Applications
98 900-0009-01-00 Rev C
Array Design
Sizing Guidelines
Below is a list of maximum array wattages for the FLEXmax for various nominal voltage batteries. This
should be used for sizing an array. Note that every PV module is different. The specifications for every
model should be consulted before designing or assembling a PV array.
Table 5 Maximum PV Input Wattage per Charge Controller
1
Nominal
Battery
Voltage
Maximum Array Size
(in watts, Standard Test Conditions)
FLEXmax 80 FLEXmax 60
12 V 1000 W 800 W
24 V 2000 W 1600 W
36 V 3000 W 2400 W
48 V 4000 W 3200 W
60 V 5000 W 4000 W
Open Circuit Voltage
(Voc)
Open-circuit voltage (Voc) is the unloaded voltage generated by the PV array. The FLEXmax controller
can withstand Voc of up to150 Vdc. However, if the Voc exceeds 145 Vdc, the FLEXmax will suspend
operation to protect the system components.
CAUTION: Equipment Damage
Although the FLEXmax shuts down when voltage is greater than 145 Vdc, this will not
prevent the array from generating voltage. Anything higher than 150 Vdc will damage
the FLEXmax, whether it has shut down or not. The array should be designed so that
voltage never exceeds 145 Vdc in order to prevent equipment damage.
Weather Conditions
Cooler climates can cause the Voc to rise above the array’s rated Voc. In climates that observe
temperatures less than approximately -15°C (5°F), a Voc greater than 125 Vdc is not recommended.
Hot weather: lower Voc and lower Vmp
Cold weather: higher Voc and higher Vmp
If the specific voltage temperature correction factor is not known for a particular module, allow for ambient
temperature correction using the following information:
25° to 10°C (77° to 50°F) multiply Voc by 1.06
9° to 0°C (49° to 32°F) multiply Voc by 1.10
-1° to -10°C (31° to 14°F) multiply Voc by 1.13
-11° to -20°C (13° to -4°F) multiply Voc by 1.17
-21° to -40°C (-5° to -40°F) multiply Voc by 1.25
1
Based on the most common solar arrays under Standard Test Conditions (1000 watts per square meter to solar
panel at 25°C [77°F] ).
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