Automotive batteries are rechargeable batteries that supplies electric energy to automobiles, most essentially for automotive SLI (starting, lighting and ignition) system. Automotive batteries also provide power to automobile accessories such as radio, music players, air conditioners, wipers and charging plugs. Furthermore, the battery also serves as voltage stabilizer by absorbing abnormal transient voltages in vehicle electrical system. Based on the chemical composition the automotive battery market is broadly categorized in five different market segment, lithium ion (Li-ion), nickel–metal hydride (Ni-MH), nickel–cadmium (Ni-Cd), gasoline and lead-acid. The energy density per unit weight (Wh/kg) is highest in Gasoline batteries followed by Li-ion and Ni-MH and is least in Lead-Acid batteries. Lead-Acid batteries are an aging automotive battery technology. Due to its simple or mature technology coupled with fluctuating lead prices in last few years, much of the automotives batteries research is focused on drifting away from this technology.