Field investigation of the relationship between battery size and PV system performance

Four photovoltaic-powered lighting systems were installed in a National Forest Service campground in June of 1991. These systems have identical solar cell arrays, loads and charge controllers. The only difference was in the rated capacity of the battery bank for each system. The battery banks all use the same basic battery as a building block with the four systems utilizing either one battery, two batteries, three batteries or four batteries. The purpose of the experiment is to examine the effect of the various battery sizes on the ability of the system to charge the battery, energy available to the load, and battery lifetime. Results show an important trend in system performance concerning the impact of charge controllers on the relation between array size and battery size which results in an inability to achieve the days of battery storage originally designed for