Control method for fuel cell system

A control method for a fuel cell system, the fuel cell system including a hydrogen storage part that stores hydrogen and a fuel cell stack that generates electric power using hydrogen supplied from the hydrogen storage part, the fuel cell system at least being capable of supplying electric power obtained by electric power generation of the fuel cell stack to an outside, the fuel cell system being mounted on a towed portion of a moving body that includes the towed portion and a towing portion, the fuel cell system being electrically connected to the towing portion, the towing portion including a battery and a drive device performing driving in response to supply of electric power, the towed portion being towed by the towing portion, the control method comprising:

• acquiring remaining amount information indicating a remaining amount of the battery;
• and
• starting supply of electric power directly to the drive device from the fuel cell system when it is determined that the remaining amount of the battery is equal to or less than a threshold based on the remaining amount information and that it is necessary to supply electric power to the drive device.