Charging device of a secondary battery for controlling termination of charging in response to the change state of terminal voltage of the secondary battery
First Claim
1. A charging device of a secondary battery for detecting terminal voltage of the secondary battery during charging for controlling termination of a charging operation, said charging device comprising:
- means for supplying a charging current to the secondary battery;
means for detecting a terminal voltage of said secondary battery;
most recent gradient calculation means for finding a most recent gradient of the terminal voltage detected by said detection means;
average gradient calculation means for finding an average gradient, for a comparatively long term, of the terminal voltage detected by said detection means;
gradient comparison means for comparing said most recent gradient with said average gradient;
voltage comparison means for comparing the most recent terminal voltage with a previously measured terminal voltage;
termination determination means responsive to outputs of said gradient comparison means and said voltage comparison means for determining termination of charging by the fact that said most recent terminal voltage becomes equal to or less than said previously measured terminal voltage at a time after said most recent gradient becomes greater than said average gradient by at least a predetermined value; and
control means responsive to said termination determination means for controlling said charging current supply means so as to stop the charging current to the secondary battery.
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Accused Products
Abstract
A control section detects terminal voltage of a battery periodically and stores it in a memory, then calculates the most recent gradient and average gradient of a charging curve from the storage contents. When the most recent gradient becomes greater than the average gradient by a predetermined value or more, the control section judges it to be the last stage of the charging. After this, the control section compares the most recent terminal voltage with the preceding terminal voltage which are detected and stored in sequence. When they become equal to each other, the control section turns off a charge switch for terminating the charging. Thus, a rise in the terminal voltage at the last stage of the charging is detected securely and the subsequent peak is detected accurately.
193 Citations
16 Claims
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1. A charging device of a secondary battery for detecting terminal voltage of the secondary battery during charging for controlling termination of a charging operation, said charging device comprising:
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means for supplying a charging current to the secondary battery; means for detecting a terminal voltage of said secondary battery; most recent gradient calculation means for finding a most recent gradient of the terminal voltage detected by said detection means; average gradient calculation means for finding an average gradient, for a comparatively long term, of the terminal voltage detected by said detection means; gradient comparison means for comparing said most recent gradient with said average gradient; voltage comparison means for comparing the most recent terminal voltage with a previously measured terminal voltage; termination determination means responsive to outputs of said gradient comparison means and said voltage comparison means for determining termination of charging by the fact that said most recent terminal voltage becomes equal to or less than said previously measured terminal voltage at a time after said most recent gradient becomes greater than said average gradient by at least a predetermined value; and control means responsive to said termination determination means for controlling said charging current supply means so as to stop the charging current to the secondary battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of charging a secondary battery for detecting terminal voltage of the secondary battery during charging for controlling termination of the charging, said charging method comprising:
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a step for detecting a terminal voltage of said secondary battery; a most recent gradient calculation step for finding a most recent gradient of the terminal voltage detected by said detection step; an average gradient calculation step for finding an average gradient, for a comparatively long term, of the terminal voltage detected by said detection step; a gradient comparison step for comparing said most recent gradient with said average gradient; a voltage comparison step for comparing the most recent terminal voltage with a previously measured terminal voltage; a termination determination step subsequent to said gradient comparison step and said voltage comparison step for determining termination of charging by the fact that said most recent terminal voltage becomes equal to or less than said previously measured terminal voltage at a time after said most recent gradient becomes greater than said average gradient by at least a predetermined value; and a control step responsive to the termination of charging determined by said termination determination step for terminating the charging current to the secondary battery.
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16. A method of charging a secondary battery comprising:
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detecting a terminal voltage of said secondary battery; calculating a most recent gradient of the terminal voltage detected by said detecting step; calculating an average gradient over a comparatively long term, of the terminal voltage detected by said detecting step; comparing said most recent gradient with said average gradient; comparing the most recent terminal voltage with a previously measured terminal voltage subsequent to said gradient comparison step and generating a termination signal in response to said most recent terminal voltage becoming equal to or less than said previously measured terminal voltage at a time after said most recent gradient becomes greater than said average gradient by at least a predetermined value; and terminating the flow of charging current to the secondary battery in response to said termination signal.
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Specification