Composite Hybrid Energy Storage System utilizing Capacitive Coupling for Hybrid and Electric Vehicles

An innovative architecture is presented that combines energy-dense and power-dense battery packs through a supercapacitor that provides capacitive coupling and a low-power DC-DC converter that provides energy balancing. A sizing algorithm is developed to optimize the design of such systems for plug-in hybrid and battery electric vehicles (PHEVs and BEVs). The proposed composite architecture extends vehicle range and battery lifetime by fully utilizing the capabilities of energy-dense and power-dense battery chemistries. A power-dense battery is coupled to an energy-dense battery using a small supercapacitor module that naturally distributes the system current between the two packs, requiring no additional contactors or full-power processing DC-DC converters. The proposed algorithm provides a tool for designing the composite architecture to achieve maximum weight reduction under given conditions for both ideal and practical scenarios. A design example is provided based on a PHEV with 68-mile range using the US06 drive cycle. The design achieved a 42% weight reduction when compared to a similar design with a conventional single chemistry battery system. Experimental results of a 1.5 kW, 0.2 kWh small-scale prototype with 25 Ah NMC and 2.9 Ah LTO battery cells and a 30 F supercapacitor verify the natural distribution of system current between the energy-dense and power-dense packs.