Electric energy accumulator

The invention relates to an electrical energy store, in particular for a hand-held power tool, comprising:-a series connection of energy store units, one of which is connected to a reference potential; a series circuit of measuring resistors; measurement switching devices, a first of the measurement switching devices being connected between the series circuit of the energy storage units and the series circuit of the measurement resistors, and the associated measurement switching device being connected between a connection node of an adjacent energy storage unit and a connection node of an adjacent measurement resistor; -a balancing switching device connected between one of the measuring resistors and a reference potential; -a measuring unit which measures the voltage falling on one of the measuring resistors; and a control unit which is designed to actuate the measuring switching device and the balancing switching device, to determine the state of charge of the energy storage unit as a function of their switc