Electronic battery tester

An electronic battery tester for testing a battery comprising:

• a source configured to apply a signal to terminals of the battery through first and second connections of a Kelvin connection to the battery;
• a differential amplifier having an inverting input, a non-inverting input and a difference input;
• a first capacitor and a first resistor configured to couple a first terminal of the battery to the inverting input of the differential amplifier and thereby form a third connection at the Kelvin connection;
• a second capacitor and a second resistor configured to couple a second terminal of the battery to the non-inverting input of the differential amplifier and thereby form a fourth connection of the Kelvin connection;
• an electrical connection between the differential output and the inverting input of the amplifier which includes a third resistor;
• a fourth resistor electrically connected to the non-inverting input differential;
• an analog to digital converter coupled to the differential output of differential amplifier;
• a microprocessor configured to determine a condition of the battery as a function of an output of the analog to digital converter in response to the signal applied to the battery by the source.