Can you cut the adapter off a lighter adapter plug and just wire it to the battery I want to do this for neons

Answer 1

Yes, you can. You need to be sure you know which wire is positive and which is negative in the adapter's cable. The negative wire will be connected to the outside shield in the socket, and the positive wire will be connected to the center contact. If you do connect it directly to the battery, make sure you put a fuse on the wire within a few inches of the positive battery terminal.

I do the same thing very often to power satellite radios and GPS units without using the vehicle's cigarette lighter, although I normally connect it to some power source under the dash instead of connecting it directly to the battery.

Answer 2

yes you can. you'll need a switch wired in-line tho or they'll be on all the time. just gotta figure which is the + and which is the - and put the switch in line with the +. ground the neon to the chassis of the car tho, not the battery.

...ignore the guy above me. do what you want.