NOVELTY - The interface (42) connects a participant i.e. monitoring module (46), with another participant i.e. control unit (34) of a control device (30), where the participants of the control device are serially interconnected in an annular communication arrangement (40). The control device controls an electrical energy module (36). The control unit and the monitoring module function as a master and a slave and comprise two integrated circuits, respectively. The participants are interconnected over a capacitor, a protective resistor, an optical coupler and/or a transformer.    USE - Communication interface for connecting a participant i.e. monitoring module, and control unit, of a control device of an electrical energy module such as electrical energy storage unit i.e. lithium-ion battery, energy producer i.e. solar cell, and/or energy converter i.e. fuel cell (all claimed), that is utilized for driving an electric motor in an electrical car and a hybrid car. Can also be used for a motor car.    ADVANTAGE - The interface connects the monitoring module with the control unit of the control device, where the monitoring module and the control unit of the control device are serially interconnected in the annular communication arrangement, thus enabling the interface to be utilized in the communication arrangement for transferring data between the monitoring module and the integrated circuits with requirement of reduced number of pins and with high data rate in a simple and inexpensive manner.    DETAILED DESCRIPTION - The integrated circuits are designed as microcontrollers, application-specific integrated circuits (ASICs) or field programmable gate arrays (FGPA). INDEPENDENT CLAIMS are also included for the following:    (1) a control device for controlling an electrical energy module    (2) a method for monitoring an electrical energy module.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a control device of an electrical energy module.    Control device (30)    Control unit (34)    Electrical energy module (36)    Annular communication arrangement (40)    Communication interface (42)    Monitoring module (46)