Solar controllers are rated in amps and volts. Thus, the solar controller must have the capability to accommodate the current or amperage and volts emitted from the solar panel. Batteries can be overcharged and ruined. Excessive discharge can also damage the battery. The controller is set between the electrical solar panel and the storage batteries for protection from overcharging or undercharging of the batteries. The purpose of the controller is to match the current (amperage) and voltage (force of the current) of the solar panel with the charging capacity of the batteries. The battery fully charged the controller cuts off the current from the solar panels. The best controllers also have a low voltage cut off which prevents the battery from being drained of electricity below the point of no recovery.
Electrical solar storage batteries are different than automobile batteries. They are built to endure the type of charging and discharging associated with solar electricity collecting. There are basically three kinds of batteries for solar electricity storage: flood lead-acid; sealed absorbent glass mat; and gel-cell. The flood lead-acid batteries do not cost as much, but require special maintenance, such as having to add distilled water to replenish water losses during charges. Sealed absorbent glass mat batteries are the most used. They do not require special maintenance, are kept at full charge, and are especially designed to function in a bank in tandem with other batteries. Gel-celled batteries do not freeze. They are better to use where excessive cold predominates.
The number of batteries needed depends on the electrical load expected to be sustained and for how long. For an off-grid system, the typical aim is to store an ample supply of electricity for continuous day and night time use, as well as enough storage for one to three cloudy days. For the average house of 1500 to 1800 square feet, this will be an estimated 17 to 19 twelve volt batteries.
Where multiple batteries are used, they are tied together by cables connecting the positive to positive and negative to negative posts. Electrical energy is stored in batteries by means of a chemical reaction. For this reason solar electrical storage batteries pose danger when not handled and stored right. Explosion, serious chemical burns, and electrocution are possible by mishandling solar electrical batteries. Electrical solar storage batteries should be housed in a well-ventilated place that is clean and dry; and the area secluded from children and unauthorized others who are not familiar with the possible dangers. You should not be put off or dissuaded from your interest in and pursuit of electrical solar energy because of the potential dangers. By and large, the benefits are immense and dangers reduced to nothing when the equipment is properly handled.
The batteries are connected to an inverter.
The inverter is the essential link between the electrical solar panels and usable electricity. Both off-grid and on-grid electrical solar systems require an inverter to transform DC electricity collected from sunlight into 120 volt or 240 volt AC electricity for use to power household lights, appliances, and other things. Also, on-grid inverters synchronize the electricity produced from the solar panel system to the utility company’s AC grade. This makes it possible for the excess of surplus electricity to be fed into the power company’s utility grid.
On-grid solar collector systems don’t have to have, but usually include, a battery bank for backup. Special inverters with a battery charger are available allowing the batteries to be charged from the grid and allow for them to be charged by a gas powered generator.
On-grid inverters are weather proofed so they can be installed outside near other electrical equipment, whereas off-grid inverters are usually not weather proofed and are made to be used very near the indoor electrical fuse or breaker box.