A first power storage pack for connection in parallel with a second power storage pack with a different battery chemistry and without any DC-DC converter interposed between the first power storage pack and the second power storage pack, wherein: a charge/discharge curve of the first power storage pack measured according to the method defined in the description has a step passing through a range of (12.5 × n) V or higher and (12.8 × n) V or lower, where n is a natural number of 1 or more and 125 or less, on a lower state of charge, SOC, side than a start point of the step of the charge/discharge curve of the first power storage pack, an average discharge voltage falls within a range of (9.0 × n) V or higher and (12.5 × n) V or lower and/or a voltage at a peak top obtained on a dQ/dV curve obtained by differentiating the discharge curve with respect to voltage falls within a range of (9.0 × n) V or higher and (12.5 × n) V or lower, on a higher SOC side than an end point of the step of the charge/discharge curve of the first power storage pack, an average charge voltage falls within the range of (12.8 × n) V or higher and (14.8 × n) V or lower and/or a voltage at a peak top obtained on a dQ/dV curve obtained by differentiating the charge curve with respect to voltage falls within the range of (12.8 × n) V or higher and (14.8 × n) V or lower, and wherein a step of a charge or discharge curve refers to a range in which the proportion of the amount of change in voltage, ΔV, on the charge/discharge curve to the amount of change in SOC, ΔSOC, is (100 × n) mV/% or more, when the SOC is in the range of 5% to 95%, and wherein the start point of a step is the minimum voltage of a discharge curve in the range of one step, and the corresponding value of the SOC at the minimum voltage, and the end point of the step is the maximum voltage of a charge curve in the range of the same step, and the corresponding value of the SOC at the maximum voltage. a charge/discharge curve of the first power storage pack measured according to the method defined in the description has a step passing through a range of (12.5 × n) V or higher and (12.8 × n) V or lower, where n is a natural number of 1 or more and 125 or less, on a lower state of charge, SOC, side than a start point of the step of the charge/discharge curve of the first power storage pack, an average discharge voltage falls within a range of (9.0 × n) V or higher and (12.5 × n) V or lower and/or a voltage at a peak top obtained on a dQ/dV curve obtained by differentiating the discharge curve with respect to voltage falls within a range of (9.0 × n) V or higher and (12.5 × n) V or lower, on a higher SOC side than an end point of the step of the charge/discharge curve of the first power storage pack, an average charge voltage falls within the range of (12.8 × n) V or higher and (14.8 × n) V or lower and/or a voltage at a peak top obtained on a dQ/dV curve obtained by differentiating the charge curve with respect to voltage falls within the range of (12.8 × n) V or higher and (14.8 × n) V or lower, and wherein a step of a charge or discharge curve refers to a range in which the proportion of the amount of change in voltage, ΔV, on the charge/discharge curve to the amount of change in SOC, ΔSOC, is (100 × n) mV/% or more, when the SOC is in the range of 5% to 95%, and wherein the start point of a step is the minimum voltage of a discharge curve in the range of one step, and the corresponding value of the SOC at the minimum voltage, and the end point of the step is the maximum voltage of a charge curve in the range of the same step, and the corresponding value of the SOC at the maximum voltage.