The paper deals with oscillating generators driven by free-piston engines. The original free-swinging piston engine with oscillating rotary generator distinguishes by its compactness, minimum frictional losses, full-balanced mechanical system, possibility of the four-stroke operation of the internal combustion engine, possibility of the multi-fuel operation of the engine (including possible version of the Stirling engine), optimal magnetic circuit of the electrical generator etc. Because the engine can optimally operate over whole range of the output power, it enables to improve electrical system of the hybrid vehicle by usage of supercapacitors (instead of the battery). In this way the competitive hybrid-electric vehicle and electrical vehicle with effective range extender can be created.