Slow, steady discharge of the common lead-acid cell is analyzed without assuming local electroneutrality. In this limit, the rate of electrolyte depletion is uniform in space and in time. For each ionic flux, the chemical reactions at the two electrodes impose boundary values; for slow, steady discharge, the fluxes vary linearly between these values. This leads to a linear variation in the electric field and the ionic density gradients. About half of the voltage drop across the cell is quadratic in space, due to a nonzero bulk charge density; in steady discharge the electrolyte is not merely a resistor. The steady-discharge resistance is about half the initial, resistorlike, resistance.

• Received 2 January 1996

DOI:https://doi.org/10.1103/PhysRevLett.76.4849