Fault detection and diagnostic system for automotive battery charging systems

An in situ self-diagnostic automotive alternator-battery charging system comprising:

• a battery;
• voltage regulator means sensing battery voltage and in response to an actuating signal, generating an excitation signal in response to the sensed battery voltage;
• alternator means coupled to said voltage regulator means and selectively coupled to said battery, driven by a vehicle engine, providing a rectified electrical signal for charging said battery in response to said excitation signal;
• an ignition switch for establishing coupling of said battery to said alternator means;
• a plurality of electronic circuit status detectors powered by said automotive charging system, each of said plurality being coupled to said battery or alternator means by isolating transistors preventing the flow of electrical current through said detectors when said ignition switch is open,
• each of said plurality of detectors maintaining a first logic state when a corresponding electrical signal characteristic is within a predetermined range and a second logic state when said electrical signal characteristic is outside said predetermined range, selected ones of said plurality being coupled to said battery, voltage regulator means and said alternator means;
• one of said plurality of said electronic circuit status detectors being coupled to said alternator and including means to detect the operation of said alternator and producing logic signals corresponding to the operative and inoperative status of said alternator;
• logic means coupled to said plurality of circuit status detectors and including power supply means, responsive to logic signals from said status detector for detection of the operation of said alternator, for supplying said actuating signal to said voltage regulator means when said alternator means operation has been detected,
• said logic means being responsive to the logic output states of said circuit status detectors, identifying predetermined sequences of logic states thereby to identify the occurrence of faults in said charging system.

The method of electronically diagnosing faults in the performance of an automotive alternator, voltage regulator, and battery system comprising the steps of:

• providing a plurality of electronic circuit status detectors at preselected positions in said system to monitor predetermined electrical signal characteristics;
• supplying in situ power to said electronic status detectors from said automotive system;
• establishing normal operating ranges for said predetermined electrical signal characteristics such that each of said circuit status detectors maintains a first logic state when said corresponding signal characteristic is within said operating range and a second logic state when said signal characteristic is outside said operating range, including selecting one of said plurality of electronic circuit status detectors and establishing time intervals for detecting the regular occurrence of pulse signals;
• and
• monitoring said logic states of said plurality of circuit status detectors for predetermined sequences of said logic states, thereby to identify the occurrence of faults in the system.