A method and device for predicting defects of a capacitor, the method including determining the ripple voltage (Udc), the temperature (TP), and the current (Ic) of the capacitor, determining the value of an equivalent series resistance (ESR) of the capacitor, and the capacitance value (C) of the capacitor using a digital filter, determining information representative of the state of aging of the capacitor according to the temperature of the capacitor, and displaying that information and information representative of the value of the capacitance (C) and/or information representative of a cause associated with the state of aging according to the capacitance value. The device may include a converter and an uninterruptible power supply.