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post #1 of Old 11-25-2012 Thread Starter
Maine Sail
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MPPT vs. Shunting Solar Controller

I get asked quite a bit to describe the difference between an MPPT (multi-point power tracking) solar controller and non MPPT controllers.

Basically all 12V nominal solar panels run voltages of 16 - 18V+. With a PWM or shunting controller the excess voltage goes to waste when the panel voltage is stepped down to a safe charging voltage. An MPPT controller can convert this excess voltage to current so there is less waste and more efficient charging..

To show how this works I decided to use my bench top power supply to simulate a solar panel yet provide consistency in output for an A/B scenario. I set the power supply at 17.4V and 4A or the rough equivalent to a 70W solar panel. I then fed the power supply through a switch to choose which solar controller got the power. I used a battery bank that had been depleted to "bulk" for the 4-5A of current it would see.

The video below shows the results. Basically the MPPT controller had an output of roughly 22% - 24% more than the simple shunting controller. There is no magic just an A/B switch and two different solar controllers...

Hope this helps give some clarity...

-Maine Sail / CS-36T

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