NOVELTY - The strength setting method involves setting the strength of the constrained mechanism. The constrained mechanism provides a restraint load to the electrical storage apparatus. The strength of the constrained mechanism is set to the restraint load based on the restraint load adding the load increase amount based on the following formula: (1) (DELTA)F1+Fa(min) not greater than (DELTA)F2+Fa(max), and (2) (DELTA)F1 not less than (DELTA)F2.    USE - Strength setting method for load in electrical storage apparatus (claimed), e.g., battery stack, mounted in vehicles such as electric and hybrid vehicles.    ADVANTAGE - Maintains restraint of electrical storage apparatus until the internal pressure of the electrical storage apparatus attains the working pressure of the valve since the strength of the constrained mechanism is set to the restraint load based on the restraint load adding the load increase amount based on predetermined formula.    DETAILED DESCRIPTION - The strength of the constrained mechanism is set to the restraint load based on the restraint load adding the load increase amount based on the following formula: (1) (DELTA)F1+Fa(min) not greater than (DELTA)F2+Fa(max), and (2) (DELTA)F1 not less than (DELTA)F2, in which Fa(min) is the lower limit of the restraint load in the initial state before the internal pressure of the electrical storage apparatus rises, Fa(max) is the upper limit of the restraint load in the initial state. (DELTA)F1 is the increase amount of the load accompanying the inner pressure rise of the electrical storage apparatus when the electrical storage apparatus receives the restraint load Fa(min), and (DELTA)F2 is the increase amount of the load accompanying the inner pressure rise of the electrical storage apparatus when the electrical storage apparatus receives the restraint load Fa(max).    DESCRIPTION OF DRAWING(S) - The drawing shows a graph highlighting the relationship between the restraining surface pressure of initial state, and restraining surface pressure when the internal pressure of the battery case rises. (Drawing includes non-English language text).