The hybrid system is basically a mild-hybrid and consists of a 48V lithium-ion battery, integrated Starter Generator (ISG) and 48V-12V (DC/AC) converter to power components requiring low voltage, including lights, audio and air conditioning. The ISG acts as both generator and starter motor. This assists the petrol engine during acceleration. As you decelerate or brake, the car produces energy and this energy is saved in the lithium-ion batteries. This stored electricity is then used through an electric motor to help produce power when accelerating. This saves the engine needing to be used as much and thus saves fuel and reduces C02 emissions. We would not at this stage have any worries reference the long term life of the Lithium battery .