What Is MPPT

MPPT stands for Maximum Power Point Tracking. This is a simple explanation on how MPPT works and why Starlight Solar recommends using this type of controller. Simply put, MPPT is an electronic method of extracting the most power from your solar panels. The "tracking" has nothing to do with mechanically moving the panels to track the sun.

Solar Panel Basics

All solar panels are rated in watts or the power a solar panel can produce under specific conditions. To determine watts, multiply the voltage (Vmp) by the current (Imp). The Voc and Isc refer to other measurements and are not used in calculating power.

 

Here is an example: Our Kyocera 130 watt solar panel is rated at 7.4 amps at 17.6 volts. By multiplying the amperage by the voltage you get the rated wattage.
 

Here's the math: 17.6 Vmp X 7.4 Imp = 130 watts.

 

A solar panel is a constant current device. The voltage may vary but the current remains relatively the same for a given amount of sunlight. Our example 130 watt panel will produce 7.4 amps in full sun but the voltage can change widely.

Why MPPT Is Important

Non-MPPT charge controllers will connect your solar panel directly to your batteries. This will limit the power captured from the panel. The battery acts as a load and will pull down the solar panel voltage lower. MPPT controllers do not connect the solar panel to the battery directly. If your panel voltage is lower, then your power will be lower as well.


Here is an example: If your battery is at 12.2 volts it will pull down the Vmp voltage of the panel to just slightly more than the battery voltage. Because the power delivered from your charge controller is the result of voltage time’s amperage, you will get less power delivered to your battery.

Here's the math: 12.2 X 7.4 = 90 watts.

You will only get about 90 watts of power out of your 130 watt panel. Here is the important part: The power is STILL available at the panel but the controller can not capture it. As the battery voltage climbs, so will the power. If your charge controller is set to regulate at 14 volts, the most you can ever capture from the 130 watt panel is 104 watts! In order to capture the full 130 watts, you must convert all the voltage into current. ONLY MPPT controllers can do this.

 

The higher a panels operating voltage (Vmp) is the more current you will gain by using MPPT. All types of solar installations will benefit by using MPPT technology. RV’s have very limited space for solar panels. Most RV and motorhome systems have the panels mounted flat on the roof. Considerable power is lost in the winter months due to the low angle of the sun. Because of these limitations, it is very important to transfer all the power you can by using MPPT technology.

 

Copyright 2007, Starlight Solar