This document is a compilation of information on lead acid batteries. The battery is the weakest part of a stand-alone PV system today. Even by using only part of the information given in this guide, the battery lifetime can be extended and the lifecycle costs of the PV system can be reduced substantially.

In most cases a modern controller in the PV system will take care of the main facts mentioned in this document. However, some details like checking the water level of the battery and cleaning of connectors must still be done manually at regular intervals. Also the right choice of battery type and proper installation is very important.

The more specific advice in this guide is written for open (also called vented) lead acid batteries, as these are still the most common type in PV systems due to their lower initial investment costs.