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Solar Boost - MPPT PV Charge Controller
How would you like to get 10 to 30 percent
more energy out of your PV modules?
This maximum power point tracking (MPPT)
charge controller will do just that!
What Is Maximum Power Point Tracking?
A maximum power point tracker is similar to the transmission
in an automobile. They both couple a power source to a load more effectively
and efficiently. What a car's transmission does mechanically, MPPT
does electrically.
All PV modules have what is known as a maximum power point. The maximum
power point is where module voltage times output current equals maximum
power. A PV's maximum power point is constantly changing with module
temperature and solar insolation.
The MPPT controller tracks that
power point as it changes.
In most PVs, the maximum power point at 25°C is
at 16.5 VDC or higher, while a typical battery bank is in the 12 to
15 V range. This overhead voltage or "voltage
overkill" is built into PV modules by their manufacturers to
compensate for voltage loss when the modules are hot. Heating a module
can cause voltage depression of over 2.5 VDC just from a 25 to 50°C
temperature change. Batteries also change in voltage. A fully depleted
12 volt battery will have a voltage of about 12.5 VDC while under
charge. A fully recharged battery will be about 15 VDC while under
charge. (These figures assume a C/20 to C/10 rate of charge. Battery
temperature and age are also factors). Both voltages are well below
a PV's maximum power point.
The net effect is that PV modules spend most of their lifetime not
operating at their maximum power point. There is more power to be
had from the module, but we can't get at it because battery voltage,
and thereby system voltage, is different from the voltage at which
the PV module gives its maximum power. The MPPT solves this problem
by allowing the PV module, or PV array, to operate at its maximum
power point regardless of battery voltage or module temperature. This
little bit of electronic wizardry can enable a PV array to produce
between 10 and 30 percent more power than it does without the MPPT.
Day after day, this adds up to more energy for the system.
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