A test system for testing a battery pack having a high voltage terminal, a low voltage terminal, first and second battery modules, and a master microprocessor is provided. The test system includes an inverter unit and a test computer. The inverter unit iteratively grounds the high voltage terminal and the low voltage terminal. The test computer sends a first message to the master microprocessor that requests first and second voltage values of the first and second battery modules. The master microprocessor sends a second message having the first and second voltage values to the test computer which determines a first voltage deviation value. The test computer sets a test flag to a predetermined pass value if the test computer received the second message and the first voltage deviation value is less than a first threshold voltage deviation value.