Thread: 12VDC to 12VDC require an adapter

My project is new and though I'm handy with a screwdriver, knife and electrical tape I don't know much about electricity. Please don't laugh at this stupid question...I would appreciate some help.

I am just starting on my first mp3car project, an HP Omnibook 800 mini-laptop acquired on ebay for $205. Eventually I'm going to mount it in my micro-trunk but for now it lives on the passenger seat to enjoy and test. The AC power adaptor that came with the Omnibook delivers 12V at 3.3 amps.

I went to Radio Shack to get a cigarette lighter adapter that would power the Omnibook directly. They sold me ($59.95) a "Universal Notebook Computer DC Power Adapter" that works like a charm. It runs on 11-16V. You can program the voltage delivery with a selector switch from 9 to 24V DC, it claims a maximum power output of 4 amps. They insisted that this was the only thing they had that would work.

Question 1: Why do I need this thing at all? Why not just run from the cigarette lighter to the DC IN on the laptop? It is 12v to 12v, right?

Question 2: If an adapter/power supply is necessary is $59.95 too much to pay? I have 30 days to return the Radio Shack unit if so. Is there a better/less expensive approach.

Eventually I'm going to mount the lappy in the micro-trunk. There is another 12v cigarette plug back there and a CD changer plug. The car also has two 12v outlets up front. I'm using the mini-laptop as a PDA/on-the-road email checker, etc. so at times it will be convenient/necessary to have it up front.

Thanks in advance for the help on the DC power adapter questions.