Optimization of a 12V Dual-Battery-System for Applications in Mild-Hybrid Vehicles

Abstract:
The lead-acid batteries mainly used for energy storage in conventional vehicles today have to handle both high power applications and charge acceptance. Supporting the lead-acid technology using a small, high power lithium-ion battery connected in parallel yields great benefits. Additionally this dual battery system enables new efficiency functions, such as ‘engine-off coasting’ for more efficient vehicles. Besides strategy and battery properties, the batteries’ connection to the power network is crucial for the duration and availability of these new efficiency functions. Given that there is a close interaction between these factors, we present in our study a simulation-based optimization method to obtain the best trade-off between function-availability, function-duration, system size and weight. Vehicle measurements prove the ability to simulate scaling of the battery and wiring harness and help in developing new and optimized vehicle power systems regardless of topology or voltage level.