Electricity: battery or capacitor charging or discharging – Battery or cell charging – With thermal condition detection
Reexamination Certificate
2001-01-18
2002-03-26
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
With thermal condition detection
C320S135000
Reexamination Certificate
active
06362600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery charging device for charging batteries comprised of a plurality of cells, and to a battery charging device that is capable of terminating charge upon detection of abnormalities of cells or inconveniences of the battery charging device or the like.
2. Discussion of the Prior Art
It is conventionally known to use batteries accumulating therein rechargeable cells that may be repeatedly used as power sources for power tools or the like. In order to generate a power source voltage that is required by the power tools or the like, it is general that the batteries are comprised of a plurality of cells of identical types combined either in a serial or parallel manner. Thus, it is considered that performances of the plurality of cells comprising the batteries are degraded in a substantially identical manner by repeating charge and discharge operations of the batteries.
However, since such cells comprising the batteries are arranged to generate electricity by utilizing chemical reaction in forms of nickel cadmium batteries or nickel metal hydride batteries, electric characteristics at the time of charge and discharge are widely varied so that it is extremely difficult to achieve an arrangement in which charge/discharge characteristics of a plurality, for instance, more than ten of cells are adjusted to be identical. It may thus happen that charge/discharge characteristics of some of the cells comprising the batteries remarkably differ from those of other cells upon repeatedly using the batteries. The possibilities that such cells degrade in performances prior than other cells is accordingly high.
It is not only through chemical factors but also through environments for using the power tools or the like that a part of the cells comprising the batteries is mechanically damaged when oscillation or shock is applied on the batteries that exceeds a presumed level or when the user erroneously drops the batteries. It may be that such mechanically damaged cells are degraded in performances when compared with other cells.
However, a battery charging device for charging batteries comprised of such cells generally employs a method of performing charge of all of the plurality of cells comprising the batteries in one lump sum. Thus, partial degradations in performances can be hardly conceived from the charge characteristics of the batteries as a whole even if a part of the cells should be degraded in performances, and it had so far been difficult to detect whether the plurality of cells comprising the batteries included cells with degraded performances. Though it may seem that it is possible to cope with such problems by providing a breakdown detecting circuit for each of the plurality of cells comprising the batteries, such a measure lacks in practicability since it would not only lead to a complicated circuit arrangement for the batteries and the battery charging device but would also increase costs for manufacturing the batteries and other members.
In a battery charging device employing a method of performing charge upon dividing the plurality of cells into two or more groups of cells, charge is individually performed by dividing the plurality of groups of cells further into two or more. Due to this arrangement, it is generally the case that a circuit for detecting inconveniences that may be generated in the charging circuit or the like is provided on the battery charging device side for detecting such inconveniences, while this arrangement provides a drawback in view of circuit arrangement, namely that the circuit arrangement for the battery charging device becomes complicated.
SUMMARY OF THE INVENTION
The present invention has thus been made for solving the above drawbacks, and it is an object thereof to provide a battery charging device that is capable of terminating charge upon detection of abnormalities of cells comprising batteries through a simply arrangement.
It is another object of the present invention to provide a battery charging device that is capable of terminating charge upon detection of inconveniences of the battery charging device or the like through a simply arrangement.
In order to achieve the above objects, according to the present invention, a battery charging device for charging batteries comprised of a plurality of cells, the battery charging device comprising:
a temperature detecting portion for detecting cell temperatures during charging operations within groups of cells for each of groups of cells in which a plurality of cells has been divided into two or more,
a comparing portion for comparing the cell temperature of one group of cells with that of another group of cells,
a determining portion for determining whether a temperature difference between the cell temperatures as compared by the comparing portion is exceeding a specified value or not, and a control portion for terminating charge when it is determined by the determining portion that the temperature difference between cell temperatures is exceeding the specified value.
In order to achieve the above objects, according to the present invention, a battery charging device for performing charge of batteries comprised of a plurality of cells upon dividing the cells into two or more groups of cells, the battery charging device comprising:
a temperature detecting portion for detecting cell temperatures during charging operations within groups of cells for each of groups of cells,
a comparing portion for comparing the cell temperature of one group of cells with that of another group of cells,
a determining portion for determining whether a temperature difference between the cell temperatures as compared by the comparing portion is exceeding a specified value or not, and a control portion for terminating charge when it is determined by the determining portion that the temperature difference between cell temperatures is exceeding the specified value.
In an invention, a temperature detecting portion detects cell temperatures within groups of cells in charging operations for each of groups of cells in which a plurality of cells has been divided into 2 or more, a comparing portion compares the cell temperature of one group of cells with that of another group of cells, a determining portion determines whether a temperature difference between cell temperatures as compared by the comparing portion is exceeding a specified value or not, and when it is determined by the determining portion that the temperature difference between cell temperatures is exceeding the specified value, charging of the batteries is terminated by a control portion. More particularly, charging of the batteries is terminated when it is determined that the temperature difference between the cell temperature of one group of cells and the cell temperature of another group of cells is exceeding a specified value. In this manner, by performing determination of cell temperature differences during charging operations through a relatively simple arrangement comprised of the temperature detecting portion, the comparing portion, determining portion and the control portion, it is possible to detect a group of cells including cells whose temperature does not rise or fall within a specified range similarly to remaining cells within the same group of cells, that is, abnormal cells and to terminate charging of the batteries.
In an invention, a temperature detecting portion detects cell temperatures within groups of cells in charging operations for each of groups of cells in which a plurality of cells has been divided into 2 or more, a comparing portion compares the cell temperature of one group of cells with that of another group of cells, a determining portion determines whether a temperature difference between cell temperatures as compared by the comparing portion is exceeding a specified value or not, and when it is determined by the determining portion that the temperature difference between cell temperatures is exceeding the specified value, charging of the batteries is
Luk Lawrence
Lyon & Lyon LLP
Makita Corporation
Wong Peter S.
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