This paper develops an energy-based control strategy for a lithium battery /supercapacitor hybrid energy storage system. The lithium battery set is interconnected in parallel with the supercapacitor module which is linked with a buck-boost converter downstream. The performance maps measured from experiments are utilized to form a control-based nonlinear system model. The control modes can be separated into the hybrid mode and the charging mode. Using a global explorative approach, under various conditions of battery state-of-charge, supercapacitor state-of-charge and loading power, the energy distribution (power split) control can be derived in these two modes. With such energy management, the consumed energy of this hybrid energy storage system is minimized.