DC CONSTANT VOLTAGE POWER SUPPLY DEVICE AND CHARGING DEVICE

PROBLEM TO BE SOLVED: To provide a charging device that has the function of detecting a degradation of a battery.SOLUTION: A charging device 2 includes: a transformer 101 having a primary winding 102 and a secondary winding 103; a switching element 106; a control section 20; a diode 108 and a capacitor 109 for generating a secondary DC voltage; and a storage section for storing a plurality of kinds of combination of a primary current (current Ip, voltage Vs), a primary voltage (voltage Ed) and a reference pulse width. The control section 20 charges a battery, and on completion of charging, detects a plurality of kinds of combination of the primary current, the primary voltage and a pulse width, reads out the reference pulse width stored in the storage section in accordance with the primary current and the primary voltage, and determines that the battery is a non-defective unit if all the plurality of pulse widths detected are within a predetermined range and determines that the battery is a defective unit if any one of the plurality of pulse widths is outside the predetermined range.