Device for detecting failure of battery cells by comparing the second derivative of battery voltage overtime with a preset threshold
First Claim
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1. A device for detecting failure of at least one battery cell of a battery comprising a plurality of cells connected in series, said device comprising:
- voltage measuring means for measuring the voltage at terminals of said battery during discharge of the battery;
computing means, connected to said voltage measuring means, for computing a quantity representative of the second derivative of said voltage over time;
comparing means, connected to said computing means, for comparing said quantity with a preset, positive or nil, threshold that is indicative of a change in sign of the second derivative; and
failure indicating means, connected to said comparing means, for indicating said failure when said quantity is greater than said threshold.
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Abstract
Failure of one or more battery cells, for example of an inverter battery bank, is detected by monitoring the second derivative of the curve U(t) representative of the voltage U at the terminals of the battery in the course of discharge. If the second derivative is positive, this is significant of a failure.
31 Citations
7 Claims
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1. A device for detecting failure of at least one battery cell of a battery comprising a plurality of cells connected in series, said device comprising:
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voltage measuring means for measuring the voltage at terminals of said battery during discharge of the battery; computing means, connected to said voltage measuring means, for computing a quantity representative of the second derivative of said voltage over time; comparing means, connected to said computing means, for comparing said quantity with a preset, positive or nil, threshold that is indicative of a change in sign of the second derivative; and failure indicating means, connected to said comparing means, for indicating said failure when said quantity is greater than said threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A device for detecting failure of at least one battery cell of a battery comprising a plurality of cells connected in series, said device comprising:
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voltage measuring means for measuring the voltage at terminals of said battery during discharge of the battery; computing means, connected to said voltage measuring means, for computing a quantity representative of the second derivative of said voltage over time; comparing means, connected to said computing means, for comparing said quantity with a preset, positive or nil, threshold; failure indicating means, connected to said comparing means, for indicating said failure when said quantity is greater than said threshold; current measuring means for measuring discharge current of the battery; power computing means, connected to said voltage and current measuring means, for computing power delivered by the battery; storing means, connected to aid power computing means, for storing power delivered by the battery; difference computing means, connected to said power computing means and to aid storing means, for computing the power difference between two successive power values; means, connected to said difference computing means, for comparing said power difference with a preset power threshold; and inhibiting means for inhibiting said failure indicating means if said power difference is greater than said power threshold.
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Specification