If you are planning to install solar panels on your conversion you will need to have a solar charge controller. The controller manages the power coming from the solar panels to the deep cycle batteries. It ensures the batteries are not overcharged during the day and does not let the power run back towards the solar panels draining the batteries at night. The primary job is to manage the power and the load coming from the panels.
Solar charger controllers come in two different technologies. PWM and MPPT. MPPT charge controllers are more expensive than a PWM but with good reason. It is better to pay the extra money and get MPPT.