Batteries
Solar set-ups not connected to the grid use batteries to store that day's unused solar energy. This energy is used during night or very cloudy days and if the grid is down. The size of the battery bank depends on the storage capacity required, the maximum discharge rate, the maximum charge rate, and the minimum temperature at which the batteries will be used. Adding batteries increases the cost and reduces the efficiency of the system. Batteries must be monitored and maintained regularly and replaced or refurbished every approx 5-20 years, dependent on battery technology.
4 Basic Types of Batteries
- RV / Marine / Golf Cart: deep cycle for very small systems.
- Flooded types
- Gel
- AGM - Absorbed Glass Mat batteries are considered very good. They can be stored in-doors where temperature changes won't effect the power supply.
Industrial strength : Flooded, Gel, and AGM sealed batteries.
You also need to purchase a controller to keep the batteries from being overcharged. Since the brighter the sunlight, the more voltage the solar cells produce, the excessive voltage could damage the batteries. A charge controller maintains the proper charging voltage on the batteries.
Most quality charge controller units have what is known as a 3 stage charge cycle; BULK, ABSORPTION, FLOAT. The Charge Controller is installed between the Solar Panel array and the Batteries where it automatically maintains the charge on the batteries using the 3 stage charge cycled. The Power Inverter can also charge the batteries if it is connected to the AC utility grid or in the case of a stand alone system, your own AC Generator.
