Series Hybrid vehicles

A series hybrid is similar to an electric vehicle with an on- board generator i.e. range extended electric vehicle. The vehicle runs on battery power like a pure electric until the batteries reach a predetermined discharged level.  In a series hybrid electric vehicle, an electric motor is the only means of driving the wheels. The motor obtains electricity either from a battery pack or from a generator powered by an engine (APU-Additional power Unit). The engine does not need to speed up or slow down as load varies. As a consequence, the engine can run at its optimum efficiency (best engine efficiency zone), thereby greatly reducing fuel consumption. To gain most advantage in efficiency from using a small engine, series drive train typically use relatively large battery packs. But batteries and motor cost more than engines for the same amount of power, so series hybrids are more expensive. The generator needed to produce electricity from the engine also adds to the cost. Series hybrids are advantageous under slower operating conditions characterizes by stop –and- go driving.  For this reason, most of the serried hybrids currently under development are for buses or other heavy duty urban vehicles. The batteries in a series hybrid are recharged both by the engine/generator set and by storing some of the energy that is normally lost during braking. Examples of this kind of arrangement are Series-Hybrid bus by Toyota in JAPAN, General Motor’s Chevy Volt, AFS Trinity SUV etc. The schematic diagram of Series Hybrid Vehicle is given in Fig. (a), (b).