Evaluation of the batteries and charge controllers in small stand-alone photovoltaic systems

In this paper, the authors report the results of long-term tests on 14 separate small stand-alone PV power systems. These tests were carried out at two separate laboratories in Albuquerque, New Mexico and in Cape Canaveral, Florida. The systems were heavily instrumented to help determine what effects voltage regulation set points have on system water loss, battery capacity lifetime and system reliability. They found that under the proper conditions, flooded Pb-acid batteries in these PV systems can achieve cycle-lifetimes comparable to manufacturer´s expectations for conventional battery applications. They also found that both the overcharge and overdischarge protection provided by the system charge controllers were necessary for proper operation of these systems. Details of the data and a number of conclusions for system designers are presented