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

There is herein provided an uninterruptible power supply device with a degradation judgment circuit 4 of a storage battery 2 which can perform an exact judgment, continuing the power supply to a load apparatus 8 stably without giving the excessive burden to the storage battery 2. The storage battery 2 is floatingly charged from a rectifier 1 connected with the power source 10. The device has the control circuit 3 for controlling the output voltage of the rectifier 1 and the degradation judgment circuit 4. The output voltage of the rectifier 1 is lowered to below a steady state by the control circuit 3. As a result, the storage battery 2 discharges with the current Idc restricted rather than rated discharge current. And a part of power supply is supplied to the load 8. The degradation judgment circuit 4 judges the degradation of the storage battery based on the discharge voltage Vdc.