Our new technology, the first technology in the small vehicle industry, achieves the fuel economy improvement due to the electricity through the highly efficient electricity generation and charge by the regenerative braking energy obtained during vehicle decelerating or coasting. The newly developed technologies is the regenerative braking system, which minimizes electricity generation during vehicle driving, while maximizes it during vehicle decelerating or coasting. Regenerative braking is the function to generate electric power using with the regenerative braking energy obtained during vehicle decelerating or coasting through the accelerator pedal released or the brake pedal applied. The kinetic energy from the vehicle in motion is recaptured as the electric power to be used for the electric component operation.This system includes the combination of the highly efficient lithium-ion battery in addition to the lead-acid battery for ISS (Idling Start and Stop) application and highly efficient alternator with higher output performance. The lead-acid battery installed in the conventional vehicle has the characteristic that it needs to be charged to full in order to deliver the steady supply of intended electric power. This needs the continuous alternator operation, leading to the increased fuel consumption. The highly efficient lithium-ion battery in addition to the lead-acid battery for ISS application is installed in this system. The lithium-ion battery is not required for charging until its SOC (State of Charge) is depleted. The employment of the lithium-ion battery of its characteristic eliminates the need for the continuous alternator operation. This unique system achieves the higher charging efficiency and higher electricity generation capacity in comparison to the previous model.For the small engines, the engine load factor for electricity generation is typically high. Therefore, the minimum electricity generation during vehicle driving allows the drastically reduced fuel consumption. In addition, smoother and quicker acceleration is also achieved because of the reduced engine loads.