High sensitivity battery resistance monitor and method therefor
First Claim
1. A method for detecting a deteriorating condition in a plurality of serially connected batteries utilized as a bank of standby batteries coupled in parallel to a battery charger and a DC powered load between a first and a second battery bus comprising the steps of:
- providing a first audio frequency current transformer for injecting a predetermined signal current and a second audio frequency current transformer for sensing a resultant current signal;
injecting an audio frequency current as said predetermined signal current via said first audio frequency current transformer into one of said first and second battery busses;
detecting a current signal at said audio frequency and carried by said one battery bus as said resultant current signal via said second audio frequency current transformer and generating a representative current signal which is related to said injected audio frequency current signal;
detecting a voltage drop, at said audio frequency, across said first and second battery busses and generating a representative voltage signal which is related to said injected audio frequency current signal;
when said bank of standby batteries is in a normal, stable operating condition, not when said bank is in a recharging state nor when said bank is supplying DC power to said load in a discharging state, establishing a differential relationship between the representative voltage and the representative current signals; and
,determining when said differential relationship exceeds at least one predetermined value and issuing an alarm signal thereat.
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Abstract
The method and the apparatus for detecting a deteriorating condition in a bank of standby batteries includes injecting an audio frequency current into one of the battery buses or cables, detecting an audio frequency current signal, matched to the injected audio frequency current signal, that is carried by the battery bus and detecting a voltage drop, at the audio frequency, across the bank of standby batteries. In one embodiment, current transformers are utilized in connection with an oscillator (to inject the AF current signal) and detection circuits (comparators and operational amplifiers) are utilized to generate a representative current signal and a representative voltage signal. The device detects when the standby batteries are operating in a normal, stable condition, that is, when the bank is neither being recharged nor is discharging DC power to the load. During normal, stable operating conditions, a differential relationship is established between the representative voltage and representative current signals. In one embodiment, a microprocessor-based system monitors the float voltage of the battery in order to ascertain when the battery system is in a normal, stable operating condition. The microprocessor also initially establishes the differential between the representative voltage and the representative current signals. The method includes determining when the differential relationship between the voltage and current signals exceeds a predetermined value and issues an alarm signal at that time. The alarm signal may be deferred until the differential relationship exceeds the predetermined value for a predetermined period of time. In one embodiment, this analysis is conducted in the microprocessor-based system.
226 Citations
21 Claims
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1. A method for detecting a deteriorating condition in a plurality of serially connected batteries utilized as a bank of standby batteries coupled in parallel to a battery charger and a DC powered load between a first and a second battery bus comprising the steps of:
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providing a first audio frequency current transformer for injecting a predetermined signal current and a second audio frequency current transformer for sensing a resultant current signal; injecting an audio frequency current as said predetermined signal current via said first audio frequency current transformer into one of said first and second battery busses; detecting a current signal at said audio frequency and carried by said one battery bus as said resultant current signal via said second audio frequency current transformer and generating a representative current signal which is related to said injected audio frequency current signal; detecting a voltage drop, at said audio frequency, across said first and second battery busses and generating a representative voltage signal which is related to said injected audio frequency current signal; when said bank of standby batteries is in a normal, stable operating condition, not when said bank is in a recharging state nor when said bank is supplying DC power to said load in a discharging state, establishing a differential relationship between the representative voltage and the representative current signals; and
,determining when said differential relationship exceeds at least one predetermined value and issuing an alarm signal thereat. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting a deteriorating condition in a plurality of serially connected batteries utilized as a bank of standby batteries coupled in parallel to a battery charger and a DC powered load between a first and a second battery bus comprising the steps of:
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providing a first audio frequency current transformer for injecting a predetermined signal current and a second audio frequency current transformer for sensing a resultant current signal; injecting an audio frequency current as said predetermined signal current via said first audio frequency current transformer into one of said first and second battery busses; detecting a current signal at said audio frequency and carried by said one battery bus as said resultant current signal via said second audio frequency current transformer and generating a representative current signal which is related to said injected audio frequency current signal; detecting a voltage drop, at said audio frequency, across said first and second battery busses and generating a representative voltage signal which is related to said injected audio frequency current signal; comparing the representative voltage and the representative current signals when said bank of standby batteries is in a normal, stable operating condition, and issuing an alarm signal when a result of said comparison falls outside of predetermined boundary values. - View Dependent Claims (14)
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15. A battery resistance monitor for detecting a deteriorating condition in a plurality of serially connected batteries utilized as a bank of standby batteries coupled in parallel to a battery charger and a DC powered load between a first and a second battery bus comprising:
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means for generating and injecting, via an electromagnetic coupling with a first audio frequency current transformer, an audio frequency current into one of said first and second battery busses; an audio frequency current detector configured as a second audio frequency current transformer, electromagnetically coupled to said one battery bus, detecting a presence of an audio frequency current signal carried by said one battery bus and matching said injected audio frequency current signal; an audio frequency voltage transformer and detector, capacitively coupled across said first and second battery busses, detecting a voltage drop at said audio frequency, across said first and second busses; a first and a second converter, respectively coupled to said current detector and said voltage detector, for generating corresponding representative current and representative voltage signals; a comparing means, coupled to said converters, for determining when a differential relationship between said representative voltage signal and said representative current signal falls outside at least one predetermined boundary value and generating an alarm signal thereupon. - View Dependent Claims (16, 17, 18, 19, 20, 21)
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Specification