Why does a 12V solar panel produce 18V?

A 12V solar panel has an operating voltage of 18V because, in most cases, the voltage produced by the panel needs to be higher than the voltage required to charge a battery. The voltage required to charge a lead-acid battery is typically around 14.4V. A solar panel producing only 12V would not be able to generate enough voltage to charge the battery.

The solar charge controller is responsible for regulating the voltage and current from the solar panel to the battery to ensure that the battery is charged correctly. The controller needs to have enough voltage headroom to provide the battery with a voltage high enough to charge it. This is why the operating voltage of the solar panel is typically higher than the voltage required to charge the battery.

The operating voltage of a 12V solar panel is usually around 18V, which provides the solar charge controller with enough voltage headroom to regulate the voltage and current from the panel to the battery. This helps to ensure that the battery is charged correctly and avoids overcharging, which can cause damage to the battery.