BACKUP POWER SUPPLY DEVICE AND METHOD FOR CHARGING AND DISCHARGING THE SAME

A backup power supply device (1) to be connected to a conduction path (P) from an external power supply (3) to an external load (4) including a plurality of secondary batteries (B1-B7) connected in parallel, a plurality of charging switches (SW1-SW7) that can individually pass and cut off charging power from the conduction path (P) to the plurality of secondary batteries (B1-B7), and a control device (10) for performing discharging control on the plurality of secondary batteries (B1-B7) when the power supply voltage of the conduction path (P) drops below a predetermined power failure detection threshold value, when battery voltages of the plurality of secondary batteries (B1-B7) drop below a predetermined charging start threshold value, the control device (10) performing charging control with a time difference (TD) set between charging start timings of the secondary batteries (B1-B7).