The extension of traction batteries of High Voltage Systems with supercapacitors is regularly discussed as a possibility to increase the lifetime of the lithium-ion cells as well as the performance of the storage systems. As part of the R&D project SukoBa, carried out by AVL together with the project partners Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) and Skeleton Technologies, a simulation model of a hybrid energy storage system consisting of a Li-ion battery and a supercapacitor was developed. The spotlight was set on the following aspects:
• Assessment of different system topologies
• Definition of application-specific load profiles for different use cases
• Definition of suitable evaluation parameters
• Development of a control strategy with focus on slowing down the ageing effects of the battery cells (patent pending)
The virtual modeling of the system was carried out in the AVL CRUISE™ M software, which offers the possibility of predictive analysis of battery electric vehicles (BEV) and battery systems, including their ageing behavior. The open system framework enabled the implementation of supercapacitors and thus the comparison of the hybrid system with a conventional battery system. With the hybrid energy storage system (HESS), a technical advantage up to 20% was demonstrated in the form of a slowdown in battery ageing and thus an extension of battery life. The economical assessment showed that due to the significant additional costs, the rollout of this technology in series production is currently questionable for several target applications and needs proper assessment. Optimization potentials, such as the consideration of the cycle stability of supercapacitors or a possible reduction in the size of the cooling system, as well as a price reduction of supercapacitors due to new highly automated production facilities can make this topology economical. The project results now provide AVL with a tool that can be used to quickly assess whether hybrid energy storage architectures are suitable in the early offer or concept phase and which priorities need to be considered in further development.