A model is set up for a time-dependent description of currents, polari
zations, state-of-charge and acid concentration with high spatial reso
lution in a flooded lead/acid battery. The detailed description of all
relevant parameters for a battery under real operating conditions all
ows the use of results obtained under well-characterized laboratory co
nditions for different ageing effects. Models of acid stratification,
vertical current distribution in the electrode, and description of pol
arizations, concentrations and state-of-charge in the porous electrode
s are necessary for any ageing model. First results show the very seve
re conditions for the lower part of the electrode under typical operat
ing conditions in photovoltaic power supply systems. The work aims at
a quantitative ageing model for batteries in such systems.