Methods of controlling the application and termination of charge to a rechargeable battery
First Claim
1. A method of charging a rechargeable battery having a voltage characteristic that varies in a predetermined manner with a charge state of the battery and for terminating said charging of the battery in response to the charge state of the battery when the battery has attained a full charge, comprising the steps of:
- supplying electrical energy to the battery for charging of the battery;
monitoring said voltage characteristic of the battery as said electrical energy is supplied to the battery;
differentiating a variation of the monitored voltage characteristic with time as said electrical energy is supplied to the battery to provide a slope characteristic that decreases as a function of time to a bottom peak followed by a top peak followed by a decreasing slope;
identifying in said slope characteristic a minimum slope of said bottom peak as said electrical energy is supplied to the battery; and
terminating said supplying of electrical energy to the battery when said slope characteristic equals said minimum slope as said slope characteristic decreases following said top peak.
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Accused Products
Abstract
As a substantially constant charge current is applied to a battery, the voltage is periodically measured and the slope of the voltage characteristic is calculated. The minimum slope of the bottom peak of the slope profile is dynamically identified and, as appropriate, updated and stored. With each identification and update of the minimum slope, a trigger threshold between the minimum slope and top peak is defined, and then stored, by adding a trigger value to the minimum slope. A termination threshold or value between the minimum slope and the trigger threshold may also be calculated and stored with each such identification and update of the minimum slope. When the calculated slope, increasing from the bottom peak, reaches the trigger threshold, the method is armed--as by setting a trigger threshold flag--so that when the calculated slope thereafter once again passes through the trigger threshold and then reaches the termination threshold, full-current charging of the battery is terminated. The termination threshold--which identifies the substantially fully-charged state of the battery--may, in some forms of the invention, be preset to equal the minimum slope value. Premature termination resulting from a high impedance spike or inflection point occurring in the voltage profile when charging current is initially applied to the battery may be avoided by gradually increasing the applied charging current at the beginning of the charging process.
52 Citations
52 Claims
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1. A method of charging a rechargeable battery having a voltage characteristic that varies in a predetermined manner with a charge state of the battery and for terminating said charging of the battery in response to the charge state of the battery when the battery has attained a full charge, comprising the steps of:
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supplying electrical energy to the battery for charging of the battery; monitoring said voltage characteristic of the battery as said electrical energy is supplied to the battery; differentiating a variation of the monitored voltage characteristic with time as said electrical energy is supplied to the battery to provide a slope characteristic that decreases as a function of time to a bottom peak followed by a top peak followed by a decreasing slope; identifying in said slope characteristic a minimum slope of said bottom peak as said electrical energy is supplied to the battery; and terminating said supplying of electrical energy to the battery when said slope characteristic equals said minimum slope as said slope characteristic decreases following said top peak. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method of charging a rechargeable battery having a voltage characteristic that varies in a predetermined manner with a charge state of the battery and for terminating said charging of the battery in response to the charge state of the battery when the battery has attained a full charge, comprising the steps of:
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applying a substantially constant current to the battery; monitoring said voltage characteristic as said substantially constant current is applied to the battery; calculating a slope defining a variation of said monitored voltage characteristic with time to provide a slope characteristic which, as the battery is charged, decreases as a function of time to a bottom peak followed by a top peak followed by a decreasing slope; identifying from said calculated slope a minimum slope of said bottom peak as said substantially constant current is applied to the battery; defining a trigger threshold by adding a trigger value to said minimum slope; identifying a first passage of said slope characteristic through said trigger threshold following the identifying of said minimum slope; identifying a second passage of said slope characteristic through said trigger threshold following the identifying of said minimum slope; and terminating said applying of said substantially constant current to the battery when said calculated slope equals a termination threshold after said second passage of the slope characteristic through said trigger threshold.
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18. A method of charging a rechargeable battery having a voltage characteristic that varies in a predetermined manner with a charge state of the battery and for terminating said charging of the battery in response to the charge state of the battery when the battery has attained a full charge, comprising the steps of:
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(a) supplying electrical energy to the battery for charging of the battery; (b) monitoring said voltage characteristic of the battery as said electrical energy is supplied to the battery; (c) differentiating a variation of the monitored voltage characteristic with time as said electrical energy is supplied to the battery to provide a slope characteristic that decreases as a function of time to a bottom peak followed by a top peak followed by a decreasing slope; (d) identifying in said slope characteristic a minimum slope of said bottom peak as said electrical energy is supplied to the battery; (e) defining a trigger threshold by adding a predetermined trigger value to said minimum slope; and (f) terminating said supplying of electrical energy to the battery when said slope characteristic equals a termination value as said slope characteristic decreases following said top peak, said termination value being in a range defined between said minimum slope and said trigger threshold. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. In a method of charging a rechargeable battery having a voltage characteristic that varies in a predetermined manner with a charge state of the battery and for terminating said charging of the battery in response to the charge state of the battery when the battery has attained a full charge, a method of initiating application of charge to the battery prior to supplying electrical energy to the battery at a substantially constant, predetermined charge rate at which the battery is to be charged until said termination of battery charging in response to the charge state of the battery when the battery has attained a full charge, comprising the steps of:
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(a) initially applying electrical energy to the battery at an initiating charge rate comprising a non-zero fraction of said predetermined charge rate; and (b) gradually increasing the rate at which electrical energy is applied to the battery from said initiating charge rate to said predetermined charge rate over a selected time interval of less than approximately 15 percent of a period necessary to fully charge the battery at said predetermined charge rate. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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Specification