Storage batteries are the heart of all stand alone wind/PV or inverter electrical systems. Their function is to balance the outgoing electrical requirements with the incoming power supply. They offer a reliable source of electricity which can be used when solar or wind power is not available. Batteries are able to provide short term power output many times higher than the charging source output. In diesel generator systems they allow power to be available 24 hrs/day but mean that the generator need only run for short periods to charge the battery.
Battery Types
Lead Acid Batteries
Lead acid batteries are the most common type of energy storage. All lead acid batteries are based on the same lead/sulphuric acid chemical reaction, however, they have evolved into different types-each designed for a specific need. Smaller batteries look like big car batteries and contain several cells in tough plastic cases to give 6V or 12V with capacities up to ~ 200Ah. They are either flooded cell types: with a vent for gassing and topping-up with distilled water; or sealed/gell types: with an immobilized electrolyte. Larger battery banks are usually made up of flooded 2V cells ranging in capacity of ~100Ah to several thousand. Sealed types are also available. Some flooded cell batteries using tubular positive plates instead of flat plates have longer life.
Nickel Cadmium Batteries
These are manufactured in many sizes. Sealed ones have very small capacities but are useful for self contained lights. The larger wet nicad is ideal for wind/solar energy storage. They require little maintenance; can be 100% discharged; left in any state of charge without damage; withstand overcharging temperature extremes. However, they are several times the price of lead acid batteries and more difficult to recycle.
We use Classic batteries manufactured by Exide.