Importance

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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.

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First Claim