In order to charge a battery with a particular chemistry, a precise voltage and current profile is necessary, or part of the capacity may be lost and the battery could be damaged or destroyed. To create this charging profile, special charge controllers are used which can generate the necessary voltage and current from one DC source. Precise information about the state of charge and aging of batteries is often needed. In high-voltage applications such as motors in electric or hybrid vehicles, a series of several battery cells is needed for energy supply. Production tolerances, self-discharge and uneven temperature distribution in the battery system means that the state of charge of the individual cells can diverge with time. This leads to a loss of capacity in the entire system which must be compensated by so-called cell balancing.
The Fraunhofer Battery Alliance is developing highly-integrated charge controllers, from simple analogue controllers to intelligent microprocessor-driven digital controllers. These devices are optimized for use with smaller external components and also for batteries with different chemistries.
Monitoring systems, and systems for the passive and active cell balancing of multi-celled battery systems, are a particular focus. Algorithms are being developed which use mathematical modeling to accurately predict the remaining capacity of batteries. This enables the typical battery parameters SOC (state of charge), SOH (state of health) and SOF (state of function) to be determined. A further topic is microelectronic devices with minimum power loss for application in battery management systems.
The Battery Alliance develops the necessary subcomponents such as charge controllers and ADCs, and can also use commercial products to construct complete energy supply systems.
Standards such as SBS (Smart Battery Standard), SMBus (System Management Bus) and PMBus (Power Management Bus) are used to achieve compatibility with commercial systems.
Application fields for the developed battery management systems include electric and hybrid vehicles and mobile electronic devices.
We also test battery management systems and batteries with a professional battery testing system, which is also used for battery modeling.