Apparatus and method for charging batteries
First Claim
1. An apparatus for charging a rechargeable battery that has a voltage that varies with its state of charge, the apparatus comprising:
- charging means for delivering electrical energy to the battery at a controllably-variable charging rate;
measurement means for providing periodic measurements of battery voltage; and
control means for detecting any change in value between successive battery voltage measurements and conditioning the charging means to decrease the charging rate if the detected voltage change is negative, increase the charging rate up to a predetermined maximum rate if the detected voltage change is positive, and decrease to zero the charging rate after initially detecting a negative voltage change and subsequently detecting a positive voltage change.
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Accused Products
Abstract
A charging system monitors the rate of change in battery voltage, adjusts the rate of charging, and checks the changes in battery voltage following adjustments in the rate of charging to observe a predetermined sequence of voltage changes that signifies when a battery is fully charged. The charging system determines the slope between consecutive battery voltage measurements. The charging system charges a battery at the full battery capacity in response to positive or zero voltage slope measurements and reduces the charging rate in response to negative voltage slope measurements. A nickel-cadmium battery is fully charged when at least one sequence of a negative slope, followed by a decrease in charging rate, then a positive or flat slope, followed by an increase in charge rate, and finally another negative slope is observed.
208 Citations
23 Claims
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1. An apparatus for charging a rechargeable battery that has a voltage that varies with its state of charge, the apparatus comprising:
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charging means for delivering electrical energy to the battery at a controllably-variable charging rate; measurement means for providing periodic measurements of battery voltage; and control means for detecting any change in value between successive battery voltage measurements and conditioning the charging means to decrease the charging rate if the detected voltage change is negative, increase the charging rate up to a predetermined maximum rate if the detected voltage change is positive, and decrease to zero the charging rate after initially detecting a negative voltage change and subsequently detecting a positive voltage change. - View Dependent Claims (2, 3, 8)
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4. An apparatus for charging a rechargeable battery that has a voltage that varies with its state of charge, the apparatus comprising:
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charging means for delivering a variable amount of electrical energy to the battery and charging it; measurement means for providing a measure of battery voltage, wherein the measurement means includes digital conversion means for periodically obtaining a plurality of battery voltage measurements during a measurement period and selecting one of the values obtained in the period as the measure of battery voltage to be provided; and control means for periodically receiving the measured battery voltage and changing the energy delivered to the battery by the charging means and detecting a characteristic sequence of measured-battery voltages that indicates a fully charged battery, wherein the control means decreases the electrical energy provided by the charging means by a predetermined proportion of the maximum allowable charging rate each time a change in the battery voltage indicates that the battery is near full charge. - View Dependent Claims (5, 6, 7)
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9. An apparatus for charging a rechargeable battery that has a voltage that varies with its state of charge, the apparatus comprising:
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charging means for delivering a variable amount of electrical energy to the battery and charging it; measurement means for providing a measure of battery voltage; and control means for periodically receiving the measured battery voltage and changing the energy delivered to the battery by the charging means and detecting a characteristic sequence of measured battery voltages that indicates a fully charged battery; wherein the charging means includes a constant current source that produces a predetermined current, and regulating means for switching the constant current source between an on state, in which the constant state, in which the constant current source is connected to the battery, and an off state, in which the constant current source is disconnected from the battery; and wherein the measurement means includes sample means for periodically obtaining a battery voltage reading. - View Dependent Claims (10)
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11. A battery charging apparatus for charging a first rechargeable battery that has a battery voltage that varies with the state of charge of the battery, the apparatus comprising:
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charging means for delivering a variable amount of electrical energy to the battery, at up to a predetermined maximum allowable charging rate capacity of the battery, and charging the battery; detecting means for periodically providing an indication of the battery voltage; slope means for providing a slope value that indicates whether the slope of the battery voltage curve corresponding to the previous two battery voltage indicators from the detecting means is positive, negative, or flat; and control means for receiving the slope value from the slope means, decreasing the amount of electrical energy delivered by the charging means if the slope is negative, increasing the amount of electrical energy delivered by the charging means up to the maximum allowable rate if the slope is positive or flat, and terminating the delivery of electrical energy from the charging means if the battery voltage undergoes three consecutive sequences of change from negative slope to positive or flat slope. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for charging rechargeable batteries having a battery voltage that varies with their state of charge, comprising the steps of:
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delivering electrical energy to a first battery at a rate up to a maximum allowable charging rate capacity of the battery and charging it; periodically measuring the battery voltage of the first battery and determining a slope that corresponds to the change in battery voltage between measurements; reducing the rate at which electrical energy is delivered to the first battery if the slope is negative and increasing it up to the maximum allowable rate if the slope is positive; and indicating that the first battery is at full charge after at least one sequence of determining a negative battery voltage slope, reducing the rate at which electrical energy is delivered to the first battery, determining a positive battery voltage slope, increasing the rate at which electrical energy is delivered to the first battery, and determining a negative battery voltage slope. - View Dependent Claims (21, 22, 23)
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Specification