Energy Research Centre, An Najah National University, Nablus, P.O. Box 721, WestBank, Palestine, Israel

Received 7 October 2003; 

Revised 18 December 2003; 

accepted 20 December 2003. 

Available online 9 April 2004.

Abstract

Storage batteries are indispensable in all stand alone solar electric systems (PV power systems). Their efficiencies and life times affect significantly the overall PV system performance and economics. Batteries specified especially for use in PV systems have to be distinguished with standing of very deep discharge rate and high cycling stability.

Ordinary batteries being marketed world wide for use in automobile, are mostly not appropriate for PV power systems. The most important characteristics of lead–acid batteries are presented and discussed in this paper. Moreover, the paper illustrates an experimental procedure for developing an algorithm for determining the ampere–hour capacity of batteries operating in PV systems. This algorithm enables determining the state-of-charge of a battery by measuring voltage and electrolyte-specific gravity at definite temperature and is applicable also for large battery storage systems.

Author Keywords: Electrical energy storage; Photovoltaic power systems; Storage batteries