Test system and method for testing a battery pack

A method for determining whether a battery pack operates correctly even if the battery pack is grounded to a vehicle chassis, the battery pack having a master microprocessor, a high voltage terminal, a low voltage terminal, first and second battery modules coupled in series to one another between the high voltage terminal and the low voltage terminal, each battery module having a positive terminal and a negative terminal, the method comprising:

• providing an inverter unit electrically coupled to both the high voltage terminal and the low voltage terminal of the battery pack;
• providing a test computer operably coupled to the master microprocessor;
• directly grounding the high voltage terminal of the battery pack such that the high voltage terminal has a ground voltage level during a first time interval utilizing the inverter unit while the low voltage terminal has a negative voltage level, in response to a pulse width modulated signal;
• directly grounding the low voltage terminal such that the low voltage terminal is transitioned from the negative voltage level to the ground voltage level during a second time interval utilizing the inverter unit while the high voltage terminal is transitioned from the ground voltage level to a positive voltage level, in response to the pulse width modulated signal, the second time interval being after the first time interval;
• directly grounding the high voltage terminal such that the high voltage terminal is transitioned from the positive voltage level to the ground voltage level during a third time interval utilizing the inverter unit while the low voltage terminal is transitioned from the ground voltage level to the negative voltage level, in response to the pulse width modulated signal, the third time interval being after the second time interval;
• sending a first message to the master microprocessor from the test computer during at least one of the first, second, and third time intervals that requests first and second voltage values, indicating a first output voltage of the first battery module and a second output voltage of the second battery module, wherein the first output voltage is indicative of a voltage difference between the positive and negative terminals of the first battery module and the second output voltage is indicative of a voltage difference between the positive and negative terminals of the second battery module;
• sending a second message having the first and second voltage values from the master microprocessor to the test computer, if the master microprocessor received the first message;
• determining a first voltage deviation value based on the first and second voltage values utilizing the test computer, if the test computer received the second message, the first voltage deviation value being an absolute value of a difference between the first and second voltage values;
• and
• setting a test flag to a predetermined pass value indicating the battery pack is operating correctly, even if the battery pack is grounded to the vehicle chassis, utilizing the test computer, if the test computer received the second message and the first voltage deviation value is less than a first threshold voltage deviation value.

A test system for determining whether a battery pack operates correctly even if the battery pack is grounded to a vehicle chassis, the battery pack having a master microprocessor, a high voltage terminal, a low voltage terminal, and first and second battery modules coupled in series to one another between the high voltage terminal and the low voltage terminal, each battery module having a positive terminal and a negative terminal, the test system comprising:

• an inverter unit adapted to be electrically coupled to both the high voltage terminal and the low voltage terminal, the inverter unit configured to alternate between directly grounding the high voltage terminal of the battery pack and directly grounding the low voltage terminal of the battery pack at respective times within a time interval;
• and
• a test computer adapted to be operably coupled to the master microprocessor, the test computer programmed to:
• send a first message to the master microprocessor during the time interval, the first message requesting each of (i) a first voltage value during the time interval, the first voltage value indicating a first output voltage of the first battery module during the time interval based on a voltage difference between the positive and negative terminals of the first battery module, and (ii) a second voltage value during the time interval, the second voltage value indicating a second output voltage of the second battery module based on a voltage difference between the positive and negative terminals of the second battery module;
• in response to receiving a second message from the master microprocessor indicating the requested first voltage value and the second voltage value, determine a first voltage deviation value based on a difference between the first voltage value and the second voltage value, wherein the first voltage deviation value is a magnitude of the difference between the first voltage value and the second voltage value;
• and
• if the first voltage deviation value is less than a first threshold voltage deviation value, set a test flag to a predetermined pass value indicating the battery pack is operating correctly even if the battery pack is grounded to the vehicle chassis.