A storage apparatus stores output property data including groups of residual capacities of a secondary battery and output densities corresponding to the residual capacities. In the output property data, both a difference between a residual capacity of a group that includes an extreme value in the output densities and a residual capacity of a group that includes an output density that immediately precedes the extreme value, and a difference between the residual capacity of the group that includes the extreme value in the output densities and a residual capacity of a group that includes an output density that immediately follows the extreme value are less than a difference between output densities of other groups adjacent to each other.