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27. Typical Array Sizing Guide
Below is a list of recommended array sizing for the FLEXmax 80 for various nominal voltage batteries:
Nominal Battery Voltage Recommended Array Size
(in watts, Standard Test Conditions)
12V 1250W
24V 2500W
36V 3750W
48V 5000W
60V 6250W
The FLEXmax 80 PV MPPT Charge Controller is capable of an input open circuit voltage (VOC) of up
to 150 VDC. Cooler climates can cause the VOC to rise above the panel VOC rating. In climates that
observe temperatures less than approximately 5° F, a VOC greater than 125 VDC is not recommended.
When sizing an array, it is recommended that the nominal array voltage be higher than the nominal
battery voltage. Below is a list of recommended nominal array sizing:
Nominal Battery Voltage Nominal Array Voltage (recommended)
12V 24V (or higher)*
24V 36V (or higher)*
36V 48V (or higher)*
48V 60 V (or higher)*
60V 60V (low temp is less than 5°F) or
72V (low temp is greater than 5°F)
* When sizing an array to charge controller with a distance of 70 feet or greater, OutBack recommends
the nominal array voltage be slightly higher than the recommended nominal array voltage. Example:
A 36VDC nominal array recharging a 12V nominal battery with an array to charge controller distance
of about 70 feet or greater. Sizing the nominal array voltage higher than the nominal battery voltage
ensures that the Maximum Power Point is always above the battery voltage. The Maximum Power
Point will decrease as the panels warm up, thus lowering the output of the array. The FLEXmax 80
Charge Controller will not be able to boost the output if the Maximum Power Point of the array is at or
lower than the battery voltage.