PREDICTING THE SERVICE LIFETIME OF LEAD-ACID-BATTERIES IN PHOTOVOLTAIC SYSTEMS

In nearly all photovoltaic (PV) systems, solar modules are used to charge a lead/acid battery, which in turn supplies power to the load. Charging and cycling conditions are quite different from those normally encountered in lead/acid battery applications, and prediction of service life needs to take these differences into account. Depending on the nature of the actual application, either cycle life or corrosion resistance (as measured by float-charge lifetime) can be the dominant life-determining quantity. Alternatively, life may be shortened prematurely by an occurrence of a special condition (such as a very deep discharge without rapid recharging). Acid stratification can cause life-shortening effects, and there is evidence that the distribution of stratification is different in PV systems and those applications where a full overcharge is given.