An electric energy storage system comprising: an electric energy storage module having a plurality of electric energy storage units connected in series, each of the plurality of electric energy storage units having one electric energy storage bank or a plurality of electric energy storage banks connected in series; a charger for charging at least one of the electric energy storage banks; a balancing circuit connected to the electric energy storage module to correct a variation in charged/discharged state between the electric energy storage banks; a voltage detection section for detecting a voltage across or across each of one or more of the electric energy storage banks, or a voltage across the charger; a plurality of taps led out, respectively, from one of opposite terminals of the electric energy storage module and/or one or more of a plurality of series-connection points between the electric energy storage units, through respective switches; and a switch control section for switching the switches such that either one of the plurality of taps is connected to one of opposite terminals of the charger, the switch control section being operable, during a charging period, to sequentially switch the switches according to progress of the charging, based on a detection result from the voltage detection section, so as to control the number of at least one of the plurality of electric energy storage units which is to be charged not via the balancing circuit but directly from the charger, or one of the plurality of taps is connected to one of opposite terminals of the charger and another of the plurality of taps is connected to the other terminal of the charger, the switch control section being operable, with respect to each of a plurality of groups set by grouping the plurality of electric energy storage units, to sequentially switch the switches so as to repeatedly charge the same at least one electric energy storage unit not via the balancing circuit but directly from the charger, in a time division manner; whereby the energy storage units which are not directly charged by the charger, receive electric charge from the storage units directly charged by the charger, via the balancing circuit. an electric energy storage module having a plurality of electric energy storage units connected in series, each of the plurality of electric energy storage units having one electric energy storage bank or a plurality of electric energy storage banks connected in series; a charger for charging at least one of the electric energy storage banks; a balancing circuit connected to the electric energy storage module to correct a variation in charged/discharged state between the electric energy storage banks; a voltage detection section for detecting a voltage across or across each of one or more of the electric energy storage banks, or a voltage across the charger; a plurality of taps led out, respectively, from one of opposite terminals of the electric energy storage module and/or one or more of a plurality of series-connection points between the electric energy storage units, through respective switches; and a switch control section for switching the switches such that either one of the plurality of taps is connected to one of opposite terminals of the charger, the switch control section being operable, during a charging period, to sequentially switch the switches according to progress of the charging, based on a detection result from the voltage detection section, so as to control the number of at least one of the plurality of electric energy storage units which is to be charged not via the balancing circuit but directly from the charger, or one of the plurality of taps is connected to one of opposite terminals of the charger and another of the plurality of taps is connected to the other terminal of the charger, the switch control section being operable, with respect to each of a plurality of groups set by grouping the plurality of electric energy storage units, to sequentially switch the switches so as to repeatedly charge the same at least one electric energy storage unit not via the balancing circuit but directly from the charger, in a time division manner; whereby the energy storage units which are not directly charged by the charger, receive electric charge from the storage units directly charged by the charger, via the balancing circuit.