What is the Array Voltage?

easytim

I have a 12vdc solar panel with the max power voltage of 19.8 volts and an open circuit voltage of 24.10 volts

What is the Array voltage? I don't know what the term Array Voltage means

BB.

Re: What is the Array Voltage?

Solar array--a collection of cells (in one panel) and/or a collection of solar panels into a voltage/current producing "array" of solar cells/panels. Typically laid out in rows and columns (like "array" in math or computer science).

The voltage would how the array is setup (series, parallel, series/parallel) to provide optimum voltage and current to the load (can be a battery bank behind a charge controller, or it could be a Grid Tied inverter to take panel power and convert it for use by a home and others on the Grid).

The array voltage can get a bit complex... First a solar cell outputs current and voltage. The "IV" curve is dependent on the light hitting the cell(s) and the load.

The typical values that we worry about are Vmp (Voltage, maximum power) and Imp (Current Maximum Power). These are the voltage and current where the cell outputs the most power (Pmp=Imp*Vmp).

Placing panels in parallel, the currents add, and the voltage remains the same.

Placing panels in series, the voltage adds and the current remains the same.

Voc (Voltage open circuit)... The maximum voltage the solar cell/array will achieve with Zero current load (such as when a charge controller has fully charged a battery bank and there is no more current required).

Here is a nice data sheet with graphs of of the voltage vs current vs power vs light levels vs temperature:

data sheet for a crystalline silicon panel
...
Solar panel voltage and current needs to be matched to your loads...

For example, a simple solar charge controller (on/off or PWM).. The panel voltage (Vmp) should be equal to:

Vmp solar array = Vbatt max + Vcontroller drop + V wiring drop=15 volts + 2v + 0v = 17V Vmp

Roughly for a lead acid battery (requires 15 volt equalization voltage) + the 2 volt controller drop) would be 17 volts or more... Less voltage at the panel, and the current to the battery will start to fall (panel has to have a higher voltage than the load for the current to flow).

If the Vmp of the panel is too high--it is a waste of power with a simple PWM charge controller...

Say we have two 34 watt panels. Once is 34 watts at Vmp=17v and 2 amps. The other is 34 watts at Vmp=34 volts and 1 amp:

Into a 12 volt battery, the "12 volt panel" (really Vmp=17 volts), Power into the battery will be:

Pbatt=15 volts * 2 amps = 30 watts into a 12 volt battery.

For the "24 volt panel" (Vmp=34 volts):

Pbatt=15 volts * 1 amp = 15 watts into a 12 volt battery.

Now, take that "24 volt panel" and connect it to a 24 volt battery bank:

Pbatt=30 volts * 1 amp = 30 watts into a 24 volt battery bank.

And the "12 volt" panel will never drive any current into a 24 volt bank...

Is this sort of what you where looking for? I am not sure you were looking for an "English" definition or an "Engineering" definition to your question... So, I went overboard and tried both.

-Bill

easytim

Re: What is the Array Voltage?

Sorry BB I did not make myself clear, the water is still muddy right now.

I'm trying to clear it up in another post:)

Thanks so much for your input