Contactor failure determining method and contactor failure determining device

1. A contactor failure determining device comprising:

a contactor control unit that outputs a control signal for switching a positive-side contactor provided between a positive electrode of the multi-cell battery and a positive electrode of a load to which the multi-cell battery supplies electric power to an open state at the end of supply of high-voltage power from a state in which a control signal for controlling the positive-side contactor and a negative-side contactor provided between a negative electrode of the multi-cell battery and a negative electrode of the load to a closed state and a precharge contactor provided between the multi-cell battery and the load to an open state is output; and

a determination unit that determines a presence of fixing of the precharge contactor based on a degree of voltage drop of a voltage applied to the load after the control signal for switching the positive-side contactor to the open state is output.

2. The contactor failure determining device according to claim 1 , wherein

the determining unit determines that the precharge contactor is fixed in the closed state when a voltage drop amount per unit period of the load after the control signal for switching the positive-side contactor to the open state is output is equal to or larger than a first predetermined value and is smaller than a second predetermined value which is larger than the first predetermined value.

3. The contactor failure determining device according to claim 2 , wherein

the determining unit further determines that the positive-side contactor is fixed in a closed state when the voltage drop amount per unit period after the control signal for switching the positive-side contactor to the open state is output is smaller than a third predetermined value or when the voltage drop amount of the load after elapse of the predetermined period after the control signal for switching the positive-side contactor to the open state is output is smaller than a fourth predetermined value.

4. The contactor failure determining device according to claim 3 , wherein

a plurality of loads are connected to the multi-cell battery, and

the determining unit sets the third and fourth predetermined values to values smaller than those when a failure is not detected in the load, when the failure is detected in at least one of the plurality of loads.

5. The contactor failure determining device according to claim 2 , wherein

a plurality of loads are connected to the multi-cell battery, and

the determining unit sets the first and second predetermined values to values smaller than those when a failure is not detected in the load, when the failure is detected in at least one of the plurality of loads.

6. The contactor failure determining device according to claim 1 , wherein

the determining unit determines that the precharge contactor is fixed in the closed state when a voltage drop amount of the load after elapse of a predetermined period after the control signal for switching the positive-side contactor to the open state is output is equal to or larger than a first predetermined value and is smaller than a second predetermined value which is larger than the first predetermined value.

7. The contactor failure determining device according to claim 6 , wherein

a plurality of loads are connected to the multi-cell battery, and

the determining unit sets the first and second predetermined values to values smaller than those when a failure is not detected in the load, when the failure is detected in at least one of the plurality of loads.

8. The contactor failure determining device according to claim 1 , wherein

the determining unit further determines a presence of fixing of the positive-side contactor as well as the presence of fixing of the precharge contactor based on a degree of voltage drop of the voltage applied to the load after the control signal for switching the positive-side contactor to the open state is output.