usually you plug in lightstrips to the standard 12 volt
#Infiniti G37x Interior lighting
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wary harness
Quite honestly, Walmart (if you live in America) sells a kit that I know comes with intructions in the kit,, I personally haven't used it but from what I've heard its quite reliable... but additionally if you're looking for something more cost efficent go with amazon brands, and youtube the whole install. But ultimately you would be plugging them into the 12v (as above stated) or into the actual battery terminal itself (how I wired my underglow)
rustic tartan
Be careful using the battery as a direct power source as you can easily drain it on accident if you don't connect to a switch
Connecting to an Accessory power line will prevent that as it will only draw power when the car is on
You could tap into the same line as your interior 12v if you don't want to or can't just plug the kit in.
Looks cleaner, more work