Method for determining battery state of charge by measuring A.C. electrical phase angle change

A battery charge - discharge life cycle testing system including continuous battery state of charge monitoring comprising:

• a battery that is to be charge - discharge life cycle tested;
• a shunt coupled to said battery;
• a first programable load bank coupled across said shunt and said battery;
• a second programable load bank coupled in series with said shunt and said battery;
• a charging current power supply coupled to said battery through said second programable load bank and said shunt;
• a D.C. charge level control circuit coupled to said second programable load bank;
• a D.C. discharge current level control circuit coupled to said first programable load bank;
• a reference voltage source having an alternating current output coupled to said D.C. discharge level control circuit, said alternating current output being applied to said battery through said D.C. discharge level control circuit, said first programable load bank and said shunt;
• a first amplifier having its input coupled across said shunt and having an output;
• a second amplifier having its input coupled across said battery and having an output;
• a phase angle measuring circuit having a first input coupled to said output of said first amplifier, a second input coupled to said output of said second amplifier and having an output;
• and
• a meter coupled to said output of said phase angle measuring circuit.