Battery systems for high voltages are comprised of a number of individual battery cells in order to attain system voltages of between 50 and 400 volts. The individual cells must be monitored separately by the battery management system to make use of the maximum available capacity of each cell and to guarantee safe operation. Furthermore, different battery technologies provide different cell voltages and peak currents and so the number of required battery cells depends on the battery technology in use. Thus, the battery management system must always be tailored to the specific number of individual battery cells and cell configurations.
The flexible battery management system of Fraunhofer IIS is able to work with different cell numbers and combinations. It can monitor any series or parallel connection of battery cells.
A small electronics module at each cell detects cell parameters such as voltage and temperature. This cell module controls active balancing to ensure an equal state-of-charge of the different cells. Optimized bus communication between these electronic modules minimizes the need for wiring between the cells. Superordinate module controllers allow any combination of different modules, either in parallel or in series connection. Power switches in the module controllers execute the safety functions. The flexible battery management system is also capable of precisely predicting the remaining capacity and the state-of-health by means of shunt- or resistance-based current measurements. This allows run time or range forecasts to be made, which eliminates the need for a safety buffer. The advantage of this is that the maximum capacity of the battery cells can be used to its fullest.