DIY Manual

47 | P a g e 10-543-1 REV A

DIY Manual

This reads as follows … With constant power, if voltage rises, current drops. In this case, power

is zero since current is zero: XVoc x 0A = 0W.

Isc – Short Circuit Current: With a PV module NOT exposed to sunshine and the positive and

negative wires connected to each other, with an ammeter you can measure Isc. When Isc is

maximum, the voltage is zero, due to zero resistance in the circuit. This is shown by the power

formula: P = V x I.

Similarly, power will be zero because voltage is now zero: 0Voc x XIsc = 0W

Vmp – Maximum Power Voltage: This is the highest voltage on the IV Curve; that is, with current

now flowing from the PV module, this will be the highest point of voltage.

Imp – Maximum Power Current: This is the current flow from the PV module at the Vmp point

on the IV curve. In operation – when the Classic sweeps the IV curve and decides to lock on to a

particular Vmp, then Imp is the current at this particular point of Vmp.

So, what does all this Vmp and Voc stuff mean?!

With your Classic powered on, go to the 3

Status page; you will see “Voc” in the lower left-hand

corner of the MNGP screen. Voc is the voltage from the PV array as per how you wired the panels

in series strings. In the upper left, you will see “IN.” IN is the array’s Vmp, which will constantly

change as the Classic constantly sweeps the IV Curve. The Voc voltage needs to be at least 133%

higher than the battery voltage at that moment in time for the Classic to work, otherwise the

Classic goes to a resting mode. Troubleshooting – If your Classic goes to resting, check the Voc

and the Vmp (“IN”). If Voc is zero, then you either have a disconnected wire from the PV array,

reverse PV polarity at the Classic’s terminal block, or a bad Classic. If Voc is less than 133% of the

battery voltage, then the Classic will not make power. Cloudy conditions will cause this to

happen, or low light conditions (i.e., early morning or late at night).

Classic Maximum Current Output

Each Classic model outputs a different amount of current based on the battery bank voltage.

CLASSIC

12V Battery Bank

24V Battery Bank

48V Battery Bank

Classic 150

96A

94A

86A

Classic 200

79A

78A

Classic 250

61A

62A

55A

P = V x I