Provided is an electric storage battery including a jelly roll type electrode assembly having a mandrel. The mandrel includes a positive portion, a negative portion and a removable portion. In some embodiments, the mandrel is planar having two faces with a groove on each of the positive and negative portions. The grooves can be on the same or different faces of the mandrel. The grooves are dimensioned to accommodate a positive and negative feedthrough pin. The electrodes are wrapped around the mandrel using the removable portion to wind the mandrel. Once wrapped, the removable portion can be detached. The positive portion and the negative portion are left in the electrode assembly insulated from each other. The mandrel allows tighter wrapping of the jelly roll assembly, increasing battery miniaturization and also results in electrode assemblies in which after-placement of tabs does not result in burrs or shorting.