Other failure modes in flooded cells are related to grid corrosion and acid stratification which are not discussed in the present paper. The increasing demand from lead-acid batteries to operate in deeper depth-of-discharge namely 20e30% DOD, emphasizes further the above described problem of sulfation. Due to sulfation, SLI batteries are planned to work at a shallow DOD. Their cycle life becomes very limited when they are forced to operate at 20e30% DOD. In order to solve the sulfation problem in deep cycling of SLI batteries, carbon materials were added into the active-masses of their electrodes