Increase Output and Efficiency with a Maximum Power Point Tracking Solar Charge Controller

Maximum Power Point Tracker – MPPT – Solar Panel Charge Controller

To understand a maximum power point tracker (MPPT), we need to understand how a photovoltaic system produces and stores power. In battery based solar panel systems, the output power that is generated is used to charge the system’s storage batteries. These batteries are rated at 12 volts. Because of the variability in the output from the solar panels, there needs to be a device in between the solar panel and the battery that will safely limit the voltage to the battery. That’s where a standard solar panel charge controller comes in. Its job is to regulate the voltage that the battery receives from the solar panel. It effectively limits the output of the solar panel to a value of about 12 volts.

On the plus side, these charge controllers are relatively simple and cheap. But, they have one very undesirable characteristic. The problem stems from that fact that these charge controller don’t allow solar panels to operate at their maximum power output levels. You won’t be getting all the power that you can from your solar panels due to the fact that solar panels usually have voltage output ratings higher than 12 volts. As an example, let’s look at the specs for a 110 watt Mitsubishi series panel.

Vmp – Voltage @ maximum power = 17.1 V
Imp – Current @ maximum power = 6.43 A

The power rating for this particular panel is 110 watts.
From ohms law, Power = Voltage x Current (110 watts = 17.1 x 6.43)

Now if you use a typical charge controller that limits the voltage to 12 volts, you can see that the available power output from the panel has been reduced. Again, using ohm’s law P=VI

Power = 12 volts x 6.43 amps = 77.6 watts
A reduction in power of 110 watts – 77.6 = 32.84 watts
As a percentage loss, that’s equal to (32.84/110) x 100 = 29.85%

As you can see, by using a normal charge controller it’s possible to lose up to 30% of the power that you could potentially be generating. One thing to note is that this is the maximum theoretical amount, and that the real value will be lower than that. But the point remains: You give up a very significant portion of power that you could be generating when you use a standard charge controller.

The good news is that there is a device that eliminates this problem, and it’s called a Maximum Power Point Tracker charge controller, or MPPT for short. What it is, is an active control system that tightly regulates the power output of the panels and allows them to operate at maximum output while charging batteries that are at a less than optimal operating voltage. Using a combination of electronic circuits, these charge controllers force the panels to operate at their maximum output all the time. The MPPT controller then conditions this power, matching it to the needs of the batteries that the panels are charging. The end result is a huge increase in efficiency and power output that would normally be lost to a typical solar panel charge controller. As you may have guessed, one of these MPPT controllers can pay for itself in a very short period of time.

Taking into account the increased output, efficiency, and very quick payback period, installing a maximum power point tracking charge controller is one of the best investments you can make in your solar power system.