Electronic battery tester
First Claim
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1. An apparatus for measuring conductance of a battery, comprising:
- a positive sense electrical connection adapted to couple to a positive terminal of the battery;
a negative sense electrical connection adapted to couple to a negative terminal of the battery;
a positive current electrical connection adapted to couple to the positive terminal of the battery;
a negative current electrical connection adapted to couple to the negative terminal of the battery;
a current source;
a current switch selectively coupling the current source between the positive current electrical connection and the negative current electrical connection;
a first capacitor connected in series with the positive sense electrical connection;
a second capacitor connected in series with the negative sense electrical connection;
a differential amplifier having a first input, a second input and a differential output;
a first switch selectively coupling the first input of the differential amplifier to the first capacitor;
a second switch selectively coupling the second input to the differential amplifier; and
control circuitry coupled to the current switch, the first switch and the second switch selectively supplying the current source to the battery by actuating the current switch and maintaining at least a momentary disconnection between the battery and the amplifier by closing the first and second switches;
the control circuitry responsively determining battery conductance as a function of differential current flow through the battery due to the applied and differential voltage drop across the battery based upon the differential output.
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Abstract
A microprocessor couples to a voltage sensor through an analog to digital converter. The voltage sensor is adapted to be coupled across terminals of a battery. A small current source is also provided and adapted to be coupled across the terminal to the battery. The current source is momentarily applied to the battery and the resulting change in voltage is monitored using the microprocessor. The microprocessor calculates battery conductance based upon the magnitude of the differential current and the change in voltage and thereby determines the condition of the battery.
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Citations
11 Claims
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1. An apparatus for measuring conductance of a battery, comprising:
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a positive sense electrical connection adapted to couple to a positive terminal of the battery;
a negative sense electrical connection adapted to couple to a negative terminal of the battery;
a positive current electrical connection adapted to couple to the positive terminal of the battery;
a negative current electrical connection adapted to couple to the negative terminal of the battery;
a current source;
a current switch selectively coupling the current source between the positive current electrical connection and the negative current electrical connection;
a first capacitor connected in series with the positive sense electrical connection;
a second capacitor connected in series with the negative sense electrical connection;
a differential amplifier having a first input, a second input and a differential output;
a first switch selectively coupling the first input of the differential amplifier to the first capacitor;
a second switch selectively coupling the second input to the differential amplifier; and
control circuitry coupled to the current switch, the first switch and the second switch selectively supplying the current source to the battery by actuating the current switch and maintaining at least a momentary disconnection between the battery and the amplifier by closing the first and second switches;
the control circuitry responsively determining battery conductance as a function of differential current flow through the battery due to the applied and differential voltage drop across the battery based upon the differential output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification