Different carbon blacks were added with quantities in between 0.2% and 2% to the negative active material of flooded lead-acid batteries. By scanning electron microscopy it can be shown that the carbons differ in aggregate structure and particle morphology. In order to test the effectiveness of the carbon blacks, the batteries were subjected to cycle tests with 17.5% depth of discharge. Batteries with carbons in the negative active masses display drastically decreased sulfation of the negative active masses. An extension of the battery lifetime by a factor of 2 could be determined compared to conventional batteries. Furthermore it was noticed that the battery cycle life is influenced by the dispersion properties of the carbon particles into the negative active mass. Particles which are homogenously distributed into the negative active mass are able to act over the whole plate and therefore affect cycle life positively.