Figure 6 - Solar Panel Cutaway
Photocells (photovoltaic or “PV”) can be thought of as a direct current (DC) generator or charger powered by the sun.
When light photons of sufficient energy strike a solar cell, they knock electrons free in the silicon crystal structure forcing them through an external circuit (battery or direct DC load), and then returning them to the other side of the solar cell to start the process all over again. The voltage output from a single crystalline solar cell is about ½ Volt with an amp output that is directly proportional to the cell's surface area (approximately 7 amps for a 6 inch square multi-crystalline solar cell). In typical solar module there will be 30 to 36 cells connected in series. This produces a solar module with a 12V nominal output (17V peak output) that can then be wired in series and/or parallel with other solar modules to form a complete solar array capable of charging a 12, 24 or 48 volt battery bank.