Powertech Solar Charge Controller with USB (12V/24V)Intelligent yet lightweight, this solar controller uses Pulse Width Modulation (PWM) to control battery charging. With total autonomy, its set and forget operation means you can get maximum charge into your batteries from your solar installation without having to worry about those things. It provides all the important safety features such as overload, short circuit, over discharge, and reverse polarity protection. A handy feature is also the USB port