Apparatus and method for measuring battery condition
First Claim
1. A battery monitor comprising:
- a. an AC signal generator adapted to generate an AC signal at a selected frequency;
b. means for applying the AC signal across a first pair of contacts of a battery;
c. means for determining first and second Ohms-law-related parameters indicative of impedance across a second pair of contacts of the battery, said determining means comprising;
first means for supplying a first input signal indicative of the first Ohms-law-related parameter;
first filter means coupled to the first supplying means for passing components of the first input signal at the selected frequency and for attenuating at least components of the first input signal in a first attenuation frequency range greater than the selected frequency, said filter means operating to generate a first filtered output signal; and
first means for measuring said first filtered output signal to determine said first Ohms-law-related parameter.
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Accused Products
Abstract
A testing device measures the impedance of secondary cells that form a battery, such as a lead acid battery, while the battery is in a float charge condition and connected to an active electrical load. The impedance measurement is made at a frequency selected to be different from those frequencies otherwise present in the charger-load circuit. A first application of the testing device monitors the battery for a change in impedance that can signal a developing defect in one or more individual cells or intercell connections that can prevent the battery from delivering its stored energy to the load. In a second application, the testing device is used to compare the impedance of individual cells and electrical connections to locate faulty components.
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Citations
47 Claims
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1. A battery monitor comprising:
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a. an AC signal generator adapted to generate an AC signal at a selected frequency; b. means for applying the AC signal across a first pair of contacts of a battery; c. means for determining first and second Ohms-law-related parameters indicative of impedance across a second pair of contacts of the battery, said determining means comprising; first means for supplying a first input signal indicative of the first Ohms-law-related parameter; first filter means coupled to the first supplying means for passing components of the first input signal at the selected frequency and for attenuating at least components of the first input signal in a first attenuation frequency range greater than the selected frequency, said filter means operating to generate a first filtered output signal; and first means for measuring said first filtered output signal to determine said first Ohms-law-related parameter. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A battery monitor for a battery which is electrically interconnected with both a battery charger and an active load, wherein said battery charger and said active load cause AC currents in said battery at a plurality of characteristic frequencies, and wherein the battery comprises a plurality of terminals, said battery monitor comprising:
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a. an AC signal generator operative to generate an AC signal at a selected frequency, different from all of the characteristic frequencies; b. means for applying said AC signal across a first pair of terminals included in said plurality of terminals; c. means for supplying a first input signal characteristic of current flowing through the battery; d. means for measuring the first input signal to determine said first Ohms-law-related parameter characteristic of battery impedance at said selected frequency across a second pair of terminals included in said plurality of terminals, said measuring means comprising a first filter means operative to pass AC components of said first input signal at the selected frequency and to attenuate AC components of said first input signal in an attenuating frequency range which includes the plurality of characteristic frequencies and which extends at least above the selected frequency; and e. means for determining a second Ohms-law-related parameter characteristic of battery impedance at said selected frequency across said second pair of terminals. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A battery monitor for a battery which is electrically interconnected with both a battery charger and an active load, wherein said battery charger and said active load cause AC currents in said battery at a plurality of characteristic frequencies, and wherein the battery comprises a plurality of terminals, said battery monitor comprising:
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a. an AC signal generator operative to generate an AC signal at a selected frequency, different from all of the characteristic frequencies; b. means for applying said AC signal across a first pair of terminals included in said plurality of terminals; c. an ammeter coupled to said applying means to generate a current measurement indicative of the magnitude of the AC current applied to the battery at said selected frequency, said ammeter comprising; means, coupled to the applying means, for developing a first input signal indicative of the magnitude of current applied to the battery by the AC signal generator; a first bandpass filter centered on said selected frequency and operative to pass components of the first input signal at said selected frequency and to attenuate components in an attenuating range which extends above and below said selected frequency range and which includes said plurality of characteristic frequencies; and means for measuring the magnitude of the first input signal as filtered by the first bandpass filter; d. a voltmeter coupled to said battery to generate a voltage measurement indicative of the magnitude of the AC voltage across a second pair of terminals of the battery, said voltmeter comprising; means, coupled to the second pair of terminals, for developing a second input signal indicative of the voltage across the second pair of terminals; a second bandpass filter centered on said selected frequency and operative to pass components of said second input signal at said selected frequency and to attenuate components in said attenuating frequency range; and means for measuring the magnitude of the second input signal as filtered by the second bandpass filter. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A method for comparing the impedance of a plurality of components of a battery while said battery is electrically connected to a charger and an active load, said battery comprising a pair of battery output terminals and a plurality of cells electrically connected between the battery output terminals, each of said components comprising a pair of electrical contacts, said method comprising the following steps:
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a. passing an AC current of a known magnitude through the battery across the battery output terminals, said AC current having a selected frequency; b. obtaining a first voltage signal indicative of the AC voltage across the pair of electrical contacts of a first one of the components; c. passing the first voltage signal through a filter operative to pass components of the first voltage signal at the selected frequency and to attenuate components of the first voltage signal in an attenuation frequency range which includes frequencies greater than the selected frequency; d. measuring the first voltage signal as filtered in step (c) to obtain a first voltage measurement; e. combining the first voltage measurement with the known magnitude of the current to obtain a first impedance value; f. repeating steps (b) through (e) with a second voltage signal indicative of the AC voltage across the pair of electrical contacts of a second one of the components to obtain a second impedance value; and g. comparing the first and second impedance values. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47)
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Specification