A solar controller is installed to regulate the voltage output of your solar panel array. For marine applications, we recommend an efficient MPPT controller over the less expensive and less efficient PWM controller. A good MPPT controller will charge your batteries faster and protect your batteries from over-charging.
Make sure you select a solar controller that is sized for the solar array voltage and amps. Also, choose a controller that is tailored to your battery chemistry and voltage (e.g. 12 or 24 VDC).