PURPOSE: To prolong a life time of a battery, making its charging in a short time possible, by modulating a DC power supply so as to output a spike-like wave voltage, and by resonating the electrolytic liquid of the battery through applying an abrupt spike-like current to it, and further, by activating the electrolyte ions forcedly through the effect of this resonant oscillation.

CONSTITUTION: When switching off an electronic switch S1, a capacitor C2 is charged by the output voltage of a main power supply 1. Also, a capacitor C1 is charged by the main power supply 1 and an auxiliary power supply 2 via a diode D2 and a resistor R1. In this state, when switching on the electronic switch 1, a spike-like voltage is applied to a battery B1. 'Therefore, an abrupt spike-like current is given to the electrolytic liquid of the battery B1, and the electrolytic liquid is oscillated resonantly. By this resonant oscillation, electrolyte ions are activated forcedly, and a large amount of ion is absorbed by the electrode of the battery B1, and in its turn, the charging current of the battery B1 flows easily. Thereby, the battery B1 can be charged in a short time.