4.0 OPERATION
MORNINGSTAR CORPORATION
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The array V
mp
is the voltage where the product of current
and voltage (Amps x Volts) is greatest, which falls on the
“knee” of the solar module I-V curve as shown in Figure 8.
Because Traditional controllers do no operate at the V
mp
of the solar array, energy is wasted that could otherwise be
used to charge the battery and power system loads. The
greater the difference between battery voltage and the Vmp
of the module, the more energy is wasted.
TrakStar MPPT technology will always operate at the
V
mp
resulting in less wasted energy compared to traditional
controllers.
4.3 Battery Charging Information
The SunSaver MPPT has a 4-stage battery charging
algorithm for rapid, ef
cient, and safe battery charging.
Figure 9 shows the sequence of the stages.
NIGHT
NIGHT
BULK
CHARGE
ABSORPTION
FLOAT
EQUALIZE
VOL
TAGE
TIME
Figure 9. SunSaver MPPT charging algorithm
Bulk Charge
In this stage, the battery voltage has not yet reached
absorption voltage and 100% of available solar power is
used to recharge the battery.
Absorption
When the battery has recharged to the Absorption voltage
setpoint, constant-voltage regulation is used to prevent
heating and excessive battery gassing.
Float
After the battery is fully charged the SS-MPPT reduces
the battery voltage to a
oat charge which is sometimes
called a
trickle charge.
Depending on battery history, the battery remains in the
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