POWER SUPPLY DEVICE

A power supply device includes an inverter, a voltage converter, a capacitor, a current detector, a counter, and a controller. The inverter converts DC power into AC power and supplies the converted AC power to a load. The voltage converter performs voltage conversion for a DC voltage from a battery. The capacitor smoothes the DC voltage from the voltage converter and inputs the smoothed DC voltage to the inverter. The current detector detects a battery current flowing from the battery into the voltage converter. The counter measures a discharge time of the battery. The controller stops the voltage converter when the measured discharge time of the battery exceeds a discharge permissible time. Based on an output from the current detector, the controller sets the discharge permissible time to be shorter as the battery current is higher when the battery current exceeds a threshold value during discharging of the battery.