Batteries for Stand-Alone Systems
Batteries store electricity for use during times that your system is not producing electricity due to resource unavailability. Batteries are most effective when used in wind and photovoltaic systems (variations in hydro resources can be more seasonal in nature, so batteries may be less useful).
Batteries store the electricity produced by your small renewable energy system for later use.
Photo credit: Warren Gretz
The "deep-cycle" (generally lead-acid) batteries typically used for small systems last five to ten years and reclaim about 80% of the energy channeled into them. In addition, these batteries are designed to provide electricity over long periods, and can repeatedly charge and discharge up to 80% of their capacity. Automotive batteries, which are shallow-cycle (and therefore prone to damage if they discharge more than 20% of their capacity), should not be used.
The cost of deep-cycle batteries depends on the type, capacity, climate conditions under which they will operate, frequency of maintenance, and chemicals used to store and release electricity. Wind or photovoltaic stand-alone system batteries need to be sized to store power sufficient to meet your needs during anticipated periods of cloudy weather or low wind. An inexpensive fossil fuel-powered back-up generator can be used to cover unanticipated or occasional slumps in the renewable resource.
For safety, batteries should be located in a space that is well ventilated and isolated from living areas and electronics, as they contain dangerous chemicals and emit hydrogen and oxygen gas while being charged. In addition, the space should provide protection from temperature extremes. Be sure to locate your batteries in a space that has easy access for maintenance, repair, and replacement. Batteries can be recycled when they wear out.
Contact your system supplier for information on sizing your battery pack to meet your specific needs.