Charge controllers are an essential part of a battery based solar system. These are very easy to hook up, simply connect + and - from the solar panel into the controller, and + and - from the controller to the battery terminals (of course, fuse everything). Point it at the sun and instant power! The job of the charge controller is to sense the batteries state of charge and turn off the power when the batteries are full, to prevent over-charging. A must have for any system over 10 watts.
There are 2 types of charge controllers, Maximum Power Point Tracking (MPPT) and Pulse Width Modulated (PWM). MPPT is the newer and better technology, it yields from 20% to 35% more power with low voltage panels, and is necessary when we move up to the higher voltage panels because it transforms the voltage down (while raising the Amperage) to charge a 12, 24, or 48 Volt battery bank. The most significant thing a MPPT controller does is to allow us to use bigger, better, less expensive, higher voltage, industrial panels.
PWM controllers are less expensive and work great with smaller, low voltage panels.