Control apparatus for operating a rechargeable energy storage device and for collecting operating data, as well as a method for operating such a control apparatus. The invention is described with reference to the use in a motor vehicle and to the control of the rechargeable energy storage device thereof for the supply of the electric drive of the motor vehicle. However, it should be noted that an apparatus having the features of the claims can operate rechargeable energy storage devices also independently of motor vehicles, or in stationary use.