The invention relates to a charging device for charging at least one rechargeable energy storage unit, having a defined inner resistance and having a compensation circuit for the compensation of a voltage drop during the charging operation caused by the inner resistance. The compensation circuit has a current detection for detecting a charge current of the rechargeable energy storage unit and a voltage regulator for adjusting the charge voltage to the detected charge current. The charging device is characterized in that the compensation circuit has a voltage distributor between the current detector and the voltage regulator, by the dimensioning of which the compensation of the inner resistance is carried out.