System and method for isolation resistance measurement

An isolation resistance measuring circuit comprising:

• a plurality of terminals;
• a measurement circuit coupled to the plurality of terminals;
• a controller coupled to the measurement circuit, wherein the controller is coupled to and provides control signals to a plurality of switches coupled between the measurement circuit and the plurality of terminals;
• and
• an auxiliary voltage supply, wherein the controller and the measurement circuit are powered by the auxiliary voltage supply, wherein the measurement circuit is to apply a test voltage to a resistor and measure a voltage drop over the resistor, and wherein the controller is to determine, based on at least the voltage drop, an isolation resistance value between a chassis ground node and at least one of a battery pack or a battery link of a power system.

A method comprising:

• connecting a processing device to a chassis ground of an electric vehicle (EV), wherein the processing device is powered by an auxiliary voltage supply of the EV;
• connecting a measurement circuit to the chassis ground of the EV, wherein the measurement circuit is powered by the auxiliary voltage supply;
• applying a test voltage to a first terminal of at least one of a battery pack or a battery link of a power system of the EV via the measurement circuit;
• measuring, using the measurement circuit, a first voltage drop over a first resistor coupled to the first terminal, the first voltage drop resulting from the test voltage applied to the first terminal via the measurement circuit;
• applying the test voltage to a second terminal of the at least one of the battery pack or the battery link of the power system of the EV via the measurement circuit
• measuring, using the measurement circuit, a second voltage drop over the first resistor coupled to the second terminal, the second voltage drop resulting from the test voltage applied to the second terminal via the measurement circuit;
• determining a first isolation resistance value based on the test voltage applied to the first terminal, the first measured voltage drop, the second measured voltage drop, and a resistance value of the first resistor;
• comparing the first isolation resistance value to a predetermined threshold;
• and
• generating an alert in response to the first isolation resistance value being less than the predetermined threshold.