Uninterruptible power supply device with circuit for degradation judgment of storage battery

An uninterruptible power supply device for supplying power to a load and for floatingly charging a storage battery from a converter connecting to an alternating current power source, and having a degradation judgment circuit for the storage battery, the degradation judgment circuit comprising:

• a control circuit for controlling an output voltage of the converter to be lower than a steady state voltage, so as to cause the storage battery to discharge at a more limited current than the rated current of the storage battery, and so as to cause the converter to supply a part of a load current to the load;
• a judgment circuit that judges the degradation of the storage battery based on a charging time of the storage battery from a time when the control circuit controls the output voltage of the converter to return to the steady state voltage to a time when the battery is fully charged, the judgment circuit using the charging time to determine whether the storage battery is degraded or normal, a degraded storage battery having a maximum storage capacity that is less than a maximum storage capacity of a new storage battery of the same kind thereof, and
• a timer for measuring the charging time of the storage battery from the time when the control circuit controls the output voltage of the converter to return to the steady state voltage to the time when the battery is fully charged.