Cars or vehicles are the dominant modes of transportation in the contemporary world and different vehicles are powered by different resources to ensure their efficient functioning. The term hybrid cars or hybrid vehicle is used to denote a vehicle which functions with the aid of two or more power resources which are mandatory for its working. These multifarious power sources which are instrumental in its functioning include internal fuel cell or internal combustion engine, with an on-board rechargeable energy storage system also referred to as RESS. It is essential to note here that one of the prevalent demerits of any fuel run vehicle is its emission and excessive carbon emission increases pollution levels which affect not only the surrounding environment but also takes its toll on human health. Therefore, in such cases, hybrid vehicles are more often preferred as it has been revealed through extensive experimentation that the level of emission in case of hybrid vehicles is very low compared the emissions produced by traditional internal combustion engine vehicles and in the face of continually rising fuel prices, these hybrid vehicles are useful in maintaining better fuel economy. This is due to several factors. The hybrid vehicles have enormous battery storage capacity which enables them to make use of as well as store recaptured energy. Moreover, the hybrid cars are considered as extremely suitable for running on modern roads as it provides suitable conditions to run under high traffic situations. This is because the working of the diesel engine or gasoline is terminated during idle periods or traffic stops therefore preventing the unnecessary loss of fuel resources. Apart from environmental pollution, sound pollution is also a growing problem and in this case too hybrid cars have an edge over other kinds of vehicles as the level of nose emission in these cars is also quite low.

There are various kinds of hybrid vehicles. The Battery Electric Vehicles or BEVs may at times posses such batteries which can be recharged while the vehicle is in motion. The Hybrid Electric Vehicles or HEVs are the most prominent among the various hybrid vehicles and in fact the term hybrid vehicle is often used to denote merely Hybrid Electric Vehicles. These hybrid electric vehicles possess internal combustion engines, diesel engines run by various fuels or gasoline apart from possessing electric batteries to boost the electric motors. Another prominent variant of the hybrid vehicle in recent times include the Plug-in Hybrid Electric Vehicle or PHEV.