Process for auto-testing a fully discharged battery, such as double-layer capacitor battery, and circuit for doing the same

A process for performing an auto-test of a fully discharged battery (130) of an electronic appliance including a battery charger (160), said process involving the steps of : - performing (210) an initialization phase; - charging (220) said battery (130) with a predetermined constant current during a predefined period allowing stabilization of said current (Icurrent); - detecting (230) the voltage of said battery after said predefined period, said battery being still in charge; - testing (240) whether said sensed voltage is comprised within a predetermined range of threshold values (V1, V2), and - reporting a battery failure when said sensed value is outside said range. The invention is particularly adapted to the auto-test of a backup battery made of Electric double layer capacitors or any fully discharged backup battery.