell of a battery pack configured with a plurality of cells.
2. Description of the Related Art
In the prior art, a secondary battery (a chargeable/dischargeable battery such as a lithium ion battery) is used as a battery pack (including a plurality of cells (battery cells) connected in series and parallel) for supplying power to various portable equipment. When the charge/discharge of the battery is repeated, especially of the lithium ion battery, it is necessary to monitor the voltage of the whole battery pack and the over-charge/over-discharge of each cell and to take preventive measures such as stopping the charge or discharge as required.
For this purpose, in the circuit shown in
FIG. 13A
, when an over-charge comparator circuit detects that the voltage of the whole battery pack has increased beyond a specified voltage corresponding to the number of cells constituting the battery pack at the time of charge, the charge is stopped. At the time of discharge, on the other hand, the discharge is stopped when an over-discharge comparator circuit detects that the voltage of the whole battery pack has decreased to below a specified voltage corresponding to the number of cells constituting the battery pack.
Also, in the circuit shown in
FIG. 13B
, an operational amplifier (OP amplifier) is attached to each cell making up the battery pack, so that upon detection of the potential of the positive electrode of each cell, the voltage of each stand-alone cell is calculated, by subtracting the potential of each cell sequentially in the OP amplifier, and notified to a microprocessing unit (MPU) not shown. In the event that the voltage of each stand-alone cell deviates from a specified voltage range during charge or discharge, the discharge or charge, as the case may be, is stopped, a cell voltage failure is detected, an alarm is issued or other appropriate measure is executed for controlling the prevailing state.
In spite of this requirement, the conventional circuit shown in
FIG. 13A
, though simple in configuration, harbors the problem that it is impossible to detect for each stand-alone cell whether the charge/discharge voltage for each cell has deviated from a specified range or not.
Also, in the conventional circuit shown in
FIG. 13B
, the voltage of each cell is calculated by an OP amplifier connected to each cell and other OP amplifiers for subtracting the outputs of the OP amplifiers. With the increase in the number of cells, the OP amplifiers also increase in number. Further, it is difficult to regulate the individual offsets accurately in view of the characteristics of OP amplifiers made up of analog elements. This leads to the problem that an increased number of cells increases the voltage error of each cell due to the offset error. Another problem is that the offset regulation circuit, if attached to each OP amplifier, complicates the circuit configuration greatly and requires a large space.
Still another problem is the voltage imbalance at the time of charge or discharge between a plurality of cells in series of the battery pack. Especially during charging, an over-charged cell may exist. Nevertheless, the state of each cell (over-charged or over-discharged or normal) is not detected nor displayed individually, thereby giving rise to the problem of an unknown state.
SUMMARY OF THE INVENTION
In order to solve these problems, an object of the present invention is to provide a battery monitor apparatus in which each of a plurality of cells of the battery pack is connected to a capacitor through a switch so that the cell voltage is retrieved and measured thereby to detect the current.
Another object of the invention is to control the charge and discharge for each cell.
Still another object of the invention is to detect and display the over-charged or over-discharged alarm state for each cell or for plural cells.
In order to achieve the objects described above, according to one aspect of the present invention, there is provided a battery monitor apparatus, for monitoring at least the voltage of each cell of the battery pack made up of a plurality of cells, comprising a capacitor, a group of switches for connecting the two ends of an arbitrary one of a plurality of cells making up the battery pack or the two ends of plural cells smaller in number than the total number of the cells to the capacitor thereby to retrieve the voltage of the single cell or plural cells, as the case may be, and a detector for detecting the voltage across the capacitor.
According to another aspect of the present invention, there is provided a battery monitor apparatus for monitoring at least the voltage of each one of a plurality of cells of a battery pack, comprising a capacitor, a group of switches for connecting the two ends of an arbitrary one of a plurality of cells making up the battery pack or the two ends of plural cells smaller in number than the total number of the cells to the capacitor thereby to retrieve the voltage of the single cell or the plural cells, as the case may be, a comparator circuit for detecting a normal, an over-charged or an over-discharged state by comparing the voltage of the capacitor with a predetermined reference voltage, and a circuit for storing the normal, an over-charged state or an over-discharged state.
REFERENCES:
patent: 4823086 (1989-04-01), Whitmire et al.
patent: 6121751 (2000-09-01), Merritt
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Toatley , Jr. Gregory J.
Wong Peter S.
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