The operating environment, manufacturing variability, and use can cause different degradation mechanisms to dominate capacity loss inside valve regulated lead-acid (VRLA) batteries. If an aging mech. Lead-acid is the most widely used chemistry for batteries in stationary and hybrid applications,. 2.1. Experimental setupThe dead battery was cycled on an Arbin BT2000 for 31,560 cycles using a duty cycle representative of an electric locomotive opera. The test results identify sulfation in one cell and water loss in three cells as probable degradation mechanisms. The capacity of the dead VRLA battery was limited largely by sulfation in on. EIS and pulse train responses reveal the non-uniformity among the cells in the aged battery and display the distribution of cell resistance and capacitance, indicating the relative health co. The authors would like thank the Norfolk Southern Corporation and the Department of Energy for financial support for this work. The authors would also like to thank Lei Cao, Jun Gou, D.