PWM vs. TrakStar MPPT Technology

Traditional PWM vs Morningstar’s TrakStar™ MPPT Technology
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The Vmp (maximum power voltage) is the voltage where the
product of the output current and output voltage (amps * volts) is
greatest and output power (watts = amps * volts) is maximized.
Module wattage ratings (e.g. 100W, 205W) are based on Pmp
(maximum power) at Vmp under standard test conditions (STC).
Using a nominal 12V system as an example, the battery voltage will
normally be somewhere between 10 – 15 VDC. However, 12V
nominal solar modules commonly have a Vmp(STC) of about 17V.
When the array (having Vmp of 17V) is connected to the batteries
for charging, the batteries pull down the output voltage of the
array. Thus, the array is not operating at its most efficient voltage of
17V, but rather at somewhere between 10 and 15V. The following
graphs illustrate this phenomenon:
Because these traditional controllers rarely operate at the Vmp of the solar array, potential energy is
being wasted that could otherwise be used to better charge the battery bank and maintain power for
system loads. The greater the difference between battery voltage and the Vmp of the array, the more
energy is wasted by a PWM controller during bulk charging.
The greater the
difference between
battery voltage and the
Vmp of the array, the
more energy is wasted
by a PWM controller
during bulk charging.