03984762 is referenced by 154 patents and cites 1 patents.

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.

Title
Method for determining battery state of charge by measuring A.C. electrical phase angle change
Application Number
5/556526
Publication Number
3984762
Application Date
March 7, 1975
Publication Date
October 5, 1976
Inventor
Edward J Dowgiallo Jr
Oxon Hill
MD, US
Agent
Nathan Edelberg
Assignee
The United States of America represented by the Secretary of the Army
DC, US
IPC
G01N 27/42
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