Here's some info on Building a Solar Power, MPPT Solar Controller. Using an Arduino. Check out the Videos and links below...

Don

ARDUINO MPPT SOLAR CHARGE CONTROLLER (Version-3.0) by deba168

"This instructable will cover a project build for a Arduino based Solar MPPT charge controller.It has features like: LCD display,Led Indication,Wi Fi data logging and provision for charging different USB devices.It is equipped with various protections to protect the circuitry from abnormal condition.

The microcontroller used is in this controller is Arduino Nano. This design is suitable for a 50W solar panel to charge a commonly used 12V lead acid battery. You can also use other Arduino board like Pro Mini,Micro and UNO.

Now a days the most advance solar charge controller available in the market is Maximum Power Point Tracking (MPPT).The MPPT controller is more sophisticated and more expensive.It has several advantages over the earlier charge controller.It is 30 to 40 % more efficient at low temperature.But making a MPPT charge controller is little bit complex in compare to PWM charge controller.It require some basic knowledge of power electronics."

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http://www.instructables.com/id/ARDUINO-SOLAR-CHARGE-CONTROLLER-Version-30/?ALLSTEPS