Commonwealth Edison Company

Charles M Gabriel

Merlin E Burkum

An apparatus for measuring charge state of a battery having multiple cells includes a transmitter that is connected to the battery to apply a test signal across the battery. This test signal is preferably a continuous square wave signal having a frequency less than 3 Hz. The test signal alternates between a voltage adequate to charge the battery and a lower voltage, and the charging voltage is retained for a time sufficient to allow a polarization voltage to develop across individual cells. A receiver is connected to the cell to monitor the polarization voltage across a cell as it develops in response to the test signal. This polarization voltage can be monitored for example using a DC voltmeter, or by displaying the voltage versus time waveform. In either case an accurate indication of the state of the charge of the cell is provided.

Apparatus and method for utilizing polarization voltage to determine

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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Lombard, IL, United States of America

Charles M Gabriel