TrakStar MPPT Technology and Maximum Input Power

Morningstar’s TrakStar™ MPPT Technology & Maximum Input Power
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Q2. Can I exceed the nominal wattage ratings of MPPT controllers? Will it void the
warranty?
You can size Morningstar’s MPPT controllers well above the Maximum Nominal Solar PV Input rating without
damaging the controller and without the charging current exceeding the maximum output current rating. The
controller can limit output current and will run at 100% of rated current output and not higher. The controller
was designed with this power-shaving capability and when oversized it does not void the warranty.
Q3. Is there a reason I would want to do that?
Yes, there are many benefits to doing this; they are outlined below. Please that note that doing this is partially an
economic decision; you can purchase more power than the controller can use and this will contribute to better
power availability and lessen the chance of a low voltage disconnect (LVD) & loss of load situation. You just have
to consider (at some point) the diminishing return that comes with more power-shaving.
Some of the benefits in exceeding the nominal wattage ratings of an MPPT controller include:
 Effect of maximum charging power limit of a Morningstar TrakStar MPPT controller on an oversized
array:
o Better production early and late in the day.
o Operates at maximum power rating getting full charging potential of MPPT controller more
often.
o Better production during low solar insolation periods (cloudy weather).
o Limits the maximum charging current.
 Viable reasons for using an array rated for a wattage greater than the controller maximum:
o Daily maximum power levels may typically be lower than STC rated power of the solar modules.
 Tilt, azimuth angle, time of day or year, weather, climate, dust, pollution and other
factors reduce output power of the array leaving some unused controller capacity.
o Energy harvesting during lower power production periods (cloudy weather) is often more
valued than during times when the array can operate at full power (sunny weather).
o Ability to use larger array sizes for more options to better match strings for the array.
o Using fewer, but high power, modules instead of several smaller ones is more cost effective.
o The availability and lower cost of 60 cell modules (Vmp~30V) from the Grid connected solar
market.
o More consistent levels of charging current (running controller at maximum levels more
consistently).