Hobbies And Interests
Rated Output vs. Actual Output
Standard panels connect 36 cells that produce 0.5 to 0.6 volts each. Therefore, a solar panel with 36 cells rated at 12 volts will actually produce around 16 to 21 volts. The printed 12-volt rating of a panel denotes that the output of the panel is sufficient to power a 12-volt rechargeable battery. This rating accounts for fluctuations in panel performance and the fact that a 12-volt battery requires more than 12 volts to charge.
Output Limits
The efficiency of a solar panel is determined by available sunlight. If panels are shaded by direct contact or by objects in the path of sunlight, the solar array will generate reduced power. The angle of incidence of sunlight also affects solar panel output. Output is highest when the angle of incidence is close to perpendicular. Therefore, the panel output will fluctuate based on the sun's path across the sky. In turn, this can affect the rate at which a battery charges.
Battery Ratings
In order to charge a battery with a 12-volt solar panel, that battery cannot have a voltage rating much higher than 12 volts. For example, you cannot charge a 24-volt battery with a 12-volt solar panel. In the worst-case scenario, this could result in damage to either the charger or the battery. If your battery is rated at 12 volts, you can charge it with your 12-volt solar panel. However, even with a matched pairing, the fluctuations in voltage from your solar panel could be harmful to your battery. For this purpose, you should use a charge controller between your panel and battery.
Charge Controllers
Charge controllers regulate the voltage from a solar panel, and send only a very specific voltage and current to your battery. In this way, you can charge a battery in the most efficient manner possible. If you send too much voltage to a battery, or if the voltage fluctuates too much, the battery could get damaged. For a 12-volt battery, if the voltage exceeds 14.5 volts for prolonged periods of time, the battery can be damaged by overcharging.
Current
Current is the flow of charge over a unit of time. One ampere, the standard unit of current, represents a flow of one coulomb of charge per second. Electricity flows from a solar panel at a specific current. The current flowing to a battery affects the rate at which a battery charges. Therefore, not only must you balance the voltage between the panel and battery, but you must also make sure the battery is receiving an appropriate current. This ensures that the battery does not charge too quickly. A charge controller will regulate the current going to your battery. In general, you should charge your battery with a current equal to 10 percent of the battery's rated ampere-hour output. For example, if a battery is rated 12 volts and 100 amp-hours, you should charge it with a current of 10 amps.