Contactor failure determination apparatus for vehicle

A contactor failure determination apparatus mounted to a vehicle including a battery that includes a positive electrode terminal and a negative electrode terminal, a first circuit that includes an inverter and a motor, a first main contactor that makes or interrupts electrical connection between the first circuit and one terminal of the positive electrode terminal and the negative electrode terminal, a second main contactor that makes or interrupts electrical connection between the first circuit and the other terminal of the positive electrode terminal and the negative electrode terminal, and a pre-charge contactor that is disposed in parallel with the first main contactor and makes or interrupts the electrical connection between the first circuit and the one terminal, the contactor failure determination apparatus comprising:

• a second circuit that includes an external charger configured to supply electric power from an external power supply to the battery so as to charge the battery;
• a pair of external charging contactors that make or interrupt electrical connection between positive-electrode side lines of the first circuit and the second circuit and between negative-electrode side lines of the first circuit and the second circuit;
• a voltage sensor configured to detect rising or dropping of a voltage of the second circuit;
• and
• a controller that controls the first main contactor, the second main contactor, the pre-charge contactor, and each of the external charging contactors such that these contactors are opened during a stop of the vehicle, wherein
• electrical resistance between the one terminal and the first circuit via the pre-charge contactor is set to be higher than electrical resistance between the other terminal and the first circuit via the first main contactor,
• in response to a vehicle start request as a request to start the vehicle being made, the controller:
• executes a first control for closing one of the pair of external charging contactors;
• executes a second control for closing the pre-charge contactor after execution of the first control;
• executes a third control for closing the second main contactor after execution of the second control;
• and
• in response to the voltage sensor detecting that the voltage of the second circuit has risen after execution of the third control, determines that the other of the pair of external charging contactors has failed in a closed state, and
• when executing the first control in response to an immediately subsequent vehicle start request, the controller closes the other of the pair of external charging contactors rather than the one of the pair of external charging contactors.