Systems and methods for measuring isolation resistance

A non-transitory computer-readable medium comprising computer-executable instructions configured to cause a processor to:

• acquire a first voltage waveform corresponding to a first voltage measurement over a first period of time at a voltage output terminal configured to output at least two voltage waveforms when a plurality of resistors of a battery system is electrically coupled to one or more battery packs via a semiconductor relay switch;
• acquire a second voltage waveform corresponding to a second voltage measurement over a second period of time at the voltage output terminal in response to at least one resistor of the plurality of resistors directly coupled to the voltage output terminal being electrically shorted via a gain field-effect transistor (FET);
• determine an isolation resistance between a battery system and a chassis based at least in part on a Thevenin equivalent resistance calculated from the first voltage waveform and the second voltage waveform;
• and
• disconnect the one or more battery packs from the battery system in response to the isolation resistance being below a threshold resistance value.

An isolation measurement circuit for measuring isolation resistance, comprising:

• a semiconductor relay switch;
• a plurality of resistors configured to electrically couple to one or more battery packs via the semiconductor relay switch, wherein one terminal of the one or more battery packs is electrically coupled to a resistor of the plurality of resistors of a battery system;
• a gain field-effect transistor (FET) configured to electrically short at least one resistor of the plurality of resistors, wherein the at least one resistor of the plurality of resistors is directly coupled to a voltage output terminal configured to output a voltage waveform for determining an isolation resistance between the battery system and a chassis;
• one or more capacitors electrically coupled to a system ground of a vehicle and the one or more battery packs;
• and
• a control system configured to:
• acquire a first voltage waveform corresponding to a first voltage measurement over a first period of time at the voltage output terminal when the plurality of resistors is electrically coupled to the one or more battery packs via the semiconductor relay switch;
• acquire a second voltage waveform corresponding to a second voltage measurement over a second period of time at the voltage output terminal in response to the at least one resistor of the plurality of resistors directly coupled to the voltage output terminal being electrically shorted via the gain field-effect transistor (FET);
• and
• determine the isolation resistance between the battery system and the chassis based at least in part on a Thevenin equivalent resistance calculated from the first voltage waveform and the second voltage waveform.