Method for determining battery state of charge by measuring A.C. electrical phase angle change
First Claim
1. A battery charge - discharge life cycle testing system including continuous battery state of charge monitoring comprising:
- a battery that is to be charge - discharge life cycle tested;
a shunt coupled to said battery;
a first programable load bank coupled across said shunt and said battery;
a second programable load bank coupled in series with said shunt and said battery;
a charging current power supply coupled to said battery through said second programable load bank and said shunt;
a D.C. charge level control circuit coupled to said second programable load bank;
a D.C. discharge current level control circuit coupled to said first programable load bank;
a reference voltage source having an alternating current output coupled to said D.C. discharge level control circuit, said alternating current output being applied to said battery through said D.C. discharge level control circuit, said first programable load bank and said shunt;
a first amplifier having its input coupled across said shunt and having an output;
a second amplifier having its input coupled across said battery and having an output;
a phase angle measuring circuit having a first input coupled to said output of said first amplifier, a second input coupled to said output of said second amplifier and having an output; and
a meter coupled to said output of said phase angle measuring circuit.
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Accused Products
Abstract
Several embodiments for determining the state of charge of a cell or battery are disclosed. In accordance with one method of this invention, an A.C. voltage is applied to a cell or battery through a shunt. The phase angle between the A.C. voltage across the battery terminals and the A.C. current through the battery (measured as a shunt voltage) is continuously monitored. This phase angle is converted to an analog voltage which represents the A.C. component that is phase shifted by the impedance of the battery. The impedance and thus the phase angle changes with the state of charge of the battery. The analog voltage can be coupled to a meter that provides a phase angle reading or a state of charge reading. Further, the analog voltage can be used to control charge and discharge circuitry. In accordance with a second method, the state of charge of a battery is determined by taking phase angle readings based on input and output A.C. voltages.
213 Citations
2 Claims
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1. A battery charge - discharge life cycle testing system including continuous battery state of charge monitoring comprising:
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a battery that is to be charge - discharge life cycle tested; a shunt coupled to said battery; a first programable load bank coupled across said shunt and said battery; a second programable load bank coupled in series with said shunt and said battery; a charging current power supply coupled to said battery through said second programable load bank and said shunt; a D.C. charge level control circuit coupled to said second programable load bank; a D.C. discharge current level control circuit coupled to said first programable load bank; a reference voltage source having an alternating current output coupled to said D.C. discharge level control circuit, said alternating current output being applied to said battery through said D.C. discharge level control circuit, said first programable load bank and said shunt; a first amplifier having its input coupled across said shunt and having an output; a second amplifier having its input coupled across said battery and having an output; a phase angle measuring circuit having a first input coupled to said output of said first amplifier, a second input coupled to said output of said second amplifier and having an output; and a meter coupled to said output of said phase angle measuring circuit.
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2. A battery state of charge measuring system comprising:
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a battery the state of charge of which is to be measured; a shunt resistor coupled to said battery; a load circuit and charging circuit coupled across said battery and said shunt resistor; a first amplifier having its input capacitively coupled across said shunt resistor and having an output; a second amplifier having its input capacitively coupled across said battery and having an output; a source of alternating voltage; a comparator having a first input coupled to said output of said first amplifier, a second input coupled to said reference source of alternating voltage and having an output; an error amplifier having its input coupled to said output of said comparator and having its output coupled across said shunt resistor and said battery; a phase angle to analog voltage converter having a first input coupled to said output of said first amplifier, a second input coupled to said output of said second amplifier and having an output; and a meter coupled to said output of said phase angle to analog voltage converter.
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Specification