Vehicle power supply system

A vehicle power supply system being mounted on a vehicle, the vehicle power supply system comprising:

• a main power supply system including a main low-voltage power supply and a normal load;
• and
• a backup power supply system including a backup low-voltage power supply and an emergency important load and connected to the main power supply system, wherein:
• the backup power supply system is configured to supply electric power of the backup low-voltage power supply to the main power supply system;
• the backup power supply system includes:
• a switching device configured to switch connection and cut-off with the main power supply system;
• and a backup power supply control device that controls the switching device;
• the backup power supply control device is configured to:
• execute a backup low-voltage power supply state estimation processing of estimating whether the backup low-voltage power supply is in a state allowing supplying electric power for operating the emergency important load when the vehicle power supply system transitions from an OFF state to an ON state;
• output a signal indicating whether the backup low-voltage power supply is in a state allowing supplying electric power for operating the emergency important load;
• output a signal indicating that the backup low-voltage power supply is in a state allowing supplying electric power for operating the emergency important load, without executing the backup low-voltage power supply state estimation processing, in a case in which a state of the vehicle satisfies a predetermined condition;
• and
• execute the backup low-voltage power supply state estimation processing, and output a signal indicating that the backup low-voltage power supply is in a state allowing supplying electric power for operating the emergency important load based on an estimation result of the backup low-voltage power supply state estimation processing, in a case in which the state of the vehicle does not satisfy the predetermined condition.