Abstract: This power supply device includes a battery unit which includes: a first battery pack; a step-up/down circuit for boosting the voltage of an external power supply up to the charge voltage of the battery pack; a first charge circuit; a first discharge circuit for detecting a voltage drop of the external power supply and performing discharge from the battery pack to a load device; and a control circuit for controlling charging and discharging. The discharge circuit has a first discharge switch and a second discharge switch which are connected in series between the battery pack and a power supply line. The first discharge switch is switched on/off by receiving a switching signal from the control circuit, and the second discharge switch is directly switched on/off not via the control circuit on the basis of the voltage of the external power supply.

Abstract: A voltage adjuster has: a current path connecting one end on an input/output terminal side and the other end on a secondary battery side; a bypass path of the current path; a converter provided in the bypass path and capable of changing input electric power to a predetermined voltage corresponding to the secondary battery or a predetermined voltage corresponding to an external device in accordance with the charge or discharge of the second battery; and a path selector configured to select a path to be used out of the current path or the bypass path in accordance with the charge or discharge of the secondary battery.

Abstract: A voltage adjuster has: a current path connecting one end on an input/output terminal side and the other end on a secondary battery side; a bypass path of the current path; a converter provided in the bypass path and capable of changing input electric power to a predetermined voltage corresponding to the secondary battery or a predetermined voltage corresponding to an external device in accordance with the charge or discharge of the second battery; and a path selector configured to select a path to be used out of the current path or the bypass path in accordance with the charge or discharge of the secondary battery.

Abstract: A power storage system includes a plurality of power storage sections parallelly disposed, a plurality of charge/discharge circuits that individually charge/discharge the plurality of power storage sections, and a system control section that controls the plurality of charge/discharge circuits, and the system control section controls the charge/discharge circuits such that power storage sections adjacent to one another in vertical, horizontal and front-rear directions are not simultaneously charged or discharged.