Lead Acid Batteries (LABs) in the Micro Hybrid vehicle have to work in Partial State of Charge (PSoC) conditions, where the negative plates may develop high sulfation leading to the battery death. In order to reduce this sulfation, Graphitized Carbon Nanofibers (GANFg) at 0.10% and two types of Organic Expanders (OEs) were used as additives for the negative plates. These fibers were previously dispersed with a certain amount of OEs. Five mixtures were selected, and the corresponding negative plates were prepared. 2 V / 1 Ah cells were assembled and tested, together with the physicochemical properties of the plates. During the formation of the cells, GANFg are thought to be integrated into the NAM skeleton where would improve the NAM energetic structure. As a result, the use of GANFg slightly enhanced the capacity and the cold cranking ability, although this last one was essentially dominated by the OEs concentration. A lower OEs concentration led to higher charge acceptance, and the use of GANFg involved a higher water loss. However, the water loss rate was considered low in comparison with other carbon materials. GANFg addition increased the cycle life of the cells during the 17.5% DoD cycling test (at PSoC).