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.

MPPT controllers do not connect the solar panel to the battery directly. By DC/DC conversion, they have the ability to track the highest voltage available at any given moment. They will adjust the amount of power being delivered as conditions change throughout the day.

Solar Panel Basics

All solar panels are rated in watts and the wattage relates to the power of a panel. To determine watts, multiply the voltage (Vmp) by the current or amps (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. It will always produce current relative to the sunlight striking it. The voltage may vary but the current remains relatively the same. Our example 130 watt panel will produce 7.4 amps in full sun but the voltage can change widely.

Why MPPT Is Important

Most 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 the solar panel voltage lower.

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 90 watts of power out of your 130 watt panel. The power is available at the panel but the controller can not capture it. As the battery voltage climbs, so will the power. If your controller is set to regulate at 14 volts, the most you can ever capture from the panel is 104 watts.

MPPT controllers are not limited by the battery voltage. They always attempt to track the Vmp of a solar panel. There is a slight loss in the conversion process but the added power will more than make up this loss.

The higher the Vmp, 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.