An inverter apparatus comprising: - a DC voltage link, - an input stage connected to the DC voltage link and configured to receive DC electric power from a DC power generator for loading the DC voltage link, - a DC/AC converter connected to the DC voltage link and configured to feed AC electric power into a power grid, - a bidirectional connection configured to connect a battery to the DC voltage link, to load the battery out of the DC voltage link, and to load the DC voltage link out of the battery, and - a controller configured to operate the DC/AC converter and, dependent on present values of relevant parameters of the battery, to operate the bidirectional connection, wherein - the controller is connected to an interface configured to receive the present values of the relevant parameters of the battery from a battery monitoring unit associated with the battery, - the relevant parameters of the battery issued by the battery monitoring unit and received by the interface include working data related to at least a state of charge of the battery and safety data indicating a safety state of the battery, - the controller is configured to consider the working data in operating the bidirectional connection, - the controller is configured to be commanded by the safety data to stop further operation of the bidirectional connection and disconnect the battery by opening suitable switches of the bidirectional connection, and - the interface comprises separate interface units (22, 23) for receiving the working data and the safety data, characterized in that the controller is configured to receive the safety data as a safety signal only indicating safety of the battery at a signal level within a predetermined safety level range and/or at a signal repetition frequency within a predetermined safety frequency range and as soon as the safety signal is no longer indicating safety of the battery, the operation of the bidirectional connection is interrupted and the battery is disconnected. - a DC voltage link, - an input stage connected to the DC voltage link and configured to receive DC electric power from a DC power generator for loading the DC voltage link, - a DC/AC converter connected to the DC voltage link and configured to feed AC electric power into a power grid, - a bidirectional connection configured to connect a battery to the DC voltage link, to load the battery out of the DC voltage link, and to load the DC voltage link out of the battery, and - a controller configured to operate the DC/AC converter and, dependent on present values of relevant parameters of the battery, to operate the bidirectional connection, - the controller is connected to an interface configured to receive the present values of the relevant parameters of the battery from a battery monitoring unit associated with the battery, - the relevant parameters of the battery issued by the battery monitoring unit and received by the interface include working data related to at least a state of charge of the battery and safety data indicating a safety state of the battery, - the controller is configured to consider the working data in operating the bidirectional connection, - the controller is configured to be commanded by the safety data to stop further operation of the bidirectional connection and disconnect the battery by opening suitable switches of the bidirectional connection, and - the interface comprises separate interface units (22, 23) for receiving the working data and the safety data,