Modelling battery charge regulation for a stand-alone photovoltaic system

A new model for the charge and discharge characteristics of a lead–acid battery is presented which aims to model the effect on capacity of variable charge and discharge rates. This model has been implemented using the circuit simulator PSPICE, and is used to investigate the effect of the charge controller strategy on the performance of a stand-alone PV system. It is shown that a simple limit on charging voltage is probably adequate to achieve a high state of charge, although a two-level regulator may be needed to maintain battery condition. The benefits of maximum power point tracking are also investigated.