Conductivity of electrodes decreases as active materials are
converted to lead sulfate. A new model that accounts for these
changes is proposed to predict charging and discharging characteristics of a lead-acid battery. The percolation model proposed by
Metzendorf[1]is used to calculate the conductivity as a function of
fraction of active materials present. A reasonable expression is used
to account for changes in the active area. The model predicts that
conductivity decreases very sharply only when fraction of active
materials reacted closely approaches a critical value. Thus, effects of
increased resistance of electrodes are found only in deep discharge
and when an electrode is a limiting reactant. When the electrodes
are the limiting reactants, the model makes successful predictions
of the experimental observations[10]and avoids use of empirical
expressions to modulate the rate of charge transfer. If the electrodes and acid are in a more or less even stoichiometric balance, or
if acid is the limiting reactant, models that neglect or include
variation in resistance perform equally well. It appears that effect of
additives that allow recharging of lead sulfate Liu et al.[24]may be
related to their enhancing effect on conductivity.