Epsolar eTracer ET4415BND, Operation Manual

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14
V
mp
. In a 12V system for example, the battery voltage may range from 11 to 15Vdc but
the module‘s V
mp
is typically around 16 or 17V.
Figure 4-1 shows a typical current VS. Voltage output curve for a nominal 12V off-grid
module.
The array V
mp
is the voltage where the product of current and voltage (Amps×Volts) is
greatest, which falls on the ‗knee‘ of the solar module I-V curve as shown in Figure4-1.
Because Traditional controllers do not operate at the V
mp
of the solar modules(s),
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 V
mp
of the module, the
more energy is wasted.
eTracer-BND MPPT technology will always operate at the V
mp
resulting in less wasted
energy compared to traditional controllers.
· Conditions That Limits the Effectiveness of MPPT
The V
mp
of a solar module decreases as the temperature of the module increases. In very
hot weather, the V
mp
may be close or even less than battery voltage. In this situation,
there will be very little or no MPPT gain compared to traditional controllers. However,
systems with modules of higher nominal voltage than the battery bank will always have
Current vs Voltage in 12V system Output power in 12V system
Figure 4-1 Nominal 12V solar module I-V curve and output power graph