03946299 is referenced by 143 patents and cites 4 patents.

A circuit for detecting and indicating the actual state of charge of a storage battery in response to signals sampled from various points in the circuit powered by the battery. Such circuit is adapted to calculate the open circuit voltage of the battery, it being realized that the open circuit voltage is directly proportional to the battery state of charge. A function generator is constructed to simulate the characteristic curve of the battery relating the internal resistance to the percent charge. Feedback is provided from the output of the indicating circuitry to the bias point of the function generator for causing the generator to produce a signal related to the actual internal resistance of the battery. The circuit is adapted to provide a reliable indication of the amount of usable energy remaining in the battery, irrespective of the conditions under which the battery was discharged.

Title
Battery state of charge gauge
Application Number
5/548913
Publication Number
3946299
Application Date
February 11, 1975
Publication Date
March 23, 1976
Inventor
Robert F Bourke
Wilson
WI, US
Clinton C Christianson
Minnetonka
MN, US
Agent
Wolfe Hubbard Leydig Voit & Osann
Assignee
Gould
IL, US
IPC
G01N 27/42
H02J 7/00
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