The US Automatic gate opener charge controller accepts inputs from either the supplied AC transformer or the optional solar panel. The transformer and solar panel come with a DC plug for easy installation. Once the charge device is selected and installed connect the DC plug into the charge controller "power in" located in the upper right corner of the charge controller. When using a solar panel, the charge controller is designed to only charge the battery when there is enough sun to do so. If there is no sun, the lights on the charge controller should be "off". this feature reduces the drain on the battery in solar installations. If transformer is installed lights are operational all the time.