Diagnosis device, energy storage apparatus, and diagnosis method

1. A diagnosis device that diagnoses current cutoff devices connected in parallel and disposed on an energization path to an energy storage device mounted on a vehicle, the diagnosis device comprising a processor configured to:

detect a parameter indicative of the vehicle being parked, the parameter being either: (1) an electrical current value that is equal to or smaller than a predetermined value for at least a first predetermined time; or (2) a lack of communication between the diagnosis device and a vehicle electronic control unit for at least a second predetermined time;

upon detecting the parameter indicative of the vehicle being parked, perform switch processing of switching one of the current cutoff devices to be diagnosed from an opened state to a closed state or from the closed state to the opened state or keeping closed the one of the current cutoff devices and switching closed or keeping closed another of the current cutoff devices while the parameter remains indicative of the vehicle being parked;

detect end-to-end voltage when current larger than a threshold flows through an end point A and an end point B after the switch processing, the current cutoff devices being connected to the end point A and the end point B in parallel, the threshold being set based on a peak value of cranking current that flows from the energy storage device to a starter at a start of an engine;

diagnose the one of the current cutoff devices based on the detected end-to-end voltage; and

close both of the current cutoff devices while the vehicle is travelling after the detection of the end-to-end voltage in a case in which the one of the current cutoff devices being diagnosed is switched from the closed state to the opened state through the switch processing while the vehicle is parked.

2. The diagnosis device according to claim 1 , wherein the end-to-end voltage of the current cutoff device is detected while the energy storage device is discharging.

3. The diagnosis device according to claim 1 , wherein the end-to-end voltage of the current cutoff device is detected while the energy storage device is being charged.

4. The diagnosis device according to claim 1 , wherein:

the diagnosis device sequentially determines open failure and close failure of each of a pair of current cutoff devices by executing processing (1) to (3):

(1) each time when an engine of the vehicle stops, one of the pair of current cutoff devices to be diagnosed is alternately switched from the opened state to the closed state or from the closed state to the opened state or the one of the current cutoff devices is kept closed, while the other of the pair of current cutoff devices is kept closed;

(2) the end-to-end voltage is detected when current larger than the threshold flows after the switching processing; and

(3) failure of the one of the pair of current cutoff devices is determined based on the detected end-to-end voltage.

5. The diagnosis device according to claim 4 , wherein failure of the current cutoff device is determined by comparing the end-to-end voltage with a value detected in a previous iteration of the processing (2).

6. The diagnosis device according to claim 4 , wherein failure of the current cutoff device is determined by comparing the end-to-end voltage with the end-to-end voltage of the current cutoff device detected in a non-diagnostic state.

7. The diagnosis device according to claim 1 , wherein the processor is further configured to issue a warning upon determination of failure.

8. The diagnosis device according to claim 1 , wherein the current cutoff devices are each a relay including a mechanical contact.

9. The diagnosis device according to claim 1 , wherein the energy storage device is a lithium ion secondary battery.

10. The diagnosis device according to claim 1 , wherein the vehicle is an idling stop vehicle.

11. An energy storage apparatus comprising:

an energy storage device;

the diagnosis device according to claim 1 ; and

a case housing the energy storage device and the diagnosis device.

12. A diagnosis method that diagnoses current cutoff devices connected in parallel and disposed on an energization path to an energy storage device mounted on a vehicle, the diagnosis method comprising the steps of:

detecting, via at least one sensor, a parameter indicative of the vehicle being parked, the parameter being either: (1) an electrical current value that is equal to or smaller than a predetermined value for at least a first predetermined time; or (2) a lack of communication between the diagnosis device and a vehicle electronic control unit for at least a second predetermined time;

upon detecting the parameter indicative of the vehicle being parked, performing, via a processor, switch processing of switching one of the current cutoff devices to be diagnosed from an opened state to a closed state or from the closed state to the opened state or keeping closed the one of the current cutoff devices and switching closed or keeping closed another of the current cutoff devices while the parameter remains indicative of the vehicle being parked;

detecting end-to-end voltage when current larger than a threshold flows through an end point A and an end point B after the switch processing, the current cutoff devices being connected to the end point A and the end point B in parallel, the threshold being set based on a peak value of cranking current that flows from the energy storage device to a starter at a start of an engine;

diagnosing the one of the current cutoff devices based on the detected end-to-end voltage; and

closing both of the current cutoff devices while the vehicle is travelling after the detection of the end-to-end voltage in a case in which the one of the current cutoff devices being diagnosed is switched from the closed state to the opened state through the switch processing while the vehicle is parked.