An energy storage system may include one or more battery packs, wherein one terminal of the one or more battery packs is electrically coupled to a resistor representative of an isolation resistance of the energy storage system, a semiconductor relay switch, a plurality of resistors configured to electrically couple to the one or more battery packs via the semiconductor relay switch, a gain field-effect transistor (FET) configured to electrically short at least one resistor of the plurality of resistors, one or more capacitors electrically couples to a system ground of a vehicle and the one or more battery packs, and a control system configured to control the semiconductor switch and the gain FET.