A traction battery connection simulator is disclosed comprising a plurality of power supplies connected to simulate a traction battery and a plurality of switching devices that selectively connect the power supplies to a controller under test. The simulator further comprises a controller programmed to selectively connect at least one of power supplies to the controller under test for a predetermined period of time before connecting remaining power supplies. The controller may also be programmed to disconnect at least one power supplies from the controller under test for a predetermined period of time before disconnecting remaining power supplies. Voltages associated with each power supply and currents through each switching device may be compared to corresponding predetermined ranges. An indicator may be set in response to at least one of the voltages and currents being outside of a corresponding predetermined range.