Evergreen Panels listed as 18V not 24V Why?

because these modules are not really 24 volts nominal

compare the VOC, VMP, and cell count to that of a 24v nominal module, and the difference is apparent.

james
Alt-E staff

This is from the Learn section of our site:

http://howto.altenergystore.com/Getting-Started-with-Renewable-Energy/Introduction-to-Solar-Electricity/a89/p4/

"PV modules have three different voltage ratings that it’s handy to understand. The Nominal voltage of a panel could also be called the “conversational voltage.” When we talk about the voltage of the panels and the other components of the system, we’ll most often use the nominal voltage. Nominal voltage actually refers to the voltage of the battery that the module is best suited to charge; this is a leftover term from the days when solar panels were used only to charge batteries. The actual voltage output of the panel changes as lighting and temperature conditions change, so there’s never one specific voltage at which the panel operates. Nominal voltage allows us, at a glance, to make sure the panel is compatible with a given system. The second voltage rating is the maximum power voltage (Vmp). This is the highest voltage the panel can produce while connected to a system and operating at peak efficiency. The third voltage is open circuit voltage (Voc). This is the maximum voltage that the panel can produce when not connected to an electrical circuit or system. Voc can be measured with a meter directly contacting the panel’s terminals or the ends of its built-in cables."

The Morningstar SunSaver MPPT specs are saying that the max Voc it can handle as an input is 75v and the max nominal PV input is 36v. So long as your charging a 24v battery bank you can connect two Evergreen ES panels wired in series into the controller.

When I'm doing voltage drop calculations I use Vmp for voltage.