SMP100 Manual
9
will produce a higher Voc and higher Vmp voltage. To determine the corrected Voc, consult
the data sheet for your solar panel and allow for the lowest possible temperature the solar
panel will be exposed to. If the data sheet is not available, use the table below to make the
calculation using the formula Voc Expected = Voc @ 25C * Correction Factor.
Temperature Correction Factor
25° to 10° C (77° to 50° F) 1.06
9° to 0° C (49° to 32° F) 1.10
-1° to -10° C (31° to 14° F) 1.13
-11° to -20° C (13° to -4° F) 1.17
-21° to -40° C (-5° to -40° F) 1.25
Wire Sizing
The distance between the PV array and the controller will be a factor in choosing an optimum
string voltage for the SolarMax. The higher the input voltage the smaller the wire can be
for any given amount of power. Be sure to consult your local electrical code specications
regarding wire sizing.
SolarMax is designed to deliver a maximum of 100 amps to the output. The wire size chosen
must be rated for this much current over the length of the run between SolarMax and the
batteries. The NEC requires that the output conductors have an amperage capacity of 1.25
X the rated current after all temperature and conduit ll corrections are calculated. For the
SolarMax this means conductors must be rated to carry 125 amps. The minimum cable
necessary to carry the full rated output of the SolarMax is #2 AWG, corrections for cable run
length, conduit ll and temperature could result in a larger wire size being necessary, to a
maximum of #1/0 AWG.
The maximum input current is a function of the array Short Circuit Current (Isc), assuming a
failure of SolarMax that creates a short circuit on the input. In this case, multiply the Isc rating
of one panel times the number of panels in PARALLEL to determine the maximum short circuit
current.
PV input circuits require a double correction factor for over current so PV Isc (short circuit
current) must be multiplied by 1.56. All PV input wires must be sized accordingly. This
apparent over sizing is done to reect the fact that solar modules can, and often do, produce
more than their rated power in conditions of heightened insolation and cold temperatures. Any
PV input disconnect or circuit breaker must also be rated at 1.56 of array Isc.