The voltage output of a single solar cell under Standard Test Conditions (STC) is approximately 0.5 volts. To increase the overall voltage, these cells are connected in series within a solar panel. Solar panels generate Direct Current (DC) power, whereas most household appliances operate on Alternating Current (AC) power.
These solar panel voltages include: Nominal Voltage. This is your typical voltage we put on solar panels; ranging from 12V, 20V, 24V, and 32V solar panels. Open Circuit Voltage (VOC). This is the maximum rated voltage under direct sunlight if the circuit is open (no current running through the wires).
Consider a scenario where you have a 200W solar panel with a working voltage of 20V and an amperage of 10A. To charge a 12V battery system, you’re going to need a charge controller to step down the voltage and regulate the current to prevent overcharging.
With solar panels, we can charge batteries, and batteries usually have 12V, 24V, or 48V input and output voltage. It is the job of the charge controller to produce a 12V DC current that charges the battery. Open circuit 20.88V voltage is the voltage that comes directly from the 36-cell solar panel.
Wattage, measured in watts (W), is the product of voltage and amperage (W = V x A). It represents the total power output of a solar panel. Understanding wattage is essential for determining how much energy a solar panel can produce and, consequently, how much power your devices or appliances can draw from it.
Max power voltage or voltage at maximum power is the voltage at which power output from the solar panel is greatest. This is the sweet point at which the solar panel is most efficient. It is higher than the nominal voltage. For example, this flexible 12V Renogy 100W solar panel has a Vmp or operating voltage of 18.9V.