Graphene nano-sheets such as graphene oxide, chemically converted graphene and pristine graphene improve the capacity utilization of the positive active material of the lead acid battery. At 0.2C, graphene oxide in positive active material produces the best capacity (41% increase over the control), and improves the high-rate performance due to higher reactivity at the graphene/active material interface. The in-situ changes in the graphene structure and oxygen states support these, as well as higher adsorptive surface area, better graphene/lead dioxide interfacial reaction, and finer & highly utilized lead dioxide phases. The multi-scale physio-chemical mechanisms improving capacity and cycle life is thus: Electrolyte/ionic permeation improvements results from increase in pre-formation porosity, and higher interfacial reactivity at gel zone which enhances active material reversibility. Our ion transfer model reveals the optimized redox reaction in the electro-active zone of graphene enhanced active materials. This work shows the best enhancement in the capacity of lead-acid battery positive electrode till date.