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4.0
Operation
The TriStar MPPT 150V operation is fully automatic. After installation is completed, there are few
operator tasks to perform. However, the operator should be familiar with the operation and care of
the TriStar MPPT 150V as described in this section.
4.1 TrakStar
MPPT Technology
TM
The TriStar MPPT 150V utilizes Morningstar's TrakStar
technology to extract maximum power from the solar array. The tracking algorithm is fully automatic
and does not require user adjustment. TrakStar
point as it varies with weather conditions, ensuring that maximum power is harvested from the array
throughout the course of the day.
Current Boost
Under most conditions, TrakStar
MPPT technology will "boost" the solar charge current. For exam-
TM
ple, a system may have 36 Amps of solar current flowing into the TS-MPPT and 44 Amps of charge
current flowing out to the battery. The TriStar MPPT 150V does not create current! Rest assured that
the power into the TriStar MPPT 150V is the same as the power out of the TriStar MPPT 150V. Since
power is the product of voltage and current (Volts x Amps), the following is true
(1) Power Into the TriStar MPPT 150V = Power Out of the TriStar MPPT 150V
(2) Volts In x Amps In = Volts Out x Amps Out
assuming 100% efficiency. Losses in wiring and conversion exist.
1
If the solar module's maximum power voltage (V
the battery current must be proportionally greater than the solar input current so that input and output
power are balanced. The greater the difference between the V
current boost. Current boost can be substantial in systems where the solar array is of a higher nomi-
nal voltage than the battery as described in the next section.
High Voltage Strings and Grid-Tie Modules
Another benefit of TrakStar
MPPT technology is the ability to charge batteries with solar arrays of
TM
higher nominal voltages. For example, a 12 volt battery bank may be charged with a 12, 24, 36, or
48 volt nominal off-grid solar array. Grid-tie solar modules may also be used as long as the solar ar-
ray open circuit voltage (V
) rating will not exceed the TriStar MPPT 150V 150 Volt maximum input
oc
voltage rating at worst-case (coldest) module temperature. The solar module documentation should
provide V
vs. temperature data.
oc
Higher solar input voltage results in lower solar input current for a given input power. High voltage
solar input strings allow for smaller gauge solar wiring. This is especially helpful and economical for
systems with long wiring runs between the controller and the solar array.
34
Maximum Power Point Tracking (MPPT)
TM
technology tracks the array maximum power
TM
:
1
) is greater than the battery voltage, it follows that
mp
and battery voltage, the greater the
mp
Operation
An Advantage Over Traditional Controllers
Traditional controllers connect the solar module directly to the battery when recharging. This
quires that the solar module operate in a voltage range that is usually below the module's V
12 Volt system for example, the battery voltage may range from 10 - 15 Vdc, but the module's V
typically around 16 or 17 Volts. Figure 4-1 shows typical current vs. voltage and power output curves
for a nominal 12 Volt off-grid module.
12 Volt Module
Current vs. Voltage
Typical Battery
Maximum
Voltage Range
Power
Point
VOLTAGE
10
15 17
Figure 4-1. Nominal 12 Volt Solar Module I-V curve and output power graph.
The array V
is the voltage where the product of output current and voltage (Amps x Volts) is great-
mp
est, which falls on the "knee" of the solar module I-V curve as shown on the left in Figure 4-1.
Because traditional controllers do not always operate at the V
that could otherwise be used to charge the battery and power system loads. The greater the dif-
ference between battery voltage and the V
MPPT technology will always operate at the maximum power point resulting in less wasted energy
compared to traditional controllers.
Conditions That Limit the Effectiveness of MPPT
The V
of a solar module decreases as the temperature of the module increases. In very hot weath-
mp
er, the V
may be close or even less than battery voltage. In this situation, there will be very little or
mp
no MPPT gain compared to traditional controllers. However, systems with modules of higher nominal
voltage than the battery bank will always have an array V
the savings in wiring due to reduced solar current make MPPT worthwhile even in hot climates.
TriStar MPPT Operator's Manual
12 Volt Module
Output Power
TrackStar
Maximum
Traditional
Controller
Operating Range
VOLTAGE
10
15 17
of the solar array, energy is wasted
mp
of the module, the more energy is wasted. TrakStar
mp
greater than battery voltage. Additionally,
mp
re-
. In a
mp
is
mp
Power
Point
TM
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