Most kits come with the LED tubes/strips which would go to a control box. The control box would then be connected to a 12V power Source. If you have a system more than 12V, you would need a voltage reducer. Most applications can be installed directly to the battery, however additional power adapters may be preferred such as a cigarette lighter power adapter, or expandable circuits.
Some kits do not have a control box, but still, has the essential wires or plugs for the kit to be up and running. Some minor electrical accessories may be needed depending on how you would like to install (such as wire connectors, or eyelets).