NOVELTY - The method involves exchanging electrical power to an electrical power supply net over power electronics systems (3.1, 4.1). The electrical power supply net is connected with an electro-chemical energy store unit (2.1). Specific data and features of an electrochemical energy store unit and a topology of the power electronics system are transmitted into the electrical power supply net and an AC battery (1.1). The AC battery is controlled, monitored and regulated by an AC battery management (5.1). Charge and discharge current of the battery is transmitted to the electrical power supply net.    USE - Method for storing electrical power in an electro-chemical energy store unit of a lithium ion battery power plant such as hybrid power plant, and wind and solar power plants.    ADVANTAGE - The method enables transferring the specific data and features of the electrochemical energy store unit and the topology of the power electronics system into the electrical power supply net and the AC battery so as to realize battery-typical operation limit, battery-typical properties of the electro-chemical energy store unit and/or a DC-battery, thus satisfying requirements of a hybrid power plant with different battery technologies and achieving cycle strength, cycle depth and low power consumption and prolonged service life of components. The AC battery is controlled, monitored and regulated by the AC battery management so as to optimize AC battery operating points on base reference guides.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a device for storing electrical power in electro-chemical energy store unit    (2) a lithium ion battery power plant.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit block diagram of a battery power plant combined AC batteries with different topologies of power electronic modules and DC batteries with partially different battery technologies.    AC battery (1.1)    Electro-chemical energy store unit (2.1)    Power electronics systems (3.1, 4.1)    AC battery management (5.1)    Power electronics module regulating device (40.1)