Modelling of local conditions in flooded lead/acid batteries in photovoltaic systems

A model is set up for a time-dependent description of currents, polarizations, state-of-charge and acid concentration with high spatial resolution in a flooded lead/acid battery. The detailed description of all relevant parameters for a battery under real operating conditions allows the use of results obtained under well-characterized laboratory conditions for different ageing effects. Models of acid stratification, vertical current distribution in the electrode, and description of polarizations, concentrations and state-of-charge in the porous electrodes are necessary for any ageing model. First results show the very severe conditions for the lower part of the electrode under typical operating conditions in photovoltaic power supply systems. The work aims at a quantitative ageing model for batteries in such systems.