Electricity: battery or capacitor charging or discharging – Battery or cell charging – With thermal condition detection
Reexamination Certificate
2000-03-16
2001-05-01
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell charging
With thermal condition detection
Reexamination Certificate
active
06225786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery charger suited for charging a battery, such as a nickel metal hydride battery, which emits high heat while being charged.
2. Discussion of the Prior Art
Presently, a battery pack housing chargeable batteries which can be repeatedly used for the power supply of, for example, a power tool is used. A nickel cadmium battery is popular as a battery for the power tool.
The inventor of the present invention studied improving the performance of a power tool by employing a nickel metal hydride battery as a battery therefor. Although the nickel metal hydride battery can increase a capacity compared with a nickel cadmium battery, it generates high heat while being charged. If the temperature of the battery becomes high by the generated heat, the electrodes and separators of the cells within the battery deteriorate and battery life is shortened. Further, the nickel metal hydride battery is less resistant against overcharge than the nickel cadmium battery. If overcharged, the battery life is shortened. It is, therefore, necessary to avoid overcharge.
Considering this, the inventor of the present invention contrived a method of controlling charging current and detecting the completion of charge based on a map for determining a current value based on the absolute temperature of the battery and a temperature rise value. With this method, however, if the number of battery cells in a battery pack increases, a battery cell positioned on the end portion of the battery pack tends to be cooled and that on the central portion thereof is difficult to cool, with the result that the completion of charge cannot be detected based on the battery temperature. Furthermore, if the temperatures of the cells in the battery pack become increasingly irregular, the life of a high temperature cell is shortened and the high temperature cell is difficult to charge. Due to this, the capacities become unbalanced among the cells and it may occur that there is a cell charged 100% and one charged 90% (high temperature cell). Here, if the capacity of the battery pack is used up to 90%, some cells have a residual capacity of 10% and the others have a residual capacity of 0% (high temperature cell). The cells of 0% residual capacity are reverse-charged by those of 10% residual capacity and the battery life is considerably shortened.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-stated problems and an object of the invention is to provide a battery charger capable of appropriately charging a battery pack including many battery cells.
In order to accomplish the said object, a battery charger dividing and charging a battery consisting of a plurality of battery cells, according to the present invention characterized by comprising:
a storage device storing a map, in which an allowable current value, with which the battery can be charged while a temperature rise of the battery is being suppressed, is mapped based on a battery temperature value and a battery temperature rise value;
a temperature detecting section for detecting a present battery temperature;
a temperature rise value outputting section for obtaining the temperature rise value from the temperature detected by said temperature detecting section;
an allowable current value retrieving section for retrieving the map of said storage device based on the temperature detected by said temperature detecting section and the temperature rise value outputted from said temperature rise value outputting section, and for obtaining said allowable current value;
a charging section for charging said divided battery with the allowable current value retrieved by said allowable current value retrieving section; and
a charge switching section for alternately switching divided blocks to be charged by said charging section.
A battery charger dividing a battery consisting of a plurality of battery cells into two or more blocks and charging the divided blocks, according to the present invention characterized by comprising:
a storage device storing a map, in which an allowable current value, with which the battery can be charged while a temperature rise of the battery is being suppressed, is mapped based on a battery temperature value and a battery temperature rise value, the allowable current value set at a low value if the battery temperature value is high and set at a low value if the temperature rise value is high;
a temperature detecting section for detecting a present battery temperature;
a temperature rise value outputting section for obtaining the temperature rise value from the temperature detected by said temperature detecting section;
an allowable current value retrieving section for retrieving the map of said storage device based on the temperature detected by said temperature detecting section and the temperature rise value outputted from said temperature rise value outputting section, and for obtaining said allowable current value;
a charging section for charging said divided battery blocks with the allowable current value retrieved by said allowable current value retrieving section;
a charge switching section for alternately switching the divided battery blocks to be charged by said charge section;
a charge completion determining section for determining completion of charge of each of the divided battery blocks based on whether frequency, with which the temperature detected by said temperature detecting section and the temperature rise value outputted from said temperature rise value outputting section belong to regions indicating a final charging period in the map of said storage device, is high; and
a charge completing section for completing charge of the divided battery blocks based on determination of completion of battery charge by said charge completion determining section.
A battery charger capable of a battery consisting simultaneously of a plurality of battery cells and dividing the battery into two or more blocks and then charging the divided battery blocks, according to the present invention characterized by comprising:
a storage device storing a map, in which an allowable current value, with which the battery can be charged while a temperature rise of the battery is being suppressed, is mapped based on a battery temperature value and a battery temperature rise value;
a temperature detecting section for detecting a present battery temperature;
a temperature rise value outputting section for obtaining the temperature rise value from the temperature detected by said temperature detecting section;
an allowable current value retrieving section for retrieving the map of said storage device based on the temperature detected by said temperature detecting section and the temperature rise value outputted from said temperature rise value outputting section, and for obtaining said allowable current value;
a charging section for charging the battery with the allowable current value retrieved by said allowable current value retrieving section; and
a charge switching section for switching said charging section and charging the battery consisting of the plurality of battery cells simultaneously or charging the battery separately, wherein
said charge switching section simultaneously charges the battery consisting of the plurality of battery cells at beginning of battery charge, and alternately switches the divided battery blocks and charges the divided battery blocks in a final charging period.
A battery charger dividing a battery consisting of a plurality of cells into two or more blocks and charging the divided battery blocks, according to the present invention characterized by comprising:
a storage device storing a map, in which an allowable current value, with which the battery can be charged while a temperature rise of the battery is being suppressed, is mapped based on a battery temperature value and a battery temperature rise value, the allowable current value set at a low value if the battery temperature value is high and set at a low value if the
Muramatsu Tomoo
Sakakibara Kazuyuki
Makita Corporation
Toplin Thomas W.
Tso Edward H.
Weslh & Katz, Ltd.
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