Development of Hybrid Electric Vehicles (HEVs) and Battery Electric Vehicles (BEVs) is gaining traction across all geographies to help meet increasing fuel economy regulations and as a pathway to offset concerns due to climate change. But HEVs and EVs have so far been a nascent market for India.These technologies have primarily shifted towards Lithium-ion batteries (LIB) for energy storage due to its high energy and power densities. In order to make actual business sense of these technologies, of which, battery is a major cost driver, it is necessary for these batteries to provide similar performance and life expectancy across the operating boundary of the vehicles, as well as provide the requirements at a competitive cost. In other words, the LIBs have to sustain the normal life cycle requirements and withstand wide range of storage temperatures that the conventional gasoline/diesel vehicles have been good at and still ensure good life. The Indian ambient ranges from minus 5°C in some areas to greater than 50°C in other areas with relative humidity up to 100% in most of the coastal areas where there is very high vehicular density. Hence it is reasonable to state that the batteries have to consistently withstand high temperatures and high humidity and still satisfy the life requirements.This paper will summarize the approach that has been taken to estimate cycle & calendar life of NMC (Nickel Manganese Cobalt Oxide) based Li-Ion high power battery used for mild hybrid application based on usage, drive & environmental profile which was derived for typical Indian conditions.