11
Figure 4-1
Nominal 12V Solar Module I-V curve and output power graph
The array Vmp 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 Figure 4-1. Because Traditional controllers do not operate at the Vmp 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 Vmp of the module, the more energy is wasted.
MPPT40CC MPPT technology will always operate at the Vmp resulting in less
wasted energy compared to traditional controllers.
Conditions that Limits the Effectiveness of MPPT
The Vmp of a solar module decreases as the temperature of the module
increases. In very hot weather, the Vmp 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 an array Vmp greater than battery voltage.
Additionally, the savings in wiring due to reduced solar current make MPPT
worthwhile even in hot climates.
Typical Battery
Voltage Range
Maximum
Power Point
Traditional
Controller
Operating
Range
Maximum
Power Point
Current vs. Voltage (12V System)
Output Power (12V System)
