A power supply system includes: a voltage converter that converts a voltage between first and second power circuits; a power controller that controls charging and discharging of first and second batteries; a cooling output controller that controls cooling output for the second battery; a temperature remaining-capacity acquirer that acquires a temperature remaining-capacity T2_mar; and a cooling remaining-capacity acquirer that acquires a cooling remaining-capacity PC2_mar depending on a difference between maximum cooling output and the cooling output of the second cooler. The power controller is configured to stop the voltage converter in a case where at least one of the temperature remaining-capacity T2_mar and the cooling remaining-capacity PC2_mar is less than an associated one of a threshold value for the temperature remaining-capacity and a threshold value for the cooling remaining-capacity and a potential difference between the first and second batteries is equal to or more than a potential difference threshold value.