Management of electrochemical battery storage in photovoltaic energy supply systems
Photovoltaic energy supply systems place high demands on battery storage. Operating conditions which have an adverse effect on the battery lifetime should be avoided; this is especially true for overcharging, non-uniform full-charging and deep-discharging. Good charging efficiency implies minimal overcharging and uncoupling electrolyte circulation from gas production due to overcharging the battery. To achieve identical performance of all individual cells, the possibility for separate behaviour must not exist. Therefore, the charging must be so controlled that all cells become fully charged, and that unnecessary overcharging is avoided. Supervision of system operation must be oriented towards the state of the battery. Therefore, knowledge of battery-specific operating parameters, e.g. the state-of-charge, is necessary. Supervision of the operation of the system with special consideration of battery-specific conditions is necessary to fulfil these demands. In addition to direct influence of battery power by system management, peripheral measures are sensible and important.