Intermediate storage facility for battery units

Method for storing a battery unit in an intermediate storage facility, having a multiplicity of battery units, having an inverter and/or rectifier, a power supply system and a controller, wherein

• each battery unit has at least one chargeable battery cell and a battery management system for monitoring and regulating the battery cell,
• at least two battery units are connected electrically in series to form a battery chain,
• the battery chain is electrically connected to the power supply system via the inverter and/or rectifier, and
• the controller has a communication connection to all the battery management systems and is configured to bring about charging of the battery cell and/or of the battery unit with electrical energy from the power supply system, to feed electrical energy in to the power supply system by discharging the battery cell and/or the battery unit and/or to bring about connection and/or disconnection of the battery unit to or from the inverter and/or rectifier, and comprising the step:
• exchanging all the battery units of each battery chain at the latest after 14 days and at the latest after an energy throughput of the battery chain of ≦3000 kWh.