Leak test method for fuel cell stack

A leak test method for a fuel cell stack for checking whether there is a leak point in the fuel cell stack, the fuel cell stack comprising:

• a cell stack body formed by stacking a plurality of unit cells together;
• a first end plate located at one end of the cell stack body in a stacking direction of the unit cells;
• and a second end plate located at another end of the cell stack body in the stacking direction of the unit cells,
• the leak test method comprising:
• a tubular body mounting step of surrounding the unit cells with a tubular body including a first opening and a second opening at both ends thereof;
• and
• a determination step performed after the tubular body mounting step, wherein
• in the tubular body mounting step, by connecting the tubular body to the first end plate and the second end plate, the first opening and the second opening are closed respectively by the first end plate and the second end plate, the tubular body extends from the first end plate to the second end plate, and a gap is formed between outer walls of the unit cells and an inner wall of the tubular body, and
• in the determination step, a test gas is supplied to an inside of the fuel cell stack to determine whether the test gas exists in the gap.