Learn how solar powered batteries work to provide power and what they are used for.
Typically, a bank of batteries will be used in conjunction with solar panels to provide power for a building. The number of batteries needed depends on the size of the building and the number of electrical devices to be powered. At the beginning of the solar energy movement, the typical size for solar batteries was 12 volts. Now there are 24 and 48 volt batteries that are more efficient and allow the solar panels to be placed further away from the battery bank if necessary.
Batteries used in a solar energy system are deep-cycle batteries. They discharge more of their energy over a longer period of time and have a longer life than a shallow cycle battery, such as a car battery. Shallow cycle batteries discharge a great deal of energy in a short period of time and recharge over a longer period of time. Solar deep-cycle batteries recharge as long as it is daylight.
The two types of batteries used in solar energy systems are nickel-cadmium and lead-acid. Nickel-cadmium batteries are more expensive than lead-acid batteries, but last longer, require less maintenance, and may be discharged more fully than lead-acid batteries. They are, however, expensive to dispose of because cadmium is a hazardous material. Lead-acid batteries may only discharge down to 40 or 50% of their total charge. If the lead-acid battery is not sealed, distilled water must be added to it at least once a year. The top and terminals of a lead-acid battery must be kept clean.
Lead-acid batteries should also be equalized every 60 to 90 days. Equalization involves a controlled overcharging of the battery. Monitor the battery closely during the process to make sure that no individual battery has a much higher charge than any of the others. Be sure that the battery area is well ventilated, as the process will release much gas. Be sure to refill the battery with distilled water after equalization, as water is used during the process.
Solar powered batteries work by storing the direct current (DC) energy that is created when sunlight is received by a solar or photovoltaic cell. In a solar system for a building, the energy flows from the solar cell through a charge controller. The charge controller prevents energy from flowing to the battery when the battery is fully charged. It will also provide a way to monitor how much of a charge the battery has. The charge controller will also prevent the battery from being drained down so far that it cannot be recharged. An inverter must also be used in order to convert the current from the battery into alternating current (AC) for household items requiring AC power, such as lamps. Items requiring DC current may use power that comes directly from the solar cell through the charge controller or the battery.
Initial costs for a solar battery depend on the type of battery being purchased. A mid-sized battery will cost anywhere from $200 to $1000. An industrial battery will cost several thousand dollars. Smaller batteries, such as marine or golf cart batteries, might cost less than $100. Be sure to add freight and handling costs to get a true final price.
Replacement and disposal of the batteries represents an ongoing cost in the solar energy system. Solar batteries must be replaced after several years. Although industrial lead-acid batteries may last as long as 20 years, intermediate sized batteries will last approximately 7 to 12 years. The smallest batteries, such as those used by a golf cart, may only last three to five years. Nickel-cadmium batteries last longer in years but not in power cycles. All batteries must be disposed of properly. This can be quite expensive if the battery is nickel-cadmium.
Fortunately, new technologies are lowering the costs and raising the efficiency of solar batteries all the time. Over the long run, this will reduce the cost of batteries as a component of a solar energy system, making solar energy a more viable option for many people.
