The distributions of current and potential on the automotive positive plate have been studied. In the early stage of the discharge, the distributions of the current density, potential, and polarization resistance are uniform. In the later stage, however, the polarization resistance of the active mass increases very rapidly at the bottom and on the top of the plate. It causes the polarization to become very high and makes the current drop rapidly in these regions. It is also found that at the beginning of the 3 C discharge, the higher current density appears in the lower part rather than in the upper part of the plate, which is different from the conventional viewpoint. This may be due to the improper formation and overcharge of the plate. (C) 2003 Elsevier B.V. All rights reserved.