This paper presents a review and description of conventional car power system, as well as a review of new technologies and power supply variants. Supercapacitors, as a fast developing technology, are an alternativesolution to the lead acid battery with numerous limitations, in order for complete replacement as a secondary energy storage in conventional cars. The second chapter describes the power supply system in conventional vehicles with description of operating principle of the vehicle battery system and vehicle battery charging system. In the third chapter, the engine starter is described as the highest power consumpting device of the vehicle, along with its working principle of starting the internal combustion engine and solenoid operating principle. The fourth chapter provides a brief overview of lithium ion battery technology and comparison with other energy storage technologies. The fifth chapter describes the structure and operating principle of the supercapacitors, with overview of voltage balancing as an essential task in the application of supercapacitors in series connection. Chapter six describes the design of a supercapacitor module and a lithium ion battery pack used in the practical part. Chapter seven deals with the results of measurements and the description of measured waveforms of current and voltage on individual components of the car's power supply. Eighth section describes the technical comparison of variants of the power supply along with a proposal for a power supply solution with a brief overview of the limitations of some variants. Chapter nine describes the economic aspect of applying supercapacitors as a component of the power supply system in conventional cars with a brief overview of price accessibility and long-term cost-effectiveness.