Power supply device

1. A power supply device, comprising:

a plurality of battery packs connected in parallel to a load;

a plurality of battery controllers corresponding to the plurality of battery packs in a one-to-one correspondence; and

a relay configured to connect or disconnect each of the battery packs to or from the load,

wherein the plurality of battery controllers has a master-slave configuration including a master controller and at least one slave controller, and each of the master controller and the at least one slave controller is configured to execute a self-diagnosis and a mechanical operation diagnosis of a mechanical component including the relay before connecting the battery packs to the load,

wherein each of the master controller and the at least one slave controller is configured to perform communication between the master controller and the at least one slave controller by using a first communication scheme and a second communication scheme that has a communication period shorter than a communication period of the first communication scheme,

wherein during executing the self-diagnosis, the master controller and the at least one slave controller are configured to perform the communication by using the first communication scheme, and

wherein during executing the mechanical operation diagnosis, which is executed after the executing the self-diagnosis is completed, the master controller and the at least one slave controller are configured to perform the communication by using the second communication scheme.

2. The power supply device of claim 1 , wherein the master controller and the at least one slave controller are configured to, during executing the mechanical operation diagnosis, perform the communication between the master controller and the at least one slave controller by the first communication scheme or the second communication scheme, whichever has the communication period that reaches earlier.

3. The power supply device of claim 1 , wherein when the master controller determines through the self-diagnosis and the mechanical operation diagnosis that at least the master controller has no abnormality, the master controller proceeds to a normal battery control without waiting for a diagnosis result of the at least one slave controller.

4. The power supply device of claim 1 , wherein the power supply device supplies DC power, which is to be converted to three-phase AC power via an inverter, to a motor generator in response to a request from a vehicle's system side.

5. The power supply device of claim 4 , when charging is necessary in accordance with determination of a vehicle control device mounted on the vehicle's system side, the power supply device stores DC power converted via the inverter from three-phase AC power generated by the motor generator.

6. The power supply device of claim 1 , wherein each of the battery packs includes a plurality of battery cells connected in series.

7. The power supply device of claim 6 , wherein each of the plurality of battery cells comprises a lithium ion secondary battery or a nickel hydride secondary battery.

8. The power supply device of claim 1 , wherein each battery pack is connected to a motor generator by turning on the relay that controls an output from the battery pack, and is disconnected from the external load by turning off the relay.

9. The power supply device of claim 5 , wherein the master controller and the at least one slave controller are connected by a communication bus that is different from a communication bus that connects the master controller and the vehicle control device.

10. The power supply device of claim 1 , wherein the master controller includes an input part, an output part, a monitoring part, and a communication part, and the monitoring part includes a Central Processing Unit, Read Only Memory, Random Access Memory, an internal clock circuit.