Investigators have confirmed that applying a small amount of mechanical pressure, approximately 1 bar (10(5) Pa), to the face of the positive electrode can dramatically increase the life of deep cycled, lead acid batteries. In this paper, we calculate the pressures required to stabilize the active material in the positive electrode based on the "Agglomerate of Spheres" model. The calculations agree closely with the experimental observations. In addition to these calculations, we also provide another possible interpretation of the "Agglomerate of Spheres" model and give an improved estimate for the surface tension of lead dioxide, an important physical quantity for the model. (C) 2000 Elsevier Science S.A. All rights reserved.