The aim of the project „Open Battery“ is to develop a construction kit with all devices and modules that are needed to build a photovoltaic (PV) system with energy storage for use in households, small farms or small industrial establishments. The operation of the system is considered not only in Germany or Europe, but also in North Africa and countries of the global south. The development of each module has to bear that in mind. For instance, parts should be easily available and designs should be reproducible with simple means and resources. All designs are carried out under CERN hardware license in order to leave room for future development. A specifically developed programmable BMS makes it possible to use 2nd-life cells or batteries.
One of the systems’ modules is needed to distinguish between consumption and supply. It provides a directional output as well as an electricity meter for AC bi-directional power measurement. With that module and its output signals, it will be possible to control an inverter and a maximum power point tracker (battery charger) in multiple ways, according to solar yield, present and future electricity demand, state of battery charge and legal requirements in a particular country or environment.
A battery cabinet is used to accommodate one or more batteries. A DC-rail in the back of the cabinet offers an easy option to expand storage capacity.
Currently, a sample system has been installed at TU Berlin and connected to the building power supply. The system is designed to be flexible, it will be used for drop-in replacements of the different components. This provides a comfortable development environment for final theses, dissertations and common research. As long as there’s no modules’ change and no switching operation, the solar energy is permanently being fed in the grid and no other expensive lab environment (eg. high power AC loads, 3-phase chargers or PV-simulators) is needed.