48V recuperation storage including a stabilizing 12V tap for HEVs

A recuperation system based on 48V components is a promising low-cost solution for hybrid electrical vehicles (HEV) to reduce CO2 emissions. A power net configuration including a 48V recuperation system contains two energy storages, 12V storage and 48V recuperation storage respectively. This paper investigates the insertion of a 12V tap to the 48V storage. Thereby, the failure safety is increased and a component downsizing is possible. Supercapacitors and lithium-ion cells are considered as storage technology for recuperation storage. First, load behavior of 12V and 48V level is determined. Then several options to connect the 12V tap to the 12V power net are investigated regarding the interaction of both voltage levels. Due to supercapacitor voltage characteristics, a dual-voltage supercapacitor storage is only possible to a limited extend. Lithium-ion batteries appear clearly more suitable.